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From: "Dave.Love at manchester dot ac.uk" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/103008] poor inlined builtin_fmod on x86_64
Date: Sun, 13 Feb 2022 21:00:37 +0000	[thread overview]
Message-ID: <bug-103008-4-feR47O87Qb@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-103008-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103008

--- Comment #15 from Dave.Love at manchester dot ac.uk ---
"ubizjak at gmail dot com" <gcc-bugzilla@gcc.gnu.org> writes:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103008
>
> --- Comment #14 from Uroš Bizjak <ubizjak at gmail dot com> ---
> Created attachment 52428
>   --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52428&action=edit
> Proposed patch
>
> The attached patch implements:
>
> fmod (a, p) = a - trunc (a/p) * p
> drem (a, p) = a - roundeven (a/p) * p
>
> using SSE4 round instruction (and uses fnma when available).
>
> Timings with Polyhedron ac.f90 on IvyBridge-E, Fedora-34, glibc 2.33-21.fc34
>
> -Ofast:
>        6,150082000 seconds user
>
> -Ofast -mno-80387:
>       18,354654000 seconds user
>
> -Ofast -msse4:
>        5,722511000 seconds user

I realize I never made a Fortran bug report about this, and should do.
(I think the gfortran intrinsic should avoid fmod anyway, and just use
the standard's arithmetical definition of MOD without having to bother
about errors.)

  parent reply	other threads:[~2022-02-13 21:00 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-30 18:51 [Bug target/103008] New: " fx at gnu dot org
2021-10-30 18:52 ` [Bug target/103008] " fx at gnu dot org
2021-10-30 18:55 ` fx at gnu dot org
2021-10-30 18:56 ` fx at gnu dot org
2021-10-30 20:15 ` fx at gnu dot org
2021-10-30 20:39 ` anlauf at gcc dot gnu.org
2021-10-31 20:05 ` ubizjak at gmail dot com
2021-11-01  8:23 ` ubizjak at gmail dot com
2022-02-10 14:18 ` rguenth at gcc dot gnu.org
2022-02-10 14:22 ` rguenth at gcc dot gnu.org
2022-02-10 18:09 ` ubizjak at gmail dot com
2022-02-10 20:50 ` joseph at codesourcery dot com
2022-02-11  7:59 ` rguenth at gcc dot gnu.org
2022-02-11 15:47 ` ubizjak at gmail dot com
2022-02-12 22:07 ` ubizjak at gmail dot com
2022-02-13 21:00 ` Dave.Love at manchester dot ac.uk [this message]
2022-02-14  7:12 ` rguenther at suse dot de
2022-02-14  7:35 ` rguenth at gcc dot gnu.org

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