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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/113583] Main loop in 519.lbm not vectorized.
Date: Wed, 07 Feb 2024 08:04:29 +0000 [thread overview]
Message-ID: <bug-113583-4-fM4UnFXTwg@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-113583-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113583
--- Comment #14 from rguenther at suse dot de <rguenther at suse dot de> ---
On Wed, 7 Feb 2024, juzhe.zhong at rivai dot ai wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113583
>
> --- Comment #13 from JuzheZhong <juzhe.zhong at rivai dot ai> ---
> Ok. I found the optimized tree:
>
>
> _5 = 3.33333333333333314829616256247390992939472198486328125e-1 - _4;
> _8 = .FMA (_5, 1.229999999999999982236431605997495353221893310546875e-1, _4);
>
> Let CST0 = 3.33333333333333314829616256247390992939472198486328125e-1,
> CST1 = 1.229999999999999982236431605997495353221893310546875e-1
>
> The expression is equivalent to the following:
>
> _5 = CST0 - _4;
> _8 = _5 * CST1 + 4;
>
> That is:
>
> _8 = (CST0 - _4) * CST1 + 4;
>
> So, We should be able to re-associate it like Clang:
>
> _8 = CST0 * CST1 - _4 * CST1 + 4; ---> _8 = CST0 * CST1 + _4 * (1 - CST1);
>
> Since both CST0 * CST1 and 1 - CST1 can be pre-computed during compilation
> time.
>
> Let say CST2 = CST0 * CST1, CST3 = 1 - CST1, then we can re-associate as Clang:
>
> _8 = FMA (_4, CST3, CST2).
>
> Any suggestions for this re-association ? Is match.pd the right place to do it
> ?
You need to look at the IL before we do .FMA forming, specifically
before/after the late reassoc pass. There pass applying match.pd
patterns everywhere is forwprop.
I also wonder which compilation flags you are using (note clang
has different defaults for example for -ftrapping-math)
next prev parent reply other threads:[~2024-02-07 8:04 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-24 14:21 [Bug tree-optimization/113583] New: " rdapp at gcc dot gnu.org
2024-01-24 14:42 ` [Bug tree-optimization/113583] " juzhe.zhong at rivai dot ai
2024-01-24 14:44 ` rdapp at gcc dot gnu.org
2024-01-24 15:00 ` juzhe.zhong at rivai dot ai
2024-01-25 3:06 ` juzhe.zhong at rivai dot ai
2024-01-25 3:13 ` juzhe.zhong at rivai dot ai
2024-01-25 5:41 ` pinskia at gcc dot gnu.org
2024-01-25 9:05 ` rguenther at suse dot de
2024-01-25 9:16 ` juzhe.zhong at rivai dot ai
2024-01-25 9:34 ` rguenth at gcc dot gnu.org
2024-01-26 9:50 ` rdapp at gcc dot gnu.org
2024-01-26 10:21 ` rguenther at suse dot de
2024-02-05 6:59 ` juzhe.zhong at rivai dot ai
2024-02-07 3:39 ` juzhe.zhong at rivai dot ai
2024-02-07 7:48 ` juzhe.zhong at rivai dot ai
2024-02-07 8:04 ` rguenther at suse dot de [this message]
2024-02-07 8:08 ` juzhe.zhong at rivai dot ai
2024-02-07 8:13 ` juzhe.zhong at rivai dot ai
2024-02-07 10:24 ` rguenther at suse dot de
2024-05-13 14:17 ` rdapp at gcc dot gnu.org
2024-05-16 12:41 ` rguenth at gcc dot gnu.org
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