Refactor Hydrogen GVN into an HPhase and use the phase zone.

src/hydrogen-gvn.h

 // 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 58 matching lines @@
  private:
   int capacity_;
   int length_;
   int* dense_;
   int* sparse_;
 
   DISALLOW_COPY_AND_ASSIGN(SparseSet);
 };
 
 
-class HGlobalValueNumberer BASE_EMBEDDED {
+// Perform common subexpression elimination and loop-invariant code motion.
+class HGlobalValueNumberingPhase : public HPhase {
  public:
-  HGlobalValueNumberer(HGraph* graph, CompilationInfo* info);
+  explicit HGlobalValueNumberingPhase(HGraph* graph);
 
-  // Returns true if values with side effects are removed.
-  bool Analyze();
+  void Run() {
+    Analyze();
+    // Trigger a second analysis pass to further eliminate duplicate values
+    // that could only be discovered by removing side-effect-generating
+    // instructions during the first pass.
+    if (FLAG_smi_only_arrays && removed_side_effects_) {
+      Analyze();
+      ASSERT(!removed_side_effects_);
+    }
+  }
 
  private:
+  void Analyze();
   GVNFlagSet CollectSideEffectsOnPathsToDominatedBlock(
       HBasicBlock* dominator,
       HBasicBlock* dominated);
   void AnalyzeGraph();
   void ComputeBlockSideEffects();
   void LoopInvariantCodeMotion();
   void ProcessLoopBlock(HBasicBlock* block,
                         HBasicBlock* before_loop,
                         GVNFlagSet loop_kills,
                         GVNFlagSet* accumulated_first_time_depends,
                         GVNFlagSet* accumulated_first_time_changes);
   bool AllowCodeMotion();
   bool ShouldMove(HInstruction* instr, HBasicBlock* loop_header);
 
-  HGraph* graph() { return graph_; }
-  CompilationInfo* info() { return info_; }
-  Zone* zone() { return &zone_; }
-
-  HGraph* graph_;
-  CompilationInfo* info_;
   bool removed_side_effects_;
 
-  Zone zone_;
-
   // A map of block IDs to their side effects.
   ZoneList<GVNFlagSet> block_side_effects_;
 
   // A map of loop header block IDs to their loop's side effects.
   ZoneList<GVNFlagSet> loop_side_effects_;
 
   // Used when collecting side effects on paths from dominator to
   // dominated.
   SparseSet visited_on_paths_;
+
+  DISALLOW_COPY_AND_ASSIGN(HGlobalValueNumberingPhase);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_GVN_H_