Will be useful for more rigorously choosing which locals to hoist checks over and unbox (https://bugs.webkit.org/show_bug.cgi?id=110433).
Created attachment 189845 [details] WRONG PATCH
Created attachment 189846 [details] the patch
Comment on attachment 189846 [details] the patch r=me
Landed in http://trac.webkit.org/changeset/143817