[x64] Compare map instead of value to heap number map in ToStringStub.

src/x64/code-stubs-x64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
 #include "src/ic/handler-compiler.h"
@@ skipping 3114 matching lines @@
 
   Label not_string;
   __ CmpObjectType(rax, FIRST_NONSTRING_TYPE, rdi);
   // rax: receiver
   // rdi: receiver map
   __ j(above_equal, &not_string, Label::kNear);
   __ Ret();
   __ bind(&not_string);
 
   Label not_heap_number;
-  __ CompareRoot(rax, Heap::kHeapNumberMapRootIndex);
+  __ CompareRoot(rdi, Heap::kHeapNumberMapRootIndex);
   __ j(not_equal, &not_heap_number, Label::kNear);
   __ bind(&is_number);
   NumberToStringStub stub(isolate());
   __ TailCallStub(&stub);
   __ bind(&not_heap_number);
 
   Label not_oddball;
   __ CmpInstanceType(rdi, ODDBALL_TYPE);
   __ j(not_equal, &not_oddball, Label::kNear);
   __ movp(rax, FieldOperand(rax, Oddball::kToStringOffset));
@@ skipping 2395 matching lines @@
                            kStackSpace, nullptr, return_value_operand, NULL);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64