gcc/tree-optimize.c

   1 /* Top-level control of tree optimizations.
   2    Copyright 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
   3    Contributed by Diego Novillo <dnovillo@redhat.com>
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 2, or (at your option)
  10 any later version.
  11
  12 GCC is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING.  If not, write to
  19 the Free Software Foundation, 51 Franklin Street, Fifth Floor,
  20 Boston, MA 02110-1301, USA.  */
  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           && !(errorcount || sorrycount));
  62 }
  63
  64 struct tree_opt_pass pass_all_optimizations =
  65 {
  66   NULL,                                 /* name */
  67   gate_all_optimizations,               /* gate */
  68   NULL,                                 /* execute */
  69   NULL,                                 /* sub */
  70   NULL,                                 /* next */
  71   0,                                    /* static_pass_number */
  72   0,                                    /* 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   0                                     /* letter */
  79 };
  80
  81 struct tree_opt_pass pass_early_local_passes =
  82 {
  83   NULL,                                 /* name */
  84   gate_all_optimizations,               /* gate */
  85   NULL,                                 /* execute */
  86   NULL,                                 /* sub */
  87   NULL,                                 /* next */
  88   0,                                    /* static_pass_number */
  89   0,                                    /* tv_id */
  90   0,                                    /* properties_required */
  91   0,                                    /* properties_provided */
  92   0,                                    /* properties_destroyed */
  93   0,                                    /* todo_flags_start */
  94   0,                                    /* todo_flags_finish */
  95   0                                     /* letter */
  96 };
  97
  98 /* Pass: cleanup the CFG just before expanding trees to RTL.
  99    This is just a round of label cleanups and case node grouping
 100    because after the tree optimizers have run such cleanups may
 101    be necessary.  */
 102
 103 static void
 104 execute_cleanup_cfg_pre_ipa (void)
 105 {
 106   cleanup_tree_cfg ();
 107 }
 108
 109 struct tree_opt_pass pass_cleanup_cfg =
 110 {
 111   "cleanup_cfg",                        /* name */
 112   NULL,                                 /* gate */
 113   execute_cleanup_cfg_pre_ipa,          /* execute */
 114   NULL,                                 /* sub */
 115   NULL,                                 /* next */
 116   0,                                    /* static_pass_number */
 117   0,                                    /* tv_id */
 118   PROP_cfg,                             /* properties_required */
 119   0,                                    /* properties_provided */
 120   0,                                    /* properties_destroyed */
 121   0,                                    /* todo_flags_start */
 122   TODO_dump_func,                                       /* todo_flags_finish */
 123   0                                     /* letter */
 124 };
 125
 126
 127 /* Pass: cleanup the CFG just before expanding trees to RTL.
 128    This is just a round of label cleanups and case node grouping
 129    because after the tree optimizers have run such cleanups may
 130    be necessary.  */
 131
 132 static void
 133 execute_cleanup_cfg_post_optimizing (void)
 134 {
 135   fold_cond_expr_cond ();
 136   cleanup_tree_cfg ();
 137   cleanup_dead_labels ();
 138   group_case_labels ();
 139 }
 140
 141 struct tree_opt_pass pass_cleanup_cfg_post_optimizing =
 142 {
 143   "final_cleanup",                      /* name */
 144   NULL,                                 /* gate */
 145   execute_cleanup_cfg_post_optimizing,  /* execute */
 146   NULL,                                 /* sub */
 147   NULL,                                 /* next */
 148   0,                                    /* static_pass_number */
 149   0,                                    /* tv_id */
 150   PROP_cfg,                             /* properties_required */
 151   0,                                    /* properties_provided */
 152   0,                                    /* properties_destroyed */
 153   0,                                    /* todo_flags_start */
 154   TODO_dump_func,                                       /* todo_flags_finish */
 155   0                                     /* letter */
 156 };
 157
 158 /* Pass: do the actions required to finish with tree-ssa optimization
 159    passes.  */
 160
 161 static void
 162 execute_free_datastructures (void)
 163 {
 164   /* ??? This isn't the right place for this.  Worse, it got computed
 165      more or less at random in various passes.  */
 166   free_dominance_info (CDI_DOMINATORS);
 167   free_dominance_info (CDI_POST_DOMINATORS);
 168
 169   /* Remove the ssa structures.  Do it here since this includes statement
 170      annotations that need to be intact during disband_implicit_edges.  */
 171   delete_tree_ssa ();
 172 }
 173
 174 struct tree_opt_pass pass_free_datastructures =
 175 {
 176   NULL,                                 /* name */
 177   NULL,                                 /* gate */
 178   execute_free_datastructures,                  /* execute */
 179   NULL,                                 /* sub */
 180   NULL,                                 /* next */
 181   0,                                    /* static_pass_number */
 182   0,                                    /* tv_id */
 183   PROP_cfg,                             /* properties_required */
 184   0,                                    /* properties_provided */
 185   0,                                    /* properties_destroyed */
 186   0,                                    /* todo_flags_start */
 187   0,                                    /* todo_flags_finish */
 188   0                                     /* letter */
 189 };
 190 /* Pass: free cfg annotations.  */
 191
 192 static void
 193 execute_free_cfg_annotations (void)
 194 {
 195   basic_block bb;
 196   block_stmt_iterator bsi;
 197
 198   /* Emit gotos for implicit jumps.  */
 199   disband_implicit_edges ();
 200
 201   /* Remove annotations from every tree in the function.  */
 202   FOR_EACH_BB (bb)
 203     for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
 204       {
 205         tree stmt = bsi_stmt (bsi);
 206         ggc_free (stmt->common.ann);
 207         stmt->common.ann = NULL;
 208       }
 209
 210   /* And get rid of annotations we no longer need.  */
 211   delete_tree_cfg_annotations ();
 212 }
 213
 214 struct tree_opt_pass pass_free_cfg_annotations =
 215 {
 216   NULL,                                 /* name */
 217   NULL,                                 /* gate */
 218   execute_free_cfg_annotations,         /* execute */
 219   NULL,                                 /* sub */
 220   NULL,                                 /* next */
 221   0,                                    /* static_pass_number */
 222   0,                                    /* tv_id */
 223   PROP_cfg,                             /* properties_required */
 224   0,                                    /* properties_provided */
 225   0,                                    /* properties_destroyed */
 226   0,                                    /* todo_flags_start */
 227   0,                                    /* todo_flags_finish */
 228   0                                     /* letter */
 229 };
 230 /* Pass: fixup_cfg - IPA passes or compilation of earlier functions might've
 231    changed some properties - such as marked functions nothrow.  Remove now
 232    redundant edges and basic blocks.  */
 233
 234 static void
 235 execute_fixup_cfg (void)
 236 {
 237   basic_block bb;
 238   block_stmt_iterator bsi;
 239
 240   if (cfun->eh)
 241     FOR_EACH_BB (bb)
 242       {
 243         for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
 244           {
 245             tree stmt = bsi_stmt (bsi);
 246             tree call = get_call_expr_in (stmt);
 247
 248             if (call && call_expr_flags (call) & (ECF_CONST | ECF_PURE))
 249               TREE_SIDE_EFFECTS (call) = 0;
 250             if (!tree_could_throw_p (stmt) && lookup_stmt_eh_region (stmt))
 251               remove_stmt_from_eh_region (stmt);
 252           }
 253         tree_purge_dead_eh_edges (bb);
 254       }
 255
 256   cleanup_tree_cfg ();
 257 }
 258
 259 struct tree_opt_pass pass_fixup_cfg =
 260 {
 261   NULL,                                 /* name */
 262   NULL,                                 /* gate */
 263   execute_fixup_cfg,                    /* execute */
 264   NULL,                                 /* sub */
 265   NULL,                                 /* next */
 266   0,                                    /* static_pass_number */
 267   0,                                    /* tv_id */
 268   PROP_cfg,                             /* properties_required */
 269   0,                                    /* properties_provided */
 270   0,                                    /* properties_destroyed */
 271   0,                                    /* todo_flags_start */
 272   0,                                    /* todo_flags_finish */
 273   0                                     /* letter */
 274 };
 275
 276 /* Do the actions required to initialize internal data structures used
 277    in tree-ssa optimization passes.  */
 278
 279 static void
 280 execute_init_datastructures (void)
 281 {
 282   /* Allocate hash tables, arrays and other structures.  */
 283   init_tree_ssa ();
 284 }
 285
 286 struct tree_opt_pass pass_init_datastructures =
 287 {
 288   NULL,                                 /* name */
 289   NULL,                                 /* gate */
 290   execute_init_datastructures,          /* execute */
 291   NULL,                                 /* sub */
 292   NULL,                                 /* next */
 293   0,                                    /* static_pass_number */
 294   0,                                    /* tv_id */
 295   PROP_cfg,                             /* properties_required */
 296   0,                                    /* properties_provided */
 297   0,                                    /* properties_destroyed */
 298   0,                                    /* todo_flags_start */
 299   0,                                    /* todo_flags_finish */
 300   0                                     /* letter */
 301 };
 302
 303 \f
 304 void
 305 tree_lowering_passes (tree fn)
 306 {
 307   tree saved_current_function_decl = current_function_decl;
 308
 309   current_function_decl = fn;
 310   push_cfun (DECL_STRUCT_FUNCTION (fn));
 311   tree_register_cfg_hooks ();
 312   bitmap_obstack_initialize (NULL);
 313   execute_pass_list (all_lowering_passes);
 314   free_dominance_info (CDI_POST_DOMINATORS);
 315   compact_blocks ();
 316   current_function_decl = saved_current_function_decl;
 317   bitmap_obstack_release (NULL);
 318   pop_cfun ();
 319 }
 320
 321 /* Update recursively all inlined_to pointers of functions
 322    inlined into NODE to INLINED_TO.  */
 323 static void
 324 update_inlined_to_pointers (struct cgraph_node *node,
 325                             struct cgraph_node *inlined_to)
 326 {
 327   struct cgraph_edge *e;
 328   for (e = node->callees; e; e = e->next_callee)
 329     {
 330       if (e->callee->global.inlined_to)
 331         {
 332           e->callee->global.inlined_to = inlined_to;
 333           update_inlined_to_pointers (e->callee, inlined_to);
 334         }
 335     }
 336 }
 337
 338 \f
 339 /* For functions-as-trees languages, this performs all optimization and
 340    compilation for FNDECL.  */
 341
 342 void
 343 tree_rest_of_compilation (tree fndecl)
 344 {
 345   location_t saved_loc;
 346   struct cgraph_node *saved_node = NULL, *node;
 347
 348   timevar_push (TV_EXPAND);
 349
 350   gcc_assert (!flag_unit_at_a_time || cgraph_global_info_ready);
 351
 352   /* Initialize the RTL code for the function.  */
 353   current_function_decl = fndecl;
 354   saved_loc = input_location;
 355   input_location = DECL_SOURCE_LOCATION (fndecl);
 356   init_function_start (fndecl);
 357
 358   /* Even though we're inside a function body, we still don't want to
 359      call expand_expr to calculate the size of a variable-sized array.
 360      We haven't necessarily assigned RTL to all variables yet, so it's
 361      not safe to try to expand expressions involving them.  */
 362   cfun->x_dont_save_pending_sizes_p = 1;
 363   cfun->after_inlining = true;
 364
 365   node = cgraph_node (fndecl);
 366
 367   /* We might need the body of this function so that we can expand
 368      it inline somewhere else.  This means not lowering some constructs
 369      such as exception handling.  */
 370   if (cgraph_preserve_function_body_p (fndecl))
 371     {
 372       if (!flag_unit_at_a_time)
 373         {
 374           struct cgraph_edge *e;
 375
 376           saved_node = cgraph_clone_node (node, node->count, 1);
 377           for (e = saved_node->callees; e; e = e->next_callee)
 378             if (!e->inline_failed)
 379               cgraph_clone_inlined_nodes (e, true);
 380         }
 381       cfun->saved_static_chain_decl = cfun->static_chain_decl;
 382       save_body (fndecl, &cfun->saved_args, &cfun->saved_static_chain_decl);
 383     }
 384
 385   if (flag_inline_trees)
 386     {
 387       struct cgraph_edge *e;
 388       for (e = node->callees; e; e = e->next_callee)
 389         if (!e->inline_failed || warn_inline)
 390           break;
 391       if (e)
 392         {
 393           timevar_push (TV_INTEGRATION);
 394           optimize_inline_calls (fndecl);
 395           timevar_pop (TV_INTEGRATION);
 396         }
 397     }
 398   /* We are not going to maintain the cgraph edges up to date.
 399      Kill it so it won't confuse us.  */
 400   while (node->callees)
 401     {
 402       /* In non-unit-at-a-time we must mark all referenced functions as needed.
 403          */
 404       if (node->callees->callee->analyzed && !flag_unit_at_a_time)
 405         cgraph_mark_needed_node (node->callees->callee);
 406       cgraph_remove_edge (node->callees);
 407     }
 408
 409   /* We are not going to maintain the cgraph edges up to date.
 410      Kill it so it won't confuse us.  */
 411   cgraph_node_remove_callees (node);
 412
 413
 414   /* Initialize the default bitmap obstack.  */
 415   bitmap_obstack_initialize (NULL);
 416   bitmap_obstack_initialize (&reg_obstack); /* FIXME, only at RTL generation*/
 417
 418   tree_register_cfg_hooks ();
 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   /* Restore original body if still needed.  */
 428   if (cfun->saved_cfg)
 429     {
 430       DECL_ARGUMENTS (fndecl) = cfun->saved_args;
 431       cfun->cfg = cfun->saved_cfg;
 432       cfun->eh = cfun->saved_eh;
 433       DECL_INITIAL (fndecl) = cfun->saved_blocks;
 434       cfun->unexpanded_var_list = cfun->saved_unexpanded_var_list;
 435       cfun->saved_cfg = NULL;
 436       cfun->saved_eh = NULL;
 437       cfun->saved_args = NULL_TREE;
 438       cfun->saved_blocks = NULL_TREE;
 439       cfun->saved_unexpanded_var_list = NULL_TREE;
 440       cfun->static_chain_decl = cfun->saved_static_chain_decl;
 441       cfun->saved_static_chain_decl = NULL;
 442       /* When not in unit-at-a-time mode, we must preserve out of line copy
 443          representing node before inlining.  Restore original outgoing edges
 444          using clone we created earlier.  */
 445       if (!flag_unit_at_a_time)
 446         {
 447           struct cgraph_edge *e;
 448
 449           node = cgraph_node (current_function_decl);
 450           cgraph_node_remove_callees (node);
 451           node->callees = saved_node->callees;
 452           saved_node->callees = NULL;
 453           update_inlined_to_pointers (node, node);
 454           for (e = node->callees; e; e = e->next_callee)
 455             e->caller = node;
 456           cgraph_remove_node (saved_node);
 457         }
 458     }
 459   else
 460     DECL_SAVED_TREE (fndecl) = NULL;
 461   cfun = 0;
 462
 463   /* If requested, warn about function definitions where the function will
 464      return a value (usually of some struct or union type) which itself will
 465      take up a lot of stack space.  */
 466   if (warn_larger_than && !DECL_EXTERNAL (fndecl) && TREE_TYPE (fndecl))
 467     {
 468       tree ret_type = TREE_TYPE (TREE_TYPE (fndecl));
 469
 470       if (ret_type && TYPE_SIZE_UNIT (ret_type)
 471           && TREE_CODE (TYPE_SIZE_UNIT (ret_type)) == INTEGER_CST
 472           && 0 < compare_tree_int (TYPE_SIZE_UNIT (ret_type),
 473                                    larger_than_size))
 474         {
 475           unsigned int size_as_int
 476             = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (ret_type));
 477
 478           if (compare_tree_int (TYPE_SIZE_UNIT (ret_type), size_as_int) == 0)
 479             warning (0, "size of return value of %q+D is %u bytes",
 480                      fndecl, size_as_int);
 481           else
 482             warning (0, "size of return value of %q+D is larger than %wd bytes",
 483                      fndecl, larger_than_size);
 484         }
 485     }
 486
 487   if (!flag_inline_trees)
 488     {
 489       DECL_SAVED_TREE (fndecl) = NULL;
 490       if (DECL_STRUCT_FUNCTION (fndecl) == 0
 491           && !cgraph_node (fndecl)->origin)
 492         {
 493           /* Stop pointing to the local nodes about to be freed.
 494              But DECL_INITIAL must remain nonzero so we know this
 495              was an actual function definition.
 496              For a nested function, this is done in c_pop_function_context.
 497              If rest_of_compilation set this to 0, leave it 0.  */
 498           if (DECL_INITIAL (fndecl) != 0)
 499             DECL_INITIAL (fndecl) = error_mark_node;
 500         }
 501     }
 502
 503   input_location = saved_loc;
 504
 505   ggc_collect ();
 506   timevar_pop (TV_EXPAND);
 507 }