This is more spec-compliant because it does not rely
on dead-code elimination by the compiler. Especially
MSVC has problems with this, as can be seen in
https://ffmpeg.org/pipermail/ffmpeg-devel/2022-May/296373.html
or
https://ffmpeg.org/pipermail/ffmpeg-devel/2022-May/297022.html
This commit does not eliminate every instance where we rely
on dead code elimination: It only tackles branching to
the initialization of arch-specific dsp code, not e.g. all
uses of CONFIG_ and HAVE_ checks. But maybe it is already
enough to compile FFmpeg with MSVC with whole-programm-optimizations
enabled (if one does not disable too many components).
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Some of these were made possible by moving several common macros to
libavutil/macros.h.
While just at it, also improve the other headers a bit.
Reviewed-by: Martin Storsjö <martin@martin.st>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Fixes: 673/clusterfuzz-testcase-5948736536576000
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/targets/ffmpeg
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This fixes ubsan warnings in non debug builds by using unsigned operations
in debug builds the correct signed operations are retained so that overflows
(which should not occur in valid files and may indicate problems in the DSP code
or decoder) can be detected.
Alternatively they can be changed to unsigned unconditionally, then its
not possible though to detect overflows easily if someone wants to test
the DSP code for overflows.
The 2nd alternative would be to leave the code as it is and accept that
there are undefined operations in the DSP code and that ubsan output is
full of them in some cases.
Similar changes would be needed in some other DSP routines
Suggested-by: Matt Wolenetz <wolenetz@google.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
benchmarked on sandybridge x86_64:
1358232 decicycles in flac_lpc_32_c
1244575 decicycles in flac_lpc_32_sse4, James Almer's patch
650045 decicycles in flac_lpc_32_sse4, this patch
I haven't tested the edgecases such as odd block lengths
odd block length tested-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Andreas Rheinhardt
Michael Niedermayer
Carl Eugen Hoyos
James Almer
James Darnley
Loren Merritt
Justin Ruggles
Mans Rullgard