Fix Win64 build

src/compiler/x64/code-generator-x64.cc

Index: src/compiler/x64/code-generator-x64.cc
diff --git a/src/compiler/x64/code-generator-x64.cc b/src/compiler/x64/code-generator-x64.cc
index dd97bb338ffbfb1cb91713c6f9a7eba27888763c..a398c2dd10a736532db9fb096b4f13ea51f6ab23 100644
--- a/src/compiler/x64/code-generator-x64.cc
+++ b/src/compiler/x64/code-generator-x64.cc
@@ -16,6 +16,8 @@ namespace v8 {
 namespace internal {
 namespace compiler {
 
+#ifndef _WIN64
+
 #define __ masm()->
 
 
@@ -981,6 +983,8 @@ bool CodeGenerator::IsNopForSmiCodeInlining(Handle<Code> code, int start_pc,
 }
 
 #endif
+
+#endif
 }
 }
 }  // namespace v8::internal::compiler