Port r7868 (constant masking) to x64.

src/x64/macro-assembler-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 756 matching lines @@
   // ---------------------------------------------------------------------------
   // Macro instructions.
 
   // Load a register with a long value as efficiently as possible.
   void Set(Register dst, int64_t x);
   void Set(const Operand& dst, int64_t x);
 
   // Move if the registers are not identical.
   void Move(Register target, Register source);
 
+  // Support for constant splitting.
+  bool IsUnsafeInt(const int x);
+  void SafeMove(Register dst, Smi* src);
+  void SafePush(Smi* src);
+
   // Bit-field support.
   void TestBit(const Operand& dst, int bit_index);
 
   // Handle support
   void Move(Register dst, Handle<Object> source);
   void Move(const Operand& dst, Handle<Object> source);
   void Cmp(Register dst, Handle<Object> source);
   void Cmp(const Operand& dst, Handle<Object> source);
   void Cmp(Register dst, Smi* src);
   void Cmp(const Operand& dst, Smi* src);
@@ skipping 688 matching lines @@
     masm->popfd();                                                        \
   }                                                                       \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_MACRO_ASSEMBLER_X64_H_