The change in r180247 and the followup in r1802479 should be rolled out of trunk. The change makes sense to fix the crash reported in https://bugs.webkit.org/show_bug.cgi?id=141730 for branches, however the solution to fail the FTL compile but continue running is not comprehensive enough for general use on trunk.
Committed r180317: <http://trac.webkit.org/changeset/180317>