cmd/compile: add Nodes.Prepend helper method

Prepared with gofmt -r.

Change-Id: Ib9f224cc20353acd9c5850dead1a2d32ca5427d3
Reviewed-on: https://go-review.googlesource.com/29165
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/compile/internal/gc/order.go

@@ -676,7 +676,7 @@ func orderstmt(n *Node, order *Order) {
 		n.Left = orderexprinplace(n.Left, order)
 		var l []*Node
 		cleantempnopop(t, order, &l)
-		n.Nbody.Set(append(l, n.Nbody.Slice()...))
+		n.Nbody.Prepend(l...)
 		orderblockNodes(&n.Nbody)
 		n.Right = orderstmtinplace(n.Right)
 		order.out = append(order.out, n)
@@ -690,10 +690,10 @@ func orderstmt(n *Node, order *Order) {
 		n.Left = orderexprinplace(n.Left, order)
 		var l []*Node
 		cleantempnopop(t, order, &l)
-		n.Nbody.Set(append(l, n.Nbody.Slice()...))
+		n.Nbody.Prepend(l...)
 		l = nil
 		cleantempnopop(t, order, &l)
-		n.Rlist.Set(append(l, n.Rlist.Slice()...))
+		n.Rlist.Prepend(l...)
 		poptemp(t, order)
 		orderblockNodes(&n.Nbody)
 		n.Rlist.Set(orderblock(n.Rlist))
@@ -917,7 +917,7 @@ func orderstmt(n *Node, order *Order) {
 		for _, n3 := range n.List.Slice() {
 			s := n3.Ninit.Slice()
 			cleantempnopop(t, order, &s)
-			n3.Nbody.Set(append(s, n3.Nbody.Slice()...))
+			n3.Nbody.Prepend(s...)
 			n3.Ninit.Set(nil)
 		}
 
@@ -1110,7 +1110,7 @@ func orderexpr(n *Node, order *Order, lhs *Node) *Node {
 		var s []*Node
 
 		cleantempnopop(mark, order, &s)
-		n.Right.Ninit.Set(append(s, n.Right.Ninit.Slice()...))
+		n.Right.Ninit.Prepend(s...)
 		n.Right = orderexprinplace(n.Right, order)
 
 	case OCALLFUNC,

src/cmd/compile/internal/gc/pgen.go

@@ -376,7 +376,7 @@ func compile(fn *Node) {
 			if t.Nname != nil {
 				n := Nod(OAS, t.Nname, nil)
 				n = typecheck(n, Etop)
-				Curfn.Nbody.Set(append([]*Node{n}, Curfn.Nbody.Slice()...))
+				Curfn.Nbody.Prepend(n)
 			}
 		}
 	}

src/cmd/compile/internal/gc/racewalk.go

@@ -69,7 +69,7 @@ func instrument(fn *Node) {
 		nodpc.Type = Types[TUINTPTR]
 		nodpc.Xoffset = int64(-Widthptr)
 		nd := mkcall("racefuncenter", nil, nil, &nodpc)
-		fn.Func.Enter.Set(append([]*Node{nd}, fn.Func.Enter.Slice()...))
+		fn.Func.Enter.Prepend(nd)
 		nd = mkcall("racefuncexit", nil, nil)
 		fn.Func.Exit.Append(nd)
 	}

src/cmd/compile/internal/gc/range.go

@@ -354,7 +354,7 @@ func walkrange(n *Node) {
 	n.Left = typecheck(n.Left, Erv)
 	n.Right = typecheck(n.Right, Etop)
 	typecheckslice(body, Etop)
-	n.Nbody.Set(append(body, n.Nbody.Slice()...))
+	n.Nbody.Prepend(body...)
 	n = walkstmt(n)
 
 	lineno = lno

src/cmd/compile/internal/gc/select.go

@@ -143,7 +143,7 @@ func walkselect(sel *Node) {
 				}
 
 				n.Op = OAS2
-				n.List.Set(append([]*Node{n.Left}, n.List.Slice()...))
+				n.List.Prepend(n.Left)
 				n.Rlist.Set1(n.Right)
 				n.Right = nil
 				n.Left = nil

src/cmd/compile/internal/gc/subr.go

@@ -2198,7 +2198,7 @@ func addinit(n *Node, init []*Node) *Node {
 		n.Typecheck = 1
 	}
 
-	n.Ninit.Set(append(init, n.Ninit.Slice()...))
+	n.Ninit.Prepend(init...)
 	n.Ullman = UINF
 	return n
 }

src/cmd/compile/internal/gc/swt.go

@@ -281,7 +281,7 @@ func (s *exprSwitch) walk(sw *Node) {
 	// handle default case
 	if nerrors == 0 {
 		cas = append(cas, clauses.defjmp)
-		sw.Nbody.Set(append(cas, sw.Nbody.Slice()...))
+		sw.Nbody.Prepend(cas...)
 		walkstmtlist(sw.Nbody.Slice())
 	}
 }
@@ -800,7 +800,7 @@ func (s *typeSwitch) walk(sw *Node) {
 	// handle default case
 	if nerrors == 0 {
 		cas = append(cas, def)
-		sw.Nbody.Set(append(cas, sw.Nbody.Slice()...))
+		sw.Nbody.Prepend(cas...)
 		sw.List.Set(nil)
 		walkstmtlist(sw.Nbody.Slice())
 	}

src/cmd/compile/internal/gc/syntax.go

@@ -583,15 +583,29 @@ func (n Nodes) Addr(i int) **Node {
 // Append appends entries to Nodes.
 // If a slice is passed in, this will take ownership of it.
 func (n *Nodes) Append(a ...*Node) {
+	if len(a) == 0 {
+		return
+	}
 	if n.slice == nil {
-		if len(a) > 0 {
-			n.slice = &a
-		}
+		n.slice = &a
 	} else {
 		*n.slice = append(*n.slice, a...)
 	}
 }
 
+// Prepend prepends entries to Nodes.
+// If a slice is passed in, this will take ownership of it.
+func (n *Nodes) Prepend(a ...*Node) {
+	if len(a) == 0 {
+		return
+	}
+	if n.slice == nil {
+		n.slice = &a
+	} else {
+		*n.slice = append(a, *n.slice...)
+	}
+}
+
 // AppendNodes appends the contents of *n2 to n, then clears n2.
 func (n *Nodes) AppendNodes(n2 *Nodes) {
 	switch {

src/cmd/compile/internal/gc/walk.go

@@ -669,7 +669,7 @@ opswitch:
 			// transformclosure already did all preparation work.
 
 			// Prepend captured variables to argument list.
-			n.List.Set(append(n.Left.Func.Enter.Slice(), n.List.Slice()...))
+			n.List.Prepend(n.Left.Func.Enter.Slice()...)
 
 			n.Left.Func.Enter.Set(nil)