[FFmpeg-devel] [PATCH 3/5] avcodec/fft_fixed: Hardcode cosine tables to save space

[Lynne]

Jan 7, 2021, 00:13 by andreas.rheinhardt at gmail.com:

> The tables that are used take 256B; the code to initialize them uses
> 281B here (GCC 9.3, x64, -O3, but in av_cold functions). On top of that,
> removing this code also allows to remove the array of AVOnce used to
> guard the cosine tables against multiple initializations; this also
> removes relocations.
>
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
> ---
>  libavcodec/Makefile       |  2 +-
>  libavcodec/fft.h          | 19 +++++++++---------
>  libavcodec/fft_fixed.c    | 42 +++++++++++++++++++++++++++++++++++++++
>  libavcodec/fft_template.c | 27 +++++++++----------------
>  4 files changed, 62 insertions(+), 28 deletions(-)
>

I'm not a big fan of this one. It saves minor amounts of space, introduces
more hard/soft table init splits, and is for code due to be replaced by
libavutil/tx anyway.