Re: [FFmpeg-devel] [PATCH v2 07/13] avfilter/x86/f_ebur128: add x86 AVX implementation

From: Niklas Haas <ffmpeg@haasn.xyz>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH v2 07/13] avfilter/x86/f_ebur128: add x86 AVX implementation
Date: Mon, 16 Jun 2025 13:19:12 +0200
Message-ID: <20250616131912.GB10251@haasn.xyz> (raw)
In-Reply-To: <20250614011222.GI29660@pb2>

On Sat, 14 Jun 2025 03:12:22 +0200 Michael Niedermayer <michael@niedermayer.cc> wrote:
> Hi Niklas
>
> On Fri, Jun 13, 2025 at 06:37:50PM +0200, Niklas Haas wrote:
> > From: Niklas Haas <git@haasn.dev>
> >
> > Processes two channels in parallel, using 128-bit XMM registers.
> >
> > In theory, we could go up to YMM registers to process 4 channels, but this is
> > not a gain except for relatively high channel counts (e.g. 7.1), and also
> > complicates the sample load/store operations considerably.
> >
> > I decided to only add an AVX variant, since the C code is not substantially
> > slower enough to justify a separate function just for ancient CPUs.
> > ---
> >  libavfilter/f_ebur128.c          |  15 ++--
> >  libavfilter/f_ebur128.h          |  16 ++++
> >  libavfilter/x86/Makefile         |   2 +
> >  libavfilter/x86/f_ebur128.asm    | 142 +++++++++++++++++++++++++++++++
> >  libavfilter/x86/f_ebur128_init.c |  35 ++++++++
> >  5 files changed, 205 insertions(+), 5 deletions(-)
> >  create mode 100644 libavfilter/x86/f_ebur128.asm
> >  create mode 100644 libavfilter/x86/f_ebur128_init.c
>
> breaks x86-32

Fixed by enabling this only on 64 bit x86.

>
> src/libavfilter/x86/f_ebur128.asm:116: error: symbol `m8' undefined
> src/libavfilter/x86/f_ebur128.asm:118: error: symbol `m9' undefined
> src/libavfilter/x86/f_ebur128.asm:119: error: symbol `m10' undefined
> src/libavfilter/x86/f_ebur128.asm:120: error: symbol `m11' undefined
> src/libavfilter/x86/f_ebur128.asm:121: error: symbol `m12' undefined
> src/libavfilter/x86/f_ebur128.asm:122: error: symbol `m13' undefined
> src/libavfilter/x86/f_ebur128.asm:124: error: symbol `r7q' undefined
> src/libavfilter/x86/f_ebur128.asm:125: error: symbol `r8q' undefined
> src/libavfilter/x86/f_ebur128.asm:132: error: symbol `r7q' undefined
> src/libavfilter/x86/f_ebur128.asm:91: ... from macro `filter_channels' defined here
> src/libavfilter/x86/f_ebur128.asm:57: ... from macro `FILTER' defined here
> src//libavutil/x86/x86inc.asm:1654: ... from macro `movsd' defined here
> src//libavutil/x86/x86inc.asm:1501: ... from macro `RUN_AVX_INSTR' defined here
> src/libavfilter/x86/f_ebur128.asm:132: error: symbol `r7q' undefined
> src/libavfilter/x86/f_ebur128.asm:91: ... from macro `filter_channels' defined here
> src/libavfilter/x86/f_ebur128.asm:58: ... from macro `FILTER' defined here
> src//libavutil/x86/x86inc.asm:1654: ... from macro `movsd' defined here
> src//libavutil/x86/x86inc.asm:1501: ... from macro `RUN_AVX_INSTR' defined here
> src/libavfilter/x86/f_ebur128.asm:132: error: symbol `r7q' undefined
> ...
>
> [...]
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> Concerning the gods, I have no means of knowing whether they exist or not
> or of what sort they may be, because of the obscurity of the subject, and
> the brevity of human life -- Protagoras
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