go/src/unicode/utf8
Joe Tsai 8eca08611a unicode/utf8: optimize ValidRune
Re-writing the switch statement as a single boolean expression
reduces the number of branches that the compiler generates.
It is also arguably easier to read as a pair of numeric ranges
that valid runes can exist in.

No test changes since the existing test does a good job of
testing all of the boundaries.

This change was to gain back some performance after a correctness
fix done in http://golang.org/cl/32123.

The correctness fix (CL/32123) slowed down the benchmarks slightly:
	benchmark                   old ns/op     new ns/op     delta
	BenchmarkIndexRune/10-4     19.3          21.6          +11.92%
	BenchmarkIndexRune/32-4     33.6          35.2          +4.76%

Since the fix relies on utf8.ValidRune, this CL improves benchmarks:
	benchmark                   old ns/op     new ns/op     delta
	BenchmarkIndexRune/10-4     21.6          20.0          -7.41%
	BenchmarkIndexRune/32-4     35.2          33.5          -4.83%

Change-Id: Ib1ca10a2e29c90e879a8ef9b7221c33e85d015d8
Reviewed-on: https://go-review.googlesource.com/32122
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
2016-10-26 23:02:52 +00:00
..
example_test.go
utf8.go unicode/utf8: optimize ValidRune 2016-10-26 23:02:52 +00:00
utf8_test.go runtime: speed up non-ASCII rune decoding 2016-10-17 11:25:22 +00:00