gcc/tree-optimize.c

   1 /* Top-level control of tree optimizations.
   2    Copyright 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009
   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   TV_NONE,                              /* 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   TV_NONE,                              /* 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   TV_NONE,                              /* 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   TV_NONE,                              /* 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   "optimized",                  /* name */
 205   NULL,                                 /* gate */
 206   execute_cleanup_cfg_post_optimizing,  /* execute */
 207   NULL,                                 /* sub */
 208   NULL,                                 /* next */
 209   0,                                    /* static_pass_number */
 210   TV_NONE,                              /* 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     | TODO_remove_unused_locals
 217  }
 218 };
 219
 220 /* Pass: do the actions required to finish with tree-ssa optimization
 221    passes.  */
 222
 223 unsigned int
 224 execute_free_datastructures (void)
 225 {
 226   free_dominance_info (CDI_DOMINATORS);
 227   free_dominance_info (CDI_POST_DOMINATORS);
 228
 229   /* Remove the ssa structures.  */
 230   if (cfun->gimple_df)
 231     delete_tree_ssa ();
 232
 233   /* And get rid of annotations we no longer need.  */
 234   delete_tree_cfg_annotations ();
 235
 236   return 0;
 237 }
 238
 239 /* Pass: fixup_cfg.  IPA passes, compilation of earlier functions or inlining
 240    might have changed some properties, such as marked functions nothrow.
 241    Remove redundant edges and basic blocks, and create new ones if necessary.
 242
 243    This pass can't be executed as stand alone pass from pass manager, because
 244    in between inlining and this fixup the verify_flow_info would fail.  */
 245
 246 unsigned int
 247 execute_fixup_cfg (void)
 248 {
 249   basic_block bb;
 250   gimple_stmt_iterator gsi;
 251   int todo = gimple_in_ssa_p (cfun) ? TODO_verify_ssa : 0;
 252
 253   if (cfun->eh)
 254     FOR_EACH_BB (bb)
 255       {
 256         for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
 257           {
 258             gimple stmt = gsi_stmt (gsi);
 259             tree decl = is_gimple_call (stmt)
 260                         ? gimple_call_fndecl (stmt)
 261                         : NULL;
 262
 263             if (decl
 264                 && gimple_call_flags (stmt) & (ECF_CONST
 265                                                | ECF_PURE
 266                                                | ECF_LOOPING_CONST_OR_PURE))
 267               {
 268                 if (gimple_in_ssa_p (cfun))
 269                   {
 270                     todo |= TODO_update_ssa | TODO_cleanup_cfg;
 271                     mark_symbols_for_renaming (stmt);
 272                     update_stmt (stmt);
 273                   }
 274               }
 275
 276             if (!stmt_could_throw_p (stmt) && lookup_stmt_eh_region (stmt))
 277               remove_stmt_from_eh_region (stmt);
 278           }
 279
 280         if (gimple_purge_dead_eh_edges (bb))
 281           todo |= TODO_cleanup_cfg;
 282       }
 283
 284   /* Dump a textual representation of the flowgraph.  */
 285   if (dump_file)
 286     gimple_dump_cfg (dump_file, dump_flags);
 287
 288   return todo;
 289 }
 290
 291 struct gimple_opt_pass pass_fixup_cfg =
 292 {
 293  {
 294   GIMPLE_PASS,
 295   NULL,                                 /* name */
 296   NULL,                                 /* gate */
 297   execute_fixup_cfg,            /* execute */
 298   NULL,                                 /* sub */
 299   NULL,                                 /* next */
 300   0,                                    /* static_pass_number */
 301   TV_NONE,                              /* tv_id */
 302   PROP_cfg,                             /* properties_required */
 303   0,                                    /* properties_provided */
 304   0,                                    /* properties_destroyed */
 305   0,                                    /* todo_flags_start */
 306   0                                     /* todo_flags_finish */
 307  }
 308 };
 309
 310 /* Do the actions required to initialize internal data structures used
 311    in tree-ssa optimization passes.  */
 312
 313 static unsigned int
 314 execute_init_datastructures (void)
 315 {
 316   /* Allocate hash tables, arrays and other structures.  */
 317   init_tree_ssa (cfun);
 318   return 0;
 319 }
 320
 321 struct gimple_opt_pass pass_init_datastructures =
 322 {
 323  {
 324   GIMPLE_PASS,
 325   NULL,                                 /* name */
 326   NULL,                                 /* gate */
 327   execute_init_datastructures,          /* execute */
 328   NULL,                                 /* sub */
 329   NULL,                                 /* next */
 330   0,                                    /* static_pass_number */
 331   TV_NONE,                              /* tv_id */
 332   PROP_cfg,                             /* properties_required */
 333   0,                                    /* properties_provided */
 334   0,                                    /* properties_destroyed */
 335   0,                                    /* todo_flags_start */
 336   0                                     /* todo_flags_finish */
 337  }
 338 };
 339
 340 void
 341 tree_lowering_passes (tree fn)
 342 {
 343   tree saved_current_function_decl = current_function_decl;
 344
 345   current_function_decl = fn;
 346   push_cfun (DECL_STRUCT_FUNCTION (fn));
 347   gimple_register_cfg_hooks ();
 348   bitmap_obstack_initialize (NULL);
 349   execute_pass_list (all_lowering_passes);
 350   if (optimize && cgraph_global_info_ready)
 351     execute_pass_list (pass_early_local_passes.pass.sub);
 352   free_dominance_info (CDI_POST_DOMINATORS);
 353   free_dominance_info (CDI_DOMINATORS);
 354   compact_blocks ();
 355   current_function_decl = saved_current_function_decl;
 356   bitmap_obstack_release (NULL);
 357   pop_cfun ();
 358 }
 359 \f
 360 /* For functions-as-trees languages, this performs all optimization and
 361    compilation for FNDECL.  */
 362
 363 void
 364 tree_rest_of_compilation (tree fndecl)
 365 {
 366   location_t saved_loc;
 367   struct cgraph_node *node;
 368
 369   timevar_push (TV_EXPAND);
 370
 371   gcc_assert (cgraph_global_info_ready);
 372
 373   node = cgraph_node (fndecl);
 374
 375   /* Initialize the default bitmap obstack.  */
 376   bitmap_obstack_initialize (NULL);
 377
 378   /* Initialize the RTL code for the function.  */
 379   current_function_decl = fndecl;
 380   saved_loc = input_location;
 381   input_location = DECL_SOURCE_LOCATION (fndecl);
 382   init_function_start (fndecl);
 383
 384   /* Even though we're inside a function body, we still don't want to
 385      call expand_expr to calculate the size of a variable-sized array.
 386      We haven't necessarily assigned RTL to all variables yet, so it's
 387      not safe to try to expand expressions involving them.  */
 388   cfun->dont_save_pending_sizes_p = 1;
 389
 390   gimple_register_cfg_hooks ();
 391
 392   bitmap_obstack_initialize (&reg_obstack); /* FIXME, only at RTL generation*/
 393   /* Perform all tree transforms and optimizations.  */
 394   execute_pass_list (all_passes);
 395
 396   bitmap_obstack_release (&reg_obstack);
 397
 398   /* Release the default bitmap obstack.  */
 399   bitmap_obstack_release (NULL);
 400
 401   set_cfun (NULL);
 402
 403   /* If requested, warn about function definitions where the function will
 404      return a value (usually of some struct or union type) which itself will
 405      take up a lot of stack space.  */
 406   if (warn_larger_than && !DECL_EXTERNAL (fndecl) && TREE_TYPE (fndecl))
 407     {
 408       tree ret_type = TREE_TYPE (TREE_TYPE (fndecl));
 409
 410       if (ret_type && TYPE_SIZE_UNIT (ret_type)
 411           && TREE_CODE (TYPE_SIZE_UNIT (ret_type)) == INTEGER_CST
 412           && 0 < compare_tree_int (TYPE_SIZE_UNIT (ret_type),
 413                                    larger_than_size))
 414         {
 415           unsigned int size_as_int
 416             = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (ret_type));
 417
 418           if (compare_tree_int (TYPE_SIZE_UNIT (ret_type), size_as_int) == 0)
 419             warning (OPT_Wlarger_than_eq, "size of return value of %q+D is %u bytes",
 420                      fndecl, size_as_int);
 421           else
 422             warning (OPT_Wlarger_than_eq, "size of return value of %q+D is larger than %wd bytes",
 423                      fndecl, larger_than_size);
 424         }
 425     }
 426
 427   gimple_set_body (fndecl, NULL);
 428   if (DECL_STRUCT_FUNCTION (fndecl) == 0
 429       && !cgraph_node (fndecl)->origin)
 430     {
 431       /* Stop pointing to the local nodes about to be freed.
 432          But DECL_INITIAL must remain nonzero so we know this
 433          was an actual function definition.
 434          For a nested function, this is done in c_pop_function_context.
 435          If rest_of_compilation set this to 0, leave it 0.  */
 436       if (DECL_INITIAL (fndecl) != 0)
 437         DECL_INITIAL (fndecl) = error_mark_node;
 438     }
 439
 440   input_location = saved_loc;
 441
 442   ggc_collect ();
 443   timevar_pop (TV_EXPAND);
 444 }