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);
  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
 249   if (cfun->eh)
 250     FOR_EACH_BB (bb)
 251       {
 252         for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
 253           {
 254             gimple stmt = gsi_stmt (gsi);
 255             tree decl = is_gimple_call (stmt)
 256                         ? gimple_call_fndecl (stmt)
 257                         : NULL;
 258
 259             if (decl
 260                 && gimple_call_flags (stmt) & (ECF_CONST
 261                                                | ECF_PURE
 262                                                | ECF_LOOPING_CONST_OR_PURE))
 263               {
 264                 if (gimple_in_ssa_p (cfun))
 265                   {
 266                     todo |= TODO_update_ssa | TODO_cleanup_cfg;
 267                     mark_symbols_for_renaming (stmt);
 268                     update_stmt (stmt);
 269                   }
 270               }
 271
 272             if (!stmt_could_throw_p (stmt) && lookup_stmt_eh_region (stmt))
 273               remove_stmt_from_eh_region (stmt);
 274           }
 275
 276         if (gimple_purge_dead_eh_edges (bb))
 277           todo |= TODO_cleanup_cfg;
 278       }
 279
 280   /* Dump a textual representation of the flowgraph.  */
 281   if (dump_file)
 282     gimple_dump_cfg (dump_file, dump_flags);
 283
 284   return todo;
 285 }
 286
 287 struct gimple_opt_pass pass_fixup_cfg =
 288 {
 289  {
 290   GIMPLE_PASS,
 291   NULL,                                 /* name */
 292   NULL,                                 /* gate */
 293   execute_fixup_cfg,            /* execute */
 294   NULL,                                 /* sub */
 295   NULL,                                 /* next */
 296   0,                                    /* static_pass_number */
 297   TV_NONE,                              /* tv_id */
 298   PROP_cfg,                             /* properties_required */
 299   0,                                    /* properties_provided */
 300   0,                                    /* properties_destroyed */
 301   0,                                    /* todo_flags_start */
 302   0                                     /* todo_flags_finish */
 303  }
 304 };
 305
 306 /* Do the actions required to initialize internal data structures used
 307    in tree-ssa optimization passes.  */
 308
 309 static unsigned int
 310 execute_init_datastructures (void)
 311 {
 312   /* Allocate hash tables, arrays and other structures.  */
 313   init_tree_ssa (cfun);
 314   return 0;
 315 }
 316
 317 struct gimple_opt_pass pass_init_datastructures =
 318 {
 319  {
 320   GIMPLE_PASS,
 321   NULL,                                 /* name */
 322   NULL,                                 /* gate */
 323   execute_init_datastructures,          /* execute */
 324   NULL,                                 /* sub */
 325   NULL,                                 /* next */
 326   0,                                    /* static_pass_number */
 327   TV_NONE,                              /* tv_id */
 328   PROP_cfg,                             /* properties_required */
 329   0,                                    /* properties_provided */
 330   0,                                    /* properties_destroyed */
 331   0,                                    /* todo_flags_start */
 332   0                                     /* todo_flags_finish */
 333  }
 334 };
 335
 336 void
 337 tree_lowering_passes (tree fn)
 338 {
 339   tree saved_current_function_decl = current_function_decl;
 340
 341   current_function_decl = fn;
 342   push_cfun (DECL_STRUCT_FUNCTION (fn));
 343   gimple_register_cfg_hooks ();
 344   bitmap_obstack_initialize (NULL);
 345   execute_pass_list (all_lowering_passes);
 346   if (optimize && cgraph_global_info_ready)
 347     execute_pass_list (pass_early_local_passes.pass.sub);
 348   free_dominance_info (CDI_POST_DOMINATORS);
 349   free_dominance_info (CDI_DOMINATORS);
 350   compact_blocks ();
 351   current_function_decl = saved_current_function_decl;
 352   bitmap_obstack_release (NULL);
 353   pop_cfun ();
 354 }
 355 \f
 356 /* For functions-as-trees languages, this performs all optimization and
 357    compilation for FNDECL.  */
 358
 359 void
 360 tree_rest_of_compilation (tree fndecl)
 361 {
 362   location_t saved_loc;
 363   struct cgraph_node *node;
 364
 365   timevar_push (TV_EXPAND);
 366
 367   gcc_assert (cgraph_global_info_ready);
 368
 369   node = cgraph_node (fndecl);
 370
 371   /* Initialize the default bitmap obstack.  */
 372   bitmap_obstack_initialize (NULL);
 373
 374   /* Initialize the RTL code for the function.  */
 375   current_function_decl = fndecl;
 376   saved_loc = input_location;
 377   input_location = DECL_SOURCE_LOCATION (fndecl);
 378   init_function_start (fndecl);
 379
 380   /* Even though we're inside a function body, we still don't want to
 381      call expand_expr to calculate the size of a variable-sized array.
 382      We haven't necessarily assigned RTL to all variables yet, so it's
 383      not safe to try to expand expressions involving them.  */
 384   cfun->dont_save_pending_sizes_p = 1;
 385
 386   gimple_register_cfg_hooks ();
 387
 388   bitmap_obstack_initialize (&reg_obstack); /* FIXME, only at RTL generation*/
 389   /* Perform all tree transforms and optimizations.  */
 390   execute_pass_list (all_passes);
 391
 392   bitmap_obstack_release (&reg_obstack);
 393
 394   /* Release the default bitmap obstack.  */
 395   bitmap_obstack_release (NULL);
 396
 397   set_cfun (NULL);
 398
 399   /* If requested, warn about function definitions where the function will
 400      return a value (usually of some struct or union type) which itself will
 401      take up a lot of stack space.  */
 402   if (warn_larger_than && !DECL_EXTERNAL (fndecl) && TREE_TYPE (fndecl))
 403     {
 404       tree ret_type = TREE_TYPE (TREE_TYPE (fndecl));
 405
 406       if (ret_type && TYPE_SIZE_UNIT (ret_type)
 407           && TREE_CODE (TYPE_SIZE_UNIT (ret_type)) == INTEGER_CST
 408           && 0 < compare_tree_int (TYPE_SIZE_UNIT (ret_type),
 409                                    larger_than_size))
 410         {
 411           unsigned int size_as_int
 412             = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (ret_type));
 413
 414           if (compare_tree_int (TYPE_SIZE_UNIT (ret_type), size_as_int) == 0)
 415             warning (OPT_Wlarger_than_eq, "size of return value of %q+D is %u bytes",
 416                      fndecl, size_as_int);
 417           else
 418             warning (OPT_Wlarger_than_eq, "size of return value of %q+D is larger than %wd bytes",
 419                      fndecl, larger_than_size);
 420         }
 421     }
 422
 423   gimple_set_body (fndecl, NULL);
 424   if (DECL_STRUCT_FUNCTION (fndecl) == 0
 425       && !cgraph_node (fndecl)->origin)
 426     {
 427       /* Stop pointing to the local nodes about to be freed.
 428          But DECL_INITIAL must remain nonzero so we know this
 429          was an actual function definition.
 430          For a nested function, this is done in c_pop_function_context.
 431          If rest_of_compilation set this to 0, leave it 0.  */
 432       if (DECL_INITIAL (fndecl) != 0)
 433         DECL_INITIAL (fndecl) = error_mark_node;
 434     }
 435
 436   input_location = saved_loc;
 437
 438   ggc_collect ();
 439   timevar_pop (TV_EXPAND);
 440 }