http://code.google.com/p/v8/source/detail?r=4503 added this functionality to ia32.

Review URL: http://codereview.chromium.org/1694018

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4549 ce2b1a6d-e550-0410-aec6-3dcde31c8c00