Fix awesomeness in X64 assembler.
Fix awesomeness in X64 assembler.

R=ulan@chromium.org
TEST=mjsunit --turbo-types

Review URL: https://codereview.chromium.org/559123003

git-svn-id: f98b9d40cb02301bc76fa9e1b46ee668158567fd@23844 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh