gcc/targhooks.c

   1 /* Default target hook functions.
   2    Copyright (C) 2003, 2004, 2005, 2007, 2008, 2009
   3    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 3, 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 COPYING3.  If not see
  19 <http://www.gnu.org/licenses/>.  */
  20
  21 /* The migration of target macros to target hooks works as follows:
  22
  23    1. Create a target hook that uses the existing target macros to
  24       implement the same functionality.
  25
  26    2. Convert all the MI files to use the hook instead of the macro.
  27
  28    3. Repeat for a majority of the remaining target macros.  This will
  29       take some time.
  30
  31    4. Tell target maintainers to start migrating.
  32
  33    5. Eventually convert the backends to override the hook instead of
  34       defining the macros.  This will take some time too.
  35
  36    6. TBD when, poison the macros.  Unmigrated targets will break at
  37       this point.
  38
  39    Note that we expect steps 1-3 to be done by the people that
  40    understand what the MI does with each macro, and step 5 to be done
  41    by the target maintainers for their respective targets.
  42
  43    Note that steps 1 and 2 don't have to be done together, but no
  44    target can override the new hook until step 2 is complete for it.
  45
  46    Once the macros are poisoned, we will revert to the old migration
  47    rules - migrate the macro, callers, and targets all at once.  This
  48    comment can thus be removed at that point.  */
  49
  50 #include "config.h"
  51 #include "system.h"
  52 #include "coretypes.h"
  53 #include "tm.h"
  54 #include "machmode.h"
  55 #include "rtl.h"
  56 #include "tree.h"
  57 #include "expr.h"
  58 #include "output.h"
  59 #include "toplev.h"
  60 #include "function.h"
  61 #include "target.h"
  62 #include "tm_p.h"
  63 #include "target-def.h"
  64 #include "ggc.h"
  65 #include "hard-reg-set.h"
  66 #include "reload.h"
  67 #include "optabs.h"
  68 #include "recog.h"
  69
  70
  71 bool
  72 default_legitimate_address_p (enum machine_mode mode ATTRIBUTE_UNUSED,
  73                               rtx addr ATTRIBUTE_UNUSED,
  74                               bool strict ATTRIBUTE_UNUSED)
  75 {
  76 #ifdef GO_IF_LEGITIMATE_ADDRESS
  77   /* Defer to the old implementation using a goto.  */
  78   if (strict)
  79     return strict_memory_address_p (mode, addr);
  80   else
  81     return memory_address_p (mode, addr);
  82 #else
  83   gcc_unreachable ();
  84 #endif
  85 }
  86
  87 void
  88 default_external_libcall (rtx fun ATTRIBUTE_UNUSED)
  89 {
  90 #ifdef ASM_OUTPUT_EXTERNAL_LIBCALL
  91   ASM_OUTPUT_EXTERNAL_LIBCALL(asm_out_file, fun);
  92 #endif
  93 }
  94
  95 int
  96 default_unspec_may_trap_p (const_rtx x, unsigned flags)
  97 {
  98   int i;
  99
 100   if (GET_CODE (x) == UNSPEC_VOLATILE
 101       /* Any floating arithmetic may trap.  */
 102       || (SCALAR_FLOAT_MODE_P (GET_MODE (x))
 103           && flag_trapping_math))
 104     return 1;
 105
 106   for (i = 0; i < XVECLEN (x, 0); ++i)
 107     {
 108       if (may_trap_p_1 (XVECEXP (x, 0, i), flags))
 109         return 1;
 110     }
 111
 112   return 0;
 113 }
 114
 115 enum machine_mode
 116 default_cc_modes_compatible (enum machine_mode m1, enum machine_mode m2)
 117 {
 118   if (m1 == m2)
 119     return m1;
 120   return VOIDmode;
 121 }
 122
 123 bool
 124 default_return_in_memory (const_tree type,
 125                           const_tree fntype ATTRIBUTE_UNUSED)
 126 {
 127   return (TYPE_MODE (type) == BLKmode);
 128 }
 129
 130 rtx
 131 default_legitimize_address (rtx x, rtx orig_x ATTRIBUTE_UNUSED,
 132                             enum machine_mode mode ATTRIBUTE_UNUSED)
 133 {
 134   return x;
 135 }
 136
 137 rtx
 138 default_expand_builtin_saveregs (void)
 139 {
 140   error ("__builtin_saveregs not supported by this target");
 141   return const0_rtx;
 142 }
 143
 144 void
 145 default_setup_incoming_varargs (CUMULATIVE_ARGS *ca ATTRIBUTE_UNUSED,
 146                                 enum machine_mode mode ATTRIBUTE_UNUSED,
 147                                 tree type ATTRIBUTE_UNUSED,
 148                                 int *pretend_arg_size ATTRIBUTE_UNUSED,
 149                                 int second_time ATTRIBUTE_UNUSED)
 150 {
 151 }
 152
 153 /* The default implementation of TARGET_BUILTIN_SETJMP_FRAME_VALUE.  */
 154
 155 rtx
 156 default_builtin_setjmp_frame_value (void)
 157 {
 158   return virtual_stack_vars_rtx;
 159 }
 160
 161 /* Generic hook that takes a CUMULATIVE_ARGS pointer and returns false.  */
 162
 163 bool
 164 hook_bool_CUMULATIVE_ARGS_false (CUMULATIVE_ARGS *ca ATTRIBUTE_UNUSED)
 165 {
 166   return false;
 167 }
 168
 169 bool
 170 default_pretend_outgoing_varargs_named (CUMULATIVE_ARGS *ca ATTRIBUTE_UNUSED)
 171 {
 172   return (targetm.calls.setup_incoming_varargs
 173           != default_setup_incoming_varargs);
 174 }
 175
 176 enum machine_mode
 177 default_eh_return_filter_mode (void)
 178 {
 179   return targetm.unwind_word_mode ();
 180 }
 181
 182 enum machine_mode
 183 default_libgcc_cmp_return_mode (void)
 184 {
 185   return word_mode;
 186 }
 187
 188 enum machine_mode
 189 default_libgcc_shift_count_mode (void)
 190 {
 191   return word_mode;
 192 }
 193
 194 enum machine_mode
 195 default_unwind_word_mode (void)
 196 {
 197   return word_mode;
 198 }
 199
 200 /* The default implementation of TARGET_SHIFT_TRUNCATION_MASK.  */
 201
 202 unsigned HOST_WIDE_INT
 203 default_shift_truncation_mask (enum machine_mode mode)
 204 {
 205   return SHIFT_COUNT_TRUNCATED ? GET_MODE_BITSIZE (mode) - 1 : 0;
 206 }
 207
 208 /* The default implementation of TARGET_MIN_DIVISIONS_FOR_RECIP_MUL.  */
 209
 210 unsigned int
 211 default_min_divisions_for_recip_mul (enum machine_mode mode ATTRIBUTE_UNUSED)
 212 {
 213   return have_insn_for (DIV, mode) ? 3 : 2;
 214 }
 215
 216 /* The default implementation of TARGET_MODE_REP_EXTENDED.  */
 217
 218 int
 219 default_mode_rep_extended (enum machine_mode mode ATTRIBUTE_UNUSED,
 220                            enum machine_mode mode_rep ATTRIBUTE_UNUSED)
 221 {
 222   return UNKNOWN;
 223 }
 224
 225 /* Generic hook that takes a CUMULATIVE_ARGS pointer and returns true.  */
 226
 227 bool
 228 hook_bool_CUMULATIVE_ARGS_true (CUMULATIVE_ARGS * a ATTRIBUTE_UNUSED)
 229 {
 230   return true;
 231 }
 232
 233 /* Return machine mode for non-standard suffix
 234    or VOIDmode if non-standard suffixes are unsupported.  */
 235 enum machine_mode
 236 default_mode_for_suffix (char suffix ATTRIBUTE_UNUSED)
 237 {
 238   return VOIDmode;
 239 }
 240
 241 /* The generic C++ ABI specifies this is a 64-bit value.  */
 242 tree
 243 default_cxx_guard_type (void)
 244 {
 245   return long_long_integer_type_node;
 246 }
 247
 248
 249 /* Returns the size of the cookie to use when allocating an array
 250    whose elements have the indicated TYPE.  Assumes that it is already
 251    known that a cookie is needed.  */
 252
 253 tree
 254 default_cxx_get_cookie_size (tree type)
 255 {
 256   tree cookie_size;
 257
 258   /* We need to allocate an additional max (sizeof (size_t), alignof
 259      (true_type)) bytes.  */
 260   tree sizetype_size;
 261   tree type_align;
 262
 263   sizetype_size = size_in_bytes (sizetype);
 264   type_align = size_int (TYPE_ALIGN_UNIT (type));
 265   if (INT_CST_LT_UNSIGNED (type_align, sizetype_size))
 266     cookie_size = sizetype_size;
 267   else
 268     cookie_size = type_align;
 269
 270   return cookie_size;
 271 }
 272
 273 /* Return true if a parameter must be passed by reference.  This version
 274    of the TARGET_PASS_BY_REFERENCE hook uses just MUST_PASS_IN_STACK.  */
 275
 276 bool
 277 hook_pass_by_reference_must_pass_in_stack (CUMULATIVE_ARGS *c ATTRIBUTE_UNUSED,
 278         enum machine_mode mode ATTRIBUTE_UNUSED, const_tree type ATTRIBUTE_UNUSED,
 279         bool named_arg ATTRIBUTE_UNUSED)
 280 {
 281   return targetm.calls.must_pass_in_stack (mode, type);
 282 }
 283
 284 /* Return true if a parameter follows callee copies conventions.  This
 285    version of the hook is true for all named arguments.  */
 286
 287 bool
 288 hook_callee_copies_named (CUMULATIVE_ARGS *ca ATTRIBUTE_UNUSED,
 289                           enum machine_mode mode ATTRIBUTE_UNUSED,
 290                           const_tree type ATTRIBUTE_UNUSED, bool named)
 291 {
 292   return named;
 293 }
 294
 295 /* Emit any directives required to unwind this instruction.  */
 296
 297 void
 298 default_unwind_emit (FILE * stream ATTRIBUTE_UNUSED,
 299                      rtx insn ATTRIBUTE_UNUSED)
 300 {
 301   /* Should never happen.  */
 302   gcc_unreachable ();
 303 }
 304
 305 /* True if MODE is valid for the target.  By "valid", we mean able to
 306    be manipulated in non-trivial ways.  In particular, this means all
 307    the arithmetic is supported.
 308
 309    By default we guess this means that any C type is supported.  If
 310    we can't map the mode back to a type that would be available in C,
 311    then reject it.  Special case, here, is the double-word arithmetic
 312    supported by optabs.c.  */
 313
 314 bool
 315 default_scalar_mode_supported_p (enum machine_mode mode)
 316 {
 317   int precision = GET_MODE_PRECISION (mode);
 318
 319   switch (GET_MODE_CLASS (mode))
 320     {
 321     case MODE_PARTIAL_INT:
 322     case MODE_INT:
 323       if (precision == CHAR_TYPE_SIZE)
 324         return true;
 325       if (precision == SHORT_TYPE_SIZE)
 326         return true;
 327       if (precision == INT_TYPE_SIZE)
 328         return true;
 329       if (precision == LONG_TYPE_SIZE)
 330         return true;
 331       if (precision == LONG_LONG_TYPE_SIZE)
 332         return true;
 333       if (precision == 2 * BITS_PER_WORD)
 334         return true;
 335       return false;
 336
 337     case MODE_FLOAT:
 338       if (precision == FLOAT_TYPE_SIZE)
 339         return true;
 340       if (precision == DOUBLE_TYPE_SIZE)
 341         return true;
 342       if (precision == LONG_DOUBLE_TYPE_SIZE)
 343         return true;
 344       return false;
 345
 346     case MODE_DECIMAL_FLOAT:
 347     case MODE_FRACT:
 348     case MODE_UFRACT:
 349     case MODE_ACCUM:
 350     case MODE_UACCUM:
 351       return false;
 352
 353     default:
 354       gcc_unreachable ();
 355     }
 356 }
 357
 358 /* True if the target supports decimal floating point.  */
 359
 360 bool
 361 default_decimal_float_supported_p (void)
 362 {
 363   return ENABLE_DECIMAL_FLOAT;
 364 }
 365
 366 /* True if the target supports fixed-point arithmetic.  */
 367
 368 bool
 369 default_fixed_point_supported_p (void)
 370 {
 371   return ENABLE_FIXED_POINT;
 372 }
 373
 374 /* NULL if INSN insn is valid within a low-overhead loop, otherwise returns
 375    an error message.
 376
 377    This function checks whether a given INSN is valid within a low-overhead
 378    loop.  If INSN is invalid it returns the reason for that, otherwise it
 379    returns NULL. A called function may clobber any special registers required
 380    for low-overhead looping. Additionally, some targets (eg, PPC) use the count
 381    register for branch on table instructions. We reject the doloop pattern in
 382    these cases.  */
 383
 384 const char *
 385 default_invalid_within_doloop (const_rtx insn)
 386 {
 387   if (CALL_P (insn))
 388     return "Function call in loop.";
 389
 390   if (JUMP_P (insn)
 391       && (GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC
 392           || GET_CODE (PATTERN (insn)) == ADDR_VEC))
 393     return "Computed branch in the loop.";
 394
 395   return NULL;
 396 }
 397
 398 /* Mapping of builtin functions to vectorized variants.  */
 399
 400 tree
 401 default_builtin_vectorized_function (unsigned int fn ATTRIBUTE_UNUSED,
 402                                      tree type_out ATTRIBUTE_UNUSED,
 403                                      tree type_in ATTRIBUTE_UNUSED)
 404 {
 405   return NULL_TREE;
 406 }
 407
 408 /* Vectorized conversion.  */
 409
 410 tree
 411 default_builtin_vectorized_conversion (unsigned int code ATTRIBUTE_UNUSED,
 412                                        tree type ATTRIBUTE_UNUSED)
 413 {
 414   return NULL_TREE;
 415 }
 416
 417 /* Reciprocal.  */
 418
 419 tree
 420 default_builtin_reciprocal (unsigned int fn ATTRIBUTE_UNUSED,
 421                             bool md_fn ATTRIBUTE_UNUSED,
 422                             bool sqrt ATTRIBUTE_UNUSED)
 423 {
 424   return NULL_TREE;
 425 }
 426
 427 bool
 428 hook_bool_CUMULATIVE_ARGS_mode_tree_bool_false (
 429         CUMULATIVE_ARGS *ca ATTRIBUTE_UNUSED,
 430         enum machine_mode mode ATTRIBUTE_UNUSED,
 431         const_tree type ATTRIBUTE_UNUSED, bool named ATTRIBUTE_UNUSED)
 432 {
 433   return false;
 434 }
 435
 436 bool
 437 hook_bool_CUMULATIVE_ARGS_mode_tree_bool_true (
 438         CUMULATIVE_ARGS *ca ATTRIBUTE_UNUSED,
 439         enum machine_mode mode ATTRIBUTE_UNUSED,
 440         const_tree type ATTRIBUTE_UNUSED, bool named ATTRIBUTE_UNUSED)
 441 {
 442   return true;
 443 }
 444
 445 int
 446 hook_int_CUMULATIVE_ARGS_mode_tree_bool_0 (
 447         CUMULATIVE_ARGS *ca ATTRIBUTE_UNUSED,
 448         enum machine_mode mode ATTRIBUTE_UNUSED,
 449         tree type ATTRIBUTE_UNUSED, bool named ATTRIBUTE_UNUSED)
 450 {
 451   return 0;
 452 }
 453
 454 void
 455 hook_void_bitmap (bitmap regs ATTRIBUTE_UNUSED)
 456 {
 457 }
 458
 459 const char *
 460 hook_invalid_arg_for_unprototyped_fn (
 461         const_tree typelist ATTRIBUTE_UNUSED,
 462         const_tree funcdecl ATTRIBUTE_UNUSED,
 463         const_tree val ATTRIBUTE_UNUSED)
 464 {
 465   return NULL;
 466 }
 467
 468 /* Initialize the stack protection decls.  */
 469
 470 /* Stack protection related decls living in libgcc.  */
 471 static GTY(()) tree stack_chk_guard_decl;
 472
 473 tree
 474 default_stack_protect_guard (void)
 475 {
 476   tree t = stack_chk_guard_decl;
 477
 478   if (t == NULL)
 479     {
 480       t = build_decl (UNKNOWN_LOCATION,
 481                       VAR_DECL, get_identifier ("__stack_chk_guard"),
 482                       ptr_type_node);
 483       TREE_STATIC (t) = 1;
 484       TREE_PUBLIC (t) = 1;
 485       DECL_EXTERNAL (t) = 1;
 486       TREE_USED (t) = 1;
 487       TREE_THIS_VOLATILE (t) = 1;
 488       DECL_ARTIFICIAL (t) = 1;
 489       DECL_IGNORED_P (t) = 1;
 490
 491       stack_chk_guard_decl = t;
 492     }
 493
 494   return t;
 495 }
 496
 497 static GTY(()) tree stack_chk_fail_decl;
 498
 499 tree
 500 default_external_stack_protect_fail (void)
 501 {
 502   tree t = stack_chk_fail_decl;
 503
 504   if (t == NULL_TREE)
 505     {
 506       t = build_function_type_list (void_type_node, NULL_TREE);
 507       t = build_decl (UNKNOWN_LOCATION,
 508                       FUNCTION_DECL, get_identifier ("__stack_chk_fail"), t);
 509       TREE_STATIC (t) = 1;
 510       TREE_PUBLIC (t) = 1;
 511       DECL_EXTERNAL (t) = 1;
 512       TREE_USED (t) = 1;
 513       TREE_THIS_VOLATILE (t) = 1;
 514       TREE_NOTHROW (t) = 1;
 515       DECL_ARTIFICIAL (t) = 1;
 516       DECL_IGNORED_P (t) = 1;
 517       DECL_VISIBILITY (t) = VISIBILITY_DEFAULT;
 518       DECL_VISIBILITY_SPECIFIED (t) = 1;
 519
 520       stack_chk_fail_decl = t;
 521     }
 522
 523   return build_call_expr (t, 0);
 524 }
 525
 526 tree
 527 default_hidden_stack_protect_fail (void)
 528 {
 529 #ifndef HAVE_GAS_HIDDEN
 530   return default_external_stack_protect_fail ();
 531 #else
 532   tree t = stack_chk_fail_decl;
 533
 534   if (!flag_pic)
 535     return default_external_stack_protect_fail ();
 536
 537   if (t == NULL_TREE)
 538     {
 539       t = build_function_type_list (void_type_node, NULL_TREE);
 540       t = build_decl (UNKNOWN_LOCATION, FUNCTION_DECL,
 541                       get_identifier ("__stack_chk_fail_local"), t);
 542       TREE_STATIC (t) = 1;
 543       TREE_PUBLIC (t) = 1;
 544       DECL_EXTERNAL (t) = 1;
 545       TREE_USED (t) = 1;
 546       TREE_THIS_VOLATILE (t) = 1;
 547       TREE_NOTHROW (t) = 1;
 548       DECL_ARTIFICIAL (t) = 1;
 549       DECL_IGNORED_P (t) = 1;
 550       DECL_VISIBILITY_SPECIFIED (t) = 1;
 551       DECL_VISIBILITY (t) = VISIBILITY_HIDDEN;
 552
 553       stack_chk_fail_decl = t;
 554     }
 555
 556   return build_call_expr (t, 0);
 557 #endif
 558 }
 559
 560 bool
 561 hook_bool_const_rtx_commutative_p (const_rtx x,
 562                                    int outer_code ATTRIBUTE_UNUSED)
 563 {
 564   return COMMUTATIVE_P (x);
 565 }
 566
 567 rtx
 568 default_function_value (const_tree ret_type ATTRIBUTE_UNUSED,
 569                         const_tree fn_decl_or_type,
 570                         bool outgoing ATTRIBUTE_UNUSED)
 571 {
 572   /* The old interface doesn't handle receiving the function type.  */
 573   if (fn_decl_or_type
 574       && !DECL_P (fn_decl_or_type))
 575     fn_decl_or_type = NULL;
 576
 577 #ifdef FUNCTION_OUTGOING_VALUE
 578   if (outgoing)
 579     return FUNCTION_OUTGOING_VALUE (ret_type, fn_decl_or_type);
 580 #endif
 581
 582 #ifdef FUNCTION_VALUE
 583   return FUNCTION_VALUE (ret_type, fn_decl_or_type);
 584 #else
 585   return NULL_RTX;
 586 #endif
 587 }
 588
 589 rtx
 590 default_internal_arg_pointer (void)
 591 {
 592   /* If the reg that the virtual arg pointer will be translated into is
 593      not a fixed reg or is the stack pointer, make a copy of the virtual
 594      arg pointer, and address parms via the copy.  The frame pointer is
 595      considered fixed even though it is not marked as such.  */
 596   if ((ARG_POINTER_REGNUM == STACK_POINTER_REGNUM
 597        || ! (fixed_regs[ARG_POINTER_REGNUM]
 598              || ARG_POINTER_REGNUM == FRAME_POINTER_REGNUM)))
 599     return copy_to_reg (virtual_incoming_args_rtx);
 600   else
 601     return virtual_incoming_args_rtx;
 602 }
 603
 604 enum reg_class
 605 default_branch_target_register_class (void)
 606 {
 607   return NO_REGS;
 608 }
 609
 610 #ifdef IRA_COVER_CLASSES
 611 const enum reg_class *
 612 default_ira_cover_classes (void)
 613 {
 614   static enum reg_class classes[] = IRA_COVER_CLASSES;
 615   return classes;
 616 }
 617 #endif
 618
 619 enum reg_class
 620 default_secondary_reload (bool in_p ATTRIBUTE_UNUSED, rtx x ATTRIBUTE_UNUSED,
 621                           enum reg_class reload_class ATTRIBUTE_UNUSED,
 622                           enum machine_mode reload_mode ATTRIBUTE_UNUSED,
 623                           secondary_reload_info *sri)
 624 {
 625   enum reg_class rclass = NO_REGS;
 626
 627   if (sri->prev_sri && sri->prev_sri->t_icode != CODE_FOR_nothing)
 628     {
 629       sri->icode = sri->prev_sri->t_icode;
 630       return NO_REGS;
 631     }
 632 #ifdef SECONDARY_INPUT_RELOAD_CLASS
 633   if (in_p)
 634     rclass = SECONDARY_INPUT_RELOAD_CLASS (reload_class, reload_mode, x);
 635 #endif
 636 #ifdef SECONDARY_OUTPUT_RELOAD_CLASS
 637   if (! in_p)
 638     rclass = SECONDARY_OUTPUT_RELOAD_CLASS (reload_class, reload_mode, x);
 639 #endif
 640   if (rclass != NO_REGS)
 641     {
 642       enum insn_code icode = (in_p ? reload_in_optab[(int) reload_mode]
 643                               : reload_out_optab[(int) reload_mode]);
 644
 645       if (icode != CODE_FOR_nothing
 646           && insn_data[(int) icode].operand[in_p].predicate
 647           && ! insn_data[(int) icode].operand[in_p].predicate (x, reload_mode))
 648         icode = CODE_FOR_nothing;
 649       else if (icode != CODE_FOR_nothing)
 650         {
 651           const char *insn_constraint, *scratch_constraint;
 652           char insn_letter, scratch_letter;
 653           enum reg_class insn_class, scratch_class;
 654
 655           gcc_assert (insn_data[(int) icode].n_operands == 3);
 656           insn_constraint = insn_data[(int) icode].operand[!in_p].constraint;
 657           if (!*insn_constraint)
 658             insn_class = ALL_REGS;
 659           else
 660             {
 661               if (in_p)
 662                 {
 663                   gcc_assert (*insn_constraint == '=');
 664                   insn_constraint++;
 665                 }
 666               insn_letter = *insn_constraint;
 667               insn_class
 668                 = (insn_letter == 'r' ? GENERAL_REGS
 669                    : REG_CLASS_FROM_CONSTRAINT ((unsigned char) insn_letter,
 670                                                 insn_constraint));
 671               gcc_assert (insn_class != NO_REGS);
 672             }
 673
 674           scratch_constraint = insn_data[(int) icode].operand[2].constraint;
 675           /* The scratch register's constraint must start with "=&",
 676              except for an input reload, where only "=" is necessary,
 677              and where it might be beneficial to re-use registers from
 678              the input.  */
 679           gcc_assert (scratch_constraint[0] == '='
 680                       && (in_p || scratch_constraint[1] == '&'));
 681           scratch_constraint++;
 682           if (*scratch_constraint == '&')
 683             scratch_constraint++;
 684           scratch_letter = *scratch_constraint;
 685           scratch_class
 686             = (scratch_letter == 'r' ? GENERAL_REGS
 687                : REG_CLASS_FROM_CONSTRAINT ((unsigned char) scratch_letter,
 688                                             scratch_constraint));
 689
 690           if (reg_class_subset_p (reload_class, insn_class))
 691             {
 692               gcc_assert (scratch_class == rclass);
 693               rclass = NO_REGS;
 694             }
 695           else
 696             rclass = insn_class;
 697
 698         }
 699       if (rclass == NO_REGS)
 700         sri->icode = icode;
 701       else
 702         sri->t_icode = icode;
 703     }
 704   return rclass;
 705 }
 706
 707 bool
 708 default_handle_c_option (size_t code ATTRIBUTE_UNUSED,
 709                          const char *arg ATTRIBUTE_UNUSED,
 710                          int value ATTRIBUTE_UNUSED)
 711 {
 712   return false;
 713 }
 714
 715 /* By default, if flag_pic is true, then neither local nor global relocs
 716    should be placed in readonly memory.  */
 717
 718 int
 719 default_reloc_rw_mask (void)
 720 {
 721   return flag_pic ? 3 : 0;
 722 }
 723
 724 /* By default, do no modification. */
 725 tree default_mangle_decl_assembler_name (tree decl ATTRIBUTE_UNUSED,
 726                                          tree id)
 727 {
 728    return id;
 729 }
 730
 731 bool
 732 default_builtin_vector_alignment_reachable (const_tree type, bool is_packed)
 733 {
 734   if (is_packed)
 735     return false;
 736
 737   /* Assuming that types whose size is > pointer-size are not guaranteed to be
 738      naturally aligned.  */
 739   if (tree_int_cst_compare (TYPE_SIZE (type), bitsize_int (POINTER_SIZE)) > 0)
 740     return false;
 741
 742   /* Assuming that types whose size is <= pointer-size
 743      are naturally aligned.  */
 744   return true;
 745 }
 746
 747 bool
 748 default_hard_regno_scratch_ok (unsigned int regno ATTRIBUTE_UNUSED)
 749 {
 750   return true;
 751 }
 752
 753 bool
 754 default_target_option_valid_attribute_p (tree ARG_UNUSED (fndecl),
 755                                          tree ARG_UNUSED (name),
 756                                          tree ARG_UNUSED (args),
 757                                          int ARG_UNUSED (flags))
 758 {
 759   warning (OPT_Wattributes,
 760            "target attribute is not supported on this machine");
 761
 762   return false;
 763 }
 764
 765 bool
 766 default_target_option_pragma_parse (tree ARG_UNUSED (args),
 767                                     tree ARG_UNUSED (pop_target))
 768 {
 769   warning (OPT_Wpragmas,
 770            "#pragma GCC target is not supported for this machine");
 771
 772   return false;
 773 }
 774
 775 bool
 776 default_target_option_can_inline_p (tree caller, tree callee)
 777 {
 778   bool ret = false;
 779   tree callee_opts = DECL_FUNCTION_SPECIFIC_TARGET (callee);
 780   tree caller_opts = DECL_FUNCTION_SPECIFIC_TARGET (caller);
 781
 782   /* If callee has no option attributes, then it is ok to inline */
 783   if (!callee_opts)
 784     ret = true;
 785
 786   /* If caller has no option attributes, but callee does then it is not ok to
 787      inline */
 788   else if (!caller_opts)
 789     ret = false;
 790
 791   /* If both caller and callee have attributes, assume that if the pointer is
 792      different, the the two functions have different target options since
 793      build_target_option_node uses a hash table for the options.  */
 794   else
 795     ret = (callee_opts == caller_opts);
 796
 797   return ret;
 798 }
 799
 800 #ifndef HAVE_casesi
 801 # define HAVE_casesi 0
 802 #endif
 803
 804 /* If the machine does not have a case insn that compares the bounds,
 805    this means extra overhead for dispatch tables, which raises the
 806    threshold for using them.  */
 807
 808 unsigned int default_case_values_threshold (void)
 809 {
 810   return (HAVE_casesi ? 4 : 5);
 811 }
 812
 813 #include "gt-targhooks.h"