diff --git a/src/cmd/compile/internal/walk/assign.go b/src/cmd/compile/internal/walk/assign.go
index 9350c389c16..9b09e097fac 100644
--- a/src/cmd/compile/internal/walk/assign.go
+++ b/src/cmd/compile/internal/walk/assign.go
@@ -157,7 +157,7 @@ func walkAssignMapRead(init *ir.Nodes, n *ir.AssignListStmt) ir.Node {
 	t := r.X.Type()
 
 	fast := mapfast(t)
-	key := mapKeyArg(fast, r, r.Index)
+	key := mapKeyArg(fast, r, r.Index, false)
 
 	// from:
 	//   a,b = m[i]
diff --git a/src/cmd/compile/internal/walk/builtin.go b/src/cmd/compile/internal/walk/builtin.go
index d0aaee03d59..b25627bd224 100644
--- a/src/cmd/compile/internal/walk/builtin.go
+++ b/src/cmd/compile/internal/walk/builtin.go
@@ -214,7 +214,7 @@ func walkDelete(init *ir.Nodes, n *ir.CallExpr) ir.Node {
 
 	t := map_.Type()
 	fast := mapfast(t)
-	key = mapKeyArg(fast, n, key)
+	key = mapKeyArg(fast, n, key, false)
 	return mkcall1(mapfndel(mapdelete[fast], t), nil, init, reflectdata.TypePtr(t), map_, key)
 }
 
diff --git a/src/cmd/compile/internal/walk/expr.go b/src/cmd/compile/internal/walk/expr.go
index 43201dbd3d4..4c1e7adddd7 100644
--- a/src/cmd/compile/internal/walk/expr.go
+++ b/src/cmd/compile/internal/walk/expr.go
@@ -723,21 +723,23 @@ func walkIndex(n *ir.IndexExpr, init *ir.Nodes) ir.Node {
 }
 
 // mapKeyArg returns an expression for key that is suitable to be passed
-// as the key argument for mapaccess and mapdelete functions.
+// as the key argument for runtime map* functions.
 // n is is the map indexing or delete Node (to provide Pos).
-// Note: this is not used for mapassign, which does distinguish pointer vs.
-// integer key.
-func mapKeyArg(fast int, n, key ir.Node) ir.Node {
-	switch fast {
-	case mapslow:
+func mapKeyArg(fast int, n, key ir.Node, assigned bool) ir.Node {
+	if fast == mapslow {
 		// standard version takes key by reference.
-		// order.expr made sure key is addressable.
+		// orderState.expr made sure key is addressable.
 		return typecheck.NodAddr(key)
+	}
+	if assigned {
+		// mapassign does distinguish pointer vs. integer key.
+		return key
+	}
+	// mapaccess and mapdelete don't distinguish pointer vs. integer key.
+	switch fast {
 	case mapfast32ptr:
-		// mapaccess and mapdelete don't distinguish pointer vs. integer key.
 		return ir.NewConvExpr(n.Pos(), ir.OCONVNOP, types.Types[types.TUINT32], key)
 	case mapfast64ptr:
-		// mapaccess and mapdelete don't distinguish pointer vs. integer key.
 		return ir.NewConvExpr(n.Pos(), ir.OCONVNOP, types.Types[types.TUINT64], key)
 	default:
 		// fast version takes key by value.
@@ -746,34 +748,27 @@ func mapKeyArg(fast int, n, key ir.Node) ir.Node {
 }
 
 // walkIndexMap walks an OINDEXMAP node.
+// It replaces m[k] with *map{access1,assign}(maptype, m, &k)
 func walkIndexMap(n *ir.IndexExpr, init *ir.Nodes) ir.Node {
-	// Replace m[k] with *map{access1,assign}(maptype, m, &k)
 	n.X = walkExpr(n.X, init)
 	n.Index = walkExpr(n.Index, init)
 	map_ := n.X
-	key := n.Index
 	t := map_.Type()
-	var call *ir.CallExpr
-	if n.Assigned {
-		// This m[k] expression is on the left-hand side of an assignment.
-		fast := mapfast(t)
-		if fast == mapslow {
-			// standard version takes key by reference.
-			// order.expr made sure key is addressable.
-			key = typecheck.NodAddr(key)
-		}
-		call = mkcall1(mapfn(mapassign[fast], t, false), nil, init, reflectdata.TypePtr(t), map_, key)
-	} else {
-		// m[k] is not the target of an assignment.
-		fast := mapfast(t)
-		key = mapKeyArg(fast, n, key)
-		if w := t.Elem().Size(); w <= zeroValSize {
-			call = mkcall1(mapfn(mapaccess1[fast], t, false), types.NewPtr(t.Elem()), init, reflectdata.TypePtr(t), map_, key)
-		} else {
-			z := reflectdata.ZeroAddr(w)
-			call = mkcall1(mapfn("mapaccess1_fat", t, true), types.NewPtr(t.Elem()), init, reflectdata.TypePtr(t), map_, key, z)
-		}
+	fast := mapfast(t)
+	key := mapKeyArg(fast, n, n.Index, n.Assigned)
+	args := []ir.Node{reflectdata.TypePtr(t), map_, key}
+
+	var mapFn ir.Node
+	switch {
+	case n.Assigned:
+		mapFn = mapfn(mapassign[fast], t, false)
+	case t.Elem().Size() > zeroValSize:
+		args = append(args, reflectdata.ZeroAddr(t.Elem().Size()))
+		mapFn = mapfn("mapaccess1_fat", t, true)
+	default:
+		mapFn = mapfn(mapaccess1[fast], t, false)
 	}
+	call := mkcall1(mapFn, nil, init, args...)
 	call.SetType(types.NewPtr(t.Elem()))
 	call.MarkNonNil() // mapaccess1* and mapassign always return non-nil pointers.
 	star := ir.NewStarExpr(base.Pos, call)