[Isolates] Avoid dereferencing Isolate::Current() to check oddball identities...

src/x64/codegen-x64.cc

 // Copyright 2010 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 1176 matching lines @@
           unsigned_left >>= shift_amount;
         }
         ASSERT(Smi::IsValid(static_cast<int32_t>(unsigned_left)));
         answer_object = Smi::FromInt(static_cast<int32_t>(unsigned_left));
         break;
       }
     default:
       UNREACHABLE();
       break;
   }
-  if (answer_object == HEAP->undefined_value()) {
+  if (answer_object->IsUndefined()) {
     return false;
   }
   frame_->Push(Handle<Object>(answer_object));
   return true;
 }
 
 
 void CodeGenerator::JumpIfNotSmiUsingTypeInfo(Register reg,
                                               TypeInfo type,
                                               DeferredCode* deferred) {
@@ skipping 10903 matching lines @@
 #undef __
 
 void RecordWriteStub::Generate(MacroAssembler* masm) {
   masm->RecordWriteHelper(object_, addr_, scratch_);
   masm->ret(0);
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64