and the value can share a register. We need to remove this aliasing
before modifying the registers.

I haven't managed to generate a stand-alon test case for this
yet. I'll do that as a separate change. This was found while loading
Wave.

Review URL: http://codereview.chromium.org/3039025

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5127 ce2b1a6d-e550-0410-aec6-3dcde31c8c00