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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/110891] [14 Regression] Dead Code Elimination
 Regression since r14-2674-gd0de3bf9175
Date: Sat, 26 Aug 2023 00:00:35 +0000
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X-Bugzilla-Component: tree-optimization
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110891

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
One thing I noticed (I don't know if causes the missed optimization) is tha=
t we
have before PRE:
```
  <bb 4> [local count: 1073531371]:
  if (a.0_1 !=3D 0)
    goto <bb 6>; [50.00%]
  else
    goto <bb 5>; [50.00%]

  <bb 5> [local count: 536765686]:
  if (_28 =3D=3D &d)
    goto <bb 9>; [30.00%]
  else
    goto <bb 7>; [70.00%]

  <bb 6> [local count: 536765685]:
  if (_28 =3D=3D &d)
    goto <bb 9>; [30.00%]
  else
    goto <bb 7>; [70.00%]
```
Which obvious should just be `if (_28 =3D=3D &d) goto bb9; else goto bb7;` =
and not
check `a.0_1` at all.

I tried a reduced testcase but PRE optimizes it:
```
int g();
int h();

int j, l;

int f(int a, int *b)
{
        if (a =3D=3D 0)
        {
                if (b =3D=3D &j) goto L9; else goto L7;
        }
        else
        {
                if (b =3D=3D &j) goto L9; else goto L7;
        }
L7: return g();
L9: return h();
}
```=