vmx: implement fast path scaled nearest vmx_8888_8888_OVER
It was benchmarked against commid id 2be523b from pixman/master
POWER8, 8 cores, 3.4GHz, RHEL 7.1 ppc64le.
reference memcpy speed = 24764.8MB/s (6191.2MP/s for 32bpp fills)
Before After Change
---------------------------------------------
L1 134.36 181.68 +35.22%
L2 135.07 180.67 +33.76%
M 134.6 180.51 +34.11%
HT 121.77 128.79 +5.76%
VT 120.49 145.07 +20.40%
R 93.83 102.3 +9.03%
RT 50.82 46.93 -7.65%
Kops/s 448 422 -5.80%
cairo trimmed benchmarks :
Speedups
========
t-firefox-asteroids 533.92 -> 497.92 : 1.07x
t-midori-zoomed 692.98 -> 651.24 : 1.06x
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
Acked-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>