gcc/combine-stack-adj.c

   1 /* Combine stack adjustments.
   2    Copyright (C) 1987, 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997,
   3    1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
   4    2010 Free Software Foundation, Inc.
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify it under
   9 the terms of the GNU General Public License as published by the Free
  10 Software Foundation; either version 3, or (at your option) any later
  11 version.
  12
  13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  15 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  16 for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GCC; see the file COPYING3.  If not see
  20 <http://www.gnu.org/licenses/>.  */
  21
  22 /* Track stack adjustments and stack memory references.  Attempt to
  23    reduce the number of stack adjustments by back-propagating across
  24    the memory references.
  25
  26    This is intended primarily for use with targets that do not define
  27    ACCUMULATE_OUTGOING_ARGS.  It is of significantly more value to
  28    targets that define PREFERRED_STACK_BOUNDARY more aligned than
  29    STACK_BOUNDARY (e.g. x86), or if not all registers can be pushed
  30    (e.g. x86 fp regs) which would ordinarily have to be implemented
  31    as a sub/mov pair due to restrictions in calls.c.
  32
  33    Propagation stops when any of the insns that need adjusting are
  34    (a) no longer valid because we've exceeded their range, (b) a
  35    non-trivial push instruction, or (c) a call instruction.
  36
  37    Restriction B is based on the assumption that push instructions
  38    are smaller or faster.  If a port really wants to remove all
  39    pushes, it should have defined ACCUMULATE_OUTGOING_ARGS.  The
  40    one exception that is made is for an add immediately followed
  41    by a push.  */
  42
  43 #include "config.h"
  44 #include "system.h"
  45 #include "coretypes.h"
  46 #include "tm.h"
  47 #include "rtl.h"
  48 #include "tm_p.h"
  49 #include "insn-config.h"
  50 #include "recog.h"
  51 #include "output.h"
  52 #include "regs.h"
  53 #include "hard-reg-set.h"
  54 #include "flags.h"
  55 #include "function.h"
  56 #include "expr.h"
  57 #include "basic-block.h"
  58 #include "df.h"
  59 #include "except.h"
  60 #include "reload.h"
  61 #include "timevar.h"
  62 #include "tree-pass.h"
  63
  64 \f
  65 /* Turn STACK_GROWS_DOWNWARD into a boolean.  */
  66 #ifdef STACK_GROWS_DOWNWARD
  67 #undef STACK_GROWS_DOWNWARD
  68 #define STACK_GROWS_DOWNWARD 1
  69 #else
  70 #define STACK_GROWS_DOWNWARD 0
  71 #endif
  72
  73 /* This structure records two kinds of stack references between stack
  74    adjusting instructions: stack references in memory addresses for
  75    regular insns and all stack references for debug insns.  */
  76
  77 struct csa_reflist
  78 {
  79   HOST_WIDE_INT sp_offset;
  80   rtx insn, *ref;
  81   struct csa_reflist *next;
  82 };
  83
  84 static int stack_memref_p (rtx);
  85 static rtx single_set_for_csa (rtx);
  86 static void free_csa_reflist (struct csa_reflist *);
  87 static struct csa_reflist *record_one_stack_ref (rtx, rtx *,
  88                                                  struct csa_reflist *);
  89 static int try_apply_stack_adjustment (rtx, struct csa_reflist *,
  90                                        HOST_WIDE_INT, HOST_WIDE_INT);
  91 static void combine_stack_adjustments_for_block (basic_block);
  92 static int record_stack_refs (rtx *, void *);
  93
  94
  95 /* Main entry point for stack adjustment combination.  */
  96
  97 static void
  98 combine_stack_adjustments (void)
  99 {
 100   basic_block bb;
 101
 102   FOR_EACH_BB (bb)
 103     combine_stack_adjustments_for_block (bb);
 104 }
 105
 106 /* Recognize a MEM of the form (sp) or (plus sp const).  */
 107
 108 static int
 109 stack_memref_p (rtx x)
 110 {
 111   if (!MEM_P (x))
 112     return 0;
 113   x = XEXP (x, 0);
 114
 115   if (x == stack_pointer_rtx)
 116     return 1;
 117   if (GET_CODE (x) == PLUS
 118       && XEXP (x, 0) == stack_pointer_rtx
 119       && CONST_INT_P (XEXP (x, 1)))
 120     return 1;
 121
 122   return 0;
 123 }
 124
 125 /* Recognize either normal single_set or the hack in i386.md for
 126    tying fp and sp adjustments.  */
 127
 128 static rtx
 129 single_set_for_csa (rtx insn)
 130 {
 131   int i;
 132   rtx tmp = single_set (insn);
 133   if (tmp)
 134     return tmp;
 135
 136   if (!NONJUMP_INSN_P (insn)
 137       || GET_CODE (PATTERN (insn)) != PARALLEL)
 138     return NULL_RTX;
 139
 140   tmp = PATTERN (insn);
 141   if (GET_CODE (XVECEXP (tmp, 0, 0)) != SET)
 142     return NULL_RTX;
 143
 144   for (i = 1; i < XVECLEN (tmp, 0); ++i)
 145     {
 146       rtx this_rtx = XVECEXP (tmp, 0, i);
 147
 148       /* The special case is allowing a no-op set.  */
 149       if (GET_CODE (this_rtx) == SET
 150           && SET_SRC (this_rtx) == SET_DEST (this_rtx))
 151         ;
 152       else if (GET_CODE (this_rtx) != CLOBBER
 153                && GET_CODE (this_rtx) != USE)
 154         return NULL_RTX;
 155     }
 156
 157   return XVECEXP (tmp, 0, 0);
 158 }
 159
 160 /* Free the list of csa_reflist nodes.  */
 161
 162 static void
 163 free_csa_reflist (struct csa_reflist *reflist)
 164 {
 165   struct csa_reflist *next;
 166   for (; reflist ; reflist = next)
 167     {
 168       next = reflist->next;
 169       free (reflist);
 170     }
 171 }
 172
 173 /* Create a new csa_reflist node from the given stack reference.
 174    It is already known that the reference is either a MEM satisfying the
 175    predicate stack_memref_p or a REG representing the stack pointer.  */
 176
 177 static struct csa_reflist *
 178 record_one_stack_ref (rtx insn, rtx *ref, struct csa_reflist *next_reflist)
 179 {
 180   struct csa_reflist *ml;
 181
 182   ml = XNEW (struct csa_reflist);
 183
 184   if (REG_P (*ref) || XEXP (*ref, 0) == stack_pointer_rtx)
 185     ml->sp_offset = 0;
 186   else
 187     ml->sp_offset = INTVAL (XEXP (XEXP (*ref, 0), 1));
 188
 189   ml->insn = insn;
 190   ml->ref = ref;
 191   ml->next = next_reflist;
 192
 193   return ml;
 194 }
 195
 196 /* Attempt to apply ADJUST to the stack adjusting insn INSN, as well
 197    as each of the memories and stack references in REFLIST.  Return true
 198    on success.  */
 199
 200 static int
 201 try_apply_stack_adjustment (rtx insn, struct csa_reflist *reflist,
 202                             HOST_WIDE_INT new_adjust, HOST_WIDE_INT delta)
 203 {
 204   struct csa_reflist *ml;
 205   rtx set;
 206
 207   set = single_set_for_csa (insn);
 208   if (MEM_P (SET_DEST (set)))
 209     validate_change (insn, &SET_DEST (set),
 210                      replace_equiv_address (SET_DEST (set), stack_pointer_rtx),
 211                      1);
 212   else
 213     validate_change (insn, &XEXP (SET_SRC (set), 1), GEN_INT (new_adjust), 1);
 214
 215   for (ml = reflist; ml ; ml = ml->next)
 216     {
 217       rtx new_addr = plus_constant (stack_pointer_rtx, ml->sp_offset - delta);
 218       rtx new_val;
 219
 220       if (MEM_P (*ml->ref))
 221         new_val = replace_equiv_address_nv (*ml->ref, new_addr);
 222       else if (GET_MODE (*ml->ref) == GET_MODE (stack_pointer_rtx))
 223         new_val = new_addr;
 224       else
 225         new_val = lowpart_subreg (GET_MODE (*ml->ref), new_addr,
 226                                   GET_MODE (new_addr));
 227       validate_change (ml->insn, ml->ref, new_val, 1);
 228     }
 229
 230   if (apply_change_group ())
 231     {
 232       /* Succeeded.  Update our knowledge of the stack references.  */
 233       for (ml = reflist; ml ; ml = ml->next)
 234         ml->sp_offset -= delta;
 235
 236       return 1;
 237     }
 238   else
 239     return 0;
 240 }
 241
 242 /* Called via for_each_rtx and used to record all stack memory and other
 243    references in the insn and discard all other stack pointer references.  */
 244 struct record_stack_refs_data
 245 {
 246   rtx insn;
 247   struct csa_reflist *reflist;
 248 };
 249
 250 static int
 251 record_stack_refs (rtx *xp, void *data)
 252 {
 253   rtx x = *xp;
 254   struct record_stack_refs_data *d =
 255     (struct record_stack_refs_data *) data;
 256   if (!x)
 257     return 0;
 258   switch (GET_CODE (x))
 259     {
 260     case MEM:
 261       if (!reg_mentioned_p (stack_pointer_rtx, x))
 262         return -1;
 263       /* We are not able to handle correctly all possible memrefs containing
 264          stack pointer, so this check is necessary.  */
 265       if (stack_memref_p (x))
 266         {
 267           d->reflist = record_one_stack_ref (d->insn, xp, d->reflist);
 268           return -1;
 269         }
 270       /* Try harder for DEBUG_INSNs, handle e.g. (mem (mem (sp + 16) + 4).  */
 271       return !DEBUG_INSN_P (d->insn);
 272     case REG:
 273       /* ??? We want be able to handle non-memory stack pointer
 274          references later.  For now just discard all insns referring to
 275          stack pointer outside mem expressions.  We would probably
 276          want to teach validate_replace to simplify expressions first.
 277
 278          We can't just compare with STACK_POINTER_RTX because the
 279          reference to the stack pointer might be in some other mode.
 280          In particular, an explicit clobber in an asm statement will
 281          result in a QImode clobber.
 282
 283          In DEBUG_INSNs, we want to replace all occurrences, otherwise
 284          they will cause -fcompare-debug failures.  */
 285       if (REGNO (x) == STACK_POINTER_REGNUM)
 286         {
 287           if (!DEBUG_INSN_P (d->insn))
 288             return 1;
 289           d->reflist = record_one_stack_ref (d->insn, xp, d->reflist);
 290           return -1;
 291         }
 292       break;
 293     default:
 294       break;
 295     }
 296   return 0;
 297 }
 298
 299 /* If INSN has a REG_ARGS_SIZE note, move it to LAST.
 300    AFTER is true iff LAST follows INSN in the instruction stream.  */
 301
 302 static void
 303 maybe_move_args_size_note (rtx last, rtx insn, bool after)
 304 {
 305   rtx note, last_note;
 306
 307   note = find_reg_note (insn, REG_ARGS_SIZE, NULL_RTX);
 308   if (note == NULL)
 309     return;
 310
 311   last_note = find_reg_note (last, REG_ARGS_SIZE, NULL_RTX);
 312   if (last_note)
 313     {
 314       /* The ARGS_SIZE notes are *not* cumulative.  They represent an
 315          absolute value, and the "most recent" note wins.  */
 316       if (!after)
 317         XEXP (last_note, 0) = XEXP (note, 0);
 318     }
 319   else
 320     add_reg_note (last, REG_ARGS_SIZE, XEXP (note, 0));
 321 }
 322
 323 /* Return the next (or previous) active insn within BB.  */
 324
 325 static rtx
 326 prev_active_insn_bb (basic_block bb, rtx insn)
 327 {
 328   for (insn = PREV_INSN (insn);
 329        insn != PREV_INSN (BB_HEAD (bb));
 330        insn = PREV_INSN (insn))
 331     if (active_insn_p (insn))
 332       return insn;
 333   return NULL_RTX;
 334 }
 335
 336 static rtx
 337 next_active_insn_bb (basic_block bb, rtx insn)
 338 {
 339   for (insn = NEXT_INSN (insn);
 340        insn != NEXT_INSN (BB_END (bb));
 341        insn = NEXT_INSN (insn))
 342     if (active_insn_p (insn))
 343       return insn;
 344   return NULL_RTX;
 345 }
 346
 347 /* If INSN has a REG_ARGS_SIZE note, if possible move it to PREV.  Otherwise
 348    search for a nearby candidate within BB where we can stick the note.  */
 349
 350 static void
 351 force_move_args_size_note (basic_block bb, rtx prev, rtx insn)
 352 {
 353   rtx note, test, next_candidate, prev_candidate;
 354
 355   /* If PREV exists, tail-call to the logic in the other function.  */
 356   if (prev)
 357     {
 358       maybe_move_args_size_note (prev, insn, false);
 359       return;
 360     }
 361
 362   /* First, make sure there's anything that needs doing.  */
 363   note = find_reg_note (insn, REG_ARGS_SIZE, NULL_RTX);
 364   if (note == NULL)
 365     return;
 366
 367   /* We need to find a spot between the previous and next exception points
 368      where we can place the note and "properly" deallocate the arguments.  */
 369   next_candidate = prev_candidate = NULL;
 370
 371   /* It is often the case that we have insns in the order:
 372         call
 373         add sp (previous deallocation)
 374         sub sp (align for next arglist)
 375         push arg
 376      and the add/sub cancel.  Therefore we begin by searching forward.  */
 377
 378   test = insn;
 379   while ((test = next_active_insn_bb (bb, test)) != NULL)
 380     {
 381       /* Found an existing note: nothing to do.  */
 382       if (find_reg_note (test, REG_ARGS_SIZE, NULL_RTX))
 383         return;
 384       /* Found something that affects unwinding.  Stop searching.  */
 385       if (CALL_P (test) || !insn_nothrow_p (test))
 386         break;
 387       if (next_candidate == NULL)
 388         next_candidate = test;
 389     }
 390
 391   test = insn;
 392   while ((test = prev_active_insn_bb (bb, test)) != NULL)
 393     {
 394       rtx tnote;
 395       /* Found a place that seems logical to adjust the stack.  */
 396       tnote = find_reg_note (test, REG_ARGS_SIZE, NULL_RTX);
 397       if (tnote)
 398         {
 399           XEXP (tnote, 0) = XEXP (note, 0);
 400           return;
 401         }
 402       if (prev_candidate == NULL)
 403         prev_candidate = test;
 404       /* Found something that affects unwinding.  Stop searching.  */
 405       if (CALL_P (test) || !insn_nothrow_p (test))
 406         break;
 407     }
 408
 409   if (prev_candidate)
 410     test = prev_candidate;
 411   else if (next_candidate)
 412     test = next_candidate;
 413   else
 414     {
 415       /* ??? We *must* have a place, lest we ICE on the lost adjustment.
 416          Options are: dummy clobber insn, nop, or prevent the removal of
 417          the sp += 0 insn.  Defer that decision until we can prove this
 418          can actually happen.  */
 419       gcc_unreachable ();
 420     }
 421   add_reg_note (test, REG_ARGS_SIZE, XEXP (note, 0));
 422 }
 423
 424 /* Subroutine of combine_stack_adjustments, called for each basic block.  */
 425
 426 static void
 427 combine_stack_adjustments_for_block (basic_block bb)
 428 {
 429   HOST_WIDE_INT last_sp_adjust = 0;
 430   rtx last_sp_set = NULL_RTX;
 431   rtx last2_sp_set = NULL_RTX;
 432   struct csa_reflist *reflist = NULL;
 433   rtx insn, next, set;
 434   struct record_stack_refs_data data;
 435   bool end_of_block = false;
 436
 437   for (insn = BB_HEAD (bb); !end_of_block ; insn = next)
 438     {
 439       end_of_block = insn == BB_END (bb);
 440       next = NEXT_INSN (insn);
 441
 442       if (! INSN_P (insn))
 443         continue;
 444
 445       set = single_set_for_csa (insn);
 446       if (set)
 447         {
 448           rtx dest = SET_DEST (set);
 449           rtx src = SET_SRC (set);
 450
 451           /* Find constant additions to the stack pointer.  */
 452           if (dest == stack_pointer_rtx
 453               && GET_CODE (src) == PLUS
 454               && XEXP (src, 0) == stack_pointer_rtx
 455               && CONST_INT_P (XEXP (src, 1)))
 456             {
 457               HOST_WIDE_INT this_adjust = INTVAL (XEXP (src, 1));
 458
 459               /* If we've not seen an adjustment previously, record
 460                  it now and continue.  */
 461               if (! last_sp_set)
 462                 {
 463                   last_sp_set = insn;
 464                   last_sp_adjust = this_adjust;
 465                   continue;
 466                 }
 467
 468               /* If not all recorded refs can be adjusted, or the
 469                  adjustment is now too large for a constant addition,
 470                  we cannot merge the two stack adjustments.
 471
 472                  Also we need to be careful to not move stack pointer
 473                  such that we create stack accesses outside the allocated
 474                  area.  We can combine an allocation into the first insn,
 475                  or a deallocation into the second insn.  We can not
 476                  combine an allocation followed by a deallocation.
 477
 478                  The only somewhat frequent occurrence of the later is when
 479                  a function allocates a stack frame but does not use it.
 480                  For this case, we would need to analyze rtl stream to be
 481                  sure that allocated area is really unused.  This means not
 482                  only checking the memory references, but also all registers
 483                  or global memory references possibly containing a stack
 484                  frame address.
 485
 486                  Perhaps the best way to address this problem is to teach
 487                  gcc not to allocate stack for objects never used.  */
 488
 489               /* Combine an allocation into the first instruction.  */
 490               if (STACK_GROWS_DOWNWARD ? this_adjust <= 0 : this_adjust >= 0)
 491                 {
 492                   if (try_apply_stack_adjustment (last_sp_set, reflist,
 493                                                   last_sp_adjust + this_adjust,
 494                                                   this_adjust))
 495                     {
 496                       /* It worked!  */
 497                       maybe_move_args_size_note (last_sp_set, insn, false);
 498                       delete_insn (insn);
 499                       last_sp_adjust += this_adjust;
 500                       continue;
 501                     }
 502                 }
 503
 504               /* Otherwise we have a deallocation.  Do not combine with
 505                  a previous allocation.  Combine into the second insn.  */
 506               else if (STACK_GROWS_DOWNWARD
 507                        ? last_sp_adjust >= 0 : last_sp_adjust <= 0)
 508                 {
 509                   if (try_apply_stack_adjustment (insn, reflist,
 510                                                   last_sp_adjust + this_adjust,
 511                                                   -last_sp_adjust))
 512                     {
 513                       /* It worked!  */
 514                       maybe_move_args_size_note (insn, last_sp_set, true);
 515                       delete_insn (last_sp_set);
 516                       last_sp_set = insn;
 517                       last_sp_adjust += this_adjust;
 518                       free_csa_reflist (reflist);
 519                       reflist = NULL;
 520                       continue;
 521                     }
 522                 }
 523
 524               /* Combination failed.  Restart processing from here.  If
 525                  deallocation+allocation conspired to cancel, we can
 526                  delete the old deallocation insn.  */
 527               if (last_sp_set)
 528                 {
 529                   if (last_sp_adjust == 0)
 530                     {
 531                       maybe_move_args_size_note (insn, last_sp_set, true);
 532                       delete_insn (last_sp_set);
 533                     }
 534                   else
 535                     last2_sp_set = last_sp_set;
 536                 }
 537               free_csa_reflist (reflist);
 538               reflist = NULL;
 539               last_sp_set = insn;
 540               last_sp_adjust = this_adjust;
 541               continue;
 542             }
 543
 544           /* Find a store with pre-(dec|inc)rement or pre-modify of exactly
 545              the previous adjustment and turn it into a simple store.  This
 546              is equivalent to anticipating the stack adjustment so this must
 547              be an allocation.  */
 548           if (MEM_P (dest)
 549               && ((STACK_GROWS_DOWNWARD
 550                    ? (GET_CODE (XEXP (dest, 0)) == PRE_DEC
 551                       && last_sp_adjust
 552                          == (HOST_WIDE_INT) GET_MODE_SIZE (GET_MODE (dest)))
 553                    : (GET_CODE (XEXP (dest, 0)) == PRE_INC
 554                       && last_sp_adjust
 555                          == -(HOST_WIDE_INT) GET_MODE_SIZE (GET_MODE (dest))))
 556                   || ((STACK_GROWS_DOWNWARD
 557                        ? last_sp_adjust >= 0 : last_sp_adjust <= 0)
 558                       && GET_CODE (XEXP (dest, 0)) == PRE_MODIFY
 559                       && GET_CODE (XEXP (XEXP (dest, 0), 1)) == PLUS
 560                       && XEXP (XEXP (XEXP (dest, 0), 1), 0)
 561                          == stack_pointer_rtx
 562                       && GET_CODE (XEXP (XEXP (XEXP (dest, 0), 1), 1))
 563                          == CONST_INT
 564                       && INTVAL (XEXP (XEXP (XEXP (dest, 0), 1), 1))
 565                          == -last_sp_adjust))
 566               && XEXP (XEXP (dest, 0), 0) == stack_pointer_rtx
 567               && !reg_mentioned_p (stack_pointer_rtx, src)
 568               && memory_address_p (GET_MODE (dest), stack_pointer_rtx)
 569               && try_apply_stack_adjustment (insn, reflist, 0,
 570                                              -last_sp_adjust))
 571             {
 572               if (last2_sp_set)
 573                 maybe_move_args_size_note (last2_sp_set, last_sp_set, false);
 574               else
 575                 maybe_move_args_size_note (insn, last_sp_set, true);
 576               delete_insn (last_sp_set);
 577               free_csa_reflist (reflist);
 578               reflist = NULL;
 579               last_sp_set = NULL_RTX;
 580               last_sp_adjust = 0;
 581               continue;
 582             }
 583         }
 584
 585       data.insn = insn;
 586       data.reflist = reflist;
 587       if (!CALL_P (insn) && last_sp_set
 588           && !for_each_rtx (&PATTERN (insn), record_stack_refs, &data))
 589         {
 590            reflist = data.reflist;
 591            continue;
 592         }
 593       reflist = data.reflist;
 594
 595       /* Otherwise, we were not able to process the instruction.
 596          Do not continue collecting data across such a one.  */
 597       if (last_sp_set
 598           && (CALL_P (insn)
 599               || reg_mentioned_p (stack_pointer_rtx, PATTERN (insn))))
 600         {
 601           if (last_sp_set && last_sp_adjust == 0)
 602             {
 603               force_move_args_size_note (bb, last2_sp_set, last_sp_set);
 604               delete_insn (last_sp_set);
 605             }
 606           free_csa_reflist (reflist);
 607           reflist = NULL;
 608           last2_sp_set = NULL_RTX;
 609           last_sp_set = NULL_RTX;
 610           last_sp_adjust = 0;
 611         }
 612     }
 613
 614   if (last_sp_set && last_sp_adjust == 0)
 615     {
 616       force_move_args_size_note (bb, last2_sp_set, last_sp_set);
 617       delete_insn (last_sp_set);
 618     }
 619
 620   if (reflist)
 621     free_csa_reflist (reflist);
 622 }
 623 \f
 624
 625 static bool
 626 gate_handle_stack_adjustments (void)
 627 {
 628   return flag_combine_stack_adjustments;
 629 }
 630
 631 static unsigned int
 632 rest_of_handle_stack_adjustments (void)
 633 {
 634   cleanup_cfg (flag_crossjumping ? CLEANUP_CROSSJUMP : 0);
 635
 636   /* This is kind of a heuristic.  We need to run combine_stack_adjustments
 637      even for machines with possibly nonzero TARGET_RETURN_POPS_ARGS
 638      and ACCUMULATE_OUTGOING_ARGS.  We expect that only ports having
 639      push instructions will have popping returns.  */
 640 #ifndef PUSH_ROUNDING
 641   if (!ACCUMULATE_OUTGOING_ARGS)
 642 #endif
 643     {
 644       df_note_add_problem ();
 645       df_analyze ();
 646       combine_stack_adjustments ();
 647     }
 648   return 0;
 649 }
 650
 651 struct rtl_opt_pass pass_stack_adjustments =
 652 {
 653  {
 654   RTL_PASS,
 655   "csa",                                /* name */
 656   gate_handle_stack_adjustments,        /* gate */
 657   rest_of_handle_stack_adjustments,     /* execute */
 658   NULL,                                 /* sub */
 659   NULL,                                 /* next */
 660   0,                                    /* static_pass_number */
 661   TV_COMBINE_STACK_ADJUST,              /* tv_id */
 662   0,                                    /* properties_required */
 663   0,                                    /* properties_provided */
 664   0,                                    /* properties_destroyed */
 665   0,                                    /* todo_flags_start */
 666   TODO_df_finish | TODO_verify_rtl_sharing |
 667   TODO_ggc_collect,                     /* todo_flags_finish */
 668  }
 669 };