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 /* Pass: replace the outermost BIND_EXPR.  We removed all of them while
  88    optimizing, but the tree->rtl expander requires it.  */
  89
  90 static void
  91 execute_rebuild_bind (void)
  92 {
  93   DECL_SAVED_TREE (current_function_decl)
  94     = build (BIND_EXPR, void_type_node, NULL_TREE,
  95              DECL_SAVED_TREE (current_function_decl), NULL_TREE);
  96 }
  97
  98 static struct tree_opt_pass pass_rebuild_bind =
  99 {
 100   NULL,                                 /* name */
 101   NULL,                                 /* gate */
 102   execute_rebuild_bind,                 /* execute */
 103   NULL,                                 /* sub */
 104   NULL,                                 /* next */
 105   0,                                    /* static_pass_number */
 106   0,                                    /* tv_id */
 107   0,                                    /* properties_required */
 108   0,                                    /* properties_provided */
 109   0,                                    /* properties_destroyed */
 110   0,                                    /* todo_flags_start */
 111   0                                     /* todo_flags_finish */
 112 };
 113
 114 /* Gate: execute, or not, all of the non-trivial optimizations.  */
 115
 116 static bool
 117 gate_all_optimizations (void)
 118 {
 119   return (optimize >= 1
 120           /* Don't bother doing anything if the program has errors.  */
 121           && !(errorcount || sorrycount));
 122 }
 123
 124 static struct tree_opt_pass pass_all_optimizations =
 125 {
 126   NULL,                                 /* name */
 127   gate_all_optimizations,               /* gate */
 128   NULL,                                 /* execute */
 129   NULL,                                 /* sub */
 130   NULL,                                 /* next */
 131   0,                                    /* static_pass_number */
 132   0,                                    /* tv_id */
 133   0,                                    /* properties_required */
 134   0,                                    /* properties_provided */
 135   0,                                    /* properties_destroyed */
 136   0,                                    /* todo_flags_start */
 137   0                                     /* todo_flags_finish */
 138 };
 139
 140 /* Pass: do the actions required to finish with tree-ssa optimization
 141    passes.  */
 142
 143 static void
 144 execute_del_cfg (void)
 145 {
 146   basic_block bb;
 147   tree *chain;
 148
 149   /* ??? This isn't the right place for this.  Worse, it got computed
 150      more or less at random in various passes.  */
 151   free_dominance_info (CDI_DOMINATORS);
 152
 153   /* Emit gotos for implicit jumps.  */
 154   disband_implicit_edges ();
 155
 156   /* Remove the ssa structures.  Do it here since this includes statement
 157      annotations that need to be intact during disband_implicit_edges.  */
 158   delete_tree_ssa ();
 159
 160   /* Re-chain the statements from the blocks.  */
 161   chain = &DECL_SAVED_TREE (current_function_decl);
 162   *chain = alloc_stmt_list ();
 163   FOR_EACH_BB (bb)
 164     {
 165       append_to_statement_list_force (bb->stmt_list, chain);
 166     }
 167
 168   /* And get rid of the cfg.  */
 169   delete_tree_cfg ();
 170 }
 171
 172 static struct tree_opt_pass pass_del_cfg =
 173 {
 174   NULL,                                 /* name */
 175   NULL,                                 /* gate */
 176   execute_del_cfg,                      /* execute */
 177   NULL,                                 /* sub */
 178   NULL,                                 /* next */
 179   0,                                    /* static_pass_number */
 180   0,                                    /* tv_id */
 181   PROP_cfg,                             /* properties_required */
 182   0,                                    /* properties_provided */
 183   PROP_cfg,                             /* properties_destroyed */
 184   0,                                    /* todo_flags_start */
 185   0                                     /* todo_flags_finish */
 186 };
 187
 188 /* Iterate over the pass tree allocating dump file numbers.  We want
 189    to do this depth first, and independent of whether the pass is
 190    enabled or not.  */
 191
 192 static void
 193 register_one_dump_file (struct tree_opt_pass *pass)
 194 {
 195   char *dot_name, *flag_name;
 196   char num[10];
 197
 198   if (!pass->name)
 199     return;
 200
 201   /* See below in dup_pass_1.  */
 202   num[0] = '\0';
 203   if (pass->static_pass_number)
 204     sprintf (num, "%d", ((int) pass->static_pass_number < 0
 205                          ? 1 : pass->static_pass_number));
 206
 207   dot_name = concat (".", pass->name, num, NULL);
 208   flag_name = concat ("tree-", pass->name, num, NULL);
 209
 210   pass->static_pass_number = dump_register (dot_name, flag_name);
 211 }
 212
 213 static int
 214 register_dump_files (struct tree_opt_pass *pass, int properties)
 215 {
 216   do
 217     {
 218       /* Verify that all required properties are present.  */
 219       if (pass->properties_required & ~properties)
 220         abort ();
 221
 222       if (pass->properties_destroyed & pass->properties_provided)
 223         abort ();
 224
 225       pass->properties_required = properties;
 226       pass->properties_provided = properties =
 227         (properties | pass->properties_provided) & ~pass->properties_destroyed;
 228
 229       if (properties & PROP_trees)
 230         register_one_dump_file (pass);
 231       if (pass->sub)
 232         properties = register_dump_files (pass->sub, properties);
 233       pass = pass->next;
 234     }
 235   while (pass);
 236
 237   return properties;
 238 }
 239
 240 /* Duplicate a pass that's to be run more than once.  */
 241
 242 static struct tree_opt_pass *
 243 dup_pass_1 (struct tree_opt_pass *pass)
 244 {
 245   struct tree_opt_pass *new;
 246
 247   new = xmalloc (sizeof (*new));
 248   memcpy (new, pass, sizeof (*new));
 249
 250   /* Indicate to register_dump_files that this pass has duplicates,
 251      and so it should rename the dump file.  The first instance will
 252      be < 0, and be number of duplicates = -static_pass_number + 1.
 253      Subsequent instances will be > 0 and just the duplicate number.  */
 254   if (pass->name)
 255     {
 256       int n, p = pass->static_pass_number;
 257
 258       if (p)
 259         n = -(--p) + 1;
 260       else
 261         n = 2, p = -1;
 262
 263       pass->static_pass_number = p;
 264       new->static_pass_number = n;
 265     }
 266
 267   return new;
 268 }
 269
 270 /* Construct the pass tree.  */
 271
 272 void
 273 init_tree_optimization_passes (void)
 274 {
 275   struct tree_opt_pass **p;
 276
 277 #define NEXT_PASS(PASS) (*p = &PASS, p = &(*p)->next)
 278 #define DUP_PASS(PASS)  (*dup_pass_1 (&PASS))
 279
 280   p = &all_passes;
 281   NEXT_PASS (pass_gimple);
 282   NEXT_PASS (pass_remove_useless_stmts);
 283   NEXT_PASS (pass_mudflap_1);
 284   NEXT_PASS (pass_lower_cf);
 285   NEXT_PASS (pass_lower_eh);
 286   NEXT_PASS (pass_all_optimizations);
 287   NEXT_PASS (pass_mudflap_2);
 288   NEXT_PASS (pass_rebuild_bind);
 289   NEXT_PASS (pass_expand);
 290   NEXT_PASS (pass_rest_of_compilation);
 291   *p = NULL;
 292
 293   p = &pass_all_optimizations.sub;
 294   NEXT_PASS (pass_build_cfg);
 295   NEXT_PASS (pass_tree_profile);
 296   NEXT_PASS (pass_referenced_vars);
 297   NEXT_PASS (pass_build_pta);
 298   NEXT_PASS (pass_build_ssa);
 299   NEXT_PASS (pass_rename_ssa_copies);
 300   NEXT_PASS (pass_early_warn_uninitialized);
 301   NEXT_PASS (pass_dce);
 302   NEXT_PASS (pass_dominator);
 303   NEXT_PASS (pass_redundant_phi);
 304   NEXT_PASS (DUP_PASS (pass_dce));
 305   NEXT_PASS (pass_forwprop);
 306   NEXT_PASS (pass_phiopt);
 307   NEXT_PASS (pass_may_alias);
 308   NEXT_PASS (pass_tail_recursion);
 309   NEXT_PASS (pass_ch);
 310   NEXT_PASS (pass_del_pta);
 311   NEXT_PASS (pass_profile);
 312   NEXT_PASS (pass_lower_complex);
 313   NEXT_PASS (pass_sra);
 314   NEXT_PASS (DUP_PASS (pass_rename_ssa_copies));
 315   NEXT_PASS (DUP_PASS (pass_dominator));
 316   NEXT_PASS (DUP_PASS (pass_redundant_phi));
 317   NEXT_PASS (DUP_PASS (pass_dce));
 318   NEXT_PASS (pass_dse);
 319   NEXT_PASS (DUP_PASS (pass_forwprop));
 320   NEXT_PASS (DUP_PASS (pass_phiopt));
 321   NEXT_PASS (pass_ccp);
 322   NEXT_PASS (DUP_PASS (pass_redundant_phi));
 323   NEXT_PASS (pass_fold_builtins);
 324   NEXT_PASS (pass_split_crit_edges);
 325   NEXT_PASS (pass_pre);
 326   NEXT_PASS (DUP_PASS (pass_dominator));
 327   NEXT_PASS (DUP_PASS (pass_redundant_phi));
 328   NEXT_PASS (pass_cd_dce);
 329   NEXT_PASS (DUP_PASS (pass_dse));
 330   NEXT_PASS (DUP_PASS (pass_forwprop));
 331   NEXT_PASS (DUP_PASS (pass_phiopt));
 332   NEXT_PASS (pass_tail_calls);
 333   NEXT_PASS (pass_late_warn_uninitialized);
 334   NEXT_PASS (pass_warn_function_return);
 335   NEXT_PASS (pass_del_ssa);
 336   NEXT_PASS (pass_nrv);
 337   NEXT_PASS (pass_remove_useless_vars);
 338   NEXT_PASS (pass_del_cfg);
 339   *p = NULL;
 340
 341 #undef NEXT_PASS
 342 #undef DUP_PASS
 343
 344   /* Register the passes with the tree dump code.  */
 345   register_dump_files (all_passes, 0);
 346 }
 347
 348 static void execute_pass_list (struct tree_opt_pass *);
 349
 350 static unsigned int last_verified;
 351
 352 static void
 353 execute_todo (unsigned int flags)
 354 {
 355   if (flags & TODO_rename_vars)
 356     {
 357       if (bitmap_first_set_bit (vars_to_rename) >= 0)
 358         rewrite_into_ssa ();
 359       BITMAP_XFREE (vars_to_rename);
 360     }
 361
 362   if ((flags & TODO_dump_func) && dump_file)
 363     dump_function_to_file (current_function_decl,
 364                            dump_file, dump_flags);
 365
 366   if (flags & TODO_ggc_collect)
 367     ggc_collect ();
 368
 369 #ifdef ENABLE_CHECKING
 370   if (flags & TODO_verify_ssa)
 371     verify_ssa ();
 372   if (flags & TODO_verify_flow)
 373     verify_flow_info ();
 374   if (flags & TODO_verify_stmts)
 375     verify_stmts ();
 376 #endif
 377 }
 378
 379 static bool
 380 execute_one_pass (struct tree_opt_pass *pass)
 381 {
 382   unsigned int todo;
 383
 384   /* See if we're supposed to run this pass.  */
 385   if (pass->gate && !pass->gate ())
 386     return false;
 387
 388   /* Note that the folders should only create gimple expressions.
 389      This is a hack until the new folder is ready.  */
 390   in_gimple_form = (pass->properties_provided & PROP_trees) != 0;
 391
 392   /* Run pre-pass verification.  */
 393   todo = pass->todo_flags_start & ~last_verified;
 394   if (todo)
 395     execute_todo (todo);
 396
 397   /* If a dump file name is present, open it if enabled.  */
 398   if (pass->static_pass_number)
 399     {
 400       dump_file = dump_begin (pass->static_pass_number, &dump_flags);
 401       if (dump_file)
 402         {
 403           const char *dname, *aname;
 404           dname = lang_hooks.decl_printable_name (current_function_decl, 2);
 405           aname = (IDENTIFIER_POINTER
 406                    (DECL_ASSEMBLER_NAME (current_function_decl)));
 407           fprintf (dump_file, "\n;; Function %s (%s)\n\n", dname, aname);
 408         }
 409     }
 410
 411   /* If a timevar is present, start it.  */
 412   if (pass->tv_id)
 413     timevar_push (pass->tv_id);
 414
 415   /* If the pass is requesting ssa variable renaming, allocate the bitmap.  */
 416   if (pass->todo_flags_finish & TODO_rename_vars)
 417     vars_to_rename = BITMAP_XMALLOC ();
 418
 419   /* Do it!  */
 420   if (pass->execute)
 421     pass->execute ();
 422
 423   /* Run post-pass cleanup and verification.  */
 424   todo = pass->todo_flags_finish;
 425   last_verified = todo & TODO_verify_all;
 426   if (todo)
 427     execute_todo (todo);
 428
 429   /* Close down timevar and dump file.  */
 430   if (pass->tv_id)
 431     timevar_pop (pass->tv_id);
 432   if (dump_file)
 433     {
 434       dump_end (pass->static_pass_number, dump_file);
 435       dump_file = NULL;
 436     }
 437
 438   return true;
 439 }
 440
 441 static void
 442 execute_pass_list (struct tree_opt_pass *pass)
 443 {
 444   do
 445     {
 446       if (execute_one_pass (pass) && pass->sub)
 447         execute_pass_list (pass->sub);
 448       pass = pass->next;
 449     }
 450   while (pass);
 451 }
 452
 453 \f
 454 /* For functions-as-trees languages, this performs all optimization and
 455    compilation for FNDECL.  */
 456
 457 void
 458 tree_rest_of_compilation (tree fndecl, bool nested_p)
 459 {
 460   location_t saved_loc;
 461   struct cgraph_node *saved_node = NULL, *node;
 462
 463   timevar_push (TV_EXPAND);
 464
 465   if (flag_unit_at_a_time && !cgraph_global_info_ready)
 466     abort ();
 467
 468   /* Initialize the RTL code for the function.  */
 469   current_function_decl = fndecl;
 470   saved_loc = input_location;
 471   input_location = DECL_SOURCE_LOCATION (fndecl);
 472   init_function_start (fndecl);
 473
 474   /* This function is being processed in whole-function mode.  */
 475   cfun->x_whole_function_mode_p = 1;
 476
 477   /* Even though we're inside a function body, we still don't want to
 478      call expand_expr to calculate the size of a variable-sized array.
 479      We haven't necessarily assigned RTL to all variables yet, so it's
 480      not safe to try to expand expressions involving them.  */
 481   immediate_size_expand = 0;
 482   cfun->x_dont_save_pending_sizes_p = 1;
 483
 484   node = cgraph_node (fndecl);
 485
 486   /* We might need the body of this function so that we can expand
 487      it inline somewhere else.  This means not lowering some constructs
 488      such as exception handling.  */
 489   if (cgraph_preserve_function_body_p (fndecl))
 490     {
 491       if (!flag_unit_at_a_time)
 492         {
 493           struct cgraph_edge *e;
 494
 495           saved_node = cgraph_clone_node (node);
 496           for (e = saved_node->callees; e; e = e->next_callee)
 497             if (!e->inline_failed)
 498               cgraph_clone_inlined_nodes (e, true);
 499         }
 500       cfun->saved_tree = save_body (fndecl, &cfun->saved_args);
 501     }
 502
 503   if (flag_inline_trees)
 504     {
 505       struct cgraph_edge *e;
 506       for (e = node->callees; e; e = e->next_callee)
 507         if (!e->inline_failed || warn_inline)
 508           break;
 509       if (e)
 510         {
 511           timevar_push (TV_INTEGRATION);
 512           optimize_inline_calls (fndecl);
 513           timevar_pop (TV_INTEGRATION);
 514         }
 515     }
 516
 517   /* If this is a nested function, protect the local variables in the stack
 518      above us from being collected while we're compiling this function.  */
 519   if (nested_p)
 520     ggc_push_context ();
 521
 522   /* Perform all tree transforms and optimizations.  */
 523   execute_pass_list (all_passes);
 524
 525   /* Restore original body if still needed.  */
 526   if (cfun->saved_tree)
 527     {
 528       DECL_SAVED_TREE (fndecl) = cfun->saved_tree;
 529       DECL_ARGUMENTS (fndecl) = cfun->saved_args;
 530
 531       /* When not in unit-at-a-time mode, we must preserve out of line copy
 532          representing node before inlining.  Restore original outgoing edges
 533          using clone we created earlier.  */
 534       if (!flag_unit_at_a_time)
 535         {
 536           struct cgraph_edge *e;
 537           while (node->callees)
 538             cgraph_remove_edge (node->callees);
 539           node->callees = saved_node->callees;
 540           saved_node->callees = NULL;
 541           for (e = saved_node->callees; e; e = e->next_callee)
 542             e->caller = node;
 543           cgraph_remove_node (saved_node);
 544         }
 545     }
 546   else
 547     DECL_SAVED_TREE (fndecl) = NULL;
 548   cfun = 0;
 549
 550   /* If requested, warn about function definitions where the function will
 551      return a value (usually of some struct or union type) which itself will
 552      take up a lot of stack space.  */
 553   if (warn_larger_than && !DECL_EXTERNAL (fndecl) && TREE_TYPE (fndecl))
 554     {
 555       tree ret_type = TREE_TYPE (TREE_TYPE (fndecl));
 556
 557       if (ret_type && TYPE_SIZE_UNIT (ret_type)
 558           && TREE_CODE (TYPE_SIZE_UNIT (ret_type)) == INTEGER_CST
 559           && 0 < compare_tree_int (TYPE_SIZE_UNIT (ret_type),
 560                                    larger_than_size))
 561         {
 562           unsigned int size_as_int
 563             = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (ret_type));
 564
 565           if (compare_tree_int (TYPE_SIZE_UNIT (ret_type), size_as_int) == 0)
 566             warning ("%Jsize of return value of '%D' is %u bytes",
 567                      fndecl, fndecl, size_as_int);
 568           else
 569             warning ("%Jsize of return value of '%D' is larger than %wd bytes",
 570                      fndecl, fndecl, larger_than_size);
 571         }
 572     }
 573
 574   if (!nested_p && !flag_inline_trees)
 575     {
 576       DECL_SAVED_TREE (fndecl) = NULL;
 577       if (DECL_STRUCT_FUNCTION (fndecl) == 0
 578           && !cgraph_node (fndecl)->origin)
 579         {
 580           /* Stop pointing to the local nodes about to be freed.
 581              But DECL_INITIAL must remain nonzero so we know this
 582              was an actual function definition.
 583              For a nested function, this is done in c_pop_function_context.
 584              If rest_of_compilation set this to 0, leave it 0.  */
 585           if (DECL_INITIAL (fndecl) != 0)
 586             DECL_INITIAL (fndecl) = error_mark_node;
 587         }
 588     }
 589
 590   input_location = saved_loc;
 591
 592   ggc_collect ();
 593
 594   /* Undo the GC context switch.  */
 595   if (nested_p)
 596     ggc_pop_context ();
 597   timevar_pop (TV_EXPAND);
 598 }