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_FOR_FN (cfun)->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_FOR_FN (cfun)->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             bool short_block = false;
 233             bool multi_reg_return = false;
 234             bool forced_late_switch = false;
 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 = true;
 255                         break;
 256                       }
 257                     return_copy_pat = PATTERN (return_copy);
 258                     switch (GET_CODE (return_copy_pat))
 259                       {
 260                       case USE:
 261                         /* Skip USEs of multiple return registers.
 262                            __builtin_apply pattern is also handled here.  */
 263                         if (GET_CODE (XEXP (return_copy_pat, 0)) == REG
 264                             && (targetm.calls.function_value_regno_p
 265                                 (REGNO (XEXP (return_copy_pat, 0)))))
 266                           {
 267                             multi_reg_return = true;
 268                             last_insn = return_copy;
 269                             continue;
 270                           }
 271                         break;
 272
 273                       case ASM_OPERANDS:
 274                         /* Skip barrier insns.  */
 275                         if (!MEM_VOLATILE_P (return_copy_pat))
 276                           break;
 277
 278                         /* Fall through.  */
 279
 280                       case ASM_INPUT:
 281                       case UNSPEC_VOLATILE:
 282                         last_insn = return_copy;
 283                         continue;
 284
 285                       default:
 286                         break;
 287                       }
 288
 289                     /* If the return register is not (in its entirety)
 290                        likely spilled, the return copy might be
 291                        partially or completely optimized away.  */
 292                     return_copy_pat = single_set (return_copy);
 293                     if (!return_copy_pat)
 294                       {
 295                         return_copy_pat = PATTERN (return_copy);
 296                         if (GET_CODE (return_copy_pat) != CLOBBER)
 297                           break;
 298                         else if (!optimize)
 299                           {
 300                             /* This might be (clobber (reg [<result>]))
 301                                when not optimizing.  Then check if
 302                                the previous insn is the clobber for
 303                                the return register.  */
 304                             copy_reg = SET_DEST (return_copy_pat);
 305                             if (GET_CODE (copy_reg) == REG
 306                                 && !HARD_REGISTER_NUM_P (REGNO (copy_reg)))
 307                               {
 308                                 if (INSN_P (PREV_INSN (return_copy)))
 309                                   {
 310                                     return_copy = PREV_INSN (return_copy);
 311                                     return_copy_pat = PATTERN (return_copy);
 312                                     if (GET_CODE (return_copy_pat) != CLOBBER)
 313                                       break;
 314                                   }
 315                               }
 316                           }
 317                       }
 318                     copy_reg = SET_DEST (return_copy_pat);
 319                     if (GET_CODE (copy_reg) == REG)
 320                       copy_start = REGNO (copy_reg);
 321                     else if (GET_CODE (copy_reg) == SUBREG
 322                              && GET_CODE (SUBREG_REG (copy_reg)) == REG)
 323                       copy_start = REGNO (SUBREG_REG (copy_reg));
 324                     else
 325                       {
 326                         /* When control reaches end of non-void function,
 327                            there are no return copy insns at all.  This
 328                            avoids an ice on that invalid function.  */
 329                         if (ret_start + nregs == ret_end)
 330                           short_block = true;
 331                         break;
 332                       }
 333                     if (!targetm.calls.function_value_regno_p (copy_start))
 334                       copy_num = 0;
 335                     else
 336                       copy_num
 337                         = hard_regno_nregs[copy_start][GET_MODE (copy_reg)];
 338
 339                     /* If the return register is not likely spilled, - as is
 340                        the case for floating point on SH4 - then it might
 341                        be set by an arithmetic operation that needs a
 342                        different mode than the exit block.  */
 343                     for (j = n_entities - 1; j >= 0; j--)
 344                       {
 345                         int e = entity_map[j];
 346                         int mode = MODE_NEEDED (e, return_copy);
 347
 348                         if (mode != num_modes[e] && mode != MODE_EXIT (e))
 349                           break;
 350                       }
 351                     if (j >= 0)
 352                       {
 353                         /* __builtin_return emits a sequence of loads to all
 354                            return registers.  One of them might require
 355                            another mode than MODE_EXIT, even if it is
 356                            unrelated to the return value, so we want to put
 357                            the final mode switch after it.  */
 358                         if (multi_reg_return
 359                             && targetm.calls.function_value_regno_p
 360                                 (copy_start))
 361                           forced_late_switch = true;
 362
 363                         /* For the SH4, floating point loads depend on fpscr,
 364                            thus we might need to put the final mode switch
 365                            after the return value copy.  That is still OK,
 366                            because a floating point return value does not
 367                            conflict with address reloads.  */
 368                         if (copy_start >= ret_start
 369                             && copy_start + copy_num <= ret_end
 370                             && OBJECT_P (SET_SRC (return_copy_pat)))
 371                           forced_late_switch = true;
 372                         break;
 373                       }
 374                     if (copy_num == 0)
 375                       {
 376                         last_insn = return_copy;
 377                         continue;
 378                       }
 379
 380                     if (copy_start >= ret_start
 381                         && copy_start + copy_num <= ret_end)
 382                       nregs -= copy_num;
 383                     else if (!multi_reg_return
 384                              || !targetm.calls.function_value_regno_p
 385                                  (copy_start))
 386                       break;
 387                     last_insn = return_copy;
 388                   }
 389                 /* ??? Exception handling can lead to the return value
 390                    copy being already separated from the return value use,
 391                    as in  unwind-dw2.c .
 392                    Similarly, conditionally returning without a value,
 393                    and conditionally using builtin_return can lead to an
 394                    isolated use.  */
 395                 if (return_copy == BB_HEAD (src_bb))
 396                   {
 397                     short_block = true;
 398                     break;
 399                   }
 400                 last_insn = return_copy;
 401               }
 402             while (nregs);
 403
 404             /* If we didn't see a full return value copy, verify that there
 405                is a plausible reason for this.  If some, but not all of the
 406                return register is likely spilled, we can expect that there
 407                is a copy for the likely spilled part.  */
 408             gcc_assert (!nregs
 409                         || forced_late_switch
 410                         || short_block
 411                         || !(targetm.class_likely_spilled_p
 412                              (REGNO_REG_CLASS (ret_start)))
 413                         || (nregs
 414                             != hard_regno_nregs[ret_start][GET_MODE (ret_reg)])
 415                         /* For multi-hard-register floating point
 416                            values, sometimes the likely-spilled part
 417                            is ordinarily copied first, then the other
 418                            part is set with an arithmetic operation.
 419                            This doesn't actually cause reload
 420                            failures, so let it pass.  */
 421                         || (GET_MODE_CLASS (GET_MODE (ret_reg)) != MODE_INT
 422                             && nregs != 1));
 423
 424             if (!NOTE_INSN_BASIC_BLOCK_P (last_insn))
 425               {
 426                 before_return_copy
 427                   = emit_note_before (NOTE_INSN_DELETED, last_insn);
 428                 /* Instructions preceding LAST_INSN in the same block might
 429                    require a different mode than MODE_EXIT, so if we might
 430                    have such instructions, keep them in a separate block
 431                    from pre_exit.  */
 432                 src_bb = split_block (src_bb,
 433                                       PREV_INSN (before_return_copy))->dest;
 434               }
 435             else
 436               before_return_copy = last_insn;
 437             pre_exit = split_block (src_bb, before_return_copy)->src;
 438           }
 439         else
 440           {
 441             pre_exit = split_edge (eg);
 442           }
 443       }
 444
 445   return pre_exit;
 446 }
 447 #endif
 448
 449 /* Find all insns that need a particular mode setting, and insert the
 450    necessary mode switches.  Return true if we did work.  */
 451
 452 static int
 453 optimize_mode_switching (void)
 454 {
 455   rtx insn;
 456   int e;
 457   basic_block bb;
 458   int need_commit = 0;
 459   sbitmap *kill;
 460   struct edge_list *edge_list;
 461   static const int num_modes[] = NUM_MODES_FOR_MODE_SWITCHING;
 462 #define N_ENTITIES ARRAY_SIZE (num_modes)
 463   int entity_map[N_ENTITIES];
 464   struct bb_info *bb_info[N_ENTITIES];
 465   int i, j;
 466   int n_entities;
 467   int max_num_modes = 0;
 468   bool emitted ATTRIBUTE_UNUSED = false;
 469   basic_block post_entry ATTRIBUTE_UNUSED, pre_exit ATTRIBUTE_UNUSED;
 470
 471   for (e = N_ENTITIES - 1, n_entities = 0; e >= 0; e--)
 472     if (OPTIMIZE_MODE_SWITCHING (e))
 473       {
 474         int entry_exit_extra = 0;
 475
 476         /* Create the list of segments within each basic block.
 477            If NORMAL_MODE is defined, allow for two extra
 478            blocks split from the entry and exit block.  */
 479 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 480         entry_exit_extra = 3;
 481 #endif
 482         bb_info[n_entities]
 483           = XCNEWVEC (struct bb_info, last_basic_block + entry_exit_extra);
 484         entity_map[n_entities++] = e;
 485         if (num_modes[e] > max_num_modes)
 486           max_num_modes = num_modes[e];
 487       }
 488
 489   if (! n_entities)
 490     return 0;
 491
 492 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 493   /* Split the edge from the entry block, so that we can note that
 494      there NORMAL_MODE is supplied.  */
 495   post_entry = split_edge (single_succ_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun)));
 496   pre_exit = create_pre_exit (n_entities, entity_map, num_modes);
 497 #endif
 498
 499   df_analyze ();
 500
 501   /* Create the bitmap vectors.  */
 502
 503   antic = sbitmap_vector_alloc (last_basic_block, n_entities);
 504   transp = sbitmap_vector_alloc (last_basic_block, n_entities);
 505   comp = sbitmap_vector_alloc (last_basic_block, n_entities);
 506
 507   bitmap_vector_ones (transp, last_basic_block);
 508
 509   for (j = n_entities - 1; j >= 0; j--)
 510     {
 511       int e = entity_map[j];
 512       int no_mode = num_modes[e];
 513       struct bb_info *info = bb_info[j];
 514
 515       /* Determine what the first use (if any) need for a mode of entity E is.
 516          This will be the mode that is anticipatable for this block.
 517          Also compute the initial transparency settings.  */
 518       FOR_EACH_BB (bb)
 519         {
 520           struct seginfo *ptr;
 521           int last_mode = no_mode;
 522           bool any_set_required = false;
 523           HARD_REG_SET live_now;
 524
 525           REG_SET_TO_HARD_REG_SET (live_now, df_get_live_in (bb));
 526
 527           /* Pretend the mode is clobbered across abnormal edges.  */
 528           {
 529             edge_iterator ei;
 530             edge e;
 531             FOR_EACH_EDGE (e, ei, bb->preds)
 532               if (e->flags & EDGE_COMPLEX)
 533                 break;
 534             if (e)
 535               {
 536                 ptr = new_seginfo (no_mode, BB_HEAD (bb), bb->index, live_now);
 537                 add_seginfo (info + bb->index, ptr);
 538                 bitmap_clear_bit (transp[bb->index], j);
 539               }
 540           }
 541
 542           FOR_BB_INSNS (bb, insn)
 543             {
 544               if (INSN_P (insn))
 545                 {
 546                   int mode = MODE_NEEDED (e, insn);
 547                   rtx link;
 548
 549                   if (mode != no_mode && mode != last_mode)
 550                     {
 551                       any_set_required = true;
 552                       last_mode = mode;
 553                       ptr = new_seginfo (mode, insn, bb->index, live_now);
 554                       add_seginfo (info + bb->index, ptr);
 555                       bitmap_clear_bit (transp[bb->index], j);
 556                     }
 557 #ifdef MODE_AFTER
 558                   last_mode = MODE_AFTER (e, last_mode, insn);
 559 #endif
 560                   /* Update LIVE_NOW.  */
 561                   for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
 562                     if (REG_NOTE_KIND (link) == REG_DEAD)
 563                       reg_dies (XEXP (link, 0), &live_now);
 564
 565                   note_stores (PATTERN (insn), reg_becomes_live, &live_now);
 566                   for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
 567                     if (REG_NOTE_KIND (link) == REG_UNUSED)
 568                       reg_dies (XEXP (link, 0), &live_now);
 569                 }
 570             }
 571
 572           info[bb->index].computing = last_mode;
 573           /* Check for blocks without ANY mode requirements.
 574              N.B. because of MODE_AFTER, last_mode might still
 575              be different from no_mode, in which case we need to
 576              mark the block as nontransparent.  */
 577           if (!any_set_required)
 578             {
 579               ptr = new_seginfo (no_mode, BB_END (bb), bb->index, live_now);
 580               add_seginfo (info + bb->index, ptr);
 581               if (last_mode != no_mode)
 582                 bitmap_clear_bit (transp[bb->index], j);
 583             }
 584         }
 585 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 586       {
 587         int mode = MODE_ENTRY (e);
 588
 589         if (mode != no_mode)
 590           {
 591             bb = post_entry;
 592
 593             /* By always making this nontransparent, we save
 594                an extra check in make_preds_opaque.  We also
 595                need this to avoid confusing pre_edge_lcm when
 596                antic is cleared but transp and comp are set.  */
 597             bitmap_clear_bit (transp[bb->index], j);
 598
 599             /* Insert a fake computing definition of MODE into entry
 600                blocks which compute no mode. This represents the mode on
 601                entry.  */
 602             info[bb->index].computing = mode;
 603
 604             if (pre_exit)
 605               info[pre_exit->index].seginfo->mode = MODE_EXIT (e);
 606           }
 607       }
 608 #endif /* NORMAL_MODE */
 609     }
 610
 611   kill = sbitmap_vector_alloc (last_basic_block, n_entities);
 612   for (i = 0; i < max_num_modes; i++)
 613     {
 614       int current_mode[N_ENTITIES];
 615       sbitmap *del;
 616       sbitmap *insert;
 617
 618       /* Set the anticipatable and computing arrays.  */
 619       bitmap_vector_clear (antic, last_basic_block);
 620       bitmap_vector_clear (comp, last_basic_block);
 621       for (j = n_entities - 1; j >= 0; j--)
 622         {
 623           int m = current_mode[j] = MODE_PRIORITY_TO_MODE (entity_map[j], i);
 624           struct bb_info *info = bb_info[j];
 625
 626           FOR_EACH_BB (bb)
 627             {
 628               if (info[bb->index].seginfo->mode == m)
 629                 bitmap_set_bit (antic[bb->index], j);
 630
 631               if (info[bb->index].computing == m)
 632                 bitmap_set_bit (comp[bb->index], j);
 633             }
 634         }
 635
 636       /* Calculate the optimal locations for the
 637          placement mode switches to modes with priority I.  */
 638
 639       FOR_EACH_BB (bb)
 640         bitmap_not (kill[bb->index], transp[bb->index]);
 641       edge_list = pre_edge_lcm (n_entities, transp, comp, antic,
 642                                 kill, &insert, &del);
 643
 644       for (j = n_entities - 1; j >= 0; j--)
 645         {
 646           /* Insert all mode sets that have been inserted by lcm.  */
 647           int no_mode = num_modes[entity_map[j]];
 648
 649           /* Wherever we have moved a mode setting upwards in the flow graph,
 650              the blocks between the new setting site and the now redundant
 651              computation ceases to be transparent for any lower-priority
 652              mode of the same entity.  First set the aux field of each
 653              insertion site edge non-transparent, then propagate the new
 654              non-transparency from the redundant computation upwards till
 655              we hit an insertion site or an already non-transparent block.  */
 656           for (e = NUM_EDGES (edge_list) - 1; e >= 0; e--)
 657             {
 658               edge eg = INDEX_EDGE (edge_list, e);
 659               int mode;
 660               basic_block src_bb;
 661               HARD_REG_SET live_at_edge;
 662               rtx mode_set;
 663
 664               eg->aux = 0;
 665
 666               if (! bitmap_bit_p (insert[e], j))
 667                 continue;
 668
 669               eg->aux = (void *)1;
 670
 671               mode = current_mode[j];
 672               src_bb = eg->src;
 673
 674               REG_SET_TO_HARD_REG_SET (live_at_edge, df_get_live_out (src_bb));
 675
 676               rtl_profile_for_edge (eg);
 677               start_sequence ();
 678               EMIT_MODE_SET (entity_map[j], mode, live_at_edge);
 679               mode_set = get_insns ();
 680               end_sequence ();
 681               default_rtl_profile ();
 682
 683               /* Do not bother to insert empty sequence.  */
 684               if (mode_set == NULL_RTX)
 685                 continue;
 686
 687               /* We should not get an abnormal edge here.  */
 688               gcc_assert (! (eg->flags & EDGE_ABNORMAL));
 689
 690               need_commit = 1;
 691               insert_insn_on_edge (mode_set, eg);
 692             }
 693
 694           FOR_EACH_BB_REVERSE (bb)
 695             if (bitmap_bit_p (del[bb->index], j))
 696               {
 697                 make_preds_opaque (bb, j);
 698                 /* Cancel the 'deleted' mode set.  */
 699                 bb_info[j][bb->index].seginfo->mode = no_mode;
 700               }
 701         }
 702
 703       sbitmap_vector_free (del);
 704       sbitmap_vector_free (insert);
 705       clear_aux_for_edges ();
 706       free_edge_list (edge_list);
 707     }
 708
 709   /* Now output the remaining mode sets in all the segments.  */
 710   for (j = n_entities - 1; j >= 0; j--)
 711     {
 712       int no_mode = num_modes[entity_map[j]];
 713
 714       FOR_EACH_BB_REVERSE (bb)
 715         {
 716           struct seginfo *ptr, *next;
 717           for (ptr = bb_info[j][bb->index].seginfo; ptr; ptr = next)
 718             {
 719               next = ptr->next;
 720               if (ptr->mode != no_mode)
 721                 {
 722                   rtx mode_set;
 723
 724                   rtl_profile_for_bb (bb);
 725                   start_sequence ();
 726                   EMIT_MODE_SET (entity_map[j], ptr->mode, ptr->regs_live);
 727                   mode_set = get_insns ();
 728                   end_sequence ();
 729
 730                   /* Insert MODE_SET only if it is nonempty.  */
 731                   if (mode_set != NULL_RTX)
 732                     {
 733                       emitted = true;
 734                       if (NOTE_INSN_BASIC_BLOCK_P (ptr->insn_ptr))
 735                         emit_insn_after (mode_set, ptr->insn_ptr);
 736                       else
 737                         emit_insn_before (mode_set, ptr->insn_ptr);
 738                     }
 739
 740                   default_rtl_profile ();
 741                 }
 742
 743               free (ptr);
 744             }
 745         }
 746
 747       free (bb_info[j]);
 748     }
 749
 750   /* Finished. Free up all the things we've allocated.  */
 751   sbitmap_vector_free (kill);
 752   sbitmap_vector_free (antic);
 753   sbitmap_vector_free (transp);
 754   sbitmap_vector_free (comp);
 755
 756   if (need_commit)
 757     commit_edge_insertions ();
 758
 759 #if defined (MODE_ENTRY) && defined (MODE_EXIT)
 760   cleanup_cfg (CLEANUP_NO_INSN_DEL);
 761 #else
 762   if (!need_commit && !emitted)
 763     return 0;
 764 #endif
 765
 766   return 1;
 767 }
 768
 769 #endif /* OPTIMIZE_MODE_SWITCHING */
 770 \f
 771 static bool
 772 gate_mode_switching (void)
 773 {
 774 #ifdef OPTIMIZE_MODE_SWITCHING
 775   return true;
 776 #else
 777   return false;
 778 #endif
 779 }
 780
 781 static unsigned int
 782 rest_of_handle_mode_switching (void)
 783 {
 784 #ifdef OPTIMIZE_MODE_SWITCHING
 785   optimize_mode_switching ();
 786 #endif /* OPTIMIZE_MODE_SWITCHING */
 787   return 0;
 788 }
 789
 790
 791 namespace {
 792
 793 const pass_data pass_data_mode_switching =
 794 {
 795   RTL_PASS, /* type */
 796   "mode_sw", /* name */
 797   OPTGROUP_NONE, /* optinfo_flags */
 798   true, /* has_gate */
 799   true, /* has_execute */
 800   TV_MODE_SWITCH, /* tv_id */
 801   0, /* properties_required */
 802   0, /* properties_provided */
 803   0, /* properties_destroyed */
 804   0, /* todo_flags_start */
 805   ( TODO_df_finish | TODO_verify_rtl_sharing | 0 ), /* todo_flags_finish */
 806 };
 807
 808 class pass_mode_switching : public rtl_opt_pass
 809 {
 810 public:
 811   pass_mode_switching (gcc::context *ctxt)
 812     : rtl_opt_pass (pass_data_mode_switching, ctxt)
 813   {}
 814
 815   /* opt_pass methods: */
 816   /* The epiphany backend creates a second instance of this pass, so we need
 817      a clone method.  */
 818   opt_pass * clone () { return new pass_mode_switching (m_ctxt); }
 819   bool gate () { return gate_mode_switching (); }
 820   unsigned int execute () { return rest_of_handle_mode_switching (); }
 821
 822 }; // class pass_mode_switching
 823
 824 } // anon namespace
 825
 826 rtl_opt_pass *
 827 make_pass_mode_switching (gcc::context *ctxt)
 828 {
 829   return new pass_mode_switching (ctxt);
 830 }