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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/90693] Missing popcount simplifications
Date: Mon, 04 Mar 2024 07:42:22 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D90693

--- 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 =3D=3D 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.=