To do so, simply add these init files to X86ASM-OBJS instead of OBJS
in the Makefile. The former is already used for the actual assembly
files, but using them for the C init files just works, because the build
system uses file extensions to derive whether it is a C or a NASM file.
This avoids compiling unused function stubs and also reduces our
reliance on DCE: We don't add %if checks to the asm files except
for AVX, AVX2, FMA3, FMA4, XOP and AVX512, so all the MMX-SSE4
functions will be available. It also allows to remove HAVE_X86ASM checks
in these init files.
Reviewed-by: Kacper Michajłow <kasper93@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
With explicit unrolling, we can skip half of the sign bit flips, and
the compiler is then better able to optimise the scalar loop:
predictor_c: 31376.0 (before)
predictor_c: 23703.0 (after)
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>
