Also disable the mmx/iwht optimization when the bitexact flag is set.
With synthetically coded coefficients (i.e. these that lead to a
residual well outside the [-255,255] range), our optimizations will
overflow. It doesn't make sense to fix the overflows, since they can
only occur on synthetic input, not on real fwht-generated input. Thus,
add a bitexact flag that disables this optimization.
See sample vp90-2-14-resize-fp-tiles-16-8-4-2-1.webm from the vp9 test
vector set which reproduces the issue. This probably costs a few cycles,
but I don't think there's an easy way to workaround that.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Before this patch, we explicitly modify rsp, which isn't necessarily
universally acceptable, since the space under the stack pointer might
be modified in things like signal handlers. Therefore, use an explicit
register to hold the stack pointer relative to the bottom of the stack
(i.e. rsp). This will also clear out valgrind errors about the use of
uninitialized data that started occurring after the idct16x16/ssse3
optimizations were first merged.
Runtime of the full 32x32 idct goes from 2446 to 2441 cycles (intra) or
from 1425 to 1306 cycles (inter). Overall runtime is not significantly
affected.
Runtime of all IDCTs together goes from 3327 to 2473 cycles (intra, i.e.
~35% faster) or from 2312 to 1448 cycles (inter, i.e. ~60% faster). Total
decode time of ped1080p.webm goes from 8.086sec to 7.974sec (1.4% faster).
Sub-IDCTs will follow later. ped1080.webm goes from 9.295s to 8.191s
(13.5% faster). The IDCT itself goes from 4372 (intra) or 4337 (inter)
to 403 (intra) or 329 (inter) cycles for the DC-only form, 23755 (intra)
or 23723 (inter) to 3497 (intra) or 3607 (inter) cycles for the no-DC
form, which averages from 23393 (intra) or 16612 (inter) to 3449 (intra)
or 2392 (inter) for all 32x32s together, i.e. about ~7x faster (all
tests done on ped1080p.webm).
Sub8x8 speed (w/o dc-only case) goes from ~750 cycles (inter) or ~735
cycles (intra) to ~415 cycles (inter) or ~430 cycles (intra). Average
overall 16x16 idct speed goes from ~635 cycles (inter) or ~720 cycles
(intra) to ~415 cycles (inter) or ~545 (intra) - all measurements done
using ped1080p.webm.
Currently only dc-only and full 16x16. Other subforms will follow in the
near future. Total decoding time of ped1080p.webm goes from 9.7 to 9.3
seconds. DC-only goes from 957 -> 131 cycles, and the full IDCT goes
from ~4050 to ~745 cycles.
Originally written by Ronald S. Bultje <rsbultje@gmail.com> and
Clément Bœsch <u@pkh.me>
Further contributions by:
Anton Khirnov <anton@khirnov.net>
Diego Biurrun <diego@biurrun.de>
Luca Barbato <lu_zero@gentoo.org>
Martin Storsjö <martin@martin.st>
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
Signed-off-by: Anton Khirnov <anton@khirnov.net>
1789 decicycles in idct_idct_4x4_add_c, 262136 runs, 8 skips
1839 decicycles in idct_idct_4x4_add_c, 524270 runs, 18 skips
1864 decicycles in idct_idct_4x4_add_c, 1048548 runs, 28 skips
529 decicycles in ff_vp9_idct_idct_4x4_add_ssse3, 262138 runs, 6 skips
516 decicycles in ff_vp9_idct_idct_4x4_add_ssse3, 524282 runs, 6 skips
474 decicycles in ff_vp9_idct_idct_4x4_add_ssse3, 1048565 runs, 11 skips
(~3.9x faster)
7726 decicycles in idct_idct_8x8_add_c, 1048433 runs, 143 skips
7732 decicycles in idct_idct_8x8_add_c, 2096882 runs, 270 skips
7731 decicycles in idct_idct_8x8_add_c, 4193772 runs, 532 skips
1145 decicycles in ff_vp9_idct_idct_8x8_add_ssse3, 1048549 runs, 27 skips
1137 decicycles in ff_vp9_idct_idct_8x8_add_ssse3, 2097097 runs, 55 skips
1086 decicycles in ff_vp9_idct_idct_8x8_add_ssse3, 4194188 runs, 116 skips
(~7.1x faster)
Overall decode time before commit:
16.48s user 0.03s system 99% cpu 16.526 total
16.54s user 0.01s system 99% cpu 16.566 total
16.46s user 0.03s system 99% cpu 16.511 total
Overall decode time after commit:
16.34s user 0.02s system 99% cpu 16.378 total
16.28s user 0.02s system 99% cpu 16.315 total
16.32s user 0.03s system 99% cpu 16.366 total
Tested on i7 920 with 40s 1080p footage.
Ronald S. Bultje
James Almer
Christophe Gisquet
Clément Bœsch