https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78546
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> --- But e.g. typedef unsigned __int128 u128; u128 b; int main () { u128 x = ((u128) ~0x7fffffffffffffff) - b; u128 y = 1 - x; if (y != 0x8000000000000001) __builtin_abort(); return 0; } is miscompiled already before that, bisecting again.