[Bug rtl-optimization/98555] Functions optimized to zero length break function pointer inequality

[rlcamp.pdx at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98555

--- Comment #2 from Campbell <rlcamp.pdx at gmail dot com> ---
> Did you actually run into this for a relevant case?

Yes. The relevant use case is where a sentinel value is needed that has
function pointer type, as function pointers are not interchangeable with other
types of pointers.