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   cfun->after_inlining = true;
 297   cfun->always_inline_functions_inlined = true;
 298
 299   if (cfun->eh)
 300     FOR_EACH_BB (bb)
 301       {
 302         for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
 303           {
 304             gimple stmt = gsi_stmt (gsi);
 305             tree decl = is_gimple_call (stmt)
 306                         ? gimple_call_fndecl (stmt)
 307                         : NULL;
 308
 309             if (decl
 310                 && gimple_call_flags (stmt) & (ECF_CONST
 311                                                | ECF_PURE
 312                                                | ECF_LOOPING_CONST_OR_PURE))
 313               {
 314                 if (gimple_in_ssa_p (cfun))
 315                   {
 316                     todo |= TODO_update_ssa | TODO_cleanup_cfg;
 317                     update_stmt (stmt);
 318                   }
 319               }
 320
 321             if (!stmt_could_throw_p (stmt) && lookup_stmt_eh_region (stmt))
 322               remove_stmt_from_eh_region (stmt);
 323           }
 324
 325         if (gimple_purge_dead_eh_edges (bb))
 326           todo |= TODO_cleanup_cfg;
 327       }
 328
 329   /* Dump a textual representation of the flowgraph.  */
 330   if (dump_file)
 331     gimple_dump_cfg (dump_file, dump_flags);
 332
 333   return todo;
 334 }
 335
 336 /* Do the actions required to initialize internal data structures used
 337    in tree-ssa optimization passes.  */
 338
 339 static unsigned int
 340 execute_init_datastructures (void)
 341 {
 342   /* Allocate hash tables, arrays and other structures.  */
 343   init_tree_ssa (cfun);
 344   return 0;
 345 }
 346
 347 struct gimple_opt_pass pass_init_datastructures =
 348 {
 349  {
 350   GIMPLE_PASS,
 351   NULL,                                 /* name */
 352   NULL,                                 /* gate */
 353   execute_init_datastructures,          /* execute */
 354   NULL,                                 /* sub */
 355   NULL,                                 /* next */
 356   0,                                    /* static_pass_number */
 357   0,                                    /* tv_id */
 358   PROP_cfg,                             /* properties_required */
 359   0,                                    /* properties_provided */
 360   0,                                    /* properties_destroyed */
 361   0,                                    /* todo_flags_start */
 362   0                                     /* todo_flags_finish */
 363  }
 364 };
 365
 366 void
 367 tree_lowering_passes (tree fn)
 368 {
 369   tree saved_current_function_decl = current_function_decl;
 370
 371   current_function_decl = fn;
 372   push_cfun (DECL_STRUCT_FUNCTION (fn));
 373   gimple_register_cfg_hooks ();
 374   bitmap_obstack_initialize (NULL);
 375   execute_pass_list (all_lowering_passes);
 376   if (optimize && cgraph_global_info_ready)
 377     execute_pass_list (pass_early_local_passes.pass.sub);
 378   free_dominance_info (CDI_POST_DOMINATORS);
 379   free_dominance_info (CDI_DOMINATORS);
 380   compact_blocks ();
 381   current_function_decl = saved_current_function_decl;
 382   bitmap_obstack_release (NULL);
 383   pop_cfun ();
 384 }
 385 \f
 386 /* For functions-as-trees languages, this performs all optimization and
 387    compilation for FNDECL.  */
 388
 389 void
 390 tree_rest_of_compilation (tree fndecl)
 391 {
 392   location_t saved_loc;
 393   struct cgraph_node *node;
 394
 395   timevar_push (TV_EXPAND);
 396
 397   gcc_assert (cgraph_global_info_ready);
 398
 399   node = cgraph_node (fndecl);
 400
 401   /* Initialize the default bitmap obstack.  */
 402   bitmap_obstack_initialize (NULL);
 403
 404   /* Initialize the RTL code for the function.  */
 405   current_function_decl = fndecl;
 406   saved_loc = input_location;
 407   input_location = DECL_SOURCE_LOCATION (fndecl);
 408   init_function_start (fndecl);
 409
 410   /* Even though we're inside a function body, we still don't want to
 411      call expand_expr to calculate the size of a variable-sized array.
 412      We haven't necessarily assigned RTL to all variables yet, so it's
 413      not safe to try to expand expressions involving them.  */
 414   cfun->dont_save_pending_sizes_p = 1;
 415
 416   gimple_register_cfg_hooks ();
 417
 418   bitmap_obstack_initialize (&reg_obstack); /* FIXME, only at RTL generation*/
 419   /* Perform all tree transforms and optimizations.  */
 420   execute_pass_list (all_passes);
 421
 422   bitmap_obstack_release (&reg_obstack);
 423
 424   /* Release the default bitmap obstack.  */
 425   bitmap_obstack_release (NULL);
 426
 427   set_cfun (NULL);
 428
 429   /* If requested, warn about function definitions where the function will
 430      return a value (usually of some struct or union type) which itself will
 431      take up a lot of stack space.  */
 432   if (warn_larger_than && !DECL_EXTERNAL (fndecl) && TREE_TYPE (fndecl))
 433     {
 434       tree ret_type = TREE_TYPE (TREE_TYPE (fndecl));
 435
 436       if (ret_type && TYPE_SIZE_UNIT (ret_type)
 437           && TREE_CODE (TYPE_SIZE_UNIT (ret_type)) == INTEGER_CST
 438           && 0 < compare_tree_int (TYPE_SIZE_UNIT (ret_type),
 439                                    larger_than_size))
 440         {
 441           unsigned int size_as_int
 442             = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (ret_type));
 443
 444           if (compare_tree_int (TYPE_SIZE_UNIT (ret_type), size_as_int) == 0)
 445             warning (OPT_Wlarger_than_eq, "size of return value of %q+D is %u bytes",
 446                      fndecl, size_as_int);
 447           else
 448             warning (OPT_Wlarger_than_eq, "size of return value of %q+D is larger than %wd bytes",
 449                      fndecl, larger_than_size);
 450         }
 451     }
 452
 453   gimple_set_body (fndecl, NULL);
 454   if (DECL_STRUCT_FUNCTION (fndecl) == 0
 455       && !cgraph_node (fndecl)->origin)
 456     {
 457       /* Stop pointing to the local nodes about to be freed.
 458          But DECL_INITIAL must remain nonzero so we know this
 459          was an actual function definition.
 460          For a nested function, this is done in c_pop_function_context.
 461          If rest_of_compilation set this to 0, leave it 0.  */
 462       if (DECL_INITIAL (fndecl) != 0)
 463         DECL_INITIAL (fndecl) = error_mark_node;
 464     }
 465
 466   input_location = saved_loc;
 467
 468   ggc_collect ();
 469   timevar_pop (TV_EXPAND);
 470 }