avcodec/huffman: replace qsort with AV_QSORT
ff_huff_build_tree uses qsort underneath. AV_QSORT is substantially
faster due to the inlining of the comparison callback. Furthermore, this
code is reasonably performance critical, since in e.g the fraps codec,
ff_huff_build_tree is called on every frame. This routine is also called
in vp6 on every frame in some circumstances.
Sample benchmark (x86-64, Haswell, GNU/Linux), vp6 from FATE:
vp6 (old):
78930 decicycles in qsort, 1 runs, 0 skips
45330 decicycles in qsort, 2 runs, 0 skips
27825 decicycles in qsort, 4 runs, 0 skips
17471 decicycles in qsort, 8 runs, 0 skips
12296 decicycles in qsort, 16 runs, 0 skips
9554 decicycles in qsort, 32 runs, 0 skips
8404 decicycles in qsort, 64 runs, 0 skips
7405 decicycles in qsort, 128 runs, 0 skips
6740 decicycles in qsort, 256 runs, 0 skips
7540 decicycles in qsort, 512 runs, 0 skips
9498 decicycles in qsort, 1024 runs, 0 skips
9938 decicycles in qsort, 2048 runs, 0 skips
8043 decicycles in qsort, 4095 runs, 1 skips
vp6 (new):
15880 decicycles in qsort, 1 runs, 0 skips
10730 decicycles in qsort, 2 runs, 0 skips
10155 decicycles in qsort, 4 runs, 0 skips
7805 decicycles in qsort, 8 runs, 0 skips
6883 decicycles in qsort, 16 runs, 0 skips
6305 decicycles in qsort, 32 runs, 0 skips
5854 decicycles in qsort, 64 runs, 0 skips
5152 decicycles in qsort, 128 runs, 0 skips
4452 decicycles in qsort, 256 runs, 0 skips
4161 decicycles in qsort, 511 runs, 1 skips
4081 decicycles in qsort, 1023 runs, 1 skips
4072 decicycles in qsort, 2047 runs, 1 skips
4004 decicycles in qsort, 4095 runs, 1 skips
Reviewed-by: Timothy Gu <timothygu99@gmail.com>
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
