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              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 tree_opt_pass pass_all_optimizations =
  66 {
  67   NULL,                                 /* name */
  68   gate_all_optimizations,               /* gate */
  69   NULL,                                 /* execute */
  70   NULL,                                 /* sub */
  71   NULL,                                 /* next */
  72   0,                                    /* static_pass_number */
  73   0,                                    /* tv_id */
  74   0,                                    /* properties_required */
  75   0,                                    /* properties_provided */
  76   0,                                    /* properties_destroyed */
  77   0,                                    /* todo_flags_start */
  78   0,                                    /* todo_flags_finish */
  79   0                                     /* letter */
  80 };
  81
  82 /* Gate: execute, or not, all of the non-trivial optimizations.  */
  83
  84 static bool
  85 gate_all_early_local_passes (void)
  86 {
  87           /* Don't bother doing anything if the program has errors.  */
  88   return (!errorcount && !sorrycount);
  89 }
  90
  91 struct tree_opt_pass pass_early_local_passes =
  92 {
  93   "early_local_cleanups",               /* name */
  94   gate_all_early_local_passes,          /* gate */
  95   NULL,                                 /* execute */
  96   NULL,                                 /* sub */
  97   NULL,                                 /* next */
  98   0,                                    /* static_pass_number */
  99   0,                                    /* tv_id */
 100   0,                                    /* properties_required */
 101   0,                                    /* properties_provided */
 102   0,                                    /* properties_destroyed */
 103   0,                                    /* todo_flags_start */
 104   TODO_remove_functions,                /* todo_flags_finish */
 105   0                                     /* letter */
 106 };
 107
 108 static unsigned int
 109 execute_early_local_optimizations (void)
 110 {
 111   if (flag_unit_at_a_time)
 112     cgraph_state = CGRAPH_STATE_IPA_SSA;
 113   return 0;
 114 }
 115
 116 /* Gate: execute, or not, all of the non-trivial optimizations.  */
 117
 118 static bool
 119 gate_all_early_optimizations (void)
 120 {
 121   return (optimize >= 1
 122           /* Don't bother doing anything if the program has errors.  */
 123           && !(errorcount || sorrycount));
 124 }
 125
 126 struct tree_opt_pass pass_all_early_optimizations =
 127 {
 128   "early_optimizations",                /* name */
 129   gate_all_early_optimizations,         /* gate */
 130   execute_early_local_optimizations,    /* execute */
 131   NULL,                                 /* sub */
 132   NULL,                                 /* next */
 133   0,                                    /* static_pass_number */
 134   0,                                    /* tv_id */
 135   0,                                    /* properties_required */
 136   0,                                    /* properties_provided */
 137   0,                                    /* properties_destroyed */
 138   0,                                    /* todo_flags_start */
 139   0,                                    /* todo_flags_finish */
 140   0                                     /* letter */
 141 };
 142
 143 /* Pass: cleanup the CFG just before expanding trees to RTL.
 144    This is just a round of label cleanups and case node grouping
 145    because after the tree optimizers have run such cleanups may
 146    be necessary.  */
 147
 148 static unsigned int
 149 execute_cleanup_cfg_pre_ipa (void)
 150 {
 151   cleanup_tree_cfg ();
 152   return 0;
 153 }
 154
 155 struct tree_opt_pass pass_cleanup_cfg =
 156 {
 157   "cleanup_cfg",                        /* name */
 158   NULL,                                 /* gate */
 159   execute_cleanup_cfg_pre_ipa,          /* execute */
 160   NULL,                                 /* sub */
 161   NULL,                                 /* next */
 162   0,                                    /* static_pass_number */
 163   0,                                    /* tv_id */
 164   PROP_cfg,                             /* properties_required */
 165   0,                                    /* properties_provided */
 166   0,                                    /* properties_destroyed */
 167   0,                                    /* todo_flags_start */
 168   TODO_dump_func,                                       /* todo_flags_finish */
 169   0                                     /* letter */
 170 };
 171
 172
 173 /* Pass: cleanup the CFG just before expanding trees to RTL.
 174    This is just a round of label cleanups and case node grouping
 175    because after the tree optimizers have run such cleanups may
 176    be necessary.  */
 177
 178 static unsigned int
 179 execute_cleanup_cfg_post_optimizing (void)
 180 {
 181   fold_cond_expr_cond ();
 182   cleanup_tree_cfg ();
 183   cleanup_dead_labels ();
 184   group_case_labels ();
 185   return 0;
 186 }
 187
 188 struct tree_opt_pass pass_cleanup_cfg_post_optimizing =
 189 {
 190   "final_cleanup",                      /* name */
 191   NULL,                                 /* gate */
 192   execute_cleanup_cfg_post_optimizing,  /* execute */
 193   NULL,                                 /* sub */
 194   NULL,                                 /* next */
 195   0,                                    /* static_pass_number */
 196   0,                                    /* tv_id */
 197   PROP_cfg,                             /* properties_required */
 198   0,                                    /* properties_provided */
 199   0,                                    /* properties_destroyed */
 200   0,                                    /* todo_flags_start */
 201   TODO_dump_func,                                       /* todo_flags_finish */
 202   0                                     /* letter */
 203 };
 204
 205 /* Pass: do the actions required to finish with tree-ssa optimization
 206    passes.  */
 207
 208 static unsigned int
 209 execute_free_datastructures (void)
 210 {
 211   /* ??? This isn't the right place for this.  Worse, it got computed
 212      more or less at random in various passes.  */
 213   free_dominance_info (CDI_DOMINATORS);
 214   free_dominance_info (CDI_POST_DOMINATORS);
 215
 216   /* Remove the ssa structures.  Do it here since this includes statement
 217      annotations that need to be intact during disband_implicit_edges.  */
 218   if (cfun->gimple_df)
 219     delete_tree_ssa ();
 220   return 0;
 221 }
 222
 223 struct tree_opt_pass pass_free_datastructures =
 224 {
 225   NULL,                                 /* name */
 226   NULL,                                 /* gate */
 227   execute_free_datastructures,                  /* execute */
 228   NULL,                                 /* sub */
 229   NULL,                                 /* next */
 230   0,                                    /* static_pass_number */
 231   0,                                    /* tv_id */
 232   PROP_cfg,                             /* properties_required */
 233   0,                                    /* properties_provided */
 234   0,                                    /* properties_destroyed */
 235   0,                                    /* todo_flags_start */
 236   0,                                    /* todo_flags_finish */
 237   0                                     /* letter */
 238 };
 239 /* Pass: free cfg annotations.  */
 240
 241 static unsigned int
 242 execute_free_cfg_annotations (void)
 243 {
 244   /* Emit gotos for implicit jumps.  */
 245   disband_implicit_edges ();
 246
 247   /* And get rid of annotations we no longer need.  */
 248   delete_tree_cfg_annotations ();
 249
 250 #ifdef ENABLE_CHECKING
 251   /* Once the statement annotations have been removed, we can verify
 252      the integrity of statements in the EH throw table.  */
 253   verify_eh_throw_table_statements ();
 254 #endif
 255   return 0;
 256 }
 257
 258 struct tree_opt_pass pass_free_cfg_annotations =
 259 {
 260   NULL,                                 /* name */
 261   NULL,                                 /* gate */
 262   execute_free_cfg_annotations,         /* 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 /* Return true if BB has at least one abnormal outgoing edge.  */
 276
 277 static inline bool
 278 has_abnormal_outgoing_edge_p (basic_block bb)
 279 {
 280   edge e;
 281   edge_iterator ei;
 282
 283   FOR_EACH_EDGE (e, ei, bb->succs)
 284     if (e->flags & EDGE_ABNORMAL)
 285       return true;
 286
 287   return false;
 288 }
 289
 290 /* Pass: fixup_cfg.  IPA passes, compilation of earlier functions or inlining
 291    might have changed some properties, such as marked functions nothrow or
 292    added calls that can potentially go to non-local labels.  Remove redundant
 293    edges and basic blocks, and create new ones if necessary.  */
 294
 295 static unsigned int
 296 execute_fixup_cfg (void)
 297 {
 298   basic_block bb;
 299   block_stmt_iterator bsi;
 300   int todo = gimple_in_ssa_p (cfun) ? TODO_verify_ssa : 0;
 301
 302   cfun->after_inlining = true;
 303
 304   if (cfun->eh)
 305     FOR_EACH_BB (bb)
 306       {
 307         for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
 308           {
 309             tree stmt = bsi_stmt (bsi);
 310             tree call = get_call_expr_in (stmt);
 311             tree decl = call ? get_callee_fndecl (call) : NULL;
 312
 313             if (decl && call_expr_flags (call) & (ECF_CONST | ECF_PURE)
 314                 && TREE_SIDE_EFFECTS (call))
 315               {
 316                 if (gimple_in_ssa_p (cfun))
 317                   {
 318                     todo |= TODO_update_ssa;
 319                     update_stmt (stmt);
 320                   }
 321                 TREE_SIDE_EFFECTS (call) = 0;
 322               }
 323             if (decl && TREE_NOTHROW (decl))
 324               TREE_NOTHROW (call) = 1;
 325             if (!tree_could_throw_p (stmt) && lookup_stmt_eh_region (stmt))
 326               remove_stmt_from_eh_region (stmt);
 327           }
 328         tree_purge_dead_eh_edges (bb);
 329       }
 330
 331   if (current_function_has_nonlocal_label)
 332     {
 333       FOR_EACH_BB (bb)
 334         {
 335           for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
 336             {
 337               tree stmt = bsi_stmt (bsi);
 338               if (tree_can_make_abnormal_goto (stmt))
 339                 {
 340                   if (stmt == bsi_stmt (bsi_last (bb)))
 341                     {
 342                       if (!has_abnormal_outgoing_edge_p (bb))
 343                         make_abnormal_goto_edges (bb, true);
 344                     }
 345                   else
 346                     {
 347                       edge e = split_block (bb, stmt);
 348                       bb = e->src;
 349                       make_abnormal_goto_edges (bb, true);
 350                     }
 351                   break;
 352                 }
 353
 354               /* Update PHIs on nonlocal goto receivers we (possibly)
 355                  just created new edges into.  */
 356               if (TREE_CODE (stmt) == LABEL_EXPR
 357                   && gimple_in_ssa_p (cfun))
 358                 {
 359                   tree target = LABEL_EXPR_LABEL (stmt);
 360                   if (DECL_NONLOCAL (target))
 361                     {
 362                       tree phi;
 363
 364                       for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
 365                         {
 366                           todo |= TODO_update_ssa;
 367                           gcc_assert (SSA_NAME_OCCURS_IN_ABNORMAL_PHI
 368                                       (PHI_RESULT (phi)));
 369                           mark_sym_for_renaming
 370                             (SSA_NAME_VAR (PHI_RESULT (phi)));
 371                         }
 372                     }
 373                 }
 374             }
 375         }
 376     }
 377
 378   /* Dump a textual representation of the flowgraph.  */
 379   if (dump_file)
 380     dump_tree_cfg (dump_file, dump_flags);
 381
 382   return todo;
 383 }
 384
 385 struct tree_opt_pass pass_fixup_cfg =
 386 {
 387   "fixupcfg",                           /* name */
 388   NULL,                                 /* gate */
 389   execute_fixup_cfg,                    /* execute */
 390   NULL,                                 /* sub */
 391   NULL,                                 /* next */
 392   0,                                    /* static_pass_number */
 393   0,                                    /* tv_id */
 394   PROP_cfg,                             /* properties_required */
 395   0,                                    /* properties_provided */
 396   0,                                    /* properties_destroyed */
 397   0,                                    /* todo_flags_start */
 398   TODO_cleanup_cfg | TODO_ggc_collect
 399   | TODO_dump_func | TODO_verify_flow
 400   | TODO_verify_stmts,/* todo_flags_finish */
 401   0                                     /* letter */ };
 402
 403 /* Do the actions required to initialize internal data structures used
 404    in tree-ssa optimization passes.  */
 405
 406 static unsigned int
 407 execute_init_datastructures (void)
 408 {
 409   /* Allocate hash tables, arrays and other structures.  */
 410   init_tree_ssa ();
 411   return 0;
 412 }
 413
 414 /* Gate: initialize or not the SSA datastructures.  */
 415
 416 static bool
 417 gate_init_datastructures (void)
 418 {
 419   return (optimize >= 1);
 420 }
 421
 422 struct tree_opt_pass pass_init_datastructures =
 423 {
 424   NULL,                                 /* name */
 425   gate_init_datastructures,             /* gate */
 426   execute_init_datastructures,          /* execute */
 427   NULL,                                 /* sub */
 428   NULL,                                 /* next */
 429   0,                                    /* static_pass_number */
 430   0,                                    /* tv_id */
 431   PROP_cfg,                             /* properties_required */
 432   0,                                    /* properties_provided */
 433   0,                                    /* properties_destroyed */
 434   0,                                    /* todo_flags_start */
 435   0,                                    /* todo_flags_finish */
 436   0                                     /* letter */
 437 };
 438
 439 void
 440 tree_lowering_passes (tree fn)
 441 {
 442   tree saved_current_function_decl = current_function_decl;
 443
 444   current_function_decl = fn;
 445   push_cfun (DECL_STRUCT_FUNCTION (fn));
 446   tree_register_cfg_hooks ();
 447   bitmap_obstack_initialize (NULL);
 448   execute_pass_list (all_lowering_passes);
 449   if (optimize && cgraph_global_info_ready)
 450     execute_pass_list (pass_early_local_passes.sub);
 451   free_dominance_info (CDI_POST_DOMINATORS);
 452   free_dominance_info (CDI_DOMINATORS);
 453   compact_blocks ();
 454   current_function_decl = saved_current_function_decl;
 455   bitmap_obstack_release (NULL);
 456   pop_cfun ();
 457 }
 458
 459 /* Update recursively all inlined_to pointers of functions
 460    inlined into NODE to INLINED_TO.  */
 461 static void
 462 update_inlined_to_pointers (struct cgraph_node *node,
 463                             struct cgraph_node *inlined_to)
 464 {
 465   struct cgraph_edge *e;
 466   for (e = node->callees; e; e = e->next_callee)
 467     {
 468       if (e->callee->global.inlined_to)
 469         {
 470           e->callee->global.inlined_to = inlined_to;
 471           update_inlined_to_pointers (e->callee, inlined_to);
 472         }
 473     }
 474 }
 475
 476 \f
 477 /* For functions-as-trees languages, this performs all optimization and
 478    compilation for FNDECL.  */
 479
 480 void
 481 tree_rest_of_compilation (tree fndecl)
 482 {
 483   location_t saved_loc;
 484   struct cgraph_node *node;
 485
 486   timevar_push (TV_EXPAND);
 487
 488   gcc_assert (!flag_unit_at_a_time || cgraph_global_info_ready);
 489
 490   node = cgraph_node (fndecl);
 491
 492   /* Initialize the default bitmap obstack.  */
 493   bitmap_obstack_initialize (NULL);
 494
 495   /* We might need the body of this function so that we can expand
 496      it inline somewhere else.  */
 497   if (cgraph_preserve_function_body_p (fndecl))
 498     save_inline_function_body (node);
 499
 500   /* Initialize the RTL code for the function.  */
 501   current_function_decl = fndecl;
 502   saved_loc = input_location;
 503   input_location = DECL_SOURCE_LOCATION (fndecl);
 504   init_function_start (fndecl);
 505
 506   /* Even though we're inside a function body, we still don't want to
 507      call expand_expr to calculate the size of a variable-sized array.
 508      We haven't necessarily assigned RTL to all variables yet, so it's
 509      not safe to try to expand expressions involving them.  */
 510   cfun->x_dont_save_pending_sizes_p = 1;
 511
 512   tree_register_cfg_hooks ();
 513
 514   if (flag_inline_trees)
 515     {
 516       struct cgraph_edge *e;
 517       for (e = node->callees; e; e = e->next_callee)
 518         if (!e->inline_failed || warn_inline)
 519           break;
 520       if (e)
 521         {
 522           timevar_push (TV_INTEGRATION);
 523           optimize_inline_calls (fndecl);
 524           timevar_pop (TV_INTEGRATION);
 525         }
 526     }
 527   /* In non-unit-at-a-time we must mark all referenced functions as needed.
 528      */
 529   if (!flag_unit_at_a_time)
 530     {
 531       struct cgraph_edge *e;
 532       for (e = node->callees; e; e = e->next_callee)
 533         if (e->callee->analyzed)
 534           cgraph_mark_needed_node (e->callee);
 535     }
 536
 537   /* We are not going to maintain the cgraph edges up to date.
 538      Kill it so it won't confuse us.  */
 539   cgraph_node_remove_callees (node);
 540
 541   bitmap_obstack_initialize (&reg_obstack); /* FIXME, only at RTL generation*/
 542   /* Perform all tree transforms and optimizations.  */
 543   execute_pass_list (all_passes);
 544
 545   bitmap_obstack_release (&reg_obstack);
 546
 547   /* Release the default bitmap obstack.  */
 548   bitmap_obstack_release (NULL);
 549
 550   DECL_SAVED_TREE (fndecl) = NULL;
 551   cfun = 0;
 552
 553   /* If requested, warn about function definitions where the function will
 554      return a value (usually of some struct or union type) which itself will
 555      take up a lot of stack space.  */
 556   if (warn_larger_than && !DECL_EXTERNAL (fndecl) && TREE_TYPE (fndecl))
 557     {
 558       tree ret_type = TREE_TYPE (TREE_TYPE (fndecl));
 559
 560       if (ret_type && TYPE_SIZE_UNIT (ret_type)
 561           && TREE_CODE (TYPE_SIZE_UNIT (ret_type)) == INTEGER_CST
 562           && 0 < compare_tree_int (TYPE_SIZE_UNIT (ret_type),
 563                                    larger_than_size))
 564         {
 565           unsigned int size_as_int
 566             = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (ret_type));
 567
 568           if (compare_tree_int (TYPE_SIZE_UNIT (ret_type), size_as_int) == 0)
 569             warning (0, "size of return value of %q+D is %u bytes",
 570                      fndecl, size_as_int);
 571           else
 572             warning (0, "size of return value of %q+D is larger than %wd bytes",
 573                      fndecl, larger_than_size);
 574         }
 575     }
 576
 577   if (!flag_inline_trees)
 578     {
 579       DECL_SAVED_TREE (fndecl) = NULL;
 580       if (DECL_STRUCT_FUNCTION (fndecl) == 0
 581           && !cgraph_node (fndecl)->origin)
 582         {
 583           /* Stop pointing to the local nodes about to be freed.
 584              But DECL_INITIAL must remain nonzero so we know this
 585              was an actual function definition.
 586              For a nested function, this is done in c_pop_function_context.
 587              If rest_of_compilation set this to 0, leave it 0.  */
 588           if (DECL_INITIAL (fndecl) != 0)
 589             DECL_INITIAL (fndecl) = error_mark_node;
 590         }
 591     }
 592
 593   input_location = saved_loc;
 594
 595   ggc_collect ();
 596   timevar_pop (TV_EXPAND);
 597 }