gcc/tree-optimize.c

   1 /* Top-level control of tree optimizations.
   2    Copyright 2001, 2002, 2003, 2004, 2005, 2007, 2008
   3    Free Software Foundation, Inc.
   4    Contributed by Diego Novillo <dnovillo@redhat.com>
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation; either version 3, or (at your option)
  11 any later version.
  12
  13 GCC is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License 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 #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 #include "cfgloop.h"
  51 #include "except.h"
  52
  53
  54 /* Gate: execute, or not, all of the non-trivial optimizations.  */
  55
  56 static bool
  57 gate_all_optimizations (void)
  58 {
  59   return (optimize >= 1
  60           /* Don't bother doing anything if the program has errors.
  61              We have to pass down the queue if we already went into SSA */
  62           && (!(errorcount || sorrycount) || gimple_in_ssa_p (cfun)));
  63 }
  64
  65 struct gimple_opt_pass pass_all_optimizations =
  66 {
  67  {
  68   GIMPLE_PASS,
  69   NULL,                                 /* name */
  70   gate_all_optimizations,               /* gate */
  71   NULL,                                 /* execute */
  72   NULL,                                 /* sub */
  73   NULL,                                 /* next */
  74   0,                                    /* static_pass_number */
  75   0,                                    /* tv_id */
  76   0,                                    /* properties_required */
  77   0,                                    /* properties_provided */
  78   0,                                    /* properties_destroyed */
  79   0,                                    /* todo_flags_start */
  80   0                                     /* todo_flags_finish */
  81  }
  82 };
  83
  84 /* Gate: execute, or not, all of the non-trivial optimizations.  */
  85
  86 static bool
  87 gate_all_early_local_passes (void)
  88 {
  89           /* Don't bother doing anything if the program has errors.  */
  90   return (!errorcount && !sorrycount);
  91 }
  92
  93 struct simple_ipa_opt_pass pass_early_local_passes =
  94 {
  95  {
  96   SIMPLE_IPA_PASS,
  97   "early_local_cleanups",               /* name */
  98   gate_all_early_local_passes,          /* gate */
  99   NULL,                                 /* execute */
 100   NULL,                                 /* sub */
 101   NULL,                                 /* next */
 102   0,                                    /* static_pass_number */
 103   0,                                    /* tv_id */
 104   0,                                    /* properties_required */
 105   0,                                    /* properties_provided */
 106   0,                                    /* properties_destroyed */
 107   0,                                    /* todo_flags_start */
 108   TODO_remove_functions                 /* todo_flags_finish */
 109  }
 110 };
 111
 112 static unsigned int
 113 execute_early_local_optimizations (void)
 114 {
 115   /* First time we start with early optimization we need to advance
 116      cgraph state so newly inserted functions are also early optimized.
 117      However we execute early local optimizations for lately inserted
 118      functions, in that case don't reset cgraph state back to IPA_SSA.  */
 119   if (cgraph_state < CGRAPH_STATE_IPA_SSA)
 120     cgraph_state = CGRAPH_STATE_IPA_SSA;
 121   return 0;
 122 }
 123
 124 /* Gate: execute, or not, all of the non-trivial optimizations.  */
 125
 126 static bool
 127 gate_all_early_optimizations (void)
 128 {
 129   return (optimize >= 1
 130           /* Don't bother doing anything if the program has errors.  */
 131           && !(errorcount || sorrycount));
 132 }
 133
 134 struct gimple_opt_pass pass_all_early_optimizations =
 135 {
 136  {
 137   GIMPLE_PASS,
 138   "early_optimizations",                /* name */
 139   gate_all_early_optimizations,         /* gate */
 140   execute_early_local_optimizations,    /* execute */
 141   NULL,                                 /* sub */
 142   NULL,                                 /* next */
 143   0,                                    /* static_pass_number */
 144   0,                                    /* tv_id */
 145   0,                                    /* properties_required */
 146   0,                                    /* properties_provided */
 147   0,                                    /* properties_destroyed */
 148   0,                                    /* todo_flags_start */
 149   0                                     /* todo_flags_finish */
 150  }
 151 };
 152
 153 /* Pass: cleanup the CFG just before expanding trees to RTL.
 154    This is just a round of label cleanups and case node grouping
 155    because after the tree optimizers have run such cleanups may
 156    be necessary.  */
 157
 158 static unsigned int
 159 execute_cleanup_cfg_pre_ipa (void)
 160 {
 161   cleanup_tree_cfg ();
 162   return 0;
 163 }
 164
 165 struct gimple_opt_pass pass_cleanup_cfg =
 166 {
 167  {
 168   GIMPLE_PASS,
 169   "cleanup_cfg",                        /* name */
 170   NULL,                                 /* gate */
 171   execute_cleanup_cfg_pre_ipa,          /* 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   TODO_dump_func                        /* todo_flags_finish */
 181  }
 182 };
 183
 184
 185 /* Pass: cleanup the CFG just before expanding trees to RTL.
 186    This is just a round of label cleanups and case node grouping
 187    because after the tree optimizers have run such cleanups may
 188    be necessary.  */
 189
 190 static unsigned int
 191 execute_cleanup_cfg_post_optimizing (void)
 192 {
 193   fold_cond_expr_cond ();
 194   cleanup_tree_cfg ();
 195   cleanup_dead_labels ();
 196   group_case_labels ();
 197   return 0;
 198 }
 199
 200 struct gimple_opt_pass pass_cleanup_cfg_post_optimizing =
 201 {
 202  {
 203   GIMPLE_PASS,
 204   "final_cleanup",                      /* name */
 205   NULL,                                 /* gate */
 206   execute_cleanup_cfg_post_optimizing,  /* execute */
 207   NULL,                                 /* sub */
 208   NULL,                                 /* next */
 209   0,                                    /* static_pass_number */
 210   0,                                    /* tv_id */
 211   PROP_cfg,                             /* properties_required */
 212   0,                                    /* properties_provided */
 213   0,                                    /* properties_destroyed */
 214   0,                                    /* todo_flags_start */
 215   TODO_dump_func                        /* todo_flags_finish */
 216  }
 217 };
 218
 219 /* Pass: do the actions required to finish with tree-ssa optimization
 220    passes.  */
 221
 222 static unsigned int
 223 execute_free_datastructures (void)
 224 {
 225   free_dominance_info (CDI_DOMINATORS);
 226   free_dominance_info (CDI_POST_DOMINATORS);
 227
 228   /* Remove the ssa structures.  */
 229   if (cfun->gimple_df)
 230     delete_tree_ssa ();
 231   return 0;
 232 }
 233
 234 struct gimple_opt_pass pass_free_datastructures =
 235 {
 236  {
 237   GIMPLE_PASS,
 238   NULL,                                 /* name */
 239   NULL,                                 /* gate */
 240   execute_free_datastructures,                  /* execute */
 241   NULL,                                 /* sub */
 242   NULL,                                 /* next */
 243   0,                                    /* static_pass_number */
 244   0,                                    /* tv_id */
 245   PROP_cfg,                             /* properties_required */
 246   0,                                    /* properties_provided */
 247   0,                                    /* properties_destroyed */
 248   0,                                    /* todo_flags_start */
 249   0                                     /* todo_flags_finish */
 250  }
 251 };
 252 /* Pass: free cfg annotations.  */
 253
 254 static unsigned int
 255 execute_free_cfg_annotations (void)
 256 {
 257   /* And get rid of annotations we no longer need.  */
 258   delete_tree_cfg_annotations ();
 259
 260   return 0;
 261 }
 262
 263 struct gimple_opt_pass pass_free_cfg_annotations =
 264 {
 265  {
 266   GIMPLE_PASS,
 267   NULL,                                 /* name */
 268   NULL,                                 /* gate */
 269   execute_free_cfg_annotations,         /* execute */
 270   NULL,                                 /* sub */
 271   NULL,                                 /* next */
 272   0,                                    /* static_pass_number */
 273   0,                                    /* tv_id */
 274   PROP_cfg,                             /* properties_required */
 275   0,                                    /* properties_provided */
 276   0,                                    /* properties_destroyed */
 277   0,                                    /* todo_flags_start */
 278   0                                     /* todo_flags_finish */
 279  }
 280 };
 281
 282 /* Pass: fixup_cfg.  IPA passes, compilation of earlier functions or inlining
 283    might have changed some properties, such as marked functions nothrow.
 284    Remove redundant edges and basic blocks, and create new ones if necessary.
 285
 286    This pass can't be executed as stand alone pass from pass manager, because
 287    in between inlining and this fixup the verify_flow_info would fail.  */
 288
 289 unsigned int
 290 execute_fixup_cfg (void)
 291 {
 292   basic_block bb;
 293   gimple_stmt_iterator gsi;
 294   int todo = gimple_in_ssa_p (cfun) ? TODO_verify_ssa : 0;
 295
 296   if (cfun->eh)
 297     FOR_EACH_BB (bb)
 298       {
 299         for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
 300           {
 301             gimple stmt = gsi_stmt (gsi);
 302             tree decl = is_gimple_call (stmt)
 303                         ? gimple_call_fndecl (stmt)
 304                         : NULL;
 305
 306             if (decl
 307                 && gimple_call_flags (stmt) & (ECF_CONST
 308                                                | ECF_PURE
 309                                                | ECF_LOOPING_CONST_OR_PURE))
 310               {
 311                 if (gimple_in_ssa_p (cfun))
 312                   {
 313                     todo |= TODO_update_ssa | TODO_cleanup_cfg;
 314                     update_stmt (stmt);
 315                   }
 316               }
 317
 318             if (!stmt_could_throw_p (stmt) && lookup_stmt_eh_region (stmt))
 319               remove_stmt_from_eh_region (stmt);
 320           }
 321
 322         if (gimple_purge_dead_eh_edges (bb))
 323           todo |= TODO_cleanup_cfg;
 324       }
 325
 326   /* Dump a textual representation of the flowgraph.  */
 327   if (dump_file)
 328     gimple_dump_cfg (dump_file, dump_flags);
 329
 330   return todo;
 331 }
 332
 333 struct gimple_opt_pass pass_fixup_cfg =
 334 {
 335  {
 336   GIMPLE_PASS,
 337   NULL,                                 /* name */
 338   NULL,                                 /* gate */
 339   execute_fixup_cfg,            /* execute */
 340   NULL,                                 /* sub */
 341   NULL,                                 /* next */
 342   0,                                    /* static_pass_number */
 343   0,                                    /* tv_id */
 344   PROP_cfg,                             /* properties_required */
 345   0,                                    /* properties_provided */
 346   0,                                    /* properties_destroyed */
 347   0,                                    /* todo_flags_start */
 348   0                                     /* todo_flags_finish */
 349  }
 350 };
 351
 352 /* Do the actions required to initialize internal data structures used
 353    in tree-ssa optimization passes.  */
 354
 355 static unsigned int
 356 execute_init_datastructures (void)
 357 {
 358   /* Allocate hash tables, arrays and other structures.  */
 359   init_tree_ssa (cfun);
 360   return 0;
 361 }
 362
 363 struct gimple_opt_pass pass_init_datastructures =
 364 {
 365  {
 366   GIMPLE_PASS,
 367   NULL,                                 /* name */
 368   NULL,                                 /* gate */
 369   execute_init_datastructures,          /* execute */
 370   NULL,                                 /* sub */
 371   NULL,                                 /* next */
 372   0,                                    /* static_pass_number */
 373   0,                                    /* tv_id */
 374   PROP_cfg,                             /* properties_required */
 375   0,                                    /* properties_provided */
 376   0,                                    /* properties_destroyed */
 377   0,                                    /* todo_flags_start */
 378   0                                     /* todo_flags_finish */
 379  }
 380 };
 381
 382 void
 383 tree_lowering_passes (tree fn)
 384 {
 385   tree saved_current_function_decl = current_function_decl;
 386
 387   current_function_decl = fn;
 388   push_cfun (DECL_STRUCT_FUNCTION (fn));
 389   gimple_register_cfg_hooks ();
 390   bitmap_obstack_initialize (NULL);
 391   execute_pass_list (all_lowering_passes);
 392   if (optimize && cgraph_global_info_ready)
 393     execute_pass_list (pass_early_local_passes.pass.sub);
 394   free_dominance_info (CDI_POST_DOMINATORS);
 395   free_dominance_info (CDI_DOMINATORS);
 396   compact_blocks ();
 397   current_function_decl = saved_current_function_decl;
 398   bitmap_obstack_release (NULL);
 399   pop_cfun ();
 400 }
 401 \f
 402 /* For functions-as-trees languages, this performs all optimization and
 403    compilation for FNDECL.  */
 404
 405 void
 406 tree_rest_of_compilation (tree fndecl)
 407 {
 408   location_t saved_loc;
 409   struct cgraph_node *node;
 410
 411   timevar_push (TV_EXPAND);
 412
 413   gcc_assert (cgraph_global_info_ready);
 414
 415   node = cgraph_node (fndecl);
 416
 417   /* Initialize the default bitmap obstack.  */
 418   bitmap_obstack_initialize (NULL);
 419
 420   /* Initialize the RTL code for the function.  */
 421   current_function_decl = fndecl;
 422   saved_loc = input_location;
 423   input_location = DECL_SOURCE_LOCATION (fndecl);
 424   init_function_start (fndecl);
 425
 426   /* Even though we're inside a function body, we still don't want to
 427      call expand_expr to calculate the size of a variable-sized array.
 428      We haven't necessarily assigned RTL to all variables yet, so it's
 429      not safe to try to expand expressions involving them.  */
 430   cfun->dont_save_pending_sizes_p = 1;
 431
 432   gimple_register_cfg_hooks ();
 433
 434   bitmap_obstack_initialize (&reg_obstack); /* FIXME, only at RTL generation*/
 435   /* Perform all tree transforms and optimizations.  */
 436   execute_pass_list (all_passes);
 437
 438   bitmap_obstack_release (&reg_obstack);
 439
 440   /* Release the default bitmap obstack.  */
 441   bitmap_obstack_release (NULL);
 442
 443   set_cfun (NULL);
 444
 445   /* If requested, warn about function definitions where the function will
 446      return a value (usually of some struct or union type) which itself will
 447      take up a lot of stack space.  */
 448   if (warn_larger_than && !DECL_EXTERNAL (fndecl) && TREE_TYPE (fndecl))
 449     {
 450       tree ret_type = TREE_TYPE (TREE_TYPE (fndecl));
 451
 452       if (ret_type && TYPE_SIZE_UNIT (ret_type)
 453           && TREE_CODE (TYPE_SIZE_UNIT (ret_type)) == INTEGER_CST
 454           && 0 < compare_tree_int (TYPE_SIZE_UNIT (ret_type),
 455                                    larger_than_size))
 456         {
 457           unsigned int size_as_int
 458             = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (ret_type));
 459
 460           if (compare_tree_int (TYPE_SIZE_UNIT (ret_type), size_as_int) == 0)
 461             warning (OPT_Wlarger_than_eq, "size of return value of %q+D is %u bytes",
 462                      fndecl, size_as_int);
 463           else
 464             warning (OPT_Wlarger_than_eq, "size of return value of %q+D is larger than %wd bytes",
 465                      fndecl, larger_than_size);
 466         }
 467     }
 468
 469   gimple_set_body (fndecl, NULL);
 470   if (DECL_STRUCT_FUNCTION (fndecl) == 0
 471       && !cgraph_node (fndecl)->origin)
 472     {
 473       /* Stop pointing to the local nodes about to be freed.
 474          But DECL_INITIAL must remain nonzero so we know this
 475          was an actual function definition.
 476          For a nested function, this is done in c_pop_function_context.
 477          If rest_of_compilation set this to 0, leave it 0.  */
 478       if (DECL_INITIAL (fndecl) != 0)
 479         DECL_INITIAL (fndecl) = error_mark_node;
 480     }
 481
 482   input_location = saved_loc;
 483
 484   ggc_collect ();
 485   timevar_pop (TV_EXPAND);
 486 }