From: "Rémi Denis-Courmont" <remi@remlab.net>
To: FFmpeg development discussions and patches
<ffmpeg-devel@ffmpeg.org>, Paul B Mahol <onemda@gmail.com>
Subject: Re: [FFmpeg-devel] [PATCH] af_afir: RISC-V V fcmul_add
Date: Tue, 26 Sep 2023 21:44:32 +0300
Message-ID: <1820851.0qsxitF44R@basile.remlab.net> (raw)
In-Reply-To: <CAPYw7P5y5DMWnMo9co3HBTDbfoXX5Cxxs_K5y08BWBdbV2wo8w@mail.gmail.com>
Le tiistaina 26. syyskuuta 2023, 21.40.12 EEST Paul B Mahol a écrit :
> On Tue, Sep 26, 2023 at 8:35 PM Rémi Denis-Courmont <remi@remlab.net> wrote:
> > Le tiistaina 26. syyskuuta 2023, 12.24.58 EEST flow gg a écrit :
> > > benchmark:
> > > fcmul_add_c: 19.7
> > > fcmul_add_rvv_f32: 6.7
> >
> > Nit: please pad mnemonics to at least 8 columns for consistency.
> >
> > I'm a bit surprised that the performance improves this much, considering
> > that
> > the C910 is notoriously bad at both segmented strided loads. It might be
> > that
> > the C versions is just very bad due to lack of aliasing optimisations. Oh
> > well.
>
> What you mean exactly that C version is missing?
The C version does not have any restrict qualifier. This potentially prevents
the C compiler from unrolling. Adding the keyword can improve performance
gains of 20-30% on RISC-V scalar floating point.
That said, sometimes you can't validly use restrict, and you simply can't tell
the C compiler how to optimise properly. In those cases, even scalar floating
point optimisations improve performance.
--
Rémi Denis-Courmont
http://www.remlab.net/
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next prev parent reply other threads:[~2023-09-26 18:44 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-26 9:24 flow gg
2023-09-26 18:34 ` Rémi Denis-Courmont
2023-09-26 18:40 ` Paul B Mahol
2023-09-26 18:44 ` Rémi Denis-Courmont [this message]
2023-09-27 1:47 ` flow gg
2023-09-27 16:01 ` Rémi Denis-Courmont
2023-09-27 16:27 ` Rémi Denis-Courmont
2023-09-26 18:50 ` Rémi Denis-Courmont
2023-09-27 16:41 ` Rémi Denis-Courmont
2023-09-28 5:45 ` flow gg
2023-09-28 13:33 ` Rémi Denis-Courmont
2023-11-13 9:43 ` flow gg
2023-11-13 15:35 ` Rémi Denis-Courmont
2023-11-13 16:01 ` Paul B Mahol
2023-11-15 8:57 ` flow gg
2023-11-15 8:59 ` flow gg
2023-11-15 15:05 ` Rémi Denis-Courmont
2023-11-15 23:04 ` flow gg
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