Without it, we won't be able to make this loop evaporate, because the CFA will execute the "i++" basic block and pollute i. for (var i = 0; i < 1; ++i) doThings(i); Patch forthcoming, though I foresee this generating some bugs, so though the patch is simple it'll probably take a while to fully bake.
Created attachment 142166 [details] work in progress
Created attachment 142326 [details] more
Created attachment 142346 [details] the patch Yup it works.
Landed in http://trac.webkit.org/changeset/117370
Merged in http://trac.webkit.org/changeset/118309