cmd/compile: mark memclrHasPointers calls as write barriers

There are two places where the compiler generates memclrHasPointers
calls. These are effectively write barriers, but the compiler doesn't
currently record them as such in the function. As a result code like

  for i := range a {
    a[i] = nil
  }

inserts a write barrier for the assignment to a[i], but the compiler
doesn't report this. Hence, it's not reported in the -d=wb output, and
it's not checked against //go:nowritebarrier annotations.

Change-Id: I40299ebc9824f05cf516cba494d4c086b80ffb53
Reviewed-on: https://go-review.googlesource.com/c/152722
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

diff --git a/src/cmd/compile/internal/gc/range.go b/src/cmd/compile/internal/gc/range.go
index bf30d9388ec55f4385cf0fb1bff6c9b4f4e30760..cbe69a1ebc16fdff770fd4637bbc90dc1671bbce 100644 (file)
--- a/src/cmd/compile/internal/gc/range.go
+++ b/src/cmd/compile/internal/gc/range.go
@@ -588,6 +588,7 @@ func arrayClear(n, v1, v2, a *Node) bool {
        var fn *Node
        if types.Haspointers(a.Type.Elem()) {
                // memclrHasPointers(hp, hn)
+               Curfn.Func.setWBPos(stmt.Pos)
                fn = mkcall("memclrHasPointers", nil, nil, hp, hn)
        } else {
                // memclrNoHeapPointers(hp, hn)

diff --git a/src/cmd/compile/internal/gc/walk.go b/src/cmd/compile/internal/gc/walk.go
index 528aacb213c4b4ef9e0dd7ea1a7671a0175e4869..b84bc26e04a720a7ef49a10d827a1bc304e923de 100644 (file)
--- a/src/cmd/compile/internal/gc/walk.go
+++ b/src/cmd/compile/internal/gc/walk.go
@@ -2860,6 +2860,7 @@ func extendslice(n *Node, init *Nodes) *Node {
        hasPointers := types.Haspointers(elemtype)
        if hasPointers {
                clrname = "memclrHasPointers"
+               Curfn.Func.setWBPos(n.Pos)
        }
 
        var clr Nodes