Intrinsic handling involves making the assumption that we're calling the intrinsic that we thought we were going to call. But that involves a speculation, which may, and almost always does, appear after the operands are computed. Hence the computation of the operands must assume that they may escape and be used arbitrarily, in the case that we don't call the intrinsic we thought we were calling (because we exited).
Created attachment 181732 [details] the patch
Comment on attachment 181732 [details] the patch r=me
Landed in http://trac.webkit.org/changeset/139098