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| author | Andreas Rheinhardt <andreas.rheinhardt@outlook.com> | 2023-11-01 10:01:09 +0100 |
|---|---|---|
| committer | Andreas Rheinhardt <andreas.rheinhardt@outlook.com> | 2023-11-04 01:26:03 +0100 |
| commit | 5b85ca5317f28a73eadf10d604d2a7421b84bed8 (patch) | |
| tree | d678474b9d9ed6a1a5bf30d615c188b8f0db7a1c /libavutil/x86 | |
| parent | 8661b5e8f9e63d2775978f2aa3ee6fae4d515c53 (diff) | |
| download | ffmpeg-5b85ca5317f28a73eadf10d604d2a7421b84bed8.tar.gz | |
avutil/x86/pixelutils: Empty MMX state in ff_pixelutils_sad_8x8_mmxext
We currently mostly do not empty the MMX state in our MMX
DSP functions; instead we only do so before code that might
be using x87 code. This is a violation of the System V i386 ABI
(and maybe of other ABIs, too):
"The CPU shall be in x87 mode upon entry to a function. Therefore,
every function that uses the MMX registers is required to issue an
emms or femms instruction after using MMX registers, before returning
or calling another function." (See 2.2.1 in [1])
This patch does not intend to change all these functions to abide
by the ABI; it only does so for ff_pixelutils_sad_8x8_mmxext, as this
function can by called by external users, because it is exported
via the pixelutils API. Without this, the following fragment will
assert (on x86/x64):
uint8_t src1[8 * 8], src2[8 * 8];
av_pixelutils_sad_fn fn = av_pixelutils_get_sad_fn(3, 3, 0, NULL);
fn(src1, 8, src2, 8);
av_assert0_fpu();
[1]: https://raw.githubusercontent.com/wiki/hjl-tools/x86-psABI/intel386-psABI-1.1.pdf
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Diffstat (limited to 'libavutil/x86')
| -rw-r--r-- | libavutil/x86/pixelutils.asm | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/libavutil/x86/pixelutils.asm b/libavutil/x86/pixelutils.asm index fbe9b45971..0bcccb51f5 100644 --- a/libavutil/x86/pixelutils.asm +++ b/libavutil/x86/pixelutils.asm @@ -43,6 +43,7 @@ cglobal pixelutils_sad_8x8, 4,4,0, src1, stride1, src2, stride2 lea src2q, [src2q + 2*stride2q] %endrep movd eax, m2 + emms RET ;------------------------------------------------------------------------------- |