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runtime: simplify typedmemmovepartial

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The offset is always a multiple of the pointer size.

Change-Id: I790e087e89a081044a3ec35d99880533a4c929bd
Reviewed-on: https://go-review.googlesource.com/c/go/+/227540
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
This commit is contained in:
Ian Lance Taylor 2020-04-07 21:39:39 -07:00
parent ddfc55b076
commit b4bb47d88f
1 changed files with 8 additions and 22 deletions
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30
src/runtime/mbarrier.go
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@ -193,32 +193,18 @@ func reflectlite_typedmemmove(typ *_type, dst, src unsafe.Pointer) {
// typedmemmovepartial is like typedmemmove but assumes that
// dst and src point off bytes into the value and only copies size bytes.
// off must be a multiple of sys.PtrSize.
//go:linkname reflect_typedmemmovepartial reflect.typedmemmovepartial
func reflect_typedmemmovepartial(typ *_type, dst, src unsafe.Pointer, off, size uintptr) {
if writeBarrier.needed && typ.ptrdata != 0 && size >= sys.PtrSize {
// Pointer-align start address for bulk barrier.
adst, asrc, asize := dst, src, size
ptrdata := typ.ptrdata
if ptrdata > off {
ptrdata -= off
} else {
ptrdata = 0
if writeBarrier.needed && typ.ptrdata > off && size >= sys.PtrSize {
if off&(sys.PtrSize-1) != 0 {
panic("reflect: internal error: misaligned offset")
}
if frag := -off & (sys.PtrSize - 1); frag != 0 {
adst = add(dst, frag)
asrc = add(src, frag)
asize -= frag
if ptrdata > frag {
ptrdata -= frag
} else {
ptrdata = 0
}
pwsize := alignDown(size, sys.PtrSize)
if poff := typ.ptrdata - off; pwsize > poff {
pwsize = poff
}
pwsize := asize &^ (sys.PtrSize - 1)
if pwsize > ptrdata {
pwsize = ptrdata
}
bulkBarrierPreWrite(uintptr(adst), uintptr(asrc), pwsize)
bulkBarrierPreWrite(uintptr(dst), uintptr(src), pwsize)
}
memmove(dst, src, size)