Implement caching scheme for Date fields.

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index aa86218e6da2541cfdafd8f419e8e346e4fe54f1..c90db9ee61b4c458898b242034e45630202535d7 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1609,8 +1609,8 @@ LInstruction* LChunkBuilder::DoDateField(HDateField* instr) {
 
 
 LInstruction* LChunkBuilder::DoSetDateField(HSetDateField* instr) {
-  LOperand* date = UseRegister(instr->OperandAt(1));
-  LOperand* value = UseRegister(instr->OperandAt(2));
+  LOperand* date = UseTempRegister(instr->OperandAt(1));
+  LOperand* value = UseTempRegister(instr->OperandAt(2));
   LSetDateField* result = new LSetDateField(date, value, instr->index());
   return DefineAsRegister(result);
 }