gcc/tree-optimize.c

   1 /* Top-level control of tree optimizations.
   2    Copyright 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
   3    Contributed by Diego Novillo <dnovillo@redhat.com>
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 2, or (at your option)
  10 any later version.
  11
  12 GCC is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING.  If not, write to
  19 the Free Software Foundation, 59 Temple Place - Suite 330,
  20 Boston, MA 02111-1307, USA.  */
  21
  22 #include "config.h"
  23 #include "system.h"
  24 #include "coretypes.h"
  25 #include "tm.h"
  26 #include "tree.h"
  27 #include "rtl.h"
  28 #include "tm_p.h"
  29 #include "hard-reg-set.h"
  30 #include "basic-block.h"
  31 #include "output.h"
  32 #include "expr.h"
  33 #include "diagnostic.h"
  34 #include "basic-block.h"
  35 #include "flags.h"
  36 #include "tree-flow.h"
  37 #include "tree-dump.h"
  38 #include "timevar.h"
  39 #include "function.h"
  40 #include "langhooks.h"
  41 #include "toplev.h"
  42 #include "flags.h"
  43 #include "cgraph.h"
  44 #include "tree-inline.h"
  45 #include "tree-mudflap.h"
  46 #include "tree-pass.h"
  47 #include "ggc.h"
  48 #include "cgraph.h"
  49 #include "graph.h"
  50
  51
  52 /* Global variables used to communicate with passes.  */
  53 int dump_flags;
  54 bitmap vars_to_rename;
  55 bool in_gimple_form;
  56
  57 /* The root of the compilation pass tree, once constructed.  */
  58 static struct tree_opt_pass *all_passes;
  59
  60 /* Pass: dump the gimplified, inlined, functions.  */
  61
  62 static struct tree_opt_pass pass_gimple =
  63 {
  64   "gimple",                             /* name */
  65   NULL,                                 /* gate */
  66   NULL,                                 /* execute */
  67   NULL,                                 /* sub */
  68   NULL,                                 /* next */
  69   0,                                    /* static_pass_number */
  70   0,                                    /* tv_id */
  71   0,                                    /* properties_required */
  72   PROP_gimple_any,                      /* properties_provided */
  73   0,                                    /* properties_destroyed */
  74   0,                                    /* todo_flags_start */
  75   TODO_dump_func,                       /* todo_flags_finish */
  76   0                                     /* letter */
  77 };
  78
  79 /* Gate: execute, or not, all of the non-trivial optimizations.  */
  80
  81 static bool
  82 gate_all_optimizations (void)
  83 {
  84   return (optimize >= 1
  85           /* Don't bother doing anything if the program has errors.  */
  86           && !(errorcount || sorrycount));
  87 }
  88
  89 static struct tree_opt_pass pass_all_optimizations =
  90 {
  91   NULL,                                 /* name */
  92   gate_all_optimizations,               /* gate */
  93   NULL,                                 /* execute */
  94   NULL,                                 /* sub */
  95   NULL,                                 /* next */
  96   0,                                    /* static_pass_number */
  97   0,                                    /* tv_id */
  98   0,                                    /* properties_required */
  99   0,                                    /* properties_provided */
 100   0,                                    /* properties_destroyed */
 101   0,                                    /* todo_flags_start */
 102   0,                                    /* todo_flags_finish */
 103   0                                     /* letter */
 104 };
 105
 106 /* Pass: cleanup the CFG just before expanding trees to RTL.
 107    This is just a round of label cleanups and case node grouping
 108    because after the tree optimizers have run such cleanups may
 109    be necessary.  */
 110
 111 static void
 112 execute_cleanup_cfg_post_optimizing (void)
 113 {
 114   cleanup_tree_cfg ();
 115   cleanup_dead_labels ();
 116   group_case_labels ();
 117 }
 118
 119 static struct tree_opt_pass pass_cleanup_cfg_post_optimizing =
 120 {
 121   "final_cleanup",                      /* name */
 122   NULL,                                 /* gate */
 123   execute_cleanup_cfg_post_optimizing,  /* execute */
 124   NULL,                                 /* sub */
 125   NULL,                                 /* next */
 126   0,                                    /* static_pass_number */
 127   0,                                    /* tv_id */
 128   PROP_cfg,                             /* properties_required */
 129   0,                                    /* properties_provided */
 130   0,                                    /* properties_destroyed */
 131   0,                                    /* todo_flags_start */
 132   TODO_dump_func,                                       /* todo_flags_finish */
 133   0                                     /* letter */
 134 };
 135
 136 /* Pass: do the actions required to finish with tree-ssa optimization
 137    passes.  */
 138
 139 static void
 140 execute_free_datastructures (void)
 141 {
 142   tree *chain;
 143
 144   /* ??? This isn't the right place for this.  Worse, it got computed
 145      more or less at random in various passes.  */
 146   free_dominance_info (CDI_DOMINATORS);
 147
 148   /* Emit gotos for implicit jumps.  */
 149   disband_implicit_edges ();
 150
 151   /* Remove the ssa structures.  Do it here since this includes statement
 152      annotations that need to be intact during disband_implicit_edges.  */
 153   delete_tree_ssa ();
 154
 155   /* Re-chain the statements from the blocks.  */
 156   chain = &DECL_SAVED_TREE (current_function_decl);
 157   *chain = alloc_stmt_list ();
 158
 159   /* And get rid of annotations we no longer need.  */
 160   delete_tree_cfg_annotations ();
 161 }
 162
 163 static struct tree_opt_pass pass_free_datastructures =
 164 {
 165   NULL,                                 /* name */
 166   NULL,                                 /* gate */
 167   execute_free_datastructures,                  /* execute */
 168   NULL,                                 /* sub */
 169   NULL,                                 /* next */
 170   0,                                    /* static_pass_number */
 171   0,                                    /* tv_id */
 172   PROP_cfg,                             /* properties_required */
 173   0,                                    /* properties_provided */
 174   0,                                    /* properties_destroyed */
 175   0,                                    /* todo_flags_start */
 176   0,                                    /* todo_flags_finish */
 177   0                                     /* letter */
 178 };
 179
 180
 181 /* Do the actions required to initialize internal data structures used
 182    in tree-ssa optimization passes.  */
 183
 184 static void
 185 execute_init_datastructures (void)
 186 {
 187   /* Allocate hash tables, arrays and other structures.  */
 188   init_tree_ssa ();
 189 }
 190
 191 static struct tree_opt_pass pass_init_datastructures =
 192 {
 193   NULL,                                 /* name */
 194   NULL,                                 /* gate */
 195   execute_init_datastructures,          /* execute */
 196   NULL,                                 /* sub */
 197   NULL,                                 /* next */
 198   0,                                    /* static_pass_number */
 199   0,                                    /* tv_id */
 200   PROP_cfg,                             /* properties_required */
 201   0,                                    /* properties_provided */
 202   0,                                    /* properties_destroyed */
 203   0,                                    /* todo_flags_start */
 204   0,                                    /* todo_flags_finish */
 205   0                                     /* letter */
 206 };
 207
 208 /* Iterate over the pass tree allocating dump file numbers.  We want
 209    to do this depth first, and independent of whether the pass is
 210    enabled or not.  */
 211
 212 static void
 213 register_one_dump_file (struct tree_opt_pass *pass, int n)
 214 {
 215   char *dot_name, *flag_name;
 216   char num[10];
 217
 218   /* See below in next_pass_1.  */
 219   num[0] = '\0';
 220   if (pass->static_pass_number != -1)
 221     sprintf (num, "%d", ((int) pass->static_pass_number < 0
 222                          ? 1 : pass->static_pass_number));
 223
 224   dot_name = concat (".", pass->name, num, NULL);
 225   if (pass->properties_provided & PROP_trees)
 226     {
 227       flag_name = concat ("tree-", pass->name, num, NULL);
 228       pass->static_pass_number = dump_register (dot_name, flag_name,
 229                                                 TDF_TREE, n + TDI_tree_all, 0);
 230     }
 231   else
 232     {
 233       flag_name = concat ("rtl-", pass->name, num, NULL);
 234       pass->static_pass_number = dump_register (dot_name, flag_name,
 235                                                 TDF_RTL, n, pass->letter);
 236     }
 237 }
 238
 239 static int
 240 register_dump_files (struct tree_opt_pass *pass, int properties)
 241 {
 242   static int n = 0;
 243   do
 244     {
 245       int new_properties;
 246       int pass_number;
 247
 248       pass->properties_required = properties;
 249       new_properties =
 250         (properties | pass->properties_provided) & ~pass->properties_destroyed;
 251
 252       /* Reset the counter when we reach RTL-based passes.  */
 253       if ((pass->properties_provided ^ pass->properties_required) & PROP_rtl)
 254         n = 0;
 255
 256       pass_number = n;
 257       if (pass->name)
 258         n++;
 259
 260       if (pass->sub)
 261         new_properties = register_dump_files (pass->sub, new_properties);
 262
 263       /* If we have a gate, combine the properties that we could have with
 264          and without the pass being examined.  */
 265       if (pass->gate)
 266         properties &= new_properties;
 267       else
 268         properties = new_properties;
 269
 270       pass->properties_provided = properties;
 271       if (pass->name)
 272         register_one_dump_file (pass, pass_number);
 273
 274       pass = pass->next;
 275     }
 276   while (pass);
 277
 278   return properties;
 279 }
 280
 281 /* Add a pass to the pass list. Duplicate the pass if it's already
 282    in the list.  */
 283
 284 static struct tree_opt_pass **
 285 next_pass_1 (struct tree_opt_pass **list, struct tree_opt_pass *pass)
 286 {
 287
 288   /* A nonzero static_pass_number indicates that the
 289      pass is already in the list.  */
 290   if (pass->static_pass_number)
 291     {
 292       struct tree_opt_pass *new;
 293
 294       new = xmalloc (sizeof (*new));
 295       memcpy (new, pass, sizeof (*new));
 296
 297       /* Indicate to register_dump_files that this pass has duplicates,
 298          and so it should rename the dump file.  The first instance will
 299          be -1, and be number of duplicates = -static_pass_number - 1.
 300          Subsequent instances will be > 0 and just the duplicate number.  */
 301       if (pass->name)
 302         {
 303           pass->static_pass_number -= 1;
 304           new->static_pass_number = -pass->static_pass_number;
 305         }
 306
 307       *list = new;
 308     }
 309   else
 310     {
 311       pass->static_pass_number = -1;
 312       *list = pass;
 313     }
 314
 315   return &(*list)->next;
 316
 317 }
 318
 319 /* Construct the pass tree.  */
 320
 321 void
 322 init_tree_optimization_passes (void)
 323 {
 324   struct tree_opt_pass **p;
 325
 326 #define NEXT_PASS(PASS)  (p = next_pass_1 (p, &PASS))
 327
 328   p = &all_passes;
 329   NEXT_PASS (pass_gimple);
 330   NEXT_PASS (pass_remove_useless_stmts);
 331   NEXT_PASS (pass_mudflap_1);
 332   NEXT_PASS (pass_lower_cf);
 333   NEXT_PASS (pass_lower_eh);
 334   NEXT_PASS (pass_build_cfg);
 335   NEXT_PASS (pass_pre_expand);
 336   NEXT_PASS (pass_tree_profile);
 337   NEXT_PASS (pass_init_datastructures);
 338   NEXT_PASS (pass_all_optimizations);
 339   NEXT_PASS (pass_warn_function_return);
 340   NEXT_PASS (pass_mudflap_2);
 341   NEXT_PASS (pass_free_datastructures);
 342   NEXT_PASS (pass_expand);
 343   NEXT_PASS (pass_rest_of_compilation);
 344   *p = NULL;
 345
 346   p = &pass_all_optimizations.sub;
 347   NEXT_PASS (pass_referenced_vars);
 348   NEXT_PASS (pass_maybe_create_global_var);
 349   NEXT_PASS (pass_build_ssa);
 350   NEXT_PASS (pass_may_alias);
 351   NEXT_PASS (pass_rename_ssa_copies);
 352   NEXT_PASS (pass_early_warn_uninitialized);
 353   NEXT_PASS (pass_dce);
 354   NEXT_PASS (pass_dominator);
 355   NEXT_PASS (pass_redundant_phi);
 356   NEXT_PASS (pass_dce);
 357   NEXT_PASS (pass_forwprop);
 358   NEXT_PASS (pass_phiopt);
 359   NEXT_PASS (pass_may_alias);
 360   NEXT_PASS (pass_tail_recursion);
 361   NEXT_PASS (pass_ch);
 362   NEXT_PASS (pass_profile);
 363   NEXT_PASS (pass_sra);
 364   NEXT_PASS (pass_rename_ssa_copies);
 365   NEXT_PASS (pass_dominator);
 366   NEXT_PASS (pass_redundant_phi);
 367   NEXT_PASS (pass_dce);
 368   NEXT_PASS (pass_dse);
 369   NEXT_PASS (pass_may_alias);
 370   NEXT_PASS (pass_forwprop);
 371   NEXT_PASS (pass_phiopt);
 372   NEXT_PASS (pass_ccp);
 373   NEXT_PASS (pass_redundant_phi);
 374   NEXT_PASS (pass_fold_builtins);
 375   /* FIXME: May alias should a TODO but for 4.0.0,
 376      we add may_alias right after fold builtins
 377      which can create arbitrary GIMPLE.  */
 378   NEXT_PASS (pass_may_alias);
 379   NEXT_PASS (pass_split_crit_edges);
 380   NEXT_PASS (pass_pre);
 381   NEXT_PASS (pass_loop);
 382   NEXT_PASS (pass_dominator);
 383   NEXT_PASS (pass_redundant_phi);
 384   /* FIXME: If DCE is not run before checking for uninitialized uses,
 385      we may get false warnings (e.g., testsuite/gcc.dg/uninit-5.c).
 386      However, this also causes us to misdiagnose cases that should be
 387      real warnings (e.g., testsuite/gcc.dg/pr18501.c).
 388
 389      To fix the false positives in uninit-5.c, we would have to
 390      account for the predicates protecting the set and the use of each
 391      variable.  Using a representation like Gated Single Assignment
 392      may help.  */
 393   NEXT_PASS (pass_late_warn_uninitialized);
 394   NEXT_PASS (pass_cd_dce);
 395   NEXT_PASS (pass_dse);
 396   NEXT_PASS (pass_forwprop);
 397   NEXT_PASS (pass_phiopt);
 398   NEXT_PASS (pass_tail_calls);
 399   NEXT_PASS (pass_del_ssa);
 400   NEXT_PASS (pass_nrv);
 401   NEXT_PASS (pass_remove_useless_vars);
 402   NEXT_PASS (pass_cleanup_cfg_post_optimizing);
 403   *p = NULL;
 404
 405   p = &pass_loop.sub;
 406   NEXT_PASS (pass_loop_init);
 407   NEXT_PASS (pass_lim);
 408   NEXT_PASS (pass_unswitch);
 409   NEXT_PASS (pass_record_bounds);
 410   NEXT_PASS (pass_linear_transform);
 411   NEXT_PASS (pass_iv_canon);
 412   NEXT_PASS (pass_if_conversion);
 413   NEXT_PASS (pass_vectorize);
 414   NEXT_PASS (pass_complete_unroll);
 415   NEXT_PASS (pass_iv_optimize);
 416   NEXT_PASS (pass_loop_done);
 417   *p = NULL;
 418
 419 #undef NEXT_PASS
 420
 421   /* Register the passes with the tree dump code.  */
 422   register_dump_files (all_passes, 0);
 423 }
 424
 425 static void execute_pass_list (struct tree_opt_pass *);
 426
 427 static unsigned int last_verified;
 428
 429 static void
 430 execute_todo (int properties, unsigned int flags)
 431 {
 432   if (flags & TODO_rename_vars)
 433     {
 434       rewrite_into_ssa (false);
 435       bitmap_clear (vars_to_rename);
 436     }
 437   if (flags & TODO_fix_def_def_chains)
 438     {
 439       rewrite_def_def_chains ();
 440       bitmap_clear (vars_to_rename);
 441     }
 442
 443   if (flags & TODO_cleanup_cfg)
 444     cleanup_tree_cfg ();
 445
 446   if ((flags & TODO_dump_func) && dump_file)
 447     {
 448       if (properties & PROP_trees)
 449         dump_function_to_file (current_function_decl,
 450                                dump_file, dump_flags);
 451       else if (properties & PROP_cfg)
 452         print_rtl_with_bb (dump_file, get_insns ());
 453       else
 454         print_rtl (dump_file, get_insns ());
 455
 456       /* Flush the file.  If verification fails, we won't be able to
 457          close the file before aborting.  */
 458       fflush (dump_file);
 459     }
 460
 461   if (flags & TODO_ggc_collect)
 462     ggc_collect ();
 463
 464 #ifdef ENABLE_CHECKING
 465   if (flags & TODO_verify_ssa)
 466     verify_ssa ();
 467   if (flags & TODO_verify_flow)
 468     verify_flow_info ();
 469   if (flags & TODO_verify_stmts)
 470     verify_stmts ();
 471 #endif
 472 }
 473
 474 static bool
 475 execute_one_pass (struct tree_opt_pass *pass)
 476 {
 477   unsigned int todo;
 478
 479   /* See if we're supposed to run this pass.  */
 480   if (pass->gate && !pass->gate ())
 481     return false;
 482
 483   /* Note that the folders should only create gimple expressions.
 484      This is a hack until the new folder is ready.  */
 485   in_gimple_form = (pass->properties_provided & PROP_trees) != 0;
 486
 487   /* Run pre-pass verification.  */
 488   todo = pass->todo_flags_start & ~last_verified;
 489   if (todo)
 490     execute_todo (pass->properties_required, todo);
 491
 492   /* If a dump file name is present, open it if enabled.  */
 493   if (pass->static_pass_number != -1)
 494     {
 495       bool initializing_dump = !dump_initialized_p (pass->static_pass_number);
 496       dump_file_name = get_dump_file_name (pass->static_pass_number);
 497       dump_file = dump_begin (pass->static_pass_number, &dump_flags);
 498       if (dump_file)
 499         {
 500           const char *dname, *aname;
 501           dname = lang_hooks.decl_printable_name (current_function_decl, 2);
 502           aname = (IDENTIFIER_POINTER
 503                    (DECL_ASSEMBLER_NAME (current_function_decl)));
 504           fprintf (dump_file, "\n;; Function %s (%s)%s\n\n", dname, aname,
 505              cfun->function_frequency == FUNCTION_FREQUENCY_HOT
 506              ? " (hot)"
 507              : cfun->function_frequency == FUNCTION_FREQUENCY_UNLIKELY_EXECUTED
 508              ? " (unlikely executed)"
 509              : "");
 510         }
 511
 512       if (initializing_dump
 513           && graph_dump_format != no_graph
 514           && (pass->properties_provided & (PROP_cfg | PROP_rtl))
 515               == (PROP_cfg | PROP_rtl))
 516         clean_graph_dump_file (dump_file_name);
 517     }
 518
 519   /* If a timevar is present, start it.  */
 520   if (pass->tv_id)
 521     timevar_push (pass->tv_id);
 522
 523   /* Do it!  */
 524   if (pass->execute)
 525     pass->execute ();
 526
 527   /* Stop timevar.  */
 528   if (pass->tv_id)
 529     timevar_pop (pass->tv_id);
 530
 531   if (dump_file
 532       && (pass->properties_provided & (PROP_cfg | PROP_rtl))
 533           == (PROP_cfg | PROP_rtl))
 534     print_rtl_with_bb (dump_file, get_insns ());
 535
 536   /* Run post-pass cleanup and verification.  */
 537   todo = pass->todo_flags_finish;
 538   last_verified = todo & TODO_verify_all;
 539   if (todo)
 540     execute_todo (pass->properties_provided, todo);
 541
 542   /* Flush and close dump file.  */
 543   if (dump_file_name)
 544     {
 545       free ((char *) dump_file_name);
 546       dump_file_name = NULL;
 547     }
 548   if (dump_file)
 549     {
 550       dump_end (pass->static_pass_number, dump_file);
 551       dump_file = NULL;
 552     }
 553
 554   return true;
 555 }
 556
 557 static void
 558 execute_pass_list (struct tree_opt_pass *pass)
 559 {
 560   do
 561     {
 562       if (execute_one_pass (pass) && pass->sub)
 563         execute_pass_list (pass->sub);
 564       pass = pass->next;
 565     }
 566   while (pass);
 567 }
 568 \f
 569
 570 /* Update recursively all inlined_to pointers of functions
 571    inlined into NODE to INLINED_TO.  */
 572 static void
 573 update_inlined_to_pointers (struct cgraph_node *node,
 574                             struct cgraph_node *inlined_to)
 575 {
 576   struct cgraph_edge *e;
 577   for (e = node->callees; e; e = e->next_callee)
 578     {
 579       if (e->callee->global.inlined_to)
 580         {
 581           e->callee->global.inlined_to = inlined_to;
 582           update_inlined_to_pointers (e->callee, inlined_to);
 583         }
 584     }
 585 }
 586
 587 \f
 588 /* For functions-as-trees languages, this performs all optimization and
 589    compilation for FNDECL.  */
 590
 591 void
 592 tree_rest_of_compilation (tree fndecl)
 593 {
 594   location_t saved_loc;
 595   struct cgraph_node *saved_node = NULL, *node;
 596
 597   timevar_push (TV_EXPAND);
 598
 599   gcc_assert (!flag_unit_at_a_time || cgraph_global_info_ready);
 600
 601   /* Initialize the RTL code for the function.  */
 602   current_function_decl = fndecl;
 603   saved_loc = input_location;
 604   input_location = DECL_SOURCE_LOCATION (fndecl);
 605   init_function_start (fndecl);
 606
 607   /* Even though we're inside a function body, we still don't want to
 608      call expand_expr to calculate the size of a variable-sized array.
 609      We haven't necessarily assigned RTL to all variables yet, so it's
 610      not safe to try to expand expressions involving them.  */
 611   cfun->x_dont_save_pending_sizes_p = 1;
 612
 613   node = cgraph_node (fndecl);
 614
 615   /* We might need the body of this function so that we can expand
 616      it inline somewhere else.  This means not lowering some constructs
 617      such as exception handling.  */
 618   if (cgraph_preserve_function_body_p (fndecl))
 619     {
 620       if (!flag_unit_at_a_time)
 621         {
 622           struct cgraph_edge *e;
 623
 624           saved_node = cgraph_clone_node (node);
 625           for (e = saved_node->callees; e; e = e->next_callee)
 626             if (!e->inline_failed)
 627               cgraph_clone_inlined_nodes (e, true);
 628         }
 629       cfun->saved_static_chain_decl = cfun->static_chain_decl;
 630       cfun->saved_tree = save_body (fndecl, &cfun->saved_args,
 631                                     &cfun->saved_static_chain_decl);
 632     }
 633
 634   if (flag_inline_trees)
 635     {
 636       struct cgraph_edge *e;
 637       for (e = node->callees; e; e = e->next_callee)
 638         if (!e->inline_failed || warn_inline)
 639           break;
 640       if (e)
 641         {
 642           timevar_push (TV_INTEGRATION);
 643           optimize_inline_calls (fndecl);
 644           timevar_pop (TV_INTEGRATION);
 645         }
 646     }
 647
 648   /* We are not going to maintain the cgraph edges up to date.
 649      Kill it so it won't confuse us.  */
 650   while (node->callees)
 651     cgraph_remove_edge (node->callees);
 652
 653
 654   /* Initialize the default bitmap obstack.  */
 655   bitmap_obstack_initialize (NULL);
 656   bitmap_obstack_initialize (&reg_obstack); /* FIXME, only at RTL generation*/
 657
 658   vars_to_rename = BITMAP_XMALLOC ();
 659
 660   /* Perform all tree transforms and optimizations.  */
 661   execute_pass_list (all_passes);
 662
 663   bitmap_obstack_release (&reg_obstack);
 664
 665   /* Release the default bitmap obstack.  */
 666   bitmap_obstack_release (NULL);
 667
 668   /* Restore original body if still needed.  */
 669   if (cfun->saved_tree)
 670     {
 671       DECL_SAVED_TREE (fndecl) = cfun->saved_tree;
 672       DECL_ARGUMENTS (fndecl) = cfun->saved_args;
 673       cfun->static_chain_decl = cfun->saved_static_chain_decl;
 674
 675       /* When not in unit-at-a-time mode, we must preserve out of line copy
 676          representing node before inlining.  Restore original outgoing edges
 677          using clone we created earlier.  */
 678       if (!flag_unit_at_a_time)
 679         {
 680           struct cgraph_edge *e;
 681
 682           while (node->callees)
 683             cgraph_remove_edge (node->callees);
 684           node->callees = saved_node->callees;
 685           saved_node->callees = NULL;
 686           update_inlined_to_pointers (node, node);
 687           for (e = node->callees; e; e = e->next_callee)
 688             e->caller = node;
 689           cgraph_remove_node (saved_node);
 690         }
 691     }
 692   else
 693     DECL_SAVED_TREE (fndecl) = NULL;
 694   cfun = 0;
 695
 696   /* If requested, warn about function definitions where the function will
 697      return a value (usually of some struct or union type) which itself will
 698      take up a lot of stack space.  */
 699   if (warn_larger_than && !DECL_EXTERNAL (fndecl) && TREE_TYPE (fndecl))
 700     {
 701       tree ret_type = TREE_TYPE (TREE_TYPE (fndecl));
 702
 703       if (ret_type && TYPE_SIZE_UNIT (ret_type)
 704           && TREE_CODE (TYPE_SIZE_UNIT (ret_type)) == INTEGER_CST
 705           && 0 < compare_tree_int (TYPE_SIZE_UNIT (ret_type),
 706                                    larger_than_size))
 707         {
 708           unsigned int size_as_int
 709             = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (ret_type));
 710
 711           if (compare_tree_int (TYPE_SIZE_UNIT (ret_type), size_as_int) == 0)
 712             warning ("%Jsize of return value of %qD is %u bytes",
 713                      fndecl, fndecl, size_as_int);
 714           else
 715             warning ("%Jsize of return value of %qD is larger than %wd bytes",
 716                      fndecl, fndecl, larger_than_size);
 717         }
 718     }
 719
 720   if (!flag_inline_trees)
 721     {
 722       DECL_SAVED_TREE (fndecl) = NULL;
 723       if (DECL_STRUCT_FUNCTION (fndecl) == 0
 724           && !cgraph_node (fndecl)->origin)
 725         {
 726           /* Stop pointing to the local nodes about to be freed.
 727              But DECL_INITIAL must remain nonzero so we know this
 728              was an actual function definition.
 729              For a nested function, this is done in c_pop_function_context.
 730              If rest_of_compilation set this to 0, leave it 0.  */
 731           if (DECL_INITIAL (fndecl) != 0)
 732             DECL_INITIAL (fndecl) = error_mark_node;
 733         }
 734     }
 735
 736   input_location = saved_loc;
 737
 738   ggc_collect ();
 739   timevar_pop (TV_EXPAND);
 740 }