gcc/tree-optimize.c

   1 /* Top-level control of tree optimizations.
   2    Copyright 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010
   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 "tm_p.h"
  28 #include "basic-block.h"
  29 #include "output.h"
  30 #include "flags.h"
  31 #include "tree-flow.h"
  32 #include "tree-dump.h"
  33 #include "timevar.h"
  34 #include "function.h"
  35 #include "langhooks.h"
  36 #include "toplev.h"
  37 #include "flags.h"
  38 #include "cgraph.h"
  39 #include "tree-inline.h"
  40 #include "tree-mudflap.h"
  41 #include "tree-pass.h"
  42 #include "ggc.h"
  43 #include "cgraph.h"
  44 #include "graph.h"
  45 #include "cfgloop.h"
  46 #include "except.h"
  47 #include "plugin.h"
  48 #include "regset.h"     /* FIXME: For reg_obstack.  */
  49
  50 /* Gate: execute, or not, all of the non-trivial optimizations.  */
  51
  52 static bool
  53 gate_all_optimizations (void)
  54 {
  55   return (optimize >= 1
  56           /* Don't bother doing anything if the program has errors.
  57              We have to pass down the queue if we already went into SSA */
  58           && (!seen_error () || gimple_in_ssa_p (cfun)));
  59 }
  60
  61 struct gimple_opt_pass pass_all_optimizations =
  62 {
  63  {
  64   GIMPLE_PASS,
  65   "*all_optimizations",                 /* name */
  66   gate_all_optimizations,               /* gate */
  67   NULL,                                 /* execute */
  68   NULL,                                 /* sub */
  69   NULL,                                 /* next */
  70   0,                                    /* static_pass_number */
  71   TV_NONE,                              /* tv_id */
  72   0,                                    /* properties_required */
  73   0,                                    /* properties_provided */
  74   0,                                    /* properties_destroyed */
  75   0,                                    /* todo_flags_start */
  76   0                                     /* todo_flags_finish */
  77  }
  78 };
  79
  80 /* Gate: execute, or not, all of the non-trivial optimizations.  */
  81
  82 static bool
  83 gate_all_early_local_passes (void)
  84 {
  85           /* Don't bother doing anything if the program has errors.  */
  86   return (!seen_error () && !in_lto_p);
  87 }
  88
  89 struct simple_ipa_opt_pass pass_early_local_passes =
  90 {
  91  {
  92   SIMPLE_IPA_PASS,
  93   "early_local_cleanups",               /* name */
  94   gate_all_early_local_passes,          /* gate */
  95   NULL,                                 /* execute */
  96   NULL,                                 /* sub */
  97   NULL,                                 /* next */
  98   0,                                    /* static_pass_number */
  99   TV_NONE,                              /* tv_id */
 100   0,                                    /* properties_required */
 101   0,                                    /* properties_provided */
 102   0,                                    /* properties_destroyed */
 103   0,                                    /* todo_flags_start */
 104   TODO_remove_functions                 /* todo_flags_finish */
 105  }
 106 };
 107
 108 static unsigned int
 109 execute_early_local_optimizations (void)
 110 {
 111   /* First time we start with early optimization we need to advance
 112      cgraph state so newly inserted functions are also early optimized.
 113      However we execute early local optimizations for lately inserted
 114      functions, in that case don't reset cgraph state back to IPA_SSA.  */
 115   if (cgraph_state < CGRAPH_STATE_IPA_SSA)
 116     cgraph_state = CGRAPH_STATE_IPA_SSA;
 117   return 0;
 118 }
 119
 120 /* Gate: execute, or not, all of the non-trivial optimizations.  */
 121
 122 static bool
 123 gate_all_early_optimizations (void)
 124 {
 125   return (optimize >= 1
 126           /* Don't bother doing anything if the program has errors.  */
 127           && !seen_error ());
 128 }
 129
 130 struct gimple_opt_pass pass_all_early_optimizations =
 131 {
 132  {
 133   GIMPLE_PASS,
 134   "early_optimizations",                /* name */
 135   gate_all_early_optimizations,         /* gate */
 136   execute_early_local_optimizations,    /* execute */
 137   NULL,                                 /* sub */
 138   NULL,                                 /* next */
 139   0,                                    /* static_pass_number */
 140   TV_NONE,                              /* tv_id */
 141   0,                                    /* properties_required */
 142   0,                                    /* properties_provided */
 143   0,                                    /* properties_destroyed */
 144   0,                                    /* todo_flags_start */
 145   0                                     /* todo_flags_finish */
 146  }
 147 };
 148
 149 /* Pass: cleanup the CFG just before expanding trees to RTL.
 150    This is just a round of label cleanups and case node grouping
 151    because after the tree optimizers have run such cleanups may
 152    be necessary.  */
 153
 154 static unsigned int
 155 execute_cleanup_cfg_pre_ipa (void)
 156 {
 157   cleanup_tree_cfg ();
 158   return 0;
 159 }
 160
 161 struct gimple_opt_pass pass_cleanup_cfg =
 162 {
 163  {
 164   GIMPLE_PASS,
 165   "cleanup_cfg",                        /* name */
 166   NULL,                                 /* gate */
 167   execute_cleanup_cfg_pre_ipa,          /* execute */
 168   NULL,                                 /* sub */
 169   NULL,                                 /* next */
 170   0,                                    /* static_pass_number */
 171   TV_NONE,                              /* tv_id */
 172   PROP_cfg,                             /* properties_required */
 173   0,                                    /* properties_provided */
 174   0,                                    /* properties_destroyed */
 175   0,                                    /* todo_flags_start */
 176   TODO_dump_func                        /* todo_flags_finish */
 177  }
 178 };
 179
 180
 181 /* Pass: cleanup the CFG just before expanding trees to RTL.
 182    This is just a round of label cleanups and case node grouping
 183    because after the tree optimizers have run such cleanups may
 184    be necessary.  */
 185
 186 static unsigned int
 187 execute_cleanup_cfg_post_optimizing (void)
 188 {
 189   fold_cond_expr_cond ();
 190   cleanup_tree_cfg ();
 191   cleanup_dead_labels ();
 192   group_case_labels ();
 193   return 0;
 194 }
 195
 196 struct gimple_opt_pass pass_cleanup_cfg_post_optimizing =
 197 {
 198  {
 199   GIMPLE_PASS,
 200   "optimized",                          /* name */
 201   NULL,                                 /* gate */
 202   execute_cleanup_cfg_post_optimizing,  /* execute */
 203   NULL,                                 /* sub */
 204   NULL,                                 /* next */
 205   0,                                    /* static_pass_number */
 206   TV_NONE,                              /* tv_id */
 207   PROP_cfg,                             /* properties_required */
 208   0,                                    /* properties_provided */
 209   0,                                    /* properties_destroyed */
 210   0,                                    /* todo_flags_start */
 211   TODO_dump_func                        /* todo_flags_finish */
 212     | TODO_remove_unused_locals
 213  }
 214 };
 215
 216 /* Pass: do the actions required to finish with tree-ssa optimization
 217    passes.  */
 218
 219 unsigned int
 220 execute_free_datastructures (void)
 221 {
 222   free_dominance_info (CDI_DOMINATORS);
 223   free_dominance_info (CDI_POST_DOMINATORS);
 224
 225   /* And get rid of annotations we no longer need.  */
 226   delete_tree_cfg_annotations ();
 227
 228   return 0;
 229 }
 230
 231 /* Pass: fixup_cfg.  IPA passes, compilation of earlier functions or inlining
 232    might have changed some properties, such as marked functions nothrow,
 233    pure, const or noreturn.
 234    Remove redundant edges and basic blocks, and create new ones if necessary.
 235
 236    This pass can't be executed as stand alone pass from pass manager, because
 237    in between inlining and this fixup the verify_flow_info would fail.  */
 238
 239 unsigned int
 240 execute_fixup_cfg (void)
 241 {
 242   basic_block bb;
 243   gimple_stmt_iterator gsi;
 244   int todo = gimple_in_ssa_p (cfun) ? TODO_verify_ssa : 0;
 245   gcov_type count_scale;
 246   edge e;
 247   edge_iterator ei;
 248
 249   if (ENTRY_BLOCK_PTR->count)
 250     count_scale = (cgraph_node (current_function_decl)->count * REG_BR_PROB_BASE
 251                    + ENTRY_BLOCK_PTR->count / 2) / ENTRY_BLOCK_PTR->count;
 252   else
 253     count_scale = REG_BR_PROB_BASE;
 254
 255   ENTRY_BLOCK_PTR->count = cgraph_node (current_function_decl)->count;
 256   EXIT_BLOCK_PTR->count = (EXIT_BLOCK_PTR->count * count_scale
 257                            + REG_BR_PROB_BASE / 2) / REG_BR_PROB_BASE;
 258
 259   FOR_EACH_BB (bb)
 260     {
 261       bb->count = (bb->count * count_scale
 262                    + REG_BR_PROB_BASE / 2) / REG_BR_PROB_BASE;
 263       for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
 264         {
 265           gimple stmt = gsi_stmt (gsi);
 266           tree decl = is_gimple_call (stmt)
 267                       ? gimple_call_fndecl (stmt)
 268                       : NULL;
 269           if (decl)
 270             {
 271               int flags = gimple_call_flags (stmt);
 272               if (flags & (ECF_CONST | ECF_PURE | ECF_LOOPING_CONST_OR_PURE))
 273                 {
 274                   if (gimple_in_ssa_p (cfun))
 275                     {
 276                       todo |= TODO_update_ssa | TODO_cleanup_cfg;
 277                       mark_symbols_for_renaming (stmt);
 278                       update_stmt (stmt);
 279                     }
 280                 }
 281
 282               if (flags & ECF_NORETURN
 283                   && fixup_noreturn_call (stmt))
 284                 todo |= TODO_cleanup_cfg;
 285              }
 286
 287           maybe_clean_eh_stmt (stmt);
 288         }
 289
 290       if (gimple_purge_dead_eh_edges (bb))
 291         todo |= TODO_cleanup_cfg;
 292       FOR_EACH_EDGE (e, ei, bb->succs)
 293         e->count = (e->count * count_scale
 294                     + REG_BR_PROB_BASE / 2) / REG_BR_PROB_BASE;
 295     }
 296   if (count_scale != REG_BR_PROB_BASE)
 297     compute_function_frequency ();
 298
 299   /* We just processed all calls.  */
 300   if (cfun->gimple_df)
 301     {
 302       VEC_free (gimple, gc, MODIFIED_NORETURN_CALLS (cfun));
 303       MODIFIED_NORETURN_CALLS (cfun) = NULL;
 304     }
 305
 306   /* Dump a textual representation of the flowgraph.  */
 307   if (dump_file)
 308     gimple_dump_cfg (dump_file, dump_flags);
 309
 310   return todo;
 311 }
 312
 313 struct gimple_opt_pass pass_fixup_cfg =
 314 {
 315  {
 316   GIMPLE_PASS,
 317   "*free_cfg_annotations",              /* name */
 318   NULL,                                 /* gate */
 319   execute_fixup_cfg,                    /* execute */
 320   NULL,                                 /* sub */
 321   NULL,                                 /* next */
 322   0,                                    /* static_pass_number */
 323   TV_NONE,                              /* tv_id */
 324   PROP_cfg,                             /* properties_required */
 325   0,                                    /* properties_provided */
 326   0,                                    /* properties_destroyed */
 327   0,                                    /* todo_flags_start */
 328   0                                     /* todo_flags_finish */
 329  }
 330 };
 331
 332 /* Do the actions required to initialize internal data structures used
 333    in tree-ssa optimization passes.  */
 334
 335 static unsigned int
 336 execute_init_datastructures (void)
 337 {
 338   /* Allocate hash tables, arrays and other structures.  */
 339   init_tree_ssa (cfun);
 340   return 0;
 341 }
 342
 343 struct gimple_opt_pass pass_init_datastructures =
 344 {
 345  {
 346   GIMPLE_PASS,
 347   "*init_datastructures",               /* name */
 348   NULL,                                 /* gate */
 349   execute_init_datastructures,          /* execute */
 350   NULL,                                 /* sub */
 351   NULL,                                 /* next */
 352   0,                                    /* static_pass_number */
 353   TV_NONE,                              /* tv_id */
 354   PROP_cfg,                             /* properties_required */
 355   0,                                    /* properties_provided */
 356   0,                                    /* properties_destroyed */
 357   0,                                    /* todo_flags_start */
 358   0                                     /* todo_flags_finish */
 359  }
 360 };
 361
 362 void
 363 tree_lowering_passes (tree fn)
 364 {
 365   tree saved_current_function_decl = current_function_decl;
 366
 367   current_function_decl = fn;
 368   push_cfun (DECL_STRUCT_FUNCTION (fn));
 369   gimple_register_cfg_hooks ();
 370   bitmap_obstack_initialize (NULL);
 371   execute_pass_list (all_lowering_passes);
 372   if (optimize && cgraph_global_info_ready)
 373     execute_pass_list (pass_early_local_passes.pass.sub);
 374   free_dominance_info (CDI_POST_DOMINATORS);
 375   free_dominance_info (CDI_DOMINATORS);
 376   compact_blocks ();
 377   current_function_decl = saved_current_function_decl;
 378   bitmap_obstack_release (NULL);
 379   pop_cfun ();
 380 }
 381 \f
 382 /* For functions-as-trees languages, this performs all optimization and
 383    compilation for FNDECL.  */
 384
 385 void
 386 tree_rest_of_compilation (tree fndecl)
 387 {
 388   location_t saved_loc;
 389
 390   timevar_push (TV_EXPAND);
 391
 392   gcc_assert (cgraph_global_info_ready);
 393
 394   /* Initialize the default bitmap obstack.  */
 395   bitmap_obstack_initialize (NULL);
 396
 397   /* Initialize the RTL code for the function.  */
 398   current_function_decl = fndecl;
 399   saved_loc = input_location;
 400   input_location = DECL_SOURCE_LOCATION (fndecl);
 401   init_function_start (fndecl);
 402
 403   /* Even though we're inside a function body, we still don't want to
 404      call expand_expr to calculate the size of a variable-sized array.
 405      We haven't necessarily assigned RTL to all variables yet, so it's
 406      not safe to try to expand expressions involving them.  */
 407   cfun->dont_save_pending_sizes_p = 1;
 408
 409   gimple_register_cfg_hooks ();
 410
 411   bitmap_obstack_initialize (&reg_obstack); /* FIXME, only at RTL generation*/
 412
 413   execute_all_ipa_transforms ();
 414
 415   /* Perform all tree transforms and optimizations.  */
 416
 417   /* Signal the start of passes.  */
 418   invoke_plugin_callbacks (PLUGIN_ALL_PASSES_START, NULL);
 419
 420   execute_pass_list (all_passes);
 421
 422   /* Signal the end of passes.  */
 423   invoke_plugin_callbacks (PLUGIN_ALL_PASSES_END, NULL);
 424
 425   bitmap_obstack_release (&reg_obstack);
 426
 427   /* Release the default bitmap obstack.  */
 428   bitmap_obstack_release (NULL);
 429
 430   set_cfun (NULL);
 431
 432   /* If requested, warn about function definitions where the function will
 433      return a value (usually of some struct or union type) which itself will
 434      take up a lot of stack space.  */
 435   if (warn_larger_than && !DECL_EXTERNAL (fndecl) && TREE_TYPE (fndecl))
 436     {
 437       tree ret_type = TREE_TYPE (TREE_TYPE (fndecl));
 438
 439       if (ret_type && TYPE_SIZE_UNIT (ret_type)
 440           && TREE_CODE (TYPE_SIZE_UNIT (ret_type)) == INTEGER_CST
 441           && 0 < compare_tree_int (TYPE_SIZE_UNIT (ret_type),
 442                                    larger_than_size))
 443         {
 444           unsigned int size_as_int
 445             = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (ret_type));
 446
 447           if (compare_tree_int (TYPE_SIZE_UNIT (ret_type), size_as_int) == 0)
 448             warning (OPT_Wlarger_than_eq, "size of return value of %q+D is %u bytes",
 449                      fndecl, size_as_int);
 450           else
 451             warning (OPT_Wlarger_than_eq, "size of return value of %q+D is larger than %wd bytes",
 452                      fndecl, larger_than_size);
 453         }
 454     }
 455
 456   gimple_set_body (fndecl, NULL);
 457   if (DECL_STRUCT_FUNCTION (fndecl) == 0
 458       && !cgraph_node (fndecl)->origin)
 459     {
 460       /* Stop pointing to the local nodes about to be freed.
 461          But DECL_INITIAL must remain nonzero so we know this
 462          was an actual function definition.
 463          For a nested function, this is done in c_pop_function_context.
 464          If rest_of_compilation set this to 0, leave it 0.  */
 465       if (DECL_INITIAL (fndecl) != 0)
 466         DECL_INITIAL (fndecl) = error_mark_node;
 467     }
 468
 469   input_location = saved_loc;
 470
 471   ggc_collect ();
 472   timevar_pop (TV_EXPAND);
 473 }