DateField cache should check the ExternalOperand instead of ExternalReference on X64

Review URL: https://chromiumcodereview.appspot.com/12637025
Patch from Weiliang Lin <weiliang.lin2@gmail.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13919 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/x64/full-codegen-x64.cc

@@ -3058,7 +3058,8 @@ void FullCodeGenerator::EmitDateField(CallRuntime* expr) {
   } else {
     if (index->value() < JSDate::kFirstUncachedField) {
       ExternalReference stamp = ExternalReference::date_cache_stamp(isolate());
-      __ movq(scratch, stamp);
+      Operand stamp_operand = __ ExternalOperand(stamp);
+      __ movq(scratch, stamp_operand);
       __ cmpq(scratch, FieldOperand(object, JSDate::kCacheStampOffset));
       __ j(not_equal, &runtime, Label::kNear);
       __ movq(result, FieldOperand(object, JSDate::kValueOffset +

src/x64/lithium-codegen-x64.cc

@@ -1643,7 +1643,8 @@ void LCodeGen::DoDateField(LDateField* instr) {
   } else {
     if (index->value() < JSDate::kFirstUncachedField) {
       ExternalReference stamp = ExternalReference::date_cache_stamp(isolate());
-      __ movq(kScratchRegister, stamp);
+      Operand stamp_operand = __ ExternalOperand(stamp);
+      __ movq(kScratchRegister, stamp_operand);
       __ cmpq(kScratchRegister, FieldOperand(object,
                                              JSDate::kCacheStampOffset));
       __ j(not_equal, &runtime, Label::kNear);