https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86214
--- Comment #6 from Steinar H. Gunderson <steinar+gcc at gunderson dot no> --- I wouldn't be surprised if everything is really over-reduced, and that GCC 7 just happens not to hit this by luck. I'll be making a checkout of the public git repository and try to reproduce there, so that I can give you an unreduced version.