Trivial optimization.
Cached string indexing in inner loop of Btoui64.
Before:
strconv_test.BenchmarkAtoi
5000000 309 ns/op
strconv_test.BenchmarkAtoiNeg
5000000 325 ns/op
strconv_test.BenchmarkAtoi64
5000000 465 ns/op
strconv_test.BenchmarkAtoi64Neg
5000000 469 ns/op
After:
strconv_test.BenchmarkAtoi
10000000 182 ns/op
strconv_test.BenchmarkAtoiNeg
10000000 193 ns/op
strconv_test.BenchmarkAtoi64
10000000 251 ns/op
strconv_test.BenchmarkAtoi64Neg
10000000 258 ns/op
R=golang-dev, gri
CC=golang-dev
https://golang.org/cl/
1227042