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cmd/compile: unify reflect, string and slice copy runtime functions

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Use a common runtime slicecopy function to copy strings or slices
into slices. This deduplicates similar code previously used in
reflect.slicecopy and runtime.stringslicecopy.

Change-Id: I09572ff0647a9e12bb5c6989689ce1c43f16b7f1
Reviewed-on: https://go-review.googlesource.com/c/go/+/254658
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Martin Möhrmann <moehrmann@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Martin Möhrmann 2020-09-14 16:30:43 +02:00
parent eaa97fbf20
commit 790fa1c546
6 changed files with 248 additions and 304 deletions
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44
src/runtime/slice.go
View file

@ -243,12 +243,13 @@ func isPowerOfTwo(x uintptr) bool {
return x&(x-1) == 0
}
func slicecopy(toPtr unsafe.Pointer, toLen int, fmPtr unsafe.Pointer, fmLen int, width uintptr) int {
if fmLen == 0 || toLen == 0 {
// slicecopy is used to copy from a string or slice of pointerless elements into a slice.
func slicecopy(toPtr unsafe.Pointer, toLen int, fromPtr unsafe.Pointer, fromLen int, width uintptr) int {
if fromLen == 0 || toLen == 0 {
return 0
}
n := fmLen
n := fromLen
if toLen < n {
n = toLen
}
@ -257,46 +258,23 @@ func slicecopy(toPtr unsafe.Pointer, toLen int, fmPtr unsafe.Pointer, fmLen int,
return n
}
size := uintptr(n) * width
if raceenabled {
callerpc := getcallerpc()
pc := funcPC(slicecopy)
racereadrangepc(fmPtr, uintptr(n*int(width)), callerpc, pc)
racewriterangepc(toPtr, uintptr(n*int(width)), callerpc, pc)
racereadrangepc(fromPtr, size, callerpc, pc)
racewriterangepc(toPtr, size, callerpc, pc)
}
if msanenabled {
msanread(fmPtr, uintptr(n*int(width)))
msanwrite(toPtr, uintptr(n*int(width)))
msanread(fromPtr, size)
msanwrite(toPtr, size)
}
size := uintptr(n) * width
if size == 1 { // common case worth about 2x to do here
// TODO: is this still worth it with new memmove impl?
*(*byte)(toPtr) = *(*byte)(fmPtr) // known to be a byte pointer
*(*byte)(toPtr) = *(*byte)(fromPtr) // known to be a byte pointer
} else {
memmove(toPtr, fmPtr, size)
memmove(toPtr, fromPtr, size)
}
return n
}
func slicestringcopy(toPtr *byte, toLen int, fm string) int {
if len(fm) == 0 || toLen == 0 {
return 0
}
n := len(fm)
if toLen < n {
n = toLen
}
if raceenabled {
callerpc := getcallerpc()
pc := funcPC(slicestringcopy)
racewriterangepc(unsafe.Pointer(toPtr), uintptr(n), callerpc, pc)
}
if msanenabled {
msanwrite(unsafe.Pointer(toPtr), uintptr(n))
}
memmove(unsafe.Pointer(toPtr), stringStructOf(&fm).str, uintptr(n))
return n
}