The new approach uses one temp register instead of two on IA32. The ARM
instructions are modified so the input can be UseAtStart again.
Review URL: http://codereview.chromium.org/7274025

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8451 ce2b1a6d-e550-0410-aec6-3dcde31c8c00