crypto/sha1: Optimise FUNC1 with alternate formulation
According to Wikipedia: http://en.wikipedia.org/wiki/SHA-1
there is an alternate formulation for the FUNC1 transform,
namely
f1 = d xor (b and (c xor d))
instead of
f1 = (b and c) or ((not b) and d)
This reduces the instruction count of FUNC1 from 6 to 4 and
makes about 5% speed improvement on amd64 and suprisingly 17%
on 386.
amd64 Intel(R) Core(TM) i7 CPU Q 820 @ 1.73GHz:
benchmark old ns/op new ns/op delta
BenchmarkHash8Bytes 506 499 -1.38%
BenchmarkHash1K 3099 2961 -4.45%
BenchmarkHash8K 22292 21243 -4.71%
benchmark old MB/s new MB/s speedup
BenchmarkHash8Bytes 15.80 16.00 1.01x
BenchmarkHash1K 330.40 345.82 1.05x
BenchmarkHash8K 367.48 385.63 1.05x
i386 Intel(R) Core(TM) i7 CPU Q 820 @ 1.73GHz:
benchmark old ns/op new ns/op delta
BenchmarkHash8Bytes 647 615 -4.95%
BenchmarkHash1K 3673 3161 -13.94%
BenchmarkHash8K 26141 22374 -14.41%
benchmark old MB/s new MB/s speedup
BenchmarkHash8Bytes 12.35 13.01 1.05x
BenchmarkHash1K 278.74 323.94 1.16x
BenchmarkHash8K 313.37 366.13 1.17x
The improvements on an Intel(R) Core(TM) i7-4770K CPU @
3.50GHz were almost identical.
R=golang-dev, r, hanwen
CC=golang-dev, rsc
https://golang.org/cl/
19910043