gcc/mode-switching.c

   1 /* CPU mode switching
   2    Copyright (C) 1998-2013 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20 #include "config.h"
  21 #include "system.h"
  22 #include "coretypes.h"
  23 #include "tm.h"
  24 #include "target.h"
  25 #include "rtl.h"
  26 #include "regs.h"
  27 #include "hard-reg-set.h"
  28 #include "flags.h"
  29 #include "insn-config.h"
  30 #include "recog.h"
  31 #include "basic-block.h"
  32 #include "tm_p.h"
  33 #include "function.h"
  34 #include "tree-pass.h"
  35 #include "df.h"
  36 #include "emit-rtl.h"
  37
  38 /* We want target macros for the mode switching code to be able to refer
  39    to instruction attribute values.  */
  40 #include "insn-attr.h"
  41
  42 #ifdef OPTIMIZE_MODE_SWITCHING
  43
  44 /* The algorithm for setting the modes consists of scanning the insn list
  45    and finding all the insns which require a specific mode.  Each insn gets
  46    a unique struct seginfo element.  These structures are inserted into a list
  47    for each basic block.  For each entity, there is an array of bb_info over
  48    the flow graph basic blocks (local var 'bb_info'), and contains a list
  49    of all insns within that basic block, in the order they are encountered.
  50
  51    For each entity, any basic block WITHOUT any insns requiring a specific
  52    mode are given a single entry, without a mode.  (Each basic block
  53    in the flow graph must have at least one entry in the segment table.)
  54
  55    The LCM algorithm is then run over the flow graph to determine where to
  56    place the sets to the highest-priority value in respect of first the first
  57    insn in any one block.  Any adjustments required to the transparency
  58    vectors are made, then the next iteration starts for the next-lower
  59    priority mode, till for each entity all modes are exhausted.
  60
  61    More details are located in the code for optimize_mode_switching().  */
  62 \f
  63 /* This structure contains the information for each insn which requires
  64    either single or double mode to be set.
  65    MODE is the mode this insn must be executed in.
  66    INSN_PTR is the insn to be executed (may be the note that marks the
  67    beginning of a basic block).
  68    BBNUM is the flow graph basic block this insn occurs in.
  69    NEXT is the next insn in the same basic block.  */
  70 struct seginfo
  71 {
  72   int mode;
  73   rtx insn_ptr;
  74   int bbnum;
  75   struct seginfo *next;
  76   HARD_REG_SET regs_live;
  77 };
  78
  79 struct bb_info
  80 {
  81   struct seginfo *seginfo;
  82   int computing;
  83 };
  84
  85 /* These bitmaps are used for the LCM algorithm.  */
  86
  87 static sbitmap *antic;
  88 static sbitmap *transp;
  89 static sbitmap *comp;
  90
  91 static struct seginfo * new_seginfo (int, rtx, int, HARD_REG_SET);
  92 static void add_seginfo (struct bb_info *, struct seginfo *);
  93 static void reg_dies (rtx, HARD_REG_SET *);
  94 static void reg_becomes_live (rtx, const_rtx, void *);
  95 static void make_preds_opaque (basic_block, int);
  96 \f
  97
  98 /* This function will allocate a new BBINFO structure, initialized
  99    with the MODE, INSN, and basic block BB parameters.  */
 100
 101 static struct seginfo *
 102 new_seginfo (int mode, rtx insn, int bb, HARD_REG_SET regs_live)
 103 {
 104   struct seginfo *ptr;
 105   ptr = XNEW (struct seginfo);
 106   ptr->mode = mode;
 107   ptr->insn_ptr = insn;
 108   ptr->bbnum = bb;
 109   ptr->next = NULL;
 110   COPY_HARD_REG_SET (ptr->regs_live, regs_live);
 111   return ptr;
 112 }
 113
 114 /* Add a seginfo element to the end of a list.
 115    HEAD is a pointer to the list beginning.
 116    INFO is the structure to be linked in.  */
 117
 118 static void
 119 add_seginfo (struct bb_info *head, struct seginfo *info)
 120 {
 121   struct seginfo *ptr;
 122
 123   if (head->seginfo == NULL)
 124     head->seginfo = info;
 125   else
 126     {
 127       ptr = head->seginfo;
 128       while (ptr->next != NULL)
 129         ptr = ptr->next;
 130       ptr->next = info;
 131     }
 132 }
 133
 134 /* Make all predecessors of basic block B opaque, recursively, till we hit
 135    some that are already non-transparent, or an edge where aux is set; that
 136    denotes that a mode set is to be done on that edge.
 137    J is the bit number in the bitmaps that corresponds to the entity that
 138    we are currently handling mode-switching for.  */
 139
 140 static void
 141 make_preds_opaque (basic_block b, int j)
 142 {
 143   edge e;
 144   edge_iterator ei;
 145
 146   FOR_EACH_EDGE (e, ei, b->preds)
 147     {
 148       basic_block pb = e->src;
 149
 150       if (e->aux || ! bitmap_bit_p (transp[pb->index], j))
 151         continue;
 152
 153       bitmap_clear_bit (transp[pb->index], j);
 154       make_preds_opaque (pb, j);
 155     }
 156 }
 157
 158 /* Record in LIVE that register REG died.  */
 159
 160 static void
 161 reg_dies (rtx reg, HARD_REG_SET *live)
 162 {
 163   int regno;
 164
 165   if (!REG_P (reg))
 166     return;
 167
 168   regno = REGNO (reg);
 169   if (regno < FIRST_PSEUDO_REGISTER)
 170     remove_from_hard_reg_set (live, GET_MODE (reg), regno);
 171 }
 172
 173 /* Record in LIVE that register REG became live.
 174    This is called via note_stores.  */
 175
 176 static void
 177 reg_becomes_live (rtx reg, const_rtx setter ATTRIBUTE_UNUSED, void *live)
 178 {
 179   int regno;
 180
 181   if (GET_CODE (reg) == SUBREG)
 182     reg = SUBREG_REG (reg);
 183
 184   if (!REG_P (reg))
 185     return;
 186
 187   regno = REGNO (reg);
 188   if (regno < FIRST_PSEUDO_REGISTER)
 189     add_to_hard_reg_set ((HARD_REG_SET *) live, GET_MODE (reg), regno);
 190 }
 191
 192 /* Make sure if MODE_ENTRY is defined the MODE_EXIT is defined
 193    and vice versa.  */
 194 #if defined (MODE_ENTRY) != defined (MODE_EXIT)
 195  #error "Both MODE_ENTRY and MODE_EXIT must be defined"
 196 #endif
 197
 198 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 199 /* Split the fallthrough edge to the exit block, so that we can note
 200    that there NORMAL_MODE is required.  Return the new block if it's
 201    inserted before the exit block.  Otherwise return null.  */
 202
 203 static basic_block
 204 create_pre_exit (int n_entities, int *entity_map, const int *num_modes)
 205 {
 206   edge eg;
 207   edge_iterator ei;
 208   basic_block pre_exit;
 209
 210   /* The only non-call predecessor at this stage is a block with a
 211      fallthrough edge; there can be at most one, but there could be
 212      none at all, e.g. when exit is called.  */
 213   pre_exit = 0;
 214   FOR_EACH_EDGE (eg, ei, EXIT_BLOCK_PTR->preds)
 215     if (eg->flags & EDGE_FALLTHRU)
 216       {
 217         basic_block src_bb = eg->src;
 218         rtx last_insn, ret_reg;
 219
 220         gcc_assert (!pre_exit);
 221         /* If this function returns a value at the end, we have to
 222            insert the final mode switch before the return value copy
 223            to its hard register.  */
 224         if (EDGE_COUNT (EXIT_BLOCK_PTR->preds) == 1
 225             && NONJUMP_INSN_P ((last_insn = BB_END (src_bb)))
 226             && GET_CODE (PATTERN (last_insn)) == USE
 227             && GET_CODE ((ret_reg = XEXP (PATTERN (last_insn), 0))) == REG)
 228           {
 229             int ret_start = REGNO (ret_reg);
 230             int nregs = hard_regno_nregs[ret_start][GET_MODE (ret_reg)];
 231             int ret_end = ret_start + nregs;
 232             int short_block = 0;
 233             int maybe_builtin_apply = 0;
 234             int forced_late_switch = 0;
 235             rtx before_return_copy;
 236
 237             do
 238               {
 239                 rtx return_copy = PREV_INSN (last_insn);
 240                 rtx return_copy_pat, copy_reg;
 241                 int copy_start, copy_num;
 242                 int j;
 243
 244                 if (NONDEBUG_INSN_P (return_copy))
 245                   {
 246                     /* When using SJLJ exceptions, the call to the
 247                        unregister function is inserted between the
 248                        clobber of the return value and the copy.
 249                        We do not want to split the block before this
 250                        or any other call; if we have not found the
 251                        copy yet, the copy must have been deleted.  */
 252                     if (CALL_P (return_copy))
 253                       {
 254                         short_block = 1;
 255                         break;
 256                       }
 257                     return_copy_pat = PATTERN (return_copy);
 258                     switch (GET_CODE (return_copy_pat))
 259                       {
 260                       case USE:
 261                         /* Skip __builtin_apply pattern.  */
 262                         if (GET_CODE (XEXP (return_copy_pat, 0)) == REG
 263                             && (targetm.calls.function_value_regno_p
 264                                 (REGNO (XEXP (return_copy_pat, 0)))))
 265                           {
 266                             maybe_builtin_apply = 1;
 267                             last_insn = return_copy;
 268                             continue;
 269                           }
 270                         break;
 271
 272                       case ASM_OPERANDS:
 273                         /* Skip barrier insns.  */
 274                         if (!MEM_VOLATILE_P (return_copy_pat))
 275                           break;
 276
 277                         /* Fall through.  */
 278
 279                       case ASM_INPUT:
 280                       case UNSPEC_VOLATILE:
 281                         last_insn = return_copy;
 282                         continue;
 283
 284                       default:
 285                         break;
 286                       }
 287
 288                     /* If the return register is not (in its entirety)
 289                        likely spilled, the return copy might be
 290                        partially or completely optimized away.  */
 291                     return_copy_pat = single_set (return_copy);
 292                     if (!return_copy_pat)
 293                       {
 294                         return_copy_pat = PATTERN (return_copy);
 295                         if (GET_CODE (return_copy_pat) != CLOBBER)
 296                           break;
 297                         else if (!optimize)
 298                           {
 299                             /* This might be (clobber (reg [<result>]))
 300                                when not optimizing.  Then check if
 301                                the previous insn is the clobber for
 302                                the return register.  */
 303                             copy_reg = SET_DEST (return_copy_pat);
 304                             if (GET_CODE (copy_reg) == REG
 305                                 && !HARD_REGISTER_NUM_P (REGNO (copy_reg)))
 306                               {
 307                                 if (INSN_P (PREV_INSN (return_copy)))
 308                                   {
 309                                     return_copy = PREV_INSN (return_copy);
 310                                     return_copy_pat = PATTERN (return_copy);
 311                                     if (GET_CODE (return_copy_pat) != CLOBBER)
 312                                       break;
 313                                   }
 314                               }
 315                           }
 316                       }
 317                     copy_reg = SET_DEST (return_copy_pat);
 318                     if (GET_CODE (copy_reg) == REG)
 319                       copy_start = REGNO (copy_reg);
 320                     else if (GET_CODE (copy_reg) == SUBREG
 321                              && GET_CODE (SUBREG_REG (copy_reg)) == REG)
 322                       copy_start = REGNO (SUBREG_REG (copy_reg));
 323                     else
 324                       {
 325                         /* When control reaches end of non-void function,
 326                            there are no return copy insns at all.  This
 327                            avoids an ice on that invalid function.  */
 328                         if (ret_start + nregs == ret_end)
 329                           short_block = 1;
 330                         break;
 331                       }
 332                     if (!targetm.calls.function_value_regno_p (copy_start))
 333                       copy_num = 0;
 334                     else
 335                       copy_num
 336                         = hard_regno_nregs[copy_start][GET_MODE (copy_reg)];
 337
 338                     /* If the return register is not likely spilled, - as is
 339                        the case for floating point on SH4 - then it might
 340                        be set by an arithmetic operation that needs a
 341                        different mode than the exit block.  */
 342                     for (j = n_entities - 1; j >= 0; j--)
 343                       {
 344                         int e = entity_map[j];
 345                         int mode = MODE_NEEDED (e, return_copy);
 346
 347                         if (mode != num_modes[e] && mode != MODE_EXIT (e))
 348                           break;
 349                       }
 350                     if (j >= 0)
 351                       {
 352                         /* __builtin_return emits a sequence of loads to all
 353                            return registers.  One of them might require
 354                            another mode than MODE_EXIT, even if it is
 355                            unrelated to the return value, so we want to put
 356                            the final mode switch after it.  */
 357                         if (maybe_builtin_apply
 358                             && targetm.calls.function_value_regno_p
 359                                 (copy_start))
 360                           forced_late_switch = 1;
 361
 362                         /* For the SH4, floating point loads depend on fpscr,
 363                            thus we might need to put the final mode switch
 364                            after the return value copy.  That is still OK,
 365                            because a floating point return value does not
 366                            conflict with address reloads.  */
 367                         if (copy_start >= ret_start
 368                             && copy_start + copy_num <= ret_end
 369                             && OBJECT_P (SET_SRC (return_copy_pat)))
 370                           forced_late_switch = 1;
 371                         break;
 372                       }
 373                     if (copy_num == 0)
 374                       {
 375                         last_insn = return_copy;
 376                         continue;
 377                       }
 378
 379                     if (copy_start >= ret_start
 380                         && copy_start + copy_num <= ret_end)
 381                       nregs -= copy_num;
 382                     else if (!maybe_builtin_apply
 383                              || !targetm.calls.function_value_regno_p
 384                                  (copy_start))
 385                       break;
 386                     last_insn = return_copy;
 387                   }
 388                 /* ??? Exception handling can lead to the return value
 389                    copy being already separated from the return value use,
 390                    as in  unwind-dw2.c .
 391                    Similarly, conditionally returning without a value,
 392                    and conditionally using builtin_return can lead to an
 393                    isolated use.  */
 394                 if (return_copy == BB_HEAD (src_bb))
 395                   {
 396                     short_block = 1;
 397                     break;
 398                   }
 399                 last_insn = return_copy;
 400               }
 401             while (nregs);
 402
 403             /* If we didn't see a full return value copy, verify that there
 404                is a plausible reason for this.  If some, but not all of the
 405                return register is likely spilled, we can expect that there
 406                is a copy for the likely spilled part.  */
 407             gcc_assert (!nregs
 408                         || forced_late_switch
 409                         || short_block
 410                         || !(targetm.class_likely_spilled_p
 411                              (REGNO_REG_CLASS (ret_start)))
 412                         || (nregs
 413                             != hard_regno_nregs[ret_start][GET_MODE (ret_reg)])
 414                         /* For multi-hard-register floating point
 415                            values, sometimes the likely-spilled part
 416                            is ordinarily copied first, then the other
 417                            part is set with an arithmetic operation.
 418                            This doesn't actually cause reload
 419                            failures, so let it pass.  */
 420                         || (GET_MODE_CLASS (GET_MODE (ret_reg)) != MODE_INT
 421                             && nregs != 1));
 422
 423             if (!NOTE_INSN_BASIC_BLOCK_P (last_insn))
 424               {
 425                 before_return_copy
 426                   = emit_note_before (NOTE_INSN_DELETED, last_insn);
 427                 /* Instructions preceding LAST_INSN in the same block might
 428                    require a different mode than MODE_EXIT, so if we might
 429                    have such instructions, keep them in a separate block
 430                    from pre_exit.  */
 431                 src_bb = split_block (src_bb,
 432                                       PREV_INSN (before_return_copy))->dest;
 433               }
 434             else
 435               before_return_copy = last_insn;
 436             pre_exit = split_block (src_bb, before_return_copy)->src;
 437           }
 438         else
 439           {
 440             pre_exit = split_edge (eg);
 441           }
 442       }
 443
 444   return pre_exit;
 445 }
 446 #endif
 447
 448 /* Find all insns that need a particular mode setting, and insert the
 449    necessary mode switches.  Return true if we did work.  */
 450
 451 static int
 452 optimize_mode_switching (void)
 453 {
 454   rtx insn;
 455   int e;
 456   basic_block bb;
 457   int need_commit = 0;
 458   sbitmap *kill;
 459   struct edge_list *edge_list;
 460   static const int num_modes[] = NUM_MODES_FOR_MODE_SWITCHING;
 461 #define N_ENTITIES ARRAY_SIZE (num_modes)
 462   int entity_map[N_ENTITIES];
 463   struct bb_info *bb_info[N_ENTITIES];
 464   int i, j;
 465   int n_entities;
 466   int max_num_modes = 0;
 467   bool emitted ATTRIBUTE_UNUSED = false;
 468   basic_block post_entry ATTRIBUTE_UNUSED, pre_exit ATTRIBUTE_UNUSED;
 469
 470   for (e = N_ENTITIES - 1, n_entities = 0; e >= 0; e--)
 471     if (OPTIMIZE_MODE_SWITCHING (e))
 472       {
 473         int entry_exit_extra = 0;
 474
 475         /* Create the list of segments within each basic block.
 476            If NORMAL_MODE is defined, allow for two extra
 477            blocks split from the entry and exit block.  */
 478 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 479         entry_exit_extra = 3;
 480 #endif
 481         bb_info[n_entities]
 482           = XCNEWVEC (struct bb_info, last_basic_block + entry_exit_extra);
 483         entity_map[n_entities++] = e;
 484         if (num_modes[e] > max_num_modes)
 485           max_num_modes = num_modes[e];
 486       }
 487
 488   if (! n_entities)
 489     return 0;
 490
 491 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 492   /* Split the edge from the entry block, so that we can note that
 493      there NORMAL_MODE is supplied.  */
 494   post_entry = split_edge (single_succ_edge (ENTRY_BLOCK_PTR));
 495   pre_exit = create_pre_exit (n_entities, entity_map, num_modes);
 496 #endif
 497
 498   df_analyze ();
 499
 500   /* Create the bitmap vectors.  */
 501
 502   antic = sbitmap_vector_alloc (last_basic_block, n_entities);
 503   transp = sbitmap_vector_alloc (last_basic_block, n_entities);
 504   comp = sbitmap_vector_alloc (last_basic_block, n_entities);
 505
 506   bitmap_vector_ones (transp, last_basic_block);
 507
 508   for (j = n_entities - 1; j >= 0; j--)
 509     {
 510       int e = entity_map[j];
 511       int no_mode = num_modes[e];
 512       struct bb_info *info = bb_info[j];
 513
 514       /* Determine what the first use (if any) need for a mode of entity E is.
 515          This will be the mode that is anticipatable for this block.
 516          Also compute the initial transparency settings.  */
 517       FOR_EACH_BB (bb)
 518         {
 519           struct seginfo *ptr;
 520           int last_mode = no_mode;
 521           bool any_set_required = false;
 522           HARD_REG_SET live_now;
 523
 524           REG_SET_TO_HARD_REG_SET (live_now, df_get_live_in (bb));
 525
 526           /* Pretend the mode is clobbered across abnormal edges.  */
 527           {
 528             edge_iterator ei;
 529             edge e;
 530             FOR_EACH_EDGE (e, ei, bb->preds)
 531               if (e->flags & EDGE_COMPLEX)
 532                 break;
 533             if (e)
 534               {
 535                 ptr = new_seginfo (no_mode, BB_HEAD (bb), bb->index, live_now);
 536                 add_seginfo (info + bb->index, ptr);
 537                 bitmap_clear_bit (transp[bb->index], j);
 538               }
 539           }
 540
 541           FOR_BB_INSNS (bb, insn)
 542             {
 543               if (INSN_P (insn))
 544                 {
 545                   int mode = MODE_NEEDED (e, insn);
 546                   rtx link;
 547
 548                   if (mode != no_mode && mode != last_mode)
 549                     {
 550                       any_set_required = true;
 551                       last_mode = mode;
 552                       ptr = new_seginfo (mode, insn, bb->index, live_now);
 553                       add_seginfo (info + bb->index, ptr);
 554                       bitmap_clear_bit (transp[bb->index], j);
 555                     }
 556 #ifdef MODE_AFTER
 557                   last_mode = MODE_AFTER (e, last_mode, insn);
 558 #endif
 559                   /* Update LIVE_NOW.  */
 560                   for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
 561                     if (REG_NOTE_KIND (link) == REG_DEAD)
 562                       reg_dies (XEXP (link, 0), &live_now);
 563
 564                   note_stores (PATTERN (insn), reg_becomes_live, &live_now);
 565                   for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
 566                     if (REG_NOTE_KIND (link) == REG_UNUSED)
 567                       reg_dies (XEXP (link, 0), &live_now);
 568                 }
 569             }
 570
 571           info[bb->index].computing = last_mode;
 572           /* Check for blocks without ANY mode requirements.
 573              N.B. because of MODE_AFTER, last_mode might still be different
 574              from no_mode.  */
 575           if (!any_set_required)
 576             {
 577               ptr = new_seginfo (no_mode, BB_END (bb), bb->index, live_now);
 578               add_seginfo (info + bb->index, ptr);
 579             }
 580         }
 581 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 582       {
 583         int mode = MODE_ENTRY (e);
 584
 585         if (mode != no_mode)
 586           {
 587             bb = post_entry;
 588
 589             /* By always making this nontransparent, we save
 590                an extra check in make_preds_opaque.  We also
 591                need this to avoid confusing pre_edge_lcm when
 592                antic is cleared but transp and comp are set.  */
 593             bitmap_clear_bit (transp[bb->index], j);
 594
 595             /* Insert a fake computing definition of MODE into entry
 596                blocks which compute no mode. This represents the mode on
 597                entry.  */
 598             info[bb->index].computing = mode;
 599
 600             if (pre_exit)
 601               info[pre_exit->index].seginfo->mode = MODE_EXIT (e);
 602           }
 603       }
 604 #endif /* NORMAL_MODE */
 605     }
 606
 607   kill = sbitmap_vector_alloc (last_basic_block, n_entities);
 608   for (i = 0; i < max_num_modes; i++)
 609     {
 610       int current_mode[N_ENTITIES];
 611       sbitmap *del;
 612       sbitmap *insert;
 613
 614       /* Set the anticipatable and computing arrays.  */
 615       bitmap_vector_clear (antic, last_basic_block);
 616       bitmap_vector_clear (comp, last_basic_block);
 617       for (j = n_entities - 1; j >= 0; j--)
 618         {
 619           int m = current_mode[j] = MODE_PRIORITY_TO_MODE (entity_map[j], i);
 620           struct bb_info *info = bb_info[j];
 621
 622           FOR_EACH_BB (bb)
 623             {
 624               if (info[bb->index].seginfo->mode == m)
 625                 bitmap_set_bit (antic[bb->index], j);
 626
 627               if (info[bb->index].computing == m)
 628                 bitmap_set_bit (comp[bb->index], j);
 629             }
 630         }
 631
 632       /* Calculate the optimal locations for the
 633          placement mode switches to modes with priority I.  */
 634
 635       FOR_EACH_BB (bb)
 636         bitmap_not (kill[bb->index], transp[bb->index]);
 637       edge_list = pre_edge_lcm (n_entities, transp, comp, antic,
 638                                 kill, &insert, &del);
 639
 640       for (j = n_entities - 1; j >= 0; j--)
 641         {
 642           /* Insert all mode sets that have been inserted by lcm.  */
 643           int no_mode = num_modes[entity_map[j]];
 644
 645           /* Wherever we have moved a mode setting upwards in the flow graph,
 646              the blocks between the new setting site and the now redundant
 647              computation ceases to be transparent for any lower-priority
 648              mode of the same entity.  First set the aux field of each
 649              insertion site edge non-transparent, then propagate the new
 650              non-transparency from the redundant computation upwards till
 651              we hit an insertion site or an already non-transparent block.  */
 652           for (e = NUM_EDGES (edge_list) - 1; e >= 0; e--)
 653             {
 654               edge eg = INDEX_EDGE (edge_list, e);
 655               int mode;
 656               basic_block src_bb;
 657               HARD_REG_SET live_at_edge;
 658               rtx mode_set;
 659
 660               eg->aux = 0;
 661
 662               if (! bitmap_bit_p (insert[e], j))
 663                 continue;
 664
 665               eg->aux = (void *)1;
 666
 667               mode = current_mode[j];
 668               src_bb = eg->src;
 669
 670               REG_SET_TO_HARD_REG_SET (live_at_edge, df_get_live_out (src_bb));
 671
 672               rtl_profile_for_edge (eg);
 673               start_sequence ();
 674               EMIT_MODE_SET (entity_map[j], mode, live_at_edge);
 675               mode_set = get_insns ();
 676               end_sequence ();
 677               default_rtl_profile ();
 678
 679               /* Do not bother to insert empty sequence.  */
 680               if (mode_set == NULL_RTX)
 681                 continue;
 682
 683               /* We should not get an abnormal edge here.  */
 684               gcc_assert (! (eg->flags & EDGE_ABNORMAL));
 685
 686               need_commit = 1;
 687               insert_insn_on_edge (mode_set, eg);
 688             }
 689
 690           FOR_EACH_BB_REVERSE (bb)
 691             if (bitmap_bit_p (del[bb->index], j))
 692               {
 693                 make_preds_opaque (bb, j);
 694                 /* Cancel the 'deleted' mode set.  */
 695                 bb_info[j][bb->index].seginfo->mode = no_mode;
 696               }
 697         }
 698
 699       sbitmap_vector_free (del);
 700       sbitmap_vector_free (insert);
 701       clear_aux_for_edges ();
 702       free_edge_list (edge_list);
 703     }
 704
 705   /* Now output the remaining mode sets in all the segments.  */
 706   for (j = n_entities - 1; j >= 0; j--)
 707     {
 708       int no_mode = num_modes[entity_map[j]];
 709
 710       FOR_EACH_BB_REVERSE (bb)
 711         {
 712           struct seginfo *ptr, *next;
 713           for (ptr = bb_info[j][bb->index].seginfo; ptr; ptr = next)
 714             {
 715               next = ptr->next;
 716               if (ptr->mode != no_mode)
 717                 {
 718                   rtx mode_set;
 719
 720                   rtl_profile_for_bb (bb);
 721                   start_sequence ();
 722                   EMIT_MODE_SET (entity_map[j], ptr->mode, ptr->regs_live);
 723                   mode_set = get_insns ();
 724                   end_sequence ();
 725
 726                   /* Insert MODE_SET only if it is nonempty.  */
 727                   if (mode_set != NULL_RTX)
 728                     {
 729                       emitted = true;
 730                       if (NOTE_INSN_BASIC_BLOCK_P (ptr->insn_ptr))
 731                         emit_insn_after (mode_set, ptr->insn_ptr);
 732                       else
 733                         emit_insn_before (mode_set, ptr->insn_ptr);
 734                     }
 735
 736                   default_rtl_profile ();
 737                 }
 738
 739               free (ptr);
 740             }
 741         }
 742
 743       free (bb_info[j]);
 744     }
 745
 746   /* Finished. Free up all the things we've allocated.  */
 747   sbitmap_vector_free (kill);
 748   sbitmap_vector_free (antic);
 749   sbitmap_vector_free (transp);
 750   sbitmap_vector_free (comp);
 751
 752   if (need_commit)
 753     commit_edge_insertions ();
 754
 755 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 756   cleanup_cfg (CLEANUP_NO_INSN_DEL);
 757 #else
 758   if (!need_commit && !emitted)
 759     return 0;
 760 #endif
 761
 762   return 1;
 763 }
 764
 765 #endif /* OPTIMIZE_MODE_SWITCHING */
 766 \f
 767 static bool
 768 gate_mode_switching (void)
 769 {
 770 #ifdef OPTIMIZE_MODE_SWITCHING
 771   return true;
 772 #else
 773   return false;
 774 #endif
 775 }
 776
 777 static unsigned int
 778 rest_of_handle_mode_switching (void)
 779 {
 780 #ifdef OPTIMIZE_MODE_SWITCHING
 781   optimize_mode_switching ();
 782 #endif /* OPTIMIZE_MODE_SWITCHING */
 783   return 0;
 784 }
 785
 786
 787 struct rtl_opt_pass pass_mode_switching =
 788 {
 789  {
 790   RTL_PASS,
 791   "mode_sw",                            /* name */
 792   OPTGROUP_NONE,                        /* optinfo_flags */
 793   gate_mode_switching,                  /* gate */
 794   rest_of_handle_mode_switching,        /* execute */
 795   NULL,                                 /* sub */
 796   NULL,                                 /* next */
 797   0,                                    /* static_pass_number */
 798   TV_MODE_SWITCH,                       /* tv_id */
 799   0,                                    /* properties_required */
 800   0,                                    /* properties_provided */
 801   0,                                    /* properties_destroyed */
 802   0,                                    /* todo_flags_start */
 803   TODO_df_finish | TODO_verify_rtl_sharing |
 804   0                                     /* todo_flags_finish */
 805  }
 806 };