Fix build problems on Windows 64-bit by casting.

src/x64/builtins-x64.cc

 // 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 1222 matching lines @@
   __ push(rdx);
   __ movq(rsi, FieldOperand(rdi, JSFunction::kContextOffset));
 
   // Load the number of arguments and setup pointer to the arguments.
   __ movq(rax, rcx);
   __ movq(rbx, r8);
 #endif  // _WIN64
 
   // Set up the roots register.
   ExternalReference roots_address = ExternalReference::roots_address();
-  __ movq(r13, roots_address);
+  __ movq(kRootRegister, roots_address);
 
   // Current stack contents:
   // [rsp + 2 * kPointerSize ... ]: Internal frame
   // [rsp + kPointerSize]         : function
   // [rsp]                        : receiver
   // Current register contents:
   // rax : argc
   // rbx : argv
   // rsi : context
   // rdi : function
@@ skipping 35 matching lines @@
 void Builtins::Generate_JSEntryTrampoline(MacroAssembler* masm) {
   Generate_JSEntryTrampolineHelper(masm, false);
 }
 
 
 void Builtins::Generate_JSConstructEntryTrampoline(MacroAssembler* masm) {
   Generate_JSEntryTrampolineHelper(masm, true);
 }
 
 } }  // namespace v8::internal