runtime: special case copy, equal for one-word interface values
Based on the observation that a great number of the types that
are copied or compared in interfaces, maps, and channels are
word-sized, this uses specialized copy and equality functions
for them that use a word instead of 4 or 8 bytes. Seems to yield
0-6% improvements in performance in the benchmarks I've run.
For example, with the regexp benchmarks:
Before:
regexp.BenchmarkLiteral 500000 3.26 µs/op
regexp.BenchmarkNotLiteral 100000 13.67 µs/op
regexp.BenchmarkMatchClass 100000 18.72 µs/op
regexp.BenchmarkMatchClass_InRange 100000 20.04 µs/op
regexp.BenchmarkReplaceAll 100000 27.85 µs/op
After:
regexp.BenchmarkLiteral 500000 3.11 µs/op
regexp.BenchmarkNotLiteral 200000 13.29 µs/op
regexp.BenchmarkMatchClass 100000 17.65 µs/op
regexp.BenchmarkMatchClass_InRange 100000 18.49 µs/op
regexp.BenchmarkReplaceAll 100000 26.34 µs/op
R=rsc
CC=golang-dev
https://golang.org/cl/
1967047