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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/112457] Possible better vectorization of different reduction min/max reduction
Date: Thu, 09 Nov 2023 12:45:54 +0000	[thread overview]
Message-ID: <bug-112457-4-LYDJ7J2sDb@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-112457-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112457

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c                           |tree-optimization
             Blocks|                            |53947

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Well, this is because MAX_EXPR detection fails when store motion inserts flags
(the max = max is elided) to avoid store-data races.  Also when using
-Ofast we avoid this but then the next phiopt comes too late to discover
MAX after store motion is applied.

The more practical example is

int foo2 (int max, int n, int * __restrict a)
{
  for (int i = 0; i < n; ++i)
    if (max < a[i]) {
        max = a[i];
    }
  return max;
}

and that's handled OK.  For your second example, index reduction, there's
already bugreports.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53947
[Bug 53947] [meta-bug] vectorizer missed-optimizations

  parent reply	other threads:[~2023-11-09 12:45 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-11-09 12:27 [Bug c/112457] New: " juzhe.zhong at rivai dot ai
2023-11-09 12:29 ` [Bug c/112457] " juzhe.zhong at rivai dot ai
2023-11-09 12:45 ` rguenth at gcc dot gnu.org [this message]
2024-01-02  8:58 ` [Bug tree-optimization/112457] " juzhe.zhong at rivai dot ai
2024-01-02 16:03 ` xry111 at gcc dot gnu.org
2024-01-08  9:00 ` rguenth at gcc dot gnu.org

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