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runtime: use typedmemclr for typed memory

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The hybrid barrier requires distinguishing typed and untyped memory
even when zeroing because the *current* contents of the memory matters
even when overwriting.

This commit introduces runtime.typedmemclr and runtime.memclrHasPointers
as a typed memory clearing functions parallel to runtime.typedmemmove.
Currently these simply call memclr, but with the hybrid barrier we'll
need to shade any pointers we're overwriting. These will provide us
with the necessary hooks to do so.

Updates #17503.

Change-Id: I74478619f8907825898092aaa204d6e4690f27e6
Reviewed-on: https://go-review.googlesource.com/31366
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
This commit is contained in:
Austin Clements 2016-10-17 17:00:05 -04:00
parent a475a38a3d
commit aa581f5157
7 changed files with 53 additions and 10 deletions
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18
src/runtime/hashmap.go
View file

@ -637,9 +637,17 @@ func mapdelete(t *maptype, h *hmap, key unsafe.Pointer) {
if !alg.equal(key, k2) {
continue
}
memclr(k, uintptr(t.keysize))
if t.indirectkey {
*(*unsafe.Pointer)(k) = nil
} else {
typedmemclr(t.key, k)
}
v := unsafe.Pointer(uintptr(unsafe.Pointer(b)) + dataOffset + bucketCnt*uintptr(t.keysize) + i*uintptr(t.valuesize))
memclr(v, uintptr(t.valuesize))
if t.indirectvalue {
*(*unsafe.Pointer)(v) = nil
} else {
typedmemclr(t.elem, v)
}
b.tophash[i] = empty
h.count--
goto done
@ -1079,7 +1087,11 @@ func evacuate(t *maptype, h *hmap, oldbucket uintptr) {
b = (*bmap)(add(h.oldbuckets, oldbucket*uintptr(t.bucketsize)))
// Preserve b.tophash because the evacuation
// state is maintained there.
memclr(add(unsafe.Pointer(b), dataOffset), uintptr(t.bucketsize)-dataOffset)
if t.bucket.kind&kindNoPointers == 0 {
memclrHasPointers(add(unsafe.Pointer(b), dataOffset), uintptr(t.bucketsize)-dataOffset)
} else {
memclr(add(unsafe.Pointer(b), dataOffset), uintptr(t.bucketsize)-dataOffset)
}
}
}