diff --git a/src/cmd/compile/internal/deadcode/deadcode.go b/src/cmd/compile/internal/deadcode/deadcode.go
index 5453cfe396b..474532bc176 100644
--- a/src/cmd/compile/internal/deadcode/deadcode.go
+++ b/src/cmd/compile/internal/deadcode/deadcode.go
@@ -84,7 +84,9 @@ func stmts(nn *ir.Nodes) {
 			}
 		}
 
-		stmts(n.PtrInit())
+		if len(n.Init()) != 0 {
+			stmts(n.(ir.InitNode).PtrInit())
+		}
 		switch n.Op() {
 		case ir.OBLOCK:
 			n := n.(*ir.BlockStmt)
diff --git a/src/cmd/compile/internal/inline/inl.go b/src/cmd/compile/internal/inline/inl.go
index 31b97a37870..24fbe3dac03 100644
--- a/src/cmd/compile/internal/inline/inl.go
+++ b/src/cmd/compile/internal/inline/inl.go
@@ -639,7 +639,7 @@ func inlCallee(fn ir.Node) *ir.Func {
 	return nil
 }
 
-func inlParam(t *types.Field, as ir.Node, inlvars map[*ir.Name]*ir.Name) ir.Node {
+func inlParam(t *types.Field, as ir.InitNode, inlvars map[*ir.Name]*ir.Name) ir.Node {
 	if t.Nname == nil {
 		return ir.BlankNode
 	}
@@ -741,7 +741,7 @@ func mkinlcall(n *ir.CallExpr, fn *ir.Func, maxCost int32, inlMap map[*ir.Func]b
 		callee := n.X
 		for callee.Op() == ir.OCONVNOP {
 			conv := callee.(*ir.ConvExpr)
-			ninit.Append(conv.PtrInit().Take()...)
+			ninit.Append(ir.TakeInit(conv)...)
 			callee = conv.X
 		}
 		if callee.Op() != ir.ONAME && callee.Op() != ir.OCLOSURE && callee.Op() != ir.OMETHEXPR {
diff --git a/src/cmd/compile/internal/ir/mini.go b/src/cmd/compile/internal/ir/mini.go
index 92701326216..93aa15abece 100644
--- a/src/cmd/compile/internal/ir/mini.go
+++ b/src/cmd/compile/internal/ir/mini.go
@@ -80,13 +80,7 @@ func (n *miniNode) SetDiag(x bool) { n.bits.set(miniDiag, x) }
 
 // Empty, immutable graph structure.
 
-func (n *miniNode) Init() Nodes     { return Nodes{} }
-func (n *miniNode) PtrInit() *Nodes { return &immutableEmptyNodes }
-func (n *miniNode) SetInit(x Nodes) {
-	if x != nil {
-		panic(n.no("SetInit"))
-	}
-}
+func (n *miniNode) Init() Nodes { return Nodes{} }
 
 // Additional functionality unavailable.
 
diff --git a/src/cmd/compile/internal/ir/node.go b/src/cmd/compile/internal/ir/node.go
index 9536503085b..9945cc987ac 100644
--- a/src/cmd/compile/internal/ir/node.go
+++ b/src/cmd/compile/internal/ir/node.go
@@ -34,8 +34,6 @@ type Node interface {
 	// Abstract graph structure, for generic traversals.
 	Op() Op
 	Init() Nodes
-	PtrInit() *Nodes
-	SetInit(x Nodes)
 
 	// Fields specific to certain Ops only.
 	Type() *types.Type
@@ -90,6 +88,20 @@ func MayBeShared(n Node) bool {
 	return false
 }
 
+type InitNode interface {
+	Node
+	PtrInit() *Nodes
+	SetInit(x Nodes)
+}
+
+func TakeInit(n Node) Nodes {
+	init := n.Init()
+	if len(init) != 0 {
+		n.(InitNode).SetInit(nil)
+	}
+	return init
+}
+
 //go:generate stringer -type=Op -trimprefix=O node.go
 
 type Op uint8
@@ -311,35 +323,15 @@ const (
 // a slice to save space.
 type Nodes []Node
 
-// immutableEmptyNodes is an immutable, empty Nodes list.
-// The methods that would modify it panic instead.
-var immutableEmptyNodes = Nodes{}
-
-func (n *Nodes) mutate() {
-	if n == &immutableEmptyNodes {
-		panic("immutable Nodes.Set")
-	}
-}
-
 // Set sets n to a slice.
 // This takes ownership of the slice.
-func (n *Nodes) Set(s []Node) {
-	if n == &immutableEmptyNodes {
-		if len(s) == 0 {
-			// Allow immutableEmptyNodes.Set(nil) (a no-op).
-			return
-		}
-		n.mutate()
-	}
-	*n = s
-}
+func (n *Nodes) Set(s []Node) { *n = s }
 
 // Append appends entries to Nodes.
 func (n *Nodes) Append(a ...Node) {
 	if len(a) == 0 {
 		return
 	}
-	n.mutate()
 	*n = append(*n, a...)
 }
 
@@ -349,7 +341,6 @@ func (n *Nodes) Prepend(a ...Node) {
 	if len(a) == 0 {
 		return
 	}
-	n.mutate()
 	*n = append(a, *n...)
 }
 
@@ -544,15 +535,16 @@ func SetPos(n Node) src.XPos {
 
 // The result of InitExpr MUST be assigned back to n, e.g.
 // 	n.Left = InitExpr(init, n.Left)
-func InitExpr(init []Node, n Node) Node {
+func InitExpr(init []Node, expr Node) Node {
 	if len(init) == 0 {
-		return n
+		return expr
 	}
-	if MayBeShared(n) {
+
+	n, ok := expr.(InitNode)
+	if !ok || MayBeShared(n) {
 		// Introduce OCONVNOP to hold init list.
-		old := n
-		n = NewConvExpr(base.Pos, OCONVNOP, nil, old)
-		n.SetType(old.Type())
+		n = NewConvExpr(base.Pos, OCONVNOP, nil, expr)
+		n.SetType(expr.Type())
 		n.SetTypecheck(1)
 	}
 
diff --git a/src/cmd/compile/internal/noder/noder.go b/src/cmd/compile/internal/noder/noder.go
index cc8a1c7c89a..948833f46e9 100644
--- a/src/cmd/compile/internal/noder/noder.go
+++ b/src/cmd/compile/internal/noder/noder.go
@@ -1200,7 +1200,7 @@ func (p *noder) stmtFall(stmt syntax.Stmt, fallOK bool) ir.Node {
 	panic("unhandled Stmt")
 }
 
-func (p *noder) assignList(expr syntax.Expr, defn ir.Node, colas bool) []ir.Node {
+func (p *noder) assignList(expr syntax.Expr, defn ir.InitNode, colas bool) []ir.Node {
 	if !colas {
 		return p.exprList(expr)
 	}
diff --git a/src/cmd/compile/internal/typecheck/typecheck.go b/src/cmd/compile/internal/typecheck/typecheck.go
index 0822a4624ca..0ee66df2cfc 100644
--- a/src/cmd/compile/internal/typecheck/typecheck.go
+++ b/src/cmd/compile/internal/typecheck/typecheck.go
@@ -914,7 +914,7 @@ func typecheck1(n ir.Node, top int) ir.Node {
 	// Each must execute its own return n.
 }
 
-func typecheckargs(n ir.Node) {
+func typecheckargs(n ir.InitNode) {
 	var list []ir.Node
 	switch n := n.(type) {
 	default:
diff --git a/src/cmd/compile/internal/walk/assign.go b/src/cmd/compile/internal/walk/assign.go
index c01079d236b..762baa0dd94 100644
--- a/src/cmd/compile/internal/walk/assign.go
+++ b/src/cmd/compile/internal/walk/assign.go
@@ -17,7 +17,7 @@ import (
 
 // walkAssign walks an OAS (AssignExpr) or OASOP (AssignOpExpr) node.
 func walkAssign(init *ir.Nodes, n ir.Node) ir.Node {
-	init.Append(n.PtrInit().Take()...)
+	init.Append(ir.TakeInit(n)...)
 
 	var left, right ir.Node
 	switch n.Op() {
@@ -124,7 +124,7 @@ func walkAssignDotType(n *ir.AssignListStmt, init *ir.Nodes) ir.Node {
 
 // walkAssignFunc walks an OAS2FUNC node.
 func walkAssignFunc(init *ir.Nodes, n *ir.AssignListStmt) ir.Node {
-	init.Append(n.PtrInit().Take()...)
+	init.Append(ir.TakeInit(n)...)
 
 	r := n.Rhs[0]
 	walkExprListSafe(n.Lhs, init)
@@ -142,7 +142,7 @@ func walkAssignFunc(init *ir.Nodes, n *ir.AssignListStmt) ir.Node {
 
 // walkAssignList walks an OAS2 node.
 func walkAssignList(init *ir.Nodes, n *ir.AssignListStmt) ir.Node {
-	init.Append(n.PtrInit().Take()...)
+	init.Append(ir.TakeInit(n)...)
 	walkExprListSafe(n.Lhs, init)
 	walkExprListSafe(n.Rhs, init)
 	return ir.NewBlockStmt(src.NoXPos, ascompatee(ir.OAS, n.Lhs, n.Rhs, init))
@@ -150,7 +150,7 @@ func walkAssignList(init *ir.Nodes, n *ir.AssignListStmt) ir.Node {
 
 // walkAssignMapRead walks an OAS2MAPR node.
 func walkAssignMapRead(init *ir.Nodes, n *ir.AssignListStmt) ir.Node {
-	init.Append(n.PtrInit().Take()...)
+	init.Append(ir.TakeInit(n)...)
 
 	r := n.Rhs[0].(*ir.IndexExpr)
 	walkExprListSafe(n.Lhs, init)
@@ -213,7 +213,7 @@ func walkAssignMapRead(init *ir.Nodes, n *ir.AssignListStmt) ir.Node {
 
 // walkAssignRecv walks an OAS2RECV node.
 func walkAssignRecv(init *ir.Nodes, n *ir.AssignListStmt) ir.Node {
-	init.Append(n.PtrInit().Take()...)
+	init.Append(ir.TakeInit(n)...)
 
 	r := n.Rhs[0].(*ir.UnaryExpr) // recv
 	walkExprListSafe(n.Lhs, init)
diff --git a/src/cmd/compile/internal/walk/builtin.go b/src/cmd/compile/internal/walk/builtin.go
index fe6045cbbd1..13837eeffc4 100644
--- a/src/cmd/compile/internal/walk/builtin.go
+++ b/src/cmd/compile/internal/walk/builtin.go
@@ -206,7 +206,7 @@ func walkCopy(n *ir.BinaryExpr, init *ir.Nodes, runtimecall bool) ir.Node {
 
 // walkDelete walks an ODELETE node.
 func walkDelete(init *ir.Nodes, n *ir.CallExpr) ir.Node {
-	init.Append(n.PtrInit().Take()...)
+	init.Append(ir.TakeInit(n)...)
 	map_ := n.Args[0]
 	key := n.Args[1]
 	map_ = walkExpr(map_, init)
diff --git a/src/cmd/compile/internal/walk/expr.go b/src/cmd/compile/internal/walk/expr.go
index 1fd09b42af4..7dfac300946 100644
--- a/src/cmd/compile/internal/walk/expr.go
+++ b/src/cmd/compile/internal/walk/expr.go
@@ -26,7 +26,7 @@ func walkExpr(n ir.Node, init *ir.Nodes) ir.Node {
 		return n
 	}
 
-	if init == n.PtrInit() {
+	if n, ok := n.(ir.InitNode); ok && init == n.PtrInit() {
 		// not okay to use n->ninit when walking n,
 		// because we might replace n with some other node
 		// and would lose the init list.
@@ -35,7 +35,7 @@ func walkExpr(n ir.Node, init *ir.Nodes) ir.Node {
 
 	if len(n.Init()) != 0 {
 		walkStmtList(n.Init())
-		init.Append(n.PtrInit().Take()...)
+		init.Append(ir.TakeInit(n)...)
 	}
 
 	lno := ir.SetPos(n)
@@ -359,7 +359,7 @@ func safeExpr(n ir.Node, init *ir.Nodes) ir.Node {
 
 	if len(n.Init()) != 0 {
 		walkStmtList(n.Init())
-		init.Append(n.PtrInit().Take()...)
+		init.Append(ir.TakeInit(n)...)
 	}
 
 	switch n.Op() {
diff --git a/src/cmd/compile/internal/walk/order.go b/src/cmd/compile/internal/walk/order.go
index e40c877ea93..679b795270e 100644
--- a/src/cmd/compile/internal/walk/order.go
+++ b/src/cmd/compile/internal/walk/order.go
@@ -466,8 +466,7 @@ func (o *orderState) init(n ir.Node) {
 		}
 		return
 	}
-	o.stmtList(n.Init())
-	n.PtrInit().Set(nil)
+	o.stmtList(ir.TakeInit(n))
 }
 
 // call orders the call expression n.
@@ -938,8 +937,7 @@ func (o *orderState) stmt(n ir.Node) {
 				if !ir.IsAutoTmp(recv.X) {
 					recv.X = o.copyExpr(recv.X)
 				}
-				init := *r.PtrInit()
-				r.PtrInit().Set(nil)
+				init := ir.TakeInit(r)
 
 				colas := r.Def
 				do := func(i int, t *types.Type) {
@@ -1000,8 +998,7 @@ func (o *orderState) stmt(n ir.Node) {
 
 			// TODO(mdempsky): Is this actually necessary?
 			// walkselect appears to walk Ninit.
-			cas.Body.Prepend(cas.Init()...)
-			cas.PtrInit().Set(nil)
+			cas.Body.Prepend(ir.TakeInit(cas)...)
 		}
 
 		o.out = append(o.out, n)
diff --git a/src/cmd/compile/internal/walk/range.go b/src/cmd/compile/internal/walk/range.go
index 49a69e97513..3092b71d729 100644
--- a/src/cmd/compile/internal/walk/range.go
+++ b/src/cmd/compile/internal/walk/range.go
@@ -210,7 +210,7 @@ func walkRange(nrange *ir.RangeStmt) ir.Node {
 		a.SetTypecheck(1)
 		a.Lhs = []ir.Node{hv1, hb}
 		a.Rhs = []ir.Node{ir.NewUnaryExpr(base.Pos, ir.ORECV, ha)}
-		*nfor.Cond.PtrInit() = []ir.Node{a}
+		nfor.Cond = ir.InitExpr([]ir.Node{a}, nfor.Cond)
 		if v1 == nil {
 			body = nil
 		} else {
diff --git a/src/cmd/compile/internal/walk/select.go b/src/cmd/compile/internal/walk/select.go
index 1c5e1d7e64a..c6e9b71384d 100644
--- a/src/cmd/compile/internal/walk/select.go
+++ b/src/cmd/compile/internal/walk/select.go
@@ -17,8 +17,7 @@ func walkSelect(sel *ir.SelectStmt) {
 		base.Fatalf("double walkselect")
 	}
 
-	init := sel.Init()
-	sel.PtrInit().Set(nil)
+	init := ir.TakeInit(sel)
 
 	init = append(init, walkSelectCases(sel.Cases)...)
 	sel.Cases = nil
@@ -45,8 +44,7 @@ func walkSelectCases(cases []*ir.CommClause) []ir.Node {
 		l := cas.Init()
 		if cas.Comm != nil { // not default:
 			n := cas.Comm
-			l = append(l, n.Init()...)
-			n.PtrInit().Set(nil)
+			l = append(l, ir.TakeInit(n)...)
 			switch n.Op() {
 			default:
 				base.Fatalf("select %v", n.Op())
@@ -171,8 +169,7 @@ func walkSelectCases(cases []*ir.CommClause) []ir.Node {
 	for _, cas := range cases {
 		ir.SetPos(cas)
 
-		init = append(init, cas.Init()...)
-		cas.PtrInit().Set(nil)
+		init = append(init, ir.TakeInit(cas)...)
 
 		n := cas.Comm
 		if n == nil { // default:
diff --git a/src/cmd/compile/internal/walk/stmt.go b/src/cmd/compile/internal/walk/stmt.go
index 8641a58e2e7..3440c665064 100644
--- a/src/cmd/compile/internal/walk/stmt.go
+++ b/src/cmd/compile/internal/walk/stmt.go
@@ -55,8 +55,7 @@ func walkStmt(n ir.Node) ir.Node {
 		if n.Typecheck() == 0 {
 			base.Fatalf("missing typecheck: %+v", n)
 		}
-		init := n.Init()
-		n.PtrInit().Set(nil)
+		init := ir.TakeInit(n)
 		n = walkExpr(n, &init)
 		if n.Op() == ir.ONAME {
 			// copy rewrote to a statement list and a temp for the length.
@@ -67,7 +66,7 @@ func walkStmt(n ir.Node) ir.Node {
 		if len(init) > 0 {
 			switch n.Op() {
 			case ir.OAS, ir.OAS2, ir.OBLOCK:
-				n.PtrInit().Prepend(init...)
+				n.(ir.InitNode).PtrInit().Prepend(init...)
 
 			default:
 				init.Append(n)
@@ -191,9 +190,8 @@ func walkDecl(n *ir.Decl) ir.Node {
 // walkFor walks an OFOR or OFORUNTIL node.
 func walkFor(n *ir.ForStmt) ir.Node {
 	if n.Cond != nil {
-		walkStmtList(n.Cond.Init())
-		init := n.Cond.Init()
-		n.Cond.PtrInit().Set(nil)
+		init := ir.TakeInit(n.Cond)
+		walkStmtList(init)
 		n.Cond = walkExpr(n.Cond, &init)
 		n.Cond = ir.InitExpr(init, n.Cond)
 	}
@@ -257,7 +255,7 @@ func walkIf(n *ir.IfStmt) ir.Node {
 func wrapCall(n *ir.CallExpr, init *ir.Nodes) ir.Node {
 	if len(n.Init()) != 0 {
 		walkStmtList(n.Init())
-		init.Append(n.PtrInit().Take()...)
+		init.Append(ir.TakeInit(n)...)
 	}
 
 	isBuiltinCall := n.Op() != ir.OCALLFUNC && n.Op() != ir.OCALLMETH && n.Op() != ir.OCALLINTER
diff --git a/src/cmd/compile/internal/walk/walk.go b/src/cmd/compile/internal/walk/walk.go
index 25f53a8e7c5..57c2d43753b 100644
--- a/src/cmd/compile/internal/walk/walk.go
+++ b/src/cmd/compile/internal/walk/walk.go
@@ -81,8 +81,7 @@ func walkRecv(n *ir.UnaryExpr) ir.Node {
 	if n.Typecheck() == 0 {
 		base.Fatalf("missing typecheck: %+v", n)
 	}
-	init := n.Init()
-	n.PtrInit().Set(nil)
+	init := ir.TakeInit(n)
 
 	n.X = walkExpr(n.X, &init)
 	call := walkExpr(mkcall1(chanfn("chanrecv1", 2, n.X.Type()), nil, &init, n.X, typecheck.NodNil()), &init)