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, 2012 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  34    (a) no longer valid because we've exceeded their range, (b) a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 "regs.h"
  52 #include "hard-reg-set.h"
  53 #include "flags.h"
  54 #include "function.h"
  55 #include "expr.h"
  56 #include "basic-block.h"
  57 #include "df.h"
  58 #include "except.h"
  59 #include "reload.h"
  60 #include "timevar.h"
  61 #include "tree-pass.h"
  62
  63 \f
  64 /* Turn STACK_GROWS_DOWNWARD into a boolean.  */
  65 #ifdef STACK_GROWS_DOWNWARD
  66 #undef STACK_GROWS_DOWNWARD
  67 #define STACK_GROWS_DOWNWARD 1
  68 #else
  69 #define STACK_GROWS_DOWNWARD 0
  70 #endif
  71
  72 /* This structure records two kinds of stack references between stack
  73    adjusting instructions: stack references in memory addresses for
  74    regular insns and all stack references for debug insns.  */
  75
  76 struct csa_reflist
  77 {
  78   HOST_WIDE_INT sp_offset;
  79   rtx insn, *ref;
  80   struct csa_reflist *next;
  81 };
  82
  83 static int stack_memref_p (rtx);
  84 static rtx single_set_for_csa (rtx);
  85 static void free_csa_reflist (struct csa_reflist *);
  86 static struct csa_reflist *record_one_stack_ref (rtx, rtx *,
  87                                                  struct csa_reflist *);
  88 static int try_apply_stack_adjustment (rtx, struct csa_reflist *,
  89                                        HOST_WIDE_INT, HOST_WIDE_INT);
  90 static void combine_stack_adjustments_for_block (basic_block);
  91 static int record_stack_refs (rtx *, void *);
  92
  93
  94 /* Main entry point for stack adjustment combination.  */
  95
  96 static void
  97 combine_stack_adjustments (void)
  98 {
  99   basic_block bb;
 100
 101   FOR_EACH_BB (bb)
 102     combine_stack_adjustments_for_block (bb);
 103 }
 104
 105 /* Recognize a MEM of the form (sp) or (plus sp const).  */
 106
 107 static int
 108 stack_memref_p (rtx x)
 109 {
 110   if (!MEM_P (x))
 111     return 0;
 112   x = XEXP (x, 0);
 113
 114   if (x == stack_pointer_rtx)
 115     return 1;
 116   if (GET_CODE (x) == PLUS
 117       && XEXP (x, 0) == stack_pointer_rtx
 118       && CONST_INT_P (XEXP (x, 1)))
 119     return 1;
 120
 121   return 0;
 122 }
 123
 124 /* Recognize either normal single_set or the hack in i386.md for
 125    tying fp and sp adjustments.  */
 126
 127 static rtx
 128 single_set_for_csa (rtx insn)
 129 {
 130   int i;
 131   rtx tmp = single_set (insn);
 132   if (tmp)
 133     return tmp;
 134
 135   if (!NONJUMP_INSN_P (insn)
 136       || GET_CODE (PATTERN (insn)) != PARALLEL)
 137     return NULL_RTX;
 138
 139   tmp = PATTERN (insn);
 140   if (GET_CODE (XVECEXP (tmp, 0, 0)) != SET)
 141     return NULL_RTX;
 142
 143   for (i = 1; i < XVECLEN (tmp, 0); ++i)
 144     {
 145       rtx this_rtx = XVECEXP (tmp, 0, i);
 146
 147       /* The special case is allowing a no-op set.  */
 148       if (GET_CODE (this_rtx) == SET
 149           && SET_SRC (this_rtx) == SET_DEST (this_rtx))
 150         ;
 151       else if (GET_CODE (this_rtx) != CLOBBER
 152                && GET_CODE (this_rtx) != USE)
 153         return NULL_RTX;
 154     }
 155
 156   return XVECEXP (tmp, 0, 0);
 157 }
 158
 159 /* Free the list of csa_reflist nodes.  */
 160
 161 static void
 162 free_csa_reflist (struct csa_reflist *reflist)
 163 {
 164   struct csa_reflist *next;
 165   for (; reflist ; reflist = next)
 166     {
 167       next = reflist->next;
 168       free (reflist);
 169     }
 170 }
 171
 172 /* Create a new csa_reflist node from the given stack reference.
 173    It is already known that the reference is either a MEM satisfying the
 174    predicate stack_memref_p or a REG representing the stack pointer.  */
 175
 176 static struct csa_reflist *
 177 record_one_stack_ref (rtx insn, rtx *ref, struct csa_reflist *next_reflist)
 178 {
 179   struct csa_reflist *ml;
 180
 181   ml = XNEW (struct csa_reflist);
 182
 183   if (REG_P (*ref) || XEXP (*ref, 0) == stack_pointer_rtx)
 184     ml->sp_offset = 0;
 185   else
 186     ml->sp_offset = INTVAL (XEXP (XEXP (*ref, 0), 1));
 187
 188   ml->insn = insn;
 189   ml->ref = ref;
 190   ml->next = next_reflist;
 191
 192   return ml;
 193 }
 194
 195 /* Attempt to apply ADJUST to the stack adjusting insn INSN, as well
 196    as each of the memories and stack references in REFLIST.  Return true
 197    on success.  */
 198
 199 static int
 200 try_apply_stack_adjustment (rtx insn, struct csa_reflist *reflist,
 201                             HOST_WIDE_INT new_adjust, HOST_WIDE_INT delta)
 202 {
 203   struct csa_reflist *ml;
 204   rtx set;
 205
 206   set = single_set_for_csa (insn);
 207   if (MEM_P (SET_DEST (set)))
 208     validate_change (insn, &SET_DEST (set),
 209                      replace_equiv_address (SET_DEST (set), stack_pointer_rtx),
 210                      1);
 211   else
 212     validate_change (insn, &XEXP (SET_SRC (set), 1), GEN_INT (new_adjust), 1);
 213
 214   for (ml = reflist; ml ; ml = ml->next)
 215     {
 216       rtx new_addr = plus_constant (Pmode, stack_pointer_rtx,
 217                                     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.  */
 418       /* TODO: Find another way to indicate to the dwarf2 code that we
 419          have not in fact lost an adjustment.  */
 420       test = emit_insn_before (gen_rtx_CLOBBER (VOIDmode, const0_rtx), insn);
 421     }
 422   add_reg_note (test, REG_ARGS_SIZE, XEXP (note, 0));
 423 }
 424
 425 /* Subroutine of combine_stack_adjustments, called for each basic block.  */
 426
 427 static void
 428 combine_stack_adjustments_for_block (basic_block bb)
 429 {
 430   HOST_WIDE_INT last_sp_adjust = 0;
 431   rtx last_sp_set = NULL_RTX;
 432   rtx last2_sp_set = NULL_RTX;
 433   struct csa_reflist *reflist = NULL;
 434   rtx insn, next, set;
 435   struct record_stack_refs_data data;
 436   bool end_of_block = false;
 437
 438   for (insn = BB_HEAD (bb); !end_of_block ; insn = next)
 439     {
 440       end_of_block = insn == BB_END (bb);
 441       next = NEXT_INSN (insn);
 442
 443       if (! INSN_P (insn))
 444         continue;
 445
 446       set = single_set_for_csa (insn);
 447       if (set)
 448         {
 449           rtx dest = SET_DEST (set);
 450           rtx src = SET_SRC (set);
 451
 452           /* Find constant additions to the stack pointer.  */
 453           if (dest == stack_pointer_rtx
 454               && GET_CODE (src) == PLUS
 455               && XEXP (src, 0) == stack_pointer_rtx
 456               && CONST_INT_P (XEXP (src, 1)))
 457             {
 458               HOST_WIDE_INT this_adjust = INTVAL (XEXP (src, 1));
 459
 460               /* If we've not seen an adjustment previously, record
 461                  it now and continue.  */
 462               if (! last_sp_set)
 463                 {
 464                   last_sp_set = insn;
 465                   last_sp_adjust = this_adjust;
 466                   continue;
 467                 }
 468
 469               /* If not all recorded refs can be adjusted, or the
 470                  adjustment is now too large for a constant addition,
 471                  we cannot merge the two stack adjustments.
 472
 473                  Also we need to be careful to not move stack pointer
 474                  such that we create stack accesses outside the allocated
 475                  area.  We can combine an allocation into the first insn,
 476                  or a deallocation into the second insn.  We can not
 477                  combine an allocation followed by a deallocation.
 478
 479                  The only somewhat frequent occurrence of the later is when
 480                  a function allocates a stack frame but does not use it.
 481                  For this case, we would need to analyze rtl stream to be
 482                  sure that allocated area is really unused.  This means not
 483                  only checking the memory references, but also all registers
 484                  or global memory references possibly containing a stack
 485                  frame address.
 486
 487                  Perhaps the best way to address this problem is to teach
 488                  gcc not to allocate stack for objects never used.  */
 489
 490               /* Combine an allocation into the first instruction.  */
 491               if (STACK_GROWS_DOWNWARD ? this_adjust <= 0 : this_adjust >= 0)
 492                 {
 493                   if (try_apply_stack_adjustment (last_sp_set, reflist,
 494                                                   last_sp_adjust + this_adjust,
 495                                                   this_adjust))
 496                     {
 497                       /* It worked!  */
 498                       maybe_move_args_size_note (last_sp_set, insn, false);
 499                       delete_insn (insn);
 500                       last_sp_adjust += this_adjust;
 501                       continue;
 502                     }
 503                 }
 504
 505               /* Otherwise we have a deallocation.  Do not combine with
 506                  a previous allocation.  Combine into the second insn.  */
 507               else if (STACK_GROWS_DOWNWARD
 508                        ? last_sp_adjust >= 0 : last_sp_adjust <= 0)
 509                 {
 510                   if (try_apply_stack_adjustment (insn, reflist,
 511                                                   last_sp_adjust + this_adjust,
 512                                                   -last_sp_adjust))
 513                     {
 514                       /* It worked!  */
 515                       maybe_move_args_size_note (insn, last_sp_set, true);
 516                       delete_insn (last_sp_set);
 517                       last_sp_set = insn;
 518                       last_sp_adjust += this_adjust;
 519                       free_csa_reflist (reflist);
 520                       reflist = NULL;
 521                       continue;
 522                     }
 523                 }
 524
 525               /* Combination failed.  Restart processing from here.  If
 526                  deallocation+allocation conspired to cancel, we can
 527                  delete the old deallocation insn.  */
 528               if (last_sp_set)
 529                 {
 530                   if (last_sp_adjust == 0)
 531                     {
 532                       maybe_move_args_size_note (insn, last_sp_set, true);
 533                       delete_insn (last_sp_set);
 534                     }
 535                   else
 536                     last2_sp_set = last_sp_set;
 537                 }
 538               free_csa_reflist (reflist);
 539               reflist = NULL;
 540               last_sp_set = insn;
 541               last_sp_adjust = this_adjust;
 542               continue;
 543             }
 544
 545           /* Find a store with pre-(dec|inc)rement or pre-modify of exactly
 546              the previous adjustment and turn it into a simple store.  This
 547              is equivalent to anticipating the stack adjustment so this must
 548              be an allocation.  */
 549           if (MEM_P (dest)
 550               && ((STACK_GROWS_DOWNWARD
 551                    ? (GET_CODE (XEXP (dest, 0)) == PRE_DEC
 552                       && last_sp_adjust
 553                          == (HOST_WIDE_INT) GET_MODE_SIZE (GET_MODE (dest)))
 554                    : (GET_CODE (XEXP (dest, 0)) == PRE_INC
 555                       && last_sp_adjust
 556                          == -(HOST_WIDE_INT) GET_MODE_SIZE (GET_MODE (dest))))
 557                   || ((STACK_GROWS_DOWNWARD
 558                        ? last_sp_adjust >= 0 : last_sp_adjust <= 0)
 559                       && GET_CODE (XEXP (dest, 0)) == PRE_MODIFY
 560                       && GET_CODE (XEXP (XEXP (dest, 0), 1)) == PLUS
 561                       && XEXP (XEXP (XEXP (dest, 0), 1), 0)
 562                          == stack_pointer_rtx
 563                       && GET_CODE (XEXP (XEXP (XEXP (dest, 0), 1), 1))
 564                          == CONST_INT
 565                       && INTVAL (XEXP (XEXP (XEXP (dest, 0), 1), 1))
 566                          == -last_sp_adjust))
 567               && XEXP (XEXP (dest, 0), 0) == stack_pointer_rtx
 568               && !reg_mentioned_p (stack_pointer_rtx, src)
 569               && memory_address_p (GET_MODE (dest), stack_pointer_rtx)
 570               && try_apply_stack_adjustment (insn, reflist, 0,
 571                                              -last_sp_adjust))
 572             {
 573               if (last2_sp_set)
 574                 maybe_move_args_size_note (last2_sp_set, last_sp_set, false);
 575               else
 576                 maybe_move_args_size_note (insn, last_sp_set, true);
 577               delete_insn (last_sp_set);
 578               free_csa_reflist (reflist);
 579               reflist = NULL;
 580               last_sp_set = NULL_RTX;
 581               last_sp_adjust = 0;
 582               continue;
 583             }
 584         }
 585
 586       data.insn = insn;
 587       data.reflist = reflist;
 588       if (!CALL_P (insn) && last_sp_set
 589           && !for_each_rtx (&PATTERN (insn), record_stack_refs, &data))
 590         {
 591            reflist = data.reflist;
 592            continue;
 593         }
 594       reflist = data.reflist;
 595
 596       /* Otherwise, we were not able to process the instruction.
 597          Do not continue collecting data across such a one.  */
 598       if (last_sp_set
 599           && (CALL_P (insn)
 600               || reg_mentioned_p (stack_pointer_rtx, PATTERN (insn))))
 601         {
 602           if (last_sp_set && last_sp_adjust == 0)
 603             {
 604               force_move_args_size_note (bb, last2_sp_set, last_sp_set);
 605               delete_insn (last_sp_set);
 606             }
 607           free_csa_reflist (reflist);
 608           reflist = NULL;
 609           last2_sp_set = NULL_RTX;
 610           last_sp_set = NULL_RTX;
 611           last_sp_adjust = 0;
 612         }
 613     }
 614
 615   if (last_sp_set && last_sp_adjust == 0)
 616     {
 617       force_move_args_size_note (bb, last2_sp_set, last_sp_set);
 618       delete_insn (last_sp_set);
 619     }
 620
 621   if (reflist)
 622     free_csa_reflist (reflist);
 623 }
 624 \f
 625
 626 static bool
 627 gate_handle_stack_adjustments (void)
 628 {
 629   return flag_combine_stack_adjustments;
 630 }
 631
 632 static unsigned int
 633 rest_of_handle_stack_adjustments (void)
 634 {
 635   cleanup_cfg (flag_crossjumping ? CLEANUP_CROSSJUMP : 0);
 636
 637   /* This is kind of a heuristic.  We need to run combine_stack_adjustments
 638      even for machines with possibly nonzero TARGET_RETURN_POPS_ARGS
 639      and ACCUMULATE_OUTGOING_ARGS.  We expect that only ports having
 640      push instructions will have popping returns.  */
 641 #ifndef PUSH_ROUNDING
 642   if (!ACCUMULATE_OUTGOING_ARGS)
 643 #endif
 644     {
 645       df_note_add_problem ();
 646       df_analyze ();
 647       combine_stack_adjustments ();
 648     }
 649   return 0;
 650 }
 651
 652 struct rtl_opt_pass pass_stack_adjustments =
 653 {
 654  {
 655   RTL_PASS,
 656   "csa",                                /* name */
 657   gate_handle_stack_adjustments,        /* gate */
 658   rest_of_handle_stack_adjustments,     /* execute */
 659   NULL,                                 /* sub */
 660   NULL,                                 /* next */
 661   0,                                    /* static_pass_number */
 662   TV_COMBINE_STACK_ADJUST,              /* tv_id */
 663   0,                                    /* properties_required */
 664   0,                                    /* properties_provided */
 665   0,                                    /* properties_destroyed */
 666   0,                                    /* todo_flags_start */
 667   TODO_df_finish | TODO_verify_rtl_sharing |
 668   TODO_ggc_collect,                     /* todo_flags_finish */
 669  }
 670 };