Turn the NumberToStringStub into a hydrogen stub.

src/hydrogen-instructions.h

 // Copyright 2012 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 5631 matching lines @@
 
   inline HObjectAccess WithRepresentation(Representation representation) {
     return HObjectAccess(portion(), offset(), representation, name());
   }
 
   static HObjectAccess ForHeapNumberValue() {
     return HObjectAccess(
         kDouble, HeapNumber::kValueOffset, Representation::Double());
   }
 
+  static HObjectAccess ForHeapNumberValueLowestBits() {
+    return HObjectAccess(kDouble,
+                         HeapNumber::kValueOffset,
+                         Representation::Integer32());
+  }
+
+  static HObjectAccess ForHeapNumberValueHighestBits() {
+    return HObjectAccess(kDouble,
+                         HeapNumber::kValueOffset + kIntSize,
+                         Representation::Integer32());
+  }
+
   static HObjectAccess ForElementsPointer() {
     return HObjectAccess(kElementsPointer, JSObject::kElementsOffset);
   }
 
   static HObjectAccess ForLiteralsPointer() {
     return HObjectAccess(kInobject, JSFunction::kLiteralsOffset);
   }
 
   static HObjectAccess ForNextFunctionLinkPointer() {
     return HObjectAccess(kInobject, JSFunction::kNextFunctionLinkOffset);
@@ skipping 1386 matching lines @@
   virtual bool IsDeletable() const V8_OVERRIDE { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_