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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/29333] Jump threading getting in the way of
 PHI-OPT
Date: Tue, 16 Nov 2021 02:15:26 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D29333

--- Comment #10 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to rsandifo@gcc.gnu.org from comment #8)
> This may be worth filing as another PR (let me know if you
> think I should), but another case of VRP stymieing phiopt is:
>=20
> void bar (int);
> void
> foo (int a, int b)
> {
>   if (!b)
>     bar (1);
>   else
>     {
>       int c;
>       if (a)
>         c =3D a;
>       else
>         c =3D 0;
>       if (c =3D=3D b)
>         bar (2);
>     }
> }

This was testcase was fixed on trunk by a combo of patches to tree-ssa-phio=
pt.c
and match.pd (r12-2041, r12-2040, r12-2039, and r12-1152 [there might have =
been
a few more required which I missed]) which allows early phiopt to change if=
 (a)
c =3D a else c =3D 0; to just c =3D a.=