vector: add SIMD versions of xxxAccumulateOpSrc.

name                         old time/op  new time/op  delta
GlyphAlpha16Src-8            3.37µs ± 0%  3.07µs ± 1%   -8.86%    (p=0.000 n=9+9)
GlyphAlpha32Src-8            6.01µs ± 1%  4.55µs ± 0%  -24.28%   (p=0.000 n=10+9)
GlyphAlpha64Src-8            13.2µs ± 0%   8.1µs ± 0%  -38.69%   (p=0.000 n=10+9)
GlyphAlpha128Src-8           32.9µs ± 0%  16.9µs ± 0%  -48.85%   (p=0.000 n=10+9)
GlyphAlpha256Src-8           98.0µs ± 0%  43.6µs ± 1%  -55.50%  (p=0.000 n=10+10)

A comparison of the non-SIMD and SIMD versions:

name                             time/op
FixedAccumulateOpSrc16-8          368ns ± 0%
FixedAccumulateOpSrcSIMD16-8     86.8ns ± 1%
FloatingAccumulateOpSrc16-8       434ns ± 0%
FloatingAccumulateOpSrcSIMD16-8   119ns ± 0%
FixedAccumulateOpSrc64-8         6.12µs ± 0%
FixedAccumulateOpSrcSIMD64-8     1.17µs ± 0%
FloatingAccumulateOpSrc64-8      7.15µs ± 0%
FloatingAccumulateOpSrcSIMD64-8  1.68µs ± 1%

Change-Id: I58e5c7a3ecd12e536aab8e765e94275453d0eac8
Reviewed-on: https://go-review.googlesource.com/30431
Reviewed-by: David Crawshaw <crawshaw@golang.org>
7 files changed