https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65979
--- Comment #23 from Kazumoto Kojima <kkojima at gcc dot gnu.org> --- Ouch. The peephole in problem was added at gcc-5 not at 4.9. The above patch should fix the original conftest.c issue, but debien 4.9-16 problem would be an another issue. Sorry for my confusion.
