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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/111294] [14 Regression] Missed Dead Code
 Elimination since  r14-573-g69f1a8af45d
Date: Tue, 05 Sep 2023 21:02:00 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111294

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> In .optimized we have:
>   <bb 4> [local count: 118111600]:
>   # _31 =3D PHI <5(2), 0(3)>
>   _6 =3D (int) a.9_28;
>   _8 =3D _31 <=3D 3;
>   _9 =3D (int) _8;
>   if (_6 !=3D _9)
>     goto <bb 5>; [66.00%]
>   else
>     goto <bb 6>; [34.00%]
>=20
> Except nothing optimizes _8 into the phi post pre (note _31 is only used =
in
> the definition of _8 even).

But optimizing that does not help here.

Someone who understands jump threading should look into this.=