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runtime: optimize slicebytestostring

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Inline rawstringtmp and simplify.
Use memmove instead of copy.

name                     old time/op  new time/op  delta
SliceByteToString/1-8    19.4ns ± 2%  14.1ns ± 1%  -27.04%  (p=0.000 n=20+17)
SliceByteToString/2-8    20.8ns ± 2%  15.5ns ± 2%  -25.46%  (p=0.000 n=20+20)
SliceByteToString/4-8    20.7ns ± 1%  14.9ns ± 1%  -28.30%  (p=0.000 n=20+20)
SliceByteToString/8-8    23.2ns ± 1%  17.1ns ± 1%  -26.22%  (p=0.000 n=19+19)
SliceByteToString/16-8   29.4ns ± 1%  23.6ns ± 1%  -19.76%  (p=0.000 n=17+20)
SliceByteToString/32-8   31.4ns ± 1%  26.0ns ± 1%  -17.11%  (p=0.000 n=16+19)
SliceByteToString/64-8   36.1ns ± 0%  30.0ns ± 0%  -16.96%  (p=0.000 n=16+16)
SliceByteToString/128-8  46.9ns ± 0%  38.9ns ± 0%  -17.15%  (p=0.000 n=17+19)

Change-Id: I422e688830e4a9bd21897d1f74964625b735f436
Reviewed-on: https://go-review.googlesource.com/37791
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Marvin Stenger <marvin.stenger94@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Josh Bleecher Snyder 2017-03-04 16:54:50 -08:00
parent 228438e097
commit 23be728950
1 changed files with 14 additions and 6 deletions
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20
src/runtime/string.go
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@ -69,7 +69,7 @@ func concatstring5(buf *tmpBuf, a [5]string) string {
// Buf is a fixed-size buffer for the result, // Buf is a fixed-size buffer for the result,
// it is not nil if the result does not escape. // it is not nil if the result does not escape.
func slicebytetostring(buf *tmpBuf, b []byte) string { func slicebytetostring(buf *tmpBuf, b []byte) (str string) {
l := len(b) l := len(b)
if l == 0 { if l == 0 {
// Turns out to be a relatively common case. // Turns out to be a relatively common case.
@ -77,18 +77,26 @@ func slicebytetostring(buf *tmpBuf, b []byte) string {
// you find the indices and convert the subslice to string. // you find the indices and convert the subslice to string.
return "" return ""
} }
if raceenabled && l > 0 { if raceenabled {
racereadrangepc(unsafe.Pointer(&b[0]), racereadrangepc(unsafe.Pointer(&b[0]),
uintptr(l), uintptr(l),
getcallerpc(unsafe.Pointer(&buf)), getcallerpc(unsafe.Pointer(&buf)),
funcPC(slicebytetostring)) funcPC(slicebytetostring))
} }
if msanenabled && l > 0 { if msanenabled {
msanread(unsafe.Pointer(&b[0]), uintptr(l)) msanread(unsafe.Pointer(&b[0]), uintptr(l))
} }
s, c := rawstringtmp(buf, l)
copy(c, b) var p unsafe.Pointer
return s if buf != nil && len(b) <= len(buf) {
p = unsafe.Pointer(buf)
} else {
p = mallocgc(uintptr(len(b)), nil, false)
}
stringStructOf(&str).str = p
stringStructOf(&str).len = len(b)
memmove(p, (*(*slice)(unsafe.Pointer(&b))).array, uintptr(len(b)))
return
} }
// stringDataOnStack reports whether the string's data is // stringDataOnStack reports whether the string's data is