gcc/combine.c

   1 /* Optimize by combining instructions for GNU compiler.
   2    Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
   3    1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 2, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15 for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING.  If not, write to the Free
  19 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  20 02110-1301, USA.  */
  21
  22 /* This module is essentially the "combiner" phase of the U. of Arizona
  23    Portable Optimizer, but redone to work on our list-structured
  24    representation for RTL instead of their string representation.
  25
  26    The LOG_LINKS of each insn identify the most recent assignment
  27    to each REG used in the insn.  It is a list of previous insns,
  28    each of which contains a SET for a REG that is used in this insn
  29    and not used or set in between.  LOG_LINKs never cross basic blocks.
  30    They were set up by the preceding pass (lifetime analysis).
  31
  32    We try to combine each pair of insns joined by a logical link.
  33    We also try to combine triples of insns A, B and C when
  34    C has a link back to B and B has a link back to A.
  35
  36    LOG_LINKS does not have links for use of the CC0.  They don't
  37    need to, because the insn that sets the CC0 is always immediately
  38    before the insn that tests it.  So we always regard a branch
  39    insn as having a logical link to the preceding insn.  The same is true
  40    for an insn explicitly using CC0.
  41
  42    We check (with use_crosses_set_p) to avoid combining in such a way
  43    as to move a computation to a place where its value would be different.
  44
  45    Combination is done by mathematically substituting the previous
  46    insn(s) values for the regs they set into the expressions in
  47    the later insns that refer to these regs.  If the result is a valid insn
  48    for our target machine, according to the machine description,
  49    we install it, delete the earlier insns, and update the data flow
  50    information (LOG_LINKS and REG_NOTES) for what we did.
  51
  52    There are a few exceptions where the dataflow information created by
  53    flow.c aren't completely updated:
  54
  55    - reg_live_length is not updated
  56    - reg_n_refs is not adjusted in the rare case when a register is
  57      no longer required in a computation
  58    - there are extremely rare cases (see distribute_notes) when a
  59      REG_DEAD note is lost
  60    - a LOG_LINKS entry that refers to an insn with multiple SETs may be
  61      removed because there is no way to know which register it was
  62      linking
  63
  64    To simplify substitution, we combine only when the earlier insn(s)
  65    consist of only a single assignment.  To simplify updating afterward,
  66    we never combine when a subroutine call appears in the middle.
  67
  68    Since we do not represent assignments to CC0 explicitly except when that
  69    is all an insn does, there is no LOG_LINKS entry in an insn that uses
  70    the condition code for the insn that set the condition code.
  71    Fortunately, these two insns must be consecutive.
  72    Therefore, every JUMP_INSN is taken to have an implicit logical link
  73    to the preceding insn.  This is not quite right, since non-jumps can
  74    also use the condition code; but in practice such insns would not
  75    combine anyway.  */
  76
  77 #include "config.h"
  78 #include "system.h"
  79 #include "coretypes.h"
  80 #include "tm.h"
  81 #include "rtl.h"
  82 #include "tree.h"
  83 #include "tm_p.h"
  84 #include "flags.h"
  85 #include "regs.h"
  86 #include "hard-reg-set.h"
  87 #include "basic-block.h"
  88 #include "insn-config.h"
  89 #include "function.h"
  90 /* Include expr.h after insn-config.h so we get HAVE_conditional_move.  */
  91 #include "expr.h"
  92 #include "insn-attr.h"
  93 #include "recog.h"
  94 #include "real.h"
  95 #include "toplev.h"
  96 #include "target.h"
  97 #include "optabs.h"
  98 #include "insn-codes.h"
  99 #include "rtlhooks-def.h"
 100 /* Include output.h for dump_file.  */
 101 #include "output.h"
 102 #include "params.h"
 103 #include "timevar.h"
 104 #include "tree-pass.h"
 105
 106 /* Number of attempts to combine instructions in this function.  */
 107
 108 static int combine_attempts;
 109
 110 /* Number of attempts that got as far as substitution in this function.  */
 111
 112 static int combine_merges;
 113
 114 /* Number of instructions combined with added SETs in this function.  */
 115
 116 static int combine_extras;
 117
 118 /* Number of instructions combined in this function.  */
 119
 120 static int combine_successes;
 121
 122 /* Totals over entire compilation.  */
 123
 124 static int total_attempts, total_merges, total_extras, total_successes;
 125
 126 /* Sometimes combine tries to replace the right hand side of an insn
 127    with the value of a REG_EQUAL note.  This is the insn that has been
 128    so modified, or null if none.  */
 129
 130 static rtx replaced_rhs_insn;
 131
 132 /* When REPLACED_RHS_INSN is nonnull, this is a copy of the new right
 133    hand side.  */
 134
 135 static rtx replaced_rhs_value;
 136 \f
 137 /* Vector mapping INSN_UIDs to cuids.
 138    The cuids are like uids but increase monotonically always.
 139    Combine always uses cuids so that it can compare them.
 140    But actually renumbering the uids, which we used to do,
 141    proves to be a bad idea because it makes it hard to compare
 142    the dumps produced by earlier passes with those from later passes.  */
 143
 144 static int *uid_cuid;
 145 static int max_uid_cuid;
 146
 147 /* Get the cuid of an insn.  */
 148
 149 #define INSN_CUID(INSN) \
 150 (INSN_UID (INSN) > max_uid_cuid ? insn_cuid (INSN) : uid_cuid[INSN_UID (INSN)])
 151
 152 /* Maximum register number, which is the size of the tables below.  */
 153
 154 static unsigned int combine_max_regno;
 155
 156 struct reg_stat {
 157   /* Record last point of death of (hard or pseudo) register n.  */
 158   rtx                           last_death;
 159
 160   /* Record last point of modification of (hard or pseudo) register n.  */
 161   rtx                           last_set;
 162
 163   /* The next group of fields allows the recording of the last value assigned
 164      to (hard or pseudo) register n.  We use this information to see if an
 165      operation being processed is redundant given a prior operation performed
 166      on the register.  For example, an `and' with a constant is redundant if
 167      all the zero bits are already known to be turned off.
 168
 169      We use an approach similar to that used by cse, but change it in the
 170      following ways:
 171
 172      (1) We do not want to reinitialize at each label.
 173      (2) It is useful, but not critical, to know the actual value assigned
 174          to a register.  Often just its form is helpful.
 175
 176      Therefore, we maintain the following fields:
 177
 178      last_set_value             the last value assigned
 179      last_set_label             records the value of label_tick when the
 180                                 register was assigned
 181      last_set_table_tick        records the value of label_tick when a
 182                                 value using the register is assigned
 183      last_set_invalid           set to nonzero when it is not valid
 184                                 to use the value of this register in some
 185                                 register's value
 186
 187      To understand the usage of these tables, it is important to understand
 188      the distinction between the value in last_set_value being valid and
 189      the register being validly contained in some other expression in the
 190      table.
 191
 192      (The next two parameters are out of date).
 193
 194      reg_stat[i].last_set_value is valid if it is nonzero, and either
 195      reg_n_sets[i] is 1 or reg_stat[i].last_set_label == label_tick.
 196
 197      Register I may validly appear in any expression returned for the value
 198      of another register if reg_n_sets[i] is 1.  It may also appear in the
 199      value for register J if reg_stat[j].last_set_invalid is zero, or
 200      reg_stat[i].last_set_label < reg_stat[j].last_set_label.
 201
 202      If an expression is found in the table containing a register which may
 203      not validly appear in an expression, the register is replaced by
 204      something that won't match, (clobber (const_int 0)).  */
 205
 206   /* Record last value assigned to (hard or pseudo) register n.  */
 207
 208   rtx                           last_set_value;
 209
 210   /* Record the value of label_tick when an expression involving register n
 211      is placed in last_set_value.  */
 212
 213   int                           last_set_table_tick;
 214
 215   /* Record the value of label_tick when the value for register n is placed in
 216      last_set_value.  */
 217
 218   int                           last_set_label;
 219
 220   /* These fields are maintained in parallel with last_set_value and are
 221      used to store the mode in which the register was last set, the bits
 222      that were known to be zero when it was last set, and the number of
 223      sign bits copies it was known to have when it was last set.  */
 224
 225   unsigned HOST_WIDE_INT        last_set_nonzero_bits;
 226   char                          last_set_sign_bit_copies;
 227   ENUM_BITFIELD(machine_mode)   last_set_mode : 8;
 228
 229   /* Set nonzero if references to register n in expressions should not be
 230      used.  last_set_invalid is set nonzero when this register is being
 231      assigned to and last_set_table_tick == label_tick.  */
 232
 233   char                          last_set_invalid;
 234
 235   /* Some registers that are set more than once and used in more than one
 236      basic block are nevertheless always set in similar ways.  For example,
 237      a QImode register may be loaded from memory in two places on a machine
 238      where byte loads zero extend.
 239
 240      We record in the following fields if a register has some leading bits
 241      that are always equal to the sign bit, and what we know about the
 242      nonzero bits of a register, specifically which bits are known to be
 243      zero.
 244
 245      If an entry is zero, it means that we don't know anything special.  */
 246
 247   unsigned char                 sign_bit_copies;
 248
 249   unsigned HOST_WIDE_INT        nonzero_bits;
 250
 251   /* Record the value of the label_tick when the last truncation
 252      happened.  The field truncated_to_mode is only valid if
 253      truncation_label == label_tick.  */
 254
 255   int                           truncation_label;
 256
 257   /* Record the last truncation seen for this register.  If truncation
 258      is not a nop to this mode we might be able to save an explicit
 259      truncation if we know that value already contains a truncated
 260      value.  */
 261
 262   ENUM_BITFIELD(machine_mode)   truncated_to_mode : 8;
 263 };
 264
 265 static struct reg_stat *reg_stat;
 266
 267 /* Record the cuid of the last insn that invalidated memory
 268    (anything that writes memory, and subroutine calls, but not pushes).  */
 269
 270 static int mem_last_set;
 271
 272 /* Record the cuid of the last CALL_INSN
 273    so we can tell whether a potential combination crosses any calls.  */
 274
 275 static int last_call_cuid;
 276
 277 /* When `subst' is called, this is the insn that is being modified
 278    (by combining in a previous insn).  The PATTERN of this insn
 279    is still the old pattern partially modified and it should not be
 280    looked at, but this may be used to examine the successors of the insn
 281    to judge whether a simplification is valid.  */
 282
 283 static rtx subst_insn;
 284
 285 /* This is the lowest CUID that `subst' is currently dealing with.
 286    get_last_value will not return a value if the register was set at or
 287    after this CUID.  If not for this mechanism, we could get confused if
 288    I2 or I1 in try_combine were an insn that used the old value of a register
 289    to obtain a new value.  In that case, we might erroneously get the
 290    new value of the register when we wanted the old one.  */
 291
 292 static int subst_low_cuid;
 293
 294 /* This contains any hard registers that are used in newpat; reg_dead_at_p
 295    must consider all these registers to be always live.  */
 296
 297 static HARD_REG_SET newpat_used_regs;
 298
 299 /* This is an insn to which a LOG_LINKS entry has been added.  If this
 300    insn is the earlier than I2 or I3, combine should rescan starting at
 301    that location.  */
 302
 303 static rtx added_links_insn;
 304
 305 /* Basic block in which we are performing combines.  */
 306 static basic_block this_basic_block;
 307
 308 /* A bitmap indicating which blocks had registers go dead at entry.
 309    After combine, we'll need to re-do global life analysis with
 310    those blocks as starting points.  */
 311 static sbitmap refresh_blocks;
 312 \f
 313 /* The following array records the insn_rtx_cost for every insn
 314    in the instruction stream.  */
 315
 316 static int *uid_insn_cost;
 317
 318 /* Length of the currently allocated uid_insn_cost array.  */
 319
 320 static int last_insn_cost;
 321
 322 /* Incremented for each label.  */
 323
 324 static int label_tick;
 325
 326 /* Mode used to compute significance in reg_stat[].nonzero_bits.  It is the
 327    largest integer mode that can fit in HOST_BITS_PER_WIDE_INT.  */
 328
 329 static enum machine_mode nonzero_bits_mode;
 330
 331 /* Nonzero when reg_stat[].nonzero_bits and reg_stat[].sign_bit_copies can
 332    be safely used.  It is zero while computing them and after combine has
 333    completed.  This former test prevents propagating values based on
 334    previously set values, which can be incorrect if a variable is modified
 335    in a loop.  */
 336
 337 static int nonzero_sign_valid;
 338
 339 \f
 340 /* Record one modification to rtl structure
 341    to be undone by storing old_contents into *where.  */
 342
 343 struct undo
 344 {
 345   struct undo *next;
 346   enum { UNDO_RTX, UNDO_INT, UNDO_MODE } kind;
 347   union { rtx r; int i; enum machine_mode m; } old_contents;
 348   union { rtx *r; int *i; } where;
 349 };
 350
 351 /* Record a bunch of changes to be undone, up to MAX_UNDO of them.
 352    num_undo says how many are currently recorded.
 353
 354    other_insn is nonzero if we have modified some other insn in the process
 355    of working on subst_insn.  It must be verified too.  */
 356
 357 struct undobuf
 358 {
 359   struct undo *undos;
 360   struct undo *frees;
 361   rtx other_insn;
 362 };
 363
 364 static struct undobuf undobuf;
 365
 366 /* Number of times the pseudo being substituted for
 367    was found and replaced.  */
 368
 369 static int n_occurrences;
 370
 371 static rtx reg_nonzero_bits_for_combine (rtx, enum machine_mode, rtx,
 372                                          enum machine_mode,
 373                                          unsigned HOST_WIDE_INT,
 374                                          unsigned HOST_WIDE_INT *);
 375 static rtx reg_num_sign_bit_copies_for_combine (rtx, enum machine_mode, rtx,
 376                                                 enum machine_mode,
 377                                                 unsigned int, unsigned int *);
 378 static void do_SUBST (rtx *, rtx);
 379 static void do_SUBST_INT (int *, int);
 380 static void init_reg_last (void);
 381 static void setup_incoming_promotions (void);
 382 static void set_nonzero_bits_and_sign_copies (rtx, rtx, void *);
 383 static int cant_combine_insn_p (rtx);
 384 static int can_combine_p (rtx, rtx, rtx, rtx, rtx *, rtx *);
 385 static int combinable_i3pat (rtx, rtx *, rtx, rtx, int, rtx *);
 386 static int contains_muldiv (rtx);
 387 static rtx try_combine (rtx, rtx, rtx, int *);
 388 static void undo_all (void);
 389 static void undo_commit (void);
 390 static rtx *find_split_point (rtx *, rtx);
 391 static rtx subst (rtx, rtx, rtx, int, int);
 392 static rtx combine_simplify_rtx (rtx, enum machine_mode, int);
 393 static rtx simplify_if_then_else (rtx);
 394 static rtx simplify_set (rtx);
 395 static rtx simplify_logical (rtx);
 396 static rtx expand_compound_operation (rtx);
 397 static rtx expand_field_assignment (rtx);
 398 static rtx make_extraction (enum machine_mode, rtx, HOST_WIDE_INT,
 399                             rtx, unsigned HOST_WIDE_INT, int, int, int);
 400 static rtx extract_left_shift (rtx, int);
 401 static rtx make_compound_operation (rtx, enum rtx_code);
 402 static int get_pos_from_mask (unsigned HOST_WIDE_INT,
 403                               unsigned HOST_WIDE_INT *);
 404 static rtx canon_reg_for_combine (rtx, rtx);
 405 static rtx force_to_mode (rtx, enum machine_mode,
 406                           unsigned HOST_WIDE_INT, int);
 407 static rtx if_then_else_cond (rtx, rtx *, rtx *);
 408 static rtx known_cond (rtx, enum rtx_code, rtx, rtx);
 409 static int rtx_equal_for_field_assignment_p (rtx, rtx);
 410 static rtx make_field_assignment (rtx);
 411 static rtx apply_distributive_law (rtx);
 412 static rtx distribute_and_simplify_rtx (rtx, int);
 413 static rtx simplify_and_const_int_1 (enum machine_mode, rtx,
 414                                      unsigned HOST_WIDE_INT);
 415 static rtx simplify_and_const_int (rtx, enum machine_mode, rtx,
 416                                    unsigned HOST_WIDE_INT);
 417 static int merge_outer_ops (enum rtx_code *, HOST_WIDE_INT *, enum rtx_code,
 418                             HOST_WIDE_INT, enum machine_mode, int *);
 419 static rtx simplify_shift_const_1 (enum rtx_code, enum machine_mode, rtx, int);
 420 static rtx simplify_shift_const (rtx, enum rtx_code, enum machine_mode, rtx,
 421                                  int);
 422 static int recog_for_combine (rtx *, rtx, rtx *);
 423 static rtx gen_lowpart_for_combine (enum machine_mode, rtx);
 424 static enum rtx_code simplify_comparison (enum rtx_code, rtx *, rtx *);
 425 static void update_table_tick (rtx);
 426 static void record_value_for_reg (rtx, rtx, rtx);
 427 static void check_conversions (rtx, rtx);
 428 static void record_dead_and_set_regs_1 (rtx, rtx, void *);
 429 static void record_dead_and_set_regs (rtx);
 430 static int get_last_value_validate (rtx *, rtx, int, int);
 431 static rtx get_last_value (rtx);
 432 static int use_crosses_set_p (rtx, int);
 433 static void reg_dead_at_p_1 (rtx, rtx, void *);
 434 static int reg_dead_at_p (rtx, rtx);
 435 static void move_deaths (rtx, rtx, int, rtx, rtx *);
 436 static int reg_bitfield_target_p (rtx, rtx);
 437 static void distribute_notes (rtx, rtx, rtx, rtx, rtx, rtx);
 438 static void distribute_links (rtx);
 439 static void mark_used_regs_combine (rtx);
 440 static int insn_cuid (rtx);
 441 static void record_promoted_value (rtx, rtx);
 442 static int unmentioned_reg_p_1 (rtx *, void *);
 443 static bool unmentioned_reg_p (rtx, rtx);
 444 static void record_truncated_value (rtx);
 445 static bool reg_truncated_to_mode (enum machine_mode, rtx);
 446 static rtx gen_lowpart_or_truncate (enum machine_mode, rtx);
 447 \f
 448
 449 /* It is not safe to use ordinary gen_lowpart in combine.
 450    See comments in gen_lowpart_for_combine.  */
 451 #undef RTL_HOOKS_GEN_LOWPART
 452 #define RTL_HOOKS_GEN_LOWPART              gen_lowpart_for_combine
 453
 454 /* Our implementation of gen_lowpart never emits a new pseudo.  */
 455 #undef RTL_HOOKS_GEN_LOWPART_NO_EMIT
 456 #define RTL_HOOKS_GEN_LOWPART_NO_EMIT      gen_lowpart_for_combine
 457
 458 #undef RTL_HOOKS_REG_NONZERO_REG_BITS
 459 #define RTL_HOOKS_REG_NONZERO_REG_BITS     reg_nonzero_bits_for_combine
 460
 461 #undef RTL_HOOKS_REG_NUM_SIGN_BIT_COPIES
 462 #define RTL_HOOKS_REG_NUM_SIGN_BIT_COPIES  reg_num_sign_bit_copies_for_combine
 463
 464 #undef RTL_HOOKS_REG_TRUNCATED_TO_MODE
 465 #define RTL_HOOKS_REG_TRUNCATED_TO_MODE    reg_truncated_to_mode
 466
 467 static const struct rtl_hooks combine_rtl_hooks = RTL_HOOKS_INITIALIZER;
 468
 469 \f
 470 /* Substitute NEWVAL, an rtx expression, into INTO, a place in some
 471    insn.  The substitution can be undone by undo_all.  If INTO is already
 472    set to NEWVAL, do not record this change.  Because computing NEWVAL might
 473    also call SUBST, we have to compute it before we put anything into
 474    the undo table.  */
 475
 476 static void
 477 do_SUBST (rtx *into, rtx newval)
 478 {
 479   struct undo *buf;
 480   rtx oldval = *into;
 481
 482   if (oldval == newval)
 483     return;
 484
 485   /* We'd like to catch as many invalid transformations here as
 486      possible.  Unfortunately, there are way too many mode changes
 487      that are perfectly valid, so we'd waste too much effort for
 488      little gain doing the checks here.  Focus on catching invalid
 489      transformations involving integer constants.  */
 490   if (GET_MODE_CLASS (GET_MODE (oldval)) == MODE_INT
 491       && GET_CODE (newval) == CONST_INT)
 492     {
 493       /* Sanity check that we're replacing oldval with a CONST_INT
 494          that is a valid sign-extension for the original mode.  */
 495       gcc_assert (INTVAL (newval)
 496                   == trunc_int_for_mode (INTVAL (newval), GET_MODE (oldval)));
 497
 498       /* Replacing the operand of a SUBREG or a ZERO_EXTEND with a
 499          CONST_INT is not valid, because after the replacement, the
 500          original mode would be gone.  Unfortunately, we can't tell
 501          when do_SUBST is called to replace the operand thereof, so we
 502          perform this test on oldval instead, checking whether an
 503          invalid replacement took place before we got here.  */
 504       gcc_assert (!(GET_CODE (oldval) == SUBREG
 505                     && GET_CODE (SUBREG_REG (oldval)) == CONST_INT));
 506       gcc_assert (!(GET_CODE (oldval) == ZERO_EXTEND
 507                     && GET_CODE (XEXP (oldval, 0)) == CONST_INT));
 508     }
 509
 510   if (undobuf.frees)
 511     buf = undobuf.frees, undobuf.frees = buf->next;
 512   else
 513     buf = XNEW (struct undo);
 514
 515   buf->kind = UNDO_RTX;
 516   buf->where.r = into;
 517   buf->old_contents.r = oldval;
 518   *into = newval;
 519
 520   buf->next = undobuf.undos, undobuf.undos = buf;
 521 }
 522
 523 #define SUBST(INTO, NEWVAL)     do_SUBST(&(INTO), (NEWVAL))
 524
 525 /* Similar to SUBST, but NEWVAL is an int expression.  Note that substitution
 526    for the value of a HOST_WIDE_INT value (including CONST_INT) is
 527    not safe.  */
 528
 529 static void
 530 do_SUBST_INT (int *into, int newval)
 531 {
 532   struct undo *buf;
 533   int oldval = *into;
 534
 535   if (oldval == newval)
 536     return;
 537
 538   if (undobuf.frees)
 539     buf = undobuf.frees, undobuf.frees = buf->next;
 540   else
 541     buf = XNEW (struct undo);
 542
 543   buf->kind = UNDO_INT;
 544   buf->where.i = into;
 545   buf->old_contents.i = oldval;
 546   *into = newval;
 547
 548   buf->next = undobuf.undos, undobuf.undos = buf;
 549 }
 550
 551 #define SUBST_INT(INTO, NEWVAL)  do_SUBST_INT(&(INTO), (NEWVAL))
 552
 553 /* Similar to SUBST, but just substitute the mode.  This is used when
 554    changing the mode of a pseudo-register, so that any other
 555    references to the entry in the regno_reg_rtx array will change as
 556    well.  */
 557
 558 static void
 559 do_SUBST_MODE (rtx *into, enum machine_mode newval)
 560 {
 561   struct undo *buf;
 562   enum machine_mode oldval = GET_MODE (*into);
 563
 564   if (oldval == newval)
 565     return;
 566
 567   if (undobuf.frees)
 568     buf = undobuf.frees, undobuf.frees = buf->next;
 569   else
 570     buf = XNEW (struct undo);
 571
 572   buf->kind = UNDO_MODE;
 573   buf->where.r = into;
 574   buf->old_contents.m = oldval;
 575   PUT_MODE (*into, newval);
 576
 577   buf->next = undobuf.undos, undobuf.undos = buf;
 578 }
 579
 580 #define SUBST_MODE(INTO, NEWVAL)  do_SUBST_MODE(&(INTO), (NEWVAL))
 581 \f
 582 /* Subroutine of try_combine.  Determine whether the combine replacement
 583    patterns NEWPAT and NEWI2PAT are cheaper according to insn_rtx_cost
 584    that the original instruction sequence I1, I2 and I3.  Note that I1
 585    and/or NEWI2PAT may be NULL_RTX.  This function returns false, if the
 586    costs of all instructions can be estimated, and the replacements are
 587    more expensive than the original sequence.  */
 588
 589 static bool
 590 combine_validate_cost (rtx i1, rtx i2, rtx i3, rtx newpat, rtx newi2pat)
 591 {
 592   int i1_cost, i2_cost, i3_cost;
 593   int new_i2_cost, new_i3_cost;
 594   int old_cost, new_cost;
 595
 596   /* Lookup the original insn_rtx_costs.  */
 597   i2_cost = INSN_UID (i2) <= last_insn_cost
 598             ? uid_insn_cost[INSN_UID (i2)] : 0;
 599   i3_cost = INSN_UID (i3) <= last_insn_cost
 600             ? uid_insn_cost[INSN_UID (i3)] : 0;
 601
 602   if (i1)
 603     {
 604       i1_cost = INSN_UID (i1) <= last_insn_cost
 605                 ? uid_insn_cost[INSN_UID (i1)] : 0;
 606       old_cost = (i1_cost > 0 && i2_cost > 0 && i3_cost > 0)
 607                  ? i1_cost + i2_cost + i3_cost : 0;
 608     }
 609   else
 610     {
 611       old_cost = (i2_cost > 0 && i3_cost > 0) ? i2_cost + i3_cost : 0;
 612       i1_cost = 0;
 613     }
 614
 615   /* Calculate the replacement insn_rtx_costs.  */
 616   new_i3_cost = insn_rtx_cost (newpat);
 617   if (newi2pat)
 618     {
 619       new_i2_cost = insn_rtx_cost (newi2pat);
 620       new_cost = (new_i2_cost > 0 && new_i3_cost > 0)
 621                  ? new_i2_cost + new_i3_cost : 0;
 622     }
 623   else
 624     {
 625       new_cost = new_i3_cost;
 626       new_i2_cost = 0;
 627     }
 628
 629   if (undobuf.other_insn)
 630     {
 631       int old_other_cost, new_other_cost;
 632
 633       old_other_cost = (INSN_UID (undobuf.other_insn) <= last_insn_cost
 634                         ? uid_insn_cost[INSN_UID (undobuf.other_insn)] : 0);
 635       new_other_cost = insn_rtx_cost (PATTERN (undobuf.other_insn));
 636       if (old_other_cost > 0 && new_other_cost > 0)
 637         {
 638           old_cost += old_other_cost;
 639           new_cost += new_other_cost;
 640         }
 641       else
 642         old_cost = 0;
 643     }
 644
 645   /* Disallow this recombination if both new_cost and old_cost are
 646      greater than zero, and new_cost is greater than old cost.  */
 647   if (old_cost > 0
 648       && new_cost > old_cost)
 649     {
 650       if (dump_file)
 651         {
 652           if (i1)
 653             {
 654               fprintf (dump_file,
 655                        "rejecting combination of insns %d, %d and %d\n",
 656                        INSN_UID (i1), INSN_UID (i2), INSN_UID (i3));
 657               fprintf (dump_file, "original costs %d + %d + %d = %d\n",
 658                        i1_cost, i2_cost, i3_cost, old_cost);
 659             }
 660           else
 661             {
 662               fprintf (dump_file,
 663                        "rejecting combination of insns %d and %d\n",
 664                        INSN_UID (i2), INSN_UID (i3));
 665               fprintf (dump_file, "original costs %d + %d = %d\n",
 666                        i2_cost, i3_cost, old_cost);
 667             }
 668
 669           if (newi2pat)
 670             {
 671               fprintf (dump_file, "replacement costs %d + %d = %d\n",
 672                        new_i2_cost, new_i3_cost, new_cost);
 673             }
 674           else
 675             fprintf (dump_file, "replacement cost %d\n", new_cost);
 676         }
 677
 678       return false;
 679     }
 680
 681   /* Update the uid_insn_cost array with the replacement costs.  */
 682   uid_insn_cost[INSN_UID (i2)] = new_i2_cost;
 683   uid_insn_cost[INSN_UID (i3)] = new_i3_cost;
 684   if (i1)
 685     uid_insn_cost[INSN_UID (i1)] = 0;
 686
 687   return true;
 688 }
 689 \f
 690 /* Main entry point for combiner.  F is the first insn of the function.
 691    NREGS is the first unused pseudo-reg number.
 692
 693    Return nonzero if the combiner has turned an indirect jump
 694    instruction into a direct jump.  */
 695 static int
 696 combine_instructions (rtx f, unsigned int nregs)
 697 {
 698   rtx insn, next;
 699 #ifdef HAVE_cc0
 700   rtx prev;
 701 #endif
 702   int i;
 703   unsigned int j = 0;
 704   rtx links, nextlinks;
 705   sbitmap_iterator sbi;
 706
 707   int new_direct_jump_p = 0;
 708
 709   combine_attempts = 0;
 710   combine_merges = 0;
 711   combine_extras = 0;
 712   combine_successes = 0;
 713
 714   combine_max_regno = nregs;
 715
 716   rtl_hooks = combine_rtl_hooks;
 717
 718   reg_stat = XCNEWVEC (struct reg_stat, nregs);
 719
 720   init_recog_no_volatile ();
 721
 722   /* Compute maximum uid value so uid_cuid can be allocated.  */
 723
 724   for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
 725     if (INSN_UID (insn) > i)
 726       i = INSN_UID (insn);
 727
 728   uid_cuid = XNEWVEC (int, i + 1);
 729   max_uid_cuid = i;
 730
 731   nonzero_bits_mode = mode_for_size (HOST_BITS_PER_WIDE_INT, MODE_INT, 0);
 732
 733   /* Don't use reg_stat[].nonzero_bits when computing it.  This can cause
 734      problems when, for example, we have j <<= 1 in a loop.  */
 735
 736   nonzero_sign_valid = 0;
 737
 738   /* Compute the mapping from uids to cuids.
 739      Cuids are numbers assigned to insns, like uids,
 740      except that cuids increase monotonically through the code.
 741
 742      Scan all SETs and see if we can deduce anything about what
 743      bits are known to be zero for some registers and how many copies
 744      of the sign bit are known to exist for those registers.
 745
 746      Also set any known values so that we can use it while searching
 747      for what bits are known to be set.  */
 748
 749   label_tick = 1;
 750
 751   setup_incoming_promotions ();
 752
 753   refresh_blocks = sbitmap_alloc (last_basic_block);
 754   sbitmap_zero (refresh_blocks);
 755
 756   /* Allocate array of current insn_rtx_costs.  */
 757   uid_insn_cost = XCNEWVEC (int, max_uid_cuid + 1);
 758   last_insn_cost = max_uid_cuid;
 759
 760   for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
 761     {
 762       uid_cuid[INSN_UID (insn)] = ++i;
 763       subst_low_cuid = i;
 764       subst_insn = insn;
 765
 766       if (INSN_P (insn))
 767         {
 768           note_stores (PATTERN (insn), set_nonzero_bits_and_sign_copies,
 769                        NULL);
 770           record_dead_and_set_regs (insn);
 771
 772 #ifdef AUTO_INC_DEC
 773           for (links = REG_NOTES (insn); links; links = XEXP (links, 1))
 774             if (REG_NOTE_KIND (links) == REG_INC)
 775               set_nonzero_bits_and_sign_copies (XEXP (links, 0), NULL_RTX,
 776                                                 NULL);
 777 #endif
 778
 779           /* Record the current insn_rtx_cost of this instruction.  */
 780           if (NONJUMP_INSN_P (insn))
 781             uid_insn_cost[INSN_UID (insn)] = insn_rtx_cost (PATTERN (insn));
 782           if (dump_file)
 783             fprintf(dump_file, "insn_cost %d: %d\n",
 784                     INSN_UID (insn), uid_insn_cost[INSN_UID (insn)]);
 785         }
 786
 787       if (LABEL_P (insn))
 788         label_tick++;
 789     }
 790
 791   nonzero_sign_valid = 1;
 792
 793   /* Now scan all the insns in forward order.  */
 794
 795   label_tick = 1;
 796   last_call_cuid = 0;
 797   mem_last_set = 0;
 798   init_reg_last ();
 799   setup_incoming_promotions ();
 800
 801   FOR_EACH_BB (this_basic_block)
 802     {
 803       for (insn = BB_HEAD (this_basic_block);
 804            insn != NEXT_INSN (BB_END (this_basic_block));
 805            insn = next ? next : NEXT_INSN (insn))
 806         {
 807           next = 0;
 808
 809           if (LABEL_P (insn))
 810             label_tick++;
 811
 812           else if (INSN_P (insn))
 813             {
 814               /* See if we know about function return values before this
 815                  insn based upon SUBREG flags.  */
 816               check_conversions (insn, PATTERN (insn));
 817
 818               /* Try this insn with each insn it links back to.  */
 819
 820               for (links = LOG_LINKS (insn); links; links = XEXP (links, 1))
 821                 if ((next = try_combine (insn, XEXP (links, 0),
 822                                          NULL_RTX, &new_direct_jump_p)) != 0)
 823                   goto retry;
 824
 825               /* Try each sequence of three linked insns ending with this one.  */
 826
 827               for (links = LOG_LINKS (insn); links; links = XEXP (links, 1))
 828                 {
 829                   rtx link = XEXP (links, 0);
 830
 831                   /* If the linked insn has been replaced by a note, then there
 832                      is no point in pursuing this chain any further.  */
 833                   if (NOTE_P (link))
 834                     continue;
 835
 836                   for (nextlinks = LOG_LINKS (link);
 837                        nextlinks;
 838                        nextlinks = XEXP (nextlinks, 1))
 839                     if ((next = try_combine (insn, link,
 840                                              XEXP (nextlinks, 0),
 841                                              &new_direct_jump_p)) != 0)
 842                       goto retry;
 843                 }
 844
 845 #ifdef HAVE_cc0
 846               /* Try to combine a jump insn that uses CC0
 847                  with a preceding insn that sets CC0, and maybe with its
 848                  logical predecessor as well.
 849                  This is how we make decrement-and-branch insns.
 850                  We need this special code because data flow connections
 851                  via CC0 do not get entered in LOG_LINKS.  */
 852
 853               if (JUMP_P (insn)
 854                   && (prev = prev_nonnote_insn (insn)) != 0
 855                   && NONJUMP_INSN_P (prev)
 856                   && sets_cc0_p (PATTERN (prev)))
 857                 {
 858                   if ((next = try_combine (insn, prev,
 859                                            NULL_RTX, &new_direct_jump_p)) != 0)
 860                     goto retry;
 861
 862                   for (nextlinks = LOG_LINKS (prev); nextlinks;
 863                        nextlinks = XEXP (nextlinks, 1))
 864                     if ((next = try_combine (insn, prev,
 865                                              XEXP (nextlinks, 0),
 866                                              &new_direct_jump_p)) != 0)
 867                       goto retry;
 868                 }
 869
 870               /* Do the same for an insn that explicitly references CC0.  */
 871               if (NONJUMP_INSN_P (insn)
 872                   && (prev = prev_nonnote_insn (insn)) != 0
 873                   && NONJUMP_INSN_P (prev)
 874                   && sets_cc0_p (PATTERN (prev))
 875                   && GET_CODE (PATTERN (insn)) == SET
 876                   && reg_mentioned_p (cc0_rtx, SET_SRC (PATTERN (insn))))
 877                 {
 878                   if ((next = try_combine (insn, prev,
 879                                            NULL_RTX, &new_direct_jump_p)) != 0)
 880                     goto retry;
 881
 882                   for (nextlinks = LOG_LINKS (prev); nextlinks;
 883                        nextlinks = XEXP (nextlinks, 1))
 884                     if ((next = try_combine (insn, prev,
 885                                              XEXP (nextlinks, 0),
 886                                              &new_direct_jump_p)) != 0)
 887                       goto retry;
 888                 }
 889
 890               /* Finally, see if any of the insns that this insn links to
 891                  explicitly references CC0.  If so, try this insn, that insn,
 892                  and its predecessor if it sets CC0.  */
 893               for (links = LOG_LINKS (insn); links; links = XEXP (links, 1))
 894                 if (NONJUMP_INSN_P (XEXP (links, 0))
 895                     && GET_CODE (PATTERN (XEXP (links, 0))) == SET
 896                     && reg_mentioned_p (cc0_rtx, SET_SRC (PATTERN (XEXP (links, 0))))
 897                     && (prev = prev_nonnote_insn (XEXP (links, 0))) != 0
 898                     && NONJUMP_INSN_P (prev)
 899                     && sets_cc0_p (PATTERN (prev))
 900                     && (next = try_combine (insn, XEXP (links, 0),
 901                                             prev, &new_direct_jump_p)) != 0)
 902                   goto retry;
 903 #endif
 904
 905               /* Try combining an insn with two different insns whose results it
 906                  uses.  */
 907               for (links = LOG_LINKS (insn); links; links = XEXP (links, 1))
 908                 for (nextlinks = XEXP (links, 1); nextlinks;
 909                      nextlinks = XEXP (nextlinks, 1))
 910                   if ((next = try_combine (insn, XEXP (links, 0),
 911                                            XEXP (nextlinks, 0),
 912                                            &new_direct_jump_p)) != 0)
 913                     goto retry;
 914
 915               /* Try this insn with each REG_EQUAL note it links back to.  */
 916               for (links = LOG_LINKS (insn); links; links = XEXP (links, 1))
 917                 {
 918                   rtx set, note;
 919                   rtx temp = XEXP (links, 0);
 920                   if ((set = single_set (temp)) != 0
 921                       && (note = find_reg_equal_equiv_note (temp)) != 0
 922                       && (note = XEXP (note, 0), GET_CODE (note)) != EXPR_LIST
 923                       /* Avoid using a register that may already been marked
 924                          dead by an earlier instruction.  */
 925                       && ! unmentioned_reg_p (note, SET_SRC (set))
 926                       && (GET_MODE (note) == VOIDmode
 927                           ? SCALAR_INT_MODE_P (GET_MODE (SET_DEST (set)))
 928                           : GET_MODE (SET_DEST (set)) == GET_MODE (note)))
 929                     {
 930                       /* Temporarily replace the set's source with the
 931                          contents of the REG_EQUAL note.  The insn will
 932                          be deleted or recognized by try_combine.  */
 933                       rtx orig = SET_SRC (set);
 934                       SET_SRC (set) = note;
 935                       replaced_rhs_insn = temp;
 936                       replaced_rhs_value = copy_rtx (note);
 937                       next = try_combine (insn, temp, NULL_RTX,
 938                                           &new_direct_jump_p);
 939                       replaced_rhs_insn = NULL;
 940                       if (next)
 941                         goto retry;
 942                       SET_SRC (set) = orig;
 943                     }
 944                 }
 945
 946               if (!NOTE_P (insn))
 947                 record_dead_and_set_regs (insn);
 948
 949             retry:
 950               ;
 951             }
 952         }
 953     }
 954   clear_bb_flags ();
 955
 956   EXECUTE_IF_SET_IN_SBITMAP (refresh_blocks, 0, j, sbi)
 957     BASIC_BLOCK (j)->flags |= BB_DIRTY;
 958   new_direct_jump_p |= purge_all_dead_edges ();
 959   delete_noop_moves ();
 960
 961   update_life_info_in_dirty_blocks (UPDATE_LIFE_GLOBAL_RM_NOTES,
 962                                     PROP_DEATH_NOTES | PROP_SCAN_DEAD_CODE
 963                                     | PROP_KILL_DEAD_CODE);
 964
 965   /* Clean up.  */
 966   sbitmap_free (refresh_blocks);
 967   free (uid_insn_cost);
 968   free (reg_stat);
 969   free (uid_cuid);
 970
 971   {
 972     struct undo *undo, *next;
 973     for (undo = undobuf.frees; undo; undo = next)
 974       {
 975         next = undo->next;
 976         free (undo);
 977       }
 978     undobuf.frees = 0;
 979   }
 980
 981   total_attempts += combine_attempts;
 982   total_merges += combine_merges;
 983   total_extras += combine_extras;
 984   total_successes += combine_successes;
 985
 986   nonzero_sign_valid = 0;
 987   rtl_hooks = general_rtl_hooks;
 988
 989   /* Make recognizer allow volatile MEMs again.  */
 990   init_recog ();
 991
 992   return new_direct_jump_p;
 993 }
 994
 995 /* Wipe the last_xxx fields of reg_stat in preparation for another pass.  */
 996
 997 static void
 998 init_reg_last (void)
 999 {
1000   unsigned int i;
1001   for (i = 0; i < combine_max_regno; i++)
1002     memset (reg_stat + i, 0, offsetof (struct reg_stat, sign_bit_copies));
1003 }
1004 \f
1005 /* Set up any promoted values for incoming argument registers.  */
1006
1007 static void
1008 setup_incoming_promotions (void)
1009 {
1010   unsigned int regno;
1011   rtx reg;
1012   enum machine_mode mode;
1013   int unsignedp;
1014   rtx first = get_insns ();
1015
1016   if (targetm.calls.promote_function_args (TREE_TYPE (cfun->decl)))
1017     {
1018       for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
1019         /* Check whether this register can hold an incoming pointer
1020            argument.  FUNCTION_ARG_REGNO_P tests outgoing register
1021            numbers, so translate if necessary due to register windows.  */
1022         if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (regno))
1023             && (reg = promoted_input_arg (regno, &mode, &unsignedp)) != 0)
1024           {
1025             record_value_for_reg
1026               (reg, first, gen_rtx_fmt_e ((unsignedp ? ZERO_EXTEND
1027                                            : SIGN_EXTEND),
1028                                           GET_MODE (reg),
1029                                           gen_rtx_CLOBBER (mode, const0_rtx)));
1030           }
1031     }
1032 }
1033 \f
1034 /* Called via note_stores.  If X is a pseudo that is narrower than
1035    HOST_BITS_PER_WIDE_INT and is being set, record what bits are known zero.
1036
1037    If we are setting only a portion of X and we can't figure out what
1038    portion, assume all bits will be used since we don't know what will
1039    be happening.
1040
1041    Similarly, set how many bits of X are known to be copies of the sign bit
1042    at all locations in the function.  This is the smallest number implied
1043    by any set of X.  */
1044
1045 static void
1046 set_nonzero_bits_and_sign_copies (rtx x, rtx set,
1047                                   void *data ATTRIBUTE_UNUSED)
1048 {
1049   unsigned int num;
1050
1051   if (REG_P (x)
1052       && REGNO (x) >= FIRST_PSEUDO_REGISTER
1053       /* If this register is undefined at the start of the file, we can't
1054          say what its contents were.  */
1055       && ! REGNO_REG_SET_P
1056          (ENTRY_BLOCK_PTR->next_bb->il.rtl->global_live_at_start, REGNO (x))
1057       && GET_MODE_BITSIZE (GET_MODE (x)) <= HOST_BITS_PER_WIDE_INT)
1058     {
1059       if (set == 0 || GET_CODE (set) == CLOBBER)
1060         {
1061           reg_stat[REGNO (x)].nonzero_bits = GET_MODE_MASK (GET_MODE (x));
1062           reg_stat[REGNO (x)].sign_bit_copies = 1;
1063           return;
1064         }
1065
1066       /* If this is a complex assignment, see if we can convert it into a
1067          simple assignment.  */
1068       set = expand_field_assignment (set);
1069
1070       /* If this is a simple assignment, or we have a paradoxical SUBREG,
1071          set what we know about X.  */
1072
1073       if (SET_DEST (set) == x
1074           || (GET_CODE (SET_DEST (set)) == SUBREG
1075               && (GET_MODE_SIZE (GET_MODE (SET_DEST (set)))
1076                   > GET_MODE_SIZE (GET_MODE (SUBREG_REG (SET_DEST (set)))))
1077               && SUBREG_REG (SET_DEST (set)) == x))
1078         {
1079           rtx src = SET_SRC (set);
1080
1081 #ifdef SHORT_IMMEDIATES_SIGN_EXTEND
1082           /* If X is narrower than a word and SRC is a non-negative
1083              constant that would appear negative in the mode of X,
1084              sign-extend it for use in reg_stat[].nonzero_bits because some
1085              machines (maybe most) will actually do the sign-extension
1086              and this is the conservative approach.
1087
1088              ??? For 2.5, try to tighten up the MD files in this regard
1089              instead of this kludge.  */
1090
1091           if (GET_MODE_BITSIZE (GET_MODE (x)) < BITS_PER_WORD
1092               && GET_CODE (src) == CONST_INT
1093               && INTVAL (src) > 0
1094               && 0 != (INTVAL (src)
1095                        & ((HOST_WIDE_INT) 1
1096                           << (GET_MODE_BITSIZE (GET_MODE (x)) - 1))))
1097             src = GEN_INT (INTVAL (src)
1098                            | ((HOST_WIDE_INT) (-1)
1099                               << GET_MODE_BITSIZE (GET_MODE (x))));
1100 #endif
1101
1102           /* Don't call nonzero_bits if it cannot change anything.  */
1103           if (reg_stat[REGNO (x)].nonzero_bits != ~(unsigned HOST_WIDE_INT) 0)
1104             reg_stat[REGNO (x)].nonzero_bits
1105               |= nonzero_bits (src, nonzero_bits_mode);
1106           num = num_sign_bit_copies (SET_SRC (set), GET_MODE (x));
1107           if (reg_stat[REGNO (x)].sign_bit_copies == 0
1108               || reg_stat[REGNO (x)].sign_bit_copies > num)
1109             reg_stat[REGNO (x)].sign_bit_copies = num;
1110         }
1111       else
1112         {
1113           reg_stat[REGNO (x)].nonzero_bits = GET_MODE_MASK (GET_MODE (x));
1114           reg_stat[REGNO (x)].sign_bit_copies = 1;
1115         }
1116     }
1117 }
1118 \f
1119 /* See if INSN can be combined into I3.  PRED and SUCC are optionally
1120    insns that were previously combined into I3 or that will be combined
1121    into the merger of INSN and I3.
1122
1123    Return 0 if the combination is not allowed for any reason.
1124
1125    If the combination is allowed, *PDEST will be set to the single
1126    destination of INSN and *PSRC to the single source, and this function
1127    will return 1.  */
1128
1129 static int
1130 can_combine_p (rtx insn, rtx i3, rtx pred ATTRIBUTE_UNUSED, rtx succ,
1131                rtx *pdest, rtx *psrc)
1132 {
1133   int i;
1134   rtx set = 0, src, dest;
1135   rtx p;
1136 #ifdef AUTO_INC_DEC
1137   rtx link;
1138 #endif
1139   int all_adjacent = (succ ? (next_active_insn (insn) == succ
1140                               && next_active_insn (succ) == i3)
1141                       : next_active_insn (insn) == i3);
1142
1143   /* Can combine only if previous insn is a SET of a REG, a SUBREG or CC0.
1144      or a PARALLEL consisting of such a SET and CLOBBERs.
1145
1146      If INSN has CLOBBER parallel parts, ignore them for our processing.
1147      By definition, these happen during the execution of the insn.  When it
1148      is merged with another insn, all bets are off.  If they are, in fact,
1149      needed and aren't also supplied in I3, they may be added by
1150      recog_for_combine.  Otherwise, it won't match.
1151
1152      We can also ignore a SET whose SET_DEST is mentioned in a REG_UNUSED
1153      note.
1154
1155      Get the source and destination of INSN.  If more than one, can't
1156      combine.  */
1157
1158   if (GET_CODE (PATTERN (insn)) == SET)
1159     set = PATTERN (insn);
1160   else if (GET_CODE (PATTERN (insn)) == PARALLEL
1161            && GET_CODE (XVECEXP (PATTERN (insn), 0, 0)) == SET)
1162     {
1163       for (i = 0; i < XVECLEN (PATTERN (insn), 0); i++)
1164         {
1165           rtx elt = XVECEXP (PATTERN (insn), 0, i);
1166           rtx note;
1167
1168           switch (GET_CODE (elt))
1169             {
1170             /* This is important to combine floating point insns
1171                for the SH4 port.  */
1172             case USE:
1173               /* Combining an isolated USE doesn't make sense.
1174                  We depend here on combinable_i3pat to reject them.  */
1175               /* The code below this loop only verifies that the inputs of
1176                  the SET in INSN do not change.  We call reg_set_between_p
1177                  to verify that the REG in the USE does not change between
1178                  I3 and INSN.
1179                  If the USE in INSN was for a pseudo register, the matching
1180                  insn pattern will likely match any register; combining this
1181                  with any other USE would only be safe if we knew that the
1182                  used registers have identical values, or if there was
1183                  something to tell them apart, e.g. different modes.  For
1184                  now, we forgo such complicated tests and simply disallow
1185                  combining of USES of pseudo registers with any other USE.  */
1186               if (REG_P (XEXP (elt, 0))
1187                   && GET_CODE (PATTERN (i3)) == PARALLEL)
1188                 {
1189                   rtx i3pat = PATTERN (i3);
1190                   int i = XVECLEN (i3pat, 0) - 1;
1191                   unsigned int regno = REGNO (XEXP (elt, 0));
1192
1193                   do
1194                     {
1195                       rtx i3elt = XVECEXP (i3pat, 0, i);
1196
1197                       if (GET_CODE (i3elt) == USE
1198                           && REG_P (XEXP (i3elt, 0))
1199                           && (REGNO (XEXP (i3elt, 0)) == regno
1200                               ? reg_set_between_p (XEXP (elt, 0),
1201                                                    PREV_INSN (insn), i3)
1202                               : regno >= FIRST_PSEUDO_REGISTER))
1203                         return 0;
1204                     }
1205                   while (--i >= 0);
1206                 }
1207               break;
1208
1209               /* We can ignore CLOBBERs.  */
1210             case CLOBBER:
1211               break;
1212
1213             case SET:
1214               /* Ignore SETs whose result isn't used but not those that
1215                  have side-effects.  */
1216               if (find_reg_note (insn, REG_UNUSED, SET_DEST (elt))
1217                   && (!(note = find_reg_note (insn, REG_EH_REGION, NULL_RTX))
1218                       || INTVAL (XEXP (note, 0)) <= 0)
1219                   && ! side_effects_p (elt))
1220                 break;
1221
1222               /* If we have already found a SET, this is a second one and
1223                  so we cannot combine with this insn.  */
1224               if (set)
1225                 return 0;
1226
1227               set = elt;
1228               break;
1229
1230             default:
1231               /* Anything else means we can't combine.  */
1232               return 0;
1233             }
1234         }
1235
1236       if (set == 0
1237           /* If SET_SRC is an ASM_OPERANDS we can't throw away these CLOBBERs,
1238              so don't do anything with it.  */
1239           || GET_CODE (SET_SRC (set)) == ASM_OPERANDS)
1240         return 0;
1241     }
1242   else
1243     return 0;
1244
1245   if (set == 0)
1246     return 0;
1247
1248   set = expand_field_assignment (set);
1249   src = SET_SRC (set), dest = SET_DEST (set);
1250
1251   /* Don't eliminate a store in the stack pointer.  */
1252   if (dest == stack_pointer_rtx
1253       /* Don't combine with an insn that sets a register to itself if it has
1254          a REG_EQUAL note.  This may be part of a REG_NO_CONFLICT sequence.  */
1255       || (rtx_equal_p (src, dest) && find_reg_note (insn, REG_EQUAL, NULL_RTX))
1256       /* Can't merge an ASM_OPERANDS.  */
1257       || GET_CODE (src) == ASM_OPERANDS
1258       /* Can't merge a function call.  */
1259       || GET_CODE (src) == CALL
1260       /* Don't eliminate a function call argument.  */
1261       || (CALL_P (i3)
1262           && (find_reg_fusage (i3, USE, dest)
1263               || (REG_P (dest)
1264                   && REGNO (dest) < FIRST_PSEUDO_REGISTER
1265                   && global_regs[REGNO (dest)])))
1266       /* Don't substitute into an incremented register.  */
1267       || FIND_REG_INC_NOTE (i3, dest)
1268       || (succ && FIND_REG_INC_NOTE (succ, dest))
1269       /* Don't substitute into a non-local goto, this confuses CFG.  */
1270       || (JUMP_P (i3) && find_reg_note (i3, REG_NON_LOCAL_GOTO, NULL_RTX))
1271 #if 0
1272       /* Don't combine the end of a libcall into anything.  */
1273       /* ??? This gives worse code, and appears to be unnecessary, since no
1274          pass after flow uses REG_LIBCALL/REG_RETVAL notes.  Local-alloc does
1275          use REG_RETVAL notes for noconflict blocks, but other code here
1276          makes sure that those insns don't disappear.  */
1277       || find_reg_note (insn, REG_RETVAL, NULL_RTX)
1278 #endif
1279       /* Make sure that DEST is not used after SUCC but before I3.  */
1280       || (succ && ! all_adjacent
1281           && reg_used_between_p (dest, succ, i3))
1282       /* Make sure that the value that is to be substituted for the register
1283          does not use any registers whose values alter in between.  However,
1284          If the insns are adjacent, a use can't cross a set even though we
1285          think it might (this can happen for a sequence of insns each setting
1286          the same destination; last_set of that register might point to
1287          a NOTE).  If INSN has a REG_EQUIV note, the register is always
1288          equivalent to the memory so the substitution is valid even if there
1289          are intervening stores.  Also, don't move a volatile asm or
1290          UNSPEC_VOLATILE across any other insns.  */
1291       || (! all_adjacent
1292           && (((!MEM_P (src)
1293                 || ! find_reg_note (insn, REG_EQUIV, src))
1294                && use_crosses_set_p (src, INSN_CUID (insn)))
1295               || (GET_CODE (src) == ASM_OPERANDS && MEM_VOLATILE_P (src))
1296               || GET_CODE (src) == UNSPEC_VOLATILE))
1297       /* If there is a REG_NO_CONFLICT note for DEST in I3 or SUCC, we get
1298          better register allocation by not doing the combine.  */
1299       || find_reg_note (i3, REG_NO_CONFLICT, dest)
1300       || (succ && find_reg_note (succ, REG_NO_CONFLICT, dest))
1301       /* Don't combine across a CALL_INSN, because that would possibly
1302          change whether the life span of some REGs crosses calls or not,
1303          and it is a pain to update that information.
1304          Exception: if source is a constant, moving it later can't hurt.
1305          Accept that special case, because it helps -fforce-addr a lot.  */
1306       || (INSN_CUID (insn) < last_call_cuid && ! CONSTANT_P (src)))
1307     return 0;
1308
1309   /* DEST must either be a REG or CC0.  */
1310   if (REG_P (dest))
1311     {
1312       /* If register alignment is being enforced for multi-word items in all
1313          cases except for parameters, it is possible to have a register copy
1314          insn referencing a hard register that is not allowed to contain the
1315          mode being copied and which would not be valid as an operand of most
1316          insns.  Eliminate this problem by not combining with such an insn.
1317
1318          Also, on some machines we don't want to extend the life of a hard
1319          register.  */
1320
1321       if (REG_P (src)
1322           && ((REGNO (dest) < FIRST_PSEUDO_REGISTER
1323                && ! HARD_REGNO_MODE_OK (REGNO (dest), GET_MODE (dest)))
1324               /* Don't extend the life of a hard register unless it is
1325                  user variable (if we have few registers) or it can't
1326                  fit into the desired register (meaning something special
1327                  is going on).
1328                  Also avoid substituting a return register into I3, because
1329                  reload can't handle a conflict with constraints of other
1330                  inputs.  */
1331               || (REGNO (src) < FIRST_PSEUDO_REGISTER
1332                   && ! HARD_REGNO_MODE_OK (REGNO (src), GET_MODE (src)))))
1333         return 0;
1334     }
1335   else if (GET_CODE (dest) != CC0)
1336     return 0;
1337
1338
1339   if (GET_CODE (PATTERN (i3)) == PARALLEL)
1340     for (i = XVECLEN (PATTERN (i3), 0) - 1; i >= 0; i--)
1341       if (GET_CODE (XVECEXP (PATTERN (i3), 0, i)) == CLOBBER)
1342         {
1343           /* Don't substitute for a register intended as a clobberable
1344              operand.  */
1345           rtx reg = XEXP (XVECEXP (PATTERN (i3), 0, i), 0);
1346           if (rtx_equal_p (reg, dest))
1347             return 0;
1348
1349           /* If the clobber represents an earlyclobber operand, we must not
1350              substitute an expression containing the clobbered register.
1351              As we do not analyze the constraint strings here, we have to
1352              make the conservative assumption.  However, if the register is
1353              a fixed hard reg, the clobber cannot represent any operand;
1354              we leave it up to the machine description to either accept or
1355              reject use-and-clobber patterns.  */
1356           if (!REG_P (reg)
1357               || REGNO (reg) >= FIRST_PSEUDO_REGISTER
1358               || !fixed_regs[REGNO (reg)])
1359             if (reg_overlap_mentioned_p (reg, src))
1360               return 0;
1361         }
1362
1363   /* If INSN contains anything volatile, or is an `asm' (whether volatile
1364      or not), reject, unless nothing volatile comes between it and I3 */
1365
1366   if (GET_CODE (src) == ASM_OPERANDS || volatile_refs_p (src))
1367     {
1368       /* Make sure succ doesn't contain a volatile reference.  */
1369       if (succ != 0 && volatile_refs_p (PATTERN (succ)))
1370         return 0;
1371
1372       for (p = NEXT_INSN (insn); p != i3; p = NEXT_INSN (p))
1373         if (INSN_P (p) && p != succ && volatile_refs_p (PATTERN (p)))
1374           return 0;
1375     }
1376
1377   /* If INSN is an asm, and DEST is a hard register, reject, since it has
1378      to be an explicit register variable, and was chosen for a reason.  */
1379
1380   if (GET_CODE (src) == ASM_OPERANDS
1381       && REG_P (dest) && REGNO (dest) < FIRST_PSEUDO_REGISTER)
1382     return 0;
1383
1384   /* If there are any volatile insns between INSN and I3, reject, because
1385      they might affect machine state.  */
1386
1387   for (p = NEXT_INSN (insn); p != i3; p = NEXT_INSN (p))
1388     if (INSN_P (p) && p != succ && volatile_insn_p (PATTERN (p)))
1389       return 0;
1390
1391   /* If INSN contains an autoincrement or autodecrement, make sure that
1392      register is not used between there and I3, and not already used in
1393      I3 either.  Neither must it be used in PRED or SUCC, if they exist.
1394      Also insist that I3 not be a jump; if it were one
1395      and the incremented register were spilled, we would lose.  */
1396
1397 #ifdef AUTO_INC_DEC
1398   for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
1399     if (REG_NOTE_KIND (link) == REG_INC
1400         && (JUMP_P (i3)
1401             || reg_used_between_p (XEXP (link, 0), insn, i3)
1402             || (pred != NULL_RTX
1403                 && reg_overlap_mentioned_p (XEXP (link, 0), PATTERN (pred)))
1404             || (succ != NULL_RTX
1405                 && reg_overlap_mentioned_p (XEXP (link, 0), PATTERN (succ)))
1406             || reg_overlap_mentioned_p (XEXP (link, 0), PATTERN (i3))))
1407       return 0;
1408 #endif
1409
1410 #ifdef HAVE_cc0
1411   /* Don't combine an insn that follows a CC0-setting insn.
1412      An insn that uses CC0 must not be separated from the one that sets it.
1413      We do, however, allow I2 to follow a CC0-setting insn if that insn
1414      is passed as I1; in that case it will be deleted also.
1415      We also allow combining in this case if all the insns are adjacent
1416      because that would leave the two CC0 insns adjacent as well.
1417      It would be more logical to test whether CC0 occurs inside I1 or I2,
1418      but that would be much slower, and this ought to be equivalent.  */
1419
1420   p = prev_nonnote_insn (insn);
1421   if (p && p != pred && NONJUMP_INSN_P (p) && sets_cc0_p (PATTERN (p))
1422       && ! all_adjacent)
1423     return 0;
1424 #endif
1425
1426   /* If we get here, we have passed all the tests and the combination is
1427      to be allowed.  */
1428
1429   *pdest = dest;
1430   *psrc = src;
1431
1432   return 1;
1433 }
1434 \f
1435 /* LOC is the location within I3 that contains its pattern or the component
1436    of a PARALLEL of the pattern.  We validate that it is valid for combining.
1437
1438    One problem is if I3 modifies its output, as opposed to replacing it
1439    entirely, we can't allow the output to contain I2DEST or I1DEST as doing
1440    so would produce an insn that is not equivalent to the original insns.
1441
1442    Consider:
1443
1444          (set (reg:DI 101) (reg:DI 100))
1445          (set (subreg:SI (reg:DI 101) 0) <foo>)
1446
1447    This is NOT equivalent to:
1448
1449          (parallel [(set (subreg:SI (reg:DI 100) 0) <foo>)
1450                     (set (reg:DI 101) (reg:DI 100))])
1451
1452    Not only does this modify 100 (in which case it might still be valid
1453    if 100 were dead in I2), it sets 101 to the ORIGINAL value of 100.
1454
1455    We can also run into a problem if I2 sets a register that I1
1456    uses and I1 gets directly substituted into I3 (not via I2).  In that
1457    case, we would be getting the wrong value of I2DEST into I3, so we
1458    must reject the combination.  This case occurs when I2 and I1 both
1459    feed into I3, rather than when I1 feeds into I2, which feeds into I3.
1460    If I1_NOT_IN_SRC is nonzero, it means that finding I1 in the source
1461    of a SET must prevent combination from occurring.
1462
1463    Before doing the above check, we first try to expand a field assignment
1464    into a set of logical operations.
1465
1466    If PI3_DEST_KILLED is nonzero, it is a pointer to a location in which
1467    we place a register that is both set and used within I3.  If more than one
1468    such register is detected, we fail.
1469
1470    Return 1 if the combination is valid, zero otherwise.  */
1471
1472 static int
1473 combinable_i3pat (rtx i3, rtx *loc, rtx i2dest, rtx i1dest,
1474                   int i1_not_in_src, rtx *pi3dest_killed)
1475 {
1476   rtx x = *loc;
1477
1478   if (GET_CODE (x) == SET)
1479     {
1480       rtx set = x ;
1481       rtx dest = SET_DEST (set);
1482       rtx src = SET_SRC (set);
1483       rtx inner_dest = dest;
1484       rtx subdest;
1485
1486       while (GET_CODE (inner_dest) == STRICT_LOW_PART
1487              || GET_CODE (inner_dest) == SUBREG
1488              || GET_CODE (inner_dest) == ZERO_EXTRACT)
1489         inner_dest = XEXP (inner_dest, 0);
1490
1491       /* Check for the case where I3 modifies its output, as discussed
1492          above.  We don't want to prevent pseudos from being combined
1493          into the address of a MEM, so only prevent the combination if
1494          i1 or i2 set the same MEM.  */
1495       if ((inner_dest != dest &&
1496            (!MEM_P (inner_dest)
1497             || rtx_equal_p (i2dest, inner_dest)
1498             || (i1dest && rtx_equal_p (i1dest, inner_dest)))
1499            && (reg_overlap_mentioned_p (i2dest, inner_dest)
1500                || (i1dest && reg_overlap_mentioned_p (i1dest, inner_dest))))
1501
1502           /* This is the same test done in can_combine_p except we can't test
1503              all_adjacent; we don't have to, since this instruction will stay
1504              in place, thus we are not considering increasing the lifetime of
1505              INNER_DEST.
1506
1507              Also, if this insn sets a function argument, combining it with
1508              something that might need a spill could clobber a previous
1509              function argument; the all_adjacent test in can_combine_p also
1510              checks this; here, we do a more specific test for this case.  */
1511
1512           || (REG_P (inner_dest)
1513               && REGNO (inner_dest) < FIRST_PSEUDO_REGISTER
1514               && (! HARD_REGNO_MODE_OK (REGNO (inner_dest),
1515                                         GET_MODE (inner_dest))))
1516           || (i1_not_in_src && reg_overlap_mentioned_p (i1dest, src)))
1517         return 0;
1518
1519       /* If DEST is used in I3, it is being killed in this insn, so
1520          record that for later.  We have to consider paradoxical
1521          subregs here, since they kill the whole register, but we
1522          ignore partial subregs, STRICT_LOW_PART, etc.
1523          Never add REG_DEAD notes for the FRAME_POINTER_REGNUM or the
1524          STACK_POINTER_REGNUM, since these are always considered to be
1525          live.  Similarly for ARG_POINTER_REGNUM if it is fixed.  */
1526       subdest = dest;
1527       if (GET_CODE (subdest) == SUBREG
1528           && (GET_MODE_SIZE (GET_MODE (subdest))
1529               >= GET_MODE_SIZE (GET_MODE (SUBREG_REG (subdest)))))
1530         subdest = SUBREG_REG (subdest);
1531       if (pi3dest_killed
1532           && REG_P (subdest)
1533           && reg_referenced_p (subdest, PATTERN (i3))
1534           && REGNO (subdest) != FRAME_POINTER_REGNUM
1535 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
1536           && REGNO (subdest) != HARD_FRAME_POINTER_REGNUM
1537 #endif
1538 #if ARG_POINTER_REGNUM != FRAME_POINTER_REGNUM
1539           && (REGNO (subdest) != ARG_POINTER_REGNUM
1540               || ! fixed_regs [REGNO (subdest)])
1541 #endif
1542           && REGNO (subdest) != STACK_POINTER_REGNUM)
1543         {
1544           if (*pi3dest_killed)
1545             return 0;
1546
1547           *pi3dest_killed = subdest;
1548         }
1549     }
1550
1551   else if (GET_CODE (x) == PARALLEL)
1552     {
1553       int i;
1554
1555       for (i = 0; i < XVECLEN (x, 0); i++)
1556         if (! combinable_i3pat (i3, &XVECEXP (x, 0, i), i2dest, i1dest,
1557                                 i1_not_in_src, pi3dest_killed))
1558           return 0;
1559     }
1560
1561   return 1;
1562 }
1563 \f
1564 /* Return 1 if X is an arithmetic expression that contains a multiplication
1565    and division.  We don't count multiplications by powers of two here.  */
1566
1567 static int
1568 contains_muldiv (rtx x)
1569 {
1570   switch (GET_CODE (x))
1571     {
1572     case MOD:  case DIV:  case UMOD:  case UDIV:
1573       return 1;
1574
1575     case MULT:
1576       return ! (GET_CODE (XEXP (x, 1)) == CONST_INT
1577                 && exact_log2 (INTVAL (XEXP (x, 1))) >= 0);
1578     default:
1579       if (BINARY_P (x))
1580         return contains_muldiv (XEXP (x, 0))
1581             || contains_muldiv (XEXP (x, 1));
1582
1583       if (UNARY_P (x))
1584         return contains_muldiv (XEXP (x, 0));
1585
1586       return 0;
1587     }
1588 }
1589 \f
1590 /* Determine whether INSN can be used in a combination.  Return nonzero if
1591    not.  This is used in try_combine to detect early some cases where we
1592    can't perform combinations.  */
1593
1594 static int
1595 cant_combine_insn_p (rtx insn)
1596 {
1597   rtx set;
1598   rtx src, dest;
1599
1600   /* If this isn't really an insn, we can't do anything.
1601      This can occur when flow deletes an insn that it has merged into an
1602      auto-increment address.  */
1603   if (! INSN_P (insn))
1604     return 1;
1605
1606   /* Never combine loads and stores involving hard regs that are likely
1607      to be spilled.  The register allocator can usually handle such
1608      reg-reg moves by tying.  If we allow the combiner to make
1609      substitutions of likely-spilled regs, reload might die.
1610      As an exception, we allow combinations involving fixed regs; these are
1611      not available to the register allocator so there's no risk involved.  */
1612
1613   set = single_set (insn);
1614   if (! set)
1615     return 0;
1616   src = SET_SRC (set);
1617   dest = SET_DEST (set);
1618   if (GET_CODE (src) == SUBREG)
1619     src = SUBREG_REG (src);
1620   if (GET_CODE (dest) == SUBREG)
1621     dest = SUBREG_REG (dest);
1622   if (REG_P (src) && REG_P (dest)
1623       && ((REGNO (src) < FIRST_PSEUDO_REGISTER
1624            && ! fixed_regs[REGNO (src)]
1625            && CLASS_LIKELY_SPILLED_P (REGNO_REG_CLASS (REGNO (src))))
1626           || (REGNO (dest) < FIRST_PSEUDO_REGISTER
1627               && ! fixed_regs[REGNO (dest)]
1628               && CLASS_LIKELY_SPILLED_P (REGNO_REG_CLASS (REGNO (dest))))))
1629     return 1;
1630
1631   return 0;
1632 }
1633
1634 struct likely_spilled_retval_info
1635 {
1636   unsigned regno, nregs;
1637   unsigned mask;
1638 };
1639
1640 /* Called via note_stores by likely_spilled_retval_p.  Remove from info->mask
1641    hard registers that are known to be written to / clobbered in full.  */
1642 static void
1643 likely_spilled_retval_1 (rtx x, rtx set, void *data)
1644 {
1645   struct likely_spilled_retval_info *info = data;
1646   unsigned regno, nregs;
1647   unsigned new_mask;
1648
1649   if (!REG_P (XEXP (set, 0)))
1650     return;
1651   regno = REGNO (x);
1652   if (regno >= info->regno + info->nregs)
1653     return;
1654   nregs = hard_regno_nregs[regno][GET_MODE (x)];
1655   if (regno + nregs <= info->regno)
1656     return;
1657   new_mask = (2U << (nregs - 1)) - 1;
1658   if (regno < info->regno)
1659     new_mask >>= info->regno - regno;
1660   else
1661     new_mask <<= regno - info->regno;
1662   info->mask &= new_mask;
1663 }
1664
1665 /* Return nonzero iff part of the return value is live during INSN, and
1666    it is likely spilled.  This can happen when more than one insn is needed
1667    to copy the return value, e.g. when we consider to combine into the
1668    second copy insn for a complex value.  */
1669
1670 static int
1671 likely_spilled_retval_p (rtx insn)
1672 {
1673   rtx use = BB_END (this_basic_block);
1674   rtx reg, p;
1675   unsigned regno, nregs;
1676   /* We assume here that no machine mode needs more than
1677      32 hard registers when the value overlaps with a register
1678      for which FUNCTION_VALUE_REGNO_P is true.  */
1679   unsigned mask;
1680   struct likely_spilled_retval_info info;
1681
1682   if (!NONJUMP_INSN_P (use) || GET_CODE (PATTERN (use)) != USE || insn == use)
1683     return 0;
1684   reg = XEXP (PATTERN (use), 0);
1685   if (!REG_P (reg) || !FUNCTION_VALUE_REGNO_P (REGNO (reg)))
1686     return 0;
1687   regno = REGNO (reg);
1688   nregs = hard_regno_nregs[regno][GET_MODE (reg)];
1689   if (nregs == 1)
1690     return 0;
1691   mask = (2U << (nregs - 1)) - 1;
1692
1693   /* Disregard parts of the return value that are set later.  */
1694   info.regno = regno;
1695   info.nregs = nregs;
1696   info.mask = mask;
1697   for (p = PREV_INSN (use); info.mask && p != insn; p = PREV_INSN (p))
1698     note_stores (PATTERN (insn), likely_spilled_retval_1, &info);
1699   mask = info.mask;
1700
1701   /* Check if any of the (probably) live return value registers is
1702      likely spilled.  */
1703   nregs --;
1704   do
1705     {
1706       if ((mask & 1 << nregs)
1707           && CLASS_LIKELY_SPILLED_P (REGNO_REG_CLASS (regno + nregs)))
1708         return 1;
1709     } while (nregs--);
1710   return 0;
1711 }
1712
1713 /* Adjust INSN after we made a change to its destination.
1714
1715    Changing the destination can invalidate notes that say something about
1716    the results of the insn and a LOG_LINK pointing to the insn.  */
1717
1718 static void
1719 adjust_for_new_dest (rtx insn)
1720 {
1721   rtx *loc;
1722
1723   /* For notes, be conservative and simply remove them.  */
1724   loc = &REG_NOTES (insn);
1725   while (*loc)
1726     {
1727       enum reg_note kind = REG_NOTE_KIND (*loc);
1728       if (kind == REG_EQUAL || kind == REG_EQUIV)
1729         *loc = XEXP (*loc, 1);
1730       else
1731         loc = &XEXP (*loc, 1);
1732     }
1733
1734   /* The new insn will have a destination that was previously the destination
1735      of an insn just above it.  Call distribute_links to make a LOG_LINK from
1736      the next use of that destination.  */
1737   distribute_links (gen_rtx_INSN_LIST (VOIDmode, insn, NULL_RTX));
1738 }
1739
1740 /* Return TRUE if combine can reuse reg X in mode MODE.
1741    ADDED_SETS is nonzero if the original set is still required.  */
1742 static bool
1743 can_change_dest_mode (rtx x, int added_sets, enum machine_mode mode)
1744 {
1745   unsigned int regno;
1746
1747   if (!REG_P(x))
1748     return false;
1749
1750   regno = REGNO (x);
1751   /* Allow hard registers if the new mode is legal, and occupies no more
1752      registers than the old mode.  */
1753   if (regno < FIRST_PSEUDO_REGISTER)
1754     return (HARD_REGNO_MODE_OK (regno, mode)
1755             && (hard_regno_nregs[regno][GET_MODE (x)]
1756                 >= hard_regno_nregs[regno][mode]));
1757
1758   /* Or a pseudo that is only used once.  */
1759   return (REG_N_SETS (regno) == 1 && !added_sets
1760           && !REG_USERVAR_P (x));
1761 }
1762
1763
1764 /* Check whether X, the destination of a set, refers to part of
1765    the register specified by REG.  */
1766
1767 static bool
1768 reg_subword_p (rtx x, rtx reg)
1769 {
1770   /* Check that reg is an integer mode register.  */
1771   if (!REG_P (reg) || GET_MODE_CLASS (GET_MODE (reg)) != MODE_INT)
1772     return false;
1773
1774   if (GET_CODE (x) == STRICT_LOW_PART
1775       || GET_CODE (x) == ZERO_EXTRACT)
1776     x = XEXP (x, 0);
1777
1778   return GET_CODE (x) == SUBREG
1779          && SUBREG_REG (x) == reg
1780          && GET_MODE_CLASS (GET_MODE (x)) == MODE_INT;
1781 }
1782
1783
1784 /* Try to combine the insns I1 and I2 into I3.
1785    Here I1 and I2 appear earlier than I3.
1786    I1 can be zero; then we combine just I2 into I3.
1787
1788    If we are combining three insns and the resulting insn is not recognized,
1789    try splitting it into two insns.  If that happens, I2 and I3 are retained
1790    and I1 is pseudo-deleted by turning it into a NOTE.  Otherwise, I1 and I2
1791    are pseudo-deleted.
1792
1793    Return 0 if the combination does not work.  Then nothing is changed.
1794    If we did the combination, return the insn at which combine should
1795    resume scanning.
1796
1797    Set NEW_DIRECT_JUMP_P to a nonzero value if try_combine creates a
1798    new direct jump instruction.  */
1799
1800 static rtx
1801 try_combine (rtx i3, rtx i2, rtx i1, int *new_direct_jump_p)
1802 {
1803   /* New patterns for I3 and I2, respectively.  */
1804   rtx newpat, newi2pat = 0;
1805   rtvec newpat_vec_with_clobbers = 0;
1806   int substed_i2 = 0, substed_i1 = 0;
1807   /* Indicates need to preserve SET in I1 or I2 in I3 if it is not dead.  */
1808   int added_sets_1, added_sets_2;
1809   /* Total number of SETs to put into I3.  */
1810   int total_sets;
1811   /* Nonzero if I2's body now appears in I3.  */
1812   int i2_is_used;
1813   /* INSN_CODEs for new I3, new I2, and user of condition code.  */
1814   int insn_code_number, i2_code_number = 0, other_code_number = 0;
1815   /* Contains I3 if the destination of I3 is used in its source, which means
1816      that the old life of I3 is being killed.  If that usage is placed into
1817      I2 and not in I3, a REG_DEAD note must be made.  */
1818   rtx i3dest_killed = 0;
1819   /* SET_DEST and SET_SRC of I2 and I1.  */
1820   rtx i2dest, i2src, i1dest = 0, i1src = 0;
1821   /* PATTERN (I2), or a copy of it in certain cases.  */
1822   rtx i2pat;
1823   /* Indicates if I2DEST or I1DEST is in I2SRC or I1_SRC.  */
1824   int i2dest_in_i2src = 0, i1dest_in_i1src = 0, i2dest_in_i1src = 0;
1825   int i2dest_killed = 0, i1dest_killed = 0;
1826   int i1_feeds_i3 = 0;
1827   /* Notes that must be added to REG_NOTES in I3 and I2.  */
1828   rtx new_i3_notes, new_i2_notes;
1829   /* Notes that we substituted I3 into I2 instead of the normal case.  */
1830   int i3_subst_into_i2 = 0;
1831   /* Notes that I1, I2 or I3 is a MULT operation.  */
1832   int have_mult = 0;
1833   int swap_i2i3 = 0;
1834
1835   int maxreg;
1836   rtx temp;
1837   rtx link;
1838   int i;
1839
1840   /* Exit early if one of the insns involved can't be used for
1841      combinations.  */
1842   if (cant_combine_insn_p (i3)
1843       || cant_combine_insn_p (i2)
1844       || (i1 && cant_combine_insn_p (i1))
1845       || likely_spilled_retval_p (i3)
1846       /* We also can't do anything if I3 has a
1847          REG_LIBCALL note since we don't want to disrupt the contiguity of a
1848          libcall.  */
1849 #if 0
1850       /* ??? This gives worse code, and appears to be unnecessary, since no
1851          pass after flow uses REG_LIBCALL/REG_RETVAL notes.  */
1852       || find_reg_note (i3, REG_LIBCALL, NULL_RTX)
1853 #endif
1854       )
1855     return 0;
1856
1857   combine_attempts++;
1858   undobuf.other_insn = 0;
1859
1860   /* Reset the hard register usage information.  */
1861   CLEAR_HARD_REG_SET (newpat_used_regs);
1862
1863   /* If I1 and I2 both feed I3, they can be in any order.  To simplify the
1864      code below, set I1 to be the earlier of the two insns.  */
1865   if (i1 && INSN_CUID (i1) > INSN_CUID (i2))
1866     temp = i1, i1 = i2, i2 = temp;
1867
1868   added_links_insn = 0;
1869
1870   /* First check for one important special-case that the code below will
1871      not handle.  Namely, the case where I1 is zero, I2 is a PARALLEL
1872      and I3 is a SET whose SET_SRC is a SET_DEST in I2.  In that case,
1873      we may be able to replace that destination with the destination of I3.
1874      This occurs in the common code where we compute both a quotient and
1875      remainder into a structure, in which case we want to do the computation
1876      directly into the structure to avoid register-register copies.
1877
1878      Note that this case handles both multiple sets in I2 and also
1879      cases where I2 has a number of CLOBBER or PARALLELs.
1880
1881      We make very conservative checks below and only try to handle the
1882      most common cases of this.  For example, we only handle the case
1883      where I2 and I3 are adjacent to avoid making difficult register
1884      usage tests.  */
1885
1886   if (i1 == 0 && NONJUMP_INSN_P (i3) && GET_CODE (PATTERN (i3)) == SET
1887       && REG_P (SET_SRC (PATTERN (i3)))
1888       && REGNO (SET_SRC (PATTERN (i3))) >= FIRST_PSEUDO_REGISTER
1889       && find_reg_note (i3, REG_DEAD, SET_SRC (PATTERN (i3)))
1890       && GET_CODE (PATTERN (i2)) == PARALLEL
1891       && ! side_effects_p (SET_DEST (PATTERN (i3)))
1892       /* If the dest of I3 is a ZERO_EXTRACT or STRICT_LOW_PART, the code
1893          below would need to check what is inside (and reg_overlap_mentioned_p
1894          doesn't support those codes anyway).  Don't allow those destinations;
1895          the resulting insn isn't likely to be recognized anyway.  */
1896       && GET_CODE (SET_DEST (PATTERN (i3))) != ZERO_EXTRACT
1897       && GET_CODE (SET_DEST (PATTERN (i3))) != STRICT_LOW_PART
1898       && ! reg_overlap_mentioned_p (SET_SRC (PATTERN (i3)),
1899                                     SET_DEST (PATTERN (i3)))
1900       && next_real_insn (i2) == i3)
1901     {
1902       rtx p2 = PATTERN (i2);
1903
1904       /* Make sure that the destination of I3,
1905          which we are going to substitute into one output of I2,
1906          is not used within another output of I2.  We must avoid making this:
1907          (parallel [(set (mem (reg 69)) ...)
1908                     (set (reg 69) ...)])
1909          which is not well-defined as to order of actions.
1910          (Besides, reload can't handle output reloads for this.)
1911
1912          The problem can also happen if the dest of I3 is a memory ref,
1913          if another dest in I2 is an indirect memory ref.  */
1914       for (i = 0; i < XVECLEN (p2, 0); i++)
1915         if ((GET_CODE (XVECEXP (p2, 0, i)) == SET
1916              || GET_CODE (XVECEXP (p2, 0, i)) == CLOBBER)
1917             && reg_overlap_mentioned_p (SET_DEST (PATTERN (i3)),
1918                                         SET_DEST (XVECEXP (p2, 0, i))))
1919           break;
1920
1921       if (i == XVECLEN (p2, 0))
1922         for (i = 0; i < XVECLEN (p2, 0); i++)
1923           if ((GET_CODE (XVECEXP (p2, 0, i)) == SET
1924                || GET_CODE (XVECEXP (p2, 0, i)) == CLOBBER)
1925               && SET_DEST (XVECEXP (p2, 0, i)) == SET_SRC (PATTERN (i3)))
1926             {
1927               combine_merges++;
1928
1929               subst_insn = i3;
1930               subst_low_cuid = INSN_CUID (i2);
1931
1932               added_sets_2 = added_sets_1 = 0;
1933               i2dest = SET_SRC (PATTERN (i3));
1934               i2dest_killed = dead_or_set_p (i2, i2dest);
1935
1936               /* Replace the dest in I2 with our dest and make the resulting
1937                  insn the new pattern for I3.  Then skip to where we
1938                  validate the pattern.  Everything was set up above.  */
1939               SUBST (SET_DEST (XVECEXP (p2, 0, i)),
1940                      SET_DEST (PATTERN (i3)));
1941
1942               newpat = p2;
1943               i3_subst_into_i2 = 1;
1944               goto validate_replacement;
1945             }
1946     }
1947
1948   /* If I2 is setting a pseudo to a constant and I3 is setting some
1949      sub-part of it to another constant, merge them by making a new
1950      constant.  */
1951   if (i1 == 0
1952       && (temp = single_set (i2)) != 0
1953       && (GET_CODE (SET_SRC (temp)) == CONST_INT
1954           || GET_CODE (SET_SRC (temp)) == CONST_DOUBLE)
1955       && GET_CODE (PATTERN (i3)) == SET
1956       && (GET_CODE (SET_SRC (PATTERN (i3))) == CONST_INT
1957           || GET_CODE (SET_SRC (PATTERN (i3))) == CONST_DOUBLE)
1958       && reg_subword_p (SET_DEST (PATTERN (i3)), SET_DEST (temp)))
1959     {
1960       rtx dest = SET_DEST (PATTERN (i3));
1961       int offset = -1;
1962       int width = 0;
1963
1964       if (GET_CODE (dest) == ZERO_EXTRACT)
1965         {
1966           if (GET_CODE (XEXP (dest, 1)) == CONST_INT
1967               && GET_CODE (XEXP (dest, 2)) == CONST_INT)
1968             {
1969               width = INTVAL (XEXP (dest, 1));
1970               offset = INTVAL (XEXP (dest, 2));
1971               dest = XEXP (dest, 0);
1972               if (BITS_BIG_ENDIAN)
1973                 offset = GET_MODE_BITSIZE (GET_MODE (dest)) - width - offset;
1974             }
1975         }
1976       else
1977         {
1978           if (GET_CODE (dest) == STRICT_LOW_PART)
1979             dest = XEXP (dest, 0);
1980           width = GET_MODE_BITSIZE (GET_MODE (dest));
1981           offset = 0;
1982         }
1983
1984       if (offset >= 0)
1985         {
1986           /* If this is the low part, we're done.  */
1987           if (subreg_lowpart_p (dest))
1988             ;
1989           /* Handle the case where inner is twice the size of outer.  */
1990           else if (GET_MODE_BITSIZE (GET_MODE (SET_DEST (temp)))
1991                    == 2 * GET_MODE_BITSIZE (GET_MODE (dest)))
1992             offset += GET_MODE_BITSIZE (GET_MODE (dest));
1993           /* Otherwise give up for now.  */
1994           else
1995             offset = -1;
1996         }
1997
1998       if (offset >= 0)
1999         {
2000           HOST_WIDE_INT mhi, ohi, ihi;
2001           HOST_WIDE_INT mlo, olo, ilo;
2002           rtx inner = SET_SRC (PATTERN (i3));
2003           rtx outer = SET_SRC (temp);
2004
2005           if (GET_CODE (outer) == CONST_INT)
2006             {
2007               olo = INTVAL (outer);
2008               ohi = olo < 0 ? -1 : 0;
2009             }
2010           else
2011             {
2012               olo = CONST_DOUBLE_LOW (outer);
2013               ohi = CONST_DOUBLE_HIGH (outer);
2014             }
2015
2016           if (GET_CODE (inner) == CONST_INT)
2017             {
2018               ilo = INTVAL (inner);
2019               ihi = ilo < 0 ? -1 : 0;
2020             }
2021           else
2022             {
2023               ilo = CONST_DOUBLE_LOW (inner);
2024               ihi = CONST_DOUBLE_HIGH (inner);
2025             }
2026
2027           if (width < HOST_BITS_PER_WIDE_INT)
2028             {
2029               mlo = ((unsigned HOST_WIDE_INT) 1 << width) - 1;
2030               mhi = 0;
2031             }
2032           else if (width < HOST_BITS_PER_WIDE_INT * 2)
2033             {
2034               mhi = ((unsigned HOST_WIDE_INT) 1
2035                      << (width - HOST_BITS_PER_WIDE_INT)) - 1;
2036               mlo = -1;
2037             }
2038           else
2039             {
2040               mlo = -1;
2041               mhi = -1;
2042             }
2043
2044           ilo &= mlo;
2045           ihi &= mhi;
2046
2047           if (offset >= HOST_BITS_PER_WIDE_INT)
2048             {
2049               mhi = mlo << (offset - HOST_BITS_PER_WIDE_INT);
2050               mlo = 0;
2051               ihi = ilo << (offset - HOST_BITS_PER_WIDE_INT);
2052               ilo = 0;
2053             }
2054           else if (offset > 0)
2055             {
2056               mhi = (mhi << offset) | ((unsigned HOST_WIDE_INT) mlo
2057                                        >> (HOST_BITS_PER_WIDE_INT - offset));
2058               mlo = mlo << offset;
2059               ihi = (ihi << offset) | ((unsigned HOST_WIDE_INT) ilo
2060                                        >> (HOST_BITS_PER_WIDE_INT - offset));
2061               ilo = ilo << offset;
2062             }
2063
2064           olo = (olo & ~mlo) | ilo;
2065           ohi = (ohi & ~mhi) | ihi;
2066
2067           combine_merges++;
2068           subst_insn = i3;
2069           subst_low_cuid = INSN_CUID (i2);
2070           added_sets_2 = added_sets_1 = 0;
2071           i2dest = SET_DEST (temp);
2072           i2dest_killed = dead_or_set_p (i2, i2dest);
2073
2074           SUBST (SET_SRC (temp),
2075                  immed_double_const (olo, ohi, GET_MODE (SET_DEST (temp))));
2076
2077           newpat = PATTERN (i2);
2078           goto validate_replacement;
2079         }
2080     }
2081
2082 #ifndef HAVE_cc0
2083   /* If we have no I1 and I2 looks like:
2084         (parallel [(set (reg:CC X) (compare:CC OP (const_int 0)))
2085                    (set Y OP)])
2086      make up a dummy I1 that is
2087         (set Y OP)
2088      and change I2 to be
2089         (set (reg:CC X) (compare:CC Y (const_int 0)))
2090
2091      (We can ignore any trailing CLOBBERs.)
2092
2093      This undoes a previous combination and allows us to match a branch-and-
2094      decrement insn.  */
2095
2096   if (i1 == 0 && GET_CODE (PATTERN (i2)) == PARALLEL
2097       && XVECLEN (PATTERN (i2), 0) >= 2
2098       && GET_CODE (XVECEXP (PATTERN (i2), 0, 0)) == SET
2099       && (GET_MODE_CLASS (GET_MODE (SET_DEST (XVECEXP (PATTERN (i2), 0, 0))))
2100           == MODE_CC)
2101       && GET_CODE (SET_SRC (XVECEXP (PATTERN (i2), 0, 0))) == COMPARE
2102       && XEXP (SET_SRC (XVECEXP (PATTERN (i2), 0, 0)), 1) == const0_rtx
2103       && GET_CODE (XVECEXP (PATTERN (i2), 0, 1)) == SET
2104       && REG_P (SET_DEST (XVECEXP (PATTERN (i2), 0, 1)))
2105       && rtx_equal_p (XEXP (SET_SRC (XVECEXP (PATTERN (i2), 0, 0)), 0),
2106                       SET_SRC (XVECEXP (PATTERN (i2), 0, 1))))
2107     {
2108       for (i = XVECLEN (PATTERN (i2), 0) - 1; i >= 2; i--)
2109         if (GET_CODE (XVECEXP (PATTERN (i2), 0, i)) != CLOBBER)
2110           break;
2111
2112       if (i == 1)
2113         {
2114           /* We make I1 with the same INSN_UID as I2.  This gives it
2115              the same INSN_CUID for value tracking.  Our fake I1 will
2116              never appear in the insn stream so giving it the same INSN_UID
2117              as I2 will not cause a problem.  */
2118
2119           i1 = gen_rtx_INSN (VOIDmode, INSN_UID (i2), NULL_RTX, i2,
2120                              BLOCK_FOR_INSN (i2), INSN_LOCATOR (i2),
2121                              XVECEXP (PATTERN (i2), 0, 1), -1, NULL_RTX,
2122                              NULL_RTX);
2123
2124           SUBST (PATTERN (i2), XVECEXP (PATTERN (i2), 0, 0));
2125           SUBST (XEXP (SET_SRC (PATTERN (i2)), 0),
2126                  SET_DEST (PATTERN (i1)));
2127         }
2128     }
2129 #endif
2130
2131   /* Verify that I2 and I1 are valid for combining.  */
2132   if (! can_combine_p (i2, i3, i1, NULL_RTX, &i2dest, &i2src)
2133       || (i1 && ! can_combine_p (i1, i3, NULL_RTX, i2, &i1dest, &i1src)))
2134     {
2135       undo_all ();
2136       return 0;
2137     }
2138
2139   /* Record whether I2DEST is used in I2SRC and similarly for the other
2140      cases.  Knowing this will help in register status updating below.  */
2141   i2dest_in_i2src = reg_overlap_mentioned_p (i2dest, i2src);
2142   i1dest_in_i1src = i1 && reg_overlap_mentioned_p (i1dest, i1src);
2143   i2dest_in_i1src = i1 && reg_overlap_mentioned_p (i2dest, i1src);
2144   i2dest_killed = dead_or_set_p (i2, i2dest);
2145   i1dest_killed = i1 && dead_or_set_p (i1, i1dest);
2146
2147   /* See if I1 directly feeds into I3.  It does if I1DEST is not used
2148      in I2SRC.  */
2149   i1_feeds_i3 = i1 && ! reg_overlap_mentioned_p (i1dest, i2src);
2150
2151   /* Ensure that I3's pattern can be the destination of combines.  */
2152   if (! combinable_i3pat (i3, &PATTERN (i3), i2dest, i1dest,
2153                           i1 && i2dest_in_i1src && i1_feeds_i3,
2154                           &i3dest_killed))
2155     {
2156       undo_all ();
2157       return 0;
2158     }
2159
2160   /* See if any of the insns is a MULT operation.  Unless one is, we will
2161      reject a combination that is, since it must be slower.  Be conservative
2162      here.  */
2163   if (GET_CODE (i2src) == MULT
2164       || (i1 != 0 && GET_CODE (i1src) == MULT)
2165       || (GET_CODE (PATTERN (i3)) == SET
2166           && GET_CODE (SET_SRC (PATTERN (i3))) == MULT))
2167     have_mult = 1;
2168
2169   /* If I3 has an inc, then give up if I1 or I2 uses the reg that is inc'd.
2170      We used to do this EXCEPT in one case: I3 has a post-inc in an
2171      output operand.  However, that exception can give rise to insns like
2172         mov r3,(r3)+
2173      which is a famous insn on the PDP-11 where the value of r3 used as the
2174      source was model-dependent.  Avoid this sort of thing.  */
2175
2176 #if 0
2177   if (!(GET_CODE (PATTERN (i3)) == SET
2178         && REG_P (SET_SRC (PATTERN (i3)))
2179         && MEM_P (SET_DEST (PATTERN (i3)))
2180         && (GET_CODE (XEXP (SET_DEST (PATTERN (i3)), 0)) == POST_INC
2181             || GET_CODE (XEXP (SET_DEST (PATTERN (i3)), 0)) == POST_DEC)))
2182     /* It's not the exception.  */
2183 #endif
2184 #ifdef AUTO_INC_DEC
2185     for (link = REG_NOTES (i3); link; link = XEXP (link, 1))
2186       if (REG_NOTE_KIND (link) == REG_INC
2187           && (reg_overlap_mentioned_p (XEXP (link, 0), PATTERN (i2))
2188               || (i1 != 0
2189                   && reg_overlap_mentioned_p (XEXP (link, 0), PATTERN (i1)))))
2190         {
2191           undo_all ();
2192           return 0;
2193         }
2194 #endif
2195
2196   /* See if the SETs in I1 or I2 need to be kept around in the merged
2197      instruction: whenever the value set there is still needed past I3.
2198      For the SETs in I2, this is easy: we see if I2DEST dies or is set in I3.
2199
2200      For the SET in I1, we have two cases:  If I1 and I2 independently
2201      feed into I3, the set in I1 needs to be kept around if I1DEST dies
2202      or is set in I3.  Otherwise (if I1 feeds I2 which feeds I3), the set
2203      in I1 needs to be kept around unless I1DEST dies or is set in either
2204      I2 or I3.  We can distinguish these cases by seeing if I2SRC mentions
2205      I1DEST.  If so, we know I1 feeds into I2.  */
2206
2207   added_sets_2 = ! dead_or_set_p (i3, i2dest);
2208
2209   added_sets_1
2210     = i1 && ! (i1_feeds_i3 ? dead_or_set_p (i3, i1dest)
2211                : (dead_or_set_p (i3, i1dest) || dead_or_set_p (i2, i1dest)));
2212
2213   /* If the set in I2 needs to be kept around, we must make a copy of
2214      PATTERN (I2), so that when we substitute I1SRC for I1DEST in
2215      PATTERN (I2), we are only substituting for the original I1DEST, not into
2216      an already-substituted copy.  This also prevents making self-referential
2217      rtx.  If I2 is a PARALLEL, we just need the piece that assigns I2SRC to
2218      I2DEST.  */
2219
2220   i2pat = (GET_CODE (PATTERN (i2)) == PARALLEL
2221            ? gen_rtx_SET (VOIDmode, i2dest, i2src)
2222            : PATTERN (i2));
2223
2224   if (added_sets_2)
2225     i2pat = copy_rtx (i2pat);
2226
2227   combine_merges++;
2228
2229   /* Substitute in the latest insn for the regs set by the earlier ones.  */
2230
2231   maxreg = max_reg_num ();
2232
2233   subst_insn = i3;
2234
2235 #ifndef HAVE_cc0
2236   /* Many machines that don't use CC0 have insns that can both perform an
2237      arithmetic operation and set the condition code.  These operations will
2238      be represented as a PARALLEL with the first element of the vector
2239      being a COMPARE of an arithmetic operation with the constant zero.
2240      The second element of the vector will set some pseudo to the result
2241      of the same arithmetic operation.  If we simplify the COMPARE, we won't
2242      match such a pattern and so will generate an extra insn.   Here we test
2243      for this case, where both the comparison and the operation result are
2244      needed, and make the PARALLEL by just replacing I2DEST in I3SRC with
2245      I2SRC.  Later we will make the PARALLEL that contains I2.  */
2246
2247   if (i1 == 0 && added_sets_2 && GET_CODE (PATTERN (i3)) == SET
2248       && GET_CODE (SET_SRC (PATTERN (i3))) == COMPARE
2249       && XEXP (SET_SRC (PATTERN (i3)), 1) == const0_rtx
2250       && rtx_equal_p (XEXP (SET_SRC (PATTERN (i3)), 0), i2dest))
2251     {
2252 #ifdef SELECT_CC_MODE
2253       rtx *cc_use;
2254       enum machine_mode compare_mode;
2255 #endif
2256
2257       newpat = PATTERN (i3);
2258       SUBST (XEXP (SET_SRC (newpat), 0), i2src);
2259
2260       i2_is_used = 1;
2261
2262 #ifdef SELECT_CC_MODE
2263       /* See if a COMPARE with the operand we substituted in should be done
2264          with the mode that is currently being used.  If not, do the same
2265          processing we do in `subst' for a SET; namely, if the destination
2266          is used only once, try to replace it with a register of the proper
2267          mode and also replace the COMPARE.  */
2268       if (undobuf.other_insn == 0
2269           && (cc_use = find_single_use (SET_DEST (newpat), i3,
2270                                         &undobuf.other_insn))
2271           && ((compare_mode = SELECT_CC_MODE (GET_CODE (*cc_use),
2272                                               i2src, const0_rtx))
2273               != GET_MODE (SET_DEST (newpat))))
2274         {
2275           if (can_change_dest_mode(SET_DEST (newpat), added_sets_2,
2276                                    compare_mode))
2277             {
2278               unsigned int regno = REGNO (SET_DEST (newpat));
2279               rtx new_dest;
2280
2281               if (regno < FIRST_PSEUDO_REGISTER)
2282                 new_dest = gen_rtx_REG (compare_mode, regno);
2283               else
2284                 {
2285                   SUBST_MODE (regno_reg_rtx[regno], compare_mode);
2286                   new_dest = regno_reg_rtx[regno];
2287                 }
2288
2289               SUBST (SET_DEST (newpat), new_dest);
2290               SUBST (XEXP (*cc_use, 0), new_dest);
2291               SUBST (SET_SRC (newpat),
2292                      gen_rtx_COMPARE (compare_mode, i2src, const0_rtx));
2293             }
2294           else
2295             undobuf.other_insn = 0;
2296         }
2297 #endif
2298     }
2299   else
2300 #endif
2301     {
2302       /* It is possible that the source of I2 or I1 may be performing
2303          an unneeded operation, such as a ZERO_EXTEND of something
2304          that is known to have the high part zero.  Handle that case
2305          by letting subst look at the innermost one of them.
2306
2307          Another way to do this would be to have a function that tries
2308          to simplify a single insn instead of merging two or more
2309          insns.  We don't do this because of the potential of infinite
2310          loops and because of the potential extra memory required.
2311          However, doing it the way we are is a bit of a kludge and
2312          doesn't catch all cases.
2313
2314          But only do this if -fexpensive-optimizations since it slows
2315          things down and doesn't usually win.
2316
2317          This is not done in the COMPARE case above because the
2318          unmodified I2PAT is used in the PARALLEL and so a pattern
2319          with a modified I2SRC would not match.  */
2320
2321       if (flag_expensive_optimizations)
2322         {
2323           /* Pass pc_rtx so no substitutions are done, just
2324              simplifications.  */
2325           if (i1)
2326             {
2327               subst_low_cuid = INSN_CUID (i1);
2328               i1src = subst (i1src, pc_rtx, pc_rtx, 0, 0);
2329             }
2330           else
2331             {
2332               subst_low_cuid = INSN_CUID (i2);
2333               i2src = subst (i2src, pc_rtx, pc_rtx, 0, 0);
2334             }
2335         }
2336
2337       n_occurrences = 0;                /* `subst' counts here */
2338
2339       /* If I1 feeds into I2 (not into I3) and I1DEST is in I1SRC, we
2340          need to make a unique copy of I2SRC each time we substitute it
2341          to avoid self-referential rtl.  */
2342
2343       subst_low_cuid = INSN_CUID (i2);
2344       newpat = subst (PATTERN (i3), i2dest, i2src, 0,
2345                       ! i1_feeds_i3 && i1dest_in_i1src);
2346       substed_i2 = 1;
2347
2348       /* Record whether i2's body now appears within i3's body.  */
2349       i2_is_used = n_occurrences;
2350     }
2351
2352   /* If we already got a failure, don't try to do more.  Otherwise,
2353      try to substitute in I1 if we have it.  */
2354
2355   if (i1 && GET_CODE (newpat) != CLOBBER)
2356     {
2357       /* Before we can do this substitution, we must redo the test done
2358          above (see detailed comments there) that ensures  that I1DEST
2359          isn't mentioned in any SETs in NEWPAT that are field assignments.  */
2360
2361       if (! combinable_i3pat (NULL_RTX, &newpat, i1dest, NULL_RTX,
2362                               0, (rtx*) 0))
2363         {
2364           undo_all ();
2365           return 0;
2366         }
2367
2368       n_occurrences = 0;
2369       subst_low_cuid = INSN_CUID (i1);
2370       newpat = subst (newpat, i1dest, i1src, 0, 0);
2371       substed_i1 = 1;
2372     }
2373
2374   /* Fail if an autoincrement side-effect has been duplicated.  Be careful
2375      to count all the ways that I2SRC and I1SRC can be used.  */
2376   if ((FIND_REG_INC_NOTE (i2, NULL_RTX) != 0
2377        && i2_is_used + added_sets_2 > 1)
2378       || (i1 != 0 && FIND_REG_INC_NOTE (i1, NULL_RTX) != 0
2379           && (n_occurrences + added_sets_1 + (added_sets_2 && ! i1_feeds_i3)
2380               > 1))
2381       /* Fail if we tried to make a new register.  */
2382       || max_reg_num () != maxreg
2383       /* Fail if we couldn't do something and have a CLOBBER.  */
2384       || GET_CODE (newpat) == CLOBBER
2385       /* Fail if this new pattern is a MULT and we didn't have one before
2386          at the outer level.  */
2387       || (GET_CODE (newpat) == SET && GET_CODE (SET_SRC (newpat)) == MULT
2388           && ! have_mult))
2389     {
2390       undo_all ();
2391       return 0;
2392     }
2393
2394   /* If the actions of the earlier insns must be kept
2395      in addition to substituting them into the latest one,
2396      we must make a new PARALLEL for the latest insn
2397      to hold additional the SETs.  */
2398
2399   if (added_sets_1 || added_sets_2)
2400     {
2401       combine_extras++;
2402
2403       if (GET_CODE (newpat) == PARALLEL)
2404         {
2405           rtvec old = XVEC (newpat, 0);
2406           total_sets = XVECLEN (newpat, 0) + added_sets_1 + added_sets_2;
2407           newpat = gen_rtx_PARALLEL (VOIDmode, rtvec_alloc (total_sets));
2408           memcpy (XVEC (newpat, 0)->elem, &old->elem[0],
2409                   sizeof (old->elem[0]) * old->num_elem);
2410         }
2411       else
2412         {
2413           rtx old = newpat;
2414           total_sets = 1 + added_sets_1 + added_sets_2;
2415           newpat = gen_rtx_PARALLEL (VOIDmode, rtvec_alloc (total_sets));
2416           XVECEXP (newpat, 0, 0) = old;
2417         }
2418
2419       if (added_sets_1)
2420         XVECEXP (newpat, 0, --total_sets)
2421           = (GET_CODE (PATTERN (i1)) == PARALLEL
2422              ? gen_rtx_SET (VOIDmode, i1dest, i1src) : PATTERN (i1));
2423
2424       if (added_sets_2)
2425         {
2426           /* If there is no I1, use I2's body as is.  We used to also not do
2427              the subst call below if I2 was substituted into I3,
2428              but that could lose a simplification.  */
2429           if (i1 == 0)
2430             XVECEXP (newpat, 0, --total_sets) = i2pat;
2431           else
2432             /* See comment where i2pat is assigned.  */
2433             XVECEXP (newpat, 0, --total_sets)
2434               = subst (i2pat, i1dest, i1src, 0, 0);
2435         }
2436     }
2437
2438   /* We come here when we are replacing a destination in I2 with the
2439      destination of I3.  */
2440  validate_replacement:
2441
2442   /* Note which hard regs this insn has as inputs.  */
2443   mark_used_regs_combine (newpat);
2444
2445   /* If recog_for_combine fails, it strips existing clobbers.  If we'll
2446      consider splitting this pattern, we might need these clobbers.  */
2447   if (i1 && GET_CODE (newpat) == PARALLEL
2448       && GET_CODE (XVECEXP (newpat, 0, XVECLEN (newpat, 0) - 1)) == CLOBBER)
2449     {
2450       int len = XVECLEN (newpat, 0);
2451
2452       newpat_vec_with_clobbers = rtvec_alloc (len);
2453       for (i = 0; i < len; i++)
2454         RTVEC_ELT (newpat_vec_with_clobbers, i) = XVECEXP (newpat, 0, i);
2455     }
2456
2457   /* Is the result of combination a valid instruction?  */
2458   insn_code_number = recog_for_combine (&newpat, i3, &new_i3_notes);
2459
2460   /* If the result isn't valid, see if it is a PARALLEL of two SETs where
2461      the second SET's destination is a register that is unused and isn't
2462      marked as an instruction that might trap in an EH region.  In that case,
2463      we just need the first SET.   This can occur when simplifying a divmod
2464      insn.  We *must* test for this case here because the code below that
2465      splits two independent SETs doesn't handle this case correctly when it
2466      updates the register status.
2467
2468      It's pointless doing this if we originally had two sets, one from
2469      i3, and one from i2.  Combining then splitting the parallel results
2470      in the original i2 again plus an invalid insn (which we delete).
2471      The net effect is only to move instructions around, which makes
2472      debug info less accurate.
2473
2474      Also check the case where the first SET's destination is unused.
2475      That would not cause incorrect code, but does cause an unneeded
2476      insn to remain.  */
2477
2478   if (insn_code_number < 0
2479       && !(added_sets_2 && i1 == 0)
2480       && GET_CODE (newpat) == PARALLEL
2481       && XVECLEN (newpat, 0) == 2
2482       && GET_CODE (XVECEXP (newpat, 0, 0)) == SET
2483       && GET_CODE (XVECEXP (newpat, 0, 1)) == SET
2484       && asm_noperands (newpat) < 0)
2485     {
2486       rtx set0 = XVECEXP (newpat, 0, 0);
2487       rtx set1 = XVECEXP (newpat, 0, 1);
2488       rtx note;
2489
2490       if (((REG_P (SET_DEST (set1))
2491             && find_reg_note (i3, REG_UNUSED, SET_DEST (set1)))
2492            || (GET_CODE (SET_DEST (set1)) == SUBREG
2493                && find_reg_note (i3, REG_UNUSED, SUBREG_REG (SET_DEST (set1)))))
2494           && (!(note = find_reg_note (i3, REG_EH_REGION, NULL_RTX))
2495               || INTVAL (XEXP (note, 0)) <= 0)
2496           && ! side_effects_p (SET_SRC (set1)))
2497         {
2498           newpat = set0;
2499           insn_code_number = recog_for_combine (&newpat, i3, &new_i3_notes);
2500         }
2501
2502       else if (((REG_P (SET_DEST (set0))
2503                  && find_reg_note (i3, REG_UNUSED, SET_DEST (set0)))
2504                 || (GET_CODE (SET_DEST (set0)) == SUBREG
2505                     && find_reg_note (i3, REG_UNUSED,
2506                                       SUBREG_REG (SET_DEST (set0)))))
2507                && (!(note = find_reg_note (i3, REG_EH_REGION, NULL_RTX))
2508                    || INTVAL (XEXP (note, 0)) <= 0)
2509                && ! side_effects_p (SET_SRC (set0)))
2510         {
2511           newpat = set1;
2512           insn_code_number = recog_for_combine (&newpat, i3, &new_i3_notes);
2513
2514           if (insn_code_number >= 0)
2515             {
2516               /* If we will be able to accept this, we have made a
2517                  change to the destination of I3.  This requires us to
2518                  do a few adjustments.  */
2519
2520               PATTERN (i3) = newpat;
2521               adjust_for_new_dest (i3);
2522             }
2523         }
2524     }
2525
2526   /* If we were combining three insns and the result is a simple SET
2527      with no ASM_OPERANDS that wasn't recognized, try to split it into two
2528      insns.  There are two ways to do this.  It can be split using a
2529      machine-specific method (like when you have an addition of a large
2530      constant) or by combine in the function find_split_point.  */
2531
2532   if (i1 && insn_code_number < 0 && GET_CODE (newpat) == SET
2533       && asm_noperands (newpat) < 0)
2534     {
2535       rtx m_split, *split;
2536
2537       /* See if the MD file can split NEWPAT.  If it can't, see if letting it
2538          use I2DEST as a scratch register will help.  In the latter case,
2539          convert I2DEST to the mode of the source of NEWPAT if we can.  */
2540
2541       m_split = split_insns (newpat, i3);
2542
2543       /* We can only use I2DEST as a scratch reg if it doesn't overlap any
2544          inputs of NEWPAT.  */
2545
2546       /* ??? If I2DEST is not safe, and I1DEST exists, then it would be
2547          possible to try that as a scratch reg.  This would require adding
2548          more code to make it work though.  */
2549
2550       if (m_split == 0 && ! reg_overlap_mentioned_p (i2dest, newpat))
2551         {
2552           enum machine_mode new_mode = GET_MODE (SET_DEST (newpat));
2553
2554           /* First try to split using the original register as a
2555              scratch register.  */
2556           m_split = split_insns (gen_rtx_PARALLEL
2557                                  (VOIDmode,
2558                                   gen_rtvec (2, newpat,
2559                                              gen_rtx_CLOBBER (VOIDmode,
2560                                                               i2dest))),
2561                                  i3);
2562
2563           /* If that didn't work, try changing the mode of I2DEST if
2564              we can.  */
2565           if (m_split == 0
2566               && new_mode != GET_MODE (i2dest)
2567               && new_mode != VOIDmode
2568               && can_change_dest_mode (i2dest, added_sets_2, new_mode))
2569             {
2570               enum machine_mode old_mode = GET_MODE (i2dest);
2571               rtx ni2dest;
2572
2573               if (REGNO (i2dest) < FIRST_PSEUDO_REGISTER)
2574                 ni2dest = gen_rtx_REG (new_mode, REGNO (i2dest));
2575               else
2576                 {
2577                   SUBST_MODE (regno_reg_rtx[REGNO (i2dest)], new_mode);
2578                   ni2dest = regno_reg_rtx[REGNO (i2dest)];
2579                 }
2580
2581               m_split = split_insns (gen_rtx_PARALLEL
2582                                      (VOIDmode,
2583                                       gen_rtvec (2, newpat,
2584                                                  gen_rtx_CLOBBER (VOIDmode,
2585                                                                   ni2dest))),
2586                                      i3);
2587
2588               if (m_split == 0
2589                   && REGNO (i2dest) >= FIRST_PSEUDO_REGISTER)
2590                 {
2591                   struct undo *buf;
2592
2593                   PUT_MODE (regno_reg_rtx[REGNO (i2dest)], old_mode);
2594                   buf = undobuf.undos;
2595                   undobuf.undos = buf->next;
2596                   buf->next = undobuf.frees;
2597                   undobuf.frees = buf;
2598                 }
2599             }
2600         }
2601
2602       /* If recog_for_combine has discarded clobbers, try to use them
2603          again for the split.  */
2604       if (m_split == 0 && newpat_vec_with_clobbers)
2605         m_split
2606           = split_insns (gen_rtx_PARALLEL (VOIDmode,
2607                                            newpat_vec_with_clobbers), i3);
2608
2609       if (m_split && NEXT_INSN (m_split) == NULL_RTX)
2610         {
2611           m_split = PATTERN (m_split);
2612           insn_code_number = recog_for_combine (&m_split, i3, &new_i3_notes);
2613           if (insn_code_number >= 0)
2614             newpat = m_split;
2615         }
2616       else if (m_split && NEXT_INSN (NEXT_INSN (m_split)) == NULL_RTX
2617                && (next_real_insn (i2) == i3
2618                    || ! use_crosses_set_p (PATTERN (m_split), INSN_CUID (i2))))
2619         {
2620           rtx i2set, i3set;
2621           rtx newi3pat = PATTERN (NEXT_INSN (m_split));
2622           newi2pat = PATTERN (m_split);
2623
2624           i3set = single_set (NEXT_INSN (m_split));
2625           i2set = single_set (m_split);
2626
2627           i2_code_number = recog_for_combine (&newi2pat, i2, &new_i2_notes);
2628
2629           /* If I2 or I3 has multiple SETs, we won't know how to track
2630              register status, so don't use these insns.  If I2's destination
2631              is used between I2 and I3, we also can't use these insns.  */
2632
2633           if (i2_code_number >= 0 && i2set && i3set
2634               && (next_real_insn (i2) == i3
2635                   || ! reg_used_between_p (SET_DEST (i2set), i2, i3)))
2636             insn_code_number = recog_for_combine (&newi3pat, i3,
2637                                                   &new_i3_notes);
2638           if (insn_code_number >= 0)
2639             newpat = newi3pat;
2640
2641           /* It is possible that both insns now set the destination of I3.
2642              If so, we must show an extra use of it.  */
2643
2644           if (insn_code_number >= 0)
2645             {
2646               rtx new_i3_dest = SET_DEST (i3set);
2647               rtx new_i2_dest = SET_DEST (i2set);
2648
2649               while (GET_CODE (new_i3_dest) == ZERO_EXTRACT
2650                      || GET_CODE (new_i3_dest) == STRICT_LOW_PART
2651                      || GET_CODE (new_i3_dest) == SUBREG)
2652                 new_i3_dest = XEXP (new_i3_dest, 0);
2653
2654               while (GET_CODE (new_i2_dest) == ZERO_EXTRACT
2655                      || GET_CODE (new_i2_dest) == STRICT_LOW_PART
2656                      || GET_CODE (new_i2_dest) == SUBREG)
2657                 new_i2_dest = XEXP (new_i2_dest, 0);
2658
2659               if (REG_P (new_i3_dest)
2660                   && REG_P (new_i2_dest)
2661                   && REGNO (new_i3_dest) == REGNO (new_i2_dest))
2662                 REG_N_SETS (REGNO (new_i2_dest))++;
2663             }
2664         }
2665
2666       /* If we can split it and use I2DEST, go ahead and see if that
2667          helps things be recognized.  Verify that none of the registers
2668          are set between I2 and I3.  */
2669       if (insn_code_number < 0 && (split = find_split_point (&newpat, i3)) != 0
2670 #ifdef HAVE_cc0
2671           && REG_P (i2dest)
2672 #endif
2673           /* We need I2DEST in the proper mode.  If it is a hard register
2674              or the only use of a pseudo, we can change its mode.
2675              Make sure we don't change a hard register to have a mode that
2676              isn't valid for it, or change the number of registers.  */
2677           && (GET_MODE (*split) == GET_MODE (i2dest)
2678               || GET_MODE (*split) == VOIDmode
2679               || can_change_dest_mode (i2dest, added_sets_2,
2680                                        GET_MODE (*split)))
2681           && (next_real_insn (i2) == i3
2682               || ! use_crosses_set_p (*split, INSN_CUID (i2)))
2683           /* We can't overwrite I2DEST if its value is still used by
2684              NEWPAT.  */
2685           && ! reg_referenced_p (i2dest, newpat))
2686         {
2687           rtx newdest = i2dest;
2688           enum rtx_code split_code = GET_CODE (*split);
2689           enum machine_mode split_mode = GET_MODE (*split);
2690           bool subst_done = false;
2691           newi2pat = NULL_RTX;
2692
2693           /* Get NEWDEST as a register in the proper mode.  We have already
2694              validated that we can do this.  */
2695           if (GET_MODE (i2dest) != split_mode && split_mode != VOIDmode)
2696             {
2697               if (REGNO (i2dest) < FIRST_PSEUDO_REGISTER)
2698                 newdest = gen_rtx_REG (split_mode, REGNO (i2dest));
2699               else
2700                 {
2701                   SUBST_MODE (regno_reg_rtx[REGNO (i2dest)], split_mode);
2702                   newdest = regno_reg_rtx[REGNO (i2dest)];
2703                 }
2704             }
2705
2706           /* If *SPLIT is a (mult FOO (const_int pow2)), convert it to
2707              an ASHIFT.  This can occur if it was inside a PLUS and hence
2708              appeared to be a memory address.  This is a kludge.  */
2709           if (split_code == MULT
2710               && GET_CODE (XEXP (*split, 1)) == CONST_INT
2711               && INTVAL (XEXP (*split, 1)) > 0
2712               && (i = exact_log2 (INTVAL (XEXP (*split, 1)))) >= 0)
2713             {
2714               SUBST (*split, gen_rtx_ASHIFT (split_mode,
2715                                              XEXP (*split, 0), GEN_INT (i)));
2716               /* Update split_code because we may not have a multiply
2717                  anymore.  */
2718               split_code = GET_CODE (*split);
2719             }
2720
2721 #ifdef INSN_SCHEDULING
2722           /* If *SPLIT is a paradoxical SUBREG, when we split it, it should
2723              be written as a ZERO_EXTEND.  */
2724           if (split_code == SUBREG && MEM_P (SUBREG_REG (*split)))
2725             {
2726 #ifdef LOAD_EXTEND_OP
2727               /* Or as a SIGN_EXTEND if LOAD_EXTEND_OP says that that's
2728                  what it really is.  */
2729               if (LOAD_EXTEND_OP (GET_MODE (SUBREG_REG (*split)))
2730                   == SIGN_EXTEND)
2731                 SUBST (*split, gen_rtx_SIGN_EXTEND (split_mode,
2732                                                     SUBREG_REG (*split)));
2733               else
2734 #endif
2735                 SUBST (*split, gen_rtx_ZERO_EXTEND (split_mode,
2736                                                     SUBREG_REG (*split)));
2737             }
2738 #endif
2739
2740           /* Attempt to split binary operators using arithmetic identities.  */
2741           if (BINARY_P (SET_SRC (newpat))
2742               && split_mode == GET_MODE (SET_SRC (newpat))
2743               && ! side_effects_p (SET_SRC (newpat)))
2744             {
2745               rtx setsrc = SET_SRC (newpat);
2746               enum machine_mode mode = GET_MODE (setsrc);
2747               enum rtx_code code = GET_CODE (setsrc);
2748               rtx src_op0 = XEXP (setsrc, 0);
2749               rtx src_op1 = XEXP (setsrc, 1);
2750
2751               /* Split "X = Y op Y" as "Z = Y; X = Z op Z".  */
2752               if (rtx_equal_p (src_op0, src_op1))
2753                 {
2754                   newi2pat = gen_rtx_SET (VOIDmode, newdest, src_op0);
2755                   SUBST (XEXP (setsrc, 0), newdest);
2756                   SUBST (XEXP (setsrc, 1), newdest);
2757                   subst_done = true;
2758                 }
2759               /* Split "((P op Q) op R) op S" where op is PLUS or MULT.  */
2760               else if ((code == PLUS || code == MULT)
2761                        && GET_CODE (src_op0) == code
2762                        && GET_CODE (XEXP (src_op0, 0)) == code
2763                        && (INTEGRAL_MODE_P (mode)
2764                            || (FLOAT_MODE_P (mode)
2765                                && flag_unsafe_math_optimizations)))
2766                 {
2767                   rtx p = XEXP (XEXP (src_op0, 0), 0);
2768                   rtx q = XEXP (XEXP (src_op0, 0), 1);
2769                   rtx r = XEXP (src_op0, 1);
2770                   rtx s = src_op1;
2771
2772                   /* Split both "((X op Y) op X) op Y" and
2773                      "((X op Y) op Y) op X" as "T op T" where T is
2774                      "X op Y".  */
2775                   if ((rtx_equal_p (p,r) && rtx_equal_p (q,s))
2776                        || (rtx_equal_p (p,s) && rtx_equal_p (q,r)))
2777                     {
2778                       newi2pat = gen_rtx_SET (VOIDmode, newdest,
2779                                               XEXP (src_op0, 0));
2780                       SUBST (XEXP (setsrc, 0), newdest);
2781                       SUBST (XEXP (setsrc, 1), newdest);
2782                       subst_done = true;
2783                     }
2784                   /* Split "((X op X) op Y) op Y)" as "T op T" where
2785                      T is "X op Y".  */
2786                   else if (rtx_equal_p (p,q) && rtx_equal_p (r,s))
2787                     {
2788                       rtx tmp = simplify_gen_binary (code, mode, p, r);
2789                       newi2pat = gen_rtx_SET (VOIDmode, newdest, tmp);
2790                       SUBST (XEXP (setsrc, 0), newdest);
2791                       SUBST (XEXP (setsrc, 1), newdest);
2792                       subst_done = true;
2793                     }
2794                 }
2795             }
2796
2797           if (!subst_done)
2798             {
2799               newi2pat = gen_rtx_SET (VOIDmode, newdest, *split);
2800               SUBST (*split, newdest);
2801             }
2802
2803           i2_code_number = recog_for_combine (&newi2pat, i2, &new_i2_notes);
2804
2805           /* recog_for_combine might have added CLOBBERs to newi2pat.
2806              Make sure NEWPAT does not depend on the clobbered regs.  */
2807           if (GET_CODE (newi2pat) == PARALLEL)
2808             for (i = XVECLEN (newi2pat, 0) - 1; i >= 0; i--)
2809               if (GET_CODE (XVECEXP (newi2pat, 0, i)) == CLOBBER)
2810                 {
2811                   rtx reg = XEXP (XVECEXP (newi2pat, 0, i), 0);
2812                   if (reg_overlap_mentioned_p (reg, newpat))
2813                     {
2814                       undo_all ();
2815                       return 0;
2816                     }
2817                 }
2818
2819           /* If the split point was a MULT and we didn't have one before,
2820              don't use one now.  */
2821           if (i2_code_number >= 0 && ! (split_code == MULT && ! have_mult))
2822             insn_code_number = recog_for_combine (&newpat, i3, &new_i3_notes);
2823         }
2824     }
2825
2826   /* Check for a case where we loaded from memory in a narrow mode and
2827      then sign extended it, but we need both registers.  In that case,
2828      we have a PARALLEL with both loads from the same memory location.
2829      We can split this into a load from memory followed by a register-register
2830      copy.  This saves at least one insn, more if register allocation can
2831      eliminate the copy.
2832
2833      We cannot do this if the destination of the first assignment is a
2834      condition code register or cc0.  We eliminate this case by making sure
2835      the SET_DEST and SET_SRC have the same mode.
2836
2837      We cannot do this if the destination of the second assignment is
2838      a register that we have already assumed is zero-extended.  Similarly
2839      for a SUBREG of such a register.  */
2840
2841   else if (i1 && insn_code_number < 0 && asm_noperands (newpat) < 0
2842            && GET_CODE (newpat) == PARALLEL
2843            && XVECLEN (newpat, 0) == 2
2844            && GET_CODE (XVECEXP (newpat, 0, 0)) == SET
2845            && GET_CODE (SET_SRC (XVECEXP (newpat, 0, 0))) == SIGN_EXTEND
2846            && (GET_MODE (SET_DEST (XVECEXP (newpat, 0, 0)))
2847                == GET_MODE (SET_SRC (XVECEXP (newpat, 0, 0))))
2848            && GET_CODE (XVECEXP (newpat, 0, 1)) == SET
2849            && rtx_equal_p (SET_SRC (XVECEXP (newpat, 0, 1)),
2850                            XEXP (SET_SRC (XVECEXP (newpat, 0, 0)), 0))
2851            && ! use_crosses_set_p (SET_SRC (XVECEXP (newpat, 0, 1)),
2852                                    INSN_CUID (i2))
2853            && GET_CODE (SET_DEST (XVECEXP (newpat, 0, 1))) != ZERO_EXTRACT
2854            && GET_CODE (SET_DEST (XVECEXP (newpat, 0, 1))) != STRICT_LOW_PART
2855            && ! (temp = SET_DEST (XVECEXP (newpat, 0, 1)),
2856                  (REG_P (temp)
2857                   && reg_stat[REGNO (temp)].nonzero_bits != 0
2858                   && GET_MODE_BITSIZE (GET_MODE (temp)) < BITS_PER_WORD
2859                   && GET_MODE_BITSIZE (GET_MODE (temp)) < HOST_BITS_PER_INT
2860                   && (reg_stat[REGNO (temp)].nonzero_bits
2861                       != GET_MODE_MASK (word_mode))))
2862            && ! (GET_CODE (SET_DEST (XVECEXP (newpat, 0, 1))) == SUBREG
2863                  && (temp = SUBREG_REG (SET_DEST (XVECEXP (newpat, 0, 1))),
2864                      (REG_P (temp)
2865                       && reg_stat[REGNO (temp)].nonzero_bits != 0
2866                       && GET_MODE_BITSIZE (GET_MODE (temp)) < BITS_PER_WORD
2867                       && GET_MODE_BITSIZE (GET_MODE (temp)) < HOST_BITS_PER_INT
2868                       && (reg_stat[REGNO (temp)].nonzero_bits
2869                           != GET_MODE_MASK (word_mode)))))
2870            && ! reg_overlap_mentioned_p (SET_DEST (XVECEXP (newpat, 0, 1)),
2871                                          SET_SRC (XVECEXP (newpat, 0, 1)))
2872            && ! find_reg_note (i3, REG_UNUSED,
2873                                SET_DEST (XVECEXP (newpat, 0, 0))))
2874     {
2875       rtx ni2dest;
2876
2877       newi2pat = XVECEXP (newpat, 0, 0);
2878       ni2dest = SET_DEST (XVECEXP (newpat, 0, 0));
2879       newpat = XVECEXP (newpat, 0, 1);
2880       SUBST (SET_SRC (newpat),
2881              gen_lowpart (GET_MODE (SET_SRC (newpat)), ni2dest));
2882       i2_code_number = recog_for_combine (&newi2pat, i2, &new_i2_notes);
2883
2884       if (i2_code_number >= 0)
2885         insn_code_number = recog_for_combine (&newpat, i3, &new_i3_notes);
2886
2887       if (insn_code_number >= 0)
2888         swap_i2i3 = 1;
2889     }
2890
2891   /* Similarly, check for a case where we have a PARALLEL of two independent
2892      SETs but we started with three insns.  In this case, we can do the sets
2893      as two separate insns.  This case occurs when some SET allows two
2894      other insns to combine, but the destination of that SET is still live.  */
2895
2896   else if (i1 && insn_code_number < 0 && asm_noperands (newpat) < 0
2897            && GET_CODE (newpat) == PARALLEL
2898            && XVECLEN (newpat, 0) == 2
2899            && GET_CODE (XVECEXP (newpat, 0, 0)) == SET
2900            && GET_CODE (SET_DEST (XVECEXP (newpat, 0, 0))) != ZERO_EXTRACT
2901            && GET_CODE (SET_DEST (XVECEXP (newpat, 0, 0))) != STRICT_LOW_PART
2902            && GET_CODE (XVECEXP (newpat, 0, 1)) == SET
2903            && GET_CODE (SET_DEST (XVECEXP (newpat, 0, 1))) != ZERO_EXTRACT
2904            && GET_CODE (SET_DEST (XVECEXP (newpat, 0, 1))) != STRICT_LOW_PART
2905            && ! use_crosses_set_p (SET_SRC (XVECEXP (newpat, 0, 1)),
2906                                    INSN_CUID (i2))
2907            && ! reg_referenced_p (SET_DEST (XVECEXP (newpat, 0, 1)),
2908                                   XVECEXP (newpat, 0, 0))
2909            && ! reg_referenced_p (SET_DEST (XVECEXP (newpat, 0, 0)),
2910                                   XVECEXP (newpat, 0, 1))
2911            && ! (contains_muldiv (SET_SRC (XVECEXP (newpat, 0, 0)))
2912                  && contains_muldiv (SET_SRC (XVECEXP (newpat, 0, 1))))
2913 #ifdef HAVE_cc0
2914            /* We cannot split the parallel into two sets if both sets
2915               reference cc0.  */
2916            && ! (reg_referenced_p (cc0_rtx, XVECEXP (newpat, 0, 0))
2917                  && reg_referenced_p (cc0_rtx, XVECEXP (newpat, 0, 1)))
2918 #endif
2919            )
2920     {
2921       /* Normally, it doesn't matter which of the two is done first,
2922          but it does if one references cc0.  In that case, it has to
2923          be first.  */
2924 #ifdef HAVE_cc0
2925       if (reg_referenced_p (cc0_rtx, XVECEXP (newpat, 0, 0)))
2926         {
2927           newi2pat = XVECEXP (newpat, 0, 0);
2928           newpat = XVECEXP (newpat, 0, 1);
2929         }
2930       else
2931 #endif
2932         {
2933           newi2pat = XVECEXP (newpat, 0, 1);
2934           newpat = XVECEXP (newpat, 0, 0);
2935         }
2936
2937       i2_code_number = recog_for_combine (&newi2pat, i2, &new_i2_notes);
2938
2939       if (i2_code_number >= 0)
2940         insn_code_number = recog_for_combine (&newpat, i3, &new_i3_notes);
2941     }
2942
2943   /* If it still isn't recognized, fail and change things back the way they
2944      were.  */
2945   if ((insn_code_number < 0
2946        /* Is the result a reasonable ASM_OPERANDS?  */
2947        && (! check_asm_operands (newpat) || added_sets_1 || added_sets_2)))
2948     {
2949       undo_all ();
2950       return 0;
2951     }
2952
2953   /* If we had to change another insn, make sure it is valid also.  */
2954   if (undobuf.other_insn)
2955     {
2956       rtx other_pat = PATTERN (undobuf.other_insn);
2957       rtx new_other_notes;
2958       rtx note, next;
2959
2960       CLEAR_HARD_REG_SET (newpat_used_regs);
2961
2962       other_code_number = recog_for_combine (&other_pat, undobuf.other_insn,
2963                                              &new_other_notes);
2964
2965       if (other_code_number < 0 && ! check_asm_operands (other_pat))
2966         {
2967           undo_all ();
2968           return 0;
2969         }
2970
2971       PATTERN (undobuf.other_insn) = other_pat;
2972
2973       /* If any of the notes in OTHER_INSN were REG_UNUSED, ensure that they
2974          are still valid.  Then add any non-duplicate notes added by
2975          recog_for_combine.  */
2976       for (note = REG_NOTES (undobuf.other_insn); note; note = next)
2977         {
2978           next = XEXP (note, 1);
2979
2980           if (REG_NOTE_KIND (note) == REG_UNUSED
2981               && ! reg_set_p (XEXP (note, 0), PATTERN (undobuf.other_insn)))
2982             {
2983               if (REG_P (XEXP (note, 0)))
2984                 REG_N_DEATHS (REGNO (XEXP (note, 0)))--;
2985
2986               remove_note (undobuf.other_insn, note);
2987             }
2988         }
2989
2990       for (note = new_other_notes; note; note = XEXP (note, 1))
2991         if (REG_P (XEXP (note, 0)))
2992           REG_N_DEATHS (REGNO (XEXP (note, 0)))++;
2993
2994       distribute_notes (new_other_notes, undobuf.other_insn,
2995                         undobuf.other_insn, NULL_RTX, NULL_RTX, NULL_RTX);
2996     }
2997 #ifdef HAVE_cc0
2998   /* If I2 is the CC0 setter and I3 is the CC0 user then check whether
2999      they are adjacent to each other or not.  */
3000   {
3001     rtx p = prev_nonnote_insn (i3);
3002     if (p && p != i2 && NONJUMP_INSN_P (p) && newi2pat
3003         && sets_cc0_p (newi2pat))
3004       {
3005         undo_all ();
3006         return 0;
3007       }
3008   }
3009 #endif
3010
3011   /* Only allow this combination if insn_rtx_costs reports that the
3012      replacement instructions are cheaper than the originals.  */
3013   if (!combine_validate_cost (i1, i2, i3, newpat, newi2pat))
3014     {
3015       undo_all ();
3016       return 0;
3017     }
3018
3019   /* We now know that we can do this combination.  Merge the insns and
3020      update the status of registers and LOG_LINKS.  */
3021
3022   if (swap_i2i3)
3023     {
3024       rtx insn;
3025       rtx link;
3026       rtx ni2dest;
3027
3028       /* I3 now uses what used to be its destination and which is now
3029          I2's destination.  This requires us to do a few adjustments.  */
3030       PATTERN (i3) = newpat;
3031       adjust_for_new_dest (i3);
3032
3033       /* We need a LOG_LINK from I3 to I2.  But we used to have one,
3034          so we still will.
3035
3036          However, some later insn might be using I2's dest and have
3037          a LOG_LINK pointing at I3.  We must remove this link.
3038          The simplest way to remove the link is to point it at I1,
3039          which we know will be a NOTE.  */
3040
3041       /* newi2pat is usually a SET here; however, recog_for_combine might
3042          have added some clobbers.  */
3043       if (GET_CODE (newi2pat) == PARALLEL)
3044         ni2dest = SET_DEST (XVECEXP (newi2pat, 0, 0));
3045       else
3046         ni2dest = SET_DEST (newi2pat);
3047
3048       for (insn = NEXT_INSN (i3);
3049            insn && (this_basic_block->next_bb == EXIT_BLOCK_PTR
3050                     || insn != BB_HEAD (this_basic_block->next_bb));
3051            insn = NEXT_INSN (insn))
3052         {
3053           if (INSN_P (insn) && reg_referenced_p (ni2dest, PATTERN (insn)))
3054             {
3055               for (link = LOG_LINKS (insn); link;
3056                    link = XEXP (link, 1))
3057                 if (XEXP (link, 0) == i3)
3058                   XEXP (link, 0) = i1;
3059
3060               break;
3061             }
3062         }
3063     }
3064
3065   {
3066     rtx i3notes, i2notes, i1notes = 0;
3067     rtx i3links, i2links, i1links = 0;
3068     rtx midnotes = 0;
3069     unsigned int regno;
3070     /* Compute which registers we expect to eliminate.  newi2pat may be setting
3071        either i3dest or i2dest, so we must check it.  Also, i1dest may be the
3072        same as i3dest, in which case newi2pat may be setting i1dest.  */
3073     rtx elim_i2 = ((newi2pat && reg_set_p (i2dest, newi2pat))
3074                    || i2dest_in_i2src || i2dest_in_i1src
3075                    || !i2dest_killed
3076                    ? 0 : i2dest);
3077     rtx elim_i1 = (i1 == 0 || i1dest_in_i1src
3078                    || (newi2pat && reg_set_p (i1dest, newi2pat))
3079                    || !i1dest_killed
3080                    ? 0 : i1dest);
3081
3082     /* Get the old REG_NOTES and LOG_LINKS from all our insns and
3083        clear them.  */
3084     i3notes = REG_NOTES (i3), i3links = LOG_LINKS (i3);
3085     i2notes = REG_NOTES (i2), i2links = LOG_LINKS (i2);
3086     if (i1)
3087       i1notes = REG_NOTES (i1), i1links = LOG_LINKS (i1);
3088
3089     /* Ensure that we do not have something that should not be shared but
3090        occurs multiple times in the new insns.  Check this by first
3091        resetting all the `used' flags and then copying anything is shared.  */
3092
3093     reset_used_flags (i3notes);
3094     reset_used_flags (i2notes);
3095     reset_used_flags (i1notes);
3096     reset_used_flags (newpat);
3097     reset_used_flags (newi2pat);
3098     if (undobuf.other_insn)
3099       reset_used_flags (PATTERN (undobuf.other_insn));
3100
3101     i3notes = copy_rtx_if_shared (i3notes);
3102     i2notes = copy_rtx_if_shared (i2notes);
3103     i1notes = copy_rtx_if_shared (i1notes);
3104     newpat = copy_rtx_if_shared (newpat);
3105     newi2pat = copy_rtx_if_shared (newi2pat);
3106     if (undobuf.other_insn)
3107       reset_used_flags (PATTERN (undobuf.other_insn));
3108
3109     INSN_CODE (i3) = insn_code_number;
3110     PATTERN (i3) = newpat;
3111
3112     if (CALL_P (i3) && CALL_INSN_FUNCTION_USAGE (i3))
3113       {
3114         rtx call_usage = CALL_INSN_FUNCTION_USAGE (i3);
3115
3116         reset_used_flags (call_usage);
3117         call_usage = copy_rtx (call_usage);
3118
3119         if (substed_i2)
3120           replace_rtx (call_usage, i2dest, i2src);
3121
3122         if (substed_i1)
3123           replace_rtx (call_usage, i1dest, i1src);
3124
3125         CALL_INSN_FUNCTION_USAGE (i3) = call_usage;
3126       }
3127
3128     if (undobuf.other_insn)
3129       INSN_CODE (undobuf.other_insn) = other_code_number;
3130
3131     /* We had one special case above where I2 had more than one set and
3132        we replaced a destination of one of those sets with the destination
3133        of I3.  In that case, we have to update LOG_LINKS of insns later
3134        in this basic block.  Note that this (expensive) case is rare.
3135
3136        Also, in this case, we must pretend that all REG_NOTEs for I2
3137        actually came from I3, so that REG_UNUSED notes from I2 will be
3138        properly handled.  */
3139
3140     if (i3_subst_into_i2)
3141       {
3142         for (i = 0; i < XVECLEN (PATTERN (i2), 0); i++)
3143           if ((GET_CODE (XVECEXP (PATTERN (i2), 0, i)) == SET
3144                || GET_CODE (XVECEXP (PATTERN (i2), 0, i)) == CLOBBER)
3145               && REG_P (SET_DEST (XVECEXP (PATTERN (i2), 0, i)))
3146               && SET_DEST (XVECEXP (PATTERN (i2), 0, i)) != i2dest
3147               && ! find_reg_note (i2, REG_UNUSED,
3148                                   SET_DEST (XVECEXP (PATTERN (i2), 0, i))))
3149             for (temp = NEXT_INSN (i2);
3150                  temp && (this_basic_block->next_bb == EXIT_BLOCK_PTR
3151                           || BB_HEAD (this_basic_block) != temp);
3152                  temp = NEXT_INSN (temp))
3153               if (temp != i3 && INSN_P (temp))
3154                 for (link = LOG_LINKS (temp); link; link = XEXP (link, 1))
3155                   if (XEXP (link, 0) == i2)
3156                     XEXP (link, 0) = i3;
3157
3158         if (i3notes)
3159           {
3160             rtx link = i3notes;
3161             while (XEXP (link, 1))
3162               link = XEXP (link, 1);
3163             XEXP (link, 1) = i2notes;
3164           }
3165         else
3166           i3notes = i2notes;
3167         i2notes = 0;
3168       }
3169
3170     LOG_LINKS (i3) = 0;
3171     REG_NOTES (i3) = 0;
3172     LOG_LINKS (i2) = 0;
3173     REG_NOTES (i2) = 0;
3174
3175     if (newi2pat)
3176       {
3177         INSN_CODE (i2) = i2_code_number;
3178         PATTERN (i2) = newi2pat;
3179       }
3180     else
3181       SET_INSN_DELETED (i2);
3182
3183     if (i1)
3184       {
3185         LOG_LINKS (i1) = 0;
3186         REG_NOTES (i1) = 0;
3187         SET_INSN_DELETED (i1);
3188       }
3189
3190     /* Get death notes for everything that is now used in either I3 or
3191        I2 and used to die in a previous insn.  If we built two new
3192        patterns, move from I1 to I2 then I2 to I3 so that we get the
3193        proper movement on registers that I2 modifies.  */
3194
3195     if (newi2pat)
3196       {
3197         move_deaths (newi2pat, NULL_RTX, INSN_CUID (i1), i2, &midnotes);
3198         move_deaths (newpat, newi2pat, INSN_CUID (i1), i3, &midnotes);
3199       }
3200     else
3201       move_deaths (newpat, NULL_RTX, i1 ? INSN_CUID (i1) : INSN_CUID (i2),
3202                    i3, &midnotes);
3203
3204     /* Distribute all the LOG_LINKS and REG_NOTES from I1, I2, and I3.  */
3205     if (i3notes)
3206       distribute_notes (i3notes, i3, i3, newi2pat ? i2 : NULL_RTX,
3207                         elim_i2, elim_i1);
3208     if (i2notes)
3209       distribute_notes (i2notes, i2, i3, newi2pat ? i2 : NULL_RTX,
3210                         elim_i2, elim_i1);
3211     if (i1notes)
3212       distribute_notes (i1notes, i1, i3, newi2pat ? i2 : NULL_RTX,
3213                         elim_i2, elim_i1);
3214     if (midnotes)
3215       distribute_notes (midnotes, NULL_RTX, i3, newi2pat ? i2 : NULL_RTX,
3216                         elim_i2, elim_i1);
3217
3218     /* Distribute any notes added to I2 or I3 by recog_for_combine.  We
3219        know these are REG_UNUSED and want them to go to the desired insn,
3220        so we always pass it as i3.  We have not counted the notes in
3221        reg_n_deaths yet, so we need to do so now.  */
3222
3223     if (newi2pat && new_i2_notes)
3224       {
3225         for (temp = new_i2_notes; temp; temp = XEXP (temp, 1))
3226           if (REG_P (XEXP (temp, 0)))
3227             REG_N_DEATHS (REGNO (XEXP (temp, 0)))++;
3228
3229         distribute_notes (new_i2_notes, i2, i2, NULL_RTX, NULL_RTX, NULL_RTX);
3230       }
3231
3232     if (new_i3_notes)
3233       {
3234         for (temp = new_i3_notes; temp; temp = XEXP (temp, 1))
3235           if (REG_P (XEXP (temp, 0)))
3236             REG_N_DEATHS (REGNO (XEXP (temp, 0)))++;
3237
3238         distribute_notes (new_i3_notes, i3, i3, NULL_RTX, NULL_RTX, NULL_RTX);
3239       }
3240
3241     /* If I3DEST was used in I3SRC, it really died in I3.  We may need to
3242        put a REG_DEAD note for it somewhere.  If NEWI2PAT exists and sets
3243        I3DEST, the death must be somewhere before I2, not I3.  If we passed I3
3244        in that case, it might delete I2.  Similarly for I2 and I1.
3245        Show an additional death due to the REG_DEAD note we make here.  If
3246        we discard it in distribute_notes, we will decrement it again.  */
3247
3248     if (i3dest_killed)
3249       {
3250         if (REG_P (i3dest_killed))
3251           REG_N_DEATHS (REGNO (i3dest_killed))++;
3252
3253         if (newi2pat && reg_set_p (i3dest_killed, newi2pat))
3254           distribute_notes (gen_rtx_EXPR_LIST (REG_DEAD, i3dest_killed,
3255                                                NULL_RTX),
3256                             NULL_RTX, i2, NULL_RTX, elim_i2, elim_i1);
3257         else
3258           distribute_notes (gen_rtx_EXPR_LIST (REG_DEAD, i3dest_killed,
3259                                                NULL_RTX),
3260                             NULL_RTX, i3, newi2pat ? i2 : NULL_RTX,
3261                             elim_i2, elim_i1);
3262       }
3263
3264     if (i2dest_in_i2src)
3265       {
3266         if (REG_P (i2dest))
3267           REG_N_DEATHS (REGNO (i2dest))++;
3268
3269         if (newi2pat && reg_set_p (i2dest, newi2pat))
3270           distribute_notes (gen_rtx_EXPR_LIST (REG_DEAD, i2dest, NULL_RTX),
3271                             NULL_RTX, i2, NULL_RTX, NULL_RTX, NULL_RTX);
3272         else
3273           distribute_notes (gen_rtx_EXPR_LIST (REG_DEAD, i2dest, NULL_RTX),
3274                             NULL_RTX, i3, newi2pat ? i2 : NULL_RTX,
3275                             NULL_RTX, NULL_RTX);
3276       }
3277
3278     if (i1dest_in_i1src)
3279       {
3280         if (REG_P (i1dest))
3281           REG_N_DEATHS (REGNO (i1dest))++;
3282
3283         if (newi2pat && reg_set_p (i1dest, newi2pat))
3284           distribute_notes (gen_rtx_EXPR_LIST (REG_DEAD, i1dest, NULL_RTX),
3285                             NULL_RTX, i2, NULL_RTX, NULL_RTX, NULL_RTX);
3286         else
3287           distribute_notes (gen_rtx_EXPR_LIST (REG_DEAD, i1dest, NULL_RTX),
3288                             NULL_RTX, i3, newi2pat ? i2 : NULL_RTX,
3289                             NULL_RTX, NULL_RTX);
3290       }
3291
3292     distribute_links (i3links);
3293     distribute_links (i2links);
3294     distribute_links (i1links);
3295
3296     if (REG_P (i2dest))
3297       {
3298         rtx link;
3299         rtx i2_insn = 0, i2_val = 0, set;
3300
3301         /* The insn that used to set this register doesn't exist, and
3302            this life of the register may not exist either.  See if one of
3303            I3's links points to an insn that sets I2DEST.  If it does,
3304            that is now the last known value for I2DEST. If we don't update
3305            this and I2 set the register to a value that depended on its old
3306            contents, we will get confused.  If this insn is used, thing
3307            will be set correctly in combine_instructions.  */
3308
3309         for (link = LOG_LINKS (i3); link; link = XEXP (link, 1))
3310           if ((set = single_set (XEXP (link, 0))) != 0
3311               && rtx_equal_p (i2dest, SET_DEST (set)))
3312             i2_insn = XEXP (link, 0), i2_val = SET_SRC (set);
3313
3314         record_value_for_reg (i2dest, i2_insn, i2_val);
3315
3316         /* If the reg formerly set in I2 died only once and that was in I3,
3317            zero its use count so it won't make `reload' do any work.  */
3318         if (! added_sets_2
3319             && (newi2pat == 0 || ! reg_mentioned_p (i2dest, newi2pat))
3320             && ! i2dest_in_i2src)
3321           {
3322             regno = REGNO (i2dest);
3323             REG_N_SETS (regno)--;
3324           }
3325       }
3326
3327     if (i1 && REG_P (i1dest))
3328       {
3329         rtx link;
3330         rtx i1_insn = 0, i1_val = 0, set;
3331
3332         for (link = LOG_LINKS (i3); link; link = XEXP (link, 1))
3333           if ((set = single_set (XEXP (link, 0))) != 0
3334               && rtx_equal_p (i1dest, SET_DEST (set)))
3335             i1_insn = XEXP (link, 0), i1_val = SET_SRC (set);
3336
3337         record_value_for_reg (i1dest, i1_insn, i1_val);
3338
3339         regno = REGNO (i1dest);
3340         if (! added_sets_1 && ! i1dest_in_i1src)
3341           REG_N_SETS (regno)--;
3342       }
3343
3344     /* Update reg_stat[].nonzero_bits et al for any changes that may have
3345        been made to this insn.  The order of
3346        set_nonzero_bits_and_sign_copies() is important.  Because newi2pat
3347        can affect nonzero_bits of newpat */
3348     if (newi2pat)
3349       note_stores (newi2pat, set_nonzero_bits_and_sign_copies, NULL);
3350     note_stores (newpat, set_nonzero_bits_and_sign_copies, NULL);
3351
3352     /* Set new_direct_jump_p if a new return or simple jump instruction
3353        has been created.
3354
3355        If I3 is now an unconditional jump, ensure that it has a
3356        BARRIER following it since it may have initially been a
3357        conditional jump.  It may also be the last nonnote insn.  */
3358
3359     if (returnjump_p (i3) || any_uncondjump_p (i3))
3360       {
3361         *new_direct_jump_p = 1;
3362         mark_jump_label (PATTERN (i3), i3, 0);
3363
3364         if ((temp = next_nonnote_insn (i3)) == NULL_RTX
3365             || !BARRIER_P (temp))
3366           emit_barrier_after (i3);
3367       }
3368
3369     if (undobuf.other_insn != NULL_RTX
3370         && (returnjump_p (undobuf.other_insn)
3371             || any_uncondjump_p (undobuf.other_insn)))
3372       {
3373         *new_direct_jump_p = 1;
3374
3375         if ((temp = next_nonnote_insn (undobuf.other_insn)) == NULL_RTX
3376             || !BARRIER_P (temp))
3377           emit_barrier_after (undobuf.other_insn);
3378       }
3379
3380     /* An NOOP jump does not need barrier, but it does need cleaning up
3381        of CFG.  */
3382     if (GET_CODE (newpat) == SET
3383         && SET_SRC (newpat) == pc_rtx
3384         && SET_DEST (newpat) == pc_rtx)
3385       *new_direct_jump_p = 1;
3386   }
3387
3388   combine_successes++;
3389   undo_commit ();
3390
3391   if (added_links_insn
3392       && (newi2pat == 0 || INSN_CUID (added_links_insn) < INSN_CUID (i2))
3393       && INSN_CUID (added_links_insn) < INSN_CUID (i3))
3394     return added_links_insn;
3395   else
3396     return newi2pat ? i2 : i3;
3397 }
3398 \f
3399 /* Undo all the modifications recorded in undobuf.  */
3400
3401 static void
3402 undo_all (void)
3403 {
3404   struct undo *undo, *next;
3405
3406   for (undo = undobuf.undos; undo; undo = next)
3407     {
3408       next = undo->next;
3409       switch (undo->kind)
3410         {
3411         case UNDO_RTX:
3412           *undo->where.r = undo->old_contents.r;
3413           break;
3414         case UNDO_INT:
3415           *undo->where.i = undo->old_contents.i;
3416           break;
3417         case UNDO_MODE:
3418           PUT_MODE (*undo->where.r, undo->old_contents.m);
3419           break;
3420         default:
3421           gcc_unreachable ();
3422         }
3423
3424       undo->next = undobuf.frees;
3425       undobuf.frees = undo;
3426     }
3427
3428   undobuf.undos = 0;
3429 }
3430
3431 /* We've committed to accepting the changes we made.  Move all
3432    of the undos to the free list.  */
3433
3434 static void
3435 undo_commit (void)
3436 {
3437   struct undo *undo, *next;
3438
3439   for (undo = undobuf.undos; undo; undo = next)
3440     {
3441       next = undo->next;
3442       undo->next = undobuf.frees;
3443       undobuf.frees = undo;
3444     }
3445   undobuf.undos = 0;
3446 }
3447 \f
3448 /* Find the innermost point within the rtx at LOC, possibly LOC itself,
3449    where we have an arithmetic expression and return that point.  LOC will
3450    be inside INSN.
3451
3452    try_combine will call this function to see if an insn can be split into
3453    two insns.  */
3454
3455 static rtx *
3456 find_split_point (rtx *loc, rtx insn)
3457 {
3458   rtx x = *loc;
3459   enum rtx_code code = GET_CODE (x);
3460   rtx *split;
3461   unsigned HOST_WIDE_INT len = 0;
3462   HOST_WIDE_INT pos = 0;
3463   int unsignedp = 0;
3464   rtx inner = NULL_RTX;
3465
3466   /* First special-case some codes.  */
3467   switch (code)
3468     {
3469     case SUBREG:
3470 #ifdef INSN_SCHEDULING
3471       /* If we are making a paradoxical SUBREG invalid, it becomes a split
3472          point.  */
3473       if (MEM_P (SUBREG_REG (x)))
3474         return loc;
3475 #endif
3476       return find_split_point (&SUBREG_REG (x), insn);
3477
3478     case MEM:
3479 #ifdef HAVE_lo_sum
3480       /* If we have (mem (const ..)) or (mem (symbol_ref ...)), split it
3481          using LO_SUM and HIGH.  */
3482       if (GET_CODE (XEXP (x, 0)) == CONST
3483           || GET_CODE (XEXP (x, 0)) == SYMBOL_REF)
3484         {
3485           SUBST (XEXP (x, 0),
3486                  gen_rtx_LO_SUM (Pmode,
3487                                  gen_rtx_HIGH (Pmode, XEXP (x, 0)),
3488                                  XEXP (x, 0)));
3489           return &XEXP (XEXP (x, 0), 0);
3490         }
3491 #endif
3492
3493       /* If we have a PLUS whose second operand is a constant and the
3494          address is not valid, perhaps will can split it up using
3495          the machine-specific way to split large constants.  We use
3496          the first pseudo-reg (one of the virtual regs) as a placeholder;
3497          it will not remain in the result.  */
3498       if (GET_CODE (XEXP (x, 0)) == PLUS
3499           && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
3500           && ! memory_address_p (GET_MODE (x), XEXP (x, 0)))
3501         {
3502           rtx reg = regno_reg_rtx[FIRST_PSEUDO_REGISTER];
3503           rtx seq = split_insns (gen_rtx_SET (VOIDmode, reg, XEXP (x, 0)),
3504                                  subst_insn);
3505
3506           /* This should have produced two insns, each of which sets our
3507              placeholder.  If the source of the second is a valid address,
3508              we can make put both sources together and make a split point
3509              in the middle.  */
3510
3511           if (seq
3512               && NEXT_INSN (seq) != NULL_RTX
3513               && NEXT_INSN (NEXT_INSN (seq)) == NULL_RTX
3514               && NONJUMP_INSN_P (seq)
3515               && GET_CODE (PATTERN (seq)) == SET
3516               && SET_DEST (PATTERN (seq)) == reg
3517               && ! reg_mentioned_p (reg,
3518                                     SET_SRC (PATTERN (seq)))
3519               && NONJUMP_INSN_P (NEXT_INSN (seq))
3520               && GET_CODE (PATTERN (NEXT_INSN (seq))) == SET
3521               && SET_DEST (PATTERN (NEXT_INSN (seq))) == reg
3522               && memory_address_p (GET_MODE (x),
3523                                    SET_SRC (PATTERN (NEXT_INSN (seq)))))
3524             {
3525               rtx src1 = SET_SRC (PATTERN (seq));
3526               rtx src2 = SET_SRC (PATTERN (NEXT_INSN (seq)));
3527
3528               /* Replace the placeholder in SRC2 with SRC1.  If we can
3529                  find where in SRC2 it was placed, that can become our
3530                  split point and we can replace this address with SRC2.
3531                  Just try two obvious places.  */
3532
3533               src2 = replace_rtx (src2, reg, src1);
3534               split = 0;
3535               if (XEXP (src2, 0) == src1)
3536                 split = &XEXP (src2, 0);
3537               else if (GET_RTX_FORMAT (GET_CODE (XEXP (src2, 0)))[0] == 'e'
3538                        && XEXP (XEXP (src2, 0), 0) == src1)
3539                 split = &XEXP (XEXP (src2, 0), 0);
3540
3541               if (split)
3542                 {
3543                   SUBST (XEXP (x, 0), src2);
3544                   return split;
3545                 }
3546             }
3547
3548           /* If that didn't work, perhaps the first operand is complex and
3549              needs to be computed separately, so make a split point there.
3550              This will occur on machines that just support REG + CONST
3551              and have a constant moved through some previous computation.  */
3552
3553           else if (!OBJECT_P (XEXP (XEXP (x, 0), 0))
3554                    && ! (GET_CODE (XEXP (XEXP (x, 0), 0)) == SUBREG
3555                          && OBJECT_P (SUBREG_REG (XEXP (XEXP (x, 0), 0)))))
3556             return &XEXP (XEXP (x, 0), 0);
3557         }
3558       break;
3559
3560     case SET:
3561 #ifdef HAVE_cc0
3562       /* If SET_DEST is CC0 and SET_SRC is not an operand, a COMPARE, or a
3563          ZERO_EXTRACT, the most likely reason why this doesn't match is that
3564          we need to put the operand into a register.  So split at that
3565          point.  */
3566
3567       if (SET_DEST (x) == cc0_rtx
3568           && GET_CODE (SET_SRC (x)) != COMPARE
3569           && GET_CODE (SET_SRC (x)) != ZERO_EXTRACT
3570           && !OBJECT_P (SET_SRC (x))
3571           && ! (GET_CODE (SET_SRC (x)) == SUBREG
3572                 && OBJECT_P (SUBREG_REG (SET_SRC (x)))))
3573         return &SET_SRC (x);
3574 #endif
3575
3576       /* See if we can split SET_SRC as it stands.  */
3577       split = find_split_point (&SET_SRC (x), insn);
3578       if (split && split != &SET_SRC (x))
3579         return split;
3580
3581       /* See if we can split SET_DEST as it stands.  */
3582       split = find_split_point (&SET_DEST (x), insn);
3583       if (split && split != &SET_DEST (x))
3584         return split;
3585
3586       /* See if this is a bitfield assignment with everything constant.  If
3587          so, this is an IOR of an AND, so split it into that.  */
3588       if (GET_CODE (SET_DEST (x)) == ZERO_EXTRACT
3589           && (GET_MODE_BITSIZE (GET_MODE (XEXP (SET_DEST (x), 0)))
3590               <= HOST_BITS_PER_WIDE_INT)
3591           && GET_CODE (XEXP (SET_DEST (x), 1)) == CONST_INT
3592           && GET_CODE (XEXP (SET_DEST (x), 2)) == CONST_INT
3593           && GET_CODE (SET_SRC (x)) == CONST_INT
3594           && ((INTVAL (XEXP (SET_DEST (x), 1))
3595                + INTVAL (XEXP (SET_DEST (x), 2)))
3596               <= GET_MODE_BITSIZE (GET_MODE (XEXP (SET_DEST (x), 0))))
3597           && ! side_effects_p (XEXP (SET_DEST (x), 0)))
3598         {
3599           HOST_WIDE_INT pos = INTVAL (XEXP (SET_DEST (x), 2));
3600           unsigned HOST_WIDE_INT len = INTVAL (XEXP (SET_DEST (x), 1));
3601           unsigned HOST_WIDE_INT src = INTVAL (SET_SRC (x));
3602           rtx dest = XEXP (SET_DEST (x), 0);
3603           enum machine_mode mode = GET_MODE (dest);
3604           unsigned HOST_WIDE_INT mask = ((HOST_WIDE_INT) 1 << len) - 1;
3605           rtx or_mask;
3606
3607           if (BITS_BIG_ENDIAN)
3608             pos = GET_MODE_BITSIZE (mode) - len - pos;
3609
3610           or_mask = gen_int_mode (src << pos, mode);
3611           if (src == mask)
3612             SUBST (SET_SRC (x),
3613                    simplify_gen_binary (IOR, mode, dest, or_mask));
3614           else
3615             {
3616               rtx negmask = gen_int_mode (~(mask << pos), mode);
3617               SUBST (SET_SRC (x),
3618                      simplify_gen_binary (IOR, mode,
3619                                           simplify_gen_binary (AND, mode,
3620                                                                dest, negmask),
3621                                           or_mask));
3622             }
3623
3624           SUBST (SET_DEST (x), dest);
3625
3626           split = find_split_point (&SET_SRC (x), insn);
3627           if (split && split != &SET_SRC (x))
3628             return split;
3629         }
3630
3631       /* Otherwise, see if this is an operation that we can split into two.
3632          If so, try to split that.  */
3633       code = GET_CODE (SET_SRC (x));
3634
3635       switch (code)
3636         {
3637         case AND:
3638           /* If we are AND'ing with a large constant that is only a single
3639              bit and the result is only being used in a context where we
3640              need to know if it is zero or nonzero, replace it with a bit
3641              extraction.  This will avoid the large constant, which might
3642              have taken more than one insn to make.  If the constant were
3643              not a valid argument to the AND but took only one insn to make,
3644              this is no worse, but if it took more than one insn, it will
3645              be better.  */
3646
3647           if (GET_CODE (XEXP (SET_SRC (x), 1)) == CONST_INT
3648               && REG_P (XEXP (SET_SRC (x), 0))
3649               && (pos = exact_log2 (INTVAL (XEXP (SET_SRC (x), 1)))) >= 7
3650               && REG_P (SET_DEST (x))
3651               && (split = find_single_use (SET_DEST (x), insn, (rtx*) 0)) != 0
3652               && (GET_CODE (*split) == EQ || GET_CODE (*split) == NE)
3653               && XEXP (*split, 0) == SET_DEST (x)
3654               && XEXP (*split, 1) == const0_rtx)
3655             {
3656               rtx extraction = make_extraction (GET_MODE (SET_DEST (x)),
3657                                                 XEXP (SET_SRC (x), 0),
3658                                                 pos, NULL_RTX, 1, 1, 0, 0);
3659               if (extraction != 0)
3660                 {
3661                   SUBST (SET_SRC (x), extraction);
3662                   return find_split_point (loc, insn);
3663                 }
3664             }
3665           break;
3666
3667         case NE:
3668           /* If STORE_FLAG_VALUE is -1, this is (NE X 0) and only one bit of X
3669              is known to be on, this can be converted into a NEG of a shift.  */
3670           if (STORE_FLAG_VALUE == -1 && XEXP (SET_SRC (x), 1) == const0_rtx
3671               && GET_MODE (SET_SRC (x)) == GET_MODE (XEXP (SET_SRC (x), 0))
3672               && 1 <= (pos = exact_log2
3673                        (nonzero_bits (XEXP (SET_SRC (x), 0),
3674                                       GET_MODE (XEXP (SET_SRC (x), 0))))))
3675             {
3676               enum machine_mode mode = GET_MODE (XEXP (SET_SRC (x), 0));
3677
3678               SUBST (SET_SRC (x),
3679                      gen_rtx_NEG (mode,
3680                                   gen_rtx_LSHIFTRT (mode,
3681                                                     XEXP (SET_SRC (x), 0),
3682                                                     GEN_INT (pos))));
3683
3684               split = find_split_point (&SET_SRC (x), insn);
3685               if (split && split != &SET_SRC (x))
3686                 return split;
3687             }
3688           break;
3689
3690         case SIGN_EXTEND:
3691           inner = XEXP (SET_SRC (x), 0);
3692
3693           /* We can't optimize if either mode is a partial integer
3694              mode as we don't know how many bits are significant
3695              in those modes.  */
3696           if (GET_MODE_CLASS (GET_MODE (inner)) == MODE_PARTIAL_INT
3697               || GET_MODE_CLASS (GET_MODE (SET_SRC (x))) == MODE_PARTIAL_INT)
3698             break;
3699
3700           pos = 0;
3701           len = GET_MODE_BITSIZE (GET_MODE (inner));
3702           unsignedp = 0;
3703           break;
3704
3705         case SIGN_EXTRACT:
3706         case ZERO_EXTRACT:
3707           if (GET_CODE (XEXP (SET_SRC (x), 1)) == CONST_INT
3708               && GET_CODE (XEXP (SET_SRC (x), 2)) == CONST_INT)
3709             {
3710               inner = XEXP (SET_SRC (x), 0);
3711               len = INTVAL (XEXP (SET_SRC (x), 1));
3712               pos = INTVAL (XEXP (SET_SRC (x), 2));
3713
3714               if (BITS_BIG_ENDIAN)
3715                 pos = GET_MODE_BITSIZE (GET_MODE (inner)) - len - pos;
3716               unsignedp = (code == ZERO_EXTRACT);
3717             }
3718           break;
3719
3720         default:
3721           break;
3722         }
3723
3724       if (len && pos >= 0 && pos + len <= GET_MODE_BITSIZE (GET_MODE (inner)))
3725         {
3726           enum machine_mode mode = GET_MODE (SET_SRC (x));
3727
3728           /* For unsigned, we have a choice of a shift followed by an
3729              AND or two shifts.  Use two shifts for field sizes where the
3730              constant might be too large.  We assume here that we can
3731              always at least get 8-bit constants in an AND insn, which is
3732              true for every current RISC.  */
3733
3734           if (unsignedp && len <= 8)
3735             {
3736               SUBST (SET_SRC (x),
3737                      gen_rtx_AND (mode,
3738                                   gen_rtx_LSHIFTRT
3739                                   (mode, gen_lowpart (mode, inner),
3740                                    GEN_INT (pos)),
3741                                   GEN_INT (((HOST_WIDE_INT) 1 << len) - 1)));
3742
3743               split = find_split_point (&SET_SRC (x), insn);
3744               if (split && split != &SET_SRC (x))
3745                 return split;
3746             }
3747           else
3748             {
3749               SUBST (SET_SRC (x),
3750                      gen_rtx_fmt_ee
3751                      (unsignedp ? LSHIFTRT : ASHIFTRT, mode,
3752                       gen_rtx_ASHIFT (mode,
3753                                       gen_lowpart (mode, inner),
3754                                       GEN_INT (GET_MODE_BITSIZE (mode)
3755                                                - len - pos)),
3756                       GEN_INT (GET_MODE_BITSIZE (mode) - len)));
3757
3758               split = find_split_point (&SET_SRC (x), insn);
3759               if (split && split != &SET_SRC (x))
3760                 return split;
3761             }
3762         }
3763
3764       /* See if this is a simple operation with a constant as the second
3765          operand.  It might be that this constant is out of range and hence
3766          could be used as a split point.  */
3767       if (BINARY_P (SET_SRC (x))
3768           && CONSTANT_P (XEXP (SET_SRC (x), 1))
3769           && (OBJECT_P (XEXP (SET_SRC (x), 0))
3770               || (GET_CODE (XEXP (SET_SRC (x), 0)) == SUBREG
3771                   && OBJECT_P (SUBREG_REG (XEXP (SET_SRC (x), 0))))))
3772         return &XEXP (SET_SRC (x), 1);
3773
3774       /* Finally, see if this is a simple operation with its first operand
3775          not in a register.  The operation might require this operand in a
3776          register, so return it as a split point.  We can always do this
3777          because if the first operand were another operation, we would have
3778          already found it as a split point.  */
3779       if ((BINARY_P (SET_SRC (x)) || UNARY_P (SET_SRC (x)))
3780           && ! register_operand (XEXP (SET_SRC (x), 0), VOIDmode))
3781         return &XEXP (SET_SRC (x), 0);
3782
3783       return 0;
3784
3785     case AND:
3786     case IOR:
3787       /* We write NOR as (and (not A) (not B)), but if we don't have a NOR,
3788          it is better to write this as (not (ior A B)) so we can split it.
3789          Similarly for IOR.  */
3790       if (GET_CODE (XEXP (x, 0)) == NOT && GET_CODE (XEXP (x, 1)) == NOT)
3791         {
3792           SUBST (*loc,
3793                  gen_rtx_NOT (GET_MODE (x),
3794                               gen_rtx_fmt_ee (code == IOR ? AND : IOR,
3795                                               GET_MODE (x),
3796                                               XEXP (XEXP (x, 0), 0),
3797                                               XEXP (XEXP (x, 1), 0))));
3798           return find_split_point (loc, insn);
3799         }
3800
3801       /* Many RISC machines have a large set of logical insns.  If the
3802          second operand is a NOT, put it first so we will try to split the
3803          other operand first.  */
3804       if (GET_CODE (XEXP (x, 1)) == NOT)
3805         {
3806           rtx tem = XEXP (x, 0);
3807           SUBST (XEXP (x, 0), XEXP (x, 1));
3808           SUBST (XEXP (x, 1), tem);
3809         }
3810       break;
3811
3812     default:
3813       break;
3814     }
3815
3816   /* Otherwise, select our actions depending on our rtx class.  */
3817   switch (GET_RTX_CLASS (code))
3818     {
3819     case RTX_BITFIELD_OPS:              /* This is ZERO_EXTRACT and SIGN_EXTRACT.  */
3820     case RTX_TERNARY:
3821       split = find_split_point (&XEXP (x, 2), insn);
3822       if (split)
3823         return split;
3824       /* ... fall through ...  */
3825     case RTX_BIN_ARITH:
3826     case RTX_COMM_ARITH:
3827     case RTX_COMPARE:
3828     case RTX_COMM_COMPARE:
3829       split = find_split_point (&XEXP (x, 1), insn);
3830       if (split)
3831         return split;
3832       /* ... fall through ...  */
3833     case RTX_UNARY:
3834       /* Some machines have (and (shift ...) ...) insns.  If X is not
3835          an AND, but XEXP (X, 0) is, use it as our split point.  */
3836       if (GET_CODE (x) != AND && GET_CODE (XEXP (x, 0)) == AND)
3837         return &XEXP (x, 0);
3838
3839       split = find_split_point (&XEXP (x, 0), insn);
3840       if (split)
3841         return split;
3842       return loc;
3843
3844     default:
3845       /* Otherwise, we don't have a split point.  */
3846       return 0;
3847     }
3848 }
3849 \f
3850 /* Throughout X, replace FROM with TO, and return the result.
3851    The result is TO if X is FROM;
3852    otherwise the result is X, but its contents may have been modified.
3853    If they were modified, a record was made in undobuf so that
3854    undo_all will (among other things) return X to its original state.
3855
3856    If the number of changes necessary is too much to record to undo,
3857    the excess changes are not made, so the result is invalid.
3858    The changes already made can still be undone.
3859    undobuf.num_undo is incremented for such changes, so by testing that
3860    the caller can tell whether the result is valid.
3861
3862    `n_occurrences' is incremented each time FROM is replaced.
3863
3864    IN_DEST is nonzero if we are processing the SET_DEST of a SET.
3865
3866    UNIQUE_COPY is nonzero if each substitution must be unique.  We do this
3867    by copying if `n_occurrences' is nonzero.  */
3868
3869 static rtx
3870 subst (rtx x, rtx from, rtx to, int in_dest, int unique_copy)
3871 {
3872   enum rtx_code code = GET_CODE (x);
3873   enum machine_mode op0_mode = VOIDmode;
3874   const char *fmt;
3875   int len, i;
3876   rtx new;
3877
3878 /* Two expressions are equal if they are identical copies of a shared
3879    RTX or if they are both registers with the same register number
3880    and mode.  */
3881
3882 #define COMBINE_RTX_EQUAL_P(X,Y)                        \
3883   ((X) == (Y)                                           \
3884    || (REG_P (X) && REG_P (Y)   \
3885        && REGNO (X) == REGNO (Y) && GET_MODE (X) == GET_MODE (Y)))
3886
3887   if (! in_dest && COMBINE_RTX_EQUAL_P (x, from))
3888     {
3889       n_occurrences++;
3890       return (unique_copy && n_occurrences > 1 ? copy_rtx (to) : to);
3891     }
3892
3893   /* If X and FROM are the same register but different modes, they will
3894      not have been seen as equal above.  However, flow.c will make a
3895      LOG_LINKS entry for that case.  If we do nothing, we will try to
3896      rerecognize our original insn and, when it succeeds, we will
3897      delete the feeding insn, which is incorrect.
3898
3899      So force this insn not to match in this (rare) case.  */
3900   if (! in_dest && code == REG && REG_P (from)
3901       && REGNO (x) == REGNO (from))
3902     return gen_rtx_CLOBBER (GET_MODE (x), const0_rtx);
3903
3904   /* If this is an object, we are done unless it is a MEM or LO_SUM, both
3905      of which may contain things that can be combined.  */
3906   if (code != MEM && code != LO_SUM && OBJECT_P (x))
3907     return x;
3908
3909   /* It is possible to have a subexpression appear twice in the insn.
3910      Suppose that FROM is a register that appears within TO.
3911      Then, after that subexpression has been scanned once by `subst',
3912      the second time it is scanned, TO may be found.  If we were
3913      to scan TO here, we would find FROM within it and create a
3914      self-referent rtl structure which is completely wrong.  */
3915   if (COMBINE_RTX_EQUAL_P (x, to))
3916     return to;
3917
3918   /* Parallel asm_operands need special attention because all of the
3919      inputs are shared across the arms.  Furthermore, unsharing the
3920      rtl results in recognition failures.  Failure to handle this case
3921      specially can result in circular rtl.
3922
3923      Solve this by doing a normal pass across the first entry of the
3924      parallel, and only processing the SET_DESTs of the subsequent
3925      entries.  Ug.  */
3926
3927   if (code == PARALLEL
3928       && GET_CODE (XVECEXP (x, 0, 0)) == SET
3929       && GET_CODE (SET_SRC (XVECEXP (x, 0, 0))) == ASM_OPERANDS)
3930     {
3931       new = subst (XVECEXP (x, 0, 0), from, to, 0, unique_copy);
3932
3933       /* If this substitution failed, this whole thing fails.  */
3934       if (GET_CODE (new) == CLOBBER
3935           && XEXP (new, 0) == const0_rtx)
3936         return new;
3937
3938       SUBST (XVECEXP (x, 0, 0), new);
3939
3940       for (i = XVECLEN (x, 0) - 1; i >= 1; i--)
3941         {
3942           rtx dest = SET_DEST (XVECEXP (x, 0, i));
3943
3944           if (!REG_P (dest)
3945               && GET_CODE (dest) != CC0
3946               && GET_CODE (dest) != PC)
3947             {
3948               new = subst (dest, from, to, 0, unique_copy);
3949
3950               /* If this substitution failed, this whole thing fails.  */
3951               if (GET_CODE (new) == CLOBBER
3952                   && XEXP (new, 0) == const0_rtx)
3953                 return new;
3954
3955               SUBST (SET_DEST (XVECEXP (x, 0, i)), new);
3956             }
3957         }
3958     }
3959   else
3960     {
3961       len = GET_RTX_LENGTH (code);
3962       fmt = GET_RTX_FORMAT (code);
3963
3964       /* We don't need to process a SET_DEST that is a register, CC0,
3965          or PC, so set up to skip this common case.  All other cases
3966          where we want to suppress replacing something inside a
3967          SET_SRC are handled via the IN_DEST operand.  */
3968       if (code == SET
3969           && (REG_P (SET_DEST (x))
3970               || GET_CODE (SET_DEST (x)) == CC0
3971               || GET_CODE (SET_DEST (x)) == PC))
3972         fmt = "ie";
3973
3974       /* Get the mode of operand 0 in case X is now a SIGN_EXTEND of a
3975          constant.  */
3976       if (fmt[0] == 'e')
3977         op0_mode = GET_MODE (XEXP (x, 0));
3978
3979       for (i = 0; i < len; i++)
3980         {
3981           if (fmt[i] == 'E')
3982             {
3983               int j;
3984               for (j = XVECLEN (x, i) - 1; j >= 0; j--)
3985                 {
3986                   if (COMBINE_RTX_EQUAL_P (XVECEXP (x, i, j), from))
3987                     {
3988                       new = (unique_copy && n_occurrences
3989                              ? copy_rtx (to) : to);
3990                       n_occurrences++;
3991                     }
3992                   else
3993                     {
3994                       new = subst (XVECEXP (x, i, j), from, to, 0,
3995                                    unique_copy);
3996
3997                       /* If this substitution failed, this whole thing
3998                          fails.  */
3999                       if (GET_CODE (new) == CLOBBER
4000                           && XEXP (new, 0) == const0_rtx)
4001                         return new;
4002                     }
4003
4004                   SUBST (XVECEXP (x, i, j), new);
4005                 }
4006             }
4007           else if (fmt[i] == 'e')
4008             {
4009               /* If this is a register being set, ignore it.  */
4010               new = XEXP (x, i);
4011               if (in_dest
4012                   && i == 0
4013                   && (((code == SUBREG || code == ZERO_EXTRACT)
4014                        && REG_P (new))
4015                       || code == STRICT_LOW_PART))
4016                 ;
4017
4018               else if (COMBINE_RTX_EQUAL_P (XEXP (x, i), from))
4019                 {
4020                   /* In general, don't install a subreg involving two
4021                      modes not tieable.  It can worsen register
4022                      allocation, and can even make invalid reload
4023                      insns, since the reg inside may need to be copied
4024                      from in the outside mode, and that may be invalid
4025                      if it is an fp reg copied in integer mode.
4026
4027                      We allow two exceptions to this: It is valid if
4028                      it is inside another SUBREG and the mode of that
4029                      SUBREG and the mode of the inside of TO is
4030                      tieable and it is valid if X is a SET that copies
4031                      FROM to CC0.  */
4032
4033                   if (GET_CODE (to) == SUBREG
4034                       && ! MODES_TIEABLE_P (GET_MODE (to),
4035                                             GET_MODE (SUBREG_REG (to)))
4036                       && ! (code == SUBREG
4037                             && MODES_TIEABLE_P (GET_MODE (x),
4038                                                 GET_MODE (SUBREG_REG (to))))
4039 #ifdef HAVE_cc0
4040                       && ! (code == SET && i == 1 && XEXP (x, 0) == cc0_rtx)
4041 #endif
4042                       )
4043                     return gen_rtx_CLOBBER (VOIDmode, const0_rtx);
4044
4045 #ifdef CANNOT_CHANGE_MODE_CLASS
4046                   if (code == SUBREG
4047                       && REG_P (to)
4048                       && REGNO (to) < FIRST_PSEUDO_REGISTER
4049                       && REG_CANNOT_CHANGE_MODE_P (REGNO (to),
4050                                                    GET_MODE (to),
4051                                                    GET_MODE (x)))
4052                     return gen_rtx_CLOBBER (VOIDmode, const0_rtx);
4053 #endif
4054
4055                   new = (unique_copy && n_occurrences ? copy_rtx (to) : to);
4056                   n_occurrences++;
4057                 }
4058               else
4059                 /* If we are in a SET_DEST, suppress most cases unless we
4060                    have gone inside a MEM, in which case we want to
4061                    simplify the address.  We assume here that things that
4062                    are actually part of the destination have their inner
4063                    parts in the first expression.  This is true for SUBREG,
4064                    STRICT_LOW_PART, and ZERO_EXTRACT, which are the only
4065                    things aside from REG and MEM that should appear in a
4066                    SET_DEST.  */
4067                 new = subst (XEXP (x, i), from, to,
4068                              (((in_dest
4069                                 && (code == SUBREG || code == STRICT_LOW_PART
4070                                     || code == ZERO_EXTRACT))
4071                                || code == SET)
4072                               && i == 0), unique_copy);
4073
4074               /* If we found that we will have to reject this combination,
4075                  indicate that by returning the CLOBBER ourselves, rather than
4076                  an expression containing it.  This will speed things up as
4077                  well as prevent accidents where two CLOBBERs are considered
4078                  to be equal, thus producing an incorrect simplification.  */
4079
4080               if (GET_CODE (new) == CLOBBER && XEXP (new, 0) == const0_rtx)
4081                 return new;
4082
4083               if (GET_CODE (x) == SUBREG
4084                   && (GET_CODE (new) == CONST_INT
4085                       || GET_CODE (new) == CONST_DOUBLE))
4086                 {
4087                   enum machine_mode mode = GET_MODE (x);
4088
4089                   x = simplify_subreg (GET_MODE (x), new,
4090                                        GET_MODE (SUBREG_REG (x)),
4091                                        SUBREG_BYTE (x));
4092                   if (! x)
4093                     x = gen_rtx_CLOBBER (mode, const0_rtx);
4094                 }
4095               else if (GET_CODE (new) == CONST_INT
4096                        && GET_CODE (x) == ZERO_EXTEND)
4097                 {
4098                   x = simplify_unary_operation (ZERO_EXTEND, GET_MODE (x),
4099                                                 new, GET_MODE (XEXP (x, 0)));
4100                   gcc_assert (x);
4101                 }
4102               else
4103                 SUBST (XEXP (x, i), new);
4104             }
4105         }
4106     }
4107
4108   /* Try to simplify X.  If the simplification changed the code, it is likely
4109      that further simplification will help, so loop, but limit the number
4110      of repetitions that will be performed.  */
4111
4112   for (i = 0; i < 4; i++)
4113     {
4114       /* If X is sufficiently simple, don't bother trying to do anything
4115          with it.  */
4116       if (code != CONST_INT && code != REG && code != CLOBBER)
4117         x = combine_simplify_rtx (x, op0_mode, in_dest);
4118
4119       if (GET_CODE (x) == code)
4120         break;
4121
4122       code = GET_CODE (x);
4123
4124       /* We no longer know the original mode of operand 0 since we
4125          have changed the form of X)  */
4126       op0_mode = VOIDmode;
4127     }
4128
4129   return x;
4130 }
4131 \f
4132 /* Simplify X, a piece of RTL.  We just operate on the expression at the
4133    outer level; call `subst' to simplify recursively.  Return the new
4134    expression.
4135
4136    OP0_MODE is the original mode of XEXP (x, 0).  IN_DEST is nonzero
4137    if we are inside a SET_DEST.  */
4138
4139 static rtx
4140 combine_simplify_rtx (rtx x, enum machine_mode op0_mode, int in_dest)
4141 {
4142   enum rtx_code code = GET_CODE (x);
4143   enum machine_mode mode = GET_MODE (x);
4144   rtx temp;
4145   int i;
4146
4147   /* If this is a commutative operation, put a constant last and a complex
4148      expression first.  We don't need to do this for comparisons here.  */
4149   if (COMMUTATIVE_ARITH_P (x)
4150       && swap_commutative_operands_p (XEXP (x, 0), XEXP (x, 1)))
4151     {
4152       temp = XEXP (x, 0);
4153       SUBST (XEXP (x, 0), XEXP (x, 1));
4154       SUBST (XEXP (x, 1), temp);
4155     }
4156
4157   /* If this is a simple operation applied to an IF_THEN_ELSE, try
4158      applying it to the arms of the IF_THEN_ELSE.  This often simplifies
4159      things.  Check for cases where both arms are testing the same
4160      condition.
4161
4162      Don't do anything if all operands are very simple.  */
4163
4164   if ((BINARY_P (x)
4165        && ((!OBJECT_P (XEXP (x, 0))
4166             && ! (GET_CODE (XEXP (x, 0)) == SUBREG
4167                   && OBJECT_P (SUBREG_REG (XEXP (x, 0)))))
4168            || (!OBJECT_P (XEXP (x, 1))
4169                && ! (GET_CODE (XEXP (x, 1)) == SUBREG
4170                      && OBJECT_P (SUBREG_REG (XEXP (x, 1)))))))
4171       || (UNARY_P (x)
4172           && (!OBJECT_P (XEXP (x, 0))
4173                && ! (GET_CODE (XEXP (x, 0)) == SUBREG
4174                      && OBJECT_P (SUBREG_REG (XEXP (x, 0)))))))
4175     {
4176       rtx cond, true_rtx, false_rtx;
4177
4178       cond = if_then_else_cond (x, &true_rtx, &false_rtx);
4179       if (cond != 0
4180           /* If everything is a comparison, what we have is highly unlikely
4181              to be simpler, so don't use it.  */
4182           && ! (COMPARISON_P (x)
4183                 && (COMPARISON_P (true_rtx) || COMPARISON_P (false_rtx))))
4184         {
4185           rtx cop1 = const0_rtx;
4186           enum rtx_code cond_code = simplify_comparison (NE, &cond, &cop1);
4187
4188           if (cond_code == NE && COMPARISON_P (cond))
4189             return x;
4190
4191           /* Simplify the alternative arms; this may collapse the true and
4192              false arms to store-flag values.  Be careful to use copy_rtx
4193              here since true_rtx or false_rtx might share RTL with x as a
4194              result of the if_then_else_cond call above.  */
4195           true_rtx = subst (copy_rtx (true_rtx), pc_rtx, pc_rtx, 0, 0);
4196           false_rtx = subst (copy_rtx (false_rtx), pc_rtx, pc_rtx, 0, 0);
4197
4198           /* If true_rtx and false_rtx are not general_operands, an if_then_else
4199              is unlikely to be simpler.  */
4200           if (general_operand (true_rtx, VOIDmode)
4201               && general_operand (false_rtx, VOIDmode))
4202             {
4203               enum rtx_code reversed;
4204
4205               /* Restarting if we generate a store-flag expression will cause
4206                  us to loop.  Just drop through in this case.  */
4207
4208               /* If the result values are STORE_FLAG_VALUE and zero, we can
4209                  just make the comparison operation.  */
4210               if (true_rtx == const_true_rtx && false_rtx == const0_rtx)
4211                 x = simplify_gen_relational (cond_code, mode, VOIDmode,
4212                                              cond, cop1);
4213               else if (true_rtx == const0_rtx && false_rtx == const_true_rtx
4214                        && ((reversed = reversed_comparison_code_parts
4215                                         (cond_code, cond, cop1, NULL))
4216                            != UNKNOWN))
4217                 x = simplify_gen_relational (reversed, mode, VOIDmode,
4218                                              cond, cop1);
4219
4220               /* Likewise, we can make the negate of a comparison operation
4221                  if the result values are - STORE_FLAG_VALUE and zero.  */
4222               else if (GET_CODE (true_rtx) == CONST_INT
4223                        && INTVAL (true_rtx) == - STORE_FLAG_VALUE
4224                        && false_rtx == const0_rtx)
4225                 x = simplify_gen_unary (NEG, mode,
4226                                         simplify_gen_relational (cond_code,
4227                                                                  mode, VOIDmode,
4228                                                                  cond, cop1),
4229                                         mode);
4230               else if (GET_CODE (false_rtx) == CONST_INT
4231                        && INTVAL (false_rtx) == - STORE_FLAG_VALUE
4232                        && true_rtx == const0_rtx
4233                        && ((reversed = reversed_comparison_code_parts
4234                                         (cond_code, cond, cop1, NULL))
4235                            != UNKNOWN))
4236                 x = simplify_gen_unary (NEG, mode,
4237                                         simplify_gen_relational (reversed,
4238                                                                  mode, VOIDmode,
4239                                                                  cond, cop1),
4240                                         mode);
4241               else
4242                 return gen_rtx_IF_THEN_ELSE (mode,
4243                                              simplify_gen_relational (cond_code,
4244                                                                       mode,
4245                                                                       VOIDmode,
4246                                                                       cond,
4247                                                                       cop1),
4248                                              true_rtx, false_rtx);
4249
4250               code = GET_CODE (x);
4251               op0_mode = VOIDmode;
4252             }
4253         }
4254     }
4255
4256   /* Try to fold this expression in case we have constants that weren't
4257      present before.  */
4258   temp = 0;
4259   switch (GET_RTX_CLASS (code))
4260     {
4261     case RTX_UNARY:
4262       if (op0_mode == VOIDmode)
4263         op0_mode = GET_MODE (XEXP (x, 0));
4264       temp = simplify_unary_operation (code, mode, XEXP (x, 0), op0_mode);
4265       break;
4266     case RTX_COMPARE:
4267     case RTX_COMM_COMPARE:
4268       {
4269         enum machine_mode cmp_mode = GET_MODE (XEXP (x, 0));
4270         if (cmp_mode == VOIDmode)
4271           {
4272             cmp_mode = GET_MODE (XEXP (x, 1));
4273             if (cmp_mode == VOIDmode)
4274               cmp_mode = op0_mode;
4275           }
4276         temp = simplify_relational_operation (code, mode, cmp_mode,
4277                                               XEXP (x, 0), XEXP (x, 1));
4278       }
4279       break;
4280     case RTX_COMM_ARITH:
4281     case RTX_BIN_ARITH:
4282       temp = simplify_binary_operation (code, mode, XEXP (x, 0), XEXP (x, 1));
4283       break;
4284     case RTX_BITFIELD_OPS:
4285     case RTX_TERNARY:
4286       temp = simplify_ternary_operation (code, mode, op0_mode, XEXP (x, 0),
4287                                          XEXP (x, 1), XEXP (x, 2));
4288       break;
4289     default:
4290       break;
4291     }
4292
4293   if (temp)
4294     {
4295       x = temp;
4296       code = GET_CODE (temp);
4297       op0_mode = VOIDmode;
4298       mode = GET_MODE (temp);
4299     }
4300
4301   /* First see if we can apply the inverse distributive law.  */
4302   if (code == PLUS || code == MINUS
4303       || code == AND || code == IOR || code == XOR)
4304     {
4305       x = apply_distributive_law (x);
4306       code = GET_CODE (x);
4307       op0_mode = VOIDmode;
4308     }
4309
4310   /* If CODE is an associative operation not otherwise handled, see if we
4311      can associate some operands.  This can win if they are constants or
4312      if they are logically related (i.e. (a & b) & a).  */
4313   if ((code == PLUS || code == MINUS || code == MULT || code == DIV
4314        || code == AND || code == IOR || code == XOR
4315        || code == SMAX || code == SMIN || code == UMAX || code == UMIN)
4316       && ((INTEGRAL_MODE_P (mode) && code != DIV)
4317           || (flag_unsafe_math_optimizations && FLOAT_MODE_P (mode))))
4318     {
4319       if (GET_CODE (XEXP (x, 0)) == code)
4320         {
4321           rtx other = XEXP (XEXP (x, 0), 0);
4322           rtx inner_op0 = XEXP (XEXP (x, 0), 1);
4323           rtx inner_op1 = XEXP (x, 1);
4324           rtx inner;
4325
4326           /* Make sure we pass the constant operand if any as the second
4327              one if this is a commutative operation.  */
4328           if (CONSTANT_P (inner_op0) && COMMUTATIVE_ARITH_P (x))
4329             {
4330               rtx tem = inner_op0;
4331               inner_op0 = inner_op1;
4332               inner_op1 = tem;
4333             }
4334           inner = simplify_binary_operation (code == MINUS ? PLUS
4335                                              : code == DIV ? MULT
4336                                              : code,
4337                                              mode, inner_op0, inner_op1);
4338
4339           /* For commutative operations, try the other pair if that one
4340              didn't simplify.  */
4341           if (inner == 0 && COMMUTATIVE_ARITH_P (x))
4342             {
4343               other = XEXP (XEXP (x, 0), 1);
4344               inner = simplify_binary_operation (code, mode,
4345                                                  XEXP (XEXP (x, 0), 0),
4346                                                  XEXP (x, 1));
4347             }
4348
4349           if (inner)
4350             return simplify_gen_binary (code, mode, other, inner);
4351         }
4352     }
4353
4354   /* A little bit of algebraic simplification here.  */
4355   switch (code)
4356     {
4357     case MEM:
4358       /* Ensure that our address has any ASHIFTs converted to MULT in case
4359          address-recognizing predicates are called later.  */
4360       temp = make_compound_operation (XEXP (x, 0), MEM);
4361       SUBST (XEXP (x, 0), temp);
4362       break;
4363
4364     case SUBREG:
4365       if (op0_mode == VOIDmode)
4366         op0_mode = GET_MODE (SUBREG_REG (x));
4367
4368       /* See if this can be moved to simplify_subreg.  */
4369       if (CONSTANT_P (SUBREG_REG (x))
4370           && subreg_lowpart_offset (mode, op0_mode) == SUBREG_BYTE (x)
4371              /* Don't call gen_lowpart if the inner mode
4372                 is VOIDmode and we cannot simplify it, as SUBREG without
4373                 inner mode is invalid.  */
4374           && (GET_MODE (SUBREG_REG (x)) != VOIDmode
4375               || gen_lowpart_common (mode, SUBREG_REG (x))))
4376         return gen_lowpart (mode, SUBREG_REG (x));
4377
4378       if (GET_MODE_CLASS (GET_MODE (SUBREG_REG (x))) == MODE_CC)
4379         break;
4380       {
4381         rtx temp;
4382         temp = simplify_subreg (mode, SUBREG_REG (x), op0_mode,
4383                                 SUBREG_BYTE (x));
4384         if (temp)
4385           return temp;
4386       }
4387
4388       /* Don't change the mode of the MEM if that would change the meaning
4389          of the address.  */
4390       if (MEM_P (SUBREG_REG (x))
4391           && (MEM_VOLATILE_P (SUBREG_REG (x))
4392               || mode_dependent_address_p (XEXP (SUBREG_REG (x), 0))))
4393         return gen_rtx_CLOBBER (mode, const0_rtx);
4394
4395       /* Note that we cannot do any narrowing for non-constants since
4396          we might have been counting on using the fact that some bits were
4397          zero.  We now do this in the SET.  */
4398
4399       break;
4400
4401     case NEG:
4402       temp = expand_compound_operation (XEXP (x, 0));
4403
4404       /* For C equal to the width of MODE minus 1, (neg (ashiftrt X C)) can be
4405          replaced by (lshiftrt X C).  This will convert
4406          (neg (sign_extract X 1 Y)) to (zero_extract X 1 Y).  */
4407
4408       if (GET_CODE (temp) == ASHIFTRT
4409           && GET_CODE (XEXP (temp, 1)) == CONST_INT
4410           && INTVAL (XEXP (temp, 1)) == GET_MODE_BITSIZE (mode) - 1)
4411         return simplify_shift_const (NULL_RTX, LSHIFTRT, mode, XEXP (temp, 0),
4412                                      INTVAL (XEXP (temp, 1)));
4413
4414       /* If X has only a single bit that might be nonzero, say, bit I, convert
4415          (neg X) to (ashiftrt (ashift X C-I) C-I) where C is the bitsize of
4416          MODE minus 1.  This will convert (neg (zero_extract X 1 Y)) to
4417          (sign_extract X 1 Y).  But only do this if TEMP isn't a register
4418          or a SUBREG of one since we'd be making the expression more
4419          complex if it was just a register.  */
4420
4421       if (!REG_P (temp)
4422           && ! (GET_CODE (temp) == SUBREG
4423                 && REG_P (SUBREG_REG (temp)))
4424           && (i = exact_log2 (nonzero_bits (temp, mode))) >= 0)
4425         {
4426           rtx temp1 = simplify_shift_const
4427             (NULL_RTX, ASHIFTRT, mode,
4428              simplify_shift_const (NULL_RTX, ASHIFT, mode, temp,
4429                                    GET_MODE_BITSIZE (mode) - 1 - i),
4430              GET_MODE_BITSIZE (mode) - 1 - i);
4431
4432           /* If all we did was surround TEMP with the two shifts, we
4433              haven't improved anything, so don't use it.  Otherwise,
4434              we are better off with TEMP1.  */
4435           if (GET_CODE (temp1) != ASHIFTRT
4436               || GET_CODE (XEXP (temp1, 0)) != ASHIFT
4437               || XEXP (XEXP (temp1, 0), 0) != temp)
4438             return temp1;
4439         }
4440       break;
4441
4442     case TRUNCATE:
4443       /* We can't handle truncation to a partial integer mode here
4444          because we don't know the real bitsize of the partial
4445          integer mode.  */
4446       if (GET_MODE_CLASS (mode) == MODE_PARTIAL_INT)
4447         break;
4448
4449       if (GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT
4450           && TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (mode),
4451                                     GET_MODE_BITSIZE (GET_MODE (XEXP (x, 0)))))
4452         SUBST (XEXP (x, 0),
4453                force_to_mode (XEXP (x, 0), GET_MODE (XEXP (x, 0)),
4454                               GET_MODE_MASK (mode), 0));
4455
4456       /* Similarly to what we do in simplify-rtx.c, a truncate of a register
4457          whose value is a comparison can be replaced with a subreg if
4458          STORE_FLAG_VALUE permits.  */
4459       if (GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT
4460           && ((HOST_WIDE_INT) STORE_FLAG_VALUE & ~GET_MODE_MASK (mode)) == 0
4461           && (temp = get_last_value (XEXP (x, 0)))
4462           && COMPARISON_P (temp))
4463         return gen_lowpart (mode, XEXP (x, 0));
4464       break;
4465
4466 #ifdef HAVE_cc0
4467     case COMPARE:
4468       /* Convert (compare FOO (const_int 0)) to FOO unless we aren't
4469          using cc0, in which case we want to leave it as a COMPARE
4470          so we can distinguish it from a register-register-copy.  */
4471       if (XEXP (x, 1) == const0_rtx)
4472         return XEXP (x, 0);
4473
4474       /* x - 0 is the same as x unless x's mode has signed zeros and
4475          allows rounding towards -infinity.  Under those conditions,
4476          0 - 0 is -0.  */
4477       if (!(HONOR_SIGNED_ZEROS (GET_MODE (XEXP (x, 0)))
4478             && HONOR_SIGN_DEPENDENT_ROUNDING (GET_MODE (XEXP (x, 0))))
4479           && XEXP (x, 1) == CONST0_RTX (GET_MODE (XEXP (x, 0))))
4480         return XEXP (x, 0);
4481       break;
4482 #endif
4483
4484     case CONST:
4485       /* (const (const X)) can become (const X).  Do it this way rather than
4486          returning the inner CONST since CONST can be shared with a
4487          REG_EQUAL note.  */
4488       if (GET_CODE (XEXP (x, 0)) == CONST)
4489         SUBST (XEXP (x, 0), XEXP (XEXP (x, 0), 0));
4490       break;
4491
4492 #ifdef HAVE_lo_sum
4493     case LO_SUM:
4494       /* Convert (lo_sum (high FOO) FOO) to FOO.  This is necessary so we
4495          can add in an offset.  find_split_point will split this address up
4496          again if it doesn't match.  */
4497       if (GET_CODE (XEXP (x, 0)) == HIGH
4498           && rtx_equal_p (XEXP (XEXP (x, 0), 0), XEXP (x, 1)))
4499         return XEXP (x, 1);
4500       break;
4501 #endif
4502
4503     case PLUS:
4504       /* (plus (xor (and <foo> (const_int pow2 - 1)) <c>) <-c>)
4505          when c is (const_int (pow2 + 1) / 2) is a sign extension of a
4506          bit-field and can be replaced by either a sign_extend or a
4507          sign_extract.  The `and' may be a zero_extend and the two
4508          <c>, -<c> constants may be reversed.  */
4509       if (GET_CODE (XEXP (x, 0)) == XOR
4510           && GET_CODE (XEXP (x, 1)) == CONST_INT
4511           && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
4512           && INTVAL (XEXP (x, 1)) == -INTVAL (XEXP (XEXP (x, 0), 1))
4513           && ((i = exact_log2 (INTVAL (XEXP (XEXP (x, 0), 1)))) >= 0
4514               || (i = exact_log2 (INTVAL (XEXP (x, 1)))) >= 0)
4515           && GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT
4516           && ((GET_CODE (XEXP (XEXP (x, 0), 0)) == AND
4517                && GET_CODE (XEXP (XEXP (XEXP (x, 0), 0), 1)) == CONST_INT
4518                && (INTVAL (XEXP (XEXP (XEXP (x, 0), 0), 1))
4519                    == ((HOST_WIDE_INT) 1 << (i + 1)) - 1))
4520               || (GET_CODE (XEXP (XEXP (x, 0), 0)) == ZERO_EXTEND
4521                   && (GET_MODE_BITSIZE (GET_MODE (XEXP (XEXP (XEXP (x, 0), 0), 0)))
4522                       == (unsigned int) i + 1))))
4523         return simplify_shift_const
4524           (NULL_RTX, ASHIFTRT, mode,
4525            simplify_shift_const (NULL_RTX, ASHIFT, mode,
4526                                  XEXP (XEXP (XEXP (x, 0), 0), 0),
4527                                  GET_MODE_BITSIZE (mode) - (i + 1)),
4528            GET_MODE_BITSIZE (mode) - (i + 1));
4529
4530       /* If only the low-order bit of X is possibly nonzero, (plus x -1)
4531          can become (ashiftrt (ashift (xor x 1) C) C) where C is
4532          the bitsize of the mode - 1.  This allows simplification of
4533          "a = (b & 8) == 0;"  */
4534       if (XEXP (x, 1) == constm1_rtx
4535           && !REG_P (XEXP (x, 0))
4536           && ! (GET_CODE (XEXP (x, 0)) == SUBREG
4537                 && REG_P (SUBREG_REG (XEXP (x, 0))))
4538           && nonzero_bits (XEXP (x, 0), mode) == 1)
4539         return simplify_shift_const (NULL_RTX, ASHIFTRT, mode,
4540            simplify_shift_const (NULL_RTX, ASHIFT, mode,
4541                                  gen_rtx_XOR (mode, XEXP (x, 0), const1_rtx),
4542                                  GET_MODE_BITSIZE (mode) - 1),
4543            GET_MODE_BITSIZE (mode) - 1);
4544
4545       /* If we are adding two things that have no bits in common, convert
4546          the addition into an IOR.  This will often be further simplified,
4547          for example in cases like ((a & 1) + (a & 2)), which can
4548          become a & 3.  */
4549
4550       if (GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT
4551           && (nonzero_bits (XEXP (x, 0), mode)
4552               & nonzero_bits (XEXP (x, 1), mode)) == 0)
4553         {
4554           /* Try to simplify the expression further.  */
4555           rtx tor = simplify_gen_binary (IOR, mode, XEXP (x, 0), XEXP (x, 1));
4556           temp = combine_simplify_rtx (tor, mode, in_dest);
4557
4558           /* If we could, great.  If not, do not go ahead with the IOR
4559              replacement, since PLUS appears in many special purpose
4560              address arithmetic instructions.  */
4561           if (GET_CODE (temp) != CLOBBER && temp != tor)
4562             return temp;
4563         }
4564       break;
4565
4566     case MINUS:
4567       /* (minus <foo> (and <foo> (const_int -pow2))) becomes
4568          (and <foo> (const_int pow2-1))  */
4569       if (GET_CODE (XEXP (x, 1)) == AND
4570           && GET_CODE (XEXP (XEXP (x, 1), 1)) == CONST_INT
4571           && exact_log2 (-INTVAL (XEXP (XEXP (x, 1), 1))) >= 0
4572           && rtx_equal_p (XEXP (XEXP (x, 1), 0), XEXP (x, 0)))
4573         return simplify_and_const_int (NULL_RTX, mode, XEXP (x, 0),
4574                                        -INTVAL (XEXP (XEXP (x, 1), 1)) - 1);
4575       break;
4576
4577     case MULT:
4578       /* If we have (mult (plus A B) C), apply the distributive law and then
4579          the inverse distributive law to see if things simplify.  This
4580          occurs mostly in addresses, often when unrolling loops.  */
4581
4582       if (GET_CODE (XEXP (x, 0)) == PLUS)
4583         {
4584           rtx result = distribute_and_simplify_rtx (x, 0);
4585           if (result)
4586             return result;
4587         }
4588
4589       /* Try simplify a*(b/c) as (a*b)/c.  */
4590       if (FLOAT_MODE_P (mode) && flag_unsafe_math_optimizations
4591           && GET_CODE (XEXP (x, 0)) == DIV)
4592         {
4593           rtx tem = simplify_binary_operation (MULT, mode,
4594                                                XEXP (XEXP (x, 0), 0),
4595                                                XEXP (x, 1));
4596           if (tem)
4597             return simplify_gen_binary (DIV, mode, tem, XEXP (XEXP (x, 0), 1));
4598         }
4599       break;
4600
4601     case UDIV:
4602       /* If this is a divide by a power of two, treat it as a shift if
4603          its first operand is a shift.  */
4604       if (GET_CODE (XEXP (x, 1)) == CONST_INT
4605           && (i = exact_log2 (INTVAL (XEXP (x, 1)))) >= 0
4606           && (GET_CODE (XEXP (x, 0)) == ASHIFT
4607               || GET_CODE (XEXP (x, 0)) == LSHIFTRT
4608               || GET_CODE (XEXP (x, 0)) == ASHIFTRT
4609               || GET_CODE (XEXP (x, 0)) == ROTATE
4610               || GET_CODE (XEXP (x, 0)) == ROTATERT))
4611         return simplify_shift_const (NULL_RTX, LSHIFTRT, mode, XEXP (x, 0), i);
4612       break;
4613
4614     case EQ:  case NE:
4615     case GT:  case GTU:  case GE:  case GEU:
4616     case LT:  case LTU:  case LE:  case LEU:
4617     case UNEQ:  case LTGT:
4618     case UNGT:  case UNGE:
4619     case UNLT:  case UNLE:
4620     case UNORDERED: case ORDERED:
4621       /* If the first operand is a condition code, we can't do anything
4622          with it.  */
4623       if (GET_CODE (XEXP (x, 0)) == COMPARE
4624           || (GET_MODE_CLASS (GET_MODE (XEXP (x, 0))) != MODE_CC
4625               && ! CC0_P (XEXP (x, 0))))
4626         {
4627           rtx op0 = XEXP (x, 0);
4628           rtx op1 = XEXP (x, 1);
4629           enum rtx_code new_code;
4630
4631           if (GET_CODE (op0) == COMPARE)
4632             op1 = XEXP (op0, 1), op0 = XEXP (op0, 0);
4633
4634           /* Simplify our comparison, if possible.  */
4635           new_code = simplify_comparison (code, &op0, &op1);
4636
4637           /* If STORE_FLAG_VALUE is 1, we can convert (ne x 0) to simply X
4638              if only the low-order bit is possibly nonzero in X (such as when
4639              X is a ZERO_EXTRACT of one bit).  Similarly, we can convert EQ to
4640              (xor X 1) or (minus 1 X); we use the former.  Finally, if X is
4641              known to be either 0 or -1, NE becomes a NEG and EQ becomes
4642              (plus X 1).
4643
4644              Remove any ZERO_EXTRACT we made when thinking this was a
4645              comparison.  It may now be simpler to use, e.g., an AND.  If a
4646              ZERO_EXTRACT is indeed appropriate, it will be placed back by
4647              the call to make_compound_operation in the SET case.  */
4648
4649           if (STORE_FLAG_VALUE == 1
4650               && new_code == NE && GET_MODE_CLASS (mode) == MODE_INT
4651               && op1 == const0_rtx
4652               && mode == GET_MODE (op0)
4653               && nonzero_bits (op0, mode) == 1)
4654             return gen_lowpart (mode,
4655                                 expand_compound_operation (op0));
4656
4657           else if (STORE_FLAG_VALUE == 1
4658                    && new_code == NE && GET_MODE_CLASS (mode) == MODE_INT
4659                    && op1 == const0_rtx
4660                    && mode == GET_MODE (op0)
4661                    && (num_sign_bit_copies (op0, mode)
4662                        == GET_MODE_BITSIZE (mode)))
4663             {
4664               op0 = expand_compound_operation (op0);
4665               return simplify_gen_unary (NEG, mode,
4666                                          gen_lowpart (mode, op0),
4667                                          mode);
4668             }
4669
4670           else if (STORE_FLAG_VALUE == 1
4671                    && new_code == EQ && GET_MODE_CLASS (mode) == MODE_INT
4672                    && op1 == const0_rtx
4673                    && mode == GET_MODE (op0)
4674                    && nonzero_bits (op0, mode) == 1)
4675             {
4676               op0 = expand_compound_operation (op0);
4677               return simplify_gen_binary (XOR, mode,
4678                                           gen_lowpart (mode, op0),
4679                                           const1_rtx);
4680             }
4681
4682           else if (STORE_FLAG_VALUE == 1
4683                    && new_code == EQ && GET_MODE_CLASS (mode) == MODE_INT
4684                    && op1 == const0_rtx
4685                    && mode == GET_MODE (op0)
4686                    && (num_sign_bit_copies (op0, mode)
4687                        == GET_MODE_BITSIZE (mode)))
4688             {
4689               op0 = expand_compound_operation (op0);
4690               return plus_constant (gen_lowpart (mode, op0), 1);
4691             }
4692
4693           /* If STORE_FLAG_VALUE is -1, we have cases similar to
4694              those above.  */
4695           if (STORE_FLAG_VALUE == -1
4696               && new_code == NE && GET_MODE_CLASS (mode) == MODE_INT
4697               && op1 == const0_rtx
4698               && (num_sign_bit_copies (op0, mode)
4699                   == GET_MODE_BITSIZE (mode)))
4700             return gen_lowpart (mode,
4701                                 expand_compound_operation (op0));
4702
4703           else if (STORE_FLAG_VALUE == -1
4704                    && new_code == NE && GET_MODE_CLASS (mode) == MODE_INT
4705                    && op1 == const0_rtx
4706                    && mode == GET_MODE (op0)
4707                    && nonzero_bits (op0, mode) == 1)
4708             {
4709               op0 = expand_compound_operation (op0);
4710               return simplify_gen_unary (NEG, mode,
4711                                          gen_lowpart (mode, op0),
4712                                          mode);
4713             }
4714
4715           else if (STORE_FLAG_VALUE == -1
4716                    && new_code == EQ && GET_MODE_CLASS (mode) == MODE_INT
4717                    && op1 == const0_rtx
4718                    && mode == GET_MODE (op0)
4719                    && (num_sign_bit_copies (op0, mode)
4720                        == GET_MODE_BITSIZE (mode)))
4721             {
4722               op0 = expand_compound_operation (op0);
4723               return simplify_gen_unary (NOT, mode,
4724                                          gen_lowpart (mode, op0),
4725                                          mode);
4726             }
4727
4728           /* If X is 0/1, (eq X 0) is X-1.  */
4729           else if (STORE_FLAG_VALUE == -1
4730                    && new_code == EQ && GET_MODE_CLASS (mode) == MODE_INT
4731                    && op1 == const0_rtx
4732                    && mode == GET_MODE (op0)
4733                    && nonzero_bits (op0, mode) == 1)
4734             {
4735               op0 = expand_compound_operation (op0);
4736               return plus_constant (gen_lowpart (mode, op0), -1);
4737             }
4738
4739           /* If STORE_FLAG_VALUE says to just test the sign bit and X has just
4740              one bit that might be nonzero, we can convert (ne x 0) to
4741              (ashift x c) where C puts the bit in the sign bit.  Remove any
4742              AND with STORE_FLAG_VALUE when we are done, since we are only
4743              going to test the sign bit.  */
4744           if (new_code == NE && GET_MODE_CLASS (mode) == MODE_INT
4745               && GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT
4746               && ((STORE_FLAG_VALUE & GET_MODE_MASK (mode))
4747                   == (unsigned HOST_WIDE_INT) 1 << (GET_MODE_BITSIZE (mode) - 1))
4748               && op1 == const0_rtx
4749               && mode == GET_MODE (op0)
4750               && (i = exact_log2 (nonzero_bits (op0, mode))) >= 0)
4751             {
4752               x = simplify_shift_const (NULL_RTX, ASHIFT, mode,
4753                                         expand_compound_operation (op0),
4754                                         GET_MODE_BITSIZE (mode) - 1 - i);
4755               if (GET_CODE (x) == AND && XEXP (x, 1) == const_true_rtx)
4756                 return XEXP (x, 0);
4757               else
4758                 return x;
4759             }
4760
4761           /* If the code changed, return a whole new comparison.  */
4762           if (new_code != code)
4763             return gen_rtx_fmt_ee (new_code, mode, op0, op1);
4764
4765           /* Otherwise, keep this operation, but maybe change its operands.
4766              This also converts (ne (compare FOO BAR) 0) to (ne FOO BAR).  */
4767           SUBST (XEXP (x, 0), op0);
4768           SUBST (XEXP (x, 1), op1);
4769         }
4770       break;
4771
4772     case IF_THEN_ELSE:
4773       return simplify_if_then_else (x);
4774
4775     case ZERO_EXTRACT:
4776     case SIGN_EXTRACT:
4777     case ZERO_EXTEND:
4778     case SIGN_EXTEND:
4779       /* If we are processing SET_DEST, we are done.  */
4780       if (in_dest)
4781         return x;
4782
4783       return expand_compound_operation (x);
4784
4785     case SET:
4786       return simplify_set (x);
4787
4788     case AND:
4789     case IOR:
4790       return simplify_logical (x);
4791
4792     case ASHIFT:
4793     case LSHIFTRT:
4794     case ASHIFTRT:
4795     case ROTATE:
4796     case ROTATERT:
4797       /* If this is a shift by a constant amount, simplify it.  */
4798       if (GET_CODE (XEXP (x, 1)) == CONST_INT)
4799         return simplify_shift_const (x, code, mode, XEXP (x, 0),
4800                                      INTVAL (XEXP (x, 1)));
4801
4802       else if (SHIFT_COUNT_TRUNCATED && !REG_P (XEXP (x, 1)))
4803         SUBST (XEXP (x, 1),
4804                force_to_mode (XEXP (x, 1), GET_MODE (XEXP (x, 1)),
4805                               ((HOST_WIDE_INT) 1
4806                                << exact_log2 (GET_MODE_BITSIZE (GET_MODE (x))))
4807                               - 1,
4808                               0));
4809       break;
4810
4811     default:
4812       break;
4813     }
4814
4815   return x;
4816 }
4817 \f
4818 /* Simplify X, an IF_THEN_ELSE expression.  Return the new expression.  */
4819
4820 static rtx
4821 simplify_if_then_else (rtx x)
4822 {
4823   enum machine_mode mode = GET_MODE (x);
4824   rtx cond = XEXP (x, 0);
4825   rtx true_rtx = XEXP (x, 1);
4826   rtx false_rtx = XEXP (x, 2);
4827   enum rtx_code true_code = GET_CODE (cond);
4828   int comparison_p = COMPARISON_P (cond);
4829   rtx temp;
4830   int i;
4831   enum rtx_code false_code;
4832   rtx reversed;
4833
4834   /* Simplify storing of the truth value.  */
4835   if (comparison_p && true_rtx == const_true_rtx && false_rtx == const0_rtx)
4836     return simplify_gen_relational (true_code, mode, VOIDmode,
4837                                     XEXP (cond, 0), XEXP (cond, 1));
4838
4839   /* Also when the truth value has to be reversed.  */
4840   if (comparison_p
4841       && true_rtx == const0_rtx && false_rtx == const_true_rtx
4842       && (reversed = reversed_comparison (cond, mode)))
4843     return reversed;
4844
4845   /* Sometimes we can simplify the arm of an IF_THEN_ELSE if a register used
4846      in it is being compared against certain values.  Get the true and false
4847      comparisons and see if that says anything about the value of each arm.  */
4848
4849   if (comparison_p
4850       && ((false_code = reversed_comparison_code (cond, NULL))
4851           != UNKNOWN)
4852       && REG_P (XEXP (cond, 0)))
4853     {
4854       HOST_WIDE_INT nzb;
4855       rtx from = XEXP (cond, 0);
4856       rtx true_val = XEXP (cond, 1);
4857       rtx false_val = true_val;
4858       int swapped = 0;
4859
4860       /* If FALSE_CODE is EQ, swap the codes and arms.  */
4861
4862       if (false_code == EQ)
4863         {
4864           swapped = 1, true_code = EQ, false_code = NE;
4865           temp = true_rtx, true_rtx = false_rtx, false_rtx = temp;
4866         }
4867
4868       /* If we are comparing against zero and the expression being tested has
4869          only a single bit that might be nonzero, that is its value when it is
4870          not equal to zero.  Similarly if it is known to be -1 or 0.  */
4871
4872       if (true_code == EQ && true_val == const0_rtx
4873           && exact_log2 (nzb = nonzero_bits (from, GET_MODE (from))) >= 0)
4874         false_code = EQ, false_val = GEN_INT (nzb);
4875       else if (true_code == EQ && true_val == const0_rtx
4876                && (num_sign_bit_copies (from, GET_MODE (from))
4877                    == GET_MODE_BITSIZE (GET_MODE (from))))
4878         false_code = EQ, false_val = constm1_rtx;
4879
4880       /* Now simplify an arm if we know the value of the register in the
4881          branch and it is used in the arm.  Be careful due to the potential
4882          of locally-shared RTL.  */
4883
4884       if (reg_mentioned_p (from, true_rtx))
4885         true_rtx = subst (known_cond (copy_rtx (true_rtx), true_code,
4886                                       from, true_val),
4887                       pc_rtx, pc_rtx, 0, 0);
4888       if (reg_mentioned_p (from, false_rtx))
4889         false_rtx = subst (known_cond (copy_rtx (false_rtx), false_code,
4890                                    from, false_val),
4891                        pc_rtx, pc_rtx, 0, 0);
4892
4893       SUBST (XEXP (x, 1), swapped ? false_rtx : true_rtx);
4894       SUBST (XEXP (x, 2), swapped ? true_rtx : false_rtx);
4895
4896       true_rtx = XEXP (x, 1);
4897       false_rtx = XEXP (x, 2);
4898       true_code = GET_CODE (cond);
4899     }
4900
4901   /* If we have (if_then_else FOO (pc) (label_ref BAR)) and FOO can be
4902      reversed, do so to avoid needing two sets of patterns for
4903      subtract-and-branch insns.  Similarly if we have a constant in the true
4904      arm, the false arm is the same as the first operand of the comparison, or
4905      the false arm is more complicated than the true arm.  */
4906
4907   if (comparison_p
4908       && reversed_comparison_code (cond, NULL) != UNKNOWN
4909       && (true_rtx == pc_rtx
4910           || (CONSTANT_P (true_rtx)
4911               && GET_CODE (false_rtx) != CONST_INT && false_rtx != pc_rtx)
4912           || true_rtx == const0_rtx
4913           || (OBJECT_P (true_rtx) && !OBJECT_P (false_rtx))
4914           || (GET_CODE (true_rtx) == SUBREG && OBJECT_P (SUBREG_REG (true_rtx))
4915               && !OBJECT_P (false_rtx))
4916           || reg_mentioned_p (true_rtx, false_rtx)
4917           || rtx_equal_p (false_rtx, XEXP (cond, 0))))
4918     {
4919       true_code = reversed_comparison_code (cond, NULL);
4920       SUBST (XEXP (x, 0), reversed_comparison (cond, GET_MODE (cond)));
4921       SUBST (XEXP (x, 1), false_rtx);
4922       SUBST (XEXP (x, 2), true_rtx);
4923
4924       temp = true_rtx, true_rtx = false_rtx, false_rtx = temp;
4925       cond = XEXP (x, 0);
4926
4927       /* It is possible that the conditional has been simplified out.  */
4928       true_code = GET_CODE (cond);
4929       comparison_p = COMPARISON_P (cond);
4930     }
4931
4932   /* If the two arms are identical, we don't need the comparison.  */
4933
4934   if (rtx_equal_p (true_rtx, false_rtx) && ! side_effects_p (cond))
4935     return true_rtx;
4936
4937   /* Convert a == b ? b : a to "a".  */
4938   if (true_code == EQ && ! side_effects_p (cond)
4939       && !HONOR_NANS (mode)
4940       && rtx_equal_p (XEXP (cond, 0), false_rtx)
4941       && rtx_equal_p (XEXP (cond, 1), true_rtx))
4942     return false_rtx;
4943   else if (true_code == NE && ! side_effects_p (cond)
4944            && !HONOR_NANS (mode)
4945            && rtx_equal_p (XEXP (cond, 0), true_rtx)
4946            && rtx_equal_p (XEXP (cond, 1), false_rtx))
4947     return true_rtx;
4948
4949   /* Look for cases where we have (abs x) or (neg (abs X)).  */
4950
4951   if (GET_MODE_CLASS (mode) == MODE_INT
4952       && GET_CODE (false_rtx) == NEG
4953       && rtx_equal_p (true_rtx, XEXP (false_rtx, 0))
4954       && comparison_p
4955       && rtx_equal_p (true_rtx, XEXP (cond, 0))
4956       && ! side_effects_p (true_rtx))
4957     switch (true_code)
4958       {
4959       case GT:
4960       case GE:
4961         return simplify_gen_unary (ABS, mode, true_rtx, mode);
4962       case LT:
4963       case LE:
4964         return
4965           simplify_gen_unary (NEG, mode,
4966                               simplify_gen_unary (ABS, mode, true_rtx, mode),
4967                               mode);
4968       default:
4969         break;
4970       }
4971
4972   /* Look for MIN or MAX.  */
4973
4974   if ((! FLOAT_MODE_P (mode) || flag_unsafe_math_optimizations)
4975       && comparison_p
4976       && rtx_equal_p (XEXP (cond, 0), true_rtx)
4977       && rtx_equal_p (XEXP (cond, 1), false_rtx)
4978       && ! side_effects_p (cond))
4979     switch (true_code)
4980       {
4981       case GE:
4982       case GT:
4983         return simplify_gen_binary (SMAX, mode, true_rtx, false_rtx);
4984       case LE:
4985       case LT:
4986         return simplify_gen_binary (SMIN, mode, true_rtx, false_rtx);
4987       case GEU:
4988       case GTU:
4989         return simplify_gen_binary (UMAX, mode, true_rtx, false_rtx);
4990       case LEU:
4991       case LTU:
4992         return simplify_gen_binary (UMIN, mode, true_rtx, false_rtx);
4993       default:
4994         break;
4995       }
4996
4997   /* If we have (if_then_else COND (OP Z C1) Z) and OP is an identity when its
4998      second operand is zero, this can be done as (OP Z (mult COND C2)) where
4999      C2 = C1 * STORE_FLAG_VALUE. Similarly if OP has an outer ZERO_EXTEND or
5000      SIGN_EXTEND as long as Z is already extended (so we don't destroy it).
5001      We can do this kind of thing in some cases when STORE_FLAG_VALUE is
5002      neither 1 or -1, but it isn't worth checking for.  */
5003
5004   if ((STORE_FLAG_VALUE == 1 || STORE_FLAG_VALUE == -1)
5005       && comparison_p
5006       && GET_MODE_CLASS (mode) == MODE_INT
5007       && ! side_effects_p (x))
5008     {
5009       rtx t = make_compound_operation (true_rtx, SET);
5010       rtx f = make_compound_operation (false_rtx, SET);
5011       rtx cond_op0 = XEXP (cond, 0);
5012       rtx cond_op1 = XEXP (cond, 1);
5013       enum rtx_code op = UNKNOWN, extend_op = UNKNOWN;
5014       enum machine_mode m = mode;
5015       rtx z = 0, c1 = NULL_RTX;
5016
5017       if ((GET_CODE (t) == PLUS || GET_CODE (t) == MINUS
5018            || GET_CODE (t) == IOR || GET_CODE (t) == XOR
5019            || GET_CODE (t) == ASHIFT
5020            || GET_CODE (t) == LSHIFTRT || GET_CODE (t) == ASHIFTRT)
5021           && rtx_equal_p (XEXP (t, 0), f))
5022         c1 = XEXP (t, 1), op = GET_CODE (t), z = f;
5023
5024       /* If an identity-zero op is commutative, check whether there
5025          would be a match if we swapped the operands.  */
5026       else if ((GET_CODE (t) == PLUS || GET_CODE (t) == IOR
5027                 || GET_CODE (t) == XOR)
5028                && rtx_equal_p (XEXP (t, 1), f))
5029         c1 = XEXP (t, 0), op = GET_CODE (t), z = f;
5030       else if (GET_CODE (t) == SIGN_EXTEND
5031                && (GET_CODE (XEXP (t, 0)) == PLUS
5032                    || GET_CODE (XEXP (t, 0)) == MINUS
5033                    || GET_CODE (XEXP (t, 0)) == IOR
5034                    || GET_CODE (XEXP (t, 0)) == XOR
5035                    || GET_CODE (XEXP (t, 0)) == ASHIFT
5036                    || GET_CODE (XEXP (t, 0)) == LSHIFTRT
5037                    || GET_CODE (XEXP (t, 0)) == ASHIFTRT)
5038                && GET_CODE (XEXP (XEXP (t, 0), 0)) == SUBREG
5039                && subreg_lowpart_p (XEXP (XEXP (t, 0), 0))
5040                && rtx_equal_p (SUBREG_REG (XEXP (XEXP (t, 0), 0)), f)
5041                && (num_sign_bit_copies (f, GET_MODE (f))
5042                    > (unsigned int)
5043                      (GET_MODE_BITSIZE (mode)
5044                       - GET_MODE_BITSIZE (GET_MODE (XEXP (XEXP (t, 0), 0))))))
5045         {
5046           c1 = XEXP (XEXP (t, 0), 1); z = f; op = GET_CODE (XEXP (t, 0));
5047           extend_op = SIGN_EXTEND;
5048           m = GET_MODE (XEXP (t, 0));
5049         }
5050       else if (GET_CODE (t) == SIGN_EXTEND
5051                && (GET_CODE (XEXP (t, 0)) == PLUS
5052                    || GET_CODE (XEXP (t, 0)) == IOR
5053                    || GET_CODE (XEXP (t, 0)) == XOR)
5054                && GET_CODE (XEXP (XEXP (t, 0), 1)) == SUBREG
5055                && subreg_lowpart_p (XEXP (XEXP (t, 0), 1))
5056                && rtx_equal_p (SUBREG_REG (XEXP (XEXP (t, 0), 1)), f)
5057                && (num_sign_bit_copies (f, GET_MODE (f))
5058                    > (unsigned int)
5059                      (GET_MODE_BITSIZE (mode)
5060                       - GET_MODE_BITSIZE (GET_MODE (XEXP (XEXP (t, 0), 1))))))
5061         {
5062           c1 = XEXP (XEXP (t, 0), 0); z = f; op = GET_CODE (XEXP (t, 0));
5063           extend_op = SIGN_EXTEND;
5064           m = GET_MODE (XEXP (t, 0));
5065         }
5066       else if (GET_CODE (t) == ZERO_EXTEND
5067                && (GET_CODE (XEXP (t, 0)) == PLUS
5068                    || GET_CODE (XEXP (t, 0)) == MINUS
5069                    || GET_CODE (XEXP (t, 0)) == IOR
5070                    || GET_CODE (XEXP (t, 0)) == XOR
5071                    || GET_CODE (XEXP (t, 0)) == ASHIFT
5072                    || GET_CODE (XEXP (t, 0)) == LSHIFTRT
5073                    || GET_CODE (XEXP (t, 0)) == ASHIFTRT)
5074                && GET_CODE (XEXP (XEXP (t, 0), 0)) == SUBREG
5075                && GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT
5076                && subreg_lowpart_p (XEXP (XEXP (t, 0), 0))
5077                && rtx_equal_p (SUBREG_REG (XEXP (XEXP (t, 0), 0)), f)
5078                && ((nonzero_bits (f, GET_MODE (f))
5079                     & ~GET_MODE_MASK (GET_MODE (XEXP (XEXP (t, 0), 0))))
5080                    == 0))
5081         {
5082           c1 = XEXP (XEXP (t, 0), 1); z = f; op = GET_CODE (XEXP (t, 0));
5083           extend_op = ZERO_EXTEND;
5084           m = GET_MODE (XEXP (t, 0));
5085         }
5086       else if (GET_CODE (t) == ZERO_EXTEND
5087                && (GET_CODE (XEXP (t, 0)) == PLUS
5088                    || GET_CODE (XEXP (t, 0)) == IOR
5089                    || GET_CODE (XEXP (t, 0)) == XOR)
5090                && GET_CODE (XEXP (XEXP (t, 0), 1)) == SUBREG
5091                && GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT
5092                && subreg_lowpart_p (XEXP (XEXP (t, 0), 1))
5093                && rtx_equal_p (SUBREG_REG (XEXP (XEXP (t, 0), 1)), f)
5094                && ((nonzero_bits (f, GET_MODE (f))
5095                     & ~GET_MODE_MASK (GET_MODE (XEXP (XEXP (t, 0), 1))))
5096                    == 0))
5097         {
5098           c1 = XEXP (XEXP (t, 0), 0); z = f; op = GET_CODE (XEXP (t, 0));
5099           extend_op = ZERO_EXTEND;
5100           m = GET_MODE (XEXP (t, 0));
5101         }
5102
5103       if (z)
5104         {
5105           temp = subst (simplify_gen_relational (true_code, m, VOIDmode,
5106                                                  cond_op0, cond_op1),
5107                         pc_rtx, pc_rtx, 0, 0);
5108           temp = simplify_gen_binary (MULT, m, temp,
5109                                       simplify_gen_binary (MULT, m, c1,
5110                                                            const_true_rtx));
5111           temp = subst (temp, pc_rtx, pc_rtx, 0, 0);
5112           temp = simplify_gen_binary (op, m, gen_lowpart (m, z), temp);
5113
5114           if (extend_op != UNKNOWN)
5115             temp = simplify_gen_unary (extend_op, mode, temp, m);
5116
5117           return temp;
5118         }
5119     }
5120
5121   /* If we have (if_then_else (ne A 0) C1 0) and either A is known to be 0 or
5122      1 and C1 is a single bit or A is known to be 0 or -1 and C1 is the
5123      negation of a single bit, we can convert this operation to a shift.  We
5124      can actually do this more generally, but it doesn't seem worth it.  */
5125
5126   if (true_code == NE && XEXP (cond, 1) == const0_rtx
5127       && false_rtx == const0_rtx && GET_CODE (true_rtx) == CONST_INT
5128       && ((1 == nonzero_bits (XEXP (cond, 0), mode)
5129            && (i = exact_log2 (INTVAL (true_rtx))) >= 0)
5130           || ((num_sign_bit_copies (XEXP (cond, 0), mode)
5131                == GET_MODE_BITSIZE (mode))
5132               && (i = exact_log2 (-INTVAL (true_rtx))) >= 0)))
5133     return
5134       simplify_shift_const (NULL_RTX, ASHIFT, mode,
5135                             gen_lowpart (mode, XEXP (cond, 0)), i);
5136
5137   /* (IF_THEN_ELSE (NE REG 0) (0) (8)) is REG for nonzero_bits (REG) == 8.  */
5138   if (true_code == NE && XEXP (cond, 1) == const0_rtx
5139       && false_rtx == const0_rtx && GET_CODE (true_rtx) == CONST_INT
5140       && GET_MODE (XEXP (cond, 0)) == mode
5141       && (INTVAL (true_rtx) & GET_MODE_MASK (mode))
5142           == nonzero_bits (XEXP (cond, 0), mode)
5143       && (i = exact_log2 (INTVAL (true_rtx) & GET_MODE_MASK (mode))) >= 0)
5144     return XEXP (cond, 0);
5145
5146   return x;
5147 }
5148 \f
5149 /* Simplify X, a SET expression.  Return the new expression.  */
5150
5151 static rtx
5152 simplify_set (rtx x)
5153 {
5154   rtx src = SET_SRC (x);
5155   rtx dest = SET_DEST (x);
5156   enum machine_mode mode
5157     = GET_MODE (src) != VOIDmode ? GET_MODE (src) : GET_MODE (dest);
5158   rtx other_insn;
5159   rtx *cc_use;
5160
5161   /* (set (pc) (return)) gets written as (return).  */
5162   if (GET_CODE (dest) == PC && GET_CODE (src) == RETURN)
5163     return src;
5164
5165   /* Now that we know for sure which bits of SRC we are using, see if we can
5166      simplify the expression for the object knowing that we only need the
5167      low-order bits.  */
5168
5169   if (GET_MODE_CLASS (mode) == MODE_INT
5170       && GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT)
5171     {
5172       src = force_to_mode (src, mode, ~(HOST_WIDE_INT) 0, 0);
5173       SUBST (SET_SRC (x), src);
5174     }
5175
5176   /* If we are setting CC0 or if the source is a COMPARE, look for the use of
5177      the comparison result and try to simplify it unless we already have used
5178      undobuf.other_insn.  */
5179   if ((GET_MODE_CLASS (mode) == MODE_CC
5180        || GET_CODE (src) == COMPARE
5181        || CC0_P (dest))
5182       && (cc_use = find_single_use (dest, subst_insn, &other_insn)) != 0
5183       && (undobuf.other_insn == 0 || other_insn == undobuf.other_insn)
5184       && COMPARISON_P (*cc_use)
5185       && rtx_equal_p (XEXP (*cc_use, 0), dest))
5186     {
5187       enum rtx_code old_code = GET_CODE (*cc_use);
5188       enum rtx_code new_code;
5189       rtx op0, op1, tmp;
5190       int other_changed = 0;
5191       enum machine_mode compare_mode = GET_MODE (dest);
5192
5193       if (GET_CODE (src) == COMPARE)
5194         op0 = XEXP (src, 0), op1 = XEXP (src, 1);
5195       else
5196         op0 = src, op1 = CONST0_RTX (GET_MODE (src));
5197
5198       tmp = simplify_relational_operation (old_code, compare_mode, VOIDmode,
5199                                            op0, op1);
5200       if (!tmp)
5201         new_code = old_code;
5202       else if (!CONSTANT_P (tmp))
5203         {
5204           new_code = GET_CODE (tmp);
5205           op0 = XEXP (tmp, 0);
5206           op1 = XEXP (tmp, 1);
5207         }
5208       else
5209         {
5210           rtx pat = PATTERN (other_insn);
5211           undobuf.other_insn = other_insn;
5212           SUBST (*cc_use, tmp);
5213
5214           /* Attempt to simplify CC user.  */
5215           if (GET_CODE (pat) == SET)
5216             {
5217               rtx new = simplify_rtx (SET_SRC (pat));
5218               if (new != NULL_RTX)
5219                 SUBST (SET_SRC (pat), new);
5220             }
5221
5222           /* Convert X into a no-op move.  */
5223           SUBST (SET_DEST (x), pc_rtx);
5224           SUBST (SET_SRC (x), pc_rtx);
5225           return x;
5226         }
5227
5228       /* Simplify our comparison, if possible.  */
5229       new_code = simplify_comparison (new_code, &op0, &op1);
5230
5231 #ifdef SELECT_CC_MODE
5232       /* If this machine has CC modes other than CCmode, check to see if we
5233          need to use a different CC mode here.  */
5234       if (GET_MODE_CLASS (GET_MODE (op0)) == MODE_CC)
5235         compare_mode = GET_MODE (op0);
5236       else
5237         compare_mode = SELECT_CC_MODE (new_code, op0, op1);
5238
5239 #ifndef HAVE_cc0
5240       /* If the mode changed, we have to change SET_DEST, the mode in the
5241          compare, and the mode in the place SET_DEST is used.  If SET_DEST is
5242          a hard register, just build new versions with the proper mode.  If it
5243          is a pseudo, we lose unless it is only time we set the pseudo, in
5244          which case we can safely change its mode.  */
5245       if (compare_mode != GET_MODE (dest))
5246         {
5247           if (can_change_dest_mode (dest, 0, compare_mode))
5248             {
5249               unsigned int regno = REGNO (dest);
5250               rtx new_dest;
5251
5252               if (regno < FIRST_PSEUDO_REGISTER)
5253                 new_dest = gen_rtx_REG (compare_mode, regno);
5254               else
5255                 {
5256                   SUBST_MODE (regno_reg_rtx[regno], compare_mode);
5257                   new_dest = regno_reg_rtx[regno];
5258                 }
5259
5260               SUBST (SET_DEST (x), new_dest);
5261               SUBST (XEXP (*cc_use, 0), new_dest);
5262               other_changed = 1;
5263
5264               dest = new_dest;
5265             }
5266         }
5267 #endif  /* cc0 */
5268 #endif  /* SELECT_CC_MODE */
5269
5270       /* If the code changed, we have to build a new comparison in
5271          undobuf.other_insn.  */
5272       if (new_code != old_code)
5273         {
5274           int other_changed_previously = other_changed;
5275           unsigned HOST_WIDE_INT mask;
5276
5277           SUBST (*cc_use, gen_rtx_fmt_ee (new_code, GET_MODE (*cc_use),
5278                                           dest, const0_rtx));
5279           other_changed = 1;
5280
5281           /* If the only change we made was to change an EQ into an NE or
5282              vice versa, OP0 has only one bit that might be nonzero, and OP1
5283              is zero, check if changing the user of the condition code will
5284              produce a valid insn.  If it won't, we can keep the original code
5285              in that insn by surrounding our operation with an XOR.  */
5286
5287           if (((old_code == NE && new_code == EQ)
5288                || (old_code == EQ && new_code == NE))
5289               && ! other_changed_previously && op1 == const0_rtx
5290               && GET_MODE_BITSIZE (GET_MODE (op0)) <= HOST_BITS_PER_WIDE_INT
5291               && exact_log2 (mask = nonzero_bits (op0, GET_MODE (op0))) >= 0)
5292             {
5293               rtx pat = PATTERN (other_insn), note = 0;
5294
5295               if ((recog_for_combine (&pat, other_insn, &note) < 0
5296                    && ! check_asm_operands (pat)))
5297                 {
5298                   PUT_CODE (*cc_use, old_code);
5299                   other_changed = 0;
5300
5301                   op0 = simplify_gen_binary (XOR, GET_MODE (op0),
5302                                              op0, GEN_INT (mask));
5303                 }
5304             }
5305         }
5306
5307       if (other_changed)
5308         undobuf.other_insn = other_insn;
5309
5310 #ifdef HAVE_cc0
5311       /* If we are now comparing against zero, change our source if
5312          needed.  If we do not use cc0, we always have a COMPARE.  */
5313       if (op1 == const0_rtx && dest == cc0_rtx)
5314         {
5315           SUBST (SET_SRC (x), op0);
5316           src = op0;
5317         }
5318       else
5319 #endif
5320
5321       /* Otherwise, if we didn't previously have a COMPARE in the
5322          correct mode, we need one.  */
5323       if (GET_CODE (src) != COMPARE || GET_MODE (src) != compare_mode)
5324         {
5325           SUBST (SET_SRC (x), gen_rtx_COMPARE (compare_mode, op0, op1));
5326           src = SET_SRC (x);
5327         }
5328       else if (GET_MODE (op0) == compare_mode && op1 == const0_rtx)
5329         {
5330           SUBST(SET_SRC (x), op0);
5331           src = SET_SRC (x);
5332         }
5333       else
5334         {
5335           /* Otherwise, update the COMPARE if needed.  */
5336           SUBST (XEXP (src, 0), op0);
5337           SUBST (XEXP (src, 1), op1);
5338         }
5339     }
5340   else
5341     {
5342       /* Get SET_SRC in a form where we have placed back any
5343          compound expressions.  Then do the checks below.  */
5344       src = make_compound_operation (src, SET);
5345       SUBST (SET_SRC (x), src);
5346     }
5347
5348   /* If we have (set x (subreg:m1 (op:m2 ...) 0)) with OP being some operation,
5349      and X being a REG or (subreg (reg)), we may be able to convert this to
5350      (set (subreg:m2 x) (op)).
5351
5352      We can always do this if M1 is narrower than M2 because that means that
5353      we only care about the low bits of the result.
5354
5355      However, on machines without WORD_REGISTER_OPERATIONS defined, we cannot
5356      perform a narrower operation than requested since the high-order bits will
5357      be undefined.  On machine where it is defined, this transformation is safe
5358      as long as M1 and M2 have the same number of words.  */
5359
5360   if (GET_CODE (src) == SUBREG && subreg_lowpart_p (src)
5361       && !OBJECT_P (SUBREG_REG (src))
5362       && (((GET_MODE_SIZE (GET_MODE (src)) + (UNITS_PER_WORD - 1))
5363            / UNITS_PER_WORD)
5364           == ((GET_MODE_SIZE (GET_MODE (SUBREG_REG (src)))
5365                + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD))
5366 #ifndef WORD_REGISTER_OPERATIONS
5367       && (GET_MODE_SIZE (GET_MODE (src))
5368         < GET_MODE_SIZE (GET_MODE (SUBREG_REG (src))))
5369 #endif
5370 #ifdef CANNOT_CHANGE_MODE_CLASS
5371       && ! (REG_P (dest) && REGNO (dest) < FIRST_PSEUDO_REGISTER
5372             && REG_CANNOT_CHANGE_MODE_P (REGNO (dest),
5373                                          GET_MODE (SUBREG_REG (src)),
5374                                          GET_MODE (src)))
5375 #endif
5376       && (REG_P (dest)
5377           || (GET_CODE (dest) == SUBREG
5378               && REG_P (SUBREG_REG (dest)))))
5379     {
5380       SUBST (SET_DEST (x),
5381              gen_lowpart (GET_MODE (SUBREG_REG (src)),
5382                                       dest));
5383       SUBST (SET_SRC (x), SUBREG_REG (src));
5384
5385       src = SET_SRC (x), dest = SET_DEST (x);
5386     }
5387
5388 #ifdef HAVE_cc0
5389   /* If we have (set (cc0) (subreg ...)), we try to remove the subreg
5390      in SRC.  */
5391   if (dest == cc0_rtx
5392       && GET_CODE (src) == SUBREG
5393       && subreg_lowpart_p (src)
5394       && (GET_MODE_BITSIZE (GET_MODE (src))
5395           < GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (src)))))
5396     {
5397       rtx inner = SUBREG_REG (src);
5398       enum machine_mode inner_mode = GET_MODE (inner);
5399
5400       /* Here we make sure that we don't have a sign bit on.  */
5401       if (GET_MODE_BITSIZE (inner_mode) <= HOST_BITS_PER_WIDE_INT
5402           && (nonzero_bits (inner, inner_mode)
5403               < ((unsigned HOST_WIDE_INT) 1
5404                  << (GET_MODE_BITSIZE (GET_MODE (src)) - 1))))
5405         {
5406           SUBST (SET_SRC (x), inner);
5407           src = SET_SRC (x);
5408         }
5409     }
5410 #endif
5411
5412 #ifdef LOAD_EXTEND_OP
5413   /* If we have (set FOO (subreg:M (mem:N BAR) 0)) with M wider than N, this
5414      would require a paradoxical subreg.  Replace the subreg with a
5415      zero_extend to avoid the reload that would otherwise be required.  */
5416
5417   if (GET_CODE (src) == SUBREG && subreg_lowpart_p (src)
5418       && LOAD_EXTEND_OP (GET_MODE (SUBREG_REG (src))) != UNKNOWN
5419       && SUBREG_BYTE (src) == 0
5420       && (GET_MODE_SIZE (GET_MODE (src))
5421           > GET_MODE_SIZE (GET_MODE (SUBREG_REG (src))))
5422       && MEM_P (SUBREG_REG (src)))
5423     {
5424       SUBST (SET_SRC (x),
5425              gen_rtx_fmt_e (LOAD_EXTEND_OP (GET_MODE (SUBREG_REG (src))),
5426                             GET_MODE (src), SUBREG_REG (src)));
5427
5428       src = SET_SRC (x);
5429     }
5430 #endif
5431
5432   /* If we don't have a conditional move, SET_SRC is an IF_THEN_ELSE, and we
5433      are comparing an item known to be 0 or -1 against 0, use a logical
5434      operation instead. Check for one of the arms being an IOR of the other
5435      arm with some value.  We compute three terms to be IOR'ed together.  In
5436      practice, at most two will be nonzero.  Then we do the IOR's.  */
5437
5438   if (GET_CODE (dest) != PC
5439       && GET_CODE (src) == IF_THEN_ELSE
5440       && GET_MODE_CLASS (GET_MODE (src)) == MODE_INT
5441       && (GET_CODE (XEXP (src, 0)) == EQ || GET_CODE (XEXP (src, 0)) == NE)
5442       && XEXP (XEXP (src, 0), 1) == const0_rtx
5443       && GET_MODE (src) == GET_MODE (XEXP (XEXP (src, 0), 0))
5444 #ifdef HAVE_conditional_move
5445       && ! can_conditionally_move_p (GET_MODE (src))
5446 #endif
5447       && (num_sign_bit_copies (XEXP (XEXP (src, 0), 0),
5448                                GET_MODE (XEXP (XEXP (src, 0), 0)))
5449           == GET_MODE_BITSIZE (GET_MODE (XEXP (XEXP (src, 0), 0))))
5450       && ! side_effects_p (src))
5451     {
5452       rtx true_rtx = (GET_CODE (XEXP (src, 0)) == NE
5453                       ? XEXP (src, 1) : XEXP (src, 2));
5454       rtx false_rtx = (GET_CODE (XEXP (src, 0)) == NE
5455                    ? XEXP (src, 2) : XEXP (src, 1));
5456       rtx term1 = const0_rtx, term2, term3;
5457
5458       if (GET_CODE (true_rtx) == IOR
5459           && rtx_equal_p (XEXP (true_rtx, 0), false_rtx))
5460         term1 = false_rtx, true_rtx = XEXP (true_rtx, 1), false_rtx = const0_rtx;
5461       else if (GET_CODE (true_rtx) == IOR
5462                && rtx_equal_p (XEXP (true_rtx, 1), false_rtx))
5463         term1 = false_rtx, true_rtx = XEXP (true_rtx, 0), false_rtx = const0_rtx;
5464       else if (GET_CODE (false_rtx) == IOR
5465                && rtx_equal_p (XEXP (false_rtx, 0), true_rtx))
5466         term1 = true_rtx, false_rtx = XEXP (false_rtx, 1), true_rtx = const0_rtx;
5467       else if (GET_CODE (false_rtx) == IOR
5468                && rtx_equal_p (XEXP (false_rtx, 1), true_rtx))
5469         term1 = true_rtx, false_rtx = XEXP (false_rtx, 0), true_rtx = const0_rtx;
5470
5471       term2 = simplify_gen_binary (AND, GET_MODE (src),
5472                                    XEXP (XEXP (src, 0), 0), true_rtx);
5473       term3 = simplify_gen_binary (AND, GET_MODE (src),
5474                                    simplify_gen_unary (NOT, GET_MODE (src),
5475                                                        XEXP (XEXP (src, 0), 0),
5476                                                        GET_MODE (src)),
5477                                    false_rtx);
5478
5479       SUBST (SET_SRC (x),
5480              simplify_gen_binary (IOR, GET_MODE (src),
5481                                   simplify_gen_binary (IOR, GET_MODE (src),
5482                                                        term1, term2),
5483                                   term3));
5484
5485       src = SET_SRC (x);
5486     }
5487
5488   /* If either SRC or DEST is a CLOBBER of (const_int 0), make this
5489      whole thing fail.  */
5490   if (GET_CODE (src) == CLOBBER && XEXP (src, 0) == const0_rtx)
5491     return src;
5492   else if (GET_CODE (dest) == CLOBBER && XEXP (dest, 0) == const0_rtx)
5493     return dest;
5494   else
5495     /* Convert this into a field assignment operation, if possible.  */
5496     return make_field_assignment (x);
5497 }
5498 \f
5499 /* Simplify, X, and AND, IOR, or XOR operation, and return the simplified
5500    result.  */
5501
5502 static rtx
5503 simplify_logical (rtx x)
5504 {
5505   enum machine_mode mode = GET_MODE (x);
5506   rtx op0 = XEXP (x, 0);
5507   rtx op1 = XEXP (x, 1);
5508
5509   switch (GET_CODE (x))
5510     {
5511     case AND:
5512       /* We can call simplify_and_const_int only if we don't lose
5513          any (sign) bits when converting INTVAL (op1) to
5514          "unsigned HOST_WIDE_INT".  */
5515       if (GET_CODE (op1) == CONST_INT
5516           && (GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT
5517               || INTVAL (op1) > 0))
5518         {
5519           x = simplify_and_const_int (x, mode, op0, INTVAL (op1));
5520           if (GET_CODE (x) != AND)
5521             return x;
5522
5523           op0 = XEXP (x, 0);
5524           op1 = XEXP (x, 1);
5525         }
5526
5527       /* If we have any of (and (ior A B) C) or (and (xor A B) C),
5528          apply the distributive law and then the inverse distributive
5529          law to see if things simplify.  */
5530       if (GET_CODE (op0) == IOR || GET_CODE (op0) == XOR)
5531         {
5532           rtx result = distribute_and_simplify_rtx (x, 0);
5533           if (result)
5534             return result;
5535         }
5536       if (GET_CODE (op1) == IOR || GET_CODE (op1) == XOR)
5537         {
5538           rtx result = distribute_and_simplify_rtx (x, 1);
5539           if (result)
5540             return result;
5541         }
5542       break;
5543
5544     case IOR:
5545       /* If we have (ior (and A B) C), apply the distributive law and then
5546          the inverse distributive law to see if things simplify.  */
5547
5548       if (GET_CODE (op0) == AND)
5549         {
5550           rtx result = distribute_and_simplify_rtx (x, 0);
5551           if (result)
5552             return result;
5553         }
5554
5555       if (GET_CODE (op1) == AND)
5556         {
5557           rtx result = distribute_and_simplify_rtx (x, 1);
5558           if (result)
5559             return result;
5560         }
5561       break;
5562
5563     default:
5564       gcc_unreachable ();
5565     }
5566
5567   return x;
5568 }
5569 \f
5570 /* We consider ZERO_EXTRACT, SIGN_EXTRACT, and SIGN_EXTEND as "compound
5571    operations" because they can be replaced with two more basic operations.
5572    ZERO_EXTEND is also considered "compound" because it can be replaced with
5573    an AND operation, which is simpler, though only one operation.
5574
5575    The function expand_compound_operation is called with an rtx expression
5576    and will convert it to the appropriate shifts and AND operations,
5577    simplifying at each stage.
5578
5579    The function make_compound_operation is called to convert an expression
5580    consisting of shifts and ANDs into the equivalent compound expression.
5581    It is the inverse of this function, loosely speaking.  */
5582
5583 static rtx
5584 expand_compound_operation (rtx x)
5585 {
5586   unsigned HOST_WIDE_INT pos = 0, len;
5587   int unsignedp = 0;
5588   unsigned int modewidth;
5589   rtx tem;
5590
5591   switch (GET_CODE (x))
5592     {
5593     case ZERO_EXTEND:
5594       unsignedp = 1;
5595     case SIGN_EXTEND:
5596       /* We can't necessarily use a const_int for a multiword mode;
5597          it depends on implicitly extending the value.
5598          Since we don't know the right way to extend it,
5599          we can't tell whether the implicit way is right.
5600
5601          Even for a mode that is no wider than a const_int,
5602          we can't win, because we need to sign extend one of its bits through
5603          the rest of it, and we don't know which bit.  */
5604       if (GET_CODE (XEXP (x, 0)) == CONST_INT)
5605         return x;
5606
5607       /* Return if (subreg:MODE FROM 0) is not a safe replacement for
5608          (zero_extend:MODE FROM) or (sign_extend:MODE FROM).  It is for any MEM
5609          because (SUBREG (MEM...)) is guaranteed to cause the MEM to be
5610          reloaded. If not for that, MEM's would very rarely be safe.
5611
5612          Reject MODEs bigger than a word, because we might not be able
5613          to reference a two-register group starting with an arbitrary register
5614          (and currently gen_lowpart might crash for a SUBREG).  */
5615
5616       if (GET_MODE_SIZE (GET_MODE (XEXP (x, 0))) > UNITS_PER_WORD)
5617         return x;
5618
5619       /* Reject MODEs that aren't scalar integers because turning vector
5620          or complex modes into shifts causes problems.  */
5621
5622       if (! SCALAR_INT_MODE_P (GET_MODE (XEXP (x, 0))))
5623         return x;
5624
5625       len = GET_MODE_BITSIZE (GET_MODE (XEXP (x, 0)));
5626       /* If the inner object has VOIDmode (the only way this can happen
5627          is if it is an ASM_OPERANDS), we can't do anything since we don't
5628          know how much masking to do.  */
5629       if (len == 0)
5630         return x;
5631
5632       break;
5633
5634     case ZERO_EXTRACT:
5635       unsignedp = 1;
5636
5637       /* ... fall through ...  */
5638
5639     case SIGN_EXTRACT:
5640       /* If the operand is a CLOBBER, just return it.  */
5641       if (GET_CODE (XEXP (x, 0)) == CLOBBER)
5642         return XEXP (x, 0);
5643
5644       if (GET_CODE (XEXP (x, 1)) != CONST_INT
5645           || GET_CODE (XEXP (x, 2)) != CONST_INT
5646           || GET_MODE (XEXP (x, 0)) == VOIDmode)
5647         return x;
5648
5649       /* Reject MODEs that aren't scalar integers because turning vector
5650          or complex modes into shifts causes problems.  */
5651
5652       if (! SCALAR_INT_MODE_P (GET_MODE (XEXP (x, 0))))
5653         return x;
5654
5655       len = INTVAL (XEXP (x, 1));
5656       pos = INTVAL (XEXP (x, 2));
5657
5658       /* This should stay within the object being extracted, fail otherwise.  */
5659       if (len + pos > GET_MODE_BITSIZE (GET_MODE (XEXP (x, 0))))
5660         return x;
5661
5662       if (BITS_BIG_ENDIAN)
5663         pos = GET_MODE_BITSIZE (GET_MODE (XEXP (x, 0))) - len - pos;
5664
5665       break;
5666
5667     default:
5668       return x;
5669     }
5670   /* Convert sign extension to zero extension, if we know that the high
5671      bit is not set, as this is easier to optimize.  It will be converted
5672      back to cheaper alternative in make_extraction.  */
5673   if (GET_CODE (x) == SIGN_EXTEND
5674       && (GET_MODE_BITSIZE (GET_MODE (x)) <= HOST_BITS_PER_WIDE_INT
5675           && ((nonzero_bits (XEXP (x, 0), GET_MODE (XEXP (x, 0)))
5676                 & ~(((unsigned HOST_WIDE_INT)
5677                       GET_MODE_MASK (GET_MODE (XEXP (x, 0))))
5678                      >> 1))
5679                == 0)))
5680     {
5681       rtx temp = gen_rtx_ZERO_EXTEND (GET_MODE (x), XEXP (x, 0));
5682       rtx temp2 = expand_compound_operation (temp);
5683
5684       /* Make sure this is a profitable operation.  */
5685       if (rtx_cost (x, SET) > rtx_cost (temp2, SET))
5686        return temp2;
5687       else if (rtx_cost (x, SET) > rtx_cost (temp, SET))
5688        return temp;
5689       else
5690        return x;
5691     }
5692
5693   /* We can optimize some special cases of ZERO_EXTEND.  */
5694   if (GET_CODE (x) == ZERO_EXTEND)
5695     {
5696       /* (zero_extend:DI (truncate:SI foo:DI)) is just foo:DI if we
5697          know that the last value didn't have any inappropriate bits
5698          set.  */
5699       if (GET_CODE (XEXP (x, 0)) == TRUNCATE
5700           && GET_MODE (XEXP (XEXP (x, 0), 0)) == GET_MODE (x)
5701           && GET_MODE_BITSIZE (GET_MODE (x)) <= HOST_BITS_PER_WIDE_INT
5702           && (nonzero_bits (XEXP (XEXP (x, 0), 0), GET_MODE (x))
5703               & ~GET_MODE_MASK (GET_MODE (XEXP (x, 0)))) == 0)
5704         return XEXP (XEXP (x, 0), 0);
5705
5706       /* Likewise for (zero_extend:DI (subreg:SI foo:DI 0)).  */
5707       if (GET_CODE (XEXP (x, 0)) == SUBREG
5708           && GET_MODE (SUBREG_REG (XEXP (x, 0))) == GET_MODE (x)
5709           && subreg_lowpart_p (XEXP (x, 0))
5710           && GET_MODE_BITSIZE (GET_MODE (x)) <= HOST_BITS_PER_WIDE_INT
5711           && (nonzero_bits (SUBREG_REG (XEXP (x, 0)), GET_MODE (x))
5712               & ~GET_MODE_MASK (GET_MODE (XEXP (x, 0)))) == 0)
5713         return SUBREG_REG (XEXP (x, 0));
5714
5715       /* (zero_extend:DI (truncate:SI foo:DI)) is just foo:DI when foo
5716          is a comparison and STORE_FLAG_VALUE permits.  This is like
5717          the first case, but it works even when GET_MODE (x) is larger
5718          than HOST_WIDE_INT.  */
5719       if (GET_CODE (XEXP (x, 0)) == TRUNCATE
5720           && GET_MODE (XEXP (XEXP (x, 0), 0)) == GET_MODE (x)
5721           && COMPARISON_P (XEXP (XEXP (x, 0), 0))
5722           && (GET_MODE_BITSIZE (GET_MODE (XEXP (x, 0)))
5723               <= HOST_BITS_PER_WIDE_INT)
5724           && ((HOST_WIDE_INT) STORE_FLAG_VALUE
5725               & ~GET_MODE_MASK (GET_MODE (XEXP (x, 0)))) == 0)
5726         return XEXP (XEXP (x, 0), 0);
5727
5728       /* Likewise for (zero_extend:DI (subreg:SI foo:DI 0)).  */
5729       if (GET_CODE (XEXP (x, 0)) == SUBREG
5730           && GET_MODE (SUBREG_REG (XEXP (x, 0))) == GET_MODE (x)
5731           && subreg_lowpart_p (XEXP (x, 0))
5732           && COMPARISON_P (SUBREG_REG (XEXP (x, 0)))
5733           && (GET_MODE_BITSIZE (GET_MODE (XEXP (x, 0)))
5734               <= HOST_BITS_PER_WIDE_INT)
5735           && ((HOST_WIDE_INT) STORE_FLAG_VALUE
5736               & ~GET_MODE_MASK (GET_MODE (XEXP (x, 0)))) == 0)
5737         return SUBREG_REG (XEXP (x, 0));
5738
5739     }
5740
5741   /* If we reach here, we want to return a pair of shifts.  The inner
5742      shift is a left shift of BITSIZE - POS - LEN bits.  The outer
5743      shift is a right shift of BITSIZE - LEN bits.  It is arithmetic or
5744      logical depending on the value of UNSIGNEDP.
5745
5746      If this was a ZERO_EXTEND or ZERO_EXTRACT, this pair of shifts will be
5747      converted into an AND of a shift.
5748
5749      We must check for the case where the left shift would have a negative
5750      count.  This can happen in a case like (x >> 31) & 255 on machines
5751      that can't shift by a constant.  On those machines, we would first
5752      combine the shift with the AND to produce a variable-position
5753      extraction.  Then the constant of 31 would be substituted in to produce
5754      a such a position.  */
5755
5756   modewidth = GET_MODE_BITSIZE (GET_MODE (x));
5757   if (modewidth + len >= pos)
5758     {
5759       enum machine_mode mode = GET_MODE (x);
5760       tem = gen_lowpart (mode, XEXP (x, 0));
5761       if (!tem || GET_CODE (tem) == CLOBBER)
5762         return x;
5763       tem = simplify_shift_const (NULL_RTX, ASHIFT, mode,
5764                                   tem, modewidth - pos - len);
5765       tem = simplify_shift_const (NULL_RTX, unsignedp ? LSHIFTRT : ASHIFTRT,
5766                                   mode, tem, modewidth - len);
5767     }
5768   else if (unsignedp && len < HOST_BITS_PER_WIDE_INT)
5769     tem = simplify_and_const_int (NULL_RTX, GET_MODE (x),
5770                                   simplify_shift_const (NULL_RTX, LSHIFTRT,
5771                                                         GET_MODE (x),
5772                                                         XEXP (x, 0), pos),
5773                                   ((HOST_WIDE_INT) 1 << len) - 1);
5774   else
5775     /* Any other cases we can't handle.  */
5776     return x;
5777
5778   /* If we couldn't do this for some reason, return the original
5779      expression.  */
5780   if (GET_CODE (tem) == CLOBBER)
5781     return x;
5782
5783   return tem;
5784 }
5785 \f
5786 /* X is a SET which contains an assignment of one object into
5787    a part of another (such as a bit-field assignment, STRICT_LOW_PART,
5788    or certain SUBREGS). If possible, convert it into a series of
5789    logical operations.
5790
5791    We half-heartedly support variable positions, but do not at all
5792    support variable lengths.  */
5793
5794 static rtx
5795 expand_field_assignment (rtx x)
5796 {
5797   rtx inner;
5798   rtx pos;                      /* Always counts from low bit.  */
5799   int len;
5800   rtx mask, cleared, masked;
5801   enum machine_mode compute_mode;
5802
5803   /* Loop until we find something we can't simplify.  */
5804   while (1)
5805     {
5806       if (GET_CODE (SET_DEST (x)) == STRICT_LOW_PART
5807           && GET_CODE (XEXP (SET_DEST (x), 0)) == SUBREG)
5808         {
5809           inner = SUBREG_REG (XEXP (SET_DEST (x), 0));
5810           len = GET_MODE_BITSIZE (GET_MODE (XEXP (SET_DEST (x), 0)));
5811           pos = GEN_INT (subreg_lsb (XEXP (SET_DEST (x), 0)));
5812         }
5813       else if (GET_CODE (SET_DEST (x)) == ZERO_EXTRACT
5814                && GET_CODE (XEXP (SET_DEST (x), 1)) == CONST_INT)
5815         {
5816           inner = XEXP (SET_DEST (x), 0);
5817           len = INTVAL (XEXP (SET_DEST (x), 1));
5818           pos = XEXP (SET_DEST (x), 2);
5819
5820           /* A constant position should stay within the width of INNER.  */
5821           if (GET_CODE (pos) == CONST_INT
5822               && INTVAL (pos) + len > GET_MODE_BITSIZE (GET_MODE (inner)))
5823             break;
5824
5825           if (BITS_BIG_ENDIAN)
5826             {
5827               if (GET_CODE (pos) == CONST_INT)
5828                 pos = GEN_INT (GET_MODE_BITSIZE (GET_MODE (inner)) - len
5829                                - INTVAL (pos));
5830               else if (GET_CODE (pos) == MINUS
5831                        && GET_CODE (XEXP (pos, 1)) == CONST_INT
5832                        && (INTVAL (XEXP (pos, 1))
5833                            == GET_MODE_BITSIZE (GET_MODE (inner)) - len))
5834                 /* If position is ADJUST - X, new position is X.  */
5835                 pos = XEXP (pos, 0);
5836               else
5837                 pos = simplify_gen_binary (MINUS, GET_MODE (pos),
5838                                            GEN_INT (GET_MODE_BITSIZE (
5839                                                     GET_MODE (inner))
5840                                                     - len),
5841                                            pos);
5842             }
5843         }
5844
5845       /* A SUBREG between two modes that occupy the same numbers of words
5846          can be done by moving the SUBREG to the source.  */
5847       else if (GET_CODE (SET_DEST (x)) == SUBREG
5848                /* We need SUBREGs to compute nonzero_bits properly.  */
5849                && nonzero_sign_valid
5850                && (((GET_MODE_SIZE (GET_MODE (SET_DEST (x)))
5851                      + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD)
5852                    == ((GET_MODE_SIZE (GET_MODE (SUBREG_REG (SET_DEST (x))))
5853                         + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD)))
5854         {
5855           x = gen_rtx_SET (VOIDmode, SUBREG_REG (SET_DEST (x)),
5856                            gen_lowpart
5857                            (GET_MODE (SUBREG_REG (SET_DEST (x))),
5858                             SET_SRC (x)));
5859           continue;
5860         }
5861       else
5862         break;
5863
5864       while (GET_CODE (inner) == SUBREG && subreg_lowpart_p (inner))
5865         inner = SUBREG_REG (inner);
5866
5867       compute_mode = GET_MODE (inner);
5868
5869       /* Don't attempt bitwise arithmetic on non scalar integer modes.  */
5870       if (! SCALAR_INT_MODE_P (compute_mode))
5871         {
5872           enum machine_mode imode;
5873
5874           /* Don't do anything for vector or complex integral types.  */
5875           if (! FLOAT_MODE_P (compute_mode))
5876             break;
5877
5878           /* Try to find an integral mode to pun with.  */
5879           imode = mode_for_size (GET_MODE_BITSIZE (compute_mode), MODE_INT, 0);
5880           if (imode == BLKmode)
5881             break;
5882
5883           compute_mode = imode;
5884           inner = gen_lowpart (imode, inner);
5885         }
5886
5887       /* Compute a mask of LEN bits, if we can do this on the host machine.  */
5888       if (len >= HOST_BITS_PER_WIDE_INT)
5889         break;
5890
5891       /* Now compute the equivalent expression.  Make a copy of INNER
5892          for the SET_DEST in case it is a MEM into which we will substitute;
5893          we don't want shared RTL in that case.  */
5894       mask = GEN_INT (((HOST_WIDE_INT) 1 << len) - 1);
5895       cleared = simplify_gen_binary (AND, compute_mode,
5896                                      simplify_gen_unary (NOT, compute_mode,
5897                                        simplify_gen_binary (ASHIFT,
5898                                                             compute_mode,
5899                                                             mask, pos),
5900                                        compute_mode),
5901                                      inner);
5902       masked = simplify_gen_binary (ASHIFT, compute_mode,
5903                                     simplify_gen_binary (
5904                                       AND, compute_mode,
5905                                       gen_lowpart (compute_mode, SET_SRC (x)),
5906                                       mask),
5907                                     pos);
5908
5909       x = gen_rtx_SET (VOIDmode, copy_rtx (inner),
5910                        simplify_gen_binary (IOR, compute_mode,
5911                                             cleared, masked));
5912     }
5913
5914   return x;
5915 }
5916 \f
5917 /* Return an RTX for a reference to LEN bits of INNER.  If POS_RTX is nonzero,
5918    it is an RTX that represents a variable starting position; otherwise,
5919    POS is the (constant) starting bit position (counted from the LSB).
5920
5921    UNSIGNEDP is nonzero for an unsigned reference and zero for a
5922    signed reference.
5923
5924    IN_DEST is nonzero if this is a reference in the destination of a
5925    SET.  This is used when a ZERO_ or SIGN_EXTRACT isn't needed.  If nonzero,
5926    a STRICT_LOW_PART will be used, if zero, ZERO_EXTEND or SIGN_EXTEND will
5927    be used.
5928
5929    IN_COMPARE is nonzero if we are in a COMPARE.  This means that a
5930    ZERO_EXTRACT should be built even for bits starting at bit 0.
5931
5932    MODE is the desired mode of the result (if IN_DEST == 0).
5933
5934    The result is an RTX for the extraction or NULL_RTX if the target
5935    can't handle it.  */
5936
5937 static rtx
5938 make_extraction (enum machine_mode mode, rtx inner, HOST_WIDE_INT pos,
5939                  rtx pos_rtx, unsigned HOST_WIDE_INT len, int unsignedp,
5940                  int in_dest, int in_compare)
5941 {
5942   /* This mode describes the size of the storage area
5943      to fetch the overall value from.  Within that, we
5944      ignore the POS lowest bits, etc.  */
5945   enum machine_mode is_mode = GET_MODE (inner);
5946   enum machine_mode inner_mode;
5947   enum machine_mode wanted_inner_mode;
5948   enum machine_mode wanted_inner_reg_mode = word_mode;
5949   enum machine_mode pos_mode = word_mode;
5950   enum machine_mode extraction_mode = word_mode;
5951   enum machine_mode tmode = mode_for_size (len, MODE_INT, 1);
5952   rtx new = 0;
5953   rtx orig_pos_rtx = pos_rtx;
5954   HOST_WIDE_INT orig_pos;
5955
5956   if (GET_CODE (inner) == SUBREG && subreg_lowpart_p (inner))
5957     {
5958       /* If going from (subreg:SI (mem:QI ...)) to (mem:QI ...),
5959          consider just the QI as the memory to extract from.
5960          The subreg adds or removes high bits; its mode is
5961          irrelevant to the meaning of this extraction,
5962          since POS and LEN count from the lsb.  */
5963       if (MEM_P (SUBREG_REG (inner)))
5964         is_mode = GET_MODE (SUBREG_REG (inner));
5965       inner = SUBREG_REG (inner);
5966     }
5967   else if (GET_CODE (inner) == ASHIFT
5968            && GET_CODE (XEXP (inner, 1)) == CONST_INT
5969            && pos_rtx == 0 && pos == 0
5970            && len > (unsigned HOST_WIDE_INT) INTVAL (XEXP (inner, 1)))
5971     {
5972       /* We're extracting the least significant bits of an rtx
5973          (ashift X (const_int C)), where LEN > C.  Extract the
5974          least significant (LEN - C) bits of X, giving an rtx
5975          whose mode is MODE, then shift it left C times.  */
5976       new = make_extraction (mode, XEXP (inner, 0),
5977                              0, 0, len - INTVAL (XEXP (inner, 1)),
5978                              unsignedp, in_dest, in_compare);
5979       if (new != 0)
5980         return gen_rtx_ASHIFT (mode, new, XEXP (inner, 1));
5981     }
5982
5983   inner_mode = GET_MODE (inner);
5984
5985   if (pos_rtx && GET_CODE (pos_rtx) == CONST_INT)
5986     pos = INTVAL (pos_rtx), pos_rtx = 0;
5987
5988   /* See if this can be done without an extraction.  We never can if the
5989      width of the field is not the same as that of some integer mode. For
5990      registers, we can only avoid the extraction if the position is at the
5991      low-order bit and this is either not in the destination or we have the
5992      appropriate STRICT_LOW_PART operation available.
5993
5994      For MEM, we can avoid an extract if the field starts on an appropriate
5995      boundary and we can change the mode of the memory reference.  */
5996
5997   if (tmode != BLKmode
5998       && ((pos_rtx == 0 && (pos % BITS_PER_WORD) == 0
5999            && !MEM_P (inner)
6000            && (inner_mode == tmode
6001                || !REG_P (inner)
6002                || TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (tmode),
6003                                          GET_MODE_BITSIZE (inner_mode))
6004                || reg_truncated_to_mode (tmode, inner))
6005            && (! in_dest
6006                || (REG_P (inner)
6007                    && have_insn_for (STRICT_LOW_PART, tmode))))
6008           || (MEM_P (inner) && pos_rtx == 0
6009               && (pos
6010                   % (STRICT_ALIGNMENT ? GET_MODE_ALIGNMENT (tmode)
6011                      : BITS_PER_UNIT)) == 0
6012               /* We can't do this if we are widening INNER_MODE (it
6013                  may not be aligned, for one thing).  */
6014               && GET_MODE_BITSIZE (inner_mode) >= GET_MODE_BITSIZE (tmode)
6015               && (inner_mode == tmode
6016                   || (! mode_dependent_address_p (XEXP (inner, 0))
6017                       && ! MEM_VOLATILE_P (inner))))))
6018     {
6019       /* If INNER is a MEM, make a new MEM that encompasses just the desired
6020          field.  If the original and current mode are the same, we need not
6021          adjust the offset.  Otherwise, we do if bytes big endian.
6022
6023          If INNER is not a MEM, get a piece consisting of just the field
6024          of interest (in this case POS % BITS_PER_WORD must be 0).  */
6025
6026       if (MEM_P (inner))
6027         {
6028           HOST_WIDE_INT offset;
6029
6030           /* POS counts from lsb, but make OFFSET count in memory order.  */
6031           if (BYTES_BIG_ENDIAN)
6032             offset = (GET_MODE_BITSIZE (is_mode) - len - pos) / BITS_PER_UNIT;
6033           else
6034             offset = pos / BITS_PER_UNIT;
6035
6036           new = adjust_address_nv (inner, tmode, offset);
6037         }
6038       else if (REG_P (inner))
6039         {
6040           if (tmode != inner_mode)
6041             {
6042               /* We can't call gen_lowpart in a DEST since we
6043                  always want a SUBREG (see below) and it would sometimes
6044                  return a new hard register.  */
6045               if (pos || in_dest)
6046                 {
6047                   HOST_WIDE_INT final_word = pos / BITS_PER_WORD;
6048
6049                   if (WORDS_BIG_ENDIAN
6050                       && GET_MODE_SIZE (inner_mode) > UNITS_PER_WORD)
6051                     final_word = ((GET_MODE_SIZE (inner_mode)
6052                                    - GET_MODE_SIZE (tmode))
6053                                   / UNITS_PER_WORD) - final_word;
6054
6055                   final_word *= UNITS_PER_WORD;
6056                   if (BYTES_BIG_ENDIAN &&
6057                       GET_MODE_SIZE (inner_mode) > GET_MODE_SIZE (tmode))
6058                     final_word += (GET_MODE_SIZE (inner_mode)
6059                                    - GET_MODE_SIZE (tmode)) % UNITS_PER_WORD;
6060
6061                   /* Avoid creating invalid subregs, for example when
6062                      simplifying (x>>32)&255.  */
6063                   if (!validate_subreg (tmode, inner_mode, inner, final_word))
6064                     return NULL_RTX;
6065
6066                   new = gen_rtx_SUBREG (tmode, inner, final_word);
6067                 }
6068               else
6069                 new = gen_lowpart (tmode, inner);
6070             }
6071           else
6072             new = inner;
6073         }
6074       else
6075         new = force_to_mode (inner, tmode,
6076                              len >= HOST_BITS_PER_WIDE_INT
6077                              ? ~(unsigned HOST_WIDE_INT) 0
6078                              : ((unsigned HOST_WIDE_INT) 1 << len) - 1,
6079                              0);
6080
6081       /* If this extraction is going into the destination of a SET,
6082          make a STRICT_LOW_PART unless we made a MEM.  */
6083
6084       if (in_dest)
6085         return (MEM_P (new) ? new
6086                 : (GET_CODE (new) != SUBREG
6087                    ? gen_rtx_CLOBBER (tmode, const0_rtx)
6088                    : gen_rtx_STRICT_LOW_PART (VOIDmode, new)));
6089
6090       if (mode == tmode)
6091         return new;
6092
6093       if (GET_CODE (new) == CONST_INT)
6094         return gen_int_mode (INTVAL (new), mode);
6095
6096       /* If we know that no extraneous bits are set, and that the high
6097          bit is not set, convert the extraction to the cheaper of
6098          sign and zero extension, that are equivalent in these cases.  */
6099       if (flag_expensive_optimizations
6100           && (GET_MODE_BITSIZE (tmode) <= HOST_BITS_PER_WIDE_INT
6101               && ((nonzero_bits (new, tmode)
6102                    & ~(((unsigned HOST_WIDE_INT)
6103                         GET_MODE_MASK (tmode))
6104                        >> 1))
6105                   == 0)))
6106         {
6107           rtx temp = gen_rtx_ZERO_EXTEND (mode, new);
6108           rtx temp1 = gen_rtx_SIGN_EXTEND (mode, new);
6109
6110           /* Prefer ZERO_EXTENSION, since it gives more information to
6111              backends.  */
6112           if (rtx_cost (temp, SET) <= rtx_cost (temp1, SET))
6113             return temp;
6114           return temp1;
6115         }
6116
6117       /* Otherwise, sign- or zero-extend unless we already are in the
6118          proper mode.  */
6119
6120       return (gen_rtx_fmt_e (unsignedp ? ZERO_EXTEND : SIGN_EXTEND,
6121                              mode, new));
6122     }
6123
6124   /* Unless this is a COMPARE or we have a funny memory reference,
6125      don't do anything with zero-extending field extracts starting at
6126      the low-order bit since they are simple AND operations.  */
6127   if (pos_rtx == 0 && pos == 0 && ! in_dest
6128       && ! in_compare && unsignedp)
6129     return 0;
6130
6131   /* Unless INNER is not MEM, reject this if we would be spanning bytes or
6132      if the position is not a constant and the length is not 1.  In all
6133      other cases, we would only be going outside our object in cases when
6134      an original shift would have been undefined.  */
6135   if (MEM_P (inner)
6136       && ((pos_rtx == 0 && pos + len > GET_MODE_BITSIZE (is_mode))
6137           || (pos_rtx != 0 && len != 1)))
6138     return 0;
6139
6140   /* Get the mode to use should INNER not be a MEM, the mode for the position,
6141      and the mode for the result.  */
6142   if (in_dest && mode_for_extraction (EP_insv, -1) != MAX_MACHINE_MODE)
6143     {
6144       wanted_inner_reg_mode = mode_for_extraction (EP_insv, 0);
6145       pos_mode = mode_for_extraction (EP_insv, 2);
6146       extraction_mode = mode_for_extraction (EP_insv, 3);
6147     }
6148
6149   if (! in_dest && unsignedp
6150       && mode_for_extraction (EP_extzv, -1) != MAX_MACHINE_MODE)
6151     {
6152       wanted_inner_reg_mode = mode_for_extraction (EP_extzv, 1);
6153       pos_mode = mode_for_extraction (EP_extzv, 3);
6154       extraction_mode = mode_for_extraction (EP_extzv, 0);
6155     }
6156
6157   if (! in_dest && ! unsignedp
6158       && mode_for_extraction (EP_extv, -1) != MAX_MACHINE_MODE)
6159     {
6160       wanted_inner_reg_mode = mode_for_extraction (EP_extv, 1);
6161       pos_mode = mode_for_extraction (EP_extv, 3);
6162       extraction_mode = mode_for_extraction (EP_extv, 0);
6163     }
6164
6165   /* Never narrow an object, since that might not be safe.  */
6166
6167   if (mode != VOIDmode
6168       && GET_MODE_SIZE (extraction_mode) < GET_MODE_SIZE (mode))
6169     extraction_mode = mode;
6170
6171   if (pos_rtx && GET_MODE (pos_rtx) != VOIDmode
6172       && GET_MODE_SIZE (pos_mode) < GET_MODE_SIZE (GET_MODE (pos_rtx)))
6173     pos_mode = GET_MODE (pos_rtx);
6174
6175   /* If this is not from memory, the desired mode is the preferred mode
6176      for an extraction pattern's first input operand, or word_mode if there
6177      is none.  */
6178   if (!MEM_P (inner))
6179     wanted_inner_mode = wanted_inner_reg_mode;
6180   else
6181     {
6182       /* Be careful not to go beyond the extracted object and maintain the
6183          natural alignment of the memory.  */
6184       wanted_inner_mode = smallest_mode_for_size (len, MODE_INT);
6185       while (pos % GET_MODE_BITSIZE (wanted_inner_mode) + len
6186              > GET_MODE_BITSIZE (wanted_inner_mode))
6187         {
6188           wanted_inner_mode = GET_MODE_WIDER_MODE (wanted_inner_mode);
6189           gcc_assert (wanted_inner_mode != VOIDmode);
6190         }
6191
6192       /* If we have to change the mode of memory and cannot, the desired mode
6193          is EXTRACTION_MODE.  */
6194       if (inner_mode != wanted_inner_mode
6195           && (mode_dependent_address_p (XEXP (inner, 0))
6196               || MEM_VOLATILE_P (inner)
6197               || pos_rtx))
6198         wanted_inner_mode = extraction_mode;
6199     }
6200
6201   orig_pos = pos;
6202
6203   if (BITS_BIG_ENDIAN)
6204     {
6205       /* POS is passed as if BITS_BIG_ENDIAN == 0, so we need to convert it to
6206          BITS_BIG_ENDIAN style.  If position is constant, compute new
6207          position.  Otherwise, build subtraction.
6208          Note that POS is relative to the mode of the original argument.
6209          If it's a MEM we need to recompute POS relative to that.
6210          However, if we're extracting from (or inserting into) a register,
6211          we want to recompute POS relative to wanted_inner_mode.  */
6212       int width = (MEM_P (inner)
6213                    ? GET_MODE_BITSIZE (is_mode)
6214                    : GET_MODE_BITSIZE (wanted_inner_mode));
6215
6216       if (pos_rtx == 0)
6217         pos = width - len - pos;
6218       else
6219         pos_rtx
6220           = gen_rtx_MINUS (GET_MODE (pos_rtx), GEN_INT (width - len), pos_rtx);
6221       /* POS may be less than 0 now, but we check for that below.
6222          Note that it can only be less than 0 if !MEM_P (inner).  */
6223     }
6224
6225   /* If INNER has a wider mode, and this is a constant extraction, try to
6226      make it smaller and adjust the byte to point to the byte containing
6227      the value.  */
6228   if (wanted_inner_mode != VOIDmode
6229       && inner_mode != wanted_inner_mode
6230       && ! pos_rtx
6231       && GET_MODE_SIZE (wanted_inner_mode) < GET_MODE_SIZE (is_mode)
6232       && MEM_P (inner)
6233       && ! mode_dependent_address_p (XEXP (inner, 0))
6234       && ! MEM_VOLATILE_P (inner))
6235     {
6236       int offset = 0;
6237
6238       /* The computations below will be correct if the machine is big
6239          endian in both bits and bytes or little endian in bits and bytes.
6240          If it is mixed, we must adjust.  */
6241
6242       /* If bytes are big endian and we had a paradoxical SUBREG, we must
6243          adjust OFFSET to compensate.  */
6244       if (BYTES_BIG_ENDIAN
6245           && GET_MODE_SIZE (inner_mode) < GET_MODE_SIZE (is_mode))
6246         offset -= GET_MODE_SIZE (is_mode) - GET_MODE_SIZE (inner_mode);
6247
6248       /* We can now move to the desired byte.  */
6249       offset += (pos / GET_MODE_BITSIZE (wanted_inner_mode))
6250                 * GET_MODE_SIZE (wanted_inner_mode);
6251       pos %= GET_MODE_BITSIZE (wanted_inner_mode);
6252
6253       if (BYTES_BIG_ENDIAN != BITS_BIG_ENDIAN
6254           && is_mode != wanted_inner_mode)
6255         offset = (GET_MODE_SIZE (is_mode)
6256                   - GET_MODE_SIZE (wanted_inner_mode) - offset);
6257
6258       inner = adjust_address_nv (inner, wanted_inner_mode, offset);
6259     }
6260
6261   /* If INNER is not memory, we can always get it into the proper mode.  If we
6262      are changing its mode, POS must be a constant and smaller than the size
6263      of the new mode.  */
6264   else if (!MEM_P (inner))
6265     {
6266       if (GET_MODE (inner) != wanted_inner_mode
6267           && (pos_rtx != 0
6268               || orig_pos + len > GET_MODE_BITSIZE (wanted_inner_mode)))
6269         return 0;
6270
6271       if (orig_pos < 0)
6272         return 0;
6273
6274       inner = force_to_mode (inner, wanted_inner_mode,
6275                              pos_rtx
6276                              || len + orig_pos >= HOST_BITS_PER_WIDE_INT
6277                              ? ~(unsigned HOST_WIDE_INT) 0
6278                              : ((((unsigned HOST_WIDE_INT) 1 << len) - 1)
6279                                 << orig_pos),
6280                              0);
6281     }
6282
6283   /* Adjust mode of POS_RTX, if needed.  If we want a wider mode, we
6284      have to zero extend.  Otherwise, we can just use a SUBREG.  */
6285   if (pos_rtx != 0
6286       && GET_MODE_SIZE (pos_mode) > GET_MODE_SIZE (GET_MODE (pos_rtx)))
6287     {
6288       rtx temp = gen_rtx_ZERO_EXTEND (pos_mode, pos_rtx);
6289
6290       /* If we know that no extraneous bits are set, and that the high
6291          bit is not set, convert extraction to cheaper one - either
6292          SIGN_EXTENSION or ZERO_EXTENSION, that are equivalent in these
6293          cases.  */
6294       if (flag_expensive_optimizations
6295           && (GET_MODE_BITSIZE (GET_MODE (pos_rtx)) <= HOST_BITS_PER_WIDE_INT
6296               && ((nonzero_bits (pos_rtx, GET_MODE (pos_rtx))
6297                    & ~(((unsigned HOST_WIDE_INT)
6298                         GET_MODE_MASK (GET_MODE (pos_rtx)))
6299                        >> 1))
6300                   == 0)))
6301         {
6302           rtx temp1 = gen_rtx_SIGN_EXTEND (pos_mode, pos_rtx);
6303
6304           /* Prefer ZERO_EXTENSION, since it gives more information to
6305              backends.  */
6306           if (rtx_cost (temp1, SET) < rtx_cost (temp, SET))
6307             temp = temp1;
6308         }
6309       pos_rtx = temp;
6310     }
6311   else if (pos_rtx != 0
6312            && GET_MODE_SIZE (pos_mode) < GET_MODE_SIZE (GET_MODE (pos_rtx)))
6313     pos_rtx = gen_lowpart (pos_mode, pos_rtx);
6314
6315   /* Make POS_RTX unless we already have it and it is correct.  If we don't
6316      have a POS_RTX but we do have an ORIG_POS_RTX, the latter must
6317      be a CONST_INT.  */
6318   if (pos_rtx == 0 && orig_pos_rtx != 0 && INTVAL (orig_pos_rtx) == pos)
6319     pos_rtx = orig_pos_rtx;
6320
6321   else if (pos_rtx == 0)
6322     pos_rtx = GEN_INT (pos);
6323
6324   /* Make the required operation.  See if we can use existing rtx.  */
6325   new = gen_rtx_fmt_eee (unsignedp ? ZERO_EXTRACT : SIGN_EXTRACT,
6326                          extraction_mode, inner, GEN_INT (len), pos_rtx);
6327   if (! in_dest)
6328     new = gen_lowpart (mode, new);
6329
6330   return new;
6331 }
6332 \f
6333 /* See if X contains an ASHIFT of COUNT or more bits that can be commuted
6334    with any other operations in X.  Return X without that shift if so.  */
6335
6336 static rtx
6337 extract_left_shift (rtx x, int count)
6338 {
6339   enum rtx_code code = GET_CODE (x);
6340   enum machine_mode mode = GET_MODE (x);
6341   rtx tem;
6342
6343   switch (code)
6344     {
6345     case ASHIFT:
6346       /* This is the shift itself.  If it is wide enough, we will return
6347          either the value being shifted if the shift count is equal to
6348          COUNT or a shift for the difference.  */
6349       if (GET_CODE (XEXP (x, 1)) == CONST_INT
6350           && INTVAL (XEXP (x, 1)) >= count)
6351         return simplify_shift_const (NULL_RTX, ASHIFT, mode, XEXP (x, 0),
6352                                      INTVAL (XEXP (x, 1)) - count);
6353       break;
6354
6355     case NEG:  case NOT:
6356       if ((tem = extract_left_shift (XEXP (x, 0), count)) != 0)
6357         return simplify_gen_unary (code, mode, tem, mode);
6358
6359       break;
6360
6361     case PLUS:  case IOR:  case XOR:  case AND:
6362       /* If we can safely shift this constant and we find the inner shift,
6363          make a new operation.  */
6364       if (GET_CODE (XEXP (x, 1)) == CONST_INT
6365           && (INTVAL (XEXP (x, 1)) & ((((HOST_WIDE_INT) 1 << count)) - 1)) == 0
6366           && (tem = extract_left_shift (XEXP (x, 0), count)) != 0)
6367         return simplify_gen_binary (code, mode, tem,
6368                                     GEN_INT (INTVAL (XEXP (x, 1)) >> count));
6369
6370       break;
6371
6372     default:
6373       break;
6374     }
6375
6376   return 0;
6377 }
6378 \f
6379 /* Look at the expression rooted at X.  Look for expressions
6380    equivalent to ZERO_EXTRACT, SIGN_EXTRACT, ZERO_EXTEND, SIGN_EXTEND.
6381    Form these expressions.
6382
6383    Return the new rtx, usually just X.
6384
6385    Also, for machines like the VAX that don't have logical shift insns,
6386    try to convert logical to arithmetic shift operations in cases where
6387    they are equivalent.  This undoes the canonicalizations to logical
6388    shifts done elsewhere.
6389
6390    We try, as much as possible, to re-use rtl expressions to save memory.
6391
6392    IN_CODE says what kind of expression we are processing.  Normally, it is
6393    SET.  In a memory address (inside a MEM, PLUS or minus, the latter two
6394    being kludges), it is MEM.  When processing the arguments of a comparison
6395    or a COMPARE against zero, it is COMPARE.  */
6396
6397 static rtx
6398 make_compound_operation (rtx x, enum rtx_code in_code)
6399 {
6400   enum rtx_code code = GET_CODE (x);
6401   enum machine_mode mode = GET_MODE (x);
6402   int mode_width = GET_MODE_BITSIZE (mode);
6403   rtx rhs, lhs;
6404   enum rtx_code next_code;
6405   int i;
6406   rtx new = 0;
6407   rtx tem;
6408   const char *fmt;
6409
6410   /* Select the code to be used in recursive calls.  Once we are inside an
6411      address, we stay there.  If we have a comparison, set to COMPARE,
6412      but once inside, go back to our default of SET.  */
6413
6414   next_code = (code == MEM || code == PLUS || code == MINUS ? MEM
6415                : ((code == COMPARE || COMPARISON_P (x))
6416                   && XEXP (x, 1) == const0_rtx) ? COMPARE
6417                : in_code == COMPARE ? SET : in_code);
6418
6419   /* Process depending on the code of this operation.  If NEW is set
6420      nonzero, it will be returned.  */
6421
6422   switch (code)
6423     {
6424     case ASHIFT:
6425       /* Convert shifts by constants into multiplications if inside
6426          an address.  */
6427       if (in_code == MEM && GET_CODE (XEXP (x, 1)) == CONST_INT
6428           && INTVAL (XEXP (x, 1)) < HOST_BITS_PER_WIDE_INT
6429           && INTVAL (XEXP (x, 1)) >= 0)
6430         {
6431           new = make_compound_operation (XEXP (x, 0), next_code);
6432           new = gen_rtx_MULT (mode, new,
6433                               GEN_INT ((HOST_WIDE_INT) 1
6434                                        << INTVAL (XEXP (x, 1))));
6435         }
6436       break;
6437
6438     case AND:
6439       /* If the second operand is not a constant, we can't do anything
6440          with it.  */
6441       if (GET_CODE (XEXP (x, 1)) != CONST_INT)
6442         break;
6443
6444       /* If the constant is a power of two minus one and the first operand
6445          is a logical right shift, make an extraction.  */
6446       if (GET_CODE (XEXP (x, 0)) == LSHIFTRT
6447           && (i = exact_log2 (INTVAL (XEXP (x, 1)) + 1)) >= 0)
6448         {
6449           new = make_compound_operation (XEXP (XEXP (x, 0), 0), next_code);
6450           new = make_extraction (mode, new, 0, XEXP (XEXP (x, 0), 1), i, 1,
6451                                  0, in_code == COMPARE);
6452         }
6453
6454       /* Same as previous, but for (subreg (lshiftrt ...)) in first op.  */
6455       else if (GET_CODE (XEXP (x, 0)) == SUBREG
6456                && subreg_lowpart_p (XEXP (x, 0))
6457                && GET_CODE (SUBREG_REG (XEXP (x, 0))) == LSHIFTRT
6458                && (i = exact_log2 (INTVAL (XEXP (x, 1)) + 1)) >= 0)
6459         {
6460           new = make_compound_operation (XEXP (SUBREG_REG (XEXP (x, 0)), 0),
6461                                          next_code);
6462           new = make_extraction (GET_MODE (SUBREG_REG (XEXP (x, 0))), new, 0,
6463                                  XEXP (SUBREG_REG (XEXP (x, 0)), 1), i, 1,
6464                                  0, in_code == COMPARE);
6465         }
6466       /* Same as previous, but for (xor/ior (lshiftrt...) (lshiftrt...)).  */
6467       else if ((GET_CODE (XEXP (x, 0)) == XOR
6468                 || GET_CODE (XEXP (x, 0)) == IOR)
6469                && GET_CODE (XEXP (XEXP (x, 0), 0)) == LSHIFTRT
6470                && GET_CODE (XEXP (XEXP (x, 0), 1)) == LSHIFTRT
6471                && (i = exact_log2 (INTVAL (XEXP (x, 1)) + 1)) >= 0)
6472         {
6473           /* Apply the distributive law, and then try to make extractions.  */
6474           new = gen_rtx_fmt_ee (GET_CODE (XEXP (x, 0)), mode,
6475                                 gen_rtx_AND (mode, XEXP (XEXP (x, 0), 0),
6476                                              XEXP (x, 1)),
6477                                 gen_rtx_AND (mode, XEXP (XEXP (x, 0), 1),
6478                                              XEXP (x, 1)));
6479           new = make_compound_operation (new, in_code);
6480         }
6481
6482       /* If we are have (and (rotate X C) M) and C is larger than the number
6483          of bits in M, this is an extraction.  */
6484
6485       else if (GET_CODE (XEXP (x, 0)) == ROTATE
6486                && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
6487                && (i = exact_log2 (INTVAL (XEXP (x, 1)) + 1)) >= 0
6488                && i <= INTVAL (XEXP (XEXP (x, 0), 1)))
6489         {
6490           new = make_compound_operation (XEXP (XEXP (x, 0), 0), next_code);
6491           new = make_extraction (mode, new,
6492                                  (GET_MODE_BITSIZE (mode)
6493                                   - INTVAL (XEXP (XEXP (x, 0), 1))),
6494                                  NULL_RTX, i, 1, 0, in_code == COMPARE);
6495         }
6496
6497       /* On machines without logical shifts, if the operand of the AND is
6498          a logical shift and our mask turns off all the propagated sign
6499          bits, we can replace the logical shift with an arithmetic shift.  */
6500       else if (GET_CODE (XEXP (x, 0)) == LSHIFTRT
6501                && !have_insn_for (LSHIFTRT, mode)
6502                && have_insn_for (ASHIFTRT, mode)
6503                && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
6504                && INTVAL (XEXP (XEXP (x, 0), 1)) >= 0
6505                && INTVAL (XEXP (XEXP (x, 0), 1)) < HOST_BITS_PER_WIDE_INT
6506                && mode_width <= HOST_BITS_PER_WIDE_INT)
6507         {
6508           unsigned HOST_WIDE_INT mask = GET_MODE_MASK (mode);
6509
6510           mask >>= INTVAL (XEXP (XEXP (x, 0), 1));
6511           if ((INTVAL (XEXP (x, 1)) & ~mask) == 0)
6512             SUBST (XEXP (x, 0),
6513                    gen_rtx_ASHIFTRT (mode,
6514                                      make_compound_operation
6515                                      (XEXP (XEXP (x, 0), 0), next_code),
6516                                      XEXP (XEXP (x, 0), 1)));
6517         }
6518
6519       /* If the constant is one less than a power of two, this might be
6520          representable by an extraction even if no shift is present.
6521          If it doesn't end up being a ZERO_EXTEND, we will ignore it unless
6522          we are in a COMPARE.  */
6523       else if ((i = exact_log2 (INTVAL (XEXP (x, 1)) + 1)) >= 0)
6524         new = make_extraction (mode,
6525                                make_compound_operation (XEXP (x, 0),
6526                                                         next_code),
6527                                0, NULL_RTX, i, 1, 0, in_code == COMPARE);
6528
6529       /* If we are in a comparison and this is an AND with a power of two,
6530          convert this into the appropriate bit extract.  */
6531       else if (in_code == COMPARE
6532                && (i = exact_log2 (INTVAL (XEXP (x, 1)))) >= 0)
6533         new = make_extraction (mode,
6534                                make_compound_operation (XEXP (x, 0),
6535                                                         next_code),
6536                                i, NULL_RTX, 1, 1, 0, 1);
6537
6538       break;
6539
6540     case LSHIFTRT:
6541       /* If the sign bit is known to be zero, replace this with an
6542          arithmetic shift.  */
6543       if (have_insn_for (ASHIFTRT, mode)
6544           && ! have_insn_for (LSHIFTRT, mode)
6545           && mode_width <= HOST_BITS_PER_WIDE_INT
6546           && (nonzero_bits (XEXP (x, 0), mode) & (1 << (mode_width - 1))) == 0)
6547         {
6548           new = gen_rtx_ASHIFTRT (mode,
6549                                   make_compound_operation (XEXP (x, 0),
6550                                                            next_code),
6551                                   XEXP (x, 1));
6552           break;
6553         }
6554
6555       /* ... fall through ...  */
6556
6557     case ASHIFTRT:
6558       lhs = XEXP (x, 0);
6559       rhs = XEXP (x, 1);
6560
6561       /* If we have (ashiftrt (ashift foo C1) C2) with C2 >= C1,
6562          this is a SIGN_EXTRACT.  */
6563       if (GET_CODE (rhs) == CONST_INT
6564           && GET_CODE (lhs) == ASHIFT
6565           && GET_CODE (XEXP (lhs, 1)) == CONST_INT
6566           && INTVAL (rhs) >= INTVAL (XEXP (lhs, 1)))
6567         {
6568           new = make_compound_operation (XEXP (lhs, 0), next_code);
6569           new = make_extraction (mode, new,
6570                                  INTVAL (rhs) - INTVAL (XEXP (lhs, 1)),
6571                                  NULL_RTX, mode_width - INTVAL (rhs),
6572                                  code == LSHIFTRT, 0, in_code == COMPARE);
6573           break;
6574         }
6575
6576       /* See if we have operations between an ASHIFTRT and an ASHIFT.
6577          If so, try to merge the shifts into a SIGN_EXTEND.  We could
6578          also do this for some cases of SIGN_EXTRACT, but it doesn't
6579          seem worth the effort; the case checked for occurs on Alpha.  */
6580
6581       if (!OBJECT_P (lhs)
6582           && ! (GET_CODE (lhs) == SUBREG
6583                 && (OBJECT_P (SUBREG_REG (lhs))))
6584           && GET_CODE (rhs) == CONST_INT
6585           && INTVAL (rhs) < HOST_BITS_PER_WIDE_INT
6586           && (new = extract_left_shift (lhs, INTVAL (rhs))) != 0)
6587         new = make_extraction (mode, make_compound_operation (new, next_code),
6588                                0, NULL_RTX, mode_width - INTVAL (rhs),
6589                                code == LSHIFTRT, 0, in_code == COMPARE);
6590
6591       break;
6592
6593     case SUBREG:
6594       /* Call ourselves recursively on the inner expression.  If we are
6595          narrowing the object and it has a different RTL code from
6596          what it originally did, do this SUBREG as a force_to_mode.  */
6597
6598       tem = make_compound_operation (SUBREG_REG (x), in_code);
6599
6600       {
6601         rtx simplified;
6602         simplified = simplify_subreg (GET_MODE (x), tem, GET_MODE (tem),
6603                                       SUBREG_BYTE (x));
6604
6605         if (simplified)
6606           tem = simplified;
6607
6608         if (GET_CODE (tem) != GET_CODE (SUBREG_REG (x))
6609             && GET_MODE_SIZE (mode) < GET_MODE_SIZE (GET_MODE (tem))
6610             && subreg_lowpart_p (x))
6611           {
6612             rtx newer = force_to_mode (tem, mode, ~(HOST_WIDE_INT) 0,
6613                                        0);
6614
6615             /* If we have something other than a SUBREG, we might have
6616                done an expansion, so rerun ourselves.  */
6617             if (GET_CODE (newer) != SUBREG)
6618               newer = make_compound_operation (newer, in_code);
6619
6620             return newer;
6621           }
6622
6623         if (simplified)
6624           return tem;
6625       }
6626       break;
6627
6628     default:
6629       break;
6630     }
6631
6632   if (new)
6633     {
6634       x = gen_lowpart (mode, new);
6635       code = GET_CODE (x);
6636     }
6637
6638   /* Now recursively process each operand of this operation.  */
6639   fmt = GET_RTX_FORMAT (code);
6640   for (i = 0; i < GET_RTX_LENGTH (code); i++)
6641     if (fmt[i] == 'e')
6642       {
6643         new = make_compound_operation (XEXP (x, i), next_code);
6644         SUBST (XEXP (x, i), new);
6645       }
6646
6647   /* If this is a commutative operation, the changes to the operands
6648      may have made it noncanonical.  */
6649   if (COMMUTATIVE_ARITH_P (x)
6650       && swap_commutative_operands_p (XEXP (x, 0), XEXP (x, 1)))
6651     {
6652       tem = XEXP (x, 0);
6653       SUBST (XEXP (x, 0), XEXP (x, 1));
6654       SUBST (XEXP (x, 1), tem);
6655     }
6656
6657   return x;
6658 }
6659 \f
6660 /* Given M see if it is a value that would select a field of bits
6661    within an item, but not the entire word.  Return -1 if not.
6662    Otherwise, return the starting position of the field, where 0 is the
6663    low-order bit.
6664
6665    *PLEN is set to the length of the field.  */
6666
6667 static int
6668 get_pos_from_mask (unsigned HOST_WIDE_INT m, unsigned HOST_WIDE_INT *plen)
6669 {
6670   /* Get the bit number of the first 1 bit from the right, -1 if none.  */
6671   int pos = exact_log2 (m & -m);
6672   int len = 0;
6673
6674   if (pos >= 0)
6675     /* Now shift off the low-order zero bits and see if we have a
6676        power of two minus 1.  */
6677     len = exact_log2 ((m >> pos) + 1);
6678
6679   if (len <= 0)
6680     pos = -1;
6681
6682   *plen = len;
6683   return pos;
6684 }
6685 \f
6686 /* If X refers to a register that equals REG in value, replace these
6687    references with REG.  */
6688 static rtx
6689 canon_reg_for_combine (rtx x, rtx reg)
6690 {
6691   rtx op0, op1, op2;
6692   const char *fmt;
6693   int i;
6694   bool copied;
6695
6696   enum rtx_code code = GET_CODE (x);
6697   switch (GET_RTX_CLASS (code))
6698     {
6699     case RTX_UNARY:
6700       op0 = canon_reg_for_combine (XEXP (x, 0), reg);
6701       if (op0 != XEXP (x, 0))
6702         return simplify_gen_unary (GET_CODE (x), GET_MODE (x), op0,
6703                                    GET_MODE (reg));
6704       break;
6705
6706     case RTX_BIN_ARITH:
6707     case RTX_COMM_ARITH:
6708       op0 = canon_reg_for_combine (XEXP (x, 0), reg);
6709       op1 = canon_reg_for_combine (XEXP (x, 1), reg);
6710       if (op0 != XEXP (x, 0) || op1 != XEXP (x, 1))
6711         return simplify_gen_binary (GET_CODE (x), GET_MODE (x), op0, op1);
6712       break;
6713
6714     case RTX_COMPARE:
6715     case RTX_COMM_COMPARE:
6716       op0 = canon_reg_for_combine (XEXP (x, 0), reg);
6717       op1 = canon_reg_for_combine (XEXP (x, 1), reg);
6718       if (op0 != XEXP (x, 0) || op1 != XEXP (x, 1))
6719         return simplify_gen_relational (GET_CODE (x), GET_MODE (x),
6720                                         GET_MODE (op0), op0, op1);
6721       break;
6722
6723     case RTX_TERNARY:
6724     case RTX_BITFIELD_OPS:
6725       op0 = canon_reg_for_combine (XEXP (x, 0), reg);
6726       op1 = canon_reg_for_combine (XEXP (x, 1), reg);
6727       op2 = canon_reg_for_combine (XEXP (x, 2), reg);
6728       if (op0 != XEXP (x, 0) || op1 != XEXP (x, 1) || op2 != XEXP (x, 2))
6729         return simplify_gen_ternary (GET_CODE (x), GET_MODE (x),
6730                                      GET_MODE (op0), op0, op1, op2);
6731
6732     case RTX_OBJ:
6733       if (REG_P (x))
6734         {
6735           if (rtx_equal_p (get_last_value (reg), x)
6736               || rtx_equal_p (reg, get_last_value (x)))
6737             return reg;
6738           else
6739             break;
6740         }
6741
6742       /* fall through */
6743
6744     default:
6745       fmt = GET_RTX_FORMAT (code);
6746       copied = false;
6747       for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
6748         if (fmt[i] == 'e')
6749           {
6750             rtx op = canon_reg_for_combine (XEXP (x, i), reg);
6751             if (op != XEXP (x, i))
6752               {
6753                 if (!copied)
6754                   {
6755                     copied = true;
6756                     x = copy_rtx (x);
6757                   }
6758                 XEXP (x, i) = op;
6759               }
6760           }
6761         else if (fmt[i] == 'E')
6762           {
6763             int j;
6764             for (j = 0; j < XVECLEN (x, i); j++)
6765               {
6766                 rtx op = canon_reg_for_combine (XVECEXP (x, i, j), reg);
6767                 if (op != XVECEXP (x, i, j))
6768                   {
6769                     if (!copied)
6770                       {
6771                         copied = true;
6772                         x = copy_rtx (x);
6773                       }
6774                     XVECEXP (x, i, j) = op;
6775                   }
6776               }
6777           }
6778
6779       break;
6780     }
6781
6782   return x;
6783 }
6784
6785 /* Return X converted to MODE.  If the value is already truncated to
6786    MODE we can just return a subreg even though in the general case we
6787    would need an explicit truncation.  */
6788
6789 static rtx
6790 gen_lowpart_or_truncate (enum machine_mode mode, rtx x)
6791 {
6792   if (GET_MODE_SIZE (GET_MODE (x)) <= GET_MODE_SIZE (mode)
6793       || TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (mode),
6794                                 GET_MODE_BITSIZE (GET_MODE (x)))
6795       || (REG_P (x) && reg_truncated_to_mode (mode, x)))
6796     return gen_lowpart (mode, x);
6797   else
6798     return simplify_gen_unary (TRUNCATE, mode, x, GET_MODE (x));
6799 }
6800
6801 /* See if X can be simplified knowing that we will only refer to it in
6802    MODE and will only refer to those bits that are nonzero in MASK.
6803    If other bits are being computed or if masking operations are done
6804    that select a superset of the bits in MASK, they can sometimes be
6805    ignored.
6806
6807    Return a possibly simplified expression, but always convert X to
6808    MODE.  If X is a CONST_INT, AND the CONST_INT with MASK.
6809
6810    If JUST_SELECT is nonzero, don't optimize by noticing that bits in MASK
6811    are all off in X.  This is used when X will be complemented, by either
6812    NOT, NEG, or XOR.  */
6813
6814 static rtx
6815 force_to_mode (rtx x, enum machine_mode mode, unsigned HOST_WIDE_INT mask,
6816                int just_select)
6817 {
6818   enum rtx_code code = GET_CODE (x);
6819   int next_select = just_select || code == XOR || code == NOT || code == NEG;
6820   enum machine_mode op_mode;
6821   unsigned HOST_WIDE_INT fuller_mask, nonzero;
6822   rtx op0, op1, temp;
6823
6824   /* If this is a CALL or ASM_OPERANDS, don't do anything.  Some of the
6825      code below will do the wrong thing since the mode of such an
6826      expression is VOIDmode.
6827
6828      Also do nothing if X is a CLOBBER; this can happen if X was
6829      the return value from a call to gen_lowpart.  */
6830   if (code == CALL || code == ASM_OPERANDS || code == CLOBBER)
6831     return x;
6832
6833   /* We want to perform the operation is its present mode unless we know
6834      that the operation is valid in MODE, in which case we do the operation
6835      in MODE.  */
6836   op_mode = ((GET_MODE_CLASS (mode) == GET_MODE_CLASS (GET_MODE (x))
6837               && have_insn_for (code, mode))
6838              ? mode : GET_MODE (x));
6839
6840   /* It is not valid to do a right-shift in a narrower mode
6841      than the one it came in with.  */
6842   if ((code == LSHIFTRT || code == ASHIFTRT)
6843       && GET_MODE_BITSIZE (mode) < GET_MODE_BITSIZE (GET_MODE (x)))
6844     op_mode = GET_MODE (x);
6845
6846   /* Truncate MASK to fit OP_MODE.  */
6847   if (op_mode)
6848     mask &= GET_MODE_MASK (op_mode);
6849
6850   /* When we have an arithmetic operation, or a shift whose count we
6851      do not know, we need to assume that all bits up to the highest-order
6852      bit in MASK will be needed.  This is how we form such a mask.  */
6853   if (mask & ((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT - 1)))
6854     fuller_mask = ~(unsigned HOST_WIDE_INT) 0;
6855   else
6856     fuller_mask = (((unsigned HOST_WIDE_INT) 1 << (floor_log2 (mask) + 1))
6857                    - 1);
6858
6859   /* Determine what bits of X are guaranteed to be (non)zero.  */
6860   nonzero = nonzero_bits (x, mode);
6861
6862   /* If none of the bits in X are needed, return a zero.  */
6863   if (!just_select && (nonzero & mask) == 0 && !side_effects_p (x))
6864     x = const0_rtx;
6865
6866   /* If X is a CONST_INT, return a new one.  Do this here since the
6867      test below will fail.  */
6868   if (GET_CODE (x) == CONST_INT)
6869     {
6870       if (SCALAR_INT_MODE_P (mode))
6871         return gen_int_mode (INTVAL (x) & mask, mode);
6872       else
6873         {
6874           x = GEN_INT (INTVAL (x) & mask);
6875           return gen_lowpart_common (mode, x);
6876         }
6877     }
6878
6879   /* If X is narrower than MODE and we want all the bits in X's mode, just
6880      get X in the proper mode.  */
6881   if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (mode)
6882       && (GET_MODE_MASK (GET_MODE (x)) & ~mask) == 0)
6883     return gen_lowpart (mode, x);
6884
6885   switch (code)
6886     {
6887     case CLOBBER:
6888       /* If X is a (clobber (const_int)), return it since we know we are
6889          generating something that won't match.  */
6890       return x;
6891
6892     case SIGN_EXTEND:
6893     case ZERO_EXTEND:
6894     case ZERO_EXTRACT:
6895     case SIGN_EXTRACT:
6896       x = expand_compound_operation (x);
6897       if (GET_CODE (x) != code)
6898         return force_to_mode (x, mode, mask, next_select);
6899       break;
6900
6901     case SUBREG:
6902       if (subreg_lowpart_p (x)
6903           /* We can ignore the effect of this SUBREG if it narrows the mode or
6904              if the constant masks to zero all the bits the mode doesn't
6905              have.  */
6906           && ((GET_MODE_SIZE (GET_MODE (x))
6907                < GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))))
6908               || (0 == (mask
6909                         & GET_MODE_MASK (GET_MODE (x))
6910                         & ~GET_MODE_MASK (GET_MODE (SUBREG_REG (x)))))))
6911         return force_to_mode (SUBREG_REG (x), mode, mask, next_select);
6912       break;
6913
6914     case AND:
6915       /* If this is an AND with a constant, convert it into an AND
6916          whose constant is the AND of that constant with MASK.  If it
6917          remains an AND of MASK, delete it since it is redundant.  */
6918
6919       if (GET_CODE (XEXP (x, 1)) == CONST_INT)
6920         {
6921           x = simplify_and_const_int (x, op_mode, XEXP (x, 0),
6922                                       mask & INTVAL (XEXP (x, 1)));
6923
6924           /* If X is still an AND, see if it is an AND with a mask that
6925              is just some low-order bits.  If so, and it is MASK, we don't
6926              need it.  */
6927
6928           if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT
6929               && ((INTVAL (XEXP (x, 1)) & GET_MODE_MASK (GET_MODE (x)))
6930                   == mask))
6931             x = XEXP (x, 0);
6932
6933           /* If it remains an AND, try making another AND with the bits
6934              in the mode mask that aren't in MASK turned on.  If the
6935              constant in the AND is wide enough, this might make a
6936              cheaper constant.  */
6937
6938           if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT
6939               && GET_MODE_MASK (GET_MODE (x)) != mask
6940               && GET_MODE_BITSIZE (GET_MODE (x)) <= HOST_BITS_PER_WIDE_INT)
6941             {
6942               HOST_WIDE_INT cval = (INTVAL (XEXP (x, 1))
6943                                     | (GET_MODE_MASK (GET_MODE (x)) & ~mask));
6944               int width = GET_MODE_BITSIZE (GET_MODE (x));
6945               rtx y;
6946
6947               /* If MODE is narrower than HOST_WIDE_INT and CVAL is a negative
6948                  number, sign extend it.  */
6949               if (width > 0 && width < HOST_BITS_PER_WIDE_INT
6950                   && (cval & ((HOST_WIDE_INT) 1 << (width - 1))) != 0)
6951                 cval |= (HOST_WIDE_INT) -1 << width;
6952
6953               y = simplify_gen_binary (AND, GET_MODE (x),
6954                                        XEXP (x, 0), GEN_INT (cval));
6955               if (rtx_cost (y, SET) < rtx_cost (x, SET))
6956                 x = y;
6957             }
6958
6959           break;
6960         }
6961
6962       goto binop;
6963
6964     case PLUS:
6965       /* In (and (plus FOO C1) M), if M is a mask that just turns off
6966          low-order bits (as in an alignment operation) and FOO is already
6967          aligned to that boundary, mask C1 to that boundary as well.
6968          This may eliminate that PLUS and, later, the AND.  */
6969
6970       {
6971         unsigned int width = GET_MODE_BITSIZE (mode);
6972         unsigned HOST_WIDE_INT smask = mask;
6973
6974         /* If MODE is narrower than HOST_WIDE_INT and mask is a negative
6975            number, sign extend it.  */
6976
6977         if (width < HOST_BITS_PER_WIDE_INT
6978             && (smask & ((HOST_WIDE_INT) 1 << (width - 1))) != 0)
6979           smask |= (HOST_WIDE_INT) -1 << width;
6980
6981         if (GET_CODE (XEXP (x, 1)) == CONST_INT
6982             && exact_log2 (- smask) >= 0
6983             && (nonzero_bits (XEXP (x, 0), mode) & ~smask) == 0
6984             && (INTVAL (XEXP (x, 1)) & ~smask) != 0)
6985           return force_to_mode (plus_constant (XEXP (x, 0),
6986                                                (INTVAL (XEXP (x, 1)) & smask)),
6987                                 mode, smask, next_select);
6988       }
6989
6990       /* ... fall through ...  */
6991
6992     case MULT:
6993       /* For PLUS, MINUS and MULT, we need any bits less significant than the
6994          most significant bit in MASK since carries from those bits will
6995          affect the bits we are interested in.  */
6996       mask = fuller_mask;
6997       goto binop;
6998
6999     case MINUS:
7000       /* If X is (minus C Y) where C's least set bit is larger than any bit
7001          in the mask, then we may replace with (neg Y).  */
7002       if (GET_CODE (XEXP (x, 0)) == CONST_INT
7003           && (((unsigned HOST_WIDE_INT) (INTVAL (XEXP (x, 0))
7004                                         & -INTVAL (XEXP (x, 0))))
7005               > mask))
7006         {
7007           x = simplify_gen_unary (NEG, GET_MODE (x), XEXP (x, 1),
7008                                   GET_MODE (x));
7009           return force_to_mode (x, mode, mask, next_select);
7010         }
7011
7012       /* Similarly, if C contains every bit in the fuller_mask, then we may
7013          replace with (not Y).  */
7014       if (GET_CODE (XEXP (x, 0)) == CONST_INT
7015           && ((INTVAL (XEXP (x, 0)) | (HOST_WIDE_INT) fuller_mask)
7016               == INTVAL (XEXP (x, 0))))
7017         {
7018           x = simplify_gen_unary (NOT, GET_MODE (x),
7019                                   XEXP (x, 1), GET_MODE (x));
7020           return force_to_mode (x, mode, mask, next_select);
7021         }
7022
7023       mask = fuller_mask;
7024       goto binop;
7025
7026     case IOR:
7027     case XOR:
7028       /* If X is (ior (lshiftrt FOO C1) C2), try to commute the IOR and
7029          LSHIFTRT so we end up with an (and (lshiftrt (ior ...) ...) ...)
7030          operation which may be a bitfield extraction.  Ensure that the
7031          constant we form is not wider than the mode of X.  */
7032
7033       if (GET_CODE (XEXP (x, 0)) == LSHIFTRT
7034           && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
7035           && INTVAL (XEXP (XEXP (x, 0), 1)) >= 0
7036           && INTVAL (XEXP (XEXP (x, 0), 1)) < HOST_BITS_PER_WIDE_INT
7037           && GET_CODE (XEXP (x, 1)) == CONST_INT
7038           && ((INTVAL (XEXP (XEXP (x, 0), 1))
7039                + floor_log2 (INTVAL (XEXP (x, 1))))
7040               < GET_MODE_BITSIZE (GET_MODE (x)))
7041           && (INTVAL (XEXP (x, 1))
7042               & ~nonzero_bits (XEXP (x, 0), GET_MODE (x))) == 0)
7043         {
7044           temp = GEN_INT ((INTVAL (XEXP (x, 1)) & mask)
7045                           << INTVAL (XEXP (XEXP (x, 0), 1)));
7046           temp = simplify_gen_binary (GET_CODE (x), GET_MODE (x),
7047                                       XEXP (XEXP (x, 0), 0), temp);
7048           x = simplify_gen_binary (LSHIFTRT, GET_MODE (x), temp,
7049                                    XEXP (XEXP (x, 0), 1));
7050           return force_to_mode (x, mode, mask, next_select);
7051         }
7052
7053     binop:
7054       /* For most binary operations, just propagate into the operation and
7055          change the mode if we have an operation of that mode.  */
7056
7057       op0 = gen_lowpart_or_truncate (op_mode,
7058                                      force_to_mode (XEXP (x, 0), mode, mask,
7059                                                     next_select));
7060       op1 = gen_lowpart_or_truncate (op_mode,
7061                                      force_to_mode (XEXP (x, 1), mode, mask,
7062                                         next_select));
7063
7064       if (op_mode != GET_MODE (x) || op0 != XEXP (x, 0) || op1 != XEXP (x, 1))
7065         x = simplify_gen_binary (code, op_mode, op0, op1);
7066       break;
7067
7068     case ASHIFT:
7069       /* For left shifts, do the same, but just for the first operand.
7070          However, we cannot do anything with shifts where we cannot
7071          guarantee that the counts are smaller than the size of the mode
7072          because such a count will have a different meaning in a
7073          wider mode.  */
7074
7075       if (! (GET_CODE (XEXP (x, 1)) == CONST_INT
7076              && INTVAL (XEXP (x, 1)) >= 0
7077              && INTVAL (XEXP (x, 1)) < GET_MODE_BITSIZE (mode))
7078           && ! (GET_MODE (XEXP (x, 1)) != VOIDmode
7079                 && (nonzero_bits (XEXP (x, 1), GET_MODE (XEXP (x, 1)))
7080                     < (unsigned HOST_WIDE_INT) GET_MODE_BITSIZE (mode))))
7081         break;
7082
7083       /* If the shift count is a constant and we can do arithmetic in
7084          the mode of the shift, refine which bits we need.  Otherwise, use the
7085          conservative form of the mask.  */
7086       if (GET_CODE (XEXP (x, 1)) == CONST_INT
7087           && INTVAL (XEXP (x, 1)) >= 0
7088           && INTVAL (XEXP (x, 1)) < GET_MODE_BITSIZE (op_mode)
7089           && GET_MODE_BITSIZE (op_mode) <= HOST_BITS_PER_WIDE_INT)
7090         mask >>= INTVAL (XEXP (x, 1));
7091       else
7092         mask = fuller_mask;
7093
7094       op0 = gen_lowpart_or_truncate (op_mode,
7095                                      force_to_mode (XEXP (x, 0), op_mode,
7096                                                     mask, next_select));
7097
7098       if (op_mode != GET_MODE (x) || op0 != XEXP (x, 0))
7099         x = simplify_gen_binary (code, op_mode, op0, XEXP (x, 1));
7100       break;
7101
7102     case LSHIFTRT:
7103       /* Here we can only do something if the shift count is a constant,
7104          this shift constant is valid for the host, and we can do arithmetic
7105          in OP_MODE.  */
7106
7107       if (GET_CODE (XEXP (x, 1)) == CONST_INT
7108           && INTVAL (XEXP (x, 1)) < HOST_BITS_PER_WIDE_INT
7109           && GET_MODE_BITSIZE (op_mode) <= HOST_BITS_PER_WIDE_INT)
7110         {
7111           rtx inner = XEXP (x, 0);
7112           unsigned HOST_WIDE_INT inner_mask;
7113
7114           /* Select the mask of the bits we need for the shift operand.  */
7115           inner_mask = mask << INTVAL (XEXP (x, 1));
7116
7117           /* We can only change the mode of the shift if we can do arithmetic
7118              in the mode of the shift and INNER_MASK is no wider than the
7119              width of X's mode.  */
7120           if ((inner_mask & ~GET_MODE_MASK (GET_MODE (x))) != 0)
7121             op_mode = GET_MODE (x);
7122
7123           inner = force_to_mode (inner, op_mode, inner_mask, next_select);
7124
7125           if (GET_MODE (x) != op_mode || inner != XEXP (x, 0))
7126             x = simplify_gen_binary (LSHIFTRT, op_mode, inner, XEXP (x, 1));
7127         }
7128
7129       /* If we have (and (lshiftrt FOO C1) C2) where the combination of the
7130          shift and AND produces only copies of the sign bit (C2 is one less
7131          than a power of two), we can do this with just a shift.  */
7132
7133       if (GET_CODE (x) == LSHIFTRT
7134           && GET_CODE (XEXP (x, 1)) == CONST_INT
7135           /* The shift puts one of the sign bit copies in the least significant
7136              bit.  */
7137           && ((INTVAL (XEXP (x, 1))
7138                + num_sign_bit_copies (XEXP (x, 0), GET_MODE (XEXP (x, 0))))
7139               >= GET_MODE_BITSIZE (GET_MODE (x)))
7140           && exact_log2 (mask + 1) >= 0
7141           /* Number of bits left after the shift must be more than the mask
7142              needs.  */
7143           && ((INTVAL (XEXP (x, 1)) + exact_log2 (mask + 1))
7144               <= GET_MODE_BITSIZE (GET_MODE (x)))
7145           /* Must be more sign bit copies than the mask needs.  */
7146           && ((int) num_sign_bit_copies (XEXP (x, 0), GET_MODE (XEXP (x, 0)))
7147               >= exact_log2 (mask + 1)))
7148         x = simplify_gen_binary (LSHIFTRT, GET_MODE (x), XEXP (x, 0),
7149                                  GEN_INT (GET_MODE_BITSIZE (GET_MODE (x))
7150                                           - exact_log2 (mask + 1)));
7151
7152       goto shiftrt;
7153
7154     case ASHIFTRT:
7155       /* If we are just looking for the sign bit, we don't need this shift at
7156          all, even if it has a variable count.  */
7157       if (GET_MODE_BITSIZE (GET_MODE (x)) <= HOST_BITS_PER_WIDE_INT
7158           && (mask == ((unsigned HOST_WIDE_INT) 1
7159                        << (GET_MODE_BITSIZE (GET_MODE (x)) - 1))))
7160         return force_to_mode (XEXP (x, 0), mode, mask, next_select);
7161
7162       /* If this is a shift by a constant, get a mask that contains those bits
7163          that are not copies of the sign bit.  We then have two cases:  If
7164          MASK only includes those bits, this can be a logical shift, which may
7165          allow simplifications.  If MASK is a single-bit field not within
7166          those bits, we are requesting a copy of the sign bit and hence can
7167          shift the sign bit to the appropriate location.  */
7168
7169       if (GET_CODE (XEXP (x, 1)) == CONST_INT && INTVAL (XEXP (x, 1)) >= 0
7170           && INTVAL (XEXP (x, 1)) < HOST_BITS_PER_WIDE_INT)
7171         {
7172           int i;
7173
7174           /* If the considered data is wider than HOST_WIDE_INT, we can't
7175              represent a mask for all its bits in a single scalar.
7176              But we only care about the lower bits, so calculate these.  */
7177
7178           if (GET_MODE_BITSIZE (GET_MODE (x)) > HOST_BITS_PER_WIDE_INT)
7179             {
7180               nonzero = ~(HOST_WIDE_INT) 0;
7181
7182               /* GET_MODE_BITSIZE (GET_MODE (x)) - INTVAL (XEXP (x, 1))
7183                  is the number of bits a full-width mask would have set.
7184                  We need only shift if these are fewer than nonzero can
7185                  hold.  If not, we must keep all bits set in nonzero.  */
7186
7187               if (GET_MODE_BITSIZE (GET_MODE (x)) - INTVAL (XEXP (x, 1))
7188                   < HOST_BITS_PER_WIDE_INT)
7189                 nonzero >>= INTVAL (XEXP (x, 1))
7190                             + HOST_BITS_PER_WIDE_INT
7191                             - GET_MODE_BITSIZE (GET_MODE (x)) ;
7192             }
7193           else
7194             {
7195               nonzero = GET_MODE_MASK (GET_MODE (x));
7196               nonzero >>= INTVAL (XEXP (x, 1));
7197             }
7198
7199           if ((mask & ~nonzero) == 0)
7200             {
7201               x = simplify_shift_const (NULL_RTX, LSHIFTRT, GET_MODE (x),
7202                                         XEXP (x, 0), INTVAL (XEXP (x, 1)));
7203               if (GET_CODE (x) != ASHIFTRT)
7204                 return force_to_mode (x, mode, mask, next_select);
7205             }
7206
7207           else if ((i = exact_log2 (mask)) >= 0)
7208             {
7209               x = simplify_shift_const
7210                   (NULL_RTX, LSHIFTRT, GET_MODE (x), XEXP (x, 0),
7211                    GET_MODE_BITSIZE (GET_MODE (x)) - 1 - i);
7212
7213               if (GET_CODE (x) != ASHIFTRT)
7214                 return force_to_mode (x, mode, mask, next_select);
7215             }
7216         }
7217
7218       /* If MASK is 1, convert this to an LSHIFTRT.  This can be done
7219          even if the shift count isn't a constant.  */
7220       if (mask == 1)
7221         x = simplify_gen_binary (LSHIFTRT, GET_MODE (x),
7222                                  XEXP (x, 0), XEXP (x, 1));
7223
7224     shiftrt:
7225
7226       /* If this is a zero- or sign-extension operation that just affects bits
7227          we don't care about, remove it.  Be sure the call above returned
7228          something that is still a shift.  */
7229
7230       if ((GET_CODE (x) == LSHIFTRT || GET_CODE (x) == ASHIFTRT)
7231           && GET_CODE (XEXP (x, 1)) == CONST_INT
7232           && INTVAL (XEXP (x, 1)) >= 0
7233           && (INTVAL (XEXP (x, 1))
7234               <= GET_MODE_BITSIZE (GET_MODE (x)) - (floor_log2 (mask) + 1))
7235           && GET_CODE (XEXP (x, 0)) == ASHIFT
7236           && XEXP (XEXP (x, 0), 1) == XEXP (x, 1))
7237         return force_to_mode (XEXP (XEXP (x, 0), 0), mode, mask,
7238                               next_select);
7239
7240       break;
7241
7242     case ROTATE:
7243     case ROTATERT:
7244       /* If the shift count is constant and we can do computations
7245          in the mode of X, compute where the bits we care about are.
7246          Otherwise, we can't do anything.  Don't change the mode of
7247          the shift or propagate MODE into the shift, though.  */
7248       if (GET_CODE (XEXP (x, 1)) == CONST_INT
7249           && INTVAL (XEXP (x, 1)) >= 0)
7250         {
7251           temp = simplify_binary_operation (code == ROTATE ? ROTATERT : ROTATE,
7252                                             GET_MODE (x), GEN_INT (mask),
7253                                             XEXP (x, 1));
7254           if (temp && GET_CODE (temp) == CONST_INT)
7255             SUBST (XEXP (x, 0),
7256                    force_to_mode (XEXP (x, 0), GET_MODE (x),
7257                                   INTVAL (temp), next_select));
7258         }
7259       break;
7260
7261     case NEG:
7262       /* If we just want the low-order bit, the NEG isn't needed since it
7263          won't change the low-order bit.  */
7264       if (mask == 1)
7265         return force_to_mode (XEXP (x, 0), mode, mask, just_select);
7266
7267       /* We need any bits less significant than the most significant bit in
7268          MASK since carries from those bits will affect the bits we are
7269          interested in.  */
7270       mask = fuller_mask;
7271       goto unop;
7272
7273     case NOT:
7274       /* (not FOO) is (xor FOO CONST), so if FOO is an LSHIFTRT, we can do the
7275          same as the XOR case above.  Ensure that the constant we form is not
7276          wider than the mode of X.  */
7277
7278       if (GET_CODE (XEXP (x, 0)) == LSHIFTRT
7279           && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
7280           && INTVAL (XEXP (XEXP (x, 0), 1)) >= 0
7281           && (INTVAL (XEXP (XEXP (x, 0), 1)) + floor_log2 (mask)
7282               < GET_MODE_BITSIZE (GET_MODE (x)))
7283           && INTVAL (XEXP (XEXP (x, 0), 1)) < HOST_BITS_PER_WIDE_INT)
7284         {
7285           temp = gen_int_mode (mask << INTVAL (XEXP (XEXP (x, 0), 1)),
7286                                GET_MODE (x));
7287           temp = simplify_gen_binary (XOR, GET_MODE (x),
7288                                       XEXP (XEXP (x, 0), 0), temp);
7289           x = simplify_gen_binary (LSHIFTRT, GET_MODE (x),
7290                                    temp, XEXP (XEXP (x, 0), 1));
7291
7292           return force_to_mode (x, mode, mask, next_select);
7293         }
7294
7295       /* (and (not FOO) CONST) is (not (or FOO (not CONST))), so we must
7296          use the full mask inside the NOT.  */
7297       mask = fuller_mask;
7298
7299     unop:
7300       op0 = gen_lowpart_or_truncate (op_mode,
7301                                      force_to_mode (XEXP (x, 0), mode, mask,
7302                                                     next_select));
7303       if (op_mode != GET_MODE (x) || op0 != XEXP (x, 0))
7304         x = simplify_gen_unary (code, op_mode, op0, op_mode);
7305       break;
7306
7307     case NE:
7308       /* (and (ne FOO 0) CONST) can be (and FOO CONST) if CONST is included
7309          in STORE_FLAG_VALUE and FOO has a single bit that might be nonzero,
7310          which is equal to STORE_FLAG_VALUE.  */
7311       if ((mask & ~STORE_FLAG_VALUE) == 0 && XEXP (x, 1) == const0_rtx
7312           && GET_MODE (XEXP (x, 0)) == mode
7313           && exact_log2 (nonzero_bits (XEXP (x, 0), mode)) >= 0
7314           && (nonzero_bits (XEXP (x, 0), mode)
7315               == (unsigned HOST_WIDE_INT) STORE_FLAG_VALUE))
7316         return force_to_mode (XEXP (x, 0), mode, mask, next_select);
7317
7318       break;
7319
7320     case IF_THEN_ELSE:
7321       /* We have no way of knowing if the IF_THEN_ELSE can itself be
7322          written in a narrower mode.  We play it safe and do not do so.  */
7323
7324       SUBST (XEXP (x, 1),
7325              gen_lowpart_or_truncate (GET_MODE (x),
7326                                       force_to_mode (XEXP (x, 1), mode,
7327                                                      mask, next_select)));
7328       SUBST (XEXP (x, 2),
7329              gen_lowpart_or_truncate (GET_MODE (x),
7330                                       force_to_mode (XEXP (x, 2), mode,
7331                                                      mask, next_select)));
7332       break;
7333
7334     default:
7335       break;
7336     }
7337
7338   /* Ensure we return a value of the proper mode.  */
7339   return gen_lowpart_or_truncate (mode, x);
7340 }
7341 \f
7342 /* Return nonzero if X is an expression that has one of two values depending on
7343    whether some other value is zero or nonzero.  In that case, we return the
7344    value that is being tested, *PTRUE is set to the value if the rtx being
7345    returned has a nonzero value, and *PFALSE is set to the other alternative.
7346
7347    If we return zero, we set *PTRUE and *PFALSE to X.  */
7348
7349 static rtx
7350 if_then_else_cond (rtx x, rtx *ptrue, rtx *pfalse)
7351 {
7352   enum machine_mode mode = GET_MODE (x);
7353   enum rtx_code code = GET_CODE (x);
7354   rtx cond0, cond1, true0, true1, false0, false1;
7355   unsigned HOST_WIDE_INT nz;
7356
7357   /* If we are comparing a value against zero, we are done.  */
7358   if ((code == NE || code == EQ)
7359       && XEXP (x, 1) == const0_rtx)
7360     {
7361       *ptrue = (code == NE) ? const_true_rtx : const0_rtx;
7362       *pfalse = (code == NE) ? const0_rtx : const_true_rtx;
7363       return XEXP (x, 0);
7364     }
7365
7366   /* If this is a unary operation whose operand has one of two values, apply
7367      our opcode to compute those values.  */
7368   else if (UNARY_P (x)
7369            && (cond0 = if_then_else_cond (XEXP (x, 0), &true0, &false0)) != 0)
7370     {
7371       *ptrue = simplify_gen_unary (code, mode, true0, GET_MODE (XEXP (x, 0)));
7372       *pfalse = simplify_gen_unary (code, mode, false0,
7373                                     GET_MODE (XEXP (x, 0)));
7374       return cond0;
7375     }
7376
7377   /* If this is a COMPARE, do nothing, since the IF_THEN_ELSE we would
7378      make can't possibly match and would suppress other optimizations.  */
7379   else if (code == COMPARE)
7380     ;
7381
7382   /* If this is a binary operation, see if either side has only one of two
7383      values.  If either one does or if both do and they are conditional on
7384      the same value, compute the new true and false values.  */
7385   else if (BINARY_P (x))
7386     {
7387       cond0 = if_then_else_cond (XEXP (x, 0), &true0, &false0);
7388       cond1 = if_then_else_cond (XEXP (x, 1), &true1, &false1);
7389
7390       if ((cond0 != 0 || cond1 != 0)
7391           && ! (cond0 != 0 && cond1 != 0 && ! rtx_equal_p (cond0, cond1)))
7392         {
7393           /* If if_then_else_cond returned zero, then true/false are the
7394              same rtl.  We must copy one of them to prevent invalid rtl
7395              sharing.  */
7396           if (cond0 == 0)
7397             true0 = copy_rtx (true0);
7398           else if (cond1 == 0)
7399             true1 = copy_rtx (true1);
7400
7401           if (COMPARISON_P (x))
7402             {
7403               *ptrue = simplify_gen_relational (code, mode, VOIDmode,
7404                                                 true0, true1);
7405               *pfalse = simplify_gen_relational (code, mode, VOIDmode,
7406                                                  false0, false1);
7407              }
7408           else
7409             {
7410               *ptrue = simplify_gen_binary (code, mode, true0, true1);
7411               *pfalse = simplify_gen_binary (code, mode, false0, false1);
7412             }
7413
7414           return cond0 ? cond0 : cond1;
7415         }
7416
7417       /* See if we have PLUS, IOR, XOR, MINUS or UMAX, where one of the
7418          operands is zero when the other is nonzero, and vice-versa,
7419          and STORE_FLAG_VALUE is 1 or -1.  */
7420
7421       if ((STORE_FLAG_VALUE == 1 || STORE_FLAG_VALUE == -1)
7422           && (code == PLUS || code == IOR || code == XOR || code == MINUS
7423               || code == UMAX)
7424           && GET_CODE (XEXP (x, 0)) == MULT && GET_CODE (XEXP (x, 1)) == MULT)
7425         {
7426           rtx op0 = XEXP (XEXP (x, 0), 1);
7427           rtx op1 = XEXP (XEXP (x, 1), 1);
7428
7429           cond0 = XEXP (XEXP (x, 0), 0);
7430           cond1 = XEXP (XEXP (x, 1), 0);
7431
7432           if (COMPARISON_P (cond0)
7433               && COMPARISON_P (cond1)
7434               && ((GET_CODE (cond0) == reversed_comparison_code (cond1, NULL)
7435                    && rtx_equal_p (XEXP (cond0, 0), XEXP (cond1, 0))
7436                    && rtx_equal_p (XEXP (cond0, 1), XEXP (cond1, 1)))
7437                   || ((swap_condition (GET_CODE (cond0))
7438                        == reversed_comparison_code (cond1, NULL))
7439                       && rtx_equal_p (XEXP (cond0, 0), XEXP (cond1, 1))
7440                       && rtx_equal_p (XEXP (cond0, 1), XEXP (cond1, 0))))
7441               && ! side_effects_p (x))
7442             {
7443               *ptrue = simplify_gen_binary (MULT, mode, op0, const_true_rtx);
7444               *pfalse = simplify_gen_binary (MULT, mode,
7445                                              (code == MINUS
7446                                               ? simplify_gen_unary (NEG, mode,
7447                                                                     op1, mode)
7448                                               : op1),
7449                                               const_true_rtx);
7450               return cond0;
7451             }
7452         }
7453
7454       /* Similarly for MULT, AND and UMIN, except that for these the result
7455          is always zero.  */
7456       if ((STORE_FLAG_VALUE == 1 || STORE_FLAG_VALUE == -1)
7457           && (code == MULT || code == AND || code == UMIN)
7458           && GET_CODE (XEXP (x, 0)) == MULT && GET_CODE (XEXP (x, 1)) == MULT)
7459         {
7460           cond0 = XEXP (XEXP (x, 0), 0);
7461           cond1 = XEXP (XEXP (x, 1), 0);
7462
7463           if (COMPARISON_P (cond0)
7464               && COMPARISON_P (cond1)
7465               && ((GET_CODE (cond0) == reversed_comparison_code (cond1, NULL)
7466                    && rtx_equal_p (XEXP (cond0, 0), XEXP (cond1, 0))
7467                    && rtx_equal_p (XEXP (cond0, 1), XEXP (cond1, 1)))
7468                   || ((swap_condition (GET_CODE (cond0))
7469                        == reversed_comparison_code (cond1, NULL))
7470                       && rtx_equal_p (XEXP (cond0, 0), XEXP (cond1, 1))
7471                       && rtx_equal_p (XEXP (cond0, 1), XEXP (cond1, 0))))
7472               && ! side_effects_p (x))
7473             {
7474               *ptrue = *pfalse = const0_rtx;
7475               return cond0;
7476             }
7477         }
7478     }
7479
7480   else if (code == IF_THEN_ELSE)
7481     {
7482       /* If we have IF_THEN_ELSE already, extract the condition and
7483          canonicalize it if it is NE or EQ.  */
7484       cond0 = XEXP (x, 0);
7485       *ptrue = XEXP (x, 1), *pfalse = XEXP (x, 2);
7486       if (GET_CODE (cond0) == NE && XEXP (cond0, 1) == const0_rtx)
7487         return XEXP (cond0, 0);
7488       else if (GET_CODE (cond0) == EQ && XEXP (cond0, 1) == const0_rtx)
7489         {
7490           *ptrue = XEXP (x, 2), *pfalse = XEXP (x, 1);
7491           return XEXP (cond0, 0);
7492         }
7493       else
7494         return cond0;
7495     }
7496
7497   /* If X is a SUBREG, we can narrow both the true and false values
7498      if the inner expression, if there is a condition.  */
7499   else if (code == SUBREG
7500            && 0 != (cond0 = if_then_else_cond (SUBREG_REG (x),
7501                                                &true0, &false0)))
7502     {
7503       true0 = simplify_gen_subreg (mode, true0,
7504                                    GET_MODE (SUBREG_REG (x)), SUBREG_BYTE (x));
7505       false0 = simplify_gen_subreg (mode, false0,
7506                                     GET_MODE (SUBREG_REG (x)), SUBREG_BYTE (x));
7507       if (true0 && false0)
7508         {
7509           *ptrue = true0;
7510           *pfalse = false0;
7511           return cond0;
7512         }
7513     }
7514
7515   /* If X is a constant, this isn't special and will cause confusions
7516      if we treat it as such.  Likewise if it is equivalent to a constant.  */
7517   else if (CONSTANT_P (x)
7518            || ((cond0 = get_last_value (x)) != 0 && CONSTANT_P (cond0)))
7519     ;
7520
7521   /* If we're in BImode, canonicalize on 0 and STORE_FLAG_VALUE, as that
7522      will be least confusing to the rest of the compiler.  */
7523   else if (mode == BImode)
7524     {
7525       *ptrue = GEN_INT (STORE_FLAG_VALUE), *pfalse = const0_rtx;
7526       return x;
7527     }
7528
7529   /* If X is known to be either 0 or -1, those are the true and
7530      false values when testing X.  */
7531   else if (x == constm1_rtx || x == const0_rtx
7532            || (mode != VOIDmode
7533                && num_sign_bit_copies (x, mode) == GET_MODE_BITSIZE (mode)))
7534     {
7535       *ptrue = constm1_rtx, *pfalse = const0_rtx;
7536       return x;
7537     }
7538
7539   /* Likewise for 0 or a single bit.  */
7540   else if (SCALAR_INT_MODE_P (mode)
7541            && GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT
7542            && exact_log2 (nz = nonzero_bits (x, mode)) >= 0)
7543     {
7544       *ptrue = gen_int_mode (nz, mode), *pfalse = const0_rtx;
7545       return x;
7546     }
7547
7548   /* Otherwise fail; show no condition with true and false values the same.  */
7549   *ptrue = *pfalse = x;
7550   return 0;
7551 }
7552 \f
7553 /* Return the value of expression X given the fact that condition COND
7554    is known to be true when applied to REG as its first operand and VAL
7555    as its second.  X is known to not be shared and so can be modified in
7556    place.
7557
7558    We only handle the simplest cases, and specifically those cases that
7559    arise with IF_THEN_ELSE expressions.  */
7560
7561 static rtx
7562 known_cond (rtx x, enum rtx_code cond, rtx reg, rtx val)
7563 {
7564   enum rtx_code code = GET_CODE (x);
7565   rtx temp;
7566   const char *fmt;
7567   int i, j;
7568
7569   if (side_effects_p (x))
7570     return x;
7571
7572   /* If either operand of the condition is a floating point value,
7573      then we have to avoid collapsing an EQ comparison.  */
7574   if (cond == EQ
7575       && rtx_equal_p (x, reg)
7576       && ! FLOAT_MODE_P (GET_MODE (x))
7577       && ! FLOAT_MODE_P (GET_MODE (val)))
7578     return val;
7579
7580   if (cond == UNEQ && rtx_equal_p (x, reg))
7581     return val;
7582
7583   /* If X is (abs REG) and we know something about REG's relationship
7584      with zero, we may be able to simplify this.  */
7585
7586   if (code == ABS && rtx_equal_p (XEXP (x, 0), reg) && val == const0_rtx)
7587     switch (cond)
7588       {
7589       case GE:  case GT:  case EQ:
7590         return XEXP (x, 0);
7591       case LT:  case LE:
7592         return simplify_gen_unary (NEG, GET_MODE (XEXP (x, 0)),
7593                                    XEXP (x, 0),
7594                                    GET_MODE (XEXP (x, 0)));
7595       default:
7596         break;
7597       }
7598
7599   /* The only other cases we handle are MIN, MAX, and comparisons if the
7600      operands are the same as REG and VAL.  */
7601
7602   else if (COMPARISON_P (x) || COMMUTATIVE_ARITH_P (x))
7603     {
7604       if (rtx_equal_p (XEXP (x, 0), val))
7605         cond = swap_condition (cond), temp = val, val = reg, reg = temp;
7606
7607       if (rtx_equal_p (XEXP (x, 0), reg) && rtx_equal_p (XEXP (x, 1), val))
7608         {
7609           if (COMPARISON_P (x))
7610             {
7611               if (comparison_dominates_p (cond, code))
7612                 return const_true_rtx;
7613
7614               code = reversed_comparison_code (x, NULL);
7615               if (code != UNKNOWN
7616                   && comparison_dominates_p (cond, code))
7617                 return const0_rtx;
7618               else
7619                 return x;
7620             }
7621           else if (code == SMAX || code == SMIN
7622                    || code == UMIN || code == UMAX)
7623             {
7624               int unsignedp = (code == UMIN || code == UMAX);
7625
7626               /* Do not reverse the condition when it is NE or EQ.
7627                  This is because we cannot conclude anything about
7628                  the value of 'SMAX (x, y)' when x is not equal to y,
7629                  but we can when x equals y.  */
7630               if ((code == SMAX || code == UMAX)
7631                   && ! (cond == EQ || cond == NE))
7632                 cond = reverse_condition (cond);
7633
7634               switch (cond)
7635                 {
7636                 case GE:   case GT:
7637                   return unsignedp ? x : XEXP (x, 1);
7638                 case LE:   case LT:
7639                   return unsignedp ? x : XEXP (x, 0);
7640                 case GEU:  case GTU:
7641                   return unsignedp ? XEXP (x, 1) : x;
7642                 case LEU:  case LTU:
7643                   return unsignedp ? XEXP (x, 0) : x;
7644                 default:
7645                   break;
7646                 }
7647             }
7648         }
7649     }
7650   else if (code == SUBREG)
7651     {
7652       enum machine_mode inner_mode = GET_MODE (SUBREG_REG (x));
7653       rtx new, r = known_cond (SUBREG_REG (x), cond, reg, val);
7654
7655       if (SUBREG_REG (x) != r)
7656         {
7657           /* We must simplify subreg here, before we lose track of the
7658              original inner_mode.  */
7659           new = simplify_subreg (GET_MODE (x), r,
7660                                  inner_mode, SUBREG_BYTE (x));
7661           if (new)
7662             return new;
7663           else
7664             SUBST (SUBREG_REG (x), r);
7665         }
7666
7667       return x;
7668     }
7669   /* We don't have to handle SIGN_EXTEND here, because even in the
7670      case of replacing something with a modeless CONST_INT, a
7671      CONST_INT is already (supposed to be) a valid sign extension for
7672      its narrower mode, which implies it's already properly
7673      sign-extended for the wider mode.  Now, for ZERO_EXTEND, the
7674      story is different.  */
7675   else if (code == ZERO_EXTEND)
7676     {
7677       enum machine_mode inner_mode = GET_MODE (XEXP (x, 0));
7678       rtx new, r = known_cond (XEXP (x, 0), cond, reg, val);
7679
7680       if (XEXP (x, 0) != r)
7681         {
7682           /* We must simplify the zero_extend here, before we lose
7683              track of the original inner_mode.  */
7684           new = simplify_unary_operation (ZERO_EXTEND, GET_MODE (x),
7685                                           r, inner_mode);
7686           if (new)
7687             return new;
7688           else
7689             SUBST (XEXP (x, 0), r);
7690         }
7691
7692       return x;
7693     }
7694
7695   fmt = GET_RTX_FORMAT (code);
7696   for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
7697     {
7698       if (fmt[i] == 'e')
7699         SUBST (XEXP (x, i), known_cond (XEXP (x, i), cond, reg, val));
7700       else if (fmt[i] == 'E')
7701         for (j = XVECLEN (x, i) - 1; j >= 0; j--)
7702           SUBST (XVECEXP (x, i, j), known_cond (XVECEXP (x, i, j),
7703                                                 cond, reg, val));
7704     }
7705
7706   return x;
7707 }
7708 \f
7709 /* See if X and Y are equal for the purposes of seeing if we can rewrite an
7710    assignment as a field assignment.  */
7711
7712 static int
7713 rtx_equal_for_field_assignment_p (rtx x, rtx y)
7714 {
7715   if (x == y || rtx_equal_p (x, y))
7716     return 1;
7717
7718   if (x == 0 || y == 0 || GET_MODE (x) != GET_MODE (y))
7719     return 0;
7720
7721   /* Check for a paradoxical SUBREG of a MEM compared with the MEM.
7722      Note that all SUBREGs of MEM are paradoxical; otherwise they
7723      would have been rewritten.  */
7724   if (MEM_P (x) && GET_CODE (y) == SUBREG
7725       && MEM_P (SUBREG_REG (y))
7726       && rtx_equal_p (SUBREG_REG (y),
7727                       gen_lowpart (GET_MODE (SUBREG_REG (y)), x)))
7728     return 1;
7729
7730   if (MEM_P (y) && GET_CODE (x) == SUBREG
7731       && MEM_P (SUBREG_REG (x))
7732       && rtx_equal_p (SUBREG_REG (x),
7733                       gen_lowpart (GET_MODE (SUBREG_REG (x)), y)))
7734     return 1;
7735
7736   /* We used to see if get_last_value of X and Y were the same but that's
7737      not correct.  In one direction, we'll cause the assignment to have
7738      the wrong destination and in the case, we'll import a register into this
7739      insn that might have already have been dead.   So fail if none of the
7740      above cases are true.  */
7741   return 0;
7742 }
7743 \f
7744 /* See if X, a SET operation, can be rewritten as a bit-field assignment.
7745    Return that assignment if so.
7746
7747    We only handle the most common cases.  */
7748
7749 static rtx
7750 make_field_assignment (rtx x)
7751 {
7752   rtx dest = SET_DEST (x);
7753   rtx src = SET_SRC (x);
7754   rtx assign;
7755   rtx rhs, lhs;
7756   HOST_WIDE_INT c1;
7757   HOST_WIDE_INT pos;
7758   unsigned HOST_WIDE_INT len;
7759   rtx other;
7760   enum machine_mode mode;
7761
7762   /* If SRC was (and (not (ashift (const_int 1) POS)) DEST), this is
7763      a clear of a one-bit field.  We will have changed it to
7764      (and (rotate (const_int -2) POS) DEST), so check for that.  Also check
7765      for a SUBREG.  */
7766
7767   if (GET_CODE (src) == AND && GET_CODE (XEXP (src, 0)) == ROTATE
7768       && GET_CODE (XEXP (XEXP (src, 0), 0)) == CONST_INT
7769       && INTVAL (XEXP (XEXP (src, 0), 0)) == -2
7770       && rtx_equal_for_field_assignment_p (dest, XEXP (src, 1)))
7771     {
7772       assign = make_extraction (VOIDmode, dest, 0, XEXP (XEXP (src, 0), 1),
7773                                 1, 1, 1, 0);
7774       if (assign != 0)
7775         return gen_rtx_SET (VOIDmode, assign, const0_rtx);
7776       return x;
7777     }
7778
7779   if (GET_CODE (src) == AND && GET_CODE (XEXP (src, 0)) == SUBREG
7780       && subreg_lowpart_p (XEXP (src, 0))
7781       && (GET_MODE_SIZE (GET_MODE (XEXP (src, 0)))
7782           < GET_MODE_SIZE (GET_MODE (SUBREG_REG (XEXP (src, 0)))))
7783       && GET_CODE (SUBREG_REG (XEXP (src, 0))) == ROTATE
7784       && GET_CODE (XEXP (SUBREG_REG (XEXP (src, 0)), 0)) == CONST_INT
7785       && INTVAL (XEXP (SUBREG_REG (XEXP (src, 0)), 0)) == -2
7786       && rtx_equal_for_field_assignment_p (dest, XEXP (src, 1)))
7787     {
7788       assign = make_extraction (VOIDmode, dest, 0,
7789                                 XEXP (SUBREG_REG (XEXP (src, 0)), 1),
7790                                 1, 1, 1, 0);
7791       if (assign != 0)
7792         return gen_rtx_SET (VOIDmode, assign, const0_rtx);
7793       return x;
7794     }
7795
7796   /* If SRC is (ior (ashift (const_int 1) POS) DEST), this is a set of a
7797      one-bit field.  */
7798   if (GET_CODE (src) == IOR && GET_CODE (XEXP (src, 0)) == ASHIFT
7799       && XEXP (XEXP (src, 0), 0) == const1_rtx
7800       && rtx_equal_for_field_assignment_p (dest, XEXP (src, 1)))
7801     {
7802       assign = make_extraction (VOIDmode, dest, 0, XEXP (XEXP (src, 0), 1),
7803                                 1, 1, 1, 0);
7804       if (assign != 0)
7805         return gen_rtx_SET (VOIDmode, assign, const1_rtx);
7806       return x;
7807     }
7808
7809   /* If DEST is already a field assignment, i.e. ZERO_EXTRACT, and the
7810      SRC is an AND with all bits of that field set, then we can discard
7811      the AND.  */
7812   if (GET_CODE (dest) == ZERO_EXTRACT
7813       && GET_CODE (XEXP (dest, 1)) == CONST_INT
7814       && GET_CODE (src) == AND
7815       && GET_CODE (XEXP (src, 1)) == CONST_INT)
7816     {
7817       HOST_WIDE_INT width = INTVAL (XEXP (dest, 1));
7818       unsigned HOST_WIDE_INT and_mask = INTVAL (XEXP (src, 1));
7819       unsigned HOST_WIDE_INT ze_mask;
7820
7821       if (width >= HOST_BITS_PER_WIDE_INT)
7822         ze_mask = -1;
7823       else
7824         ze_mask = ((unsigned HOST_WIDE_INT)1 << width) - 1;
7825
7826       /* Complete overlap.  We can remove the source AND.  */
7827       if ((and_mask & ze_mask) == ze_mask)
7828         return gen_rtx_SET (VOIDmode, dest, XEXP (src, 0));
7829
7830       /* Partial overlap.  We can reduce the source AND.  */
7831       if ((and_mask & ze_mask) != and_mask)
7832         {
7833           mode = GET_MODE (src);
7834           src = gen_rtx_AND (mode, XEXP (src, 0),
7835                              gen_int_mode (and_mask & ze_mask, mode));
7836           return gen_rtx_SET (VOIDmode, dest, src);
7837         }
7838     }
7839
7840   /* The other case we handle is assignments into a constant-position
7841      field.  They look like (ior/xor (and DEST C1) OTHER).  If C1 represents
7842      a mask that has all one bits except for a group of zero bits and
7843      OTHER is known to have zeros where C1 has ones, this is such an
7844      assignment.  Compute the position and length from C1.  Shift OTHER
7845      to the appropriate position, force it to the required mode, and
7846      make the extraction.  Check for the AND in both operands.  */
7847
7848   if (GET_CODE (src) != IOR && GET_CODE (src) != XOR)
7849     return x;
7850
7851   rhs = expand_compound_operation (XEXP (src, 0));
7852   lhs = expand_compound_operation (XEXP (src, 1));
7853
7854   if (GET_CODE (rhs) == AND
7855       && GET_CODE (XEXP (rhs, 1)) == CONST_INT
7856       && rtx_equal_for_field_assignment_p (XEXP (rhs, 0), dest))
7857     c1 = INTVAL (XEXP (rhs, 1)), other = lhs;
7858   else if (GET_CODE (lhs) == AND
7859            && GET_CODE (XEXP (lhs, 1)) == CONST_INT
7860            && rtx_equal_for_field_assignment_p (XEXP (lhs, 0), dest))
7861     c1 = INTVAL (XEXP (lhs, 1)), other = rhs;
7862   else
7863     return x;
7864
7865   pos = get_pos_from_mask ((~c1) & GET_MODE_MASK (GET_MODE (dest)), &len);
7866   if (pos < 0 || pos + len > GET_MODE_BITSIZE (GET_MODE (dest))
7867       || GET_MODE_BITSIZE (GET_MODE (dest)) > HOST_BITS_PER_WIDE_INT
7868       || (c1 & nonzero_bits (other, GET_MODE (dest))) != 0)
7869     return x;
7870
7871   assign = make_extraction (VOIDmode, dest, pos, NULL_RTX, len, 1, 1, 0);
7872   if (assign == 0)
7873     return x;
7874
7875   /* The mode to use for the source is the mode of the assignment, or of
7876      what is inside a possible STRICT_LOW_PART.  */
7877   mode = (GET_CODE (assign) == STRICT_LOW_PART
7878           ? GET_MODE (XEXP (assign, 0)) : GET_MODE (assign));
7879
7880   /* Shift OTHER right POS places and make it the source, restricting it
7881      to the proper length and mode.  */
7882
7883   src = canon_reg_for_combine (simplify_shift_const (NULL_RTX, LSHIFTRT,
7884                                                      GET_MODE (src),
7885                                                      other, pos),
7886                                dest);
7887   src = force_to_mode (src, mode,
7888                        GET_MODE_BITSIZE (mode) >= HOST_BITS_PER_WIDE_INT
7889                        ? ~(unsigned HOST_WIDE_INT) 0
7890                        : ((unsigned HOST_WIDE_INT) 1 << len) - 1,
7891                        0);
7892
7893   /* If SRC is masked by an AND that does not make a difference in
7894      the value being stored, strip it.  */
7895   if (GET_CODE (assign) == ZERO_EXTRACT
7896       && GET_CODE (XEXP (assign, 1)) == CONST_INT
7897       && INTVAL (XEXP (assign, 1)) < HOST_BITS_PER_WIDE_INT
7898       && GET_CODE (src) == AND
7899       && GET_CODE (XEXP (src, 1)) == CONST_INT
7900       && ((unsigned HOST_WIDE_INT) INTVAL (XEXP (src, 1))
7901           == ((unsigned HOST_WIDE_INT) 1 << INTVAL (XEXP (assign, 1))) - 1))
7902     src = XEXP (src, 0);
7903
7904   return gen_rtx_SET (VOIDmode, assign, src);
7905 }
7906 \f
7907 /* See if X is of the form (+ (* a c) (* b c)) and convert to (* (+ a b) c)
7908    if so.  */
7909
7910 static rtx
7911 apply_distributive_law (rtx x)
7912 {
7913   enum rtx_code code = GET_CODE (x);
7914   enum rtx_code inner_code;
7915   rtx lhs, rhs, other;
7916   rtx tem;
7917
7918   /* Distributivity is not true for floating point as it can change the
7919      value.  So we don't do it unless -funsafe-math-optimizations.  */
7920   if (FLOAT_MODE_P (GET_MODE (x))
7921       && ! flag_unsafe_math_optimizations)
7922     return x;
7923
7924   /* The outer operation can only be one of the following:  */
7925   if (code != IOR && code != AND && code != XOR
7926       && code != PLUS && code != MINUS)
7927     return x;
7928
7929   lhs = XEXP (x, 0);
7930   rhs = XEXP (x, 1);
7931
7932   /* If either operand is a primitive we can't do anything, so get out
7933      fast.  */
7934   if (OBJECT_P (lhs) || OBJECT_P (rhs))
7935     return x;
7936
7937   lhs = expand_compound_operation (lhs);
7938   rhs = expand_compound_operation (rhs);
7939   inner_code = GET_CODE (lhs);
7940   if (inner_code != GET_CODE (rhs))
7941     return x;
7942
7943   /* See if the inner and outer operations distribute.  */
7944   switch (inner_code)
7945     {
7946     case LSHIFTRT:
7947     case ASHIFTRT:
7948     case AND:
7949     case IOR:
7950       /* These all distribute except over PLUS.  */
7951       if (code == PLUS || code == MINUS)
7952         return x;
7953       break;
7954
7955     case MULT:
7956       if (code != PLUS && code != MINUS)
7957         return x;
7958       break;
7959
7960     case ASHIFT:
7961       /* This is also a multiply, so it distributes over everything.  */
7962       break;
7963
7964     case SUBREG:
7965       /* Non-paradoxical SUBREGs distributes over all operations,
7966          provided the inner modes and byte offsets are the same, this
7967          is an extraction of a low-order part, we don't convert an fp
7968          operation to int or vice versa, this is not a vector mode,
7969          and we would not be converting a single-word operation into a
7970          multi-word operation.  The latter test is not required, but
7971          it prevents generating unneeded multi-word operations.  Some
7972          of the previous tests are redundant given the latter test,
7973          but are retained because they are required for correctness.
7974
7975          We produce the result slightly differently in this case.  */
7976
7977       if (GET_MODE (SUBREG_REG (lhs)) != GET_MODE (SUBREG_REG (rhs))
7978           || SUBREG_BYTE (lhs) != SUBREG_BYTE (rhs)
7979           || ! subreg_lowpart_p (lhs)
7980           || (GET_MODE_CLASS (GET_MODE (lhs))
7981               != GET_MODE_CLASS (GET_MODE (SUBREG_REG (lhs))))
7982           || (GET_MODE_SIZE (GET_MODE (lhs))
7983               > GET_MODE_SIZE (GET_MODE (SUBREG_REG (lhs))))
7984           || VECTOR_MODE_P (GET_MODE (lhs))
7985           || GET_MODE_SIZE (GET_MODE (SUBREG_REG (lhs))) > UNITS_PER_WORD
7986           /* Result might need to be truncated.  Don't change mode if
7987              explicit truncation is needed.  */
7988           || !TRULY_NOOP_TRUNCATION
7989                (GET_MODE_BITSIZE (GET_MODE (x)),
7990                 GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (lhs)))))
7991         return x;
7992
7993       tem = simplify_gen_binary (code, GET_MODE (SUBREG_REG (lhs)),
7994                                  SUBREG_REG (lhs), SUBREG_REG (rhs));
7995       return gen_lowpart (GET_MODE (x), tem);
7996
7997     default:
7998       return x;
7999     }
8000
8001   /* Set LHS and RHS to the inner operands (A and B in the example
8002      above) and set OTHER to the common operand (C in the example).
8003      There is only one way to do this unless the inner operation is
8004      commutative.  */
8005   if (COMMUTATIVE_ARITH_P (lhs)
8006       && rtx_equal_p (XEXP (lhs, 0), XEXP (rhs, 0)))
8007     other = XEXP (lhs, 0), lhs = XEXP (lhs, 1), rhs = XEXP (rhs, 1);
8008   else if (COMMUTATIVE_ARITH_P (lhs)
8009            && rtx_equal_p (XEXP (lhs, 0), XEXP (rhs, 1)))
8010     other = XEXP (lhs, 0), lhs = XEXP (lhs, 1), rhs = XEXP (rhs, 0);
8011   else if (COMMUTATIVE_ARITH_P (lhs)
8012            && rtx_equal_p (XEXP (lhs, 1), XEXP (rhs, 0)))
8013     other = XEXP (lhs, 1), lhs = XEXP (lhs, 0), rhs = XEXP (rhs, 1);
8014   else if (rtx_equal_p (XEXP (lhs, 1), XEXP (rhs, 1)))
8015     other = XEXP (lhs, 1), lhs = XEXP (lhs, 0), rhs = XEXP (rhs, 0);
8016   else
8017     return x;
8018
8019   /* Form the new inner operation, seeing if it simplifies first.  */
8020   tem = simplify_gen_binary (code, GET_MODE (x), lhs, rhs);
8021
8022   /* There is one exception to the general way of distributing:
8023      (a | c) ^ (b | c) -> (a ^ b) & ~c  */
8024   if (code == XOR && inner_code == IOR)
8025     {
8026       inner_code = AND;
8027       other = simplify_gen_unary (NOT, GET_MODE (x), other, GET_MODE (x));
8028     }
8029
8030   /* We may be able to continuing distributing the result, so call
8031      ourselves recursively on the inner operation before forming the
8032      outer operation, which we return.  */
8033   return simplify_gen_binary (inner_code, GET_MODE (x),
8034                               apply_distributive_law (tem), other);
8035 }
8036
8037 /* See if X is of the form (* (+ A B) C), and if so convert to
8038    (+ (* A C) (* B C)) and try to simplify.
8039
8040    Most of the time, this results in no change.  However, if some of
8041    the operands are the same or inverses of each other, simplifications
8042    will result.
8043
8044    For example, (and (ior A B) (not B)) can occur as the result of
8045    expanding a bit field assignment.  When we apply the distributive
8046    law to this, we get (ior (and (A (not B))) (and (B (not B)))),
8047    which then simplifies to (and (A (not B))).
8048
8049    Note that no checks happen on the validity of applying the inverse
8050    distributive law.  This is pointless since we can do it in the
8051    few places where this routine is called.
8052
8053    N is the index of the term that is decomposed (the arithmetic operation,
8054    i.e. (+ A B) in the first example above).  !N is the index of the term that
8055    is distributed, i.e. of C in the first example above.  */
8056 static rtx
8057 distribute_and_simplify_rtx (rtx x, int n)
8058 {
8059   enum machine_mode mode;
8060   enum rtx_code outer_code, inner_code;
8061   rtx decomposed, distributed, inner_op0, inner_op1, new_op0, new_op1, tmp;
8062
8063   decomposed = XEXP (x, n);
8064   if (!ARITHMETIC_P (decomposed))
8065     return NULL_RTX;
8066
8067   mode = GET_MODE (x);
8068   outer_code = GET_CODE (x);
8069   distributed = XEXP (x, !n);
8070
8071   inner_code = GET_CODE (decomposed);
8072   inner_op0 = XEXP (decomposed, 0);
8073   inner_op1 = XEXP (decomposed, 1);
8074
8075   /* Special case (and (xor B C) (not A)), which is equivalent to
8076      (xor (ior A B) (ior A C))  */
8077   if (outer_code == AND && inner_code == XOR && GET_CODE (distributed) == NOT)
8078     {
8079       distributed = XEXP (distributed, 0);
8080       outer_code = IOR;
8081     }
8082
8083   if (n == 0)
8084     {
8085       /* Distribute the second term.  */
8086       new_op0 = simplify_gen_binary (outer_code, mode, inner_op0, distributed);
8087       new_op1 = simplify_gen_binary (outer_code, mode, inner_op1, distributed);
8088     }
8089   else
8090     {
8091       /* Distribute the first term.  */
8092       new_op0 = simplify_gen_binary (outer_code, mode, distributed, inner_op0);
8093       new_op1 = simplify_gen_binary (outer_code, mode, distributed, inner_op1);
8094     }
8095
8096   tmp = apply_distributive_law (simplify_gen_binary (inner_code, mode,
8097                                                      new_op0, new_op1));
8098   if (GET_CODE (tmp) != outer_code
8099       && rtx_cost (tmp, SET) < rtx_cost (x, SET))
8100     return tmp;
8101
8102   return NULL_RTX;
8103 }
8104 \f
8105 /* Simplify a logical `and' of VAROP with the constant CONSTOP, to be done
8106    in MODE.  Return an equivalent form, if different from (and VAROP
8107    (const_int CONSTOP)).  Otherwise, return NULL_RTX.  */
8108
8109 static rtx
8110 simplify_and_const_int_1 (enum machine_mode mode, rtx varop,
8111                           unsigned HOST_WIDE_INT constop)
8112 {
8113   unsigned HOST_WIDE_INT nonzero;
8114   unsigned HOST_WIDE_INT orig_constop;
8115   rtx orig_varop;
8116   int i;
8117
8118   orig_varop = varop;
8119   orig_constop = constop;
8120   if (GET_CODE (varop) == CLOBBER)
8121     return NULL_RTX;
8122
8123   /* Simplify VAROP knowing that we will be only looking at some of the
8124      bits in it.
8125
8126      Note by passing in CONSTOP, we guarantee that the bits not set in
8127      CONSTOP are not significant and will never be examined.  We must
8128      ensure that is the case by explicitly masking out those bits
8129      before returning.  */
8130   varop = force_to_mode (varop, mode, constop, 0);
8131
8132   /* If VAROP is a CLOBBER, we will fail so return it.  */
8133   if (GET_CODE (varop) == CLOBBER)
8134     return varop;
8135
8136   /* If VAROP is a CONST_INT, then we need to apply the mask in CONSTOP
8137      to VAROP and return the new constant.  */
8138   if (GET_CODE (varop) == CONST_INT)
8139     return gen_int_mode (INTVAL (varop) & constop, mode);
8140
8141   /* See what bits may be nonzero in VAROP.  Unlike the general case of
8142      a call to nonzero_bits, here we don't care about bits outside
8143      MODE.  */
8144
8145   nonzero = nonzero_bits (varop, mode) & GET_MODE_MASK (mode);
8146
8147   /* Turn off all bits in the constant that are known to already be zero.
8148      Thus, if the AND isn't needed at all, we will have CONSTOP == NONZERO_BITS
8149      which is tested below.  */
8150
8151   constop &= nonzero;
8152
8153   /* If we don't have any bits left, return zero.  */
8154   if (constop == 0)
8155     return const0_rtx;
8156
8157   /* If VAROP is a NEG of something known to be zero or 1 and CONSTOP is
8158      a power of two, we can replace this with an ASHIFT.  */
8159   if (GET_CODE (varop) == NEG && nonzero_bits (XEXP (varop, 0), mode) == 1
8160       && (i = exact_log2 (constop)) >= 0)
8161     return simplify_shift_const (NULL_RTX, ASHIFT, mode, XEXP (varop, 0), i);
8162
8163   /* If VAROP is an IOR or XOR, apply the AND to both branches of the IOR
8164      or XOR, then try to apply the distributive law.  This may eliminate
8165      operations if either branch can be simplified because of the AND.
8166      It may also make some cases more complex, but those cases probably
8167      won't match a pattern either with or without this.  */
8168
8169   if (GET_CODE (varop) == IOR || GET_CODE (varop) == XOR)
8170     return
8171       gen_lowpart
8172         (mode,
8173          apply_distributive_law
8174          (simplify_gen_binary (GET_CODE (varop), GET_MODE (varop),
8175                                simplify_and_const_int (NULL_RTX,
8176                                                        GET_MODE (varop),
8177                                                        XEXP (varop, 0),
8178                                                        constop),
8179                                simplify_and_const_int (NULL_RTX,
8180                                                        GET_MODE (varop),
8181                                                        XEXP (varop, 1),
8182                                                        constop))));
8183
8184   /* If VAROP is PLUS, and the constant is a mask of low bits, distribute
8185      the AND and see if one of the operands simplifies to zero.  If so, we
8186      may eliminate it.  */
8187
8188   if (GET_CODE (varop) == PLUS
8189       && exact_log2 (constop + 1) >= 0)
8190     {
8191       rtx o0, o1;
8192
8193       o0 = simplify_and_const_int (NULL_RTX, mode, XEXP (varop, 0), constop);
8194       o1 = simplify_and_const_int (NULL_RTX, mode, XEXP (varop, 1), constop);
8195       if (o0 == const0_rtx)
8196         return o1;
8197       if (o1 == const0_rtx)
8198         return o0;
8199     }
8200
8201   /* Make a SUBREG if necessary.  If we can't make it, fail.  */
8202   varop = gen_lowpart (mode, varop);
8203   if (varop == NULL_RTX || GET_CODE (varop) == CLOBBER)
8204     return NULL_RTX;
8205
8206   /* If we are only masking insignificant bits, return VAROP.  */
8207   if (constop == nonzero)
8208     return varop;
8209
8210   if (varop == orig_varop && constop == orig_constop)
8211     return NULL_RTX;
8212
8213   /* Otherwise, return an AND.  */
8214   return simplify_gen_binary (AND, mode, varop, gen_int_mode (constop, mode));
8215 }
8216
8217
8218 /* We have X, a logical `and' of VAROP with the constant CONSTOP, to be done
8219    in MODE.
8220
8221    Return an equivalent form, if different from X.  Otherwise, return X.  If
8222    X is zero, we are to always construct the equivalent form.  */
8223
8224 static rtx
8225 simplify_and_const_int (rtx x, enum machine_mode mode, rtx varop,
8226                         unsigned HOST_WIDE_INT constop)
8227 {
8228   rtx tem = simplify_and_const_int_1 (mode, varop, constop);
8229   if (tem)
8230     return tem;
8231
8232   if (!x)
8233     x = simplify_gen_binary (AND, GET_MODE (varop), varop,
8234                              gen_int_mode (constop, mode));
8235   if (GET_MODE (x) != mode)
8236     x = gen_lowpart (mode, x);
8237   return x;
8238 }
8239 \f
8240 /* Given a REG, X, compute which bits in X can be nonzero.
8241    We don't care about bits outside of those defined in MODE.
8242
8243    For most X this is simply GET_MODE_MASK (GET_MODE (MODE)), but if X is
8244    a shift, AND, or zero_extract, we can do better.  */
8245
8246 static rtx
8247 reg_nonzero_bits_for_combine (rtx x, enum machine_mode mode,
8248                               rtx known_x ATTRIBUTE_UNUSED,
8249                               enum machine_mode known_mode ATTRIBUTE_UNUSED,
8250                               unsigned HOST_WIDE_INT known_ret ATTRIBUTE_UNUSED,
8251                               unsigned HOST_WIDE_INT *nonzero)
8252 {
8253   rtx tem;
8254
8255   /* If X is a register whose nonzero bits value is current, use it.
8256      Otherwise, if X is a register whose value we can find, use that
8257      value.  Otherwise, use the previously-computed global nonzero bits
8258      for this register.  */
8259
8260   if (reg_stat[REGNO (x)].last_set_value != 0
8261       && (reg_stat[REGNO (x)].last_set_mode == mode
8262           || (GET_MODE_CLASS (reg_stat[REGNO (x)].last_set_mode) == MODE_INT
8263               && GET_MODE_CLASS (mode) == MODE_INT))
8264       && (reg_stat[REGNO (x)].last_set_label == label_tick
8265           || (REGNO (x) >= FIRST_PSEUDO_REGISTER
8266               && REG_N_SETS (REGNO (x)) == 1
8267               && ! REGNO_REG_SET_P
8268                  (ENTRY_BLOCK_PTR->next_bb->il.rtl->global_live_at_start,
8269                   REGNO (x))))
8270       && INSN_CUID (reg_stat[REGNO (x)].last_set) < subst_low_cuid)
8271     {
8272       *nonzero &= reg_stat[REGNO (x)].last_set_nonzero_bits;
8273       return NULL;
8274     }
8275
8276   tem = get_last_value (x);
8277
8278   if (tem)
8279     {
8280 #ifdef SHORT_IMMEDIATES_SIGN_EXTEND
8281       /* If X is narrower than MODE and TEM is a non-negative
8282          constant that would appear negative in the mode of X,
8283          sign-extend it for use in reg_nonzero_bits because some
8284          machines (maybe most) will actually do the sign-extension
8285          and this is the conservative approach.
8286
8287          ??? For 2.5, try to tighten up the MD files in this regard
8288          instead of this kludge.  */
8289
8290       if (GET_MODE_BITSIZE (GET_MODE (x)) < GET_MODE_BITSIZE (mode)
8291           && GET_CODE (tem) == CONST_INT
8292           && INTVAL (tem) > 0
8293           && 0 != (INTVAL (tem)
8294                    & ((HOST_WIDE_INT) 1
8295                       << (GET_MODE_BITSIZE (GET_MODE (x)) - 1))))
8296         tem = GEN_INT (INTVAL (tem)
8297                        | ((HOST_WIDE_INT) (-1)
8298                           << GET_MODE_BITSIZE (GET_MODE (x))));
8299 #endif
8300       return tem;
8301     }
8302   else if (nonzero_sign_valid && reg_stat[REGNO (x)].nonzero_bits)
8303     {
8304       unsigned HOST_WIDE_INT mask = reg_stat[REGNO (x)].nonzero_bits;
8305
8306       if (GET_MODE_BITSIZE (GET_MODE (x)) < GET_MODE_BITSIZE (mode))
8307         /* We don't know anything about the upper bits.  */
8308         mask |= GET_MODE_MASK (mode) ^ GET_MODE_MASK (GET_MODE (x));
8309       *nonzero &= mask;
8310     }
8311
8312   return NULL;
8313 }
8314
8315 /* Return the number of bits at the high-order end of X that are known to
8316    be equal to the sign bit.  X will be used in mode MODE; if MODE is
8317    VOIDmode, X will be used in its own mode.  The returned value  will always
8318    be between 1 and the number of bits in MODE.  */
8319
8320 static rtx
8321 reg_num_sign_bit_copies_for_combine (rtx x, enum machine_mode mode,
8322                                      rtx known_x ATTRIBUTE_UNUSED,
8323                                      enum machine_mode known_mode
8324                                      ATTRIBUTE_UNUSED,
8325                                      unsigned int known_ret ATTRIBUTE_UNUSED,
8326                                      unsigned int *result)
8327 {
8328   rtx tem;
8329
8330   if (reg_stat[REGNO (x)].last_set_value != 0
8331       && reg_stat[REGNO (x)].last_set_mode == mode
8332       && (reg_stat[REGNO (x)].last_set_label == label_tick
8333           || (REGNO (x) >= FIRST_PSEUDO_REGISTER
8334               && REG_N_SETS (REGNO (x)) == 1
8335               && ! REGNO_REG_SET_P
8336                  (ENTRY_BLOCK_PTR->next_bb->il.rtl->global_live_at_start,
8337                   REGNO (x))))
8338       && INSN_CUID (reg_stat[REGNO (x)].last_set) < subst_low_cuid)
8339     {
8340       *result = reg_stat[REGNO (x)].last_set_sign_bit_copies;
8341       return NULL;
8342     }
8343
8344   tem = get_last_value (x);
8345   if (tem != 0)
8346     return tem;
8347
8348   if (nonzero_sign_valid && reg_stat[REGNO (x)].sign_bit_copies != 0
8349       && GET_MODE_BITSIZE (GET_MODE (x)) == GET_MODE_BITSIZE (mode))
8350     *result = reg_stat[REGNO (x)].sign_bit_copies;
8351
8352   return NULL;
8353 }
8354 \f
8355 /* Return the number of "extended" bits there are in X, when interpreted
8356    as a quantity in MODE whose signedness is indicated by UNSIGNEDP.  For
8357    unsigned quantities, this is the number of high-order zero bits.
8358    For signed quantities, this is the number of copies of the sign bit
8359    minus 1.  In both case, this function returns the number of "spare"
8360    bits.  For example, if two quantities for which this function returns
8361    at least 1 are added, the addition is known not to overflow.
8362
8363    This function will always return 0 unless called during combine, which
8364    implies that it must be called from a define_split.  */
8365
8366 unsigned int
8367 extended_count (rtx x, enum machine_mode mode, int unsignedp)
8368 {
8369   if (nonzero_sign_valid == 0)
8370     return 0;
8371
8372   return (unsignedp
8373           ? (GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT
8374              ? (unsigned int) (GET_MODE_BITSIZE (mode) - 1
8375                                - floor_log2 (nonzero_bits (x, mode)))
8376              : 0)
8377           : num_sign_bit_copies (x, mode) - 1);
8378 }
8379 \f
8380 /* This function is called from `simplify_shift_const' to merge two
8381    outer operations.  Specifically, we have already found that we need
8382    to perform operation *POP0 with constant *PCONST0 at the outermost
8383    position.  We would now like to also perform OP1 with constant CONST1
8384    (with *POP0 being done last).
8385
8386    Return 1 if we can do the operation and update *POP0 and *PCONST0 with
8387    the resulting operation.  *PCOMP_P is set to 1 if we would need to
8388    complement the innermost operand, otherwise it is unchanged.
8389
8390    MODE is the mode in which the operation will be done.  No bits outside
8391    the width of this mode matter.  It is assumed that the width of this mode
8392    is smaller than or equal to HOST_BITS_PER_WIDE_INT.
8393
8394    If *POP0 or OP1 are UNKNOWN, it means no operation is required.  Only NEG, PLUS,
8395    IOR, XOR, and AND are supported.  We may set *POP0 to SET if the proper
8396    result is simply *PCONST0.
8397
8398    If the resulting operation cannot be expressed as one operation, we
8399    return 0 and do not change *POP0, *PCONST0, and *PCOMP_P.  */
8400
8401 static int
8402 merge_outer_ops (enum rtx_code *pop0, HOST_WIDE_INT *pconst0, enum rtx_code op1, HOST_WIDE_INT const1, enum machine_mode mode, int *pcomp_p)
8403 {
8404   enum rtx_code op0 = *pop0;
8405   HOST_WIDE_INT const0 = *pconst0;
8406
8407   const0 &= GET_MODE_MASK (mode);
8408   const1 &= GET_MODE_MASK (mode);
8409
8410   /* If OP0 is an AND, clear unimportant bits in CONST1.  */
8411   if (op0 == AND)
8412     const1 &= const0;
8413
8414   /* If OP0 or OP1 is UNKNOWN, this is easy.  Similarly if they are the same or
8415      if OP0 is SET.  */
8416
8417   if (op1 == UNKNOWN || op0 == SET)
8418     return 1;
8419
8420   else if (op0 == UNKNOWN)
8421     op0 = op1, const0 = const1;
8422
8423   else if (op0 == op1)
8424     {
8425       switch (op0)
8426         {
8427         case AND:
8428           const0 &= const1;
8429           break;
8430         case IOR:
8431           const0 |= const1;
8432           break;
8433         case XOR:
8434           const0 ^= const1;
8435           break;
8436         case PLUS:
8437           const0 += const1;
8438           break;
8439         case NEG:
8440           op0 = UNKNOWN;
8441           break;
8442         default:
8443           break;
8444         }
8445     }
8446
8447   /* Otherwise, if either is a PLUS or NEG, we can't do anything.  */
8448   else if (op0 == PLUS || op1 == PLUS || op0 == NEG || op1 == NEG)
8449     return 0;
8450
8451   /* If the two constants aren't the same, we can't do anything.  The
8452      remaining six cases can all be done.  */
8453   else if (const0 != const1)
8454     return 0;
8455
8456   else
8457     switch (op0)
8458       {
8459       case IOR:
8460         if (op1 == AND)
8461           /* (a & b) | b == b */
8462           op0 = SET;
8463         else /* op1 == XOR */
8464           /* (a ^ b) | b == a | b */
8465           {;}
8466         break;
8467
8468       case XOR:
8469         if (op1 == AND)
8470           /* (a & b) ^ b == (~a) & b */
8471           op0 = AND, *pcomp_p = 1;
8472         else /* op1 == IOR */
8473           /* (a | b) ^ b == a & ~b */
8474           op0 = AND, const0 = ~const0;
8475         break;
8476
8477       case AND:
8478         if (op1 == IOR)
8479           /* (a | b) & b == b */
8480         op0 = SET;
8481         else /* op1 == XOR */
8482           /* (a ^ b) & b) == (~a) & b */
8483           *pcomp_p = 1;
8484         break;
8485       default:
8486         break;
8487       }
8488
8489   /* Check for NO-OP cases.  */
8490   const0 &= GET_MODE_MASK (mode);
8491   if (const0 == 0
8492       && (op0 == IOR || op0 == XOR || op0 == PLUS))
8493     op0 = UNKNOWN;
8494   else if (const0 == 0 && op0 == AND)
8495     op0 = SET;
8496   else if ((unsigned HOST_WIDE_INT) const0 == GET_MODE_MASK (mode)
8497            && op0 == AND)
8498     op0 = UNKNOWN;
8499
8500   /* ??? Slightly redundant with the above mask, but not entirely.
8501      Moving this above means we'd have to sign-extend the mode mask
8502      for the final test.  */
8503   const0 = trunc_int_for_mode (const0, mode);
8504
8505   *pop0 = op0;
8506   *pconst0 = const0;
8507
8508   return 1;
8509 }
8510 \f
8511 /* Simplify a shift of VAROP by COUNT bits.  CODE says what kind of shift.
8512    The result of the shift is RESULT_MODE.  Return NULL_RTX if we cannot
8513    simplify it.  Otherwise, return a simplified value.
8514
8515    The shift is normally computed in the widest mode we find in VAROP, as
8516    long as it isn't a different number of words than RESULT_MODE.  Exceptions
8517    are ASHIFTRT and ROTATE, which are always done in their original mode.  */
8518
8519 static rtx
8520 simplify_shift_const_1 (enum rtx_code code, enum machine_mode result_mode,
8521                         rtx varop, int orig_count)
8522 {
8523   enum rtx_code orig_code = code;
8524   rtx orig_varop = varop;
8525   int count;
8526   enum machine_mode mode = result_mode;
8527   enum machine_mode shift_mode, tmode;
8528   unsigned int mode_words
8529     = (GET_MODE_SIZE (mode) + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD;
8530   /* We form (outer_op (code varop count) (outer_const)).  */
8531   enum rtx_code outer_op = UNKNOWN;
8532   HOST_WIDE_INT outer_const = 0;
8533   int complement_p = 0;
8534   rtx new, x;
8535
8536   /* Make sure and truncate the "natural" shift on the way in.  We don't
8537      want to do this inside the loop as it makes it more difficult to
8538      combine shifts.  */
8539   if (SHIFT_COUNT_TRUNCATED)
8540     orig_count &= GET_MODE_BITSIZE (mode) - 1;
8541
8542   /* If we were given an invalid count, don't do anything except exactly
8543      what was requested.  */
8544
8545   if (orig_count < 0 || orig_count >= (int) GET_MODE_BITSIZE (mode))
8546     return NULL_RTX;
8547
8548   count = orig_count;
8549
8550   /* Unless one of the branches of the `if' in this loop does a `continue',
8551      we will `break' the loop after the `if'.  */
8552
8553   while (count != 0)
8554     {
8555       /* If we have an operand of (clobber (const_int 0)), fail.  */
8556       if (GET_CODE (varop) == CLOBBER)
8557         return NULL_RTX;
8558
8559       /* If we discovered we had to complement VAROP, leave.  Making a NOT
8560          here would cause an infinite loop.  */
8561       if (complement_p)
8562         break;
8563
8564       /* Convert ROTATERT to ROTATE.  */
8565       if (code == ROTATERT)
8566         {
8567           unsigned int bitsize = GET_MODE_BITSIZE (result_mode);;
8568           code = ROTATE;
8569           if (VECTOR_MODE_P (result_mode))
8570             count = bitsize / GET_MODE_NUNITS (result_mode) - count;
8571           else
8572             count = bitsize - count;
8573         }
8574
8575       /* We need to determine what mode we will do the shift in.  If the
8576          shift is a right shift or a ROTATE, we must always do it in the mode
8577          it was originally done in.  Otherwise, we can do it in MODE, the
8578          widest mode encountered.  */
8579       shift_mode
8580         = (code == ASHIFTRT || code == LSHIFTRT || code == ROTATE
8581            ? result_mode : mode);
8582
8583       /* Handle cases where the count is greater than the size of the mode
8584          minus 1.  For ASHIFT, use the size minus one as the count (this can
8585          occur when simplifying (lshiftrt (ashiftrt ..))).  For rotates,
8586          take the count modulo the size.  For other shifts, the result is
8587          zero.
8588
8589          Since these shifts are being produced by the compiler by combining
8590          multiple operations, each of which are defined, we know what the
8591          result is supposed to be.  */
8592
8593       if (count > (GET_MODE_BITSIZE (shift_mode) - 1))
8594         {
8595           if (code == ASHIFTRT)
8596             count = GET_MODE_BITSIZE (shift_mode) - 1;
8597           else if (code == ROTATE || code == ROTATERT)
8598             count %= GET_MODE_BITSIZE (shift_mode);
8599           else
8600             {
8601               /* We can't simply return zero because there may be an
8602                  outer op.  */
8603               varop = const0_rtx;
8604               count = 0;
8605               break;
8606             }
8607         }
8608
8609       /* An arithmetic right shift of a quantity known to be -1 or 0
8610          is a no-op.  */
8611       if (code == ASHIFTRT
8612           && (num_sign_bit_copies (varop, shift_mode)
8613               == GET_MODE_BITSIZE (shift_mode)))
8614         {
8615           count = 0;
8616           break;
8617         }
8618
8619       /* If we are doing an arithmetic right shift and discarding all but
8620          the sign bit copies, this is equivalent to doing a shift by the
8621          bitsize minus one.  Convert it into that shift because it will often
8622          allow other simplifications.  */
8623
8624       if (code == ASHIFTRT
8625           && (count + num_sign_bit_copies (varop, shift_mode)
8626               >= GET_MODE_BITSIZE (shift_mode)))
8627         count = GET_MODE_BITSIZE (shift_mode) - 1;
8628
8629       /* We simplify the tests below and elsewhere by converting
8630          ASHIFTRT to LSHIFTRT if we know the sign bit is clear.
8631          `make_compound_operation' will convert it to an ASHIFTRT for
8632          those machines (such as VAX) that don't have an LSHIFTRT.  */
8633       if (GET_MODE_BITSIZE (shift_mode) <= HOST_BITS_PER_WIDE_INT
8634           && code == ASHIFTRT
8635           && ((nonzero_bits (varop, shift_mode)
8636                & ((HOST_WIDE_INT) 1 << (GET_MODE_BITSIZE (shift_mode) - 1)))
8637               == 0))
8638         code = LSHIFTRT;
8639
8640       if (((code == LSHIFTRT
8641             && GET_MODE_BITSIZE (shift_mode) <= HOST_BITS_PER_WIDE_INT
8642             && !(nonzero_bits (varop, shift_mode) >> count))
8643            || (code == ASHIFT
8644                && GET_MODE_BITSIZE (shift_mode) <= HOST_BITS_PER_WIDE_INT
8645                && !((nonzero_bits (varop, shift_mode) << count)
8646                     & GET_MODE_MASK (shift_mode))))
8647           && !side_effects_p (varop))
8648         varop = const0_rtx;
8649
8650       switch (GET_CODE (varop))
8651         {
8652         case SIGN_EXTEND:
8653         case ZERO_EXTEND:
8654         case SIGN_EXTRACT:
8655         case ZERO_EXTRACT:
8656           new = expand_compound_operation (varop);
8657           if (new != varop)
8658             {
8659               varop = new;
8660               continue;
8661             }
8662           break;
8663
8664         case MEM:
8665           /* If we have (xshiftrt (mem ...) C) and C is MODE_WIDTH
8666              minus the width of a smaller mode, we can do this with a
8667              SIGN_EXTEND or ZERO_EXTEND from the narrower memory location.  */
8668           if ((code == ASHIFTRT || code == LSHIFTRT)
8669               && ! mode_dependent_address_p (XEXP (varop, 0))
8670               && ! MEM_VOLATILE_P (varop)
8671               && (tmode = mode_for_size (GET_MODE_BITSIZE (mode) - count,
8672                                          MODE_INT, 1)) != BLKmode)
8673             {
8674               new = adjust_address_nv (varop, tmode,
8675                                        BYTES_BIG_ENDIAN ? 0
8676                                        : count / BITS_PER_UNIT);
8677
8678               varop = gen_rtx_fmt_e (code == ASHIFTRT ? SIGN_EXTEND
8679                                      : ZERO_EXTEND, mode, new);
8680               count = 0;
8681               continue;
8682             }
8683           break;
8684
8685         case SUBREG:
8686           /* If VAROP is a SUBREG, strip it as long as the inner operand has
8687              the same number of words as what we've seen so far.  Then store
8688              the widest mode in MODE.  */
8689           if (subreg_lowpart_p (varop)
8690               && (GET_MODE_SIZE (GET_MODE (SUBREG_REG (varop)))
8691                   > GET_MODE_SIZE (GET_MODE (varop)))
8692               && (unsigned int) ((GET_MODE_SIZE (GET_MODE (SUBREG_REG (varop)))
8693                                   + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD)
8694                  == mode_words)
8695             {
8696               varop = SUBREG_REG (varop);
8697               if (GET_MODE_SIZE (GET_MODE (varop)) > GET_MODE_SIZE (mode))
8698                 mode = GET_MODE (varop);
8699               continue;
8700             }
8701           break;
8702
8703         case MULT:
8704           /* Some machines use MULT instead of ASHIFT because MULT
8705              is cheaper.  But it is still better on those machines to
8706              merge two shifts into one.  */
8707           if (GET_CODE (XEXP (varop, 1)) == CONST_INT
8708               && exact_log2 (INTVAL (XEXP (varop, 1))) >= 0)
8709             {
8710               varop
8711                 = simplify_gen_binary (ASHIFT, GET_MODE (varop),
8712                                        XEXP (varop, 0),
8713                                        GEN_INT (exact_log2 (
8714                                                 INTVAL (XEXP (varop, 1)))));
8715               continue;
8716             }
8717           break;
8718
8719         case UDIV:
8720           /* Similar, for when divides are cheaper.  */
8721           if (GET_CODE (XEXP (varop, 1)) == CONST_INT
8722               && exact_log2 (INTVAL (XEXP (varop, 1))) >= 0)
8723             {
8724               varop
8725                 = simplify_gen_binary (LSHIFTRT, GET_MODE (varop),
8726                                        XEXP (varop, 0),
8727                                        GEN_INT (exact_log2 (
8728                                                 INTVAL (XEXP (varop, 1)))));
8729               continue;
8730             }
8731           break;
8732
8733         case ASHIFTRT:
8734           /* If we are extracting just the sign bit of an arithmetic
8735              right shift, that shift is not needed.  However, the sign
8736              bit of a wider mode may be different from what would be
8737              interpreted as the sign bit in a narrower mode, so, if
8738              the result is narrower, don't discard the shift.  */
8739           if (code == LSHIFTRT
8740               && count == (GET_MODE_BITSIZE (result_mode) - 1)
8741               && (GET_MODE_BITSIZE (result_mode)
8742                   >= GET_MODE_BITSIZE (GET_MODE (varop))))
8743             {
8744               varop = XEXP (varop, 0);
8745               continue;
8746             }
8747
8748           /* ... fall through ...  */
8749
8750         case LSHIFTRT:
8751         case ASHIFT:
8752         case ROTATE:
8753           /* Here we have two nested shifts.  The result is usually the
8754              AND of a new shift with a mask.  We compute the result below.  */
8755           if (GET_CODE (XEXP (varop, 1)) == CONST_INT
8756               && INTVAL (XEXP (varop, 1)) >= 0
8757               && INTVAL (XEXP (varop, 1)) < GET_MODE_BITSIZE (GET_MODE (varop))
8758               && GET_MODE_BITSIZE (result_mode) <= HOST_BITS_PER_WIDE_INT
8759               && GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT
8760               && !VECTOR_MODE_P (result_mode))
8761             {
8762               enum rtx_code first_code = GET_CODE (varop);
8763               unsigned int first_count = INTVAL (XEXP (varop, 1));
8764               unsigned HOST_WIDE_INT mask;
8765               rtx mask_rtx;
8766
8767               /* We have one common special case.  We can't do any merging if
8768                  the inner code is an ASHIFTRT of a smaller mode.  However, if
8769                  we have (ashift:M1 (subreg:M1 (ashiftrt:M2 FOO C1) 0) C2)
8770                  with C2 == GET_MODE_BITSIZE (M1) - GET_MODE_BITSIZE (M2),
8771                  we can convert it to
8772                  (ashiftrt:M1 (ashift:M1 (and:M1 (subreg:M1 FOO 0 C2) C3) C1).
8773                  This simplifies certain SIGN_EXTEND operations.  */
8774               if (code == ASHIFT && first_code == ASHIFTRT
8775                   && count == (GET_MODE_BITSIZE (result_mode)
8776                                - GET_MODE_BITSIZE (GET_MODE (varop))))
8777                 {
8778                   /* C3 has the low-order C1 bits zero.  */
8779
8780                   mask = (GET_MODE_MASK (mode)
8781                           & ~(((HOST_WIDE_INT) 1 << first_count) - 1));
8782
8783                   varop = simplify_and_const_int (NULL_RTX, result_mode,
8784                                                   XEXP (varop, 0), mask);
8785                   varop = simplify_shift_const (NULL_RTX, ASHIFT, result_mode,
8786                                                 varop, count);
8787                   count = first_count;
8788                   code = ASHIFTRT;
8789                   continue;
8790                 }
8791
8792               /* If this was (ashiftrt (ashift foo C1) C2) and FOO has more
8793                  than C1 high-order bits equal to the sign bit, we can convert
8794                  this to either an ASHIFT or an ASHIFTRT depending on the
8795                  two counts.
8796
8797                  We cannot do this if VAROP's mode is not SHIFT_MODE.  */
8798
8799               if (code == ASHIFTRT && first_code == ASHIFT
8800                   && GET_MODE (varop) == shift_mode
8801                   && (num_sign_bit_copies (XEXP (varop, 0), shift_mode)
8802                       > first_count))
8803                 {
8804                   varop = XEXP (varop, 0);
8805                   count -= first_count;
8806                   if (count < 0)
8807                     {
8808                       count = -count;
8809                       code = ASHIFT;
8810                     }
8811
8812                   continue;
8813                 }
8814
8815               /* There are some cases we can't do.  If CODE is ASHIFTRT,
8816                  we can only do this if FIRST_CODE is also ASHIFTRT.
8817
8818                  We can't do the case when CODE is ROTATE and FIRST_CODE is
8819                  ASHIFTRT.
8820
8821                  If the mode of this shift is not the mode of the outer shift,
8822                  we can't do this if either shift is a right shift or ROTATE.
8823
8824                  Finally, we can't do any of these if the mode is too wide
8825                  unless the codes are the same.
8826
8827                  Handle the case where the shift codes are the same
8828                  first.  */
8829
8830               if (code == first_code)
8831                 {
8832                   if (GET_MODE (varop) != result_mode
8833                       && (code == ASHIFTRT || code == LSHIFTRT
8834                           || code == ROTATE))
8835                     break;
8836
8837                   count += first_count;
8838                   varop = XEXP (varop, 0);
8839                   continue;
8840                 }
8841
8842               if (code == ASHIFTRT
8843                   || (code == ROTATE && first_code == ASHIFTRT)
8844                   || GET_MODE_BITSIZE (mode) > HOST_BITS_PER_WIDE_INT
8845                   || (GET_MODE (varop) != result_mode
8846                       && (first_code == ASHIFTRT || first_code == LSHIFTRT
8847                           || first_code == ROTATE
8848                           || code == ROTATE)))
8849                 break;
8850
8851               /* To compute the mask to apply after the shift, shift the
8852                  nonzero bits of the inner shift the same way the
8853                  outer shift will.  */
8854
8855               mask_rtx = GEN_INT (nonzero_bits (varop, GET_MODE (varop)));
8856
8857               mask_rtx
8858                 = simplify_const_binary_operation (code, result_mode, mask_rtx,
8859                                                    GEN_INT (count));
8860
8861               /* Give up if we can't compute an outer operation to use.  */
8862               if (mask_rtx == 0
8863                   || GET_CODE (mask_rtx) != CONST_INT
8864                   || ! merge_outer_ops (&outer_op, &outer_const, AND,
8865                                         INTVAL (mask_rtx),
8866                                         result_mode, &complement_p))
8867                 break;
8868
8869               /* If the shifts are in the same direction, we add the
8870                  counts.  Otherwise, we subtract them.  */
8871               if ((code == ASHIFTRT || code == LSHIFTRT)
8872                   == (first_code == ASHIFTRT || first_code == LSHIFTRT))
8873                 count += first_count;
8874               else
8875                 count -= first_count;
8876
8877               /* If COUNT is positive, the new shift is usually CODE,
8878                  except for the two exceptions below, in which case it is
8879                  FIRST_CODE.  If the count is negative, FIRST_CODE should
8880                  always be used  */
8881               if (count > 0
8882                   && ((first_code == ROTATE && code == ASHIFT)
8883                       || (first_code == ASHIFTRT && code == LSHIFTRT)))
8884                 code = first_code;
8885               else if (count < 0)
8886                 code = first_code, count = -count;
8887
8888               varop = XEXP (varop, 0);
8889               continue;
8890             }
8891
8892           /* If we have (A << B << C) for any shift, we can convert this to
8893              (A << C << B).  This wins if A is a constant.  Only try this if
8894              B is not a constant.  */
8895
8896           else if (GET_CODE (varop) == code
8897                    && GET_CODE (XEXP (varop, 0)) == CONST_INT
8898                    && GET_CODE (XEXP (varop, 1)) != CONST_INT)
8899             {
8900               rtx new = simplify_const_binary_operation (code, mode,
8901                                                          XEXP (varop, 0),
8902                                                          GEN_INT (count));
8903               varop = gen_rtx_fmt_ee (code, mode, new, XEXP (varop, 1));
8904               count = 0;
8905               continue;
8906             }
8907           break;
8908
8909         case NOT:
8910           /* Make this fit the case below.  */
8911           varop = gen_rtx_XOR (mode, XEXP (varop, 0),
8912                                GEN_INT (GET_MODE_MASK (mode)));
8913           continue;
8914
8915         case IOR:
8916         case AND:
8917         case XOR:
8918           /* If we have (xshiftrt (ior (plus X (const_int -1)) X) C)
8919              with C the size of VAROP - 1 and the shift is logical if
8920              STORE_FLAG_VALUE is 1 and arithmetic if STORE_FLAG_VALUE is -1,
8921              we have an (le X 0) operation.   If we have an arithmetic shift
8922              and STORE_FLAG_VALUE is 1 or we have a logical shift with
8923              STORE_FLAG_VALUE of -1, we have a (neg (le X 0)) operation.  */
8924
8925           if (GET_CODE (varop) == IOR && GET_CODE (XEXP (varop, 0)) == PLUS
8926               && XEXP (XEXP (varop, 0), 1) == constm1_rtx
8927               && (STORE_FLAG_VALUE == 1 || STORE_FLAG_VALUE == -1)
8928               && (code == LSHIFTRT || code == ASHIFTRT)
8929               && count == (GET_MODE_BITSIZE (GET_MODE (varop)) - 1)
8930               && rtx_equal_p (XEXP (XEXP (varop, 0), 0), XEXP (varop, 1)))
8931             {
8932               count = 0;
8933               varop = gen_rtx_LE (GET_MODE (varop), XEXP (varop, 1),
8934                                   const0_rtx);
8935
8936               if (STORE_FLAG_VALUE == 1 ? code == ASHIFTRT : code == LSHIFTRT)
8937                 varop = gen_rtx_NEG (GET_MODE (varop), varop);
8938
8939               continue;
8940             }
8941
8942           /* If we have (shift (logical)), move the logical to the outside
8943              to allow it to possibly combine with another logical and the
8944              shift to combine with another shift.  This also canonicalizes to
8945              what a ZERO_EXTRACT looks like.  Also, some machines have
8946              (and (shift)) insns.  */
8947
8948           if (GET_CODE (XEXP (varop, 1)) == CONST_INT
8949               /* We can't do this if we have (ashiftrt (xor))  and the
8950                  constant has its sign bit set in shift_mode.  */
8951               && !(code == ASHIFTRT && GET_CODE (varop) == XOR
8952                    && 0 > trunc_int_for_mode (INTVAL (XEXP (varop, 1)),
8953                                               shift_mode))
8954               && (new = simplify_const_binary_operation (code, result_mode,
8955                                                          XEXP (varop, 1),
8956                                                          GEN_INT (count))) != 0
8957               && GET_CODE (new) == CONST_INT
8958               && merge_outer_ops (&outer_op, &outer_const, GET_CODE (varop),
8959                                   INTVAL (new), result_mode, &complement_p))
8960             {
8961               varop = XEXP (varop, 0);
8962               continue;
8963             }
8964
8965           /* If we can't do that, try to simplify the shift in each arm of the
8966              logical expression, make a new logical expression, and apply
8967              the inverse distributive law.  This also can't be done
8968              for some (ashiftrt (xor)).  */
8969           if (GET_CODE (XEXP (varop, 1)) == CONST_INT
8970              && !(code == ASHIFTRT && GET_CODE (varop) == XOR
8971                   && 0 > trunc_int_for_mode (INTVAL (XEXP (varop, 1)),
8972                                              shift_mode)))
8973             {
8974               rtx lhs = simplify_shift_const (NULL_RTX, code, shift_mode,
8975                                               XEXP (varop, 0), count);
8976               rtx rhs = simplify_shift_const (NULL_RTX, code, shift_mode,
8977                                               XEXP (varop, 1), count);
8978
8979               varop = simplify_gen_binary (GET_CODE (varop), shift_mode,
8980                                            lhs, rhs);
8981               varop = apply_distributive_law (varop);
8982
8983               count = 0;
8984               continue;
8985             }
8986           break;
8987
8988         case EQ:
8989           /* Convert (lshiftrt (eq FOO 0) C) to (xor FOO 1) if STORE_FLAG_VALUE
8990              says that the sign bit can be tested, FOO has mode MODE, C is
8991              GET_MODE_BITSIZE (MODE) - 1, and FOO has only its low-order bit
8992              that may be nonzero.  */
8993           if (code == LSHIFTRT
8994               && XEXP (varop, 1) == const0_rtx
8995               && GET_MODE (XEXP (varop, 0)) == result_mode
8996               && count == (GET_MODE_BITSIZE (result_mode) - 1)
8997               && GET_MODE_BITSIZE (result_mode) <= HOST_BITS_PER_WIDE_INT
8998               && STORE_FLAG_VALUE == -1
8999               && nonzero_bits (XEXP (varop, 0), result_mode) == 1
9000               && merge_outer_ops (&outer_op, &outer_const, XOR,
9001                                   (HOST_WIDE_INT) 1, result_mode,
9002                                   &complement_p))
9003             {
9004               varop = XEXP (varop, 0);
9005               count = 0;
9006               continue;
9007             }
9008           break;
9009
9010         case NEG:
9011           /* (lshiftrt (neg A) C) where A is either 0 or 1 and C is one less
9012              than the number of bits in the mode is equivalent to A.  */
9013           if (code == LSHIFTRT
9014               && count == (GET_MODE_BITSIZE (result_mode) - 1)
9015               && nonzero_bits (XEXP (varop, 0), result_mode) == 1)
9016             {
9017               varop = XEXP (varop, 0);
9018               count = 0;
9019               continue;
9020             }
9021
9022           /* NEG commutes with ASHIFT since it is multiplication.  Move the
9023              NEG outside to allow shifts to combine.  */
9024           if (code == ASHIFT
9025               && merge_outer_ops (&outer_op, &outer_const, NEG,
9026                                   (HOST_WIDE_INT) 0, result_mode,
9027                                   &complement_p))
9028             {
9029               varop = XEXP (varop, 0);
9030               continue;
9031             }
9032           break;
9033
9034         case PLUS:
9035           /* (lshiftrt (plus A -1) C) where A is either 0 or 1 and C
9036              is one less than the number of bits in the mode is
9037              equivalent to (xor A 1).  */
9038           if (code == LSHIFTRT
9039               && count == (GET_MODE_BITSIZE (result_mode) - 1)
9040               && XEXP (varop, 1) == constm1_rtx
9041               && nonzero_bits (XEXP (varop, 0), result_mode) == 1
9042               && merge_outer_ops (&outer_op, &outer_const, XOR,
9043                                   (HOST_WIDE_INT) 1, result_mode,
9044                                   &complement_p))
9045             {
9046               count = 0;
9047               varop = XEXP (varop, 0);
9048               continue;
9049             }
9050
9051           /* If we have (xshiftrt (plus FOO BAR) C), and the only bits
9052              that might be nonzero in BAR are those being shifted out and those
9053              bits are known zero in FOO, we can replace the PLUS with FOO.
9054              Similarly in the other operand order.  This code occurs when
9055              we are computing the size of a variable-size array.  */
9056
9057           if ((code == ASHIFTRT || code == LSHIFTRT)
9058               && count < HOST_BITS_PER_WIDE_INT
9059               && nonzero_bits (XEXP (varop, 1), result_mode) >> count == 0
9060               && (nonzero_bits (XEXP (varop, 1), result_mode)
9061                   & nonzero_bits (XEXP (varop, 0), result_mode)) == 0)
9062             {
9063               varop = XEXP (varop, 0);
9064               continue;
9065             }
9066           else if ((code == ASHIFTRT || code == LSHIFTRT)
9067                    && count < HOST_BITS_PER_WIDE_INT
9068                    && GET_MODE_BITSIZE (result_mode) <= HOST_BITS_PER_WIDE_INT
9069                    && 0 == (nonzero_bits (XEXP (varop, 0), result_mode)
9070                             >> count)
9071                    && 0 == (nonzero_bits (XEXP (varop, 0), result_mode)
9072                             & nonzero_bits (XEXP (varop, 1),
9073                                                  result_mode)))
9074             {
9075               varop = XEXP (varop, 1);
9076               continue;
9077             }
9078
9079           /* (ashift (plus foo C) N) is (plus (ashift foo N) C').  */
9080           if (code == ASHIFT
9081               && GET_CODE (XEXP (varop, 1)) == CONST_INT
9082               && (new = simplify_const_binary_operation (ASHIFT, result_mode,
9083                                                          XEXP (varop, 1),
9084                                                          GEN_INT (count))) != 0
9085               && GET_CODE (new) == CONST_INT
9086               && merge_outer_ops (&outer_op, &outer_const, PLUS,
9087                                   INTVAL (new), result_mode, &complement_p))
9088             {
9089               varop = XEXP (varop, 0);
9090               continue;
9091             }
9092
9093           /* Check for 'PLUS signbit', which is the canonical form of 'XOR
9094              signbit', and attempt to change the PLUS to an XOR and move it to
9095              the outer operation as is done above in the AND/IOR/XOR case
9096              leg for shift(logical). See details in logical handling above
9097              for reasoning in doing so.  */
9098           if (code == LSHIFTRT
9099               && GET_CODE (XEXP (varop, 1)) == CONST_INT
9100               && mode_signbit_p (result_mode, XEXP (varop, 1))
9101               && (new = simplify_const_binary_operation (code, result_mode,
9102                                                          XEXP (varop, 1),
9103                                                          GEN_INT (count))) != 0
9104               && GET_CODE (new) == CONST_INT
9105               && merge_outer_ops (&outer_op, &outer_const, XOR,
9106                                   INTVAL (new), result_mode, &complement_p))
9107             {
9108               varop = XEXP (varop, 0);
9109               continue;
9110             }
9111
9112           break;
9113
9114         case MINUS:
9115           /* If we have (xshiftrt (minus (ashiftrt X C)) X) C)
9116              with C the size of VAROP - 1 and the shift is logical if
9117              STORE_FLAG_VALUE is 1 and arithmetic if STORE_FLAG_VALUE is -1,
9118              we have a (gt X 0) operation.  If the shift is arithmetic with
9119              STORE_FLAG_VALUE of 1 or logical with STORE_FLAG_VALUE == -1,
9120              we have a (neg (gt X 0)) operation.  */
9121
9122           if ((STORE_FLAG_VALUE == 1 || STORE_FLAG_VALUE == -1)
9123               && GET_CODE (XEXP (varop, 0)) == ASHIFTRT
9124               && count == (GET_MODE_BITSIZE (GET_MODE (varop)) - 1)
9125               && (code == LSHIFTRT || code == ASHIFTRT)
9126               && GET_CODE (XEXP (XEXP (varop, 0), 1)) == CONST_INT
9127               && INTVAL (XEXP (XEXP (varop, 0), 1)) == count
9128               && rtx_equal_p (XEXP (XEXP (varop, 0), 0), XEXP (varop, 1)))
9129             {
9130               count = 0;
9131               varop = gen_rtx_GT (GET_MODE (varop), XEXP (varop, 1),
9132                                   const0_rtx);
9133
9134               if (STORE_FLAG_VALUE == 1 ? code == ASHIFTRT : code == LSHIFTRT)
9135                 varop = gen_rtx_NEG (GET_MODE (varop), varop);
9136
9137               continue;
9138             }
9139           break;
9140
9141         case TRUNCATE:
9142           /* Change (lshiftrt (truncate (lshiftrt))) to (truncate (lshiftrt))
9143              if the truncate does not affect the value.  */
9144           if (code == LSHIFTRT
9145               && GET_CODE (XEXP (varop, 0)) == LSHIFTRT
9146               && GET_CODE (XEXP (XEXP (varop, 0), 1)) == CONST_INT
9147               && (INTVAL (XEXP (XEXP (varop, 0), 1))
9148                   >= (GET_MODE_BITSIZE (GET_MODE (XEXP (varop, 0)))
9149                       - GET_MODE_BITSIZE (GET_MODE (varop)))))
9150             {
9151               rtx varop_inner = XEXP (varop, 0);
9152
9153               varop_inner
9154                 = gen_rtx_LSHIFTRT (GET_MODE (varop_inner),
9155                                     XEXP (varop_inner, 0),
9156                                     GEN_INT
9157                                     (count + INTVAL (XEXP (varop_inner, 1))));
9158               varop = gen_rtx_TRUNCATE (GET_MODE (varop), varop_inner);
9159               count = 0;
9160               continue;
9161             }
9162           break;
9163
9164         default:
9165           break;
9166         }
9167
9168       break;
9169     }
9170
9171   /* We need to determine what mode to do the shift in.  If the shift is
9172      a right shift or ROTATE, we must always do it in the mode it was
9173      originally done in.  Otherwise, we can do it in MODE, the widest mode
9174      encountered.  The code we care about is that of the shift that will
9175      actually be done, not the shift that was originally requested.  */
9176   shift_mode
9177     = (code == ASHIFTRT || code == LSHIFTRT || code == ROTATE
9178        ? result_mode : mode);
9179
9180   /* We have now finished analyzing the shift.  The result should be
9181      a shift of type CODE with SHIFT_MODE shifting VAROP COUNT places.  If
9182      OUTER_OP is non-UNKNOWN, it is an operation that needs to be applied
9183      to the result of the shift.  OUTER_CONST is the relevant constant,
9184      but we must turn off all bits turned off in the shift.  */
9185
9186   if (outer_op == UNKNOWN
9187       && orig_code == code && orig_count == count
9188       && varop == orig_varop
9189       && shift_mode == GET_MODE (varop))
9190     return NULL_RTX;
9191
9192   /* Make a SUBREG if necessary.  If we can't make it, fail.  */
9193   varop = gen_lowpart (shift_mode, varop);
9194   if (varop == NULL_RTX || GET_CODE (varop) == CLOBBER)
9195     return NULL_RTX;
9196
9197   /* If we have an outer operation and we just made a shift, it is
9198      possible that we could have simplified the shift were it not
9199      for the outer operation.  So try to do the simplification
9200      recursively.  */
9201
9202   if (outer_op != UNKNOWN)
9203     x = simplify_shift_const_1 (code, shift_mode, varop, count);
9204   else
9205     x = NULL_RTX;
9206
9207   if (x == NULL_RTX)
9208     x = simplify_gen_binary (code, shift_mode, varop, GEN_INT (count));
9209
9210   /* If we were doing an LSHIFTRT in a wider mode than it was originally,
9211      turn off all the bits that the shift would have turned off.  */
9212   if (orig_code == LSHIFTRT && result_mode != shift_mode)
9213     x = simplify_and_const_int (NULL_RTX, shift_mode, x,
9214                                 GET_MODE_MASK (result_mode) >> orig_count);
9215
9216   /* Do the remainder of the processing in RESULT_MODE.  */
9217   x = gen_lowpart_or_truncate (result_mode, x);
9218
9219   /* If COMPLEMENT_P is set, we have to complement X before doing the outer
9220      operation.  */
9221   if (complement_p)
9222     x = simplify_gen_unary (NOT, result_mode, x, result_mode);
9223
9224   if (outer_op != UNKNOWN)
9225     {
9226       if (GET_MODE_BITSIZE (result_mode) < HOST_BITS_PER_WIDE_INT)
9227         outer_const = trunc_int_for_mode (outer_const, result_mode);
9228
9229       if (outer_op == AND)
9230         x = simplify_and_const_int (NULL_RTX, result_mode, x, outer_const);
9231       else if (outer_op == SET)
9232         {
9233           /* This means that we have determined that the result is
9234              equivalent to a constant.  This should be rare.  */
9235           if (!side_effects_p (x))
9236             x = GEN_INT (outer_const);
9237         }
9238       else if (GET_RTX_CLASS (outer_op) == RTX_UNARY)
9239         x = simplify_gen_unary (outer_op, result_mode, x, result_mode);
9240       else
9241         x = simplify_gen_binary (outer_op, result_mode, x,
9242                                  GEN_INT (outer_const));
9243     }
9244
9245   return x;
9246 }
9247
9248 /* Simplify a shift of VAROP by COUNT bits.  CODE says what kind of shift.
9249    The result of the shift is RESULT_MODE.  If we cannot simplify it,
9250    return X or, if it is NULL, synthesize the expression with
9251    simplify_gen_binary.  Otherwise, return a simplified value.
9252
9253    The shift is normally computed in the widest mode we find in VAROP, as
9254    long as it isn't a different number of words than RESULT_MODE.  Exceptions
9255    are ASHIFTRT and ROTATE, which are always done in their original mode.  */
9256
9257 static rtx
9258 simplify_shift_const (rtx x, enum rtx_code code, enum machine_mode result_mode,
9259                       rtx varop, int count)
9260 {
9261   rtx tem = simplify_shift_const_1 (code, result_mode, varop, count);
9262   if (tem)
9263     return tem;
9264
9265   if (!x)
9266     x = simplify_gen_binary (code, GET_MODE (varop), varop, GEN_INT (count));
9267   if (GET_MODE (x) != result_mode)
9268     x = gen_lowpart (result_mode, x);
9269   return x;
9270 }
9271
9272 \f
9273 /* Like recog, but we receive the address of a pointer to a new pattern.
9274    We try to match the rtx that the pointer points to.
9275    If that fails, we may try to modify or replace the pattern,
9276    storing the replacement into the same pointer object.
9277
9278    Modifications include deletion or addition of CLOBBERs.
9279
9280    PNOTES is a pointer to a location where any REG_UNUSED notes added for
9281    the CLOBBERs are placed.
9282
9283    The value is the final insn code from the pattern ultimately matched,
9284    or -1.  */
9285
9286 static int
9287 recog_for_combine (rtx *pnewpat, rtx insn, rtx *pnotes)
9288 {
9289   rtx pat = *pnewpat;
9290   int insn_code_number;
9291   int num_clobbers_to_add = 0;
9292   int i;
9293   rtx notes = 0;
9294   rtx old_notes, old_pat;
9295
9296   /* If PAT is a PARALLEL, check to see if it contains the CLOBBER
9297      we use to indicate that something didn't match.  If we find such a
9298      thing, force rejection.  */
9299   if (GET_CODE (pat) == PARALLEL)
9300     for (i = XVECLEN (pat, 0) - 1; i >= 0; i--)
9301       if (GET_CODE (XVECEXP (pat, 0, i)) == CLOBBER
9302           && XEXP (XVECEXP (pat, 0, i), 0) == const0_rtx)
9303         return -1;
9304
9305   old_pat = PATTERN (insn);
9306   old_notes = REG_NOTES (insn);
9307   PATTERN (insn) = pat;
9308   REG_NOTES (insn) = 0;
9309
9310   insn_code_number = recog (pat, insn, &num_clobbers_to_add);
9311
9312   /* If it isn't, there is the possibility that we previously had an insn
9313      that clobbered some register as a side effect, but the combined
9314      insn doesn't need to do that.  So try once more without the clobbers
9315      unless this represents an ASM insn.  */
9316
9317   if (insn_code_number < 0 && ! check_asm_operands (pat)
9318       && GET_CODE (pat) == PARALLEL)
9319     {
9320       int pos;
9321
9322       for (pos = 0, i = 0; i < XVECLEN (pat, 0); i++)
9323         if (GET_CODE (XVECEXP (pat, 0, i)) != CLOBBER)
9324           {
9325             if (i != pos)
9326               SUBST (XVECEXP (pat, 0, pos), XVECEXP (pat, 0, i));
9327             pos++;
9328           }
9329
9330       SUBST_INT (XVECLEN (pat, 0), pos);
9331
9332       if (pos == 1)
9333         pat = XVECEXP (pat, 0, 0);
9334
9335       PATTERN (insn) = pat;
9336       insn_code_number = recog (pat, insn, &num_clobbers_to_add);
9337     }
9338   PATTERN (insn) = old_pat;
9339   REG_NOTES (insn) = old_notes;
9340
9341   /* Recognize all noop sets, these will be killed by followup pass.  */
9342   if (insn_code_number < 0 && GET_CODE (pat) == SET && set_noop_p (pat))
9343     insn_code_number = NOOP_MOVE_INSN_CODE, num_clobbers_to_add = 0;
9344
9345   /* If we had any clobbers to add, make a new pattern than contains
9346      them.  Then check to make sure that all of them are dead.  */
9347   if (num_clobbers_to_add)
9348     {
9349       rtx newpat = gen_rtx_PARALLEL (VOIDmode,
9350                                      rtvec_alloc (GET_CODE (pat) == PARALLEL
9351                                                   ? (XVECLEN (pat, 0)
9352                                                      + num_clobbers_to_add)
9353                                                   : num_clobbers_to_add + 1));
9354
9355       if (GET_CODE (pat) == PARALLEL)
9356         for (i = 0; i < XVECLEN (pat, 0); i++)
9357           XVECEXP (newpat, 0, i) = XVECEXP (pat, 0, i);
9358       else
9359         XVECEXP (newpat, 0, 0) = pat;
9360
9361       add_clobbers (newpat, insn_code_number);
9362
9363       for (i = XVECLEN (newpat, 0) - num_clobbers_to_add;
9364            i < XVECLEN (newpat, 0); i++)
9365         {
9366           if (REG_P (XEXP (XVECEXP (newpat, 0, i), 0))
9367               && ! reg_dead_at_p (XEXP (XVECEXP (newpat, 0, i), 0), insn))
9368             return -1;
9369           notes = gen_rtx_EXPR_LIST (REG_UNUSED,
9370                                      XEXP (XVECEXP (newpat, 0, i), 0), notes);
9371         }
9372       pat = newpat;
9373     }
9374
9375   *pnewpat = pat;
9376   *pnotes = notes;
9377
9378   return insn_code_number;
9379 }
9380 \f
9381 /* Like gen_lowpart_general but for use by combine.  In combine it
9382    is not possible to create any new pseudoregs.  However, it is
9383    safe to create invalid memory addresses, because combine will
9384    try to recognize them and all they will do is make the combine
9385    attempt fail.
9386
9387    If for some reason this cannot do its job, an rtx
9388    (clobber (const_int 0)) is returned.
9389    An insn containing that will not be recognized.  */
9390
9391 static rtx
9392 gen_lowpart_for_combine (enum machine_mode omode, rtx x)
9393 {
9394   enum machine_mode imode = GET_MODE (x);
9395   unsigned int osize = GET_MODE_SIZE (omode);
9396   unsigned int isize = GET_MODE_SIZE (imode);
9397   rtx result;
9398
9399   if (omode == imode)
9400     return x;
9401
9402   /* Return identity if this is a CONST or symbolic reference.  */
9403   if (omode == Pmode
9404       && (GET_CODE (x) == CONST
9405           || GET_CODE (x) == SYMBOL_REF
9406           || GET_CODE (x) == LABEL_REF))
9407     return x;
9408
9409   /* We can only support MODE being wider than a word if X is a
9410      constant integer or has a mode the same size.  */
9411   if (GET_MODE_SIZE (omode) > UNITS_PER_WORD
9412       && ! ((imode == VOIDmode
9413              && (GET_CODE (x) == CONST_INT
9414                  || GET_CODE (x) == CONST_DOUBLE))
9415             || isize == osize))
9416     goto fail;
9417
9418   /* X might be a paradoxical (subreg (mem)).  In that case, gen_lowpart
9419      won't know what to do.  So we will strip off the SUBREG here and
9420      process normally.  */
9421   if (GET_CODE (x) == SUBREG && MEM_P (SUBREG_REG (x)))
9422     {
9423       x = SUBREG_REG (x);
9424
9425       /* For use in case we fall down into the address adjustments
9426          further below, we need to adjust the known mode and size of
9427          x; imode and isize, since we just adjusted x.  */
9428       imode = GET_MODE (x);
9429
9430       if (imode == omode)
9431         return x;
9432
9433       isize = GET_MODE_SIZE (imode);
9434     }
9435
9436   result = gen_lowpart_common (omode, x);
9437
9438 #ifdef CANNOT_CHANGE_MODE_CLASS
9439   if (result != 0 && GET_CODE (result) == SUBREG)
9440     record_subregs_of_mode (result);
9441 #endif
9442
9443   if (result)
9444     return result;
9445
9446   if (MEM_P (x))
9447     {
9448       int offset = 0;
9449
9450       /* Refuse to work on a volatile memory ref or one with a mode-dependent
9451          address.  */
9452       if (MEM_VOLATILE_P (x) || mode_dependent_address_p (XEXP (x, 0)))
9453         goto fail;
9454
9455       /* If we want to refer to something bigger than the original memref,
9456          generate a paradoxical subreg instead.  That will force a reload
9457          of the original memref X.  */
9458       if (isize < osize)
9459         return gen_rtx_SUBREG (omode, x, 0);
9460
9461       if (WORDS_BIG_ENDIAN)
9462         offset = MAX (isize, UNITS_PER_WORD) - MAX (osize, UNITS_PER_WORD);
9463
9464       /* Adjust the address so that the address-after-the-data is
9465          unchanged.  */
9466       if (BYTES_BIG_ENDIAN)
9467         offset -= MIN (UNITS_PER_WORD, osize) - MIN (UNITS_PER_WORD, isize);
9468
9469       return adjust_address_nv (x, omode, offset);
9470     }
9471
9472   /* If X is a comparison operator, rewrite it in a new mode.  This
9473      probably won't match, but may allow further simplifications.  */
9474   else if (COMPARISON_P (x))
9475     return gen_rtx_fmt_ee (GET_CODE (x), omode, XEXP (x, 0), XEXP (x, 1));
9476
9477   /* If we couldn't simplify X any other way, just enclose it in a
9478      SUBREG.  Normally, this SUBREG won't match, but some patterns may
9479      include an explicit SUBREG or we may simplify it further in combine.  */
9480   else
9481     {
9482       int offset = 0;
9483       rtx res;
9484
9485       offset = subreg_lowpart_offset (omode, imode);
9486       if (imode == VOIDmode)
9487         {
9488           imode = int_mode_for_mode (omode);
9489           x = gen_lowpart_common (imode, x);
9490           if (x == NULL)
9491             goto fail;
9492         }
9493       res = simplify_gen_subreg (omode, x, imode, offset);
9494       if (res)
9495         return res;
9496     }
9497
9498  fail:
9499   return gen_rtx_CLOBBER (imode, const0_rtx);
9500 }
9501 \f
9502 /* Simplify a comparison between *POP0 and *POP1 where CODE is the
9503    comparison code that will be tested.
9504
9505    The result is a possibly different comparison code to use.  *POP0 and
9506    *POP1 may be updated.
9507
9508    It is possible that we might detect that a comparison is either always
9509    true or always false.  However, we do not perform general constant
9510    folding in combine, so this knowledge isn't useful.  Such tautologies
9511    should have been detected earlier.  Hence we ignore all such cases.  */
9512
9513 static enum rtx_code
9514 simplify_comparison (enum rtx_code code, rtx *pop0, rtx *pop1)
9515 {
9516   rtx op0 = *pop0;
9517   rtx op1 = *pop1;
9518   rtx tem, tem1;
9519   int i;
9520   enum machine_mode mode, tmode;
9521
9522   /* Try a few ways of applying the same transformation to both operands.  */
9523   while (1)
9524     {
9525 #ifndef WORD_REGISTER_OPERATIONS
9526       /* The test below this one won't handle SIGN_EXTENDs on these machines,
9527          so check specially.  */
9528       if (code != GTU && code != GEU && code != LTU && code != LEU
9529           && GET_CODE (op0) == ASHIFTRT && GET_CODE (op1) == ASHIFTRT
9530           && GET_CODE (XEXP (op0, 0)) == ASHIFT
9531           && GET_CODE (XEXP (op1, 0)) == ASHIFT
9532           && GET_CODE (XEXP (XEXP (op0, 0), 0)) == SUBREG
9533           && GET_CODE (XEXP (XEXP (op1, 0), 0)) == SUBREG
9534           && (GET_MODE (SUBREG_REG (XEXP (XEXP (op0, 0), 0)))
9535               == GET_MODE (SUBREG_REG (XEXP (XEXP (op1, 0), 0))))
9536           && GET_CODE (XEXP (op0, 1)) == CONST_INT
9537           && XEXP (op0, 1) == XEXP (op1, 1)
9538           && XEXP (op0, 1) == XEXP (XEXP (op0, 0), 1)
9539           && XEXP (op0, 1) == XEXP (XEXP (op1, 0), 1)
9540           && (INTVAL (XEXP (op0, 1))
9541               == (GET_MODE_BITSIZE (GET_MODE (op0))
9542                   - (GET_MODE_BITSIZE
9543                      (GET_MODE (SUBREG_REG (XEXP (XEXP (op0, 0), 0))))))))
9544         {
9545           op0 = SUBREG_REG (XEXP (XEXP (op0, 0), 0));
9546           op1 = SUBREG_REG (XEXP (XEXP (op1, 0), 0));
9547         }
9548 #endif
9549
9550       /* If both operands are the same constant shift, see if we can ignore the
9551          shift.  We can if the shift is a rotate or if the bits shifted out of
9552          this shift are known to be zero for both inputs and if the type of
9553          comparison is compatible with the shift.  */
9554       if (GET_CODE (op0) == GET_CODE (op1)
9555           && GET_MODE_BITSIZE (GET_MODE (op0)) <= HOST_BITS_PER_WIDE_INT
9556           && ((GET_CODE (op0) == ROTATE && (code == NE || code == EQ))
9557               || ((GET_CODE (op0) == LSHIFTRT || GET_CODE (op0) == ASHIFT)
9558                   && (code != GT && code != LT && code != GE && code != LE))
9559               || (GET_CODE (op0) == ASHIFTRT
9560                   && (code != GTU && code != LTU
9561                       && code != GEU && code != LEU)))
9562           && GET_CODE (XEXP (op0, 1)) == CONST_INT
9563           && INTVAL (XEXP (op0, 1)) >= 0
9564           && INTVAL (XEXP (op0, 1)) < HOST_BITS_PER_WIDE_INT
9565           && XEXP (op0, 1) == XEXP (op1, 1))
9566         {
9567           enum machine_mode mode = GET_MODE (op0);
9568           unsigned HOST_WIDE_INT mask = GET_MODE_MASK (mode);
9569           int shift_count = INTVAL (XEXP (op0, 1));
9570
9571           if (GET_CODE (op0) == LSHIFTRT || GET_CODE (op0) == ASHIFTRT)
9572             mask &= (mask >> shift_count) << shift_count;
9573           else if (GET_CODE (op0) == ASHIFT)
9574             mask = (mask & (mask << shift_count)) >> shift_count;
9575
9576           if ((nonzero_bits (XEXP (op0, 0), mode) & ~mask) == 0
9577               && (nonzero_bits (XEXP (op1, 0), mode) & ~mask) == 0)
9578             op0 = XEXP (op0, 0), op1 = XEXP (op1, 0);
9579           else
9580             break;
9581         }
9582
9583       /* If both operands are AND's of a paradoxical SUBREG by constant, the
9584          SUBREGs are of the same mode, and, in both cases, the AND would
9585          be redundant if the comparison was done in the narrower mode,
9586          do the comparison in the narrower mode (e.g., we are AND'ing with 1
9587          and the operand's possibly nonzero bits are 0xffffff01; in that case
9588          if we only care about QImode, we don't need the AND).  This case
9589          occurs if the output mode of an scc insn is not SImode and
9590          STORE_FLAG_VALUE == 1 (e.g., the 386).
9591
9592          Similarly, check for a case where the AND's are ZERO_EXTEND
9593          operations from some narrower mode even though a SUBREG is not
9594          present.  */
9595
9596       else if (GET_CODE (op0) == AND && GET_CODE (op1) == AND
9597                && GET_CODE (XEXP (op0, 1)) == CONST_INT
9598                && GET_CODE (XEXP (op1, 1)) == CONST_INT)
9599         {
9600           rtx inner_op0 = XEXP (op0, 0);
9601           rtx inner_op1 = XEXP (op1, 0);
9602           HOST_WIDE_INT c0 = INTVAL (XEXP (op0, 1));
9603           HOST_WIDE_INT c1 = INTVAL (XEXP (op1, 1));
9604           int changed = 0;
9605
9606           if (GET_CODE (inner_op0) == SUBREG && GET_CODE (inner_op1) == SUBREG
9607               && (GET_MODE_SIZE (GET_MODE (inner_op0))
9608                   > GET_MODE_SIZE (GET_MODE (SUBREG_REG (inner_op0))))
9609               && (GET_MODE (SUBREG_REG (inner_op0))
9610                   == GET_MODE (SUBREG_REG (inner_op1)))
9611               && (GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (inner_op0)))
9612                   <= HOST_BITS_PER_WIDE_INT)
9613               && (0 == ((~c0) & nonzero_bits (SUBREG_REG (inner_op0),
9614                                              GET_MODE (SUBREG_REG (inner_op0)))))
9615               && (0 == ((~c1) & nonzero_bits (SUBREG_REG (inner_op1),
9616                                              GET_MODE (SUBREG_REG (inner_op1))))))
9617             {
9618               op0 = SUBREG_REG (inner_op0);
9619               op1 = SUBREG_REG (inner_op1);
9620
9621               /* The resulting comparison is always unsigned since we masked
9622                  off the original sign bit.  */
9623               code = unsigned_condition (code);
9624
9625               changed = 1;
9626             }
9627
9628           else if (c0 == c1)
9629             for (tmode = GET_CLASS_NARROWEST_MODE
9630                  (GET_MODE_CLASS (GET_MODE (op0)));
9631                  tmode != GET_MODE (op0); tmode = GET_MODE_WIDER_MODE (tmode))
9632               if ((unsigned HOST_WIDE_INT) c0 == GET_MODE_MASK (tmode))
9633                 {
9634                   op0 = gen_lowpart (tmode, inner_op0);
9635                   op1 = gen_lowpart (tmode, inner_op1);
9636                   code = unsigned_condition (code);
9637                   changed = 1;
9638                   break;
9639                 }
9640
9641           if (! changed)
9642             break;
9643         }
9644
9645       /* If both operands are NOT, we can strip off the outer operation
9646          and adjust the comparison code for swapped operands; similarly for
9647          NEG, except that this must be an equality comparison.  */
9648       else if ((GET_CODE (op0) == NOT && GET_CODE (op1) == NOT)
9649                || (GET_CODE (op0) == NEG && GET_CODE (op1) == NEG
9650                    && (code == EQ || code == NE)))
9651         op0 = XEXP (op0, 0), op1 = XEXP (op1, 0), code = swap_condition (code);
9652
9653       else
9654         break;
9655     }
9656
9657   /* If the first operand is a constant, swap the operands and adjust the
9658      comparison code appropriately, but don't do this if the second operand
9659      is already a constant integer.  */
9660   if (swap_commutative_operands_p (op0, op1))
9661     {
9662       tem = op0, op0 = op1, op1 = tem;
9663       code = swap_condition (code);
9664     }
9665
9666   /* We now enter a loop during which we will try to simplify the comparison.
9667      For the most part, we only are concerned with comparisons with zero,
9668      but some things may really be comparisons with zero but not start
9669      out looking that way.  */
9670
9671   while (GET_CODE (op1) == CONST_INT)
9672     {
9673       enum machine_mode mode = GET_MODE (op0);
9674       unsigned int mode_width = GET_MODE_BITSIZE (mode);
9675       unsigned HOST_WIDE_INT mask = GET_MODE_MASK (mode);
9676       int equality_comparison_p;
9677       int sign_bit_comparison_p;
9678       int unsigned_comparison_p;
9679       HOST_WIDE_INT const_op;
9680
9681       /* We only want to handle integral modes.  This catches VOIDmode,
9682          CCmode, and the floating-point modes.  An exception is that we
9683          can handle VOIDmode if OP0 is a COMPARE or a comparison
9684          operation.  */
9685
9686       if (GET_MODE_CLASS (mode) != MODE_INT
9687           && ! (mode == VOIDmode
9688                 && (GET_CODE (op0) == COMPARE || COMPARISON_P (op0))))
9689         break;
9690
9691       /* Get the constant we are comparing against and turn off all bits
9692          not on in our mode.  */
9693       const_op = INTVAL (op1);
9694       if (mode != VOIDmode)
9695         const_op = trunc_int_for_mode (const_op, mode);
9696       op1 = GEN_INT (const_op);
9697
9698       /* If we are comparing against a constant power of two and the value
9699          being compared can only have that single bit nonzero (e.g., it was
9700          `and'ed with that bit), we can replace this with a comparison
9701          with zero.  */
9702       if (const_op
9703           && (code == EQ || code == NE || code == GE || code == GEU
9704               || code == LT || code == LTU)
9705           && mode_width <= HOST_BITS_PER_WIDE_INT
9706           && exact_log2 (const_op) >= 0
9707           && nonzero_bits (op0, mode) == (unsigned HOST_WIDE_INT) const_op)
9708         {
9709           code = (code == EQ || code == GE || code == GEU ? NE : EQ);
9710           op1 = const0_rtx, const_op = 0;
9711         }
9712
9713       /* Similarly, if we are comparing a value known to be either -1 or
9714          0 with -1, change it to the opposite comparison against zero.  */
9715
9716       if (const_op == -1
9717           && (code == EQ || code == NE || code == GT || code == LE
9718               || code == GEU || code == LTU)
9719           && num_sign_bit_copies (op0, mode) == mode_width)
9720         {
9721           code = (code == EQ || code == LE || code == GEU ? NE : EQ);
9722           op1 = const0_rtx, const_op = 0;
9723         }
9724
9725       /* Do some canonicalizations based on the comparison code.  We prefer
9726          comparisons against zero and then prefer equality comparisons.
9727          If we can reduce the size of a constant, we will do that too.  */
9728
9729       switch (code)
9730         {
9731         case LT:
9732           /* < C is equivalent to <= (C - 1) */
9733           if (const_op > 0)
9734             {
9735               const_op -= 1;
9736               op1 = GEN_INT (const_op);
9737               code = LE;
9738               /* ... fall through to LE case below.  */
9739             }
9740           else
9741             break;
9742
9743         case LE:
9744           /* <= C is equivalent to < (C + 1); we do this for C < 0  */
9745           if (const_op < 0)
9746             {
9747               const_op += 1;
9748               op1 = GEN_INT (const_op);
9749               code = LT;
9750             }
9751
9752           /* If we are doing a <= 0 comparison on a value known to have
9753              a zero sign bit, we can replace this with == 0.  */
9754           else if (const_op == 0
9755                    && mode_width <= HOST_BITS_PER_WIDE_INT
9756                    && (nonzero_bits (op0, mode)
9757                        & ((HOST_WIDE_INT) 1 << (mode_width - 1))) == 0)
9758             code = EQ;
9759           break;
9760
9761         case GE:
9762           /* >= C is equivalent to > (C - 1).  */
9763           if (const_op > 0)
9764             {
9765               const_op -= 1;
9766               op1 = GEN_INT (const_op);
9767               code = GT;
9768               /* ... fall through to GT below.  */
9769             }
9770           else
9771             break;
9772
9773         case GT:
9774           /* > C is equivalent to >= (C + 1); we do this for C < 0.  */
9775           if (const_op < 0)
9776             {
9777               const_op += 1;
9778               op1 = GEN_INT (const_op);
9779               code = GE;
9780             }
9781
9782           /* If we are doing a > 0 comparison on a value known to have
9783              a zero sign bit, we can replace this with != 0.  */
9784           else if (const_op == 0
9785                    && mode_width <= HOST_BITS_PER_WIDE_INT
9786                    && (nonzero_bits (op0, mode)
9787                        & ((HOST_WIDE_INT) 1 << (mode_width - 1))) == 0)
9788             code = NE;
9789           break;
9790
9791         case LTU:
9792           /* < C is equivalent to <= (C - 1).  */
9793           if (const_op > 0)
9794             {
9795               const_op -= 1;
9796               op1 = GEN_INT (const_op);
9797               code = LEU;
9798               /* ... fall through ...  */
9799             }
9800
9801           /* (unsigned) < 0x80000000 is equivalent to >= 0.  */
9802           else if ((mode_width <= HOST_BITS_PER_WIDE_INT)
9803                    && (const_op == (HOST_WIDE_INT) 1 << (mode_width - 1)))
9804             {
9805               const_op = 0, op1 = const0_rtx;
9806               code = GE;
9807               break;
9808             }
9809           else
9810             break;
9811
9812         case LEU:
9813           /* unsigned <= 0 is equivalent to == 0 */
9814           if (const_op == 0)
9815             code = EQ;
9816
9817           /* (unsigned) <= 0x7fffffff is equivalent to >= 0.  */
9818           else if ((mode_width <= HOST_BITS_PER_WIDE_INT)
9819                    && (const_op == ((HOST_WIDE_INT) 1 << (mode_width - 1)) - 1))
9820             {
9821               const_op = 0, op1 = const0_rtx;
9822               code = GE;
9823             }
9824           break;
9825
9826         case GEU:
9827           /* >= C is equivalent to > (C - 1).  */
9828           if (const_op > 1)
9829             {
9830               const_op -= 1;
9831               op1 = GEN_INT (const_op);
9832               code = GTU;
9833               /* ... fall through ...  */
9834             }
9835
9836           /* (unsigned) >= 0x80000000 is equivalent to < 0.  */
9837           else if ((mode_width <= HOST_BITS_PER_WIDE_INT)
9838                    && (const_op == (HOST_WIDE_INT) 1 << (mode_width - 1)))
9839             {
9840               const_op = 0, op1 = const0_rtx;
9841               code = LT;
9842               break;
9843             }
9844           else
9845             break;
9846
9847         case GTU:
9848           /* unsigned > 0 is equivalent to != 0 */
9849           if (const_op == 0)
9850             code = NE;
9851
9852           /* (unsigned) > 0x7fffffff is equivalent to < 0.  */
9853           else if ((mode_width <= HOST_BITS_PER_WIDE_INT)
9854                    && (const_op == ((HOST_WIDE_INT) 1 << (mode_width - 1)) - 1))
9855             {
9856               const_op = 0, op1 = const0_rtx;
9857               code = LT;
9858             }
9859           break;
9860
9861         default:
9862           break;
9863         }
9864
9865       /* Compute some predicates to simplify code below.  */
9866
9867       equality_comparison_p = (code == EQ || code == NE);
9868       sign_bit_comparison_p = ((code == LT || code == GE) && const_op == 0);
9869       unsigned_comparison_p = (code == LTU || code == LEU || code == GTU
9870                                || code == GEU);
9871
9872       /* If this is a sign bit comparison and we can do arithmetic in
9873          MODE, say that we will only be needing the sign bit of OP0.  */
9874       if (sign_bit_comparison_p
9875           && GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT)
9876         op0 = force_to_mode (op0, mode,
9877                              ((HOST_WIDE_INT) 1
9878                               << (GET_MODE_BITSIZE (mode) - 1)),
9879                              0);
9880
9881       /* Now try cases based on the opcode of OP0.  If none of the cases
9882          does a "continue", we exit this loop immediately after the
9883          switch.  */
9884
9885       switch (GET_CODE (op0))
9886         {
9887         case ZERO_EXTRACT:
9888           /* If we are extracting a single bit from a variable position in
9889              a constant that has only a single bit set and are comparing it
9890              with zero, we can convert this into an equality comparison
9891              between the position and the location of the single bit.  */
9892           /* Except we can't if SHIFT_COUNT_TRUNCATED is set, since we might
9893              have already reduced the shift count modulo the word size.  */
9894           if (!SHIFT_COUNT_TRUNCATED
9895               && GET_CODE (XEXP (op0, 0)) == CONST_INT
9896               && XEXP (op0, 1) == const1_rtx
9897               && equality_comparison_p && const_op == 0
9898               && (i = exact_log2 (INTVAL (XEXP (op0, 0)))) >= 0)
9899             {
9900               if (BITS_BIG_ENDIAN)
9901                 {
9902                   enum machine_mode new_mode
9903                     = mode_for_extraction (EP_extzv, 1);
9904                   if (new_mode == MAX_MACHINE_MODE)
9905                     i = BITS_PER_WORD - 1 - i;
9906                   else
9907                     {
9908                       mode = new_mode;
9909                       i = (GET_MODE_BITSIZE (mode) - 1 - i);
9910                     }
9911                 }
9912
9913               op0 = XEXP (op0, 2);
9914               op1 = GEN_INT (i);
9915               const_op = i;
9916
9917               /* Result is nonzero iff shift count is equal to I.  */
9918               code = reverse_condition (code);
9919               continue;
9920             }
9921
9922           /* ... fall through ...  */
9923
9924         case SIGN_EXTRACT:
9925           tem = expand_compound_operation (op0);
9926           if (tem != op0)
9927             {
9928               op0 = tem;
9929               continue;
9930             }
9931           break;
9932
9933         case NOT:
9934           /* If testing for equality, we can take the NOT of the constant.  */
9935           if (equality_comparison_p
9936               && (tem = simplify_unary_operation (NOT, mode, op1, mode)) != 0)
9937             {
9938               op0 = XEXP (op0, 0);
9939               op1 = tem;
9940               continue;
9941             }
9942
9943           /* If just looking at the sign bit, reverse the sense of the
9944              comparison.  */
9945           if (sign_bit_comparison_p)
9946             {
9947               op0 = XEXP (op0, 0);
9948               code = (code == GE ? LT : GE);
9949               continue;
9950             }
9951           break;
9952
9953         case NEG:
9954           /* If testing for equality, we can take the NEG of the constant.  */
9955           if (equality_comparison_p
9956               && (tem = simplify_unary_operation (NEG, mode, op1, mode)) != 0)
9957             {
9958               op0 = XEXP (op0, 0);
9959               op1 = tem;
9960               continue;
9961             }
9962
9963           /* The remaining cases only apply to comparisons with zero.  */
9964           if (const_op != 0)
9965             break;
9966
9967           /* When X is ABS or is known positive,
9968              (neg X) is < 0 if and only if X != 0.  */
9969
9970           if (sign_bit_comparison_p
9971               && (GET_CODE (XEXP (op0, 0)) == ABS
9972                   || (mode_width <= HOST_BITS_PER_WIDE_INT
9973                       && (nonzero_bits (XEXP (op0, 0), mode)
9974                           & ((HOST_WIDE_INT) 1 << (mode_width - 1))) == 0)))
9975             {
9976               op0 = XEXP (op0, 0);
9977               code = (code == LT ? NE : EQ);
9978               continue;
9979             }
9980
9981           /* If we have NEG of something whose two high-order bits are the
9982              same, we know that "(-a) < 0" is equivalent to "a > 0".  */
9983           if (num_sign_bit_copies (op0, mode) >= 2)
9984             {
9985               op0 = XEXP (op0, 0);
9986               code = swap_condition (code);
9987               continue;
9988             }
9989           break;
9990
9991         case ROTATE:
9992           /* If we are testing equality and our count is a constant, we
9993              can perform the inverse operation on our RHS.  */
9994           if (equality_comparison_p && GET_CODE (XEXP (op0, 1)) == CONST_INT
9995               && (tem = simplify_binary_operation (ROTATERT, mode,
9996                                                    op1, XEXP (op0, 1))) != 0)
9997             {
9998               op0 = XEXP (op0, 0);
9999               op1 = tem;
10000               continue;
10001             }
10002
10003           /* If we are doing a < 0 or >= 0 comparison, it means we are testing
10004              a particular bit.  Convert it to an AND of a constant of that
10005              bit.  This will be converted into a ZERO_EXTRACT.  */
10006           if (const_op == 0 && sign_bit_comparison_p
10007               && GET_CODE (XEXP (op0, 1)) == CONST_INT
10008               && mode_width <= HOST_BITS_PER_WIDE_INT)
10009             {
10010               op0 = simplify_and_const_int (NULL_RTX, mode, XEXP (op0, 0),
10011                                             ((HOST_WIDE_INT) 1
10012                                              << (mode_width - 1
10013                                                  - INTVAL (XEXP (op0, 1)))));
10014               code = (code == LT ? NE : EQ);
10015               continue;
10016             }
10017
10018           /* Fall through.  */
10019
10020         case ABS:
10021           /* ABS is ignorable inside an equality comparison with zero.  */
10022           if (const_op == 0 && equality_comparison_p)
10023             {
10024               op0 = XEXP (op0, 0);
10025               continue;
10026             }
10027           break;
10028
10029         case SIGN_EXTEND:
10030           /* Can simplify (compare (zero/sign_extend FOO) CONST) to
10031              (compare FOO CONST) if CONST fits in FOO's mode and we
10032              are either testing inequality or have an unsigned
10033              comparison with ZERO_EXTEND or a signed comparison with
10034              SIGN_EXTEND.  But don't do it if we don't have a compare
10035              insn of the given mode, since we'd have to revert it
10036              later on, and then we wouldn't know whether to sign- or
10037              zero-extend.  */
10038           mode = GET_MODE (XEXP (op0, 0));
10039           if (mode != VOIDmode && GET_MODE_CLASS (mode) == MODE_INT
10040               && ! unsigned_comparison_p
10041               && (GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT)
10042               && ((unsigned HOST_WIDE_INT) const_op
10043                   < (((unsigned HOST_WIDE_INT) 1
10044                       << (GET_MODE_BITSIZE (mode) - 1))))
10045               && cmp_optab->handlers[(int) mode].insn_code != CODE_FOR_nothing)
10046             {
10047               op0 = XEXP (op0, 0);
10048               continue;
10049             }
10050           break;
10051
10052         case SUBREG:
10053           /* Check for the case where we are comparing A - C1 with C2, that is
10054
10055                (subreg:MODE (plus (A) (-C1))) op (C2)
10056
10057              with C1 a constant, and try to lift the SUBREG, i.e. to do the
10058              comparison in the wider mode.  One of the following two conditions
10059              must be true in order for this to be valid:
10060
10061                1. The mode extension results in the same bit pattern being added
10062                   on both sides and the comparison is equality or unsigned.  As
10063                   C2 has been truncated to fit in MODE, the pattern can only be
10064                   all 0s or all 1s.
10065
10066                2. The mode extension results in the sign bit being copied on
10067                   each side.
10068
10069              The difficulty here is that we have predicates for A but not for
10070              (A - C1) so we need to check that C1 is within proper bounds so
10071              as to perturbate A as little as possible.  */
10072
10073           if (mode_width <= HOST_BITS_PER_WIDE_INT
10074               && subreg_lowpart_p (op0)
10075               && GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (op0))) > mode_width
10076               && GET_CODE (SUBREG_REG (op0)) == PLUS
10077               && GET_CODE (XEXP (SUBREG_REG (op0), 1)) == CONST_INT)
10078             {
10079               enum machine_mode inner_mode = GET_MODE (SUBREG_REG (op0));
10080               rtx a = XEXP (SUBREG_REG (op0), 0);
10081               HOST_WIDE_INT c1 = -INTVAL (XEXP (SUBREG_REG (op0), 1));
10082
10083               if ((c1 > 0
10084                    && (unsigned HOST_WIDE_INT) c1
10085                        < (unsigned HOST_WIDE_INT) 1 << (mode_width - 1)
10086                    && (equality_comparison_p || unsigned_comparison_p)
10087                    /* (A - C1) zero-extends if it is positive and sign-extends
10088                       if it is negative, C2 both zero- and sign-extends.  */
10089                    && ((0 == (nonzero_bits (a, inner_mode)
10090                               & ~GET_MODE_MASK (mode))
10091                         && const_op >= 0)
10092                        /* (A - C1) sign-extends if it is positive and 1-extends
10093                           if it is negative, C2 both sign- and 1-extends.  */
10094                        || (num_sign_bit_copies (a, inner_mode)
10095                            > (unsigned int) (GET_MODE_BITSIZE (inner_mode)
10096                                              - mode_width)
10097                            && const_op < 0)))
10098                   || ((unsigned HOST_WIDE_INT) c1
10099                        < (unsigned HOST_WIDE_INT) 1 << (mode_width - 2)
10100                       /* (A - C1) always sign-extends, like C2.  */
10101                       && num_sign_bit_copies (a, inner_mode)
10102                          > (unsigned int) (GET_MODE_BITSIZE (inner_mode)
10103                                            - (mode_width - 1))))
10104                 {
10105                   op0 = SUBREG_REG (op0);
10106                   continue;
10107                 }
10108             }
10109
10110           /* If the inner mode is narrower and we are extracting the low part,
10111              we can treat the SUBREG as if it were a ZERO_EXTEND.  */
10112           if (subreg_lowpart_p (op0)
10113               && GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (op0))) < mode_width)
10114             /* Fall through */ ;
10115           else
10116             break;
10117
10118           /* ... fall through ...  */
10119
10120         case ZERO_EXTEND:
10121           mode = GET_MODE (XEXP (op0, 0));
10122           if (mode != VOIDmode && GET_MODE_CLASS (mode) == MODE_INT
10123               && (unsigned_comparison_p || equality_comparison_p)
10124               && (GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT)
10125               && ((unsigned HOST_WIDE_INT) const_op < GET_MODE_MASK (mode))
10126               && cmp_optab->handlers[(int) mode].insn_code != CODE_FOR_nothing)
10127             {
10128               op0 = XEXP (op0, 0);
10129               continue;
10130             }
10131           break;
10132
10133         case PLUS:
10134           /* (eq (plus X A) B) -> (eq X (minus B A)).  We can only do
10135              this for equality comparisons due to pathological cases involving
10136              overflows.  */
10137           if (equality_comparison_p
10138               && 0 != (tem = simplify_binary_operation (MINUS, mode,
10139                                                         op1, XEXP (op0, 1))))
10140             {
10141               op0 = XEXP (op0, 0);
10142               op1 = tem;
10143               continue;
10144             }
10145
10146           /* (plus (abs X) (const_int -1)) is < 0 if and only if X == 0.  */
10147           if (const_op == 0 && XEXP (op0, 1) == constm1_rtx
10148               && GET_CODE (XEXP (op0, 0)) == ABS && sign_bit_comparison_p)
10149             {
10150               op0 = XEXP (XEXP (op0, 0), 0);
10151               code = (code == LT ? EQ : NE);
10152               continue;
10153             }
10154           break;
10155
10156         case MINUS:
10157           /* We used to optimize signed comparisons against zero, but that
10158              was incorrect.  Unsigned comparisons against zero (GTU, LEU)
10159              arrive here as equality comparisons, or (GEU, LTU) are
10160              optimized away.  No need to special-case them.  */
10161
10162           /* (eq (minus A B) C) -> (eq A (plus B C)) or
10163              (eq B (minus A C)), whichever simplifies.  We can only do
10164              this for equality comparisons due to pathological cases involving
10165              overflows.  */
10166           if (equality_comparison_p
10167               && 0 != (tem = simplify_binary_operation (PLUS, mode,
10168                                                         XEXP (op0, 1), op1)))
10169             {
10170               op0 = XEXP (op0, 0);
10171               op1 = tem;
10172               continue;
10173             }
10174
10175           if (equality_comparison_p
10176               && 0 != (tem = simplify_binary_operation (MINUS, mode,
10177                                                         XEXP (op0, 0), op1)))
10178             {
10179               op0 = XEXP (op0, 1);
10180               op1 = tem;
10181               continue;
10182             }
10183
10184           /* The sign bit of (minus (ashiftrt X C) X), where C is the number
10185              of bits in X minus 1, is one iff X > 0.  */
10186           if (sign_bit_comparison_p && GET_CODE (XEXP (op0, 0)) == ASHIFTRT
10187               && GET_CODE (XEXP (XEXP (op0, 0), 1)) == CONST_INT
10188               && (unsigned HOST_WIDE_INT) INTVAL (XEXP (XEXP (op0, 0), 1))
10189                  == mode_width - 1
10190               && rtx_equal_p (XEXP (XEXP (op0, 0), 0), XEXP (op0, 1)))
10191             {
10192               op0 = XEXP (op0, 1);
10193               code = (code == GE ? LE : GT);
10194               continue;
10195             }
10196           break;
10197
10198         case XOR:
10199           /* (eq (xor A B) C) -> (eq A (xor B C)).  This is a simplification
10200              if C is zero or B is a constant.  */
10201           if (equality_comparison_p
10202               && 0 != (tem = simplify_binary_operation (XOR, mode,
10203                                                         XEXP (op0, 1), op1)))
10204             {
10205               op0 = XEXP (op0, 0);
10206               op1 = tem;
10207               continue;
10208             }
10209           break;
10210
10211         case EQ:  case NE:
10212         case UNEQ:  case LTGT:
10213         case LT:  case LTU:  case UNLT:  case LE:  case LEU:  case UNLE:
10214         case GT:  case GTU:  case UNGT:  case GE:  case GEU:  case UNGE:
10215         case UNORDERED: case ORDERED:
10216           /* We can't do anything if OP0 is a condition code value, rather
10217              than an actual data value.  */
10218           if (const_op != 0
10219               || CC0_P (XEXP (op0, 0))
10220               || GET_MODE_CLASS (GET_MODE (XEXP (op0, 0))) == MODE_CC)
10221             break;
10222
10223           /* Get the two operands being compared.  */
10224           if (GET_CODE (XEXP (op0, 0)) == COMPARE)
10225             tem = XEXP (XEXP (op0, 0), 0), tem1 = XEXP (XEXP (op0, 0), 1);
10226           else
10227             tem = XEXP (op0, 0), tem1 = XEXP (op0, 1);
10228
10229           /* Check for the cases where we simply want the result of the
10230              earlier test or the opposite of that result.  */
10231           if (code == NE || code == EQ
10232               || (GET_MODE_BITSIZE (GET_MODE (op0)) <= HOST_BITS_PER_WIDE_INT
10233                   && GET_MODE_CLASS (GET_MODE (op0)) == MODE_INT
10234                   && (STORE_FLAG_VALUE
10235                       & (((HOST_WIDE_INT) 1
10236                           << (GET_MODE_BITSIZE (GET_MODE (op0)) - 1))))
10237                   && (code == LT || code == GE)))
10238             {
10239               enum rtx_code new_code;
10240               if (code == LT || code == NE)
10241                 new_code = GET_CODE (op0);
10242               else
10243                 new_code = reversed_comparison_code (op0, NULL);
10244
10245               if (new_code != UNKNOWN)
10246                 {
10247                   code = new_code;
10248                   op0 = tem;
10249                   op1 = tem1;
10250                   continue;
10251                 }
10252             }
10253           break;
10254
10255         case IOR:
10256           /* The sign bit of (ior (plus X (const_int -1)) X) is nonzero
10257              iff X <= 0.  */
10258           if (sign_bit_comparison_p && GET_CODE (XEXP (op0, 0)) == PLUS
10259               && XEXP (XEXP (op0, 0), 1) == constm1_rtx
10260               && rtx_equal_p (XEXP (XEXP (op0, 0), 0), XEXP (op0, 1)))
10261             {
10262               op0 = XEXP (op0, 1);
10263               code = (code == GE ? GT : LE);
10264               continue;
10265             }
10266           break;
10267
10268         case AND:
10269           /* Convert (and (xshift 1 X) Y) to (and (lshiftrt Y X) 1).  This
10270              will be converted to a ZERO_EXTRACT later.  */
10271           if (const_op == 0 && equality_comparison_p
10272               && GET_CODE (XEXP (op0, 0)) == ASHIFT
10273               && XEXP (XEXP (op0, 0), 0) == const1_rtx)
10274             {
10275               op0 = simplify_and_const_int
10276                 (NULL_RTX, mode, gen_rtx_LSHIFTRT (mode,
10277                                                    XEXP (op0, 1),
10278                                                    XEXP (XEXP (op0, 0), 1)),
10279                  (HOST_WIDE_INT) 1);
10280               continue;
10281             }
10282
10283           /* If we are comparing (and (lshiftrt X C1) C2) for equality with
10284              zero and X is a comparison and C1 and C2 describe only bits set
10285              in STORE_FLAG_VALUE, we can compare with X.  */
10286           if (const_op == 0 && equality_comparison_p
10287               && mode_width <= HOST_BITS_PER_WIDE_INT
10288               && GET_CODE (XEXP (op0, 1)) == CONST_INT
10289               && GET_CODE (XEXP (op0, 0)) == LSHIFTRT
10290               && GET_CODE (XEXP (XEXP (op0, 0), 1)) == CONST_INT
10291               && INTVAL (XEXP (XEXP (op0, 0), 1)) >= 0
10292               && INTVAL (XEXP (XEXP (op0, 0), 1)) < HOST_BITS_PER_WIDE_INT)
10293             {
10294               mask = ((INTVAL (XEXP (op0, 1)) & GET_MODE_MASK (mode))
10295                       << INTVAL (XEXP (XEXP (op0, 0), 1)));
10296               if ((~STORE_FLAG_VALUE & mask) == 0
10297                   && (COMPARISON_P (XEXP (XEXP (op0, 0), 0))
10298                       || ((tem = get_last_value (XEXP (XEXP (op0, 0), 0))) != 0
10299                           && COMPARISON_P (tem))))
10300                 {
10301                   op0 = XEXP (XEXP (op0, 0), 0);
10302                   continue;
10303                 }
10304             }
10305
10306           /* If we are doing an equality comparison of an AND of a bit equal
10307              to the sign bit, replace this with a LT or GE comparison of
10308              the underlying value.  */
10309           if (equality_comparison_p
10310               && const_op == 0
10311               && GET_CODE (XEXP (op0, 1)) == CONST_INT
10312               && mode_width <= HOST_BITS_PER_WIDE_INT
10313               && ((INTVAL (XEXP (op0, 1)) & GET_MODE_MASK (mode))
10314                   == (unsigned HOST_WIDE_INT) 1 << (mode_width - 1)))
10315             {
10316               op0 = XEXP (op0, 0);
10317               code = (code == EQ ? GE : LT);
10318               continue;
10319             }
10320
10321           /* If this AND operation is really a ZERO_EXTEND from a narrower
10322              mode, the constant fits within that mode, and this is either an
10323              equality or unsigned comparison, try to do this comparison in
10324              the narrower mode.
10325
10326              Note that in:
10327
10328              (ne:DI (and:DI (reg:DI 4) (const_int 0xffffffff)) (const_int 0))
10329              -> (ne:DI (reg:SI 4) (const_int 0))
10330
10331              unless TRULY_NOOP_TRUNCATION allows it or the register is
10332              known to hold a value of the required mode the
10333              transformation is invalid.  */
10334           if ((equality_comparison_p || unsigned_comparison_p)
10335               && GET_CODE (XEXP (op0, 1)) == CONST_INT
10336               && (i = exact_log2 ((INTVAL (XEXP (op0, 1))
10337                                    & GET_MODE_MASK (mode))
10338                                   + 1)) >= 0
10339               && const_op >> i == 0
10340               && (tmode = mode_for_size (i, MODE_INT, 1)) != BLKmode
10341               && (TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (tmode),
10342                                          GET_MODE_BITSIZE (GET_MODE (op0)))
10343                   || (REG_P (XEXP (op0, 0))
10344                       && reg_truncated_to_mode (tmode, XEXP (op0, 0)))))
10345             {
10346               op0 = gen_lowpart (tmode, XEXP (op0, 0));
10347               continue;
10348             }
10349
10350           /* If this is (and:M1 (subreg:M2 X 0) (const_int C1)) where C1
10351              fits in both M1 and M2 and the SUBREG is either paradoxical
10352              or represents the low part, permute the SUBREG and the AND
10353              and try again.  */
10354           if (GET_CODE (XEXP (op0, 0)) == SUBREG)
10355             {
10356               unsigned HOST_WIDE_INT c1;
10357               tmode = GET_MODE (SUBREG_REG (XEXP (op0, 0)));
10358               /* Require an integral mode, to avoid creating something like
10359                  (AND:SF ...).  */
10360               if (SCALAR_INT_MODE_P (tmode)
10361                   /* It is unsafe to commute the AND into the SUBREG if the
10362                      SUBREG is paradoxical and WORD_REGISTER_OPERATIONS is
10363                      not defined.  As originally written the upper bits
10364                      have a defined value due to the AND operation.
10365                      However, if we commute the AND inside the SUBREG then
10366                      they no longer have defined values and the meaning of
10367                      the code has been changed.  */
10368                   && (0
10369 #ifdef WORD_REGISTER_OPERATIONS
10370                       || (mode_width > GET_MODE_BITSIZE (tmode)
10371                           && mode_width <= BITS_PER_WORD)
10372 #endif
10373                       || (mode_width <= GET_MODE_BITSIZE (tmode)
10374                           && subreg_lowpart_p (XEXP (op0, 0))))
10375                   && GET_CODE (XEXP (op0, 1)) == CONST_INT
10376                   && mode_width <= HOST_BITS_PER_WIDE_INT
10377                   && GET_MODE_BITSIZE (tmode) <= HOST_BITS_PER_WIDE_INT
10378                   && ((c1 = INTVAL (XEXP (op0, 1))) & ~mask) == 0
10379                   && (c1 & ~GET_MODE_MASK (tmode)) == 0
10380                   && c1 != mask
10381                   && c1 != GET_MODE_MASK (tmode))
10382                 {
10383                   op0 = simplify_gen_binary (AND, tmode,
10384                                              SUBREG_REG (XEXP (op0, 0)),
10385                                              gen_int_mode (c1, tmode));
10386                   op0 = gen_lowpart (mode, op0);
10387                   continue;
10388                 }
10389             }
10390
10391           /* Convert (ne (and (not X) 1) 0) to (eq (and X 1) 0).  */
10392           if (const_op == 0 && equality_comparison_p
10393               && XEXP (op0, 1) == const1_rtx
10394               && GET_CODE (XEXP (op0, 0)) == NOT)
10395             {
10396               op0 = simplify_and_const_int
10397                 (NULL_RTX, mode, XEXP (XEXP (op0, 0), 0), (HOST_WIDE_INT) 1);
10398               code = (code == NE ? EQ : NE);
10399               continue;
10400             }
10401
10402           /* Convert (ne (and (lshiftrt (not X)) 1) 0) to
10403              (eq (and (lshiftrt X) 1) 0).
10404              Also handle the case where (not X) is expressed using xor.  */
10405           if (const_op == 0 && equality_comparison_p
10406               && XEXP (op0, 1) == const1_rtx
10407               && GET_CODE (XEXP (op0, 0)) == LSHIFTRT)
10408             {
10409               rtx shift_op = XEXP (XEXP (op0, 0), 0);
10410               rtx shift_count = XEXP (XEXP (op0, 0), 1);
10411
10412               if (GET_CODE (shift_op) == NOT
10413                   || (GET_CODE (shift_op) == XOR
10414                       && GET_CODE (XEXP (shift_op, 1)) == CONST_INT
10415                       && GET_CODE (shift_count) == CONST_INT
10416                       && GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT
10417                       && (INTVAL (XEXP (shift_op, 1))
10418                           == (HOST_WIDE_INT) 1 << INTVAL (shift_count))))
10419                 {
10420                   op0 = simplify_and_const_int
10421                     (NULL_RTX, mode,
10422                      gen_rtx_LSHIFTRT (mode, XEXP (shift_op, 0), shift_count),
10423                      (HOST_WIDE_INT) 1);
10424                   code = (code == NE ? EQ : NE);
10425                   continue;
10426                 }
10427             }
10428           break;
10429
10430         case ASHIFT:
10431           /* If we have (compare (ashift FOO N) (const_int C)) and
10432              the high order N bits of FOO (N+1 if an inequality comparison)
10433              are known to be zero, we can do this by comparing FOO with C
10434              shifted right N bits so long as the low-order N bits of C are
10435              zero.  */
10436           if (GET_CODE (XEXP (op0, 1)) == CONST_INT
10437               && INTVAL (XEXP (op0, 1)) >= 0
10438               && ((INTVAL (XEXP (op0, 1)) + ! equality_comparison_p)
10439                   < HOST_BITS_PER_WIDE_INT)
10440               && ((const_op
10441                    & (((HOST_WIDE_INT) 1 << INTVAL (XEXP (op0, 1))) - 1)) == 0)
10442               && mode_width <= HOST_BITS_PER_WIDE_INT
10443               && (nonzero_bits (XEXP (op0, 0), mode)
10444                   & ~(mask >> (INTVAL (XEXP (op0, 1))
10445                                + ! equality_comparison_p))) == 0)
10446             {
10447               /* We must perform a logical shift, not an arithmetic one,
10448                  as we want the top N bits of C to be zero.  */
10449               unsigned HOST_WIDE_INT temp = const_op & GET_MODE_MASK (mode);
10450
10451               temp >>= INTVAL (XEXP (op0, 1));
10452               op1 = gen_int_mode (temp, mode);
10453               op0 = XEXP (op0, 0);
10454               continue;
10455             }
10456
10457           /* If we are doing a sign bit comparison, it means we are testing
10458              a particular bit.  Convert it to the appropriate AND.  */
10459           if (sign_bit_comparison_p && GET_CODE (XEXP (op0, 1)) == CONST_INT
10460               && mode_width <= HOST_BITS_PER_WIDE_INT)
10461             {
10462               op0 = simplify_and_const_int (NULL_RTX, mode, XEXP (op0, 0),
10463                                             ((HOST_WIDE_INT) 1
10464                                              << (mode_width - 1
10465                                                  - INTVAL (XEXP (op0, 1)))));
10466               code = (code == LT ? NE : EQ);
10467               continue;
10468             }
10469
10470           /* If this an equality comparison with zero and we are shifting
10471              the low bit to the sign bit, we can convert this to an AND of the
10472              low-order bit.  */
10473           if (const_op == 0 && equality_comparison_p
10474               && GET_CODE (XEXP (op0, 1)) == CONST_INT
10475               && (unsigned HOST_WIDE_INT) INTVAL (XEXP (op0, 1))
10476                  == mode_width - 1)
10477             {
10478               op0 = simplify_and_const_int (NULL_RTX, mode, XEXP (op0, 0),
10479                                             (HOST_WIDE_INT) 1);
10480               continue;
10481             }
10482           break;
10483
10484         case ASHIFTRT:
10485           /* If this is an equality comparison with zero, we can do this
10486              as a logical shift, which might be much simpler.  */
10487           if (equality_comparison_p && const_op == 0
10488               && GET_CODE (XEXP (op0, 1)) == CONST_INT)
10489             {
10490               op0 = simplify_shift_const (NULL_RTX, LSHIFTRT, mode,
10491                                           XEXP (op0, 0),
10492                                           INTVAL (XEXP (op0, 1)));
10493               continue;
10494             }
10495
10496           /* If OP0 is a sign extension and CODE is not an unsigned comparison,
10497              do the comparison in a narrower mode.  */
10498           if (! unsigned_comparison_p
10499               && GET_CODE (XEXP (op0, 1)) == CONST_INT
10500               && GET_CODE (XEXP (op0, 0)) == ASHIFT
10501               && XEXP (op0, 1) == XEXP (XEXP (op0, 0), 1)
10502               && (tmode = mode_for_size (mode_width - INTVAL (XEXP (op0, 1)),
10503                                          MODE_INT, 1)) != BLKmode
10504               && (((unsigned HOST_WIDE_INT) const_op
10505                    + (GET_MODE_MASK (tmode) >> 1) + 1)
10506                   <= GET_MODE_MASK (tmode)))
10507             {
10508               op0 = gen_lowpart (tmode, XEXP (XEXP (op0, 0), 0));
10509               continue;
10510             }
10511
10512           /* Likewise if OP0 is a PLUS of a sign extension with a
10513              constant, which is usually represented with the PLUS
10514              between the shifts.  */
10515           if (! unsigned_comparison_p
10516               && GET_CODE (XEXP (op0, 1)) == CONST_INT
10517               && GET_CODE (XEXP (op0, 0)) == PLUS
10518               && GET_CODE (XEXP (XEXP (op0, 0), 1)) == CONST_INT
10519               && GET_CODE (XEXP (XEXP (op0, 0), 0)) == ASHIFT
10520               && XEXP (op0, 1) == XEXP (XEXP (XEXP (op0, 0), 0), 1)
10521               && (tmode = mode_for_size (mode_width - INTVAL (XEXP (op0, 1)),
10522                                          MODE_INT, 1)) != BLKmode
10523               && (((unsigned HOST_WIDE_INT) const_op
10524                    + (GET_MODE_MASK (tmode) >> 1) + 1)
10525                   <= GET_MODE_MASK (tmode)))
10526             {
10527               rtx inner = XEXP (XEXP (XEXP (op0, 0), 0), 0);
10528               rtx add_const = XEXP (XEXP (op0, 0), 1);
10529               rtx new_const = simplify_gen_binary (ASHIFTRT, GET_MODE (op0),
10530                                                    add_const, XEXP (op0, 1));
10531
10532               op0 = simplify_gen_binary (PLUS, tmode,
10533                                          gen_lowpart (tmode, inner),
10534                                          new_const);
10535               continue;
10536             }
10537
10538           /* ... fall through ...  */
10539         case LSHIFTRT:
10540           /* If we have (compare (xshiftrt FOO N) (const_int C)) and
10541              the low order N bits of FOO are known to be zero, we can do this
10542              by comparing FOO with C shifted left N bits so long as no
10543              overflow occurs.  */
10544           if (GET_CODE (XEXP (op0, 1)) == CONST_INT
10545               && INTVAL (XEXP (op0, 1)) >= 0
10546               && INTVAL (XEXP (op0, 1)) < HOST_BITS_PER_WIDE_INT
10547               && mode_width <= HOST_BITS_PER_WIDE_INT
10548               && (nonzero_bits (XEXP (op0, 0), mode)
10549                   & (((HOST_WIDE_INT) 1 << INTVAL (XEXP (op0, 1))) - 1)) == 0
10550               && (((unsigned HOST_WIDE_INT) const_op
10551                    + (GET_CODE (op0) != LSHIFTRT
10552                       ? ((GET_MODE_MASK (mode) >> INTVAL (XEXP (op0, 1)) >> 1)
10553                          + 1)
10554                       : 0))
10555                   <= GET_MODE_MASK (mode) >> INTVAL (XEXP (op0, 1))))
10556             {
10557               /* If the shift was logical, then we must make the condition
10558                  unsigned.  */
10559               if (GET_CODE (op0) == LSHIFTRT)
10560                 code = unsigned_condition (code);
10561
10562               const_op <<= INTVAL (XEXP (op0, 1));
10563               op1 = GEN_INT (const_op);
10564               op0 = XEXP (op0, 0);
10565               continue;
10566             }
10567
10568           /* If we are using this shift to extract just the sign bit, we
10569              can replace this with an LT or GE comparison.  */
10570           if (const_op == 0
10571               && (equality_comparison_p || sign_bit_comparison_p)
10572               && GET_CODE (XEXP (op0, 1)) == CONST_INT
10573               && (unsigned HOST_WIDE_INT) INTVAL (XEXP (op0, 1))
10574                  == mode_width - 1)
10575             {
10576               op0 = XEXP (op0, 0);
10577               code = (code == NE || code == GT ? LT : GE);
10578               continue;
10579             }
10580           break;
10581
10582         default:
10583           break;
10584         }
10585
10586       break;
10587     }
10588
10589   /* Now make any compound operations involved in this comparison.  Then,
10590      check for an outmost SUBREG on OP0 that is not doing anything or is
10591      paradoxical.  The latter transformation must only be performed when
10592      it is known that the "extra" bits will be the same in op0 and op1 or
10593      that they don't matter.  There are three cases to consider:
10594
10595      1. SUBREG_REG (op0) is a register.  In this case the bits are don't
10596      care bits and we can assume they have any convenient value.  So
10597      making the transformation is safe.
10598
10599      2. SUBREG_REG (op0) is a memory and LOAD_EXTEND_OP is not defined.
10600      In this case the upper bits of op0 are undefined.  We should not make
10601      the simplification in that case as we do not know the contents of
10602      those bits.
10603
10604      3. SUBREG_REG (op0) is a memory and LOAD_EXTEND_OP is defined and not
10605      UNKNOWN.  In that case we know those bits are zeros or ones.  We must
10606      also be sure that they are the same as the upper bits of op1.
10607
10608      We can never remove a SUBREG for a non-equality comparison because
10609      the sign bit is in a different place in the underlying object.  */
10610
10611   op0 = make_compound_operation (op0, op1 == const0_rtx ? COMPARE : SET);
10612   op1 = make_compound_operation (op1, SET);
10613
10614   if (GET_CODE (op0) == SUBREG && subreg_lowpart_p (op0)
10615       && GET_MODE_CLASS (GET_MODE (op0)) == MODE_INT
10616       && GET_MODE_CLASS (GET_MODE (SUBREG_REG (op0))) == MODE_INT
10617       && (code == NE || code == EQ))
10618     {
10619       if (GET_MODE_SIZE (GET_MODE (op0))
10620           > GET_MODE_SIZE (GET_MODE (SUBREG_REG (op0))))
10621         {
10622           /* For paradoxical subregs, allow case 1 as above.  Case 3 isn't
10623              implemented.  */
10624           if (REG_P (SUBREG_REG (op0)))
10625             {
10626               op0 = SUBREG_REG (op0);
10627               op1 = gen_lowpart (GET_MODE (op0), op1);
10628             }
10629         }
10630       else if ((GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (op0)))
10631                 <= HOST_BITS_PER_WIDE_INT)
10632                && (nonzero_bits (SUBREG_REG (op0),
10633                                  GET_MODE (SUBREG_REG (op0)))
10634                    & ~GET_MODE_MASK (GET_MODE (op0))) == 0)
10635         {
10636           tem = gen_lowpart (GET_MODE (SUBREG_REG (op0)), op1);
10637
10638           if ((nonzero_bits (tem, GET_MODE (SUBREG_REG (op0)))
10639                & ~GET_MODE_MASK (GET_MODE (op0))) == 0)
10640             op0 = SUBREG_REG (op0), op1 = tem;
10641         }
10642     }
10643
10644   /* We now do the opposite procedure: Some machines don't have compare
10645      insns in all modes.  If OP0's mode is an integer mode smaller than a
10646      word and we can't do a compare in that mode, see if there is a larger
10647      mode for which we can do the compare.  There are a number of cases in
10648      which we can use the wider mode.  */
10649
10650   mode = GET_MODE (op0);
10651   if (mode != VOIDmode && GET_MODE_CLASS (mode) == MODE_INT
10652       && GET_MODE_SIZE (mode) < UNITS_PER_WORD
10653       && ! have_insn_for (COMPARE, mode))
10654     for (tmode = GET_MODE_WIDER_MODE (mode);
10655          (tmode != VOIDmode
10656           && GET_MODE_BITSIZE (tmode) <= HOST_BITS_PER_WIDE_INT);
10657          tmode = GET_MODE_WIDER_MODE (tmode))
10658       if (have_insn_for (COMPARE, tmode))
10659         {
10660           int zero_extended;
10661
10662           /* If the only nonzero bits in OP0 and OP1 are those in the
10663              narrower mode and this is an equality or unsigned comparison,
10664              we can use the wider mode.  Similarly for sign-extended
10665              values, in which case it is true for all comparisons.  */
10666           zero_extended = ((code == EQ || code == NE
10667                             || code == GEU || code == GTU
10668                             || code == LEU || code == LTU)
10669                            && (nonzero_bits (op0, tmode)
10670                                & ~GET_MODE_MASK (mode)) == 0
10671                            && ((GET_CODE (op1) == CONST_INT
10672                                 || (nonzero_bits (op1, tmode)
10673                                     & ~GET_MODE_MASK (mode)) == 0)));
10674
10675           if (zero_extended
10676               || ((num_sign_bit_copies (op0, tmode)
10677                    > (unsigned int) (GET_MODE_BITSIZE (tmode)
10678                                      - GET_MODE_BITSIZE (mode)))
10679                   && (num_sign_bit_copies (op1, tmode)
10680                       > (unsigned int) (GET_MODE_BITSIZE (tmode)
10681                                         - GET_MODE_BITSIZE (mode)))))
10682             {
10683               /* If OP0 is an AND and we don't have an AND in MODE either,
10684                  make a new AND in the proper mode.  */
10685               if (GET_CODE (op0) == AND
10686                   && !have_insn_for (AND, mode))
10687                 op0 = simplify_gen_binary (AND, tmode,
10688                                            gen_lowpart (tmode,
10689                                                         XEXP (op0, 0)),
10690                                            gen_lowpart (tmode,
10691                                                         XEXP (op0, 1)));
10692
10693               op0 = gen_lowpart (tmode, op0);
10694               if (zero_extended && GET_CODE (op1) == CONST_INT)
10695                 op1 = GEN_INT (INTVAL (op1) & GET_MODE_MASK (mode));
10696               op1 = gen_lowpart (tmode, op1);
10697               break;
10698             }
10699
10700           /* If this is a test for negative, we can make an explicit
10701              test of the sign bit.  */
10702
10703           if (op1 == const0_rtx && (code == LT || code == GE)
10704               && GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT)
10705             {
10706               op0 = simplify_gen_binary (AND, tmode,
10707                                          gen_lowpart (tmode, op0),
10708                                          GEN_INT ((HOST_WIDE_INT) 1
10709                                                   << (GET_MODE_BITSIZE (mode)
10710                                                       - 1)));
10711               code = (code == LT) ? NE : EQ;
10712               break;
10713             }
10714         }
10715
10716 #ifdef CANONICALIZE_COMPARISON
10717   /* If this machine only supports a subset of valid comparisons, see if we
10718      can convert an unsupported one into a supported one.  */
10719   CANONICALIZE_COMPARISON (code, op0, op1);
10720 #endif
10721
10722   *pop0 = op0;
10723   *pop1 = op1;
10724
10725   return code;
10726 }
10727 \f
10728 /* Utility function for record_value_for_reg.  Count number of
10729    rtxs in X.  */
10730 static int
10731 count_rtxs (rtx x)
10732 {
10733   enum rtx_code code = GET_CODE (x);
10734   const char *fmt;
10735   int i, ret = 1;
10736
10737   if (GET_RTX_CLASS (code) == '2'
10738       || GET_RTX_CLASS (code) == 'c')
10739     {
10740       rtx x0 = XEXP (x, 0);
10741       rtx x1 = XEXP (x, 1);
10742
10743       if (x0 == x1)
10744         return 1 + 2 * count_rtxs (x0);
10745
10746       if ((GET_RTX_CLASS (GET_CODE (x1)) == '2'
10747            || GET_RTX_CLASS (GET_CODE (x1)) == 'c')
10748           && (x0 == XEXP (x1, 0) || x0 == XEXP (x1, 1)))
10749         return 2 + 2 * count_rtxs (x0)
10750                + count_rtxs (x == XEXP (x1, 0)
10751                              ? XEXP (x1, 1) : XEXP (x1, 0));
10752
10753       if ((GET_RTX_CLASS (GET_CODE (x0)) == '2'
10754            || GET_RTX_CLASS (GET_CODE (x0)) == 'c')
10755           && (x1 == XEXP (x0, 0) || x1 == XEXP (x0, 1)))
10756         return 2 + 2 * count_rtxs (x1)
10757                + count_rtxs (x == XEXP (x0, 0)
10758                              ? XEXP (x0, 1) : XEXP (x0, 0));
10759     }
10760
10761   fmt = GET_RTX_FORMAT (code);
10762   for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
10763     if (fmt[i] == 'e')
10764       ret += count_rtxs (XEXP (x, i));
10765
10766   return ret;
10767 }
10768 \f
10769 /* Utility function for following routine.  Called when X is part of a value
10770    being stored into last_set_value.  Sets last_set_table_tick
10771    for each register mentioned.  Similar to mention_regs in cse.c  */
10772
10773 static void
10774 update_table_tick (rtx x)
10775 {
10776   enum rtx_code code = GET_CODE (x);
10777   const char *fmt = GET_RTX_FORMAT (code);
10778   int i;
10779
10780   if (code == REG)
10781     {
10782       unsigned int regno = REGNO (x);
10783       unsigned int endregno
10784         = regno + (regno < FIRST_PSEUDO_REGISTER
10785                    ? hard_regno_nregs[regno][GET_MODE (x)] : 1);
10786       unsigned int r;
10787
10788       for (r = regno; r < endregno; r++)
10789         reg_stat[r].last_set_table_tick = label_tick;
10790
10791       return;
10792     }
10793
10794   for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
10795     /* Note that we can't have an "E" in values stored; see
10796        get_last_value_validate.  */
10797     if (fmt[i] == 'e')
10798       {
10799         /* Check for identical subexpressions.  If x contains
10800            identical subexpression we only have to traverse one of
10801            them.  */
10802         if (i == 0 && ARITHMETIC_P (x))
10803           {
10804             /* Note that at this point x1 has already been
10805                processed.  */
10806             rtx x0 = XEXP (x, 0);
10807             rtx x1 = XEXP (x, 1);
10808
10809             /* If x0 and x1 are identical then there is no need to
10810                process x0.  */
10811             if (x0 == x1)
10812               break;
10813
10814             /* If x0 is identical to a subexpression of x1 then while
10815                processing x1, x0 has already been processed.  Thus we
10816                are done with x.  */
10817             if (ARITHMETIC_P (x1)
10818                 && (x0 == XEXP (x1, 0) || x0 == XEXP (x1, 1)))
10819               break;
10820
10821             /* If x1 is identical to a subexpression of x0 then we
10822                still have to process the rest of x0.  */
10823             if (ARITHMETIC_P (x0)
10824                 && (x1 == XEXP (x0, 0) || x1 == XEXP (x0, 1)))
10825               {
10826                 update_table_tick (XEXP (x0, x1 == XEXP (x0, 0) ? 1 : 0));
10827                 break;
10828               }
10829           }
10830
10831         update_table_tick (XEXP (x, i));
10832       }
10833 }
10834
10835 /* Record that REG is set to VALUE in insn INSN.  If VALUE is zero, we
10836    are saying that the register is clobbered and we no longer know its
10837    value.  If INSN is zero, don't update reg_stat[].last_set; this is
10838    only permitted with VALUE also zero and is used to invalidate the
10839    register.  */
10840
10841 static void
10842 record_value_for_reg (rtx reg, rtx insn, rtx value)
10843 {
10844   unsigned int regno = REGNO (reg);
10845   unsigned int endregno
10846     = regno + (regno < FIRST_PSEUDO_REGISTER
10847                ? hard_regno_nregs[regno][GET_MODE (reg)] : 1);
10848   unsigned int i;
10849
10850   /* If VALUE contains REG and we have a previous value for REG, substitute
10851      the previous value.  */
10852   if (value && insn && reg_overlap_mentioned_p (reg, value))
10853     {
10854       rtx tem;
10855
10856       /* Set things up so get_last_value is allowed to see anything set up to
10857          our insn.  */
10858       subst_low_cuid = INSN_CUID (insn);
10859       tem = get_last_value (reg);
10860
10861       /* If TEM is simply a binary operation with two CLOBBERs as operands,
10862          it isn't going to be useful and will take a lot of time to process,
10863          so just use the CLOBBER.  */
10864
10865       if (tem)
10866         {
10867           if (ARITHMETIC_P (tem)
10868               && GET_CODE (XEXP (tem, 0)) == CLOBBER
10869               && GET_CODE (XEXP (tem, 1)) == CLOBBER)
10870             tem = XEXP (tem, 0);
10871           else if (count_occurrences (value, reg, 1) >= 2)
10872             {
10873               /* If there are two or more occurrences of REG in VALUE,
10874                  prevent the value from growing too much.  */
10875               if (count_rtxs (tem) > MAX_LAST_VALUE_RTL)
10876                 tem = gen_rtx_CLOBBER (GET_MODE (tem), const0_rtx);
10877             }
10878
10879           value = replace_rtx (copy_rtx (value), reg, tem);
10880         }
10881     }
10882
10883   /* For each register modified, show we don't know its value, that
10884      we don't know about its bitwise content, that its value has been
10885      updated, and that we don't know the location of the death of the
10886      register.  */
10887   for (i = regno; i < endregno; i++)
10888     {
10889       if (insn)
10890         reg_stat[i].last_set = insn;
10891
10892       reg_stat[i].last_set_value = 0;
10893       reg_stat[i].last_set_mode = 0;
10894       reg_stat[i].last_set_nonzero_bits = 0;
10895       reg_stat[i].last_set_sign_bit_copies = 0;
10896       reg_stat[i].last_death = 0;
10897       reg_stat[i].truncated_to_mode = 0;
10898     }
10899
10900   /* Mark registers that are being referenced in this value.  */
10901   if (value)
10902     update_table_tick (value);
10903
10904   /* Now update the status of each register being set.
10905      If someone is using this register in this block, set this register
10906      to invalid since we will get confused between the two lives in this
10907      basic block.  This makes using this register always invalid.  In cse, we
10908      scan the table to invalidate all entries using this register, but this
10909      is too much work for us.  */
10910
10911   for (i = regno; i < endregno; i++)
10912     {
10913       reg_stat[i].last_set_label = label_tick;
10914       if (!insn || (value && reg_stat[i].last_set_table_tick == label_tick))
10915         reg_stat[i].last_set_invalid = 1;
10916       else
10917         reg_stat[i].last_set_invalid = 0;
10918     }
10919
10920   /* The value being assigned might refer to X (like in "x++;").  In that
10921      case, we must replace it with (clobber (const_int 0)) to prevent
10922      infinite loops.  */
10923   if (value && ! get_last_value_validate (&value, insn,
10924                                           reg_stat[regno].last_set_label, 0))
10925     {
10926       value = copy_rtx (value);
10927       if (! get_last_value_validate (&value, insn,
10928                                      reg_stat[regno].last_set_label, 1))
10929         value = 0;
10930     }
10931
10932   /* For the main register being modified, update the value, the mode, the
10933      nonzero bits, and the number of sign bit copies.  */
10934
10935   reg_stat[regno].last_set_value = value;
10936
10937   if (value)
10938     {
10939       enum machine_mode mode = GET_MODE (reg);
10940       subst_low_cuid = INSN_CUID (insn);
10941       reg_stat[regno].last_set_mode = mode;
10942       if (GET_MODE_CLASS (mode) == MODE_INT
10943           && GET_MODE_BITSIZE (mode) <= HOST_BITS_PER_WIDE_INT)
10944         mode = nonzero_bits_mode;
10945       reg_stat[regno].last_set_nonzero_bits = nonzero_bits (value, mode);
10946       reg_stat[regno].last_set_sign_bit_copies
10947         = num_sign_bit_copies (value, GET_MODE (reg));
10948     }
10949 }
10950
10951 /* Called via note_stores from record_dead_and_set_regs to handle one
10952    SET or CLOBBER in an insn.  DATA is the instruction in which the
10953    set is occurring.  */
10954
10955 static void
10956 record_dead_and_set_regs_1 (rtx dest, rtx setter, void *data)
10957 {
10958   rtx record_dead_insn = (rtx) data;
10959
10960   if (GET_CODE (dest) == SUBREG)
10961     dest = SUBREG_REG (dest);
10962
10963   if (!record_dead_insn)
10964     {
10965       if (REG_P (dest))
10966         record_value_for_reg (dest, NULL_RTX, NULL_RTX);
10967       return;
10968     }
10969
10970   if (REG_P (dest))
10971     {
10972       /* If we are setting the whole register, we know its value.  Otherwise
10973          show that we don't know the value.  We can handle SUBREG in
10974          some cases.  */
10975       if (GET_CODE (setter) == SET && dest == SET_DEST (setter))
10976         record_value_for_reg (dest, record_dead_insn, SET_SRC (setter));
10977       else if (GET_CODE (setter) == SET
10978                && GET_CODE (SET_DEST (setter)) == SUBREG
10979                && SUBREG_REG (SET_DEST (setter)) == dest
10980                && GET_MODE_BITSIZE (GET_MODE (dest)) <= BITS_PER_WORD
10981                && subreg_lowpart_p (SET_DEST (setter)))
10982         record_value_for_reg (dest, record_dead_insn,
10983                               gen_lowpart (GET_MODE (dest),
10984                                                        SET_SRC (setter)));
10985       else
10986         record_value_for_reg (dest, record_dead_insn, NULL_RTX);
10987     }
10988   else if (MEM_P (dest)
10989            /* Ignore pushes, they clobber nothing.  */
10990            && ! push_operand (dest, GET_MODE (dest)))
10991     mem_last_set = INSN_CUID (record_dead_insn);
10992 }
10993
10994 /* Update the records of when each REG was most recently set or killed
10995    for the things done by INSN.  This is the last thing done in processing
10996    INSN in the combiner loop.
10997
10998    We update reg_stat[], in particular fields last_set, last_set_value,
10999    last_set_mode, last_set_nonzero_bits, last_set_sign_bit_copies,
11000    last_death, and also the similar information mem_last_set (which insn
11001    most recently modified memory) and last_call_cuid (which insn was the
11002    most recent subroutine call).  */
11003
11004 static void
11005 record_dead_and_set_regs (rtx insn)
11006 {
11007   rtx link;
11008   unsigned int i;
11009
11010   for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
11011     {
11012       if (REG_NOTE_KIND (link) == REG_DEAD
11013           && REG_P (XEXP (link, 0)))
11014         {
11015           unsigned int regno = REGNO (XEXP (link, 0));
11016           unsigned int endregno
11017             = regno + (regno < FIRST_PSEUDO_REGISTER
11018                        ? hard_regno_nregs[regno][GET_MODE (XEXP (link, 0))]
11019                        : 1);
11020
11021           for (i = regno; i < endregno; i++)
11022             reg_stat[i].last_death = insn;
11023         }
11024       else if (REG_NOTE_KIND (link) == REG_INC)
11025         record_value_for_reg (XEXP (link, 0), insn, NULL_RTX);
11026     }
11027
11028   if (CALL_P (insn))
11029     {
11030       for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
11031         if (TEST_HARD_REG_BIT (regs_invalidated_by_call, i))
11032           {
11033             reg_stat[i].last_set_value = 0;
11034             reg_stat[i].last_set_mode = 0;
11035             reg_stat[i].last_set_nonzero_bits = 0;
11036             reg_stat[i].last_set_sign_bit_copies = 0;
11037             reg_stat[i].last_death = 0;
11038             reg_stat[i].truncated_to_mode = 0;
11039           }
11040
11041       last_call_cuid = mem_last_set = INSN_CUID (insn);
11042
11043       /* We can't combine into a call pattern.  Remember, though, that
11044          the return value register is set at this CUID.  We could
11045          still replace a register with the return value from the
11046          wrong subroutine call!  */
11047       note_stores (PATTERN (insn), record_dead_and_set_regs_1, NULL_RTX);
11048     }
11049   else
11050     note_stores (PATTERN (insn), record_dead_and_set_regs_1, insn);
11051 }
11052
11053 /* If a SUBREG has the promoted bit set, it is in fact a property of the
11054    register present in the SUBREG, so for each such SUBREG go back and
11055    adjust nonzero and sign bit information of the registers that are
11056    known to have some zero/sign bits set.
11057
11058    This is needed because when combine blows the SUBREGs away, the
11059    information on zero/sign bits is lost and further combines can be
11060    missed because of that.  */
11061
11062 static void
11063 record_promoted_value (rtx insn, rtx subreg)
11064 {
11065   rtx links, set;
11066   unsigned int regno = REGNO (SUBREG_REG (subreg));
11067   enum machine_mode mode = GET_MODE (subreg);
11068
11069   if (GET_MODE_BITSIZE (mode) > HOST_BITS_PER_WIDE_INT)
11070     return;
11071
11072   for (links = LOG_LINKS (insn); links;)
11073     {
11074       insn = XEXP (links, 0);
11075       set = single_set (insn);
11076
11077       if (! set || !REG_P (SET_DEST (set))
11078           || REGNO (SET_DEST (set)) != regno
11079           || GET_MODE (SET_DEST (set)) != GET_MODE (SUBREG_REG (subreg)))
11080         {
11081           links = XEXP (links, 1);
11082           continue;
11083         }
11084
11085       if (reg_stat[regno].last_set == insn)
11086         {
11087           if (SUBREG_PROMOTED_UNSIGNED_P (subreg) > 0)
11088             reg_stat[regno].last_set_nonzero_bits &= GET_MODE_MASK (mode);
11089         }
11090
11091       if (REG_P (SET_SRC (set)))
11092         {
11093           regno = REGNO (SET_SRC (set));
11094           links = LOG_LINKS (insn);
11095         }
11096       else
11097         break;
11098     }
11099 }
11100
11101 /* Check if X, a register, is known to contain a value already
11102    truncated to MODE.  In this case we can use a subreg to refer to
11103    the truncated value even though in the generic case we would need
11104    an explicit truncation.  */
11105
11106 static bool
11107 reg_truncated_to_mode (enum machine_mode mode, rtx x)
11108 {
11109   enum machine_mode truncated = reg_stat[REGNO (x)].truncated_to_mode;
11110
11111   if (truncated == 0 || reg_stat[REGNO (x)].truncation_label != label_tick)
11112     return false;
11113   if (GET_MODE_SIZE (truncated) <= GET_MODE_SIZE (mode))
11114     return true;
11115   if (TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (mode),
11116                              GET_MODE_BITSIZE (truncated)))
11117     return true;
11118   return false;
11119 }
11120
11121 /* X is a REG or a SUBREG.  If X is some sort of a truncation record
11122    it.  For non-TRULY_NOOP_TRUNCATION targets we might be able to turn
11123    a truncate into a subreg using this information.  */
11124
11125 static void
11126 record_truncated_value (rtx x)
11127 {
11128   enum machine_mode truncated_mode;
11129
11130   if (GET_CODE (x) == SUBREG && REG_P (SUBREG_REG (x)))
11131     {
11132       enum machine_mode original_mode = GET_MODE (SUBREG_REG (x));
11133       truncated_mode = GET_MODE (x);
11134
11135       if (GET_MODE_SIZE (original_mode) <= GET_MODE_SIZE (truncated_mode))
11136         return;
11137
11138       if (TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (truncated_mode),
11139                                  GET_MODE_BITSIZE (original_mode)))
11140         return;
11141
11142       x = SUBREG_REG (x);
11143     }
11144   /* ??? For hard-regs we now record everything.  We might be able to
11145      optimize this using last_set_mode.  */
11146   else if (REG_P (x) && REGNO (x) < FIRST_PSEUDO_REGISTER)
11147     truncated_mode = GET_MODE (x);
11148   else
11149     return;
11150
11151   if (reg_stat[REGNO (x)].truncated_to_mode == 0
11152       || reg_stat[REGNO (x)].truncation_label < label_tick
11153       || (GET_MODE_SIZE (truncated_mode)
11154           < GET_MODE_SIZE (reg_stat[REGNO (x)].truncated_to_mode)))
11155     {
11156       reg_stat[REGNO (x)].truncated_to_mode = truncated_mode;
11157       reg_stat[REGNO (x)].truncation_label = label_tick;
11158     }
11159 }
11160
11161 /* Scan X for promoted SUBREGs and truncated REGs.  For each one
11162    found, note what it implies to the registers used in it.  */
11163
11164 static void
11165 check_conversions (rtx insn, rtx x)
11166 {
11167   if (GET_CODE (x) == SUBREG || REG_P (x))
11168     {
11169       if (GET_CODE (x) == SUBREG
11170           && SUBREG_PROMOTED_VAR_P (x)
11171           && REG_P (SUBREG_REG (x)))
11172         record_promoted_value (insn, x);
11173
11174       record_truncated_value (x);
11175     }
11176   else
11177     {
11178       const char *format = GET_RTX_FORMAT (GET_CODE (x));
11179       int i, j;
11180
11181       for (i = 0; i < GET_RTX_LENGTH (GET_CODE (x)); i++)
11182         switch (format[i])
11183           {
11184           case 'e':
11185             check_conversions (insn, XEXP (x, i));
11186             break;
11187           case 'V':
11188           case 'E':
11189             if (XVEC (x, i) != 0)
11190               for (j = 0; j < XVECLEN (x, i); j++)
11191                 check_conversions (insn, XVECEXP (x, i, j));
11192             break;
11193           }
11194     }
11195 }
11196 \f
11197 /* Utility routine for the following function.  Verify that all the registers
11198    mentioned in *LOC are valid when *LOC was part of a value set when
11199    label_tick == TICK.  Return 0 if some are not.
11200
11201    If REPLACE is nonzero, replace the invalid reference with
11202    (clobber (const_int 0)) and return 1.  This replacement is useful because
11203    we often can get useful information about the form of a value (e.g., if
11204    it was produced by a shift that always produces -1 or 0) even though
11205    we don't know exactly what registers it was produced from.  */
11206
11207 static int
11208 get_last_value_validate (rtx *loc, rtx insn, int tick, int replace)
11209 {
11210   rtx x = *loc;
11211   const char *fmt = GET_RTX_FORMAT (GET_CODE (x));
11212   int len = GET_RTX_LENGTH (GET_CODE (x));
11213   int i;
11214
11215   if (REG_P (x))
11216     {
11217       unsigned int regno = REGNO (x);
11218       unsigned int endregno
11219         = regno + (regno < FIRST_PSEUDO_REGISTER
11220                    ? hard_regno_nregs[regno][GET_MODE (x)] : 1);
11221       unsigned int j;
11222
11223       for (j = regno; j < endregno; j++)
11224         if (reg_stat[j].last_set_invalid
11225             /* If this is a pseudo-register that was only set once and not
11226                live at the beginning of the function, it is always valid.  */
11227             || (! (regno >= FIRST_PSEUDO_REGISTER
11228                    && REG_N_SETS (regno) == 1
11229                    && (! REGNO_REG_SET_P
11230                        (ENTRY_BLOCK_PTR->next_bb->il.rtl->global_live_at_start,
11231                         regno)))
11232                 && reg_stat[j].last_set_label > tick))
11233           {
11234             if (replace)
11235               *loc = gen_rtx_CLOBBER (GET_MODE (x), const0_rtx);
11236             return replace;
11237           }
11238
11239       return 1;
11240     }
11241   /* If this is a memory reference, make sure that there were
11242      no stores after it that might have clobbered the value.  We don't
11243      have alias info, so we assume any store invalidates it.  */
11244   else if (MEM_P (x) && !MEM_READONLY_P (x)
11245            && INSN_CUID (insn) <= mem_last_set)
11246     {
11247       if (replace)
11248         *loc = gen_rtx_CLOBBER (GET_MODE (x), const0_rtx);
11249       return replace;
11250     }
11251
11252   for (i = 0; i < len; i++)
11253     {
11254       if (fmt[i] == 'e')
11255         {
11256           /* Check for identical subexpressions.  If x contains
11257              identical subexpression we only have to traverse one of
11258              them.  */
11259           if (i == 1 && ARITHMETIC_P (x))
11260             {
11261               /* Note that at this point x0 has already been checked
11262                  and found valid.  */
11263               rtx x0 = XEXP (x, 0);
11264               rtx x1 = XEXP (x, 1);
11265
11266               /* If x0 and x1 are identical then x is also valid.  */
11267               if (x0 == x1)
11268                 return 1;
11269
11270               /* If x1 is identical to a subexpression of x0 then
11271                  while checking x0, x1 has already been checked.  Thus
11272                  it is valid and so as x.  */
11273               if (ARITHMETIC_P (x0)
11274                   && (x1 == XEXP (x0, 0) || x1 == XEXP (x0, 1)))
11275                 return 1;
11276
11277               /* If x0 is identical to a subexpression of x1 then x is
11278                  valid iff the rest of x1 is valid.  */
11279               if (ARITHMETIC_P (x1)
11280                   && (x0 == XEXP (x1, 0) || x0 == XEXP (x1, 1)))
11281                 return
11282                   get_last_value_validate (&XEXP (x1,
11283                                                   x0 == XEXP (x1, 0) ? 1 : 0),
11284                                            insn, tick, replace);
11285             }
11286
11287           if (get_last_value_validate (&XEXP (x, i), insn, tick,
11288                                        replace) == 0)
11289             return 0;
11290         }
11291       /* Don't bother with these.  They shouldn't occur anyway.  */
11292       else if (fmt[i] == 'E')
11293         return 0;
11294     }
11295
11296   /* If we haven't found a reason for it to be invalid, it is valid.  */
11297   return 1;
11298 }
11299
11300 /* Get the last value assigned to X, if known.  Some registers
11301    in the value may be replaced with (clobber (const_int 0)) if their value
11302    is known longer known reliably.  */
11303
11304 static rtx
11305 get_last_value (rtx x)
11306 {
11307   unsigned int regno;
11308   rtx value;
11309
11310   /* If this is a non-paradoxical SUBREG, get the value of its operand and
11311      then convert it to the desired mode.  If this is a paradoxical SUBREG,
11312      we cannot predict what values the "extra" bits might have.  */
11313   if (GET_CODE (x) == SUBREG
11314       && subreg_lowpart_p (x)
11315       && (GET_MODE_SIZE (GET_MODE (x))
11316           <= GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))))
11317       && (value = get_last_value (SUBREG_REG (x))) != 0)
11318     return gen_lowpart (GET_MODE (x), value);
11319
11320   if (!REG_P (x))
11321     return 0;
11322
11323   regno = REGNO (x);
11324   value = reg_stat[regno].last_set_value;
11325
11326   /* If we don't have a value, or if it isn't for this basic block and
11327      it's either a hard register, set more than once, or it's a live
11328      at the beginning of the function, return 0.
11329
11330      Because if it's not live at the beginning of the function then the reg
11331      is always set before being used (is never used without being set).
11332      And, if it's set only once, and it's always set before use, then all
11333      uses must have the same last value, even if it's not from this basic
11334      block.  */
11335
11336   if (value == 0
11337       || (reg_stat[regno].last_set_label != label_tick
11338           && (regno < FIRST_PSEUDO_REGISTER
11339               || REG_N_SETS (regno) != 1
11340               || (REGNO_REG_SET_P
11341                   (ENTRY_BLOCK_PTR->next_bb->il.rtl->global_live_at_start,
11342                    regno)))))
11343     return 0;
11344
11345   /* If the value was set in a later insn than the ones we are processing,
11346      we can't use it even if the register was only set once.  */
11347   if (INSN_CUID (reg_stat[regno].last_set) >= subst_low_cuid)
11348     return 0;
11349
11350   /* If the value has all its registers valid, return it.  */
11351   if (get_last_value_validate (&value, reg_stat[regno].last_set,
11352                                reg_stat[regno].last_set_label, 0))
11353     return value;
11354
11355   /* Otherwise, make a copy and replace any invalid register with
11356      (clobber (const_int 0)).  If that fails for some reason, return 0.  */
11357
11358   value = copy_rtx (value);
11359   if (get_last_value_validate (&value, reg_stat[regno].last_set,
11360                                reg_stat[regno].last_set_label, 1))
11361     return value;
11362
11363   return 0;
11364 }
11365 \f
11366 /* Return nonzero if expression X refers to a REG or to memory
11367    that is set in an instruction more recent than FROM_CUID.  */
11368
11369 static int
11370 use_crosses_set_p (rtx x, int from_cuid)
11371 {
11372   const char *fmt;
11373   int i;
11374   enum rtx_code code = GET_CODE (x);
11375
11376   if (code == REG)
11377     {
11378       unsigned int regno = REGNO (x);
11379       unsigned endreg = regno + (regno < FIRST_PSEUDO_REGISTER
11380                                  ? hard_regno_nregs[regno][GET_MODE (x)] : 1);
11381
11382 #ifdef PUSH_ROUNDING
11383       /* Don't allow uses of the stack pointer to be moved,
11384          because we don't know whether the move crosses a push insn.  */
11385       if (regno == STACK_POINTER_REGNUM && PUSH_ARGS)
11386         return 1;
11387 #endif
11388       for (; regno < endreg; regno++)
11389         if (reg_stat[regno].last_set
11390             && INSN_CUID (reg_stat[regno].last_set) > from_cuid)
11391           return 1;
11392       return 0;
11393     }
11394
11395   if (code == MEM && mem_last_set > from_cuid)
11396     return 1;
11397
11398   fmt = GET_RTX_FORMAT (code);
11399
11400   for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
11401     {
11402       if (fmt[i] == 'E')
11403         {
11404           int j;
11405           for (j = XVECLEN (x, i) - 1; j >= 0; j--)
11406             if (use_crosses_set_p (XVECEXP (x, i, j), from_cuid))
11407               return 1;
11408         }
11409       else if (fmt[i] == 'e'
11410                && use_crosses_set_p (XEXP (x, i), from_cuid))
11411         return 1;
11412     }
11413   return 0;
11414 }
11415 \f
11416 /* Define three variables used for communication between the following
11417    routines.  */
11418
11419 static unsigned int reg_dead_regno, reg_dead_endregno;
11420 static int reg_dead_flag;
11421
11422 /* Function called via note_stores from reg_dead_at_p.
11423
11424    If DEST is within [reg_dead_regno, reg_dead_endregno), set
11425    reg_dead_flag to 1 if X is a CLOBBER and to -1 it is a SET.  */
11426
11427 static void
11428 reg_dead_at_p_1 (rtx dest, rtx x, void *data ATTRIBUTE_UNUSED)
11429 {
11430   unsigned int regno, endregno;
11431
11432   if (!REG_P (dest))
11433     return;
11434
11435   regno = REGNO (dest);
11436   endregno = regno + (regno < FIRST_PSEUDO_REGISTER
11437                       ? hard_regno_nregs[regno][GET_MODE (dest)] : 1);
11438
11439   if (reg_dead_endregno > regno && reg_dead_regno < endregno)
11440     reg_dead_flag = (GET_CODE (x) == CLOBBER) ? 1 : -1;
11441 }
11442
11443 /* Return nonzero if REG is known to be dead at INSN.
11444
11445    We scan backwards from INSN.  If we hit a REG_DEAD note or a CLOBBER
11446    referencing REG, it is dead.  If we hit a SET referencing REG, it is
11447    live.  Otherwise, see if it is live or dead at the start of the basic
11448    block we are in.  Hard regs marked as being live in NEWPAT_USED_REGS
11449    must be assumed to be always live.  */
11450
11451 static int
11452 reg_dead_at_p (rtx reg, rtx insn)
11453 {
11454   basic_block block;
11455   unsigned int i;
11456
11457   /* Set variables for reg_dead_at_p_1.  */
11458   reg_dead_regno = REGNO (reg);
11459   reg_dead_endregno = reg_dead_regno + (reg_dead_regno < FIRST_PSEUDO_REGISTER
11460                                         ? hard_regno_nregs[reg_dead_regno]
11461                                                           [GET_MODE (reg)]
11462                                         : 1);
11463
11464   reg_dead_flag = 0;
11465
11466   /* Check that reg isn't mentioned in NEWPAT_USED_REGS.  For fixed registers
11467      we allow the machine description to decide whether use-and-clobber
11468      patterns are OK.  */
11469   if (reg_dead_regno < FIRST_PSEUDO_REGISTER)
11470     {
11471       for (i = reg_dead_regno; i < reg_dead_endregno; i++)
11472         if (!fixed_regs[i] && TEST_HARD_REG_BIT (newpat_used_regs, i))
11473           return 0;
11474     }
11475
11476   /* Scan backwards until we find a REG_DEAD note, SET, CLOBBER, label, or
11477      beginning of function.  */
11478   for (; insn && !LABEL_P (insn) && !BARRIER_P (insn);
11479        insn = prev_nonnote_insn (insn))
11480     {
11481       note_stores (PATTERN (insn), reg_dead_at_p_1, NULL);
11482       if (reg_dead_flag)
11483         return reg_dead_flag == 1 ? 1 : 0;
11484
11485       if (find_regno_note (insn, REG_DEAD, reg_dead_regno))
11486         return 1;
11487     }
11488
11489   /* Get the basic block that we were in.  */
11490   if (insn == 0)
11491     block = ENTRY_BLOCK_PTR->next_bb;
11492   else
11493     {
11494       FOR_EACH_BB (block)
11495         if (insn == BB_HEAD (block))
11496           break;
11497
11498       if (block == EXIT_BLOCK_PTR)
11499         return 0;
11500     }
11501
11502   for (i = reg_dead_regno; i < reg_dead_endregno; i++)
11503     if (REGNO_REG_SET_P (block->il.rtl->global_live_at_start, i))
11504       return 0;
11505
11506   return 1;
11507 }
11508 \f
11509 /* Note hard registers in X that are used.  This code is similar to
11510    that in flow.c, but much simpler since we don't care about pseudos.  */
11511
11512 static void
11513 mark_used_regs_combine (rtx x)
11514 {
11515   RTX_CODE code = GET_CODE (x);
11516   unsigned int regno;
11517   int i;
11518
11519   switch (code)
11520     {
11521     case LABEL_REF:
11522     case SYMBOL_REF:
11523     case CONST_INT:
11524     case CONST:
11525     case CONST_DOUBLE:
11526     case CONST_VECTOR:
11527     case PC:
11528     case ADDR_VEC:
11529     case ADDR_DIFF_VEC:
11530     case ASM_INPUT:
11531 #ifdef HAVE_cc0
11532     /* CC0 must die in the insn after it is set, so we don't need to take
11533        special note of it here.  */
11534     case CC0:
11535 #endif
11536       return;
11537
11538     case CLOBBER:
11539       /* If we are clobbering a MEM, mark any hard registers inside the
11540          address as used.  */
11541       if (MEM_P (XEXP (x, 0)))
11542         mark_used_regs_combine (XEXP (XEXP (x, 0), 0));
11543       return;
11544
11545     case REG:
11546       regno = REGNO (x);
11547       /* A hard reg in a wide mode may really be multiple registers.
11548          If so, mark all of them just like the first.  */
11549       if (regno < FIRST_PSEUDO_REGISTER)
11550         {
11551           unsigned int endregno, r;
11552
11553           /* None of this applies to the stack, frame or arg pointers.  */
11554           if (regno == STACK_POINTER_REGNUM
11555 #if FRAME_POINTER_REGNUM != HARD_FRAME_POINTER_REGNUM
11556               || regno == HARD_FRAME_POINTER_REGNUM
11557 #endif
11558 #if FRAME_POINTER_REGNUM != ARG_POINTER_REGNUM
11559               || (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
11560 #endif
11561               || regno == FRAME_POINTER_REGNUM)
11562             return;
11563
11564           endregno = regno + hard_regno_nregs[regno][GET_MODE (x)];
11565           for (r = regno; r < endregno; r++)
11566             SET_HARD_REG_BIT (newpat_used_regs, r);
11567         }
11568       return;
11569
11570     case SET:
11571       {
11572         /* If setting a MEM, or a SUBREG of a MEM, then note any hard regs in
11573            the address.  */
11574         rtx testreg = SET_DEST (x);
11575
11576         while (GET_CODE (testreg) == SUBREG
11577                || GET_CODE (testreg) == ZERO_EXTRACT
11578                || GET_CODE (testreg) == STRICT_LOW_PART)
11579           testreg = XEXP (testreg, 0);
11580
11581         if (MEM_P (testreg))
11582           mark_used_regs_combine (XEXP (testreg, 0));
11583
11584         mark_used_regs_combine (SET_SRC (x));
11585       }
11586       return;
11587
11588     default:
11589       break;
11590     }
11591
11592   /* Recursively scan the operands of this expression.  */
11593
11594   {
11595     const char *fmt = GET_RTX_FORMAT (code);
11596
11597     for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
11598       {
11599         if (fmt[i] == 'e')
11600           mark_used_regs_combine (XEXP (x, i));
11601         else if (fmt[i] == 'E')
11602           {
11603             int j;
11604
11605             for (j = 0; j < XVECLEN (x, i); j++)
11606               mark_used_regs_combine (XVECEXP (x, i, j));
11607           }
11608       }
11609   }
11610 }
11611 \f
11612 /* Remove register number REGNO from the dead registers list of INSN.
11613
11614    Return the note used to record the death, if there was one.  */
11615
11616 rtx
11617 remove_death (unsigned int regno, rtx insn)
11618 {
11619   rtx note = find_regno_note (insn, REG_DEAD, regno);
11620
11621   if (note)
11622     {
11623       REG_N_DEATHS (regno)--;
11624       remove_note (insn, note);
11625     }
11626
11627   return note;
11628 }
11629
11630 /* For each register (hardware or pseudo) used within expression X, if its
11631    death is in an instruction with cuid between FROM_CUID (inclusive) and
11632    TO_INSN (exclusive), put a REG_DEAD note for that register in the
11633    list headed by PNOTES.
11634
11635    That said, don't move registers killed by maybe_kill_insn.
11636
11637    This is done when X is being merged by combination into TO_INSN.  These
11638    notes will then be distributed as needed.  */
11639
11640 static void
11641 move_deaths (rtx x, rtx maybe_kill_insn, int from_cuid, rtx to_insn,
11642              rtx *pnotes)
11643 {
11644   const char *fmt;
11645   int len, i;
11646   enum rtx_code code = GET_CODE (x);
11647
11648   if (code == REG)
11649     {
11650       unsigned int regno = REGNO (x);
11651       rtx where_dead = reg_stat[regno].last_death;
11652       rtx before_dead, after_dead;
11653
11654       /* Don't move the register if it gets killed in between from and to.  */
11655       if (maybe_kill_insn && reg_set_p (x, maybe_kill_insn)
11656           && ! reg_referenced_p (x, maybe_kill_insn))
11657         return;
11658
11659       /* WHERE_DEAD could be a USE insn made by combine, so first we
11660          make sure that we have insns with valid INSN_CUID values.  */
11661       before_dead = where_dead;
11662       while (before_dead && INSN_UID (before_dead) > max_uid_cuid)
11663         before_dead = PREV_INSN (before_dead);
11664
11665       after_dead = where_dead;
11666       while (after_dead && INSN_UID (after_dead) > max_uid_cuid)
11667         after_dead = NEXT_INSN (after_dead);
11668
11669       if (before_dead && after_dead
11670           && INSN_CUID (before_dead) >= from_cuid
11671           && (INSN_CUID (after_dead) < INSN_CUID (to_insn)
11672               || (where_dead != after_dead
11673                   && INSN_CUID (after_dead) == INSN_CUID (to_insn))))
11674         {
11675           rtx note = remove_death (regno, where_dead);
11676
11677           /* It is possible for the call above to return 0.  This can occur
11678              when last_death points to I2 or I1 that we combined with.
11679              In that case make a new note.
11680
11681              We must also check for the case where X is a hard register
11682              and NOTE is a death note for a range of hard registers
11683              including X.  In that case, we must put REG_DEAD notes for
11684              the remaining registers in place of NOTE.  */
11685
11686           if (note != 0 && regno < FIRST_PSEUDO_REGISTER
11687               && (GET_MODE_SIZE (GET_MODE (XEXP (note, 0)))
11688                   > GET_MODE_SIZE (GET_MODE (x))))
11689             {
11690               unsigned int deadregno = REGNO (XEXP (note, 0));
11691               unsigned int deadend
11692                 = (deadregno + hard_regno_nregs[deadregno]
11693                                                [GET_MODE (XEXP (note, 0))]);
11694               unsigned int ourend
11695                 = regno + hard_regno_nregs[regno][GET_MODE (x)];
11696               unsigned int i;
11697
11698               for (i = deadregno; i < deadend; i++)
11699                 if (i < regno || i >= ourend)
11700                   REG_NOTES (where_dead)
11701                     = gen_rtx_EXPR_LIST (REG_DEAD,
11702                                          regno_reg_rtx[i],
11703                                          REG_NOTES (where_dead));
11704             }
11705
11706           /* If we didn't find any note, or if we found a REG_DEAD note that
11707              covers only part of the given reg, and we have a multi-reg hard
11708              register, then to be safe we must check for REG_DEAD notes
11709              for each register other than the first.  They could have
11710              their own REG_DEAD notes lying around.  */
11711           else if ((note == 0
11712                     || (note != 0
11713                         && (GET_MODE_SIZE (GET_MODE (XEXP (note, 0)))
11714                             < GET_MODE_SIZE (GET_MODE (x)))))
11715                    && regno < FIRST_PSEUDO_REGISTER
11716                    && hard_regno_nregs[regno][GET_MODE (x)] > 1)
11717             {
11718               unsigned int ourend
11719                 = regno + hard_regno_nregs[regno][GET_MODE (x)];
11720               unsigned int i, offset;
11721               rtx oldnotes = 0;
11722
11723               if (note)
11724                 offset = hard_regno_nregs[regno][GET_MODE (XEXP (note, 0))];
11725               else
11726                 offset = 1;
11727
11728               for (i = regno + offset; i < ourend; i++)
11729                 move_deaths (regno_reg_rtx[i],
11730                              maybe_kill_insn, from_cuid, to_insn, &oldnotes);
11731             }
11732
11733           if (note != 0 && GET_MODE (XEXP (note, 0)) == GET_MODE (x))
11734             {
11735               XEXP (note, 1) = *pnotes;
11736               *pnotes = note;
11737             }
11738           else
11739             *pnotes = gen_rtx_EXPR_LIST (REG_DEAD, x, *pnotes);
11740
11741           REG_N_DEATHS (regno)++;
11742         }
11743
11744       return;
11745     }
11746
11747   else if (GET_CODE (x) == SET)
11748     {
11749       rtx dest = SET_DEST (x);
11750
11751       move_deaths (SET_SRC (x), maybe_kill_insn, from_cuid, to_insn, pnotes);
11752
11753       /* In the case of a ZERO_EXTRACT, a STRICT_LOW_PART, or a SUBREG
11754          that accesses one word of a multi-word item, some
11755          piece of everything register in the expression is used by
11756          this insn, so remove any old death.  */
11757       /* ??? So why do we test for equality of the sizes?  */
11758
11759       if (GET_CODE (dest) == ZERO_EXTRACT
11760           || GET_CODE (dest) == STRICT_LOW_PART
11761           || (GET_CODE (dest) == SUBREG
11762               && (((GET_MODE_SIZE (GET_MODE (dest))
11763                     + UNITS_PER_WORD - 1) / UNITS_PER_WORD)
11764                   == ((GET_MODE_SIZE (GET_MODE (SUBREG_REG (dest)))
11765                        + UNITS_PER_WORD - 1) / UNITS_PER_WORD))))
11766         {
11767           move_deaths (dest, maybe_kill_insn, from_cuid, to_insn, pnotes);
11768           return;
11769         }
11770
11771       /* If this is some other SUBREG, we know it replaces the entire
11772          value, so use that as the destination.  */
11773       if (GET_CODE (dest) == SUBREG)
11774         dest = SUBREG_REG (dest);
11775
11776       /* If this is a MEM, adjust deaths of anything used in the address.
11777          For a REG (the only other possibility), the entire value is
11778          being replaced so the old value is not used in this insn.  */
11779
11780       if (MEM_P (dest))
11781         move_deaths (XEXP (dest, 0), maybe_kill_insn, from_cuid,
11782                      to_insn, pnotes);
11783       return;
11784     }
11785
11786   else if (GET_CODE (x) == CLOBBER)
11787     return;
11788
11789   len = GET_RTX_LENGTH (code);
11790   fmt = GET_RTX_FORMAT (code);
11791
11792   for (i = 0; i < len; i++)
11793     {
11794       if (fmt[i] == 'E')
11795         {
11796           int j;
11797           for (j = XVECLEN (x, i) - 1; j >= 0; j--)
11798             move_deaths (XVECEXP (x, i, j), maybe_kill_insn, from_cuid,
11799                          to_insn, pnotes);
11800         }
11801       else if (fmt[i] == 'e')
11802         move_deaths (XEXP (x, i), maybe_kill_insn, from_cuid, to_insn, pnotes);
11803     }
11804 }
11805 \f
11806 /* Return 1 if X is the target of a bit-field assignment in BODY, the
11807    pattern of an insn.  X must be a REG.  */
11808
11809 static int
11810 reg_bitfield_target_p (rtx x, rtx body)
11811 {
11812   int i;
11813
11814   if (GET_CODE (body) == SET)
11815     {
11816       rtx dest = SET_DEST (body);
11817       rtx target;
11818       unsigned int regno, tregno, endregno, endtregno;
11819
11820       if (GET_CODE (dest) == ZERO_EXTRACT)
11821         target = XEXP (dest, 0);
11822       else if (GET_CODE (dest) == STRICT_LOW_PART)
11823         target = SUBREG_REG (XEXP (dest, 0));
11824       else
11825         return 0;
11826
11827       if (GET_CODE (target) == SUBREG)
11828         target = SUBREG_REG (target);
11829
11830       if (!REG_P (target))
11831         return 0;
11832
11833       tregno = REGNO (target), regno = REGNO (x);
11834       if (tregno >= FIRST_PSEUDO_REGISTER || regno >= FIRST_PSEUDO_REGISTER)
11835         return target == x;
11836
11837       endtregno = tregno + hard_regno_nregs[tregno][GET_MODE (target)];
11838       endregno = regno + hard_regno_nregs[regno][GET_MODE (x)];
11839
11840       return endregno > tregno && regno < endtregno;
11841     }
11842
11843   else if (GET_CODE (body) == PARALLEL)
11844     for (i = XVECLEN (body, 0) - 1; i >= 0; i--)
11845       if (reg_bitfield_target_p (x, XVECEXP (body, 0, i)))
11846         return 1;
11847
11848   return 0;
11849 }
11850 \f
11851 /* Given a chain of REG_NOTES originally from FROM_INSN, try to place them
11852    as appropriate.  I3 and I2 are the insns resulting from the combination
11853    insns including FROM (I2 may be zero).
11854
11855    ELIM_I2 and ELIM_I1 are either zero or registers that we know will
11856    not need REG_DEAD notes because they are being substituted for.  This
11857    saves searching in the most common cases.
11858
11859    Each note in the list is either ignored or placed on some insns, depending
11860    on the type of note.  */
11861
11862 static void
11863 distribute_notes (rtx notes, rtx from_insn, rtx i3, rtx i2, rtx elim_i2,
11864                   rtx elim_i1)
11865 {
11866   rtx note, next_note;
11867   rtx tem;
11868
11869   for (note = notes; note; note = next_note)
11870     {
11871       rtx place = 0, place2 = 0;
11872
11873       next_note = XEXP (note, 1);
11874       switch (REG_NOTE_KIND (note))
11875         {
11876         case REG_BR_PROB:
11877         case REG_BR_PRED:
11878           /* Doesn't matter much where we put this, as long as it's somewhere.
11879              It is preferable to keep these notes on branches, which is most
11880              likely to be i3.  */
11881           place = i3;
11882           break;
11883
11884         case REG_VALUE_PROFILE:
11885           /* Just get rid of this note, as it is unused later anyway.  */
11886           break;
11887
11888         case REG_NON_LOCAL_GOTO:
11889           if (JUMP_P (i3))
11890             place = i3;
11891           else
11892             {
11893               gcc_assert (i2 && JUMP_P (i2));
11894               place = i2;
11895             }
11896           break;
11897
11898         case REG_EH_REGION:
11899           /* These notes must remain with the call or trapping instruction.  */
11900           if (CALL_P (i3))
11901             place = i3;
11902           else if (i2 && CALL_P (i2))
11903             place = i2;
11904           else
11905             {
11906               gcc_assert (flag_non_call_exceptions);
11907               if (may_trap_p (i3))
11908                 place = i3;
11909               else if (i2 && may_trap_p (i2))
11910                 place = i2;
11911               /* ??? Otherwise assume we've combined things such that we
11912                  can now prove that the instructions can't trap.  Drop the
11913                  note in this case.  */
11914             }
11915           break;
11916
11917         case REG_NORETURN:
11918         case REG_SETJMP:
11919           /* These notes must remain with the call.  It should not be
11920              possible for both I2 and I3 to be a call.  */
11921           if (CALL_P (i3))
11922             place = i3;
11923           else
11924             {
11925               gcc_assert (i2 && CALL_P (i2));
11926               place = i2;
11927             }
11928           break;
11929
11930         case REG_UNUSED:
11931           /* Any clobbers for i3 may still exist, and so we must process
11932              REG_UNUSED notes from that insn.
11933
11934              Any clobbers from i2 or i1 can only exist if they were added by
11935              recog_for_combine.  In that case, recog_for_combine created the
11936              necessary REG_UNUSED notes.  Trying to keep any original
11937              REG_UNUSED notes from these insns can cause incorrect output
11938              if it is for the same register as the original i3 dest.
11939              In that case, we will notice that the register is set in i3,
11940              and then add a REG_UNUSED note for the destination of i3, which
11941              is wrong.  However, it is possible to have REG_UNUSED notes from
11942              i2 or i1 for register which were both used and clobbered, so
11943              we keep notes from i2 or i1 if they will turn into REG_DEAD
11944              notes.  */
11945
11946           /* If this register is set or clobbered in I3, put the note there
11947              unless there is one already.  */
11948           if (reg_set_p (XEXP (note, 0), PATTERN (i3)))
11949             {
11950               if (from_insn != i3)
11951                 break;
11952
11953               if (! (REG_P (XEXP (note, 0))
11954                      ? find_regno_note (i3, REG_UNUSED, REGNO (XEXP (note, 0)))
11955                      : find_reg_note (i3, REG_UNUSED, XEXP (note, 0))))
11956                 place = i3;
11957             }
11958           /* Otherwise, if this register is used by I3, then this register
11959              now dies here, so we must put a REG_DEAD note here unless there
11960              is one already.  */
11961           else if (reg_referenced_p (XEXP (note, 0), PATTERN (i3))
11962                    && ! (REG_P (XEXP (note, 0))
11963                          ? find_regno_note (i3, REG_DEAD,
11964                                             REGNO (XEXP (note, 0)))
11965                          : find_reg_note (i3, REG_DEAD, XEXP (note, 0))))
11966             {
11967               PUT_REG_NOTE_KIND (note, REG_DEAD);
11968               place = i3;
11969             }
11970           break;
11971
11972         case REG_EQUAL:
11973         case REG_EQUIV:
11974         case REG_NOALIAS:
11975           /* These notes say something about results of an insn.  We can
11976              only support them if they used to be on I3 in which case they
11977              remain on I3.  Otherwise they are ignored.
11978
11979              If the note refers to an expression that is not a constant, we
11980              must also ignore the note since we cannot tell whether the
11981              equivalence is still true.  It might be possible to do
11982              slightly better than this (we only have a problem if I2DEST
11983              or I1DEST is present in the expression), but it doesn't
11984              seem worth the trouble.  */
11985
11986           if (from_insn == i3
11987               && (XEXP (note, 0) == 0 || CONSTANT_P (XEXP (note, 0))))
11988             place = i3;
11989           break;
11990
11991         case REG_INC:
11992         case REG_NO_CONFLICT:
11993           /* These notes say something about how a register is used.  They must
11994              be present on any use of the register in I2 or I3.  */
11995           if (reg_mentioned_p (XEXP (note, 0), PATTERN (i3)))
11996             place = i3;
11997
11998           if (i2 && reg_mentioned_p (XEXP (note, 0), PATTERN (i2)))
11999             {
12000               if (place)
12001                 place2 = i2;
12002               else
12003                 place = i2;
12004             }
12005           break;
12006
12007         case REG_LABEL:
12008           /* This can show up in several ways -- either directly in the
12009              pattern, or hidden off in the constant pool with (or without?)
12010              a REG_EQUAL note.  */
12011           /* ??? Ignore the without-reg_equal-note problem for now.  */
12012           if (reg_mentioned_p (XEXP (note, 0), PATTERN (i3))
12013               || ((tem = find_reg_note (i3, REG_EQUAL, NULL_RTX))
12014                   && GET_CODE (XEXP (tem, 0)) == LABEL_REF
12015                   && XEXP (XEXP (tem, 0), 0) == XEXP (note, 0)))
12016             place = i3;
12017
12018           if (i2
12019               && (reg_mentioned_p (XEXP (note, 0), PATTERN (i2))
12020                   || ((tem = find_reg_note (i2, REG_EQUAL, NULL_RTX))
12021                       && GET_CODE (XEXP (tem, 0)) == LABEL_REF
12022                       && XEXP (XEXP (tem, 0), 0) == XEXP (note, 0))))
12023             {
12024               if (place)
12025                 place2 = i2;
12026               else
12027                 place = i2;
12028             }
12029
12030           /* Don't attach REG_LABEL note to a JUMP_INSN.  Add
12031              a JUMP_LABEL instead or decrement LABEL_NUSES.  */
12032           if (place && JUMP_P (place))
12033             {
12034               rtx label = JUMP_LABEL (place);
12035
12036               if (!label)
12037                 JUMP_LABEL (place) = XEXP (note, 0);
12038               else
12039                 {
12040                   gcc_assert (label == XEXP (note, 0));
12041                   if (LABEL_P (label))
12042                     LABEL_NUSES (label)--;
12043                 }
12044               place = 0;
12045             }
12046           if (place2 && JUMP_P (place2))
12047             {
12048               rtx label = JUMP_LABEL (place2);
12049
12050               if (!label)
12051                 JUMP_LABEL (place2) = XEXP (note, 0);
12052               else
12053                 {
12054                   gcc_assert (label == XEXP (note, 0));
12055                   if (LABEL_P (label))
12056                     LABEL_NUSES (label)--;
12057                 }
12058               place2 = 0;
12059             }
12060           break;
12061
12062         case REG_NONNEG:
12063           /* This note says something about the value of a register prior
12064              to the execution of an insn.  It is too much trouble to see
12065              if the note is still correct in all situations.  It is better
12066              to simply delete it.  */
12067           break;
12068
12069         case REG_RETVAL:
12070           /* If the insn previously containing this note still exists,
12071              put it back where it was.  Otherwise move it to the previous
12072              insn.  Adjust the corresponding REG_LIBCALL note.  */
12073           if (!NOTE_P (from_insn))
12074             place = from_insn;
12075           else
12076             {
12077               tem = find_reg_note (XEXP (note, 0), REG_LIBCALL, NULL_RTX);
12078               place = prev_real_insn (from_insn);
12079               if (tem && place)
12080                 XEXP (tem, 0) = place;
12081               /* If we're deleting the last remaining instruction of a
12082                  libcall sequence, don't add the notes.  */
12083               else if (XEXP (note, 0) == from_insn)
12084                 tem = place = 0;
12085               /* Don't add the dangling REG_RETVAL note.  */
12086               else if (! tem)
12087                 place = 0;
12088             }
12089           break;
12090
12091         case REG_LIBCALL:
12092           /* This is handled similarly to REG_RETVAL.  */
12093           if (!NOTE_P (from_insn))
12094             place = from_insn;
12095           else
12096             {
12097               tem = find_reg_note (XEXP (note, 0), REG_RETVAL, NULL_RTX);
12098               place = next_real_insn (from_insn);
12099               if (tem && place)
12100                 XEXP (tem, 0) = place;
12101               /* If we're deleting the last remaining instruction of a
12102                  libcall sequence, don't add the notes.  */
12103               else if (XEXP (note, 0) == from_insn)
12104                 tem = place = 0;
12105               /* Don't add the dangling REG_LIBCALL note.  */
12106               else if (! tem)
12107                 place = 0;
12108             }
12109           break;
12110
12111         case REG_DEAD:
12112           /* If we replaced the right hand side of FROM_INSN with a
12113              REG_EQUAL note, the original use of the dying register
12114              will not have been combined into I3 and I2.  In such cases,
12115              FROM_INSN is guaranteed to be the first of the combined
12116              instructions, so we simply need to search back before
12117              FROM_INSN for the previous use or set of this register,
12118              then alter the notes there appropriately.
12119
12120              If the register is used as an input in I3, it dies there.
12121              Similarly for I2, if it is nonzero and adjacent to I3.
12122
12123              If the register is not used as an input in either I3 or I2
12124              and it is not one of the registers we were supposed to eliminate,
12125              there are two possibilities.  We might have a non-adjacent I2
12126              or we might have somehow eliminated an additional register
12127              from a computation.  For example, we might have had A & B where
12128              we discover that B will always be zero.  In this case we will
12129              eliminate the reference to A.
12130
12131              In both cases, we must search to see if we can find a previous
12132              use of A and put the death note there.  */
12133
12134           if (from_insn
12135               && from_insn == replaced_rhs_insn
12136               && !reg_overlap_mentioned_p (XEXP (note, 0), replaced_rhs_value))
12137             tem = from_insn;
12138           else
12139             {
12140               if (from_insn
12141                   && CALL_P (from_insn)
12142                   && find_reg_fusage (from_insn, USE, XEXP (note, 0)))
12143                 place = from_insn;
12144               else if (reg_referenced_p (XEXP (note, 0), PATTERN (i3)))
12145                 place = i3;
12146               else if (i2 != 0 && next_nonnote_insn (i2) == i3
12147                        && reg_referenced_p (XEXP (note, 0), PATTERN (i2)))
12148                 place = i2;
12149               else if (rtx_equal_p (XEXP (note, 0), elim_i2)
12150                        || rtx_equal_p (XEXP (note, 0), elim_i1))
12151                 break;
12152               tem = i3;
12153             }
12154
12155           if (place == 0)
12156             {
12157               basic_block bb = this_basic_block;
12158
12159               for (tem = PREV_INSN (tem); place == 0; tem = PREV_INSN (tem))
12160                 {
12161                   if (! INSN_P (tem))
12162                     {
12163                       if (tem == BB_HEAD (bb))
12164                         break;
12165                       continue;
12166                     }
12167
12168                   /* If TEM is a (reaching) definition of the use to which the
12169                      note was attached, see if that is all TEM is doing.  If so,
12170                      delete TEM.  Otherwise, make this into a REG_UNUSED note
12171                      instead.  Don't delete sets to global register vars.  */
12172                   if ((!from_insn
12173                        || INSN_CUID (tem) < INSN_CUID (from_insn))
12174                       && (REGNO (XEXP (note, 0)) >= FIRST_PSEUDO_REGISTER
12175                           || !global_regs[REGNO (XEXP (note, 0))])
12176                       && reg_set_p (XEXP (note, 0), PATTERN (tem)))
12177                     {
12178                       rtx set = single_set (tem);
12179                       rtx inner_dest = 0;
12180 #ifdef HAVE_cc0
12181                       rtx cc0_setter = NULL_RTX;
12182 #endif
12183
12184                       if (set != 0)
12185                         for (inner_dest = SET_DEST (set);
12186                              (GET_CODE (inner_dest) == STRICT_LOW_PART
12187                               || GET_CODE (inner_dest) == SUBREG
12188                               || GET_CODE (inner_dest) == ZERO_EXTRACT);
12189                              inner_dest = XEXP (inner_dest, 0))
12190                           ;
12191
12192                       /* Verify that it was the set, and not a clobber that
12193                          modified the register.
12194
12195                          CC0 targets must be careful to maintain setter/user
12196                          pairs.  If we cannot delete the setter due to side
12197                          effects, mark the user with an UNUSED note instead
12198                          of deleting it.  */
12199
12200                       if (set != 0 && ! side_effects_p (SET_SRC (set))
12201                           && rtx_equal_p (XEXP (note, 0), inner_dest)
12202 #ifdef HAVE_cc0
12203                           && (! reg_mentioned_p (cc0_rtx, SET_SRC (set))
12204                               || ((cc0_setter = prev_cc0_setter (tem)) != NULL
12205                                   && sets_cc0_p (PATTERN (cc0_setter)) > 0))
12206 #endif
12207                           )
12208                         {
12209                           /* Move the notes and links of TEM elsewhere.
12210                              This might delete other dead insns recursively.
12211                              First set the pattern to something that won't use
12212                              any register.  */
12213                           rtx old_notes = REG_NOTES (tem);
12214
12215                           PATTERN (tem) = pc_rtx;
12216                           REG_NOTES (tem) = NULL;
12217
12218                           distribute_notes (old_notes, tem, tem, NULL_RTX,
12219                                             NULL_RTX, NULL_RTX);
12220                           distribute_links (LOG_LINKS (tem));
12221
12222                           SET_INSN_DELETED (tem);
12223
12224 #ifdef HAVE_cc0
12225                           /* Delete the setter too.  */
12226                           if (cc0_setter)
12227                             {
12228                               PATTERN (cc0_setter) = pc_rtx;
12229                               old_notes = REG_NOTES (cc0_setter);
12230                               REG_NOTES (cc0_setter) = NULL;
12231
12232                               distribute_notes (old_notes, cc0_setter,
12233                                                 cc0_setter, NULL_RTX,
12234                                                 NULL_RTX, NULL_RTX);
12235                               distribute_links (LOG_LINKS (cc0_setter));
12236
12237                               SET_INSN_DELETED (cc0_setter);
12238                             }
12239 #endif
12240                         }
12241                       else
12242                         {
12243                           PUT_REG_NOTE_KIND (note, REG_UNUSED);
12244
12245                           /*  If there isn't already a REG_UNUSED note, put one
12246                               here.  Do not place a REG_DEAD note, even if
12247                               the register is also used here; that would not
12248                               match the algorithm used in lifetime analysis
12249                               and can cause the consistency check in the
12250                               scheduler to fail.  */
12251                           if (! find_regno_note (tem, REG_UNUSED,
12252                                                  REGNO (XEXP (note, 0))))
12253                             place = tem;
12254                           break;
12255                         }
12256                     }
12257                   else if (reg_referenced_p (XEXP (note, 0), PATTERN (tem))
12258                            || (CALL_P (tem)
12259                                && find_reg_fusage (tem, USE, XEXP (note, 0))))
12260                     {
12261                       place = tem;
12262
12263                       /* If we are doing a 3->2 combination, and we have a
12264                          register which formerly died in i3 and was not used
12265                          by i2, which now no longer dies in i3 and is used in
12266                          i2 but does not die in i2, and place is between i2
12267                          and i3, then we may need to move a link from place to
12268                          i2.  */
12269                       if (i2 && INSN_UID (place) <= max_uid_cuid
12270                           && INSN_CUID (place) > INSN_CUID (i2)
12271                           && from_insn
12272                           && INSN_CUID (from_insn) > INSN_CUID (i2)
12273                           && reg_referenced_p (XEXP (note, 0), PATTERN (i2)))
12274                         {
12275                           rtx links = LOG_LINKS (place);
12276                           LOG_LINKS (place) = 0;
12277                           distribute_links (links);
12278                         }
12279                       break;
12280                     }
12281
12282                   if (tem == BB_HEAD (bb))
12283                     break;
12284                 }
12285
12286               /* We haven't found an insn for the death note and it
12287                  is still a REG_DEAD note, but we have hit the beginning
12288                  of the block.  If the existing life info says the reg
12289                  was dead, there's nothing left to do.  Otherwise, we'll
12290                  need to do a global life update after combine.  */
12291               if (REG_NOTE_KIND (note) == REG_DEAD && place == 0
12292                   && REGNO_REG_SET_P (bb->il.rtl->global_live_at_start,
12293                                       REGNO (XEXP (note, 0))))
12294                 SET_BIT (refresh_blocks, this_basic_block->index);
12295             }
12296
12297           /* If the register is set or already dead at PLACE, we needn't do
12298              anything with this note if it is still a REG_DEAD note.
12299              We check here if it is set at all, not if is it totally replaced,
12300              which is what `dead_or_set_p' checks, so also check for it being
12301              set partially.  */
12302
12303           if (place && REG_NOTE_KIND (note) == REG_DEAD)
12304             {
12305               unsigned int regno = REGNO (XEXP (note, 0));
12306
12307               /* Similarly, if the instruction on which we want to place
12308                  the note is a noop, we'll need do a global live update
12309                  after we remove them in delete_noop_moves.  */
12310               if (noop_move_p (place))
12311                 SET_BIT (refresh_blocks, this_basic_block->index);
12312
12313               if (dead_or_set_p (place, XEXP (note, 0))
12314                   || reg_bitfield_target_p (XEXP (note, 0), PATTERN (place)))
12315                 {
12316                   /* Unless the register previously died in PLACE, clear
12317                      last_death.  [I no longer understand why this is
12318                      being done.] */
12319                   if (reg_stat[regno].last_death != place)
12320                     reg_stat[regno].last_death = 0;
12321                   place = 0;
12322                 }
12323               else
12324                 reg_stat[regno].last_death = place;
12325
12326               /* If this is a death note for a hard reg that is occupying
12327                  multiple registers, ensure that we are still using all
12328                  parts of the object.  If we find a piece of the object
12329                  that is unused, we must arrange for an appropriate REG_DEAD
12330                  note to be added for it.  However, we can't just emit a USE
12331                  and tag the note to it, since the register might actually
12332                  be dead; so we recourse, and the recursive call then finds
12333                  the previous insn that used this register.  */
12334
12335               if (place && regno < FIRST_PSEUDO_REGISTER
12336                   && hard_regno_nregs[regno][GET_MODE (XEXP (note, 0))] > 1)
12337                 {
12338                   unsigned int endregno
12339                     = regno + hard_regno_nregs[regno]
12340                                               [GET_MODE (XEXP (note, 0))];
12341                   int all_used = 1;
12342                   unsigned int i;
12343
12344                   for (i = regno; i < endregno; i++)
12345                     if ((! refers_to_regno_p (i, i + 1, PATTERN (place), 0)
12346                          && ! find_regno_fusage (place, USE, i))
12347                         || dead_or_set_regno_p (place, i))
12348                       all_used = 0;
12349
12350                   if (! all_used)
12351                     {
12352                       /* Put only REG_DEAD notes for pieces that are
12353                          not already dead or set.  */
12354
12355                       for (i = regno; i < endregno;
12356                            i += hard_regno_nregs[i][reg_raw_mode[i]])
12357                         {
12358                           rtx piece = regno_reg_rtx[i];
12359                           basic_block bb = this_basic_block;
12360
12361                           if (! dead_or_set_p (place, piece)
12362                               && ! reg_bitfield_target_p (piece,
12363                                                           PATTERN (place)))
12364                             {
12365                               rtx new_note
12366                                 = gen_rtx_EXPR_LIST (REG_DEAD, piece, NULL_RTX);
12367
12368                               distribute_notes (new_note, place, place,
12369                                                 NULL_RTX, NULL_RTX, NULL_RTX);
12370                             }
12371                           else if (! refers_to_regno_p (i, i + 1,
12372                                                         PATTERN (place), 0)
12373                                    && ! find_regno_fusage (place, USE, i))
12374                             for (tem = PREV_INSN (place); ;
12375                                  tem = PREV_INSN (tem))
12376                               {
12377                                 if (! INSN_P (tem))
12378                                   {
12379                                     if (tem == BB_HEAD (bb))
12380                                       {
12381                                         SET_BIT (refresh_blocks,
12382                                                  this_basic_block->index);
12383                                         break;
12384                                       }
12385                                     continue;
12386                                   }
12387                                 if (dead_or_set_p (tem, piece)
12388                                     || reg_bitfield_target_p (piece,
12389                                                               PATTERN (tem)))
12390                                   {
12391                                     REG_NOTES (tem)
12392                                       = gen_rtx_EXPR_LIST (REG_UNUSED, piece,
12393                                                            REG_NOTES (tem));
12394                                     break;
12395                                   }
12396                               }
12397
12398                         }
12399
12400                       place = 0;
12401                     }
12402                 }
12403             }
12404           break;
12405
12406         default:
12407           /* Any other notes should not be present at this point in the
12408              compilation.  */
12409           gcc_unreachable ();
12410         }
12411
12412       if (place)
12413         {
12414           XEXP (note, 1) = REG_NOTES (place);
12415           REG_NOTES (place) = note;
12416         }
12417       else if ((REG_NOTE_KIND (note) == REG_DEAD
12418                 || REG_NOTE_KIND (note) == REG_UNUSED)
12419                && REG_P (XEXP (note, 0)))
12420         REG_N_DEATHS (REGNO (XEXP (note, 0)))--;
12421
12422       if (place2)
12423         {
12424           if ((REG_NOTE_KIND (note) == REG_DEAD
12425                || REG_NOTE_KIND (note) == REG_UNUSED)
12426               && REG_P (XEXP (note, 0)))
12427             REG_N_DEATHS (REGNO (XEXP (note, 0)))++;
12428
12429           REG_NOTES (place2) = gen_rtx_fmt_ee (GET_CODE (note),
12430                                                REG_NOTE_KIND (note),
12431                                                XEXP (note, 0),
12432                                                REG_NOTES (place2));
12433         }
12434     }
12435 }
12436 \f
12437 /* Similarly to above, distribute the LOG_LINKS that used to be present on
12438    I3, I2, and I1 to new locations.  This is also called to add a link
12439    pointing at I3 when I3's destination is changed.  */
12440
12441 static void
12442 distribute_links (rtx links)
12443 {
12444   rtx link, next_link;
12445
12446   for (link = links; link; link = next_link)
12447     {
12448       rtx place = 0;
12449       rtx insn;
12450       rtx set, reg;
12451
12452       next_link = XEXP (link, 1);
12453
12454       /* If the insn that this link points to is a NOTE or isn't a single
12455          set, ignore it.  In the latter case, it isn't clear what we
12456          can do other than ignore the link, since we can't tell which
12457          register it was for.  Such links wouldn't be used by combine
12458          anyway.
12459
12460          It is not possible for the destination of the target of the link to
12461          have been changed by combine.  The only potential of this is if we
12462          replace I3, I2, and I1 by I3 and I2.  But in that case the
12463          destination of I2 also remains unchanged.  */
12464
12465       if (NOTE_P (XEXP (link, 0))
12466           || (set = single_set (XEXP (link, 0))) == 0)
12467         continue;
12468
12469       reg = SET_DEST (set);
12470       while (GET_CODE (reg) == SUBREG || GET_CODE (reg) == ZERO_EXTRACT
12471              || GET_CODE (reg) == STRICT_LOW_PART)
12472         reg = XEXP (reg, 0);
12473
12474       /* A LOG_LINK is defined as being placed on the first insn that uses
12475          a register and points to the insn that sets the register.  Start
12476          searching at the next insn after the target of the link and stop
12477          when we reach a set of the register or the end of the basic block.
12478
12479          Note that this correctly handles the link that used to point from
12480          I3 to I2.  Also note that not much searching is typically done here
12481          since most links don't point very far away.  */
12482
12483       for (insn = NEXT_INSN (XEXP (link, 0));
12484            (insn && (this_basic_block->next_bb == EXIT_BLOCK_PTR
12485                      || BB_HEAD (this_basic_block->next_bb) != insn));
12486            insn = NEXT_INSN (insn))
12487         if (INSN_P (insn) && reg_overlap_mentioned_p (reg, PATTERN (insn)))
12488           {
12489             if (reg_referenced_p (reg, PATTERN (insn)))
12490               place = insn;
12491             break;
12492           }
12493         else if (CALL_P (insn)
12494                  && find_reg_fusage (insn, USE, reg))
12495           {
12496             place = insn;
12497             break;
12498           }
12499         else if (INSN_P (insn) && reg_set_p (reg, insn))
12500           break;
12501
12502       /* If we found a place to put the link, place it there unless there
12503          is already a link to the same insn as LINK at that point.  */
12504
12505       if (place)
12506         {
12507           rtx link2;
12508
12509           for (link2 = LOG_LINKS (place); link2; link2 = XEXP (link2, 1))
12510             if (XEXP (link2, 0) == XEXP (link, 0))
12511               break;
12512
12513           if (link2 == 0)
12514             {
12515               XEXP (link, 1) = LOG_LINKS (place);
12516               LOG_LINKS (place) = link;
12517
12518               /* Set added_links_insn to the earliest insn we added a
12519                  link to.  */
12520               if (added_links_insn == 0
12521                   || INSN_CUID (added_links_insn) > INSN_CUID (place))
12522                 added_links_insn = place;
12523             }
12524         }
12525     }
12526 }
12527 \f
12528 /* Subroutine of unmentioned_reg_p and callback from for_each_rtx.
12529    Check whether the expression pointer to by LOC is a register or
12530    memory, and if so return 1 if it isn't mentioned in the rtx EXPR.
12531    Otherwise return zero.  */
12532
12533 static int
12534 unmentioned_reg_p_1 (rtx *loc, void *expr)
12535 {
12536   rtx x = *loc;
12537
12538   if (x != NULL_RTX
12539       && (REG_P (x) || MEM_P (x))
12540       && ! reg_mentioned_p (x, (rtx) expr))
12541     return 1;
12542   return 0;
12543 }
12544
12545 /* Check for any register or memory mentioned in EQUIV that is not
12546    mentioned in EXPR.  This is used to restrict EQUIV to "specializations"
12547    of EXPR where some registers may have been replaced by constants.  */
12548
12549 static bool
12550 unmentioned_reg_p (rtx equiv, rtx expr)
12551 {
12552   return for_each_rtx (&equiv, unmentioned_reg_p_1, expr);
12553 }
12554 \f
12555 /* Compute INSN_CUID for INSN, which is an insn made by combine.  */
12556
12557 static int
12558 insn_cuid (rtx insn)
12559 {
12560   while (insn != 0 && INSN_UID (insn) > max_uid_cuid
12561          && NONJUMP_INSN_P (insn) && GET_CODE (PATTERN (insn)) == USE)
12562     insn = NEXT_INSN (insn);
12563
12564   gcc_assert (INSN_UID (insn) <= max_uid_cuid);
12565
12566   return INSN_CUID (insn);
12567 }
12568 \f
12569 void
12570 dump_combine_stats (FILE *file)
12571 {
12572   fprintf
12573     (file,
12574      ";; Combiner statistics: %d attempts, %d substitutions (%d requiring new space),\n;; %d successes.\n\n",
12575      combine_attempts, combine_merges, combine_extras, combine_successes);
12576 }
12577
12578 void
12579 dump_combine_total_stats (FILE *file)
12580 {
12581   fprintf
12582     (file,
12583      "\n;; Combiner totals: %d attempts, %d substitutions (%d requiring new space),\n;; %d successes.\n",
12584      total_attempts, total_merges, total_extras, total_successes);
12585 }
12586 \f
12587
12588 static bool
12589 gate_handle_combine (void)
12590 {
12591   return (optimize > 0);
12592 }
12593
12594 /* Try combining insns through substitution.  */
12595 static unsigned int
12596 rest_of_handle_combine (void)
12597 {
12598   int rebuild_jump_labels_after_combine
12599     = combine_instructions (get_insns (), max_reg_num ());
12600
12601   /* Combining insns may have turned an indirect jump into a
12602      direct jump.  Rebuild the JUMP_LABEL fields of jumping
12603      instructions.  */
12604   if (rebuild_jump_labels_after_combine)
12605     {
12606       timevar_push (TV_JUMP);
12607       rebuild_jump_labels (get_insns ());
12608       timevar_pop (TV_JUMP);
12609
12610       delete_dead_jumptables ();
12611       cleanup_cfg (CLEANUP_EXPENSIVE | CLEANUP_UPDATE_LIFE);
12612     }
12613   return 0;
12614 }
12615
12616 struct tree_opt_pass pass_combine =
12617 {
12618   "combine",                            /* name */
12619   gate_handle_combine,                  /* gate */
12620   rest_of_handle_combine,               /* execute */
12621   NULL,                                 /* sub */
12622   NULL,                                 /* next */
12623   0,                                    /* static_pass_number */
12624   TV_COMBINE,                           /* tv_id */
12625   0,                                    /* properties_required */
12626   0,                                    /* properties_provided */
12627   0,                                    /* properties_destroyed */
12628   0,                                    /* todo_flags_start */
12629   TODO_dump_func |
12630   TODO_ggc_collect,                     /* todo_flags_finish */
12631   'c'                                   /* letter */
12632 };
12633