For widths of 32 pixels and more, loop first horizontally,
then vertically.
Previously, this function would process a 16 pixel wide slice
of the block, looping vertically. After processing the whole
height, it would backtrack and process the next 16 pixel wide
slice.
When doing 8tap filtering horizontally, the function must load
7 more pixels (in practice, 8) following the actual inputs, and
this was done for each slice.
By iterating first horizontally throughout each line, then
vertically, we access data in a more cache friendly order, and
we don't need to reload data unnecessarily.
Keep the original order in put_hevc_\type\()_h12_8_neon; the
only suboptimal case there is for width=24. But specializing
an optimal variant for that would require more code, which
might not be worth it.
For the h16 case, this implementation would give a slowdown,
as it now loads the first 8 pixels separately from the rest, but
for larger widths, it is a gain. Therefore, keep the h16 case
as it was (but remove the outer loop), and create a new specialized
version for horizontal looping with 16 pixels at a time.
Before: Cortex A53 A72 A73 Graviton 3
put_hevc_qpel_h16_8_neon: 710.5 667.7 692.5 211.0
put_hevc_qpel_h32_8_neon: 2791.5 2643.5 2732.0 883.5
put_hevc_qpel_h64_8_neon: 10954.0 10657.0 10874.2 3241.5
After:
put_hevc_qpel_h16_8_neon: 697.5 663.5 705.7 212.5
put_hevc_qpel_h32_8_neon: 2767.2 2684.5 2791.2 920.5
put_hevc_qpel_h64_8_neon: 10559.2 10471.5 10932.2 3051.7
Signed-off-by: Martin Storsjö <martin@martin.st>
Martin Storsjö
10 months ago