Fix mips64 and presumably x87.

BUG=
R=mstarzinger@chromium.org, sigurds@chromium.org

Review URL: https://codereview.chromium.org/679433004

Patch from Paul Lind <paul.lind@imgtec.com>.

Cr-Commit-Position: refs/heads/master@{#24897}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24897 ce2b1a6d-e550-0410-aec6-3dcde31c8c00