7 files changed, 23 insertions, 20 deletions
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 103a0f4cd6..95f753c167 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -136,11 +136,6 @@ func buildssa(fn *Node, worker int) *ssa.Func {
 	if fn.Func.Pragma&Nosplit != 0 {
 		s.f.NoSplit = true
 	}
-	defer func() {
-		if s.f.WBPos.IsKnown() {
-			fn.Func.WBPos = s.f.WBPos
-		}
-	}()
 	s.exitCode = fn.Func.Exit
 	s.panics = map[funcLine]*ssa.Block{}
 
@@ -5180,10 +5175,6 @@ func (e *ssafn) Debug_checknil() bool {
 	return Debug_checknil != 0
 }
 
-func (e *ssafn) Debug_wb() bool {
-	return Debug_wb != 0
-}
-
 func (e *ssafn) UseWriteBarrier() bool {
 	return use_writebarrier
 }
@@ -5205,6 +5196,10 @@ func (e *ssafn) Syslook(name string) *obj.LSym {
 	return nil
 }
 
+func (e *ssafn) SetWBPos(pos src.XPos) {
+	e.curfn.Func.setWBPos(pos)
+}
+
 func (n *Node) Typ() *types.Type {
 	return n.Type
 }
diff --git a/src/cmd/compile/internal/gc/syntax.go b/src/cmd/compile/internal/gc/syntax.go
index e18cdfef5d..e28f8a0df3 100644
--- a/src/cmd/compile/internal/gc/syntax.go
+++ b/src/cmd/compile/internal/gc/syntax.go
@@ -427,7 +427,7 @@ type Func struct {
 	Label int32 // largest auto-generated label in this function
 
 	Endlineno src.XPos
-	WBPos     src.XPos // position of first write barrier
+	WBPos     src.XPos // position of first write barrier; see SetWBPos
 
 	Pragma syntax.Pragma // go:xxx function annotations
 
@@ -484,6 +484,15 @@ func (f *Func) SetHasDefer(b bool)            { f.flags.set(funcHasDefer, b) }
 func (f *Func) SetNilCheckDisabled(b bool)    { f.flags.set(funcNilCheckDisabled, b) }
 func (f *Func) SetInlinabilityChecked(b bool) { f.flags.set(funcInlinabilityChecked, b) }
 
+func (f *Func) setWBPos(pos src.XPos) {
+	if Debug_wb != 0 {
+		Warnl(pos, "write barrier")
+	}
+	if !f.WBPos.IsKnown() {
+		f.WBPos = pos
+	}
+}
+
 type Op uint8
 
 // Node ops.
diff --git a/src/cmd/compile/internal/gc/walk.go b/src/cmd/compile/internal/gc/walk.go
index 65ca6cc27a..3139404b1e 100644
--- a/src/cmd/compile/internal/gc/walk.go
+++ b/src/cmd/compile/internal/gc/walk.go
@@ -2955,6 +2955,7 @@ func appendslice(n *Node, init *Nodes) *Node {
 		nptr1.SetSliceBounds(nod(OLEN, l1, nil), nil, nil)
 		nptr1.Etype = 1
 		nptr2 := l2
+		Curfn.Func.setWBPos(n.Pos)
 		fn := syslook("typedslicecopy")
 		fn = substArgTypes(fn, l1.Type, l2.Type)
 		var ln Nodes
@@ -3117,6 +3118,7 @@ func walkappend(n *Node, init *Nodes, dst *Node) *Node {
 //
 func copyany(n *Node, init *Nodes, runtimecall bool) *Node {
 	if types.Haspointers(n.Left.Type.Elem()) {
+		Curfn.Func.setWBPos(n.Pos)
 		fn := writebarrierfn("typedslicecopy", n.Left.Type, n.Right.Type)
 		return mkcall1(fn, n.Type, init, typename(n.Left.Type.Elem()), n.Left, n.Right)
 	}
diff --git a/src/cmd/compile/internal/ssa/config.go b/src/cmd/compile/internal/ssa/config.go
index c352219523..de3aadbbe5 100644
--- a/src/cmd/compile/internal/ssa/config.go
+++ b/src/cmd/compile/internal/ssa/config.go
@@ -88,7 +88,6 @@ type Logger interface {
 
 	// Forwards the Debug flags from gc
 	Debug_checknil() bool
-	Debug_wb() bool
 }
 
 type Frontend interface {
@@ -131,6 +130,10 @@ type Frontend interface {
 
 	// UseWriteBarrier returns whether write barrier is enabled
 	UseWriteBarrier() bool
+
+	// SetWBPos indicates that a write barrier has been inserted
+	// in this function at position pos.
+	SetWBPos(pos src.XPos)
 }
 
 // interface used to hold a *gc.Node (a stack variable).
diff --git a/src/cmd/compile/internal/ssa/export_test.go b/src/cmd/compile/internal/ssa/export_test.go
index ad69463bdd..d1d6831eb3 100644
--- a/src/cmd/compile/internal/ssa/export_test.go
+++ b/src/cmd/compile/internal/ssa/export_test.go
@@ -125,6 +125,8 @@ func (d DummyFrontend) Syslook(s string) *obj.LSym {
 func (DummyFrontend) UseWriteBarrier() bool {
 	return true // only writebarrier_test cares
 }
+func (DummyFrontend) SetWBPos(pos src.XPos) {
+}
 
 func (d DummyFrontend) Logf(msg string, args ...interface{}) { d.t.Logf(msg, args...) }
 func (d DummyFrontend) Log() bool                            { return true }
@@ -132,7 +134,6 @@ func (d DummyFrontend) Log() bool                            { return true }
 func (d DummyFrontend) Fatalf(_ src.XPos, msg string, args ...interface{}) { d.t.Fatalf(msg, args...) }
 func (d DummyFrontend) Warnl(_ src.XPos, msg string, args ...interface{})  { d.t.Logf(msg, args...) }
 func (d DummyFrontend) Debug_checknil() bool                               { return false }
-func (d DummyFrontend) Debug_wb() bool                                     { return false }
 
 var dummyTypes Types
 
diff --git a/src/cmd/compile/internal/ssa/func.go b/src/cmd/compile/internal/ssa/func.go
index 559f1d70e6..01966adb0f 100644
--- a/src/cmd/compile/internal/ssa/func.go
+++ b/src/cmd/compile/internal/ssa/func.go
@@ -44,8 +44,6 @@ type Func struct {
 	scheduled bool // Values in Blocks are in final order
 	NoSplit   bool // true if function is marked as nosplit.  Used by schedule check pass.
 
-	WBPos src.XPos // line number of first write barrier
-
 	// when register allocation is done, maps value ids to locations
 	RegAlloc []Location
 
diff --git a/src/cmd/compile/internal/ssa/writebarrier.go b/src/cmd/compile/internal/ssa/writebarrier.go
index 129a06eecb..60797158b3 100644
--- a/src/cmd/compile/internal/ssa/writebarrier.go
+++ b/src/cmd/compile/internal/ssa/writebarrier.go
@@ -226,12 +226,7 @@ func writebarrier(f *Func) {
 
 			if fn != nil {
 				// Note that we set up a writebarrier function call.
-				if !f.WBPos.IsKnown() {
-					f.WBPos = pos
-				}
-				if f.fe.Debug_wb() {
-					f.Warnl(pos, "write barrier")
-				}
+				f.fe.SetWBPos(pos)
 			}
 		}