This work is sponsored by, and copyright, Google.
This is similar to the arm version, but due to the larger registers
on aarch64, we can do 8 pixels at a time for all filter sizes.
Examples of runtimes vs the 32 bit version, on a Cortex A53:
ARM AArch64
vp9_loop_filter_h_4_8_10bpp_neon: 213.2 172.6
vp9_loop_filter_h_8_8_10bpp_neon: 281.2 244.2
vp9_loop_filter_h_16_8_10bpp_neon: 657.0 444.5
vp9_loop_filter_h_16_16_10bpp_neon: 1280.4 877.7
vp9_loop_filter_mix2_h_44_16_10bpp_neon: 397.7 358.0
vp9_loop_filter_mix2_h_48_16_10bpp_neon: 465.7 429.0
vp9_loop_filter_mix2_h_84_16_10bpp_neon: 465.7 428.0
vp9_loop_filter_mix2_h_88_16_10bpp_neon: 533.7 499.0
vp9_loop_filter_mix2_v_44_16_10bpp_neon: 271.5 244.0
vp9_loop_filter_mix2_v_48_16_10bpp_neon: 330.0 305.0
vp9_loop_filter_mix2_v_84_16_10bpp_neon: 329.0 306.0
vp9_loop_filter_mix2_v_88_16_10bpp_neon: 386.0 365.0
vp9_loop_filter_v_4_8_10bpp_neon: 150.0 115.2
vp9_loop_filter_v_8_8_10bpp_neon: 209.0 175.5
vp9_loop_filter_v_16_8_10bpp_neon: 492.7 345.2
vp9_loop_filter_v_16_16_10bpp_neon: 951.0 682.7
This is significantly faster than the ARM version in almost
all cases except for the mix2 functions.
Based on START_TIMER/STOP_TIMER wrapping around a few individual
functions, the speedup vs C code is around 2-3x.
Signed-off-by: Martin Storsjö <martin@martin.st>
