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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 16:41:31 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D90693

--- Comment #13 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #12)
> (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);
> > }
>=20
>=20
> 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 be=
en
> done yet.

Well that also should be transformed into `__builtin_popcount(a) <=3D 1` wh=
ich
then gets expanded into `(v & (v - 1)) =3D=3D 0`. I will be handling both o=
f those
via PR 94787 .=