https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88854
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> --- GCC 5 doesn't see the CSE opportunity because it doesn't process the unused load and the translation code is not up-to-speed. Then DOM figures out the redundant store it sees them adjacent. So I wouldn't really call this a regression.