swscale/input: Avoid calls to av_pix_fmt_desc_get()

Up until now, libswscale/input.c used a macro to read
an input pixel which involved a call to av_pix_fmt_desc_get()
to find out whether the input pixel format is BE or LE
despite this being known at compile-time (there are templates
per pixfmt). Even worse, these calls are made in a loop,
so that e.g. there are six calls to av_pix_fmt_desc_get()
for every pair of UV pixel processed in
rgb64ToUV_half_c_template().

This commit modifies these macros to ensure that isBE()
is evaluated at compile-time. This saved 9743B of .text
for me (GCC 11.2, -O3). For a simple RGB64LE->YUV420P
transformation like
ffmpeg -f lavfi -i haldclutsrc,format=rgba64le -pix_fmt yuv420p \
-threads 1  -t 1:00  -f null -
the amount of decicycles spent in rgb64LEToUV_half_c
(which is created via the template mentioned above)
decreases from 19751 to 5341; for RGBA64BE the number
went down from 11945 to 5393. For shared builds (where
the call to av_pix_fmt_desc_get() is indirect) the old numbers
are 15230 for RGBA64BE and 27502 for RGBA64LE, whereas
the numbers with this patch are indistinguishable from
the numbers from a static build.

Also make the macros that are touched conform to the
usual convention of using uppercase names while just at it.

Reviewed-by: Anton Khirnov <anton@khirnov.net>
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

0 files changed, 0 insertions, 0 deletions