Never hchange nan-hole to hole or hole to nan-hole.

src/hydrogen-mark-deoptimize.h

 // Copyright 2013 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 40 matching lines @@
   void ProcessPhi(HPhi* phi);
 
   // Preallocated worklist used as an optimization so we don't have
   // to allocate a new ZoneList for every ProcessPhi() invocation.
   ZoneList<HPhi*> worklist_;
 
   DISALLOW_COPY_AND_ASSIGN(HMarkDeoptimizeOnUndefinedPhase);
 };
 
 
+class HComputeChangeUndefinedToNaN : public HPhase {
+ public:
+  explicit HComputeChangeUndefinedToNaN(HGraph* graph)
+      : HPhase("H_Compute change undefined to nan", graph) {}
+
+  void Run();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(HComputeChangeUndefinedToNaN);
+};
+
+
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_MARK_DEOPTIMIZE_H_