https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80837
--- Comment #2 from Peter Cordes <peter at cordes dot ca> --- (In reply to Richard Biener from comment #1) > GCC 8 generates a __atomic_load_16 call for me while GCC 6 does > > lock cmpxchg16b (%rdi) That's expected. See https://gcc.gnu.org/ml/gcc-patches/2017-01/msg02344.html for the reason. (Apparently the plan is for gcc7 to call libatomic, to make it possible to change the implementation sooner in the future if that's deemed appropriate, even in ways that breaks compat with code that inlines lock cmpxchg16b.) The bug here is that gcc7.1.0 goes berserk after the library call, but gcc8 doesn't. I haven't tested on any other gcc7 versions.
