ARM Skia NEON patches - 30 - Xfermode: NEON modeprocs

ARM Skia NEON patches - 30 - Xfermode: NEON modeprocs

Xfermode: NEON implementation of SIMD procs

This patch contains a NEON implementation for a number of Xfermodes.
It provides a big speedup on Xfermode benchmarks (currently up to 3x
with gcc4.7 but up to 10x when gcc produces optimal code for it).

Signed-off-by: Kévin PETIT <kevin.petit@arm.com>
BUG=
R=djsollen@google.com, mtklein@google.com, reed@google.com

Author: kevin.petit.arm@gmail.com

Review URL: https://codereview.chromium.org/26627004

git-svn-id: http://skia.googlecode.com/svn/trunk@11777 2bbb7eff-a529-9590-31e7-b0007b416f81