Improve dead phi elimination....

src/hydrogen-instructions.h

 // Copyright 2011 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 1782 matching lines @@
  protected:
   virtual bool DataEquals(HValue* other) { return true; }
 };
 
 
 class HPhi: public HValue {
  public:
   explicit HPhi(int merged_index)
       : inputs_(2),
         merged_index_(merged_index),
-        phi_id_(-1) {
+        phi_id_(-1),
+        is_live_(false) {
     for (int i = 0; i < Representation::kNumRepresentations; i++) {
       non_phi_uses_[i] = 0;
       indirect_uses_[i] = 0;
     }
     ASSERT(merged_index >= 0);
     set_representation(Representation::Tagged());
     SetFlag(kFlexibleRepresentation);
   }
 
   virtual Representation InferredRepresentation() {
@@ skipping 13 matching lines @@
 
   virtual Range* InferRange();
   virtual Representation RequiredInputRepresentation(int index) const {
     return representation();
   }
   virtual HType CalculateInferredType();
   virtual int OperandCount() { return inputs_.length(); }
   virtual HValue* OperandAt(int index) { return inputs_[index]; }
   HValue* GetRedundantReplacement();
   void AddInput(HValue* value);
+  bool HasRealUses();
 
   bool IsReceiver() { return merged_index_ == 0; }
 
   int merged_index() const { return merged_index_; }
 
   virtual const char* Mnemonic() const { return "phi"; }
 
   virtual void PrintTo(StringStream* stream);
 
 #ifdef DEBUG
@@ skipping 18 matching lines @@
   int tagged_indirect_uses() const {
     return indirect_uses_[Representation::kTagged];
   }
   int int32_indirect_uses() const {
     return indirect_uses_[Representation::kInteger32];
   }
   int double_indirect_uses() const {
     return indirect_uses_[Representation::kDouble];
   }
   int phi_id() { return phi_id_; }
+  bool is_live() { return is_live_; }
+  void set_is_live(bool b) { is_live_ = b; }
 
  protected:
   virtual void DeleteFromGraph();
   virtual void InternalSetOperandAt(int index, HValue* value) {
     inputs_[index] = value;
   }
 
  private:
   ZoneList<HValue*> inputs_;
   int merged_index_;
 
   int non_phi_uses_[Representation::kNumRepresentations];
   int indirect_uses_[Representation::kNumRepresentations];
   int phi_id_;
+  bool is_live_;
 };
 
 
 class HArgumentsObject: public HTemplateInstruction<0> {
  public:
   HArgumentsObject() {
     set_representation(Representation::Tagged());
     SetFlag(kIsArguments);
   }
 
@@ skipping 1547 matching lines @@
   HValue* object() { return left(); }
   HValue* key() { return right(); }
 };
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_