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Author SHA1 Message Date
Rémi Denis-Courmont f0ef11ea83 lavc/bswapdsp: RISC-V B bswap_buf 
Simply taking the Zbb REV8 instruction into use in a simple loop gives
some significant savings:

bswap_buf_c: 1081.0
bswap_buf_rvb_b: 771.0

But we can also use the 64-bit REV8 as a pseudo-SIMD instruction with
just one additional shift, and one fewer load, effectively doubling the
bandwidth. Consequently, this patch is useful even if the compile-time
target has Zbb enabled for C code:

bswap_buf_c: 1081.0
bswap_buf_rvb_b: 341.0  (this patch)

On the other hand, this approach fails miserably for bswap16_buf as the
ratio of shifts and stores becomes unfavorable compared to naïve C:

bswap16_buf_c: 1542.0
bswap16_buf_rvb_b: 1803.7

Unrolling to process 128 bits (4 samples) at a time actually worsens
performance ever so slightly:

bswap_buf_c: 1081.0
bswap_buf_rvb_b: 408.5
 2022-10-05 08:26:19 +02:00
Andreas Rheinhardt 40e6575aa3 all: Replace if (ARCH_FOO) checks by #if ARCH_FOO 
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>
 2022-06-15 04:56:37 +02:00
Michael Niedermayer 35bb74900b Merge commit 'c67b449bebbe0b35c73b203683e77a0a649bc765' 
* commit 'c67b449bebbe0b35c73b203683e77a0a649bc765':
  dsputil: Split bswap*_buf() off into a separate context

Conflicts:
	configure
	libavcodec/4xm.c
	libavcodec/ac3dec.c
	libavcodec/ac3dec.h
	libavcodec/apedec.c
	libavcodec/eamad.c
	libavcodec/flacenc.c
	libavcodec/fraps.c
	libavcodec/huffyuv.c
	libavcodec/huffyuvdec.c
	libavcodec/motionpixels.c
	libavcodec/truemotion2.c
	libavcodec/x86/Makefile
	libavcodec/x86/dsputil_init.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>
 2014-06-23 13:31:26 +02:00
Diego Biurrun c67b449beb dsputil: Split bswap*_buf() off into a separate context 2014-06-22 18:22:31 -07:00