http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21998
--- Comment #5 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-13 11:28:45 UTC --- We have two related flags here, -ftree-loop-if-convert-stores, and --param allow-store-data-races. We can adjust the former to honor the latter if specified and then eventually vectorize this, too.