Replace OS::MemCopy with OS::MemMove (just as fast but more flexible).

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 9b648a33704ab45b09ea7a743c807de807b1894c..4c65735f24e8c7736401988464d2bef079673fe1 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -118,7 +118,7 @@ void LCodeGen::Comment(const char* format, ...) {
   // issues when the stack allocated buffer goes out of scope.
   int length = builder.position();
   Vector<char> copy = Vector<char>::New(length + 1);
-  memcpy(copy.start(), builder.Finalize(), copy.length());
+  OS::MemCopy(copy.start(), builder.Finalize(), copy.length());
   masm()->RecordComment(copy.start());
 }