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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/103008] poor inlined builtin_fmod on x86_64
Date: Mon, 14 Feb 2022 07:12:58 +0000 [thread overview]
Message-ID: <bug-103008-4-iASE4FtXUJ@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 #16 from rguenther at suse dot de <rguenther at suse dot de> ---
On Fri, 11 Feb 2022, ubizjak at gmail dot com wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103008
>
> --- Comment #13 from Uroš Bizjak <ubizjak at gmail dot com> ---
> (In reply to Richard Biener from comment #12)
> > Just as data-point on znver2 Uros testcase shows
> >
> > rguenther@ryzen:/tmp> gcc-11 t.c -Ofast -lm -march=znver2
> > rguenther@ryzen:/tmp> numactl --physcpubind=3 /usr/bin/time ./a.out
> > 19.18user 0.00system 0:19.18elapsed 99%CPU (0avgtext+0avgdata
> > 1528maxresident)k
> > 0inputs+0outputs (0major+76minor)pagefaults 0swaps
> > rguenther@ryzen:/tmp> gcc-11 t.c -Ofast -lm -march=znver2 -fno-builtin-fmod
>
> You should use -fno-builtin-fmodf in the above compile flags.
Oops, yes. Then the glibc version is
22.53user 0.00system 0:22.53elapsed 99%CPU (0avgtext+0avgdata
1600maxresident)k
0inputs+0outputs (0major+77minor)pagefaults 0swaps
so indeed for float the x87 inline version is faster when benchmarked
this way. For double it's
19.31user 0.00system 0:19.31elapsed 99%CPU (0avgtext+0avgdata
1536maxresident)k
0inputs+0outputs (0major+76minor)pagefaults 0swaps
vs.
18.47user 0.00system 0:18.47elapsed 99%CPU (0avgtext+0avgdata
1600maxresident)k
0inputs+0outputs (0major+77minor)pagefaults 0swaps
so glibc is a bit faster here while the x87 version is of course
similar. Avoiding the libcall can of course avoid spilling SSE
regs around the call.
So what remains is really the special case in blender doing
fmod (x, 1.) which can eventually be optimized with SSE4.
next prev parent reply other threads:[~2022-02-14 7:12 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
2022-02-14 7:12 ` rguenther at suse dot de [this message]
2022-02-14 7:35 ` rguenth at gcc dot gnu.org
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