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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/107880] bool tautology missed optimisation
Date: Sat, 26 Nov 2022 18:11:12 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107880

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=3D101807

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
One way of fixing this is first transform:
  _9 =3D ~a_4(D);
  _10 =3D b_3(D) | _9;
Into:

_10 =3D a_4(D) <=3D b_3(D);

And then we have:
  _8 =3D b_3(D) >=3D a_4(D);
  _7 =3D b_3(D) <=3D a_4(D);
  _1 =3D _7 =3D=3D _8;
  _2 =3D b_3(D) =3D=3D a_4(D);
  _6 =3D _1 =3D=3D _2;

But  _1 is true iff a_4(D) =3D=3D b_3(D) .
Let me file that second one as we don't optimize it also for int.=