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author | Andreas Rheinhardt <andreas.rheinhardt@outlook.com> | 2022-06-11 23:25:14 +0200 |
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committer | Andreas Rheinhardt <andreas.rheinhardt@outlook.com> | 2022-06-14 01:28:29 +0200 |
commit | 55fc2c5a892c50feb1b9a8f55b74ec6594755ddb (patch) | |
tree | e76ad1561945d9ee48d58e82a027518cae4aca82 /libavcodec/libwebpenc.c | |
parent | ff07492cd800d2904816f6cf0c0cca21d3ccef1e (diff) | |
download | ffmpeg-55fc2c5a892c50feb1b9a8f55b74ec6594755ddb.tar.gz |
swresample/resample: Properly empty MMX state
There is a x86-32 MMXEXT implementation for resampling
planar 16bit data. multiple_resample() therefore calls
emms_c() if it thinks that this needed. And this is bad:
1. It is a maintenance nightmare because changes to the
x86 resample DSP code would necessitate changes to the check
whether to call emms_c().
2. The return value of av_get_cpu_flags() does not tell
whether the MMX DSP functions are in use, as they could
have been overridden by av_force_cpu_flags().
3. The MMX DSP functions will never be overridden in case of
an x86-32 build with --disable-sse2. In this scenario lots of
resampling tests (like swr-resample_exact_lin_async-s16p-8000-48000)
fail because the cpuflags indicate that SSE2 is available
(presuming that the test is run on a CPU with SSE2).
4. The check includes a call to av_get_cpu_flags(). This is not
optimized away for arches other than x86-32.
5. The check takes about as much time as emms_c() itself,
making it pointless.
This commit therefore removes the check and calls emms_c()
unconditionally (it is a no-op for non-x86).
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Diffstat (limited to 'libavcodec/libwebpenc.c')
0 files changed, 0 insertions, 0 deletions