* ChangeLog.vta: New.

[pf3gnuchains/gcc-fork.git] / gcc / tree-ssa-dce.c

diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c
index 381d910..bc17003 100644 (file)
--- a/gcc/tree-ssa-dce.c
+++ b/gcc/tree-ssa-dce.c
@@ -1,5 +1,6 @@
 /* Dead code elimination pass for the GNU compiler.
-   Copyright (C) 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
+   Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007
+   Free Software Foundation, Inc.
    Contributed by Ben Elliston <bje@redhat.com>
    and Andrew MacLeod <amacleod@redhat.com>
    Adapted to use control dependence by Steven Bosscher, SUSE Labs.
@@ -8,7 +9,7 @@ This file is part of GCC.
    
 GCC is free software; you can redistribute it and/or modify it
 under the terms of the GNU General Public License as published by the
-Free Software Foundation; either version 2, or (at your option) any
+Free Software Foundation; either version 3, or (at your option) any
 later version.
    
 GCC is distributed in the hope that it will be useful, but WITHOUT
@@ -17,9 +18,8 @@ FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 for more details.
    
 You should have received a copy of the GNU General Public License
-along with GCC; see the file COPYING.  If not, write to the Free
-Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
-02110-1301, USA.  */
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
 
 /* Dead code elimination.
 
@@ -286,6 +286,7 @@ mark_stmt_if_obviously_necessary (tree stmt, bool aggressive)
     case ASM_EXPR:
     case RESX_EXPR:
     case RETURN_EXPR:
+    case CHANGE_DYNAMIC_TYPE_EXPR:
       mark_stmt_necessary (stmt, true);
       return;
 
@@ -591,7 +592,7 @@ remove_dead_stmt (block_stmt_iterator *i, basic_block bb)
       basic_block post_dom_bb;
 
       /* The post dominance info has to be up-to-date.  */
-      gcc_assert (dom_computed[CDI_POST_DOMINATORS] == DOM_OK);
+      gcc_assert (dom_info_state (CDI_POST_DOMINATORS) == DOM_OK);
       /* Get the immediate post dominator of bb.  */
       post_dom_bb = get_immediate_dominator (CDI_POST_DOMINATORS, bb);
 
@@ -607,7 +608,6 @@ remove_dead_stmt (block_stmt_iterator *i, basic_block bb)
         3. If the post dominator has PHI nodes we may be able to compute
            the right PHI args for them.
 
-
         In each of these cases we must remove the control statement
         as it may reference SSA_NAMEs which are going to be removed and
         we remove all but one outgoing edge from the block.  */
@@ -620,6 +620,11 @@ remove_dead_stmt (block_stmt_iterator *i, basic_block bb)
          /* Redirect the first edge out of BB to reach POST_DOM_BB.  */
          redirect_edge_and_branch (EDGE_SUCC (bb, 0), post_dom_bb);
          PENDING_STMT (EDGE_SUCC (bb, 0)) = NULL;
+
+         /* It is not sufficient to set cfg_altered below during edge
+            removal, in case BB has two successors and one of them
+            is POST_DOM_BB.  */
+         cfg_altered = true;
        }
       EDGE_SUCC (bb, 0)->probability = REG_BR_PROB_BASE;
       EDGE_SUCC (bb, 0)->count = bb->count;
@@ -688,11 +693,39 @@ eliminate_unnecessary_stmts (void)
            {
              tree call = get_call_expr_in (t);
              if (call)
-               notice_special_calls (call);
+               {
+                 tree name;
+
+                 /* When LHS of var = call (); is dead, simplify it into
+                    call (); saving one operand.  */
+                 if (TREE_CODE (t) == GIMPLE_MODIFY_STMT
+                     && (TREE_CODE ((name = GIMPLE_STMT_OPERAND (t, 0)))
+                         == SSA_NAME)
+                     && !TEST_BIT (processed, SSA_NAME_VERSION (name)))
+                   {
+                     tree oldlhs = GIMPLE_STMT_OPERAND (t, 0);
+                     something_changed = true;
+                     if (dump_file && (dump_flags & TDF_DETAILS))
+                       {
+                         fprintf (dump_file, "Deleting LHS of call: ");
+                         print_generic_stmt (dump_file, t, TDF_SLIM);
+                         fprintf (dump_file, "\n");
+                       }
+                     push_stmt_changes (bsi_stmt_ptr (i));
+                     TREE_BLOCK (call) = TREE_BLOCK (t);
+                     bsi_replace (&i, call, false);
+                     maybe_clean_or_replace_eh_stmt (t, call);
+                     mark_symbols_for_renaming (call);
+                     pop_stmt_changes (bsi_stmt_ptr (i));
+                     release_ssa_name (oldlhs);
+                   }
+                 notice_special_calls (call);
+               }
              bsi_next (&i);
            }
        }
     }
+
   return something_changed;
 }
 
@@ -812,8 +845,8 @@ perform_tree_ssa_dce (bool aggressive)
   something_changed |= eliminate_unnecessary_stmts ();
   something_changed |= cfg_altered;
 
-  if (aggressive && something_changed)
-    free_dominance_info (CDI_POST_DOMINATORS);
+  /* We do not update postdominators, so free them unconditionally.  */
+  free_dominance_info (CDI_POST_DOMINATORS);
 
   /* If we removed paths in the CFG, then we need to update
      dominators as well.  I haven't investigated the possibility