On 7/27/2022 10:02 PM, Soft Works wrote:
-----Original Message-----
From: ffmpeg-devel<ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of
Hendrik Leppkes
Sent: Wednesday, July 27, 2022 10:42 PM
To: FFmpeg development discussions and patches <ffmpeg-
de...@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH] enable auto vectorization for gcc
7 and higher
On Wed, Jul 27, 2022 at 7:39 PM James Almer<jamr...@gmail.com>
wrote:
On 7/27/2022 2:34 PM, Swinney, Jonathan wrote:
I recognize that this patch is going to be somewhat
controversial. I'm submitting it mostly to see what the opinions are
and evaluate options. I am working on improving performance for
aarch64. On that architecture, there are fewer hand written assembly
implementations of hot functions than there are for x86_64 and
allowing gcc to auto-vectorize yields noticeable improvements.
Gcc vectorization has improved recently and it hasn't been
evaluated on the mailing list for a few years. This is the latest
discussion I found in my searches:
http://ffmpeg.org/pipermail/ffmpeg-devel/2016-May/193977.html
Every time this was done, it was inevitably reverted after
complains and
crash reports started piling up because gcc can't really handle all
the
inline code our codebase has, among other things.
No need to wait for issues, I just tested, and the same issues still
persist that have existed for years with GCC now. They don't seem to
care to make it compatible with inline asm, which might be fair
enough, but it means it just can't work here.
In file included from libavcodec/cabac_functions.h:49,
from libavcodec/h264_cabac.c:36:
libavcodec/h264_cabac.c: In function 'ff_h264_decode_mb_cabac':
libavcodec/x86/cabac.h:199:5: error: 'asm' operand has impossible
constraints
I wonder why it doesn't fail when I try the same on MINGW32:
gcc -I. -Isrc/ -D_FORTIFY_SOURCE=0 -D__USE_MINGW_ANSI_STDIO=1 -D_ISOC99_SOURCE
-D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -U__STRICT_ANSI__
-D__USE_MINGW_ANSI_STDIO=1 -D__printf__=__gnu_printf__ -D_POSIX_C_SOURCE=200112
-D_XOPEN_SOURCE=600 -DOPJ_STATIC -DZLIB_CONST -DHAVE_AV_CONFIG_H
-DBUILDING_avcodec -mthreads -DLIBTWOLAME_STATIC -std=c11
-IV:/ffbuild/mas/local32/include -IV:/ffbuild/mas/msys64/mingw32/include
-I/mingw32/include -IF:/ffbuild/mas/local32/include -DLIBARCHIVE_STATIC
-Wdeclaration-after-statement -Wall -Wdisabled-optimization -Wpointer-arith
-Wredundant-decls -Wwrite-strings -Wtype-limits -Wundef -Wmissing-prototypes
-Wstrict-prototypes -Wempty-body -Wno-parentheses -Wno-switch
-Wno-format-zero-length -Wno-pointer-sign -Wno-unused-const-variable
-Wno-bool-operation -Wno-char-subscripts -O3 -Werror=format-security
-Werror=implicit-function-declaration -Werror=missing-prototypes
-Werror=return-type -Werror=vla -Wformat -fdiagnostics-color=auto
-Wno-maybe-uninitialized
-
ftree-vectorize -MMD -MF libavcodec/h264_cabac.d -MT libavcodec/h264_cabac.o
-c -o libavcodec/h264_cabac.o src/libavcodec/h264_cabac.c
You didn't set CPU to haswell (Which will add -march=haswell to the
command line).
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