runtime/internal/atomic: add write barrier-enabled pointer atomics

UnsafePointer.Store, UnsafePointer.CompareAndSwap were missing,
although .StoreNoWB and .CompareAndSwapNoWB existed.
Same for Pointer[T}.

Do the linkname tricks necessary to add those methods.

Change-Id: I925ee27673288accb15ebe93898f9eb01ab46a98
Reviewed-on: https://go-review.googlesource.com/c/go/+/443379
Auto-Submit: Russ Cox <rsc@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/src/runtime/atomic_pointer.go b/src/runtime/atomic_pointer.go
index b8f0c22c63..25e0e651b4 100644
--- a/src/runtime/atomic_pointer.go
+++ b/src/runtime/atomic_pointer.go
@@ -35,6 +35,27 @@ func atomicstorep(ptr unsafe.Pointer, new unsafe.Pointer) {
 	atomic.StorepNoWB(noescape(ptr), new)
 }
 
+// atomic_storePointer is the implementation of runtime/internal/UnsafePointer.Store
+// (like StoreNoWB but with the write barrier).
+//
+//go:nosplit
+//go:linkname atomic_storePointer runtime/internal/atomic.storePointer
+func atomic_storePointer(ptr *unsafe.Pointer, new unsafe.Pointer) {
+	atomicstorep(unsafe.Pointer(ptr), new)
+}
+
+// atomic_casPointer is the implementation of runtime/internal/UnsafePointer.CompareAndSwap
+// (like CompareAndSwapNoWB but with the write barrier).
+//
+//go:nosplit
+//go:linkname atomic_casPointer runtime/internal/atomic.casPointer
+func atomic_casPointer(ptr *unsafe.Pointer, old, new unsafe.Pointer) bool {
+	if writeBarrier.enabled {
+		atomicwb(ptr, new)
+	}
+	return atomic.Casp1(ptr, old, new)
+}
+
 // Like above, but implement in terms of sync/atomic's uintptr operations.
 // We cannot just call the runtime routines, because the race detector expects
 // to be able to intercept the sync/atomic forms but not the runtime forms.