Perform a fix point iteration for GVN.

src/hydrogen-gvn.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 356 matching lines @@
       : HPhase("H_Global value numbering", graph),
         removed_side_effects_(false),
         block_side_effects_(graph->blocks()->length(), zone()),
         loop_side_effects_(graph->blocks()->length(), zone()),
         visited_on_paths_(graph->blocks()->length(), zone()) {
     ASSERT(!AllowHandleAllocation::IsAllowed());
     block_side_effects_.AddBlock(GVNFlagSet(), graph->blocks()->length(),
                                  zone());
     loop_side_effects_.AddBlock(GVNFlagSet(), graph->blocks()->length(),
                                 zone());
-  }
+}
+
+
+void HGlobalValueNumberingPhase::Reset() {
+  block_side_effects_.Clear();
+  loop_side_effects_.Clear();
+  visited_on_paths_.Clear();
+  block_side_effects_.AddBlock(GVNFlagSet(), graph()->blocks()->length(),
+                               zone());
+  loop_side_effects_.AddBlock(GVNFlagSet(), graph()->blocks()->length(),
+                              zone());
+}
+
 
 void HGlobalValueNumberingPhase::Analyze() {
   removed_side_effects_ = false;
   ComputeBlockSideEffects();
   if (FLAG_loop_invariant_code_motion) {
     LoopInvariantCodeMotion();
   }
   AnalyzeGraph();
 }
 
@@ skipping 396 matching lines @@
           GVNFlag changes_flag = HValue::ChangesFlagFromInt(i);
           GVNFlag depends_on_flag = HValue::DependsOnFlagFromInt(i);
           if (instr->DependsOnFlags().Contains(depends_on_flag) &&
               (other != NULL)) {
             TRACE_GVN_5("Side-effect #%d in %d (%s) is dominated by %d (%s)\n",
                         i,
                         instr->id(),
                         instr->Mnemonic(),
                         other->id(),
                         other->Mnemonic());
-            instr->HandleSideEffectDominator(changes_flag, other);
+            if (instr->HandleSideEffectDominator(changes_flag, other)) {
+              removed_side_effects_ = true;
+            }
           }
         }
       }
       // Instruction was unlinked during graph traversal.
       if (!instr->IsLinked()) continue;
 
       GVNFlagSet flags = instr->ChangesFlags();
       if (!flags.IsEmpty()) {
         // Clear all instructions in the map that are affected by side effects.
         // Store instruction as the dominating one for tracked side effects.
@@ skipping 43 matching lines @@
                                                       dominated);
         successor_map->Kill(side_effects_on_all_paths);
         successor_dominators->Kill(side_effects_on_all_paths);
       }
     }
     current = next;
   }
 }
 
 } }  // namespace v8::internal