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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/110919] [14 Regression] Dead Code Elimination
 Regression at -O3 since r14-1691-gbc5a2c2e793
Date: Sun, 20 Aug 2023 09:11:57 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: missed-optimization
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110919

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The first change we get is threadfull1 where there is an extra jump threadi=
ng.
And then phiopt2 changes:
  <bb 3> [local count: 719407024]:
  if (l_15(D) !=3D 0)
    goto <bb 6>; [50.00%]
  else
    goto <bb 7>; [50.00%]
into:
  <bb 3> [local count: 719407024]:
  _17 =3D l_15(D) =3D=3D 0;
  _36 =3D (int) _17;

And then DOM2 does not do jump threading along:
  <bb 6> [local count: 628138968]:
  # iftmp.1_8 =3D PHI <_36(3), 0(5)>


As I mentioned in comment #2 we don't see that:
  _19 =3D _6 =3D=3D iftmp.1_8;
  _3 =3D iftmp.1_8 ^ 1;
  _21 =3D (_Bool) _3;
  _22 =3D _19 & _21;
  _23 =3D _6 !=3D 0;
  _5 =3D _22 & _23;

is always 0.=