http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56888
--- Comment #2 from Mikael Pettersson <mikpe at it dot uu.se> 2013-04-09 09:59:20 UTC --- Started with Richard Biener's http://gcc.gnu.org/r188261 aka PR53081 fix, which added or improved memcpy recognition. I'm guess the new code fails to check for whatever option is supposed to disable this sort of transformation.
