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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	[thread overview]
Message-ID: <bug-108360-4-t1dZ0e81Ap@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-108360-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108360

--- 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 = b;
  _2 = b.2_1 <= 0;
  _4 = (char) _2;
  f = _4;
  f.5_5 = (unsigned char) _2;
  _6 = f.5_5 << 4;
  e = _6;
  _19 = b.2_1 <= 0;
  _7 = (short int) _19;
  _21 = _7 << 4;
  if (b.2_1 == _21)

```
Which is closer.

```
int f(short b)
{
  auto _19 = b <= 0;
  auto _7 = (short int) _19;
  auto _21 = _7 << 4;
  return b == _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 ...

  parent reply	other threads:[~2023-08-09  1:25 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-10 13:10 [Bug tree-optimization/108360] New: Dead Code Elimination Regression at -Os (trunk vs. 12.2.0) yann at ywg dot ch
2023-01-10 14:48 ` [Bug tree-optimization/108360] [13 Regression] Dead Code Elimination Regression at -Os since r13-2048-g418b71c0d535bf marxin at gcc dot gnu.org
2023-01-10 17:00 ` jakub at gcc dot gnu.org
2023-01-10 17:32 ` jakub at gcc dot gnu.org
2023-01-10 17:45 ` jakub at gcc dot gnu.org
2023-01-10 19:18 ` amacleod at redhat dot com
2023-01-10 19:26 ` amacleod at redhat dot com
2023-01-10 19:28 ` amacleod at redhat dot com
2023-03-27 11:37 ` rguenth at gcc dot gnu.org
2023-04-08 14:37 ` law at gcc dot gnu.org
2023-04-26  6:57 ` [Bug tree-optimization/108360] [13/14 " rguenth at gcc dot gnu.org
2023-07-27  9:25 ` rguenth at gcc dot gnu.org
2023-08-07  8:53 ` pinskia at gcc dot gnu.org
2023-08-09  1:25 ` pinskia at gcc dot gnu.org [this message]
2024-05-21  9:13 ` [Bug tree-optimization/108360] [13/14/15 " jakub at gcc dot gnu.org

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