On Fri, 26 Jan 2024, Martin Storsjö wrote:
On Fri, 26 Jan 2024, Martin Storsjö wrote:
These inline implementations of AV_COPY64, AV_SWAP64 and AV_ZERO64
are known to clobber the FPU state - which has to be restored
with the 'emms' instruction afterwards.
This was known and signaled with the FF_COPY_SWAP_ZERO_USES_MMX
define, which calling code seems to have been supposed to check,
in order to call emms_c() after using them. See
0b1972d4096df5879038f0af776f87f41e90ebd4,
29c4c0886d143790fcbeddbe40a23dfc6f56345c and
df215e575850e41b19aeb1fd99e53372a6b3d537 for history on earlier
fixes in the same area.
However, new code can use these AV_*64() macros without knowing
about the need to call emms_c().
Just get rid of these dangerous inline assembly snippets; this
doesn't make any difference for 64 bit architectures anyway.
Signed-off-by: Martin Storsjö <mar...@martin.st>
---
libavcodec/dca_core.c | 16 ----------------
libavutil/x86/intreadwrite.h | 36 ------------------------------------
2 files changed, 52 deletions(-)
I forgot to add some more context here; the VVC tests fail on i386 in some
cases.
https://patchwork.ffmpeg.org/project/ffmpeg/patch/20240125170518.61211-1-p...@frankplowman.com/
fixes this, by using av_log2() instead of the float log2() in the VVC
decoder. This patch fixes the same issue as well, by eliminating the FPU
state clobbering (so that float math functions anywhere in decoders work as
expected).
If there are no better suggestions here, I would like to go ahead and push
this.
// Martin
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