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From: "amonakov at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/108922] fmod() 13x slowdown in gcc4.9 dropping "fprem" and calling fmod()
Date: Mon, 27 Feb 2023 08:17:06 +0000	[thread overview]
Message-ID: <bug-108922-4-wABmcVpsyI@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-108922-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108922

--- Comment #15 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
That is the fancy-error-handling path that is reached under _LIB_VERSION !=
_IEEE_. Before glibc-2.27, linking with -lieee would set _LIB_VERSION = _IEEE_,
and then glibc would use the fprem[1] instruction without any special-casing.

musl libc does not implement errno setting for math functions, and always uses
fprem directly; likewise for Apple libm:

https://github.com/apple-oss-distributions/Libm/blob/17a5f9daa3f5679f7536b26f133b40cc078753c3/Source/Intel/fmod.s

  parent reply	other threads:[~2023-02-27  8:17 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-24 12:22 [Bug target/108922] New: fmod() 13x slowdown in gcc 4.8->4.9 " jkratochvil at azul dot com
2023-02-25  2:41 ` [Bug target/108922] fmod() 13x slowdown in gcc4.9 " pinskia at gcc dot gnu.org
2023-02-25  2:47 ` pinskia at gcc dot gnu.org
2023-02-25  9:58 ` amonakov at gcc dot gnu.org
2023-02-25 10:24 ` amonakov at gcc dot gnu.org
2023-02-25 10:30 ` ubizjak at gmail dot com
2023-02-25 10:49 ` ubizjak at gmail dot com
2023-02-25 10:56 ` amonakov at gcc dot gnu.org
2023-02-26  6:39 ` jkratochvil at azul dot com
2023-02-26  8:01 ` amonakov at gcc dot gnu.org
2023-02-26 11:16 ` jkratochvil at azul dot com
2023-02-26 21:28 ` ubizjak at gmail dot com
2023-02-26 21:32 ` ubizjak at gmail dot com
2023-02-26 23:36 ` jkratochvil at azul dot com
2023-02-27  7:13 ` ubizjak at gmail dot com
2023-02-27  8:17 ` amonakov at gcc dot gnu.org [this message]
2023-02-27  8:31 ` jakub at gcc dot gnu.org
2023-02-27  9:10 ` ubizjak at gmail dot com
2023-02-27  9:17 ` jakub at gcc dot gnu.org
2023-02-27  9:32 ` amonakov at gcc dot gnu.org
2023-02-27  9:33 ` ubizjak at gmail dot com
2023-02-27  9:49 ` ubizjak at gmail dot com
2023-02-27 10:01 ` amonakov at gcc dot gnu.org
2023-02-27 10:10 ` jkratochvil at azul dot com
2023-02-27 10:13 ` jkratochvil at azul dot com
2023-02-27 10:16 ` jakub at gcc dot gnu.org
2023-02-27 10:31 ` ubizjak at gmail dot com
2023-02-27 10:41 ` jakub at gcc dot gnu.org
2023-02-27 10:46 ` ubizjak at gmail dot com
2023-02-27 10:47 ` jakub at gcc dot gnu.org
2023-02-27 10:58 ` ubizjak at gmail dot com
2023-02-27 21:11 ` cvs-commit at gcc dot gnu.org
2023-02-27 21:13 ` ubizjak at gmail dot com
2023-02-28 16:51 ` hjl.tools at gmail dot com

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