[x64] Improve key value sign-extension of dehoisted LoadKeyed/StoreKeyed

src/x64/lithium-x64.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 248 matching lines @@
   bool IsMarkedAsCall() const { return IsCall(); }
 
   virtual bool HasResult() const = 0;
   virtual LOperand* result() const = 0;
 
   LOperand* FirstInput() { return InputAt(0); }
   LOperand* Output() { return HasResult() ? result() : NULL; }
 
   virtual bool HasInterestingComment(LCodeGen* gen) const { return true; }
 
+  virtual bool MustSignExtendResult() const { return false; }
+
 #ifdef DEBUG
   void VerifyCall();
 #endif
 
  private:
   // Iterator support.
   friend class InputIterator;
   virtual int InputCount() = 0;
   virtual LOperand* InputAt(int i) = 0;
 
@@ skipping 15 matching lines @@
 class LTemplateResultInstruction : public LInstruction {
  public:
   // Allow 0 or 1 output operands.
   STATIC_ASSERT(R == 0 || R == 1);
   virtual bool HasResult() const V8_FINAL V8_OVERRIDE {
     return R != 0 && result() != NULL;
   }
   void set_result(LOperand* operand) { results_[0] = operand; }
   LOperand* result() const { return results_[0]; }
 
+  virtual bool MustSignExtendResult() const V8_FINAL V8_OVERRIDE;
+
  protected:
   EmbeddedContainer<LOperand*, R> results_;
 };
 
 
 // R = number of result operands (0 or 1).
 // I = number of input operands.
 // T = number of temporary operands.
 template<int R, int I, int T>
 class LTemplateInstruction : public LTemplateResultInstruction<R> {
@@ skipping 2351 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(LChunkBuilder);
 };
 
 #undef DECLARE_HYDROGEN_ACCESSOR
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::int
 
 #endif  // V8_X64_LITHIUM_X64_H_