This is a subset of a CL reviewed earlier(http://codereview.chromium.org/551093).
The register usage optimisation part has been reviewed and submitted separately.
Two fast cases supported: HeapNumber operands and String operands for ADD.


Review URL: http://codereview.chromium.org/553117

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3988 ce2b1a6d-e550-0410-aec6-3dcde31c8c00