Declare register names as constants in assembler-x64.h. Fix for issue 615.

src/x64/macro-assembler-x64.h

 // Copyright 2009 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 18 matching lines @@
 #define V8_X64_MACRO_ASSEMBLER_X64_H_
 
 #include "assembler.h"
 
 namespace v8 {
 namespace internal {
 
 // Default scratch register used by MacroAssembler (and other code that needs
 // a spare register). The register isn't callee save, and not used by the
 // function calling convention.
-static const Register kScratchRegister = r10;
+static const Register kScratchRegister = { 10 };  // r10.
 
 // Convenience for platform-independent signatures.
 typedef Operand MemOperand;
 
 // Forward declaration.
 class JumpTarget;
 
 struct SmiIndex {
   SmiIndex(Register index_register, ScaleFactor scale)
       : reg(index_register),
@@ skipping 754 matching lines @@
   }                                                                       \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_MACRO_ASSEMBLER_X64_H_