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 "diagnostic-core.h"
  37 #include "toplev.h"
  38 #include "flags.h"
  39 #include "cgraph.h"
  40 #include "tree-inline.h"
  41 #include "tree-mudflap.h"
  42 #include "tree-pass.h"
  43 #include "ggc.h"
  44 #include "cgraph.h"
  45 #include "graph.h"
  46 #include "cfgloop.h"
  47 #include "except.h"
  48 #include "plugin.h"
  49 #include "regset.h"     /* FIXME: For reg_obstack.  */
  50
  51 /* Gate: execute, or not, all of the non-trivial optimizations.  */
  52
  53 static bool
  54 gate_all_optimizations (void)
  55 {
  56   return (optimize >= 1
  57           /* Don't bother doing anything if the program has errors.
  58              We have to pass down the queue if we already went into SSA */
  59           && (!seen_error () || gimple_in_ssa_p (cfun)));
  60 }
  61
  62 struct gimple_opt_pass pass_all_optimizations =
  63 {
  64  {
  65   GIMPLE_PASS,
  66   "*all_optimizations",                 /* name */
  67   gate_all_optimizations,               /* gate */
  68   NULL,                                 /* execute */
  69   NULL,                                 /* sub */
  70   NULL,                                 /* next */
  71   0,                                    /* static_pass_number */
  72   TV_OPTIMIZE,                          /* tv_id */
  73   0,                                    /* properties_required */
  74   0,                                    /* properties_provided */
  75   0,                                    /* properties_destroyed */
  76   0,                                    /* todo_flags_start */
  77   0                                     /* todo_flags_finish */
  78  }
  79 };
  80
  81 /* Gate: execute, or not, all of the non-trivial optimizations.  */
  82
  83 static bool
  84 gate_all_early_local_passes (void)
  85 {
  86           /* Don't bother doing anything if the program has errors.  */
  87   return (!seen_error () && !in_lto_p);
  88 }
  89
  90 static unsigned int
  91 execute_all_early_local_passes (void)
  92 {
  93   /* Once this pass (and its sub-passes) are complete, all functions
  94      will be in SSA form.  Technically this state change is happening
  95      a tad early, since the sub-passes have not yet run, but since
  96      none of the sub-passes are IPA passes and do not create new
  97      functions, this is ok.  We're setting this value for the benefit
  98      of IPA passes that follow.  */
  99   if (cgraph_state < CGRAPH_STATE_IPA_SSA)
 100     cgraph_state = CGRAPH_STATE_IPA_SSA;
 101   return 0;
 102 }
 103
 104 struct simple_ipa_opt_pass pass_early_local_passes =
 105 {
 106  {
 107   SIMPLE_IPA_PASS,
 108   "early_local_cleanups",               /* name */
 109   gate_all_early_local_passes,          /* gate */
 110   execute_all_early_local_passes,       /* execute */
 111   NULL,                                 /* sub */
 112   NULL,                                 /* next */
 113   0,                                    /* static_pass_number */
 114   TV_EARLY_LOCAL,                       /* tv_id */
 115   0,                                    /* properties_required */
 116   0,                                    /* properties_provided */
 117   0,                                    /* properties_destroyed */
 118   0,                                    /* todo_flags_start */
 119   TODO_remove_functions                 /* todo_flags_finish */
 120  }
 121 };
 122
 123 /* Gate: execute, or not, all of the non-trivial optimizations.  */
 124
 125 static bool
 126 gate_all_early_optimizations (void)
 127 {
 128   return (optimize >= 1
 129           /* Don't bother doing anything if the program has errors.  */
 130           && !seen_error ());
 131 }
 132
 133 struct gimple_opt_pass pass_all_early_optimizations =
 134 {
 135  {
 136   GIMPLE_PASS,
 137   "early_optimizations",                /* name */
 138   gate_all_early_optimizations,         /* gate */
 139   NULL,                                 /* execute */
 140   NULL,                                 /* sub */
 141   NULL,                                 /* next */
 142   0,                                    /* static_pass_number */
 143   TV_NONE,                              /* tv_id */
 144   0,                                    /* properties_required */
 145   0,                                    /* properties_provided */
 146   0,                                    /* properties_destroyed */
 147   0,                                    /* todo_flags_start */
 148   0                                     /* todo_flags_finish */
 149  }
 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_post_optimizing (void)
 160 {
 161   cleanup_tree_cfg ();
 162   cleanup_dead_labels ();
 163   group_case_labels ();
 164   if ((flag_compare_debug_opt || flag_compare_debug)
 165       && flag_dump_final_insns)
 166     {
 167       FILE *final_output = fopen (flag_dump_final_insns, "a");
 168
 169       if (!final_output)
 170         {
 171           error ("could not open final insn dump file %qs: %m",
 172                  flag_dump_final_insns);
 173           flag_dump_final_insns = NULL;
 174         }
 175       else
 176         {
 177           int save_unnumbered = flag_dump_unnumbered;
 178           int save_noaddr = flag_dump_noaddr;
 179
 180           flag_dump_noaddr = flag_dump_unnumbered = 1;
 181           fprintf (final_output, "\n");
 182           dump_enumerated_decls (final_output, dump_flags | TDF_NOUID);
 183           flag_dump_noaddr = save_noaddr;
 184           flag_dump_unnumbered = save_unnumbered;
 185           if (fclose (final_output))
 186             {
 187               error ("could not close final insn dump file %qs: %m",
 188                      flag_dump_final_insns);
 189               flag_dump_final_insns = NULL;
 190             }
 191         }
 192     }
 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_TREE_CLEANUP_CFG,                  /* 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 /* 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_get_node (current_function_decl)->count
 251                     * REG_BR_PROB_BASE + ENTRY_BLOCK_PTR->count / 2)
 252                    / ENTRY_BLOCK_PTR->count);
 253   else
 254     count_scale = REG_BR_PROB_BASE;
 255
 256   ENTRY_BLOCK_PTR->count = cgraph_get_node (current_function_decl)->count;
 257   EXIT_BLOCK_PTR->count = (EXIT_BLOCK_PTR->count * count_scale
 258                            + REG_BR_PROB_BASE / 2) / REG_BR_PROB_BASE;
 259
 260   FOR_EACH_BB (bb)
 261     {
 262       bb->count = (bb->count * count_scale
 263                    + REG_BR_PROB_BASE / 2) / REG_BR_PROB_BASE;
 264       for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
 265         {
 266           gimple stmt = gsi_stmt (gsi);
 267           tree decl = is_gimple_call (stmt)
 268                       ? gimple_call_fndecl (stmt)
 269                       : NULL;
 270           if (decl)
 271             {
 272               int flags = gimple_call_flags (stmt);
 273               if (flags & (ECF_CONST | ECF_PURE | ECF_LOOPING_CONST_OR_PURE))
 274                 {
 275                   if (gimple_purge_dead_abnormal_call_edges (bb))
 276                     todo |= TODO_cleanup_cfg;
 277
 278                   if (gimple_in_ssa_p (cfun))
 279                     {
 280                       todo |= TODO_update_ssa | TODO_cleanup_cfg;
 281                       update_stmt (stmt);
 282                     }
 283                 }
 284
 285               if (flags & ECF_NORETURN
 286                   && fixup_noreturn_call (stmt))
 287                 todo |= TODO_cleanup_cfg;
 288              }
 289
 290           if (maybe_clean_eh_stmt (stmt)
 291               && gimple_purge_dead_eh_edges (bb))
 292             todo |= TODO_cleanup_cfg;
 293         }
 294
 295       FOR_EACH_EDGE (e, ei, bb->succs)
 296         e->count = (e->count * count_scale
 297                     + REG_BR_PROB_BASE / 2) / REG_BR_PROB_BASE;
 298     }
 299   if (count_scale != REG_BR_PROB_BASE)
 300     compute_function_frequency ();
 301
 302   /* We just processed all calls.  */
 303   if (cfun->gimple_df)
 304     {
 305       VEC_free (gimple, gc, MODIFIED_NORETURN_CALLS (cfun));
 306       MODIFIED_NORETURN_CALLS (cfun) = NULL;
 307     }
 308
 309   /* Dump a textual representation of the flowgraph.  */
 310   if (dump_file)
 311     gimple_dump_cfg (dump_file, dump_flags);
 312
 313   return todo;
 314 }
 315
 316 struct gimple_opt_pass pass_fixup_cfg =
 317 {
 318  {
 319   GIMPLE_PASS,
 320   "*free_cfg_annotations",              /* name */
 321   NULL,                                 /* gate */
 322   execute_fixup_cfg,                    /* execute */
 323   NULL,                                 /* sub */
 324   NULL,                                 /* next */
 325   0,                                    /* static_pass_number */
 326   TV_NONE,                              /* tv_id */
 327   PROP_cfg,                             /* properties_required */
 328   0,                                    /* properties_provided */
 329   0,                                    /* properties_destroyed */
 330   0,                                    /* todo_flags_start */
 331   0                                     /* todo_flags_finish */
 332  }
 333 };
 334
 335 /* Do the actions required to initialize internal data structures used
 336    in tree-ssa optimization passes.  */
 337
 338 static unsigned int
 339 execute_init_datastructures (void)
 340 {
 341   /* Allocate hash tables, arrays and other structures.  */
 342   init_tree_ssa (cfun);
 343   return 0;
 344 }
 345
 346 struct gimple_opt_pass pass_init_datastructures =
 347 {
 348  {
 349   GIMPLE_PASS,
 350   "*init_datastructures",               /* name */
 351   NULL,                                 /* gate */
 352   execute_init_datastructures,          /* execute */
 353   NULL,                                 /* sub */
 354   NULL,                                 /* next */
 355   0,                                    /* static_pass_number */
 356   TV_NONE,                              /* tv_id */
 357   PROP_cfg,                             /* properties_required */
 358   0,                                    /* properties_provided */
 359   0,                                    /* properties_destroyed */
 360   0,                                    /* todo_flags_start */
 361   0                                     /* todo_flags_finish */
 362  }
 363 };
 364
 365 void
 366 tree_lowering_passes (tree fn)
 367 {
 368   tree saved_current_function_decl = current_function_decl;
 369
 370   current_function_decl = fn;
 371   push_cfun (DECL_STRUCT_FUNCTION (fn));
 372   gimple_register_cfg_hooks ();
 373   bitmap_obstack_initialize (NULL);
 374   execute_pass_list (all_lowering_passes);
 375   if (optimize && cgraph_global_info_ready)
 376     execute_pass_list (pass_early_local_passes.pass.sub);
 377   free_dominance_info (CDI_POST_DOMINATORS);
 378   free_dominance_info (CDI_DOMINATORS);
 379   compact_blocks ();
 380   current_function_decl = saved_current_function_decl;
 381   bitmap_obstack_release (NULL);
 382   pop_cfun ();
 383 }
 384 \f
 385 /* For functions-as-trees languages, this performs all optimization and
 386    compilation for FNDECL.  */
 387
 388 void
 389 tree_rest_of_compilation (tree fndecl)
 390 {
 391   location_t saved_loc;
 392
 393   timevar_push (TV_REST_OF_COMPILATION);
 394
 395   gcc_assert (cgraph_global_info_ready);
 396
 397   /* Initialize the default bitmap obstack.  */
 398   bitmap_obstack_initialize (NULL);
 399
 400   /* Initialize the RTL code for the function.  */
 401   current_function_decl = fndecl;
 402   saved_loc = input_location;
 403   input_location = DECL_SOURCE_LOCATION (fndecl);
 404   init_function_start (fndecl);
 405
 406   gimple_register_cfg_hooks ();
 407
 408   bitmap_obstack_initialize (&reg_obstack); /* FIXME, only at RTL generation*/
 409
 410   execute_all_ipa_transforms ();
 411
 412   /* Perform all tree transforms and optimizations.  */
 413
 414   /* Signal the start of passes.  */
 415   invoke_plugin_callbacks (PLUGIN_ALL_PASSES_START, NULL);
 416
 417   execute_pass_list (all_passes);
 418
 419   /* Signal the end of passes.  */
 420   invoke_plugin_callbacks (PLUGIN_ALL_PASSES_END, NULL);
 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_, "size of return value of %q+D is %u bytes",
 446                      fndecl, size_as_int);
 447           else
 448             warning (OPT_Wlarger_than_, "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_get_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_REST_OF_COMPILATION);
 470 }