Add support to load/store byte fields.

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 763 matching lines @@
 
   // Checks if the given register or operand is a unique name
   void JumpIfNotUniqueName(Register reg, Label* not_unique_name,
                            Label::Distance distance = Label::kFar);
   void JumpIfNotUniqueName(Operand operand, Label* not_unique_name,
                            Label::Distance distance = Label::kFar);
 
   // ---------------------------------------------------------------------------
   // Macro instructions.
 
+  // Load/store with specific representation.
+  void Load(Register dst, const Operand& src, Representation r);
+  void Store(const Operand& dst, Register src, Representation r);
+
   // 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);
 
   // cvtsi2sd instruction only writes to the low 64-bit of dst register, which
   // hinders register renaming and makes dependence chains longer. So we use
   // xorps to clear the dst register before cvtsi2sd to solve this issue.
   void Cvtlsi2sd(XMMRegister dst, Register src);
   void Cvtlsi2sd(XMMRegister dst, const Operand& src);
 
@@ skipping 785 matching lines @@
     masm->popfq();                                                           \
   }                                                                          \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_MACRO_ASSEMBLER_X64_H_