SHA-256:

benchmark          old ns/op    new ns/op    delta
BenchmarkHash1K        21686        16912  -22.01%
BenchmarkHash8K       173216       135020  -22.05%

benchmark           old MB/s     new MB/s  speedup
BenchmarkHash1K        47.22        60.55    1.28x
BenchmarkHash8K        47.29        60.67    1.28x

SHA-512:

benchmark          old ns/op    new ns/op    delta
BenchmarkHash1K        14323        11163  -22.06%
BenchmarkHash8K       114120        88693  -22.28%

benchmark           old MB/s     new MB/s  speedup
BenchmarkHash1K        71.49        91.73    1.28x
BenchmarkHash8K        71.78        92.36    1.29x

R=golang-dev, agl
CC=golang-dev
https://golang.org/cl/6584071