It addresses the problem of 'cmp' instruction that has the side-effect that ip register
shouldn't be used as rn.

Review URL: http://codereview.chromium.org/11323

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@810 ce2b1a6d-e550-0410-aec6-3dcde31c8c00