[PATCH] aarch64: optimize the unaligned case of memcmp

[Wilco Dijkstra]

Hi,

So I had a look at it using the GLIBC bench-memcmp.c. I quickly got the
unaligned loop to go faster than the aligned one using ccmp, so I had to
tune the unaligned loop too... This is using a similar trick as your byte loop to
remove a branch and 1-2 ALU operations per iteration.

This gives a 24% speedup on both Cortex-A53 and Cortex-A72 for
the aligned loop, and about 18% for the unaligned loop on top of your
patch. Aligning either src1 or src2 appears best as there isn't enough
work in the loops to hide an unaligned access.

Wilco