[Bug c/110249] __builtin_unreachable helps optimisation at -O1 but not at -O2

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110249

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
We could pattern-match this to

 p = __builtin_assume_aligned (p, 8);

which is btw the better way to write this.