Minor change to for-in...

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 3907 matching lines @@
   __ cmpq(rcx, rdx);
   end_del_check.Branch(equal);
 
   // Convert the entry to a string (or null if it isn't a property anymore).
   frame_->EmitPush(frame_->ElementAt(4));  // push enumerable
   frame_->EmitPush(rbx);  // push entry
   frame_->InvokeBuiltin(Builtins::FILTER_KEY, CALL_FUNCTION, 2);
   __ movq(rbx, rax);
 
   // If the property has been removed while iterating, we just skip it.
-  __ CompareRoot(rbx, Heap::kNullValueRootIndex);
+  __ SmiCompare(rbx, Smi::FromInt(0));
   node->continue_target()->Branch(equal);
 
   end_del_check.Bind();
   // Store the entry in the 'each' expression and take another spin in the
   // loop.  rdx: i'th entry of the enum cache (or string there of)
   frame_->EmitPush(rbx);
   { Reference each(this, node->each());
     // Loading a reference may leave the frame in an unspilled state.
     frame_->SpillAll();
     if (!each.is_illegal()) {
@@ skipping 8682 matching lines @@
 #undef __
 
 void RecordWriteStub::Generate(MacroAssembler* masm) {
   masm->RecordWriteHelper(object_, addr_, scratch_);
   masm->ret(0);
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64