Stowage/go
2
0
Fork 0
mirror of https://github.com/golang/go.git synced 2025-12-08 06:10:04 +00:00
Code Issues Projects Releases Packages Wiki Activity

cmd/compile: improve string iteration performance

Browse source 
Generate a for loop for ranging over strings that only needs to call
the runtime function charntorune for non ASCII characters.

This provides faster iteration over ASCII characters and slightly
faster iteration for other characters.

The runtime function charntorune is changed to take an index from where
to start decoding and returns the index after the last byte belonging
to the decoded rune.

All call sites of charntorune in the runtime are replaced by a for loop
that will be transformed by the compiler instead of calling the charntorune
function directly.

go binary size decreases by 80 bytes.
godoc binary size increases by around 4 kilobytes.

runtime:

name                           old time/op  new time/op  delta
RuneIterate/range/ASCII-4      43.7ns ± 3%  10.3ns ± 4%  -76.33%  (p=0.000 n=44+45)
RuneIterate/range/Japanese-4   72.5ns ± 2%  62.8ns ± 2%  -13.41%  (p=0.000 n=49+50)
RuneIterate/range1/ASCII-4     43.5ns ± 2%  10.4ns ± 3%  -76.18%  (p=0.000 n=50+50)
RuneIterate/range1/Japanese-4  72.5ns ± 2%  62.9ns ± 2%  -13.26%  (p=0.000 n=50+49)
RuneIterate/range2/ASCII-4     43.5ns ± 3%  10.3ns ± 2%  -76.22%  (p=0.000 n=48+47)
RuneIterate/range2/Japanese-4  72.4ns ± 2%  62.7ns ± 2%  -13.47%  (p=0.000 n=50+50)

strings:

name                 old time/op    new time/op    delta
IndexRune-4            64.7ns ± 5%    22.4ns ± 3%  -65.43%  (p=0.000 n=25+21)
MapNoChanges-4          269ns ± 2%     157ns ± 2%  -41.46%  (p=0.000 n=23+24)
Fields-4               23.0ms ± 2%    19.7ms ± 2%  -14.35%  (p=0.000 n=25+25)
FieldsFunc-4           23.1ms ± 2%    19.6ms ± 2%  -14.94%  (p=0.000 n=25+24)

name                 old speed      new speed      delta
Fields-4             45.6MB/s ± 2%  53.2MB/s ± 2%  +16.87%  (p=0.000 n=24+25)
FieldsFunc-4         45.5MB/s ± 2%  53.5MB/s ± 2%  +17.57%  (p=0.000 n=25+24)

Updates #13162

Change-Id: I79ffaf828d82bf9887592f08e5cad883e9f39701
Reviewed-on: https://go-review.googlesource.com/27853
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Martin Möhrmann <martisch@uos.de>
This commit is contained in:
Martin Möhrmann 2016-08-26 15:00:46 +02:00 • committed by Martin Möhrmann
parent 0d7a2241cb
commit 0dae9dfb08
8 changed files with 290 additions and 224 deletions
Download patch file Download diff file Expand all files Collapse all files

47
src/runtime/string.go
View file

@ -163,12 +163,10 @@ func stringtoslicerune(buf *[tmpStringBufSize]rune, s string) []rune {
// two passes.
// unlike slicerunetostring, no race because strings are immutable.
n := 0
t := s
for len(s) > 0 {
_, k := charntorune(s)
s = s[k:]
for range s {
n++
}
var a []rune
if buf != nil && n <= len(buf) {
*buf = [tmpStringBufSize]rune{}
@ -176,10 +174,9 @@ func stringtoslicerune(buf *[tmpStringBufSize]rune, s string) []rune {
} else {
a = rawruneslice(n)
}
n = 0
for len(t) > 0 {
r, k := charntorune(t)
t = t[k:]
for _, r := range s {
a[n] = r
n++
}
@ -244,42 +241,6 @@ func intstring(buf *[4]byte, v int64) string {
return s[:n]
}
// stringiter returns the index of the next
// rune after the rune that starts at s[k].
func stringiter(s string, k int) int {
if k >= len(s) {
// 0 is end of iteration
return 0
}
c := s[k]
if c < runeself {
return k + 1
}
// multi-char rune
_, n := charntorune(s[k:])
return k + n
}
// stringiter2 returns the rune that starts at s[k]
// and the index where the next rune starts.
func stringiter2(s string, k int) (int, rune) {
if k >= len(s) {
// 0 is end of iteration
return 0, 0
}
c := s[k]
if c < runeself {
return k + 1, rune(c)
}
// multi-char rune
r, n := charntorune(s[k:])
return k + n, r
}
// rawstring allocates storage for a new string. The returned
// string and byte slice both refer to the same storage.
// The storage is not zeroed. Callers should use