[Bug rtl-optimization/120004] __builtin_unreachable/noreturn should not fall through to another function

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120004

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
unreachable() is in some cases added to make the CFG valid - in the past we had
a return in such places but unreachable seemed to be a better fit.

For asm() we'd need "[[noreturn]]" (or rather [[return]]?).