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   "*all_optimizations",                 /* 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 && !in_lto_p);
  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   /* And get rid of annotations we no longer need.  */
 230   delete_tree_cfg_annotations ();
 231
 232   return 0;
 233 }
 234
 235 /* Pass: fixup_cfg.  IPA passes, compilation of earlier functions or inlining
 236    might have changed some properties, such as marked functions nothrow.
 237    Remove redundant edges and basic blocks, and create new ones if necessary.
 238
 239    This pass can't be executed as stand alone pass from pass manager, because
 240    in between inlining and this fixup the verify_flow_info would fail.  */
 241
 242 unsigned int
 243 execute_fixup_cfg (void)
 244 {
 245   basic_block bb;
 246   gimple_stmt_iterator gsi;
 247   int todo = gimple_in_ssa_p (cfun) ? TODO_verify_ssa : 0;
 248   gcov_type count_scale;
 249   edge e;
 250   edge_iterator ei;
 251
 252   if (ENTRY_BLOCK_PTR->count)
 253     count_scale = (cgraph_node (current_function_decl)->count * REG_BR_PROB_BASE
 254                    + ENTRY_BLOCK_PTR->count / 2) / ENTRY_BLOCK_PTR->count;
 255   else
 256     count_scale = REG_BR_PROB_BASE;
 257
 258   FOR_EACH_BB (bb)
 259     {
 260       bb->count = (bb->count * count_scale
 261                    + REG_BR_PROB_BASE / 2) / REG_BR_PROB_BASE;
 262       for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
 263         {
 264           gimple stmt = gsi_stmt (gsi);
 265           tree decl = is_gimple_call (stmt)
 266                       ? gimple_call_fndecl (stmt)
 267                       : NULL;
 268
 269           if (decl
 270               && gimple_call_flags (stmt) & (ECF_CONST
 271                                              | ECF_PURE
 272                                              | 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           maybe_clean_eh_stmt (stmt);
 283         }
 284
 285       if (gimple_purge_dead_eh_edges (bb))
 286         todo |= TODO_cleanup_cfg;
 287       FOR_EACH_EDGE (e, ei, bb->succs)
 288         e->count = (e->count * count_scale
 289                     + REG_BR_PROB_BASE / 2) / REG_BR_PROB_BASE;
 290     }
 291   if (count_scale != REG_BR_PROB_BASE)
 292     compute_function_frequency ();
 293
 294   /* Dump a textual representation of the flowgraph.  */
 295   if (dump_file)
 296     gimple_dump_cfg (dump_file, dump_flags);
 297
 298   return todo;
 299 }
 300
 301 struct gimple_opt_pass pass_fixup_cfg =
 302 {
 303  {
 304   GIMPLE_PASS,
 305   "*free_cfg_annotations",              /* name */
 306   NULL,                                 /* gate */
 307   execute_fixup_cfg,                    /* execute */
 308   NULL,                                 /* sub */
 309   NULL,                                 /* next */
 310   0,                                    /* static_pass_number */
 311   TV_NONE,                              /* tv_id */
 312   PROP_cfg,                             /* properties_required */
 313   0,                                    /* properties_provided */
 314   0,                                    /* properties_destroyed */
 315   0,                                    /* todo_flags_start */
 316   0                                     /* todo_flags_finish */
 317  }
 318 };
 319
 320 /* Do the actions required to initialize internal data structures used
 321    in tree-ssa optimization passes.  */
 322
 323 static unsigned int
 324 execute_init_datastructures (void)
 325 {
 326   /* Allocate hash tables, arrays and other structures.  */
 327   init_tree_ssa (cfun);
 328   return 0;
 329 }
 330
 331 struct gimple_opt_pass pass_init_datastructures =
 332 {
 333  {
 334   GIMPLE_PASS,
 335   "*init_datastructures",               /* name */
 336   NULL,                                 /* gate */
 337   execute_init_datastructures,          /* execute */
 338   NULL,                                 /* sub */
 339   NULL,                                 /* next */
 340   0,                                    /* static_pass_number */
 341   TV_NONE,                              /* tv_id */
 342   PROP_cfg,                             /* properties_required */
 343   0,                                    /* properties_provided */
 344   0,                                    /* properties_destroyed */
 345   0,                                    /* todo_flags_start */
 346   0                                     /* todo_flags_finish */
 347  }
 348 };
 349
 350 void
 351 tree_lowering_passes (tree fn)
 352 {
 353   tree saved_current_function_decl = current_function_decl;
 354
 355   current_function_decl = fn;
 356   push_cfun (DECL_STRUCT_FUNCTION (fn));
 357   gimple_register_cfg_hooks ();
 358   bitmap_obstack_initialize (NULL);
 359   execute_pass_list (all_lowering_passes);
 360   if (optimize && cgraph_global_info_ready)
 361     execute_pass_list (pass_early_local_passes.pass.sub);
 362   free_dominance_info (CDI_POST_DOMINATORS);
 363   free_dominance_info (CDI_DOMINATORS);
 364   compact_blocks ();
 365   current_function_decl = saved_current_function_decl;
 366   bitmap_obstack_release (NULL);
 367   pop_cfun ();
 368 }
 369 \f
 370 /* For functions-as-trees languages, this performs all optimization and
 371    compilation for FNDECL.  */
 372
 373 void
 374 tree_rest_of_compilation (tree fndecl)
 375 {
 376   location_t saved_loc;
 377   struct cgraph_node *node;
 378
 379   timevar_push (TV_EXPAND);
 380
 381   gcc_assert (cgraph_global_info_ready);
 382
 383   node = cgraph_node (fndecl);
 384
 385   /* Initialize the default bitmap obstack.  */
 386   bitmap_obstack_initialize (NULL);
 387
 388   /* Initialize the RTL code for the function.  */
 389   current_function_decl = fndecl;
 390   saved_loc = input_location;
 391   input_location = DECL_SOURCE_LOCATION (fndecl);
 392   init_function_start (fndecl);
 393
 394   /* Even though we're inside a function body, we still don't want to
 395      call expand_expr to calculate the size of a variable-sized array.
 396      We haven't necessarily assigned RTL to all variables yet, so it's
 397      not safe to try to expand expressions involving them.  */
 398   cfun->dont_save_pending_sizes_p = 1;
 399
 400   gimple_register_cfg_hooks ();
 401
 402   bitmap_obstack_initialize (&reg_obstack); /* FIXME, only at RTL generation*/
 403
 404   execute_all_ipa_transforms ();
 405
 406   /* Perform all tree transforms and optimizations.  */
 407   execute_pass_list (all_passes);
 408
 409   bitmap_obstack_release (&reg_obstack);
 410
 411   /* Release the default bitmap obstack.  */
 412   bitmap_obstack_release (NULL);
 413
 414   set_cfun (NULL);
 415
 416   /* If requested, warn about function definitions where the function will
 417      return a value (usually of some struct or union type) which itself will
 418      take up a lot of stack space.  */
 419   if (warn_larger_than && !DECL_EXTERNAL (fndecl) && TREE_TYPE (fndecl))
 420     {
 421       tree ret_type = TREE_TYPE (TREE_TYPE (fndecl));
 422
 423       if (ret_type && TYPE_SIZE_UNIT (ret_type)
 424           && TREE_CODE (TYPE_SIZE_UNIT (ret_type)) == INTEGER_CST
 425           && 0 < compare_tree_int (TYPE_SIZE_UNIT (ret_type),
 426                                    larger_than_size))
 427         {
 428           unsigned int size_as_int
 429             = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (ret_type));
 430
 431           if (compare_tree_int (TYPE_SIZE_UNIT (ret_type), size_as_int) == 0)
 432             warning (OPT_Wlarger_than_eq, "size of return value of %q+D is %u bytes",
 433                      fndecl, size_as_int);
 434           else
 435             warning (OPT_Wlarger_than_eq, "size of return value of %q+D is larger than %wd bytes",
 436                      fndecl, larger_than_size);
 437         }
 438     }
 439
 440   gimple_set_body (fndecl, NULL);
 441   if (DECL_STRUCT_FUNCTION (fndecl) == 0
 442       && !cgraph_node (fndecl)->origin)
 443     {
 444       /* Stop pointing to the local nodes about to be freed.
 445          But DECL_INITIAL must remain nonzero so we know this
 446          was an actual function definition.
 447          For a nested function, this is done in c_pop_function_context.
 448          If rest_of_compilation set this to 0, leave it 0.  */
 449       if (DECL_INITIAL (fndecl) != 0)
 450         DECL_INITIAL (fndecl) = error_mark_node;
 451     }
 452
 453   input_location = saved_loc;
 454
 455   ggc_collect ();
 456   timevar_pop (TV_EXPAND);
 457 }