[Bug tree-optimization/94566] conversion between std::strong_ordering and int

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94566

--- Comment #11 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Oliver Schönrock from comment #10)
> I agree the switch optimisation is better, but...
> 
>  shouldn't std::bit_cast prevent incorrect casting with different underlying
> implementaion? (ie if the size doesn't match, and the size could be deduced
> with TMP) 

The size can be deduced, yes.  What the bits actually mean can't be.

> and "unordered value" doesn't apply to std::strong_ordering?

Sure, but this PR isn't just about strong_ordering, same problem applies for
partial_ordering.
And actually not just those, but any case of some set of enumerators or macros
where you don't know the values exactly and mapping them to or from a set of
integer constants, ideally with 1:1 mapping but not guaranteed that way.