elemtype := s.Type().Elem()

	// Decompose slice.
	oldPtr := ir.NewUnaryExpr(base.Pos, ir.OSPTR, s)
	oldLen := ir.NewUnaryExpr(base.Pos, ir.OLEN, s)
	oldCap := ir.NewUnaryExpr(base.Pos, ir.OCAP, s)

	// Number of elements we are adding
	num := ir.NewUnaryExpr(base.Pos, ir.OLEN, l2)

	// newLen := oldLen + num

	l = append(l, ir.NewAssignStmt(base.Pos, nr, n.Y))

	nfrm := ir.NewUnaryExpr(base.Pos, ir.OSPTR, nr)
	nto := ir.NewUnaryExpr(base.Pos, ir.OSPTR, nl)

	nlen := typecheck.TempAt(base.Pos, ir.CurFunc, types.Types[types.TINT])

	// n = len(to)
	l = append(l, ir.NewAssignStmt(base.Pos, nlen, ir.NewUnaryExpr(base.Pos, ir.OLEN, nl)))

	// if n > len(frm) { n = len(frm) }

	if c != n || len(init) != 0 {
		base.Fatalf("backingArrayPtrLen not cheap: %v", n)
	}
	ptr = ir.NewUnaryExpr(base.Pos, ir.OSPTR, n)
	if n.Type().IsString() {
		ptr.SetType(types.Types[types.TUINT8].PtrTo())
	} else {
		ptr.SetType(n.Type().Elem().PtrTo())
	}
	ptr.SetTypecheck(1)
	length = ir.NewUnaryExpr(base.Pos, ir.OLEN, n)
	length.SetType(types.Types[types.TINT])
	length.SetTypecheck(1)
	return ptr, length

	// Get interface descriptor word.
	// For empty interfaces this will be the type.
	// For non-empty interfaces this will be the itab.
	srcItab := ir.NewUnaryExpr(base.Pos, ir.OITAB, s.srcName)
	srcData := ir.NewUnaryExpr(base.Pos, ir.OIDATA, s.srcName)
	srcData.SetType(types.Types[types.TUINT8].PtrTo())
	srcData.SetTypecheck(1)

	// For empty interfaces, do:
	//     if e._type == nil {

	if wantABI != obj.ABIInternal {
		base.ErrorfAt(pos, 0, "internal/abi.FuncPC%s does not accept func expression, which is ABIInternal", wantABI)
	}
	var e Node = NewUnaryExpr(pos, OIDATA, n)
	e.SetType(types.Types[types.TUINTPTR].PtrTo())
	e.SetTypecheck(1)
	e = NewStarExpr(pos, e)
	e.SetType(types.Types[types.TUINTPTR])
	e.SetTypecheck(1)
	return e
}

			typecheckargs(n)
			fallthrough
		case ir.ONEW:
			arg, ok := needOneArg(n, "%v", n.Op())
			if !ok {
				n.SetType(nil)
				return n
			}
			u := ir.NewUnaryExpr(n.Pos(), l.BuiltinOp, arg)
			return typecheck(ir.InitExpr(n.Init(), u), top) // typecheckargs can add to old.Init

		case ir.OCOMPLEX, ir.OCOPY, ir.OUNSAFEADD, ir.OUNSAFESLICE, ir.OUNSAFESTRING:
			typecheckargs(n)