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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/110992] [13/14 Regression] missed VRP
 optimization due to transformation of `a & -zero_one_valued_p` into `a *
 zero_one_valued_p`
Date: Fri, 15 Sep 2023 03:19:01 +0000
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X-Bugzilla-Component: tree-optimization
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110992

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|14.0                        |13.3
            Summary|[14 Regression] Dead Code   |[13/14 Regression] missed
                   |Elimination Regression at   |VRP optimization due to
                   |-O3 since                   |transformation of `a &
                   |r14-1654-g7ceed7e3e29       |-zero_one_valued_p` into `a
                   |                            |* zero_one_valued_p`

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Hmm, I think this is a ranger issue really.
Take:
```
int f(unsigned b, short c)
{
  int bt =3D b;
  int bt1 =3D bt;
  int t =3D bt1 & -(c!=3D0);
 // int t =3D bt1 * (c!=3D0);

  if (!t) return 0;
  foo(bt =3D=3D 0);
  return 0;
}
```

That `bt =3D=3D 0` should be figured out that is 0 there. We could figure t=
hat out
in GCC 12 even. But in GCC 13+ we could not.

That is traced back to r13-793-g8fb94fc6097c but really the ranger should
figure out if you have a*b !=3D 0, then both a and b should be non-zero ...
But currently that is not support ....
It looks like we only handle `a & b` that way ...=