gcc/mode-switching.c

   1 /* CPU mode switching
   2    Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
   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 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 #include "config.h"
  23 #include "system.h"
  24 #include "coretypes.h"
  25 #include "tm.h"
  26 #include "rtl.h"
  27 #include "regs.h"
  28 #include "hard-reg-set.h"
  29 #include "flags.h"
  30 #include "real.h"
  31 #include "insn-config.h"
  32 #include "recog.h"
  33 #include "basic-block.h"
  34 #include "output.h"
  35 #include "tm_p.h"
  36 #include "function.h"
  37 #include "tree-pass.h"
  38 #include "timevar.h"
  39
  40 /* We want target macros for the mode switching code to be able to refer
  41    to instruction attribute values.  */
  42 #include "insn-attr.h"
  43
  44 #ifdef OPTIMIZE_MODE_SWITCHING
  45
  46 /* The algorithm for setting the modes consists of scanning the insn list
  47    and finding all the insns which require a specific mode.  Each insn gets
  48    a unique struct seginfo element.  These structures are inserted into a list
  49    for each basic block.  For each entity, there is an array of bb_info over
  50    the flow graph basic blocks (local var 'bb_info'), and contains a list
  51    of all insns within that basic block, in the order they are encountered.
  52
  53    For each entity, any basic block WITHOUT any insns requiring a specific
  54    mode are given a single entry, without a mode.  (Each basic block
  55    in the flow graph must have at least one entry in the segment table.)
  56
  57    The LCM algorithm is then run over the flow graph to determine where to
  58    place the sets to the highest-priority value in respect of first the first
  59    insn in any one block.  Any adjustments required to the transparency
  60    vectors are made, then the next iteration starts for the next-lower
  61    priority mode, till for each entity all modes are exhausted.
  62
  63    More details are located in the code for optimize_mode_switching().  */
  64 \f
  65 /* This structure contains the information for each insn which requires
  66    either single or double mode to be set.
  67    MODE is the mode this insn must be executed in.
  68    INSN_PTR is the insn to be executed (may be the note that marks the
  69    beginning of a basic block).
  70    BBNUM is the flow graph basic block this insn occurs in.
  71    NEXT is the next insn in the same basic block.  */
  72 struct seginfo
  73 {
  74   int mode;
  75   rtx insn_ptr;
  76   int bbnum;
  77   struct seginfo *next;
  78   HARD_REG_SET regs_live;
  79 };
  80
  81 struct bb_info
  82 {
  83   struct seginfo *seginfo;
  84   int computing;
  85 };
  86
  87 /* These bitmaps are used for the LCM algorithm.  */
  88
  89 static sbitmap *antic;
  90 static sbitmap *transp;
  91 static sbitmap *comp;
  92
  93 static struct seginfo * new_seginfo (int, rtx, int, HARD_REG_SET);
  94 static void add_seginfo (struct bb_info *, struct seginfo *);
  95 static void reg_dies (rtx, HARD_REG_SET);
  96 static void reg_becomes_live (rtx, rtx, void *);
  97 static void make_preds_opaque (basic_block, int);
  98 \f
  99
 100 /* This function will allocate a new BBINFO structure, initialized
 101    with the MODE, INSN, and basic block BB parameters.  */
 102
 103 static struct seginfo *
 104 new_seginfo (int mode, rtx insn, int bb, HARD_REG_SET regs_live)
 105 {
 106   struct seginfo *ptr;
 107   ptr = XNEW (struct seginfo);
 108   ptr->mode = mode;
 109   ptr->insn_ptr = insn;
 110   ptr->bbnum = bb;
 111   ptr->next = NULL;
 112   COPY_HARD_REG_SET (ptr->regs_live, regs_live);
 113   return ptr;
 114 }
 115
 116 /* Add a seginfo element to the end of a list.
 117    HEAD is a pointer to the list beginning.
 118    INFO is the structure to be linked in.  */
 119
 120 static void
 121 add_seginfo (struct bb_info *head, struct seginfo *info)
 122 {
 123   struct seginfo *ptr;
 124
 125   if (head->seginfo == NULL)
 126     head->seginfo = info;
 127   else
 128     {
 129       ptr = head->seginfo;
 130       while (ptr->next != NULL)
 131         ptr = ptr->next;
 132       ptr->next = info;
 133     }
 134 }
 135
 136 /* Make all predecessors of basic block B opaque, recursively, till we hit
 137    some that are already non-transparent, or an edge where aux is set; that
 138    denotes that a mode set is to be done on that edge.
 139    J is the bit number in the bitmaps that corresponds to the entity that
 140    we are currently handling mode-switching for.  */
 141
 142 static void
 143 make_preds_opaque (basic_block b, int j)
 144 {
 145   edge e;
 146   edge_iterator ei;
 147
 148   FOR_EACH_EDGE (e, ei, b->preds)
 149     {
 150       basic_block pb = e->src;
 151
 152       if (e->aux || ! TEST_BIT (transp[pb->index], j))
 153         continue;
 154
 155       RESET_BIT (transp[pb->index], j);
 156       make_preds_opaque (pb, j);
 157     }
 158 }
 159
 160 /* Record in LIVE that register REG died.  */
 161
 162 static void
 163 reg_dies (rtx reg, HARD_REG_SET live)
 164 {
 165   int regno, nregs;
 166
 167   if (!REG_P (reg))
 168     return;
 169
 170   regno = REGNO (reg);
 171   if (regno < FIRST_PSEUDO_REGISTER)
 172     for (nregs = hard_regno_nregs[regno][GET_MODE (reg)] - 1; nregs >= 0;
 173          nregs--)
 174       CLEAR_HARD_REG_BIT (live, regno + nregs);
 175 }
 176
 177 /* Record in LIVE that register REG became live.
 178    This is called via note_stores.  */
 179
 180 static void
 181 reg_becomes_live (rtx reg, rtx setter ATTRIBUTE_UNUSED, void *live)
 182 {
 183   int regno, nregs;
 184
 185   if (GET_CODE (reg) == SUBREG)
 186     reg = SUBREG_REG (reg);
 187
 188   if (!REG_P (reg))
 189     return;
 190
 191   regno = REGNO (reg);
 192   if (regno < FIRST_PSEUDO_REGISTER)
 193     for (nregs = hard_regno_nregs[regno][GET_MODE (reg)] - 1; nregs >= 0;
 194          nregs--)
 195       SET_HARD_REG_BIT (* (HARD_REG_SET *) live, regno + nregs);
 196 }
 197
 198 /* Make sure if MODE_ENTRY is defined the MODE_EXIT is defined
 199    and vice versa.  */
 200 #if defined (MODE_ENTRY) != defined (MODE_EXIT)
 201  #error "Both MODE_ENTRY and MODE_EXIT must be defined"
 202 #endif
 203
 204 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 205 /* Split the fallthrough edge to the exit block, so that we can note
 206    that there NORMAL_MODE is required.  Return the new block if it's
 207    inserted before the exit block.  Otherwise return null.  */
 208
 209 static basic_block
 210 create_pre_exit (int n_entities, int *entity_map, const int *num_modes)
 211 {
 212   edge eg;
 213   edge_iterator ei;
 214   basic_block pre_exit;
 215
 216   /* The only non-call predecessor at this stage is a block with a
 217      fallthrough edge; there can be at most one, but there could be
 218      none at all, e.g. when exit is called.  */
 219   pre_exit = 0;
 220   FOR_EACH_EDGE (eg, ei, EXIT_BLOCK_PTR->preds)
 221     if (eg->flags & EDGE_FALLTHRU)
 222       {
 223         basic_block src_bb = eg->src;
 224         regset live_at_end = src_bb->il.rtl->global_live_at_end;
 225         rtx last_insn, ret_reg;
 226
 227         gcc_assert (!pre_exit);
 228         /* If this function returns a value at the end, we have to
 229            insert the final mode switch before the return value copy
 230            to its hard register.  */
 231         if (EDGE_COUNT (EXIT_BLOCK_PTR->preds) == 1
 232             && NONJUMP_INSN_P ((last_insn = BB_END (src_bb)))
 233             && GET_CODE (PATTERN (last_insn)) == USE
 234             && GET_CODE ((ret_reg = XEXP (PATTERN (last_insn), 0))) == REG)
 235           {
 236             int ret_start = REGNO (ret_reg);
 237             int nregs = hard_regno_nregs[ret_start][GET_MODE (ret_reg)];
 238             int ret_end = ret_start + nregs;
 239             int short_block = 0;
 240             int maybe_builtin_apply = 0;
 241             int forced_late_switch = 0;
 242             rtx before_return_copy;
 243
 244             do
 245               {
 246                 rtx return_copy = PREV_INSN (last_insn);
 247                 rtx return_copy_pat, copy_reg;
 248                 int copy_start, copy_num;
 249                 int j;
 250
 251                 if (INSN_P (return_copy))
 252                   {
 253                     if (GET_CODE (PATTERN (return_copy)) == USE
 254                         && GET_CODE (XEXP (PATTERN (return_copy), 0)) == REG
 255                         && (FUNCTION_VALUE_REGNO_P
 256                             (REGNO (XEXP (PATTERN (return_copy), 0)))))
 257                       {
 258                         maybe_builtin_apply = 1;
 259                         last_insn = return_copy;
 260                         continue;
 261                       }
 262                     /* If the return register is not (in its entirety)
 263                        likely spilled, the return copy might be
 264                        partially or completely optimized away.  */
 265                     return_copy_pat = single_set (return_copy);
 266                     if (!return_copy_pat)
 267                       {
 268                         return_copy_pat = PATTERN (return_copy);
 269                         if (GET_CODE (return_copy_pat) != CLOBBER)
 270                           break;
 271                       }
 272                     copy_reg = SET_DEST (return_copy_pat);
 273                     if (GET_CODE (copy_reg) == REG)
 274                       copy_start = REGNO (copy_reg);
 275                     else if (GET_CODE (copy_reg) == SUBREG
 276                              && GET_CODE (SUBREG_REG (copy_reg)) == REG)
 277                       copy_start = REGNO (SUBREG_REG (copy_reg));
 278                     else
 279                       break;
 280                     if (copy_start >= FIRST_PSEUDO_REGISTER)
 281                       break;
 282                     copy_num
 283                       = hard_regno_nregs[copy_start][GET_MODE (copy_reg)];
 284
 285                     /* If the return register is not likely spilled, - as is
 286                        the case for floating point on SH4 - then it might
 287                        be set by an arithmetic operation that needs a
 288                        different mode than the exit block.  */
 289                     for (j = n_entities - 1; j >= 0; j--)
 290                       {
 291                         int e = entity_map[j];
 292                         int mode = MODE_NEEDED (e, return_copy);
 293
 294                         if (mode != num_modes[e] && mode != MODE_EXIT (e))
 295                           break;
 296                       }
 297                     if (j >= 0)
 298                       {
 299                         /* For the SH4, floating point loads depend on fpscr,
 300                            thus we might need to put the final mode switch
 301                            after the return value copy.  That is still OK,
 302                            because a floating point return value does not
 303                            conflict with address reloads.  */
 304                         if (copy_start >= ret_start
 305                             && copy_start + copy_num <= ret_end
 306                             && OBJECT_P (SET_SRC (return_copy_pat)))
 307                           forced_late_switch = 1;
 308                         break;
 309                       }
 310
 311                     if (copy_start >= ret_start
 312                         && copy_start + copy_num <= ret_end)
 313                       nregs -= copy_num;
 314                     else if (!maybe_builtin_apply
 315                              || !FUNCTION_VALUE_REGNO_P (copy_start))
 316                       break;
 317                     last_insn = return_copy;
 318                   }
 319                 /* ??? Exception handling can lead to the return value
 320                    copy being already separated from the return value use,
 321                    as in  unwind-dw2.c .
 322                    Similarly, conditionally returning without a value,
 323                    and conditionally using builtin_return can lead to an
 324                    isolated use.  */
 325                 if (return_copy == BB_HEAD (src_bb))
 326                   {
 327                     short_block = 1;
 328                     break;
 329                   }
 330                 last_insn = return_copy;
 331               }
 332             while (nregs);
 333
 334             /* If we didn't see a full return value copy, verify that there
 335                is a plausible reason for this.  If some, but not all of the
 336                return register is likely spilled, we can expect that there
 337                is a copy for the likely spilled part.  */
 338             gcc_assert (!nregs
 339                         || forced_late_switch
 340                         || short_block
 341                         || !(CLASS_LIKELY_SPILLED_P
 342                              (REGNO_REG_CLASS (ret_start)))
 343                         || (nregs
 344                             != hard_regno_nregs[ret_start][GET_MODE (ret_reg)])
 345                         /* For multi-hard-register floating point
 346                            values, sometimes the likely-spilled part
 347                            is ordinarily copied first, then the other
 348                            part is set with an arithmetic operation.
 349                            This doesn't actually cause reload
 350                            failures, so let it pass.  */
 351                         || (GET_MODE_CLASS (GET_MODE (ret_reg)) != MODE_INT
 352                             && nregs != 1));
 353
 354             if (INSN_P (last_insn))
 355               {
 356                 before_return_copy
 357                   = emit_note_before (NOTE_INSN_DELETED, last_insn);
 358                 /* Instructions preceding LAST_INSN in the same block might
 359                    require a different mode than MODE_EXIT, so if we might
 360                    have such instructions, keep them in a separate block
 361                    from pre_exit.  */
 362                 if (last_insn != BB_HEAD (src_bb))
 363                   src_bb = split_block (src_bb,
 364                                         PREV_INSN (before_return_copy))->dest;
 365               }
 366             else
 367               before_return_copy = last_insn;
 368             pre_exit = split_block (src_bb, before_return_copy)->src;
 369           }
 370         else
 371           {
 372             pre_exit = split_edge (eg);
 373             COPY_REG_SET (pre_exit->il.rtl->global_live_at_start, live_at_end);
 374             COPY_REG_SET (pre_exit->il.rtl->global_live_at_end, live_at_end);
 375           }
 376       }
 377
 378   return pre_exit;
 379 }
 380 #endif
 381
 382 /* Find all insns that need a particular mode setting, and insert the
 383    necessary mode switches.  Return true if we did work.  */
 384
 385 static int
 386 optimize_mode_switching (void)
 387 {
 388   rtx insn;
 389   int e;
 390   basic_block bb;
 391   int need_commit = 0;
 392   sbitmap *kill;
 393   struct edge_list *edge_list;
 394   static const int num_modes[] = NUM_MODES_FOR_MODE_SWITCHING;
 395 #define N_ENTITIES ARRAY_SIZE (num_modes)
 396   int entity_map[N_ENTITIES];
 397   struct bb_info *bb_info[N_ENTITIES];
 398   int i, j;
 399   int n_entities;
 400   int max_num_modes = 0;
 401   bool emited = false;
 402   basic_block post_entry ATTRIBUTE_UNUSED, pre_exit ATTRIBUTE_UNUSED;
 403
 404   clear_bb_flags ();
 405
 406   for (e = N_ENTITIES - 1, n_entities = 0; e >= 0; e--)
 407     if (OPTIMIZE_MODE_SWITCHING (e))
 408       {
 409         int entry_exit_extra = 0;
 410
 411         /* Create the list of segments within each basic block.
 412            If NORMAL_MODE is defined, allow for two extra
 413            blocks split from the entry and exit block.  */
 414 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 415         entry_exit_extra = 3;
 416 #endif
 417         bb_info[n_entities]
 418           = XCNEWVEC (struct bb_info, last_basic_block + entry_exit_extra);
 419         entity_map[n_entities++] = e;
 420         if (num_modes[e] > max_num_modes)
 421           max_num_modes = num_modes[e];
 422       }
 423
 424   if (! n_entities)
 425     return 0;
 426
 427 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 428   /* Split the edge from the entry block, so that we can note that
 429      there NORMAL_MODE is supplied.  */
 430   post_entry = split_edge (single_succ_edge (ENTRY_BLOCK_PTR));
 431   pre_exit = create_pre_exit (n_entities, entity_map, num_modes);
 432 #endif
 433
 434   /* Create the bitmap vectors.  */
 435
 436   antic = sbitmap_vector_alloc (last_basic_block, n_entities);
 437   transp = sbitmap_vector_alloc (last_basic_block, n_entities);
 438   comp = sbitmap_vector_alloc (last_basic_block, n_entities);
 439
 440   sbitmap_vector_ones (transp, last_basic_block);
 441
 442   for (j = n_entities - 1; j >= 0; j--)
 443     {
 444       int e = entity_map[j];
 445       int no_mode = num_modes[e];
 446       struct bb_info *info = bb_info[j];
 447
 448       /* Determine what the first use (if any) need for a mode of entity E is.
 449          This will be the mode that is anticipatable for this block.
 450          Also compute the initial transparency settings.  */
 451       FOR_EACH_BB (bb)
 452         {
 453           struct seginfo *ptr;
 454           int last_mode = no_mode;
 455           HARD_REG_SET live_now;
 456
 457           REG_SET_TO_HARD_REG_SET (live_now,
 458                                    bb->il.rtl->global_live_at_start);
 459
 460           /* Pretend the mode is clobbered across abnormal edges.  */
 461           {
 462             edge_iterator ei;
 463             edge e;
 464             FOR_EACH_EDGE (e, ei, bb->preds)
 465               if (e->flags & EDGE_COMPLEX)
 466                 break;
 467             if (e)
 468               {
 469                 ptr = new_seginfo (no_mode, BB_HEAD (bb), bb->index, live_now);
 470                 add_seginfo (info + bb->index, ptr);
 471                 RESET_BIT (transp[bb->index], j);
 472               }
 473           }
 474
 475           for (insn = BB_HEAD (bb);
 476                insn != NULL && insn != NEXT_INSN (BB_END (bb));
 477                insn = NEXT_INSN (insn))
 478             {
 479               if (INSN_P (insn))
 480                 {
 481                   int mode = MODE_NEEDED (e, insn);
 482                   rtx link;
 483
 484                   if (mode != no_mode && mode != last_mode)
 485                     {
 486                       last_mode = mode;
 487                       ptr = new_seginfo (mode, insn, bb->index, live_now);
 488                       add_seginfo (info + bb->index, ptr);
 489                       RESET_BIT (transp[bb->index], j);
 490                     }
 491 #ifdef MODE_AFTER
 492                   last_mode = MODE_AFTER (last_mode, insn);
 493 #endif
 494                   /* Update LIVE_NOW.  */
 495                   for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
 496                     if (REG_NOTE_KIND (link) == REG_DEAD)
 497                       reg_dies (XEXP (link, 0), live_now);
 498
 499                   note_stores (PATTERN (insn), reg_becomes_live, &live_now);
 500                   for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
 501                     if (REG_NOTE_KIND (link) == REG_UNUSED)
 502                       reg_dies (XEXP (link, 0), live_now);
 503                 }
 504             }
 505
 506           info[bb->index].computing = last_mode;
 507           /* Check for blocks without ANY mode requirements.  */
 508           if (last_mode == no_mode)
 509             {
 510               ptr = new_seginfo (no_mode, BB_END (bb), bb->index, live_now);
 511               add_seginfo (info + bb->index, ptr);
 512             }
 513         }
 514 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 515       {
 516         int mode = MODE_ENTRY (e);
 517
 518         if (mode != no_mode)
 519           {
 520             bb = post_entry;
 521
 522             /* By always making this nontransparent, we save
 523                an extra check in make_preds_opaque.  We also
 524                need this to avoid confusing pre_edge_lcm when
 525                antic is cleared but transp and comp are set.  */
 526             RESET_BIT (transp[bb->index], j);
 527
 528             /* Insert a fake computing definition of MODE into entry
 529                blocks which compute no mode. This represents the mode on
 530                entry.  */
 531             info[bb->index].computing = mode;
 532
 533             if (pre_exit)
 534               info[pre_exit->index].seginfo->mode = MODE_EXIT (e);
 535           }
 536       }
 537 #endif /* NORMAL_MODE */
 538     }
 539
 540   kill = sbitmap_vector_alloc (last_basic_block, n_entities);
 541   for (i = 0; i < max_num_modes; i++)
 542     {
 543       int current_mode[N_ENTITIES];
 544       sbitmap *delete;
 545       sbitmap *insert;
 546
 547       /* Set the anticipatable and computing arrays.  */
 548       sbitmap_vector_zero (antic, last_basic_block);
 549       sbitmap_vector_zero (comp, last_basic_block);
 550       for (j = n_entities - 1; j >= 0; j--)
 551         {
 552           int m = current_mode[j] = MODE_PRIORITY_TO_MODE (entity_map[j], i);
 553           struct bb_info *info = bb_info[j];
 554
 555           FOR_EACH_BB (bb)
 556             {
 557               if (info[bb->index].seginfo->mode == m)
 558                 SET_BIT (antic[bb->index], j);
 559
 560               if (info[bb->index].computing == m)
 561                 SET_BIT (comp[bb->index], j);
 562             }
 563         }
 564
 565       /* Calculate the optimal locations for the
 566          placement mode switches to modes with priority I.  */
 567
 568       FOR_EACH_BB (bb)
 569         sbitmap_not (kill[bb->index], transp[bb->index]);
 570       edge_list = pre_edge_lcm (n_entities, transp, comp, antic,
 571                                 kill, &insert, &delete);
 572
 573       for (j = n_entities - 1; j >= 0; j--)
 574         {
 575           /* Insert all mode sets that have been inserted by lcm.  */
 576           int no_mode = num_modes[entity_map[j]];
 577
 578           /* Wherever we have moved a mode setting upwards in the flow graph,
 579              the blocks between the new setting site and the now redundant
 580              computation ceases to be transparent for any lower-priority
 581              mode of the same entity.  First set the aux field of each
 582              insertion site edge non-transparent, then propagate the new
 583              non-transparency from the redundant computation upwards till
 584              we hit an insertion site or an already non-transparent block.  */
 585           for (e = NUM_EDGES (edge_list) - 1; e >= 0; e--)
 586             {
 587               edge eg = INDEX_EDGE (edge_list, e);
 588               int mode;
 589               basic_block src_bb;
 590               HARD_REG_SET live_at_edge;
 591               rtx mode_set;
 592
 593               eg->aux = 0;
 594
 595               if (! TEST_BIT (insert[e], j))
 596                 continue;
 597
 598               eg->aux = (void *)1;
 599
 600               mode = current_mode[j];
 601               src_bb = eg->src;
 602
 603               REG_SET_TO_HARD_REG_SET (live_at_edge,
 604                                        src_bb->il.rtl->global_live_at_end);
 605
 606               start_sequence ();
 607               EMIT_MODE_SET (entity_map[j], mode, live_at_edge);
 608               mode_set = get_insns ();
 609               end_sequence ();
 610
 611               /* Do not bother to insert empty sequence.  */
 612               if (mode_set == NULL_RTX)
 613                 continue;
 614
 615               /* We should not get an abnormal edge here.  */
 616               gcc_assert (! (eg->flags & EDGE_ABNORMAL));
 617
 618               need_commit = 1;
 619               insert_insn_on_edge (mode_set, eg);
 620             }
 621
 622           FOR_EACH_BB_REVERSE (bb)
 623             if (TEST_BIT (delete[bb->index], j))
 624               {
 625                 make_preds_opaque (bb, j);
 626                 /* Cancel the 'deleted' mode set.  */
 627                 bb_info[j][bb->index].seginfo->mode = no_mode;
 628               }
 629         }
 630
 631       sbitmap_vector_free (delete);
 632       sbitmap_vector_free (insert);
 633       clear_aux_for_edges ();
 634       free_edge_list (edge_list);
 635     }
 636
 637   /* Now output the remaining mode sets in all the segments.  */
 638   for (j = n_entities - 1; j >= 0; j--)
 639     {
 640       int no_mode = num_modes[entity_map[j]];
 641
 642       FOR_EACH_BB_REVERSE (bb)
 643         {
 644           struct seginfo *ptr, *next;
 645           for (ptr = bb_info[j][bb->index].seginfo; ptr; ptr = next)
 646             {
 647               next = ptr->next;
 648               if (ptr->mode != no_mode)
 649                 {
 650                   rtx mode_set;
 651
 652                   start_sequence ();
 653                   EMIT_MODE_SET (entity_map[j], ptr->mode, ptr->regs_live);
 654                   mode_set = get_insns ();
 655                   end_sequence ();
 656
 657                   /* Insert MODE_SET only if it is nonempty.  */
 658                   if (mode_set != NULL_RTX)
 659                     {
 660                       emited = true;
 661                       if (NOTE_P (ptr->insn_ptr)
 662                           && (NOTE_LINE_NUMBER (ptr->insn_ptr)
 663                               == NOTE_INSN_BASIC_BLOCK))
 664                         emit_insn_after (mode_set, ptr->insn_ptr);
 665                       else
 666                         emit_insn_before (mode_set, ptr->insn_ptr);
 667                     }
 668                 }
 669
 670               free (ptr);
 671             }
 672         }
 673
 674       free (bb_info[j]);
 675     }
 676
 677   /* Finished. Free up all the things we've allocated.  */
 678
 679   sbitmap_vector_free (kill);
 680   sbitmap_vector_free (antic);
 681   sbitmap_vector_free (transp);
 682   sbitmap_vector_free (comp);
 683
 684   if (need_commit)
 685     commit_edge_insertions ();
 686
 687 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 688   cleanup_cfg (CLEANUP_NO_INSN_DEL);
 689 #else
 690   if (!need_commit && !emited)
 691     return 0;
 692 #endif
 693
 694   max_regno = max_reg_num ();
 695   allocate_reg_info (max_regno, FALSE, FALSE);
 696   update_life_info_in_dirty_blocks (UPDATE_LIFE_GLOBAL_RM_NOTES,
 697                                     (PROP_DEATH_NOTES | PROP_KILL_DEAD_CODE
 698                                      | PROP_SCAN_DEAD_CODE));
 699
 700   return 1;
 701 }
 702
 703 #endif /* OPTIMIZE_MODE_SWITCHING */
 704 \f
 705 static bool
 706 gate_mode_switching (void)
 707 {
 708 #ifdef OPTIMIZE_MODE_SWITCHING
 709   return true;
 710 #else
 711   return false;
 712 #endif
 713 }
 714
 715 static unsigned int
 716 rest_of_handle_mode_switching (void)
 717 {
 718 #ifdef OPTIMIZE_MODE_SWITCHING
 719   no_new_pseudos = 0;
 720   optimize_mode_switching ();
 721   no_new_pseudos = 1;
 722 #endif /* OPTIMIZE_MODE_SWITCHING */
 723   return 0;
 724 }
 725
 726
 727 struct tree_opt_pass pass_mode_switching =
 728 {
 729   "mode-sw",                            /* name */
 730   gate_mode_switching,                  /* gate */
 731   rest_of_handle_mode_switching,        /* execute */
 732   NULL,                                 /* sub */
 733   NULL,                                 /* next */
 734   0,                                    /* static_pass_number */
 735   TV_MODE_SWITCH,                       /* tv_id */
 736   0,                                    /* properties_required */
 737   0,                                    /* properties_provided */
 738   0,                                    /* properties_destroyed */
 739   0,                                    /* todo_flags_start */
 740   TODO_dump_func,                       /* todo_flags_finish */
 741   0                                     /* letter */
 742 };