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