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

src/x64/lithium-codegen-x64.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 269 matching lines @@
   void RecordSafepoint(Safepoint::DeoptMode mode);
   void RecordSafepointWithRegisters(LPointerMap* pointers,
                                     int arguments,
                                     Safepoint::DeoptMode mode);
   void RecordPosition(int position);
 
   static Condition TokenToCondition(Token::Value op, bool is_unsigned);
   void EmitGoto(int block);
   template<class InstrType>
   void EmitBranch(InstrType instr, Condition cc);
+  template<class InstrType>
+  void EmitFalseBranch(InstrType instr, Condition cc);
   void EmitNumberUntagD(
       Register input,
       XMMRegister result,
       bool allow_undefined_as_nan,
       bool deoptimize_on_minus_zero,
       LEnvironment* env,
       NumberUntagDMode mode = NUMBER_CANDIDATE_IS_ANY_TAGGED);
 
   // Emits optimized code for typeof x == "y".  Modifies input register.
   // Returns the condition on which a final split to
@@ skipping 137 matching lines @@
   LCodeGen* codegen_;
   Label entry_;
   Label exit_;
   Label* external_exit_;
   int instruction_index_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_LITHIUM_CODEGEN_X64_H_