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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/108360] [13/14 Regression] Dead Code
 Elimination Regression at -Os since r13-2048-g418b71c0d535bf
Date: Wed, 09 Aug 2023 01:25:35 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108360

--- Comment #11 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I have a patch which gets us to:
```
  short int b.2_1;
...
  b.2_1 =3D b;
  _2 =3D b.2_1 <=3D 0;
  _4 =3D (char) _2;
  f =3D _4;
  f.5_5 =3D (unsigned char) _2;
  _6 =3D f.5_5 << 4;
  e =3D _6;
  _19 =3D b.2_1 <=3D 0;
  _7 =3D (short int) _19;
  _21 =3D _7 << 4;
  if (b.2_1 =3D=3D _21)

```
Which is closer.

```
int f(short b)
{
  auto _19 =3D b <=3D 0;
  auto _7 =3D (short int) _19;
  auto _21 =3D _7 << 4;
  return b =3D=3D _21;
}
```
is just `return false;` as _21's range is `[0,4]` but it is only 0 when `b =
> 0`

And then maybe:
(simplify
 (eq:c @0 (rshift (convert (le @0 integer_zero_p)) INTEGER_CST@1))
 (if (wi::to_wide(@1) < element_precision (TREE_TYPE (@0)) - 1)
  ( { false_value; } ))

Is this worth this pattern, I don't know ...=