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 "tree-alias-common.h"
  48 #include "ggc.h"
  49 #include "cgraph.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: gimplify the function if it's not been done.  */
  61
  62 static void
  63 execute_gimple (void)
  64 {
  65   /* We have this test here rather than as the gate because we always
  66      want to dump the original gimplified function.  */
  67   if (!lang_hooks.gimple_before_inlining)
  68     gimplify_function_tree (current_function_decl);
  69 }
  70
  71 static struct tree_opt_pass pass_gimple =
  72 {
  73   "gimple",                             /* name */
  74   NULL,                                 /* gate */
  75   execute_gimple,                       /* execute */
  76   NULL,                                 /* sub */
  77   NULL,                                 /* next */
  78   0,                                    /* static_pass_number */
  79   0,                                    /* tv_id */
  80   0,                                    /* properties_required */
  81   PROP_gimple_any,                      /* properties_provided */
  82   0,                                    /* properties_destroyed */
  83   0,                                    /* todo_flags_start */
  84   TODO_dump_func                        /* todo_flags_finish */
  85 };
  86
  87 /* Gate: execute, or not, all of the non-trivial optimizations.  */
  88
  89 static bool
  90 gate_all_optimizations (void)
  91 {
  92   return (optimize >= 1
  93           /* Don't bother doing anything if the program has errors.  */
  94           && !(errorcount || sorrycount));
  95 }
  96
  97 static struct tree_opt_pass pass_all_optimizations =
  98 {
  99   NULL,                                 /* name */
 100   gate_all_optimizations,               /* gate */
 101   NULL,                                 /* execute */
 102   NULL,                                 /* sub */
 103   NULL,                                 /* next */
 104   0,                                    /* static_pass_number */
 105   0,                                    /* tv_id */
 106   0,                                    /* properties_required */
 107   0,                                    /* properties_provided */
 108   0,                                    /* properties_destroyed */
 109   0,                                    /* todo_flags_start */
 110   0                                     /* todo_flags_finish */
 111 };
 112
 113 /* Pass: do the actions required to finish with tree-ssa optimization
 114    passes.  */
 115
 116 static void
 117 execute_free_datastructures (void)
 118 {
 119   tree *chain;
 120
 121   /* ??? This isn't the right place for this.  Worse, it got computed
 122      more or less at random in various passes.  */
 123   free_dominance_info (CDI_DOMINATORS);
 124
 125   /* Emit gotos for implicit jumps.  */
 126   disband_implicit_edges ();
 127
 128   /* Remove the ssa structures.  Do it here since this includes statement
 129      annotations that need to be intact during disband_implicit_edges.  */
 130   delete_tree_ssa ();
 131
 132   /* Re-chain the statements from the blocks.  */
 133   chain = &DECL_SAVED_TREE (current_function_decl);
 134   *chain = alloc_stmt_list ();
 135
 136   /* And get rid of annotations we no longer need.  */
 137   delete_tree_cfg_annotations ();
 138 }
 139
 140 static struct tree_opt_pass pass_free_datastructures =
 141 {
 142   NULL,                                 /* name */
 143   NULL,                                 /* gate */
 144   execute_free_datastructures,                  /* execute */
 145   NULL,                                 /* sub */
 146   NULL,                                 /* next */
 147   0,                                    /* static_pass_number */
 148   0,                                    /* tv_id */
 149   PROP_cfg,                             /* properties_required */
 150   0,                                    /* properties_provided */
 151   0,                                    /* properties_destroyed */
 152   0,                                    /* todo_flags_start */
 153   0                                     /* todo_flags_finish */
 154 };
 155
 156
 157 /* Do the actions required to initialize internal data structures used
 158    in tree-ssa optimization passes.  */
 159
 160 static void
 161 execute_init_datastructures (void)
 162 {
 163   /* Allocate hash tables, arrays and other structures.  */
 164   init_tree_ssa ();
 165 }
 166
 167 static struct tree_opt_pass pass_init_datastructures =
 168 {
 169   NULL,                                 /* name */
 170   NULL,                                 /* gate */
 171   execute_init_datastructures,          /* execute */
 172   NULL,                                 /* sub */
 173   NULL,                                 /* next */
 174   0,                                    /* static_pass_number */
 175   0,                                    /* tv_id */
 176   PROP_cfg,                             /* properties_required */
 177   0,                                    /* properties_provided */
 178   0,                                    /* properties_destroyed */
 179   0,                                    /* todo_flags_start */
 180   0                                     /* todo_flags_finish */
 181 };
 182
 183 /* Iterate over the pass tree allocating dump file numbers.  We want
 184    to do this depth first, and independent of whether the pass is
 185    enabled or not.  */
 186
 187 static void
 188 register_one_dump_file (struct tree_opt_pass *pass)
 189 {
 190   char *dot_name, *flag_name;
 191   char num[10];
 192
 193   if (!pass->name)
 194     return;
 195
 196   /* See below in dup_pass_1.  */
 197   num[0] = '\0';
 198   if (pass->static_pass_number)
 199     sprintf (num, "%d", ((int) pass->static_pass_number < 0
 200                          ? 1 : pass->static_pass_number));
 201
 202   dot_name = concat (".", pass->name, num, NULL);
 203   flag_name = concat ("tree-", pass->name, num, NULL);
 204
 205   pass->static_pass_number = dump_register (dot_name, flag_name);
 206 }
 207
 208 static int
 209 register_dump_files (struct tree_opt_pass *pass, int properties)
 210 {
 211   do
 212     {
 213       /* Verify that all required properties are present.  */
 214       if (pass->properties_required & ~properties)
 215         abort ();
 216
 217       if (pass->properties_destroyed & pass->properties_provided)
 218         abort ();
 219
 220       pass->properties_required = properties;
 221       pass->properties_provided = properties =
 222         (properties | pass->properties_provided) & ~pass->properties_destroyed;
 223
 224       if (properties & PROP_trees)
 225         register_one_dump_file (pass);
 226       if (pass->sub)
 227         properties = register_dump_files (pass->sub, properties);
 228       pass = pass->next;
 229     }
 230   while (pass);
 231
 232   return properties;
 233 }
 234
 235 /* Duplicate a pass that's to be run more than once.  */
 236
 237 static struct tree_opt_pass *
 238 dup_pass_1 (struct tree_opt_pass *pass)
 239 {
 240   struct tree_opt_pass *new;
 241
 242   new = xmalloc (sizeof (*new));
 243   memcpy (new, pass, sizeof (*new));
 244
 245   /* Indicate to register_dump_files that this pass has duplicates,
 246      and so it should rename the dump file.  The first instance will
 247      be < 0, and be number of duplicates = -static_pass_number + 1.
 248      Subsequent instances will be > 0 and just the duplicate number.  */
 249   if (pass->name)
 250     {
 251       int n, p = pass->static_pass_number;
 252
 253       if (p)
 254         n = -(--p) + 1;
 255       else
 256         n = 2, p = -1;
 257
 258       pass->static_pass_number = p;
 259       new->static_pass_number = n;
 260     }
 261
 262   return new;
 263 }
 264
 265 /* Construct the pass tree.  */
 266
 267 void
 268 init_tree_optimization_passes (void)
 269 {
 270   struct tree_opt_pass **p;
 271
 272 #define NEXT_PASS(PASS) (*p = &PASS, p = &(*p)->next)
 273 #define DUP_PASS(PASS)  (*dup_pass_1 (&PASS))
 274
 275   p = &all_passes;
 276   NEXT_PASS (pass_gimple);
 277   NEXT_PASS (pass_remove_useless_stmts);
 278   NEXT_PASS (pass_mudflap_1);
 279   NEXT_PASS (pass_lower_cf);
 280   NEXT_PASS (pass_lower_eh);
 281   NEXT_PASS (pass_build_cfg);
 282   NEXT_PASS (pass_tree_profile);
 283   NEXT_PASS (pass_init_datastructures);
 284   NEXT_PASS (pass_all_optimizations);
 285   NEXT_PASS (pass_mudflap_2);
 286   NEXT_PASS (pass_free_datastructures);
 287   NEXT_PASS (pass_expand);
 288   NEXT_PASS (pass_rest_of_compilation);
 289   *p = NULL;
 290
 291   p = &pass_all_optimizations.sub;
 292   NEXT_PASS (pass_referenced_vars);
 293   NEXT_PASS (pass_build_pta);
 294   NEXT_PASS (pass_build_ssa);
 295   NEXT_PASS (pass_rename_ssa_copies);
 296   NEXT_PASS (pass_early_warn_uninitialized);
 297   NEXT_PASS (pass_dce);
 298   NEXT_PASS (pass_dominator);
 299   NEXT_PASS (pass_redundant_phi);
 300   NEXT_PASS (DUP_PASS (pass_dce));
 301   NEXT_PASS (pass_forwprop);
 302   NEXT_PASS (pass_phiopt);
 303   NEXT_PASS (pass_may_alias);
 304   NEXT_PASS (pass_tail_recursion);
 305   NEXT_PASS (pass_ch);
 306   NEXT_PASS (pass_del_pta);
 307   NEXT_PASS (pass_profile);
 308   NEXT_PASS (pass_lower_complex);
 309   NEXT_PASS (pass_sra);
 310   NEXT_PASS (DUP_PASS (pass_rename_ssa_copies));
 311   NEXT_PASS (DUP_PASS (pass_dominator));
 312   NEXT_PASS (DUP_PASS (pass_redundant_phi));
 313   NEXT_PASS (DUP_PASS (pass_dce));
 314   NEXT_PASS (pass_dse);
 315   NEXT_PASS (DUP_PASS (pass_forwprop));
 316   NEXT_PASS (DUP_PASS (pass_phiopt));
 317   NEXT_PASS (pass_ccp);
 318   NEXT_PASS (DUP_PASS (pass_redundant_phi));
 319   NEXT_PASS (pass_fold_builtins);
 320   NEXT_PASS (pass_split_crit_edges);
 321   NEXT_PASS (pass_pre);
 322   NEXT_PASS (DUP_PASS (pass_dominator));
 323   NEXT_PASS (DUP_PASS (pass_redundant_phi));
 324   NEXT_PASS (pass_cd_dce);
 325   NEXT_PASS (DUP_PASS (pass_dse));
 326   NEXT_PASS (DUP_PASS (pass_forwprop));
 327   NEXT_PASS (DUP_PASS (pass_phiopt));
 328   NEXT_PASS (pass_tail_calls);
 329   NEXT_PASS (pass_late_warn_uninitialized);
 330   NEXT_PASS (pass_warn_function_return);
 331   NEXT_PASS (pass_del_ssa);
 332   NEXT_PASS (pass_nrv);
 333   NEXT_PASS (pass_remove_useless_vars);
 334   *p = NULL;
 335
 336 #undef NEXT_PASS
 337 #undef DUP_PASS
 338
 339   /* Register the passes with the tree dump code.  */
 340   register_dump_files (all_passes, 0);
 341 }
 342
 343 static void execute_pass_list (struct tree_opt_pass *);
 344
 345 static unsigned int last_verified;
 346
 347 static void
 348 execute_todo (unsigned int flags)
 349 {
 350   if (flags & TODO_rename_vars)
 351     {
 352       if (bitmap_first_set_bit (vars_to_rename) >= 0)
 353         rewrite_into_ssa ();
 354       BITMAP_XFREE (vars_to_rename);
 355     }
 356
 357   if ((flags & TODO_dump_func) && dump_file)
 358     dump_function_to_file (current_function_decl,
 359                            dump_file, dump_flags);
 360
 361   if (flags & TODO_ggc_collect)
 362     ggc_collect ();
 363
 364 #ifdef ENABLE_CHECKING
 365   if (flags & TODO_verify_ssa)
 366     verify_ssa ();
 367   if (flags & TODO_verify_flow)
 368     verify_flow_info ();
 369   if (flags & TODO_verify_stmts)
 370     verify_stmts ();
 371 #endif
 372 }
 373
 374 static bool
 375 execute_one_pass (struct tree_opt_pass *pass)
 376 {
 377   unsigned int todo;
 378
 379   /* See if we're supposed to run this pass.  */
 380   if (pass->gate && !pass->gate ())
 381     return false;
 382
 383   /* Note that the folders should only create gimple expressions.
 384      This is a hack until the new folder is ready.  */
 385   in_gimple_form = (pass->properties_provided & PROP_trees) != 0;
 386
 387   /* Run pre-pass verification.  */
 388   todo = pass->todo_flags_start & ~last_verified;
 389   if (todo)
 390     execute_todo (todo);
 391
 392   /* If a dump file name is present, open it if enabled.  */
 393   if (pass->static_pass_number)
 394     {
 395       dump_file = dump_begin (pass->static_pass_number, &dump_flags);
 396       if (dump_file)
 397         {
 398           const char *dname, *aname;
 399           dname = lang_hooks.decl_printable_name (current_function_decl, 2);
 400           aname = (IDENTIFIER_POINTER
 401                    (DECL_ASSEMBLER_NAME (current_function_decl)));
 402           fprintf (dump_file, "\n;; Function %s (%s)\n\n", dname, aname);
 403         }
 404     }
 405
 406   /* If a timevar is present, start it.  */
 407   if (pass->tv_id)
 408     timevar_push (pass->tv_id);
 409
 410   /* If the pass is requesting ssa variable renaming, allocate the bitmap.  */
 411   if (pass->todo_flags_finish & TODO_rename_vars)
 412     vars_to_rename = BITMAP_XMALLOC ();
 413
 414   /* Do it!  */
 415   if (pass->execute)
 416     pass->execute ();
 417
 418   /* Run post-pass cleanup and verification.  */
 419   todo = pass->todo_flags_finish;
 420   last_verified = todo & TODO_verify_all;
 421   if (todo)
 422     execute_todo (todo);
 423
 424   /* Close down timevar and dump file.  */
 425   if (pass->tv_id)
 426     timevar_pop (pass->tv_id);
 427   if (dump_file)
 428     {
 429       dump_end (pass->static_pass_number, dump_file);
 430       dump_file = NULL;
 431     }
 432
 433   return true;
 434 }
 435
 436 static void
 437 execute_pass_list (struct tree_opt_pass *pass)
 438 {
 439   do
 440     {
 441       if (execute_one_pass (pass) && pass->sub)
 442         execute_pass_list (pass->sub);
 443       pass = pass->next;
 444     }
 445   while (pass);
 446 }
 447
 448 \f
 449 /* For functions-as-trees languages, this performs all optimization and
 450    compilation for FNDECL.  */
 451
 452 void
 453 tree_rest_of_compilation (tree fndecl, bool nested_p)
 454 {
 455   location_t saved_loc;
 456   struct cgraph_node *saved_node = NULL, *node;
 457
 458   timevar_push (TV_EXPAND);
 459
 460   if (flag_unit_at_a_time && !cgraph_global_info_ready)
 461     abort ();
 462
 463   /* Initialize the RTL code for the function.  */
 464   current_function_decl = fndecl;
 465   saved_loc = input_location;
 466   input_location = DECL_SOURCE_LOCATION (fndecl);
 467   init_function_start (fndecl);
 468
 469   /* This function is being processed in whole-function mode.  */
 470   cfun->x_whole_function_mode_p = 1;
 471
 472   /* Even though we're inside a function body, we still don't want to
 473      call expand_expr to calculate the size of a variable-sized array.
 474      We haven't necessarily assigned RTL to all variables yet, so it's
 475      not safe to try to expand expressions involving them.  */
 476   immediate_size_expand = 0;
 477   cfun->x_dont_save_pending_sizes_p = 1;
 478
 479   node = cgraph_node (fndecl);
 480
 481   /* We might need the body of this function so that we can expand
 482      it inline somewhere else.  This means not lowering some constructs
 483      such as exception handling.  */
 484   if (cgraph_preserve_function_body_p (fndecl))
 485     {
 486       if (!flag_unit_at_a_time)
 487         {
 488           struct cgraph_edge *e;
 489
 490           saved_node = cgraph_clone_node (node);
 491           for (e = saved_node->callees; e; e = e->next_callee)
 492             if (!e->inline_failed)
 493               cgraph_clone_inlined_nodes (e, true);
 494         }
 495       cfun->saved_tree = save_body (fndecl, &cfun->saved_args);
 496     }
 497
 498   if (flag_inline_trees)
 499     {
 500       struct cgraph_edge *e;
 501       for (e = node->callees; e; e = e->next_callee)
 502         if (!e->inline_failed || warn_inline)
 503           break;
 504       if (e)
 505         {
 506           timevar_push (TV_INTEGRATION);
 507           optimize_inline_calls (fndecl);
 508           timevar_pop (TV_INTEGRATION);
 509         }
 510     }
 511
 512   /* If this is a nested function, protect the local variables in the stack
 513      above us from being collected while we're compiling this function.  */
 514   if (nested_p)
 515     ggc_push_context ();
 516
 517   /* Perform all tree transforms and optimizations.  */
 518   execute_pass_list (all_passes);
 519
 520   /* Restore original body if still needed.  */
 521   if (cfun->saved_tree)
 522     {
 523       DECL_SAVED_TREE (fndecl) = cfun->saved_tree;
 524       DECL_ARGUMENTS (fndecl) = cfun->saved_args;
 525
 526       /* When not in unit-at-a-time mode, we must preserve out of line copy
 527          representing node before inlining.  Restore original outgoing edges
 528          using clone we created earlier.  */
 529       if (!flag_unit_at_a_time)
 530         {
 531           struct cgraph_edge *e;
 532           while (node->callees)
 533             cgraph_remove_edge (node->callees);
 534           node->callees = saved_node->callees;
 535           saved_node->callees = NULL;
 536           for (e = saved_node->callees; e; e = e->next_callee)
 537             e->caller = node;
 538           cgraph_remove_node (saved_node);
 539         }
 540     }
 541   else
 542     DECL_SAVED_TREE (fndecl) = NULL;
 543   cfun = 0;
 544
 545   /* If requested, warn about function definitions where the function will
 546      return a value (usually of some struct or union type) which itself will
 547      take up a lot of stack space.  */
 548   if (warn_larger_than && !DECL_EXTERNAL (fndecl) && TREE_TYPE (fndecl))
 549     {
 550       tree ret_type = TREE_TYPE (TREE_TYPE (fndecl));
 551
 552       if (ret_type && TYPE_SIZE_UNIT (ret_type)
 553           && TREE_CODE (TYPE_SIZE_UNIT (ret_type)) == INTEGER_CST
 554           && 0 < compare_tree_int (TYPE_SIZE_UNIT (ret_type),
 555                                    larger_than_size))
 556         {
 557           unsigned int size_as_int
 558             = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (ret_type));
 559
 560           if (compare_tree_int (TYPE_SIZE_UNIT (ret_type), size_as_int) == 0)
 561             warning ("%Jsize of return value of '%D' is %u bytes",
 562                      fndecl, fndecl, size_as_int);
 563           else
 564             warning ("%Jsize of return value of '%D' is larger than %wd bytes",
 565                      fndecl, fndecl, larger_than_size);
 566         }
 567     }
 568
 569   if (!nested_p && !flag_inline_trees)
 570     {
 571       DECL_SAVED_TREE (fndecl) = NULL;
 572       if (DECL_STRUCT_FUNCTION (fndecl) == 0
 573           && !cgraph_node (fndecl)->origin)
 574         {
 575           /* Stop pointing to the local nodes about to be freed.
 576              But DECL_INITIAL must remain nonzero so we know this
 577              was an actual function definition.
 578              For a nested function, this is done in c_pop_function_context.
 579              If rest_of_compilation set this to 0, leave it 0.  */
 580           if (DECL_INITIAL (fndecl) != 0)
 581             DECL_INITIAL (fndecl) = error_mark_node;
 582         }
 583     }
 584
 585   input_location = saved_loc;
 586
 587   ggc_collect ();
 588
 589   /* Undo the GC context switch.  */
 590   if (nested_p)
 591     ggc_pop_context ();
 592   timevar_pop (TV_EXPAND);
 593 }