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                       {
 334                         last_insn = return_copy;
 335                         continue;
 336                       }
 337                     copy_num
 338                       = hard_regno_nregs[copy_start][GET_MODE (copy_reg)];
 339
 340                     /* If the return register is not likely spilled, - as is
 341                        the case for floating point on SH4 - then it might
 342                        be set by an arithmetic operation that needs a
 343                        different mode than the exit block.  */
 344                     for (j = n_entities - 1; j >= 0; j--)
 345                       {
 346                         int e = entity_map[j];
 347                         int mode = MODE_NEEDED (e, return_copy);
 348
 349                         if (mode != num_modes[e] && mode != MODE_EXIT (e))
 350                           break;
 351                       }
 352                     if (j >= 0)
 353                       {
 354                         /* __builtin_return emits a sequence of loads to all
 355                            return registers.  One of them might require
 356                            another mode than MODE_EXIT, even if it is
 357                            unrelated to the return value, so we want to put
 358                            the final mode switch after it.  */
 359                         if (maybe_builtin_apply
 360                             && targetm.calls.function_value_regno_p
 361                                 (copy_start))
 362                           forced_late_switch = 1;
 363
 364                         /* For the SH4, floating point loads depend on fpscr,
 365                            thus we might need to put the final mode switch
 366                            after the return value copy.  That is still OK,
 367                            because a floating point return value does not
 368                            conflict with address reloads.  */
 369                         if (copy_start >= ret_start
 370                             && copy_start + copy_num <= ret_end
 371                             && OBJECT_P (SET_SRC (return_copy_pat)))
 372                           forced_late_switch = 1;
 373                         break;
 374                       }
 375
 376                     if (copy_start >= ret_start
 377                         && copy_start + copy_num <= ret_end)
 378                       nregs -= copy_num;
 379                     else if (!maybe_builtin_apply
 380                              || !targetm.calls.function_value_regno_p
 381                                  (copy_start))
 382                       break;
 383                     last_insn = return_copy;
 384                   }
 385                 /* ??? Exception handling can lead to the return value
 386                    copy being already separated from the return value use,
 387                    as in  unwind-dw2.c .
 388                    Similarly, conditionally returning without a value,
 389                    and conditionally using builtin_return can lead to an
 390                    isolated use.  */
 391                 if (return_copy == BB_HEAD (src_bb))
 392                   {
 393                     short_block = 1;
 394                     break;
 395                   }
 396                 last_insn = return_copy;
 397               }
 398             while (nregs);
 399
 400             /* If we didn't see a full return value copy, verify that there
 401                is a plausible reason for this.  If some, but not all of the
 402                return register is likely spilled, we can expect that there
 403                is a copy for the likely spilled part.  */
 404             gcc_assert (!nregs
 405                         || forced_late_switch
 406                         || short_block
 407                         || !(targetm.class_likely_spilled_p
 408                              (REGNO_REG_CLASS (ret_start)))
 409                         || (nregs
 410                             != hard_regno_nregs[ret_start][GET_MODE (ret_reg)])
 411                         /* For multi-hard-register floating point
 412                            values, sometimes the likely-spilled part
 413                            is ordinarily copied first, then the other
 414                            part is set with an arithmetic operation.
 415                            This doesn't actually cause reload
 416                            failures, so let it pass.  */
 417                         || (GET_MODE_CLASS (GET_MODE (ret_reg)) != MODE_INT
 418                             && nregs != 1));
 419
 420             if (INSN_P (last_insn))
 421               {
 422                 before_return_copy
 423                   = emit_note_before (NOTE_INSN_DELETED, last_insn);
 424                 /* Instructions preceding LAST_INSN in the same block might
 425                    require a different mode than MODE_EXIT, so if we might
 426                    have such instructions, keep them in a separate block
 427                    from pre_exit.  */
 428                 if (last_insn != BB_HEAD (src_bb))
 429                   src_bb = split_block (src_bb,
 430                                         PREV_INSN (before_return_copy))->dest;
 431               }
 432             else
 433               before_return_copy = last_insn;
 434             pre_exit = split_block (src_bb, before_return_copy)->src;
 435           }
 436         else
 437           {
 438             pre_exit = split_edge (eg);
 439           }
 440       }
 441
 442   return pre_exit;
 443 }
 444 #endif
 445
 446 /* Find all insns that need a particular mode setting, and insert the
 447    necessary mode switches.  Return true if we did work.  */
 448
 449 static int
 450 optimize_mode_switching (void)
 451 {
 452   rtx insn;
 453   int e;
 454   basic_block bb;
 455   int need_commit = 0;
 456   sbitmap *kill;
 457   struct edge_list *edge_list;
 458   static const int num_modes[] = NUM_MODES_FOR_MODE_SWITCHING;
 459 #define N_ENTITIES ARRAY_SIZE (num_modes)
 460   int entity_map[N_ENTITIES];
 461   struct bb_info *bb_info[N_ENTITIES];
 462   int i, j;
 463   int n_entities;
 464   int max_num_modes = 0;
 465   bool emitted ATTRIBUTE_UNUSED = false;
 466   basic_block post_entry ATTRIBUTE_UNUSED, pre_exit ATTRIBUTE_UNUSED;
 467
 468   for (e = N_ENTITIES - 1, n_entities = 0; e >= 0; e--)
 469     if (OPTIMIZE_MODE_SWITCHING (e))
 470       {
 471         int entry_exit_extra = 0;
 472
 473         /* Create the list of segments within each basic block.
 474            If NORMAL_MODE is defined, allow for two extra
 475            blocks split from the entry and exit block.  */
 476 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 477         entry_exit_extra = 3;
 478 #endif
 479         bb_info[n_entities]
 480           = XCNEWVEC (struct bb_info, last_basic_block + entry_exit_extra);
 481         entity_map[n_entities++] = e;
 482         if (num_modes[e] > max_num_modes)
 483           max_num_modes = num_modes[e];
 484       }
 485
 486   if (! n_entities)
 487     return 0;
 488
 489 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 490   /* Split the edge from the entry block, so that we can note that
 491      there NORMAL_MODE is supplied.  */
 492   post_entry = split_edge (single_succ_edge (ENTRY_BLOCK_PTR));
 493   pre_exit = create_pre_exit (n_entities, entity_map, num_modes);
 494 #endif
 495
 496   df_analyze ();
 497
 498   /* Create the bitmap vectors.  */
 499
 500   antic = sbitmap_vector_alloc (last_basic_block, n_entities);
 501   transp = sbitmap_vector_alloc (last_basic_block, n_entities);
 502   comp = sbitmap_vector_alloc (last_basic_block, n_entities);
 503
 504   bitmap_vector_ones (transp, last_basic_block);
 505
 506   for (j = n_entities - 1; j >= 0; j--)
 507     {
 508       int e = entity_map[j];
 509       int no_mode = num_modes[e];
 510       struct bb_info *info = bb_info[j];
 511
 512       /* Determine what the first use (if any) need for a mode of entity E is.
 513          This will be the mode that is anticipatable for this block.
 514          Also compute the initial transparency settings.  */
 515       FOR_EACH_BB (bb)
 516         {
 517           struct seginfo *ptr;
 518           int last_mode = no_mode;
 519           bool any_set_required = false;
 520           HARD_REG_SET live_now;
 521
 522           REG_SET_TO_HARD_REG_SET (live_now, df_get_live_in (bb));
 523
 524           /* Pretend the mode is clobbered across abnormal edges.  */
 525           {
 526             edge_iterator ei;
 527             edge e;
 528             FOR_EACH_EDGE (e, ei, bb->preds)
 529               if (e->flags & EDGE_COMPLEX)
 530                 break;
 531             if (e)
 532               {
 533                 ptr = new_seginfo (no_mode, BB_HEAD (bb), bb->index, live_now);
 534                 add_seginfo (info + bb->index, ptr);
 535                 bitmap_clear_bit (transp[bb->index], j);
 536               }
 537           }
 538
 539           FOR_BB_INSNS (bb, insn)
 540             {
 541               if (INSN_P (insn))
 542                 {
 543                   int mode = MODE_NEEDED (e, insn);
 544                   rtx link;
 545
 546                   if (mode != no_mode && mode != last_mode)
 547                     {
 548                       any_set_required = true;
 549                       last_mode = mode;
 550                       ptr = new_seginfo (mode, insn, bb->index, live_now);
 551                       add_seginfo (info + bb->index, ptr);
 552                       bitmap_clear_bit (transp[bb->index], j);
 553                     }
 554 #ifdef MODE_AFTER
 555                   last_mode = MODE_AFTER (e, last_mode, insn);
 556 #endif
 557                   /* Update LIVE_NOW.  */
 558                   for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
 559                     if (REG_NOTE_KIND (link) == REG_DEAD)
 560                       reg_dies (XEXP (link, 0), &live_now);
 561
 562                   note_stores (PATTERN (insn), reg_becomes_live, &live_now);
 563                   for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
 564                     if (REG_NOTE_KIND (link) == REG_UNUSED)
 565                       reg_dies (XEXP (link, 0), &live_now);
 566                 }
 567             }
 568
 569           info[bb->index].computing = last_mode;
 570           /* Check for blocks without ANY mode requirements.
 571              N.B. because of MODE_AFTER, last_mode might still be different
 572              from no_mode.  */
 573           if (!any_set_required)
 574             {
 575               ptr = new_seginfo (no_mode, BB_END (bb), bb->index, live_now);
 576               add_seginfo (info + bb->index, ptr);
 577             }
 578         }
 579 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 580       {
 581         int mode = MODE_ENTRY (e);
 582
 583         if (mode != no_mode)
 584           {
 585             bb = post_entry;
 586
 587             /* By always making this nontransparent, we save
 588                an extra check in make_preds_opaque.  We also
 589                need this to avoid confusing pre_edge_lcm when
 590                antic is cleared but transp and comp are set.  */
 591             bitmap_clear_bit (transp[bb->index], j);
 592
 593             /* Insert a fake computing definition of MODE into entry
 594                blocks which compute no mode. This represents the mode on
 595                entry.  */
 596             info[bb->index].computing = mode;
 597
 598             if (pre_exit)
 599               info[pre_exit->index].seginfo->mode = MODE_EXIT (e);
 600           }
 601       }
 602 #endif /* NORMAL_MODE */
 603     }
 604
 605   kill = sbitmap_vector_alloc (last_basic_block, n_entities);
 606   for (i = 0; i < max_num_modes; i++)
 607     {
 608       int current_mode[N_ENTITIES];
 609       sbitmap *del;
 610       sbitmap *insert;
 611
 612       /* Set the anticipatable and computing arrays.  */
 613       bitmap_vector_clear (antic, last_basic_block);
 614       bitmap_vector_clear (comp, last_basic_block);
 615       for (j = n_entities - 1; j >= 0; j--)
 616         {
 617           int m = current_mode[j] = MODE_PRIORITY_TO_MODE (entity_map[j], i);
 618           struct bb_info *info = bb_info[j];
 619
 620           FOR_EACH_BB (bb)
 621             {
 622               if (info[bb->index].seginfo->mode == m)
 623                 bitmap_set_bit (antic[bb->index], j);
 624
 625               if (info[bb->index].computing == m)
 626                 bitmap_set_bit (comp[bb->index], j);
 627             }
 628         }
 629
 630       /* Calculate the optimal locations for the
 631          placement mode switches to modes with priority I.  */
 632
 633       FOR_EACH_BB (bb)
 634         bitmap_not (kill[bb->index], transp[bb->index]);
 635       edge_list = pre_edge_lcm (n_entities, transp, comp, antic,
 636                                 kill, &insert, &del);
 637
 638       for (j = n_entities - 1; j >= 0; j--)
 639         {
 640           /* Insert all mode sets that have been inserted by lcm.  */
 641           int no_mode = num_modes[entity_map[j]];
 642
 643           /* Wherever we have moved a mode setting upwards in the flow graph,
 644              the blocks between the new setting site and the now redundant
 645              computation ceases to be transparent for any lower-priority
 646              mode of the same entity.  First set the aux field of each
 647              insertion site edge non-transparent, then propagate the new
 648              non-transparency from the redundant computation upwards till
 649              we hit an insertion site or an already non-transparent block.  */
 650           for (e = NUM_EDGES (edge_list) - 1; e >= 0; e--)
 651             {
 652               edge eg = INDEX_EDGE (edge_list, e);
 653               int mode;
 654               basic_block src_bb;
 655               HARD_REG_SET live_at_edge;
 656               rtx mode_set;
 657
 658               eg->aux = 0;
 659
 660               if (! bitmap_bit_p (insert[e], j))
 661                 continue;
 662
 663               eg->aux = (void *)1;
 664
 665               mode = current_mode[j];
 666               src_bb = eg->src;
 667
 668               REG_SET_TO_HARD_REG_SET (live_at_edge, df_get_live_out (src_bb));
 669
 670               start_sequence ();
 671               EMIT_MODE_SET (entity_map[j], mode, live_at_edge);
 672               mode_set = get_insns ();
 673               end_sequence ();
 674
 675               /* Do not bother to insert empty sequence.  */
 676               if (mode_set == NULL_RTX)
 677                 continue;
 678
 679               /* We should not get an abnormal edge here.  */
 680               gcc_assert (! (eg->flags & EDGE_ABNORMAL));
 681
 682               need_commit = 1;
 683               insert_insn_on_edge (mode_set, eg);
 684             }
 685
 686           FOR_EACH_BB_REVERSE (bb)
 687             if (bitmap_bit_p (del[bb->index], j))
 688               {
 689                 make_preds_opaque (bb, j);
 690                 /* Cancel the 'deleted' mode set.  */
 691                 bb_info[j][bb->index].seginfo->mode = no_mode;
 692               }
 693         }
 694
 695       sbitmap_vector_free (del);
 696       sbitmap_vector_free (insert);
 697       clear_aux_for_edges ();
 698       free_edge_list (edge_list);
 699     }
 700
 701   /* Now output the remaining mode sets in all the segments.  */
 702   for (j = n_entities - 1; j >= 0; j--)
 703     {
 704       int no_mode = num_modes[entity_map[j]];
 705
 706       FOR_EACH_BB_REVERSE (bb)
 707         {
 708           struct seginfo *ptr, *next;
 709           for (ptr = bb_info[j][bb->index].seginfo; ptr; ptr = next)
 710             {
 711               next = ptr->next;
 712               if (ptr->mode != no_mode)
 713                 {
 714                   rtx mode_set;
 715
 716                   start_sequence ();
 717                   EMIT_MODE_SET (entity_map[j], ptr->mode, ptr->regs_live);
 718                   mode_set = get_insns ();
 719                   end_sequence ();
 720
 721                   /* Insert MODE_SET only if it is nonempty.  */
 722                   if (mode_set != NULL_RTX)
 723                     {
 724                       emitted = true;
 725                       if (NOTE_INSN_BASIC_BLOCK_P (ptr->insn_ptr))
 726                         emit_insn_after (mode_set, ptr->insn_ptr);
 727                       else
 728                         emit_insn_before (mode_set, ptr->insn_ptr);
 729                     }
 730                 }
 731
 732               free (ptr);
 733             }
 734         }
 735
 736       free (bb_info[j]);
 737     }
 738
 739   /* Finished. Free up all the things we've allocated.  */
 740   sbitmap_vector_free (kill);
 741   sbitmap_vector_free (antic);
 742   sbitmap_vector_free (transp);
 743   sbitmap_vector_free (comp);
 744
 745   if (need_commit)
 746     commit_edge_insertions ();
 747
 748 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 749   cleanup_cfg (CLEANUP_NO_INSN_DEL);
 750 #else
 751   if (!need_commit && !emitted)
 752     return 0;
 753 #endif
 754
 755   return 1;
 756 }
 757
 758 #endif /* OPTIMIZE_MODE_SWITCHING */
 759 \f
 760 static bool
 761 gate_mode_switching (void)
 762 {
 763 #ifdef OPTIMIZE_MODE_SWITCHING
 764   return true;
 765 #else
 766   return false;
 767 #endif
 768 }
 769
 770 static unsigned int
 771 rest_of_handle_mode_switching (void)
 772 {
 773 #ifdef OPTIMIZE_MODE_SWITCHING
 774   optimize_mode_switching ();
 775 #endif /* OPTIMIZE_MODE_SWITCHING */
 776   return 0;
 777 }
 778
 779
 780 struct rtl_opt_pass pass_mode_switching =
 781 {
 782  {
 783   RTL_PASS,
 784   "mode_sw",                            /* name */
 785   OPTGROUP_NONE,                        /* optinfo_flags */
 786   gate_mode_switching,                  /* gate */
 787   rest_of_handle_mode_switching,        /* execute */
 788   NULL,                                 /* sub */
 789   NULL,                                 /* next */
 790   0,                                    /* static_pass_number */
 791   TV_MODE_SWITCH,                       /* tv_id */
 792   0,                                    /* properties_required */
 793   0,                                    /* properties_provided */
 794   0,                                    /* properties_destroyed */
 795   0,                                    /* todo_flags_start */
 796   TODO_df_finish | TODO_verify_rtl_sharing |
 797   0                                     /* todo_flags_finish */
 798  }
 799 };