https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71648
--- Comment #5 from Bill Schmidt <wschmidt at gcc dot gnu.org> --- This appears to be fixed on trunk -- between David and me we've tested this on AIX 32- and 64-bit, PPC64LE on P8, and PPC64 on P7. We'll need to bisect and see what fixed the problem and work on a backport for GCC 6.
