[Bug tree-optimization/90693] Missing popcount simplifications

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90693

--- Comment #12 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Piotr Siupa from comment #11)
> However, I've noticed that:
> bool foo(unsigned x)
> {
>     if (x == 0)
>         return true;
>     else
>         return std::has_single_bit(x);
> }


Oh that is because expand does not use flow sensitive ranges/non-zero bits
there. There is talk about adding the ability for that but nothing has been
done yet.