This is a port of the IA-32 version from r3400 (http://code.google.com/p/v8/source/detail?r=3400). In the X64 version the additional registers are used to avoid loading the instance type and arguments several times.
Review URL: http://codereview.chromium.org/460109

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3434 ce2b1a6d-e550-0410-aec6-3dcde31c8c00