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   cleanup_tree_cfg ();
 136   cleanup_dead_labels ();
 137   group_case_labels ();
 138 }
 139
 140 struct tree_opt_pass pass_cleanup_cfg_post_optimizing =
 141 {
 142   "final_cleanup",                      /* name */
 143   NULL,                                 /* gate */
 144   execute_cleanup_cfg_post_optimizing,  /* execute */
 145   NULL,                                 /* sub */
 146   NULL,                                 /* next */
 147   0,                                    /* static_pass_number */
 148   0,                                    /* tv_id */
 149   PROP_cfg,                             /* properties_required */
 150   0,                                    /* properties_provided */
 151   0,                                    /* properties_destroyed */
 152   0,                                    /* todo_flags_start */
 153   TODO_dump_func,                                       /* todo_flags_finish */
 154   0                                     /* letter */
 155 };
 156
 157 /* Pass: do the actions required to finish with tree-ssa optimization
 158    passes.  */
 159
 160 static void
 161 execute_free_datastructures (void)
 162 {
 163   /* ??? This isn't the right place for this.  Worse, it got computed
 164      more or less at random in various passes.  */
 165   free_dominance_info (CDI_DOMINATORS);
 166   free_dominance_info (CDI_POST_DOMINATORS);
 167
 168   /* Remove the ssa structures.  Do it here since this includes statement
 169      annotations that need to be intact during disband_implicit_edges.  */
 170   delete_tree_ssa ();
 171 }
 172
 173 struct tree_opt_pass pass_free_datastructures =
 174 {
 175   NULL,                                 /* name */
 176   NULL,                                 /* gate */
 177   execute_free_datastructures,                  /* execute */
 178   NULL,                                 /* sub */
 179   NULL,                                 /* next */
 180   0,                                    /* static_pass_number */
 181   0,                                    /* tv_id */
 182   PROP_cfg,                             /* properties_required */
 183   0,                                    /* properties_provided */
 184   0,                                    /* properties_destroyed */
 185   0,                                    /* todo_flags_start */
 186   0,                                    /* todo_flags_finish */
 187   0                                     /* letter */
 188 };
 189 /* Pass: free cfg annotations.  */
 190
 191 static void
 192 execute_free_cfg_annotations (void)
 193 {
 194   basic_block bb;
 195   block_stmt_iterator bsi;
 196
 197   /* Emit gotos for implicit jumps.  */
 198   disband_implicit_edges ();
 199
 200   /* Remove annotations from every tree in the function.  */
 201   FOR_EACH_BB (bb)
 202     for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
 203       {
 204         tree stmt = bsi_stmt (bsi);
 205         ggc_free (stmt->common.ann);
 206         stmt->common.ann = NULL;
 207       }
 208
 209   /* And get rid of annotations we no longer need.  */
 210   delete_tree_cfg_annotations ();
 211 }
 212
 213 struct tree_opt_pass pass_free_cfg_annotations =
 214 {
 215   NULL,                                 /* name */
 216   NULL,                                 /* gate */
 217   execute_free_cfg_annotations,         /* execute */
 218   NULL,                                 /* sub */
 219   NULL,                                 /* next */
 220   0,                                    /* static_pass_number */
 221   0,                                    /* tv_id */
 222   PROP_cfg,                             /* properties_required */
 223   0,                                    /* properties_provided */
 224   0,                                    /* properties_destroyed */
 225   0,                                    /* todo_flags_start */
 226   0,                                    /* todo_flags_finish */
 227   0                                     /* letter */
 228 };
 229 /* Pass: fixup_cfg - IPA passes or compilation of earlier functions might've
 230    changed some properties - such as marked functions nothrow.  Remove now
 231    redundant edges and basic blocks.  */
 232
 233 static void
 234 execute_fixup_cfg (void)
 235 {
 236   basic_block bb;
 237   block_stmt_iterator bsi;
 238
 239   if (cfun->eh)
 240     FOR_EACH_BB (bb)
 241       {
 242         for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
 243           {
 244             tree stmt = bsi_stmt (bsi);
 245             tree call = get_call_expr_in (stmt);
 246
 247             if (call && call_expr_flags (call) & (ECF_CONST | ECF_PURE))
 248               TREE_SIDE_EFFECTS (call) = 0;
 249             if (!tree_could_throw_p (stmt) && lookup_stmt_eh_region (stmt))
 250               remove_stmt_from_eh_region (stmt);
 251           }
 252         tree_purge_dead_eh_edges (bb);
 253       }
 254
 255   cleanup_tree_cfg ();
 256 }
 257
 258 struct tree_opt_pass pass_fixup_cfg =
 259 {
 260   NULL,                                 /* name */
 261   NULL,                                 /* gate */
 262   execute_fixup_cfg,                    /* execute */
 263   NULL,                                 /* sub */
 264   NULL,                                 /* next */
 265   0,                                    /* static_pass_number */
 266   0,                                    /* tv_id */
 267   PROP_cfg,                             /* properties_required */
 268   0,                                    /* properties_provided */
 269   0,                                    /* properties_destroyed */
 270   0,                                    /* todo_flags_start */
 271   0,                                    /* todo_flags_finish */
 272   0                                     /* letter */
 273 };
 274
 275 /* Do the actions required to initialize internal data structures used
 276    in tree-ssa optimization passes.  */
 277
 278 static void
 279 execute_init_datastructures (void)
 280 {
 281   /* Allocate hash tables, arrays and other structures.  */
 282   init_tree_ssa ();
 283 }
 284
 285 struct tree_opt_pass pass_init_datastructures =
 286 {
 287   NULL,                                 /* name */
 288   NULL,                                 /* gate */
 289   execute_init_datastructures,          /* execute */
 290   NULL,                                 /* sub */
 291   NULL,                                 /* next */
 292   0,                                    /* static_pass_number */
 293   0,                                    /* tv_id */
 294   PROP_cfg,                             /* properties_required */
 295   0,                                    /* properties_provided */
 296   0,                                    /* properties_destroyed */
 297   0,                                    /* todo_flags_start */
 298   0,                                    /* todo_flags_finish */
 299   0                                     /* letter */
 300 };
 301
 302 \f
 303 void
 304 tree_lowering_passes (tree fn)
 305 {
 306   tree saved_current_function_decl = current_function_decl;
 307
 308   current_function_decl = fn;
 309   push_cfun (DECL_STRUCT_FUNCTION (fn));
 310   tree_register_cfg_hooks ();
 311   bitmap_obstack_initialize (NULL);
 312   execute_pass_list (all_lowering_passes);
 313   free_dominance_info (CDI_POST_DOMINATORS);
 314   compact_blocks ();
 315   current_function_decl = saved_current_function_decl;
 316   bitmap_obstack_release (NULL);
 317   pop_cfun ();
 318 }
 319
 320 /* Update recursively all inlined_to pointers of functions
 321    inlined into NODE to INLINED_TO.  */
 322 static void
 323 update_inlined_to_pointers (struct cgraph_node *node,
 324                             struct cgraph_node *inlined_to)
 325 {
 326   struct cgraph_edge *e;
 327   for (e = node->callees; e; e = e->next_callee)
 328     {
 329       if (e->callee->global.inlined_to)
 330         {
 331           e->callee->global.inlined_to = inlined_to;
 332           update_inlined_to_pointers (e->callee, inlined_to);
 333         }
 334     }
 335 }
 336
 337 \f
 338 /* For functions-as-trees languages, this performs all optimization and
 339    compilation for FNDECL.  */
 340
 341 void
 342 tree_rest_of_compilation (tree fndecl)
 343 {
 344   location_t saved_loc;
 345   struct cgraph_node *saved_node = NULL, *node;
 346
 347   timevar_push (TV_EXPAND);
 348
 349   gcc_assert (!flag_unit_at_a_time || cgraph_global_info_ready);
 350
 351   /* Initialize the RTL code for the function.  */
 352   current_function_decl = fndecl;
 353   saved_loc = input_location;
 354   input_location = DECL_SOURCE_LOCATION (fndecl);
 355   init_function_start (fndecl);
 356
 357   /* Even though we're inside a function body, we still don't want to
 358      call expand_expr to calculate the size of a variable-sized array.
 359      We haven't necessarily assigned RTL to all variables yet, so it's
 360      not safe to try to expand expressions involving them.  */
 361   cfun->x_dont_save_pending_sizes_p = 1;
 362   cfun->after_inlining = true;
 363
 364   node = cgraph_node (fndecl);
 365
 366   /* We might need the body of this function so that we can expand
 367      it inline somewhere else.  This means not lowering some constructs
 368      such as exception handling.  */
 369   if (cgraph_preserve_function_body_p (fndecl))
 370     {
 371       if (!flag_unit_at_a_time)
 372         {
 373           struct cgraph_edge *e;
 374
 375           saved_node = cgraph_clone_node (node, node->count, 1);
 376           for (e = saved_node->callees; e; e = e->next_callee)
 377             if (!e->inline_failed)
 378               cgraph_clone_inlined_nodes (e, true);
 379         }
 380       cfun->saved_static_chain_decl = cfun->static_chain_decl;
 381       save_body (fndecl, &cfun->saved_args, &cfun->saved_static_chain_decl);
 382     }
 383
 384   if (flag_inline_trees)
 385     {
 386       struct cgraph_edge *e;
 387       for (e = node->callees; e; e = e->next_callee)
 388         if (!e->inline_failed || warn_inline)
 389           break;
 390       if (e)
 391         {
 392           timevar_push (TV_INTEGRATION);
 393           optimize_inline_calls (fndecl);
 394           timevar_pop (TV_INTEGRATION);
 395         }
 396     }
 397   /* We are not going to maintain the cgraph edges up to date.
 398      Kill it so it won't confuse us.  */
 399   while (node->callees)
 400     {
 401       /* In non-unit-at-a-time we must mark all referenced functions as needed.
 402          */
 403       if (node->callees->callee->analyzed && !flag_unit_at_a_time)
 404         cgraph_mark_needed_node (node->callees->callee);
 405       cgraph_remove_edge (node->callees);
 406     }
 407
 408   /* We are not going to maintain the cgraph edges up to date.
 409      Kill it so it won't confuse us.  */
 410   cgraph_node_remove_callees (node);
 411
 412
 413   /* Initialize the default bitmap obstack.  */
 414   bitmap_obstack_initialize (NULL);
 415   bitmap_obstack_initialize (&reg_obstack); /* FIXME, only at RTL generation*/
 416
 417   tree_register_cfg_hooks ();
 418   /* Perform all tree transforms and optimizations.  */
 419   execute_pass_list (all_passes);
 420
 421   bitmap_obstack_release (&reg_obstack);
 422
 423   /* Release the default bitmap obstack.  */
 424   bitmap_obstack_release (NULL);
 425
 426   /* Restore original body if still needed.  */
 427   if (cfun->saved_cfg)
 428     {
 429       DECL_ARGUMENTS (fndecl) = cfun->saved_args;
 430       cfun->cfg = cfun->saved_cfg;
 431       cfun->eh = cfun->saved_eh;
 432       DECL_INITIAL (fndecl) = cfun->saved_blocks;
 433       cfun->unexpanded_var_list = cfun->saved_unexpanded_var_list;
 434       cfun->saved_cfg = NULL;
 435       cfun->saved_eh = NULL;
 436       cfun->saved_args = NULL_TREE;
 437       cfun->saved_blocks = NULL_TREE;
 438       cfun->saved_unexpanded_var_list = NULL_TREE;
 439       cfun->static_chain_decl = cfun->saved_static_chain_decl;
 440       cfun->saved_static_chain_decl = NULL;
 441       /* When not in unit-at-a-time mode, we must preserve out of line copy
 442          representing node before inlining.  Restore original outgoing edges
 443          using clone we created earlier.  */
 444       if (!flag_unit_at_a_time)
 445         {
 446           struct cgraph_edge *e;
 447
 448           node = cgraph_node (current_function_decl);
 449           cgraph_node_remove_callees (node);
 450           node->callees = saved_node->callees;
 451           saved_node->callees = NULL;
 452           update_inlined_to_pointers (node, node);
 453           for (e = node->callees; e; e = e->next_callee)
 454             e->caller = node;
 455           cgraph_remove_node (saved_node);
 456         }
 457     }
 458   else
 459     DECL_SAVED_TREE (fndecl) = NULL;
 460   cfun = 0;
 461
 462   /* If requested, warn about function definitions where the function will
 463      return a value (usually of some struct or union type) which itself will
 464      take up a lot of stack space.  */
 465   if (warn_larger_than && !DECL_EXTERNAL (fndecl) && TREE_TYPE (fndecl))
 466     {
 467       tree ret_type = TREE_TYPE (TREE_TYPE (fndecl));
 468
 469       if (ret_type && TYPE_SIZE_UNIT (ret_type)
 470           && TREE_CODE (TYPE_SIZE_UNIT (ret_type)) == INTEGER_CST
 471           && 0 < compare_tree_int (TYPE_SIZE_UNIT (ret_type),
 472                                    larger_than_size))
 473         {
 474           unsigned int size_as_int
 475             = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (ret_type));
 476
 477           if (compare_tree_int (TYPE_SIZE_UNIT (ret_type), size_as_int) == 0)
 478             warning (0, "size of return value of %q+D is %u bytes",
 479                      fndecl, size_as_int);
 480           else
 481             warning (0, "size of return value of %q+D is larger than %wd bytes",
 482                      fndecl, larger_than_size);
 483         }
 484     }
 485
 486   if (!flag_inline_trees)
 487     {
 488       DECL_SAVED_TREE (fndecl) = NULL;
 489       if (DECL_STRUCT_FUNCTION (fndecl) == 0
 490           && !cgraph_node (fndecl)->origin)
 491         {
 492           /* Stop pointing to the local nodes about to be freed.
 493              But DECL_INITIAL must remain nonzero so we know this
 494              was an actual function definition.
 495              For a nested function, this is done in c_pop_function_context.
 496              If rest_of_compilation set this to 0, leave it 0.  */
 497           if (DECL_INITIAL (fndecl) != 0)
 498             DECL_INITIAL (fndecl) = error_mark_node;
 499         }
 500     }
 501
 502   input_location = saved_loc;
 503
 504   ggc_collect ();
 505   timevar_pop (TV_EXPAND);
 506 }