[FFmpeg-devel] [PATCH 1/2] avcodec/x86: move simple_idct to external assembly

[James Darnley]

On 2017-05-29 16:51, James Darnley wrote:
> ---
> Changes:
>  - Changed type of d40000 constant to dwords because it gets used as dwords.
>  - Changed or removed HAVE_MMX_INLINE preprocessor guards.
>  - Added note about conversion from inline.
>  - New file no longer has "2" suffix.
>  - Whitespace (indentation and alignment).
> 
>  libavcodec/tests/x86/dct.c     |   2 +-
>  libavcodec/x86/Makefile        |   4 +-
>  libavcodec/x86/idctdsp_init.c  |   4 -
>  libavcodec/x86/simple_idct.asm | 889 +++++++++++++++++++++++++++++++++++++++
>  libavcodec/x86/simple_idct.c   | 929 -----------------------------------------
>  5 files changed, 892 insertions(+), 936 deletions(-)
>  create mode 100644 libavcodec/x86/simple_idct.asm
>  delete mode 100644 libavcodec/x86/simple_idct.c

Ronald queried on IRC about the performance.  The libavcodec/tests/dct
utility reports these numbers

Yorkfield:
 - inline:   IDCT SIMPLE-MMX: 15715.9 kdct/s
 - external: IDCT SIMPLE-MMX: 15699.9 kdct/s

Skylake-U:
 - inline:   IDCT SIMPLE-MMX: 11193.3 kdct/s
 - external: IDCT SIMPLE-MMX: 11189.7 kdct/s

I assume those units are "thousand discrete cosine transforms per second".