When the CFA proves code to be unreachable, we are stuck in a bit of a conundrum. The code must still be known to other parts of the compiler because of OSR exit liveness issues, so it cannot be simply jettisoned. But we shouldn't be spending time generating that code, and we shouldn't be allowing OSR entry into that code.
Created attachment 144410 [details] the patch
Created attachment 144425 [details] the patch Cleaned up constant folding a bit more.
Landed in http://trac.webkit.org/changeset/118715