Allow HPhis to have an invalid merge index.

src/hydrogen-instructions.h

 // Copyright 2012 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 3002 matching lines @@
  public:
   HPhi(int merged_index, Zone* zone)
       : inputs_(2, zone),
         merged_index_(merged_index),
         phi_id_(-1),
         induction_variable_data_(NULL) {
     for (int i = 0; i < Representation::kNumRepresentations; i++) {
       non_phi_uses_[i] = 0;
       indirect_uses_[i] = 0;
     }
-    ASSERT(merged_index >= 0);
+    ASSERT(merged_index >= 0 || merged_index == kInvalidMergedIndex);
     SetFlag(kFlexibleRepresentation);
     SetFlag(kAllowUndefinedAsNaN);
   }
 
   virtual Representation RepresentationFromInputs();
 
   virtual Range* InferRange(Zone* zone);
   virtual void InferRepresentation(HInferRepresentationPhase* h_infer);
   virtual Representation RequiredInputRepresentation(int index) {
     return representation();
   }
   virtual Representation KnownOptimalRepresentation() {
     return representation();
   }
   virtual HType CalculateInferredType();
   virtual int OperandCount() { return inputs_.length(); }
   virtual HValue* OperandAt(int index) const { return inputs_[index]; }
   HValue* GetRedundantReplacement();
   void AddInput(HValue* value);
   bool HasRealUses();
 
   bool IsReceiver() const { return merged_index_ == 0; }
+  bool HasMergedIndex() const { return merged_index_ != kInvalidMergedIndex; }
 
   int merged_index() const { return merged_index_; }
 
   InductionVariableData* induction_variable_data() {
     return induction_variable_data_;
   }
   bool IsInductionVariable() {
     return induction_variable_data_ != NULL;
   }
   bool IsLimitedInductionVariable() {
@@ skipping 42 matching lines @@
   int phi_id() { return phi_id_; }
 
   static HPhi* cast(HValue* value) {
     ASSERT(value->IsPhi());
     return reinterpret_cast<HPhi*>(value);
   }
   virtual Opcode opcode() const { return HValue::kPhi; }
 
   void SimplifyConstantInputs();
 
+  // Marker value representing an invalid merge index.
+  static const int kInvalidMergedIndex = -1;
+
  protected:
   virtual void DeleteFromGraph();
   virtual void InternalSetOperandAt(int index, HValue* value) {
     inputs_[index] = value;
   }
 
  private:
   ZoneList<HValue*> inputs_;
   int merged_index_;
 
@@ skipping 3660 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_