vmx: implement fast path iterator vmx_fetch_a8

no changes were observed when running cairo trimmed benchmarks.

Running "lowlevel-blt-bench src_8_8888" on POWER8, 8 cores,
3.4GHz, RHEL 7.1 ppc64le gave the following results:

reference memcpy speed = 25197.2MB/s (6299.3MP/s for 32bpp fills)

                Before          After           Change
              --------------------------------------------
L1              965.34          3936           +307.73%
L2              942.99          3436.29        +264.40%
M               902.24          2757.77        +205.66%
HT              448.46          784.99         +75.04%
VT              430.05          819.78         +90.62%
R               412.9           717.04         +73.66%
RT              168.93          220.63         +30.60%
Kops/s          1025            1303           +27.12%

It was benchmarked against commid id e2d211a from pixman/master

Siarhei Siamashka reported that on playstation3, it shows the following
results:

== before ==

              src_8_8888 =  L1: 194.37  L2: 198.46  M:155.90 (148.35%)
              HT: 59.18  VT: 36.71  R: 38.93  RT: 12.79 ( 106Kops/s)

== after ==

              src_8_8888 =  L1: 373.96  L2: 391.10  M:245.81 (233.88%)
              HT: 80.81  VT: 44.33  R: 48.10  RT: 14.79 ( 122Kops/s)

Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
Acked-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
1 file changed