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

src/x64/lithium-codegen-x64.h

Index: src/x64/lithium-codegen-x64.h
diff --git a/src/x64/lithium-codegen-x64.h b/src/x64/lithium-codegen-x64.h
index 0f1a9cdb7096546b3c83e0d5461a1a7526c318bb..3e8ac160e3c30e70a6e0b204bcc168a5f5119c31 100644
--- a/src/x64/lithium-codegen-x64.h
+++ b/src/x64/lithium-codegen-x64.h
@@ -86,6 +86,7 @@ class LCodeGen: public LCodeGenBase {
   Register ToRegister(LOperand* op) const;
   XMMRegister ToDoubleRegister(LOperand* op) const;
   bool IsInteger32Constant(LConstantOperand* op) const;
+  bool IsDehoistedKeyConstant(LConstantOperand* op) const;
   bool IsSmiConstant(LConstantOperand* op) const;
   int32_t ToInteger32(LConstantOperand* op) const;
   Smi* ToSmi(LConstantOperand* op) const;
@@ -159,6 +160,7 @@ class LCodeGen: public LCodeGenBase {
 
   // Code generation passes.  Returns true if code generation should
   // continue.
+  void GenerateBodyInstructionPost(LInstruction* instr) V8_OVERRIDE;
   bool GeneratePrologue();
   bool GenerateDeferredCode();
   bool GenerateJumpTable();