// callee args space for its use.
func (s *State) UseArgs(n int64) {
	if s.maxarg < n {
		s.maxarg = n
	}
}

// fieldIdx finds the index of the field referred to by the ODOT node n.
func fieldIdx(n *ir.SelectorExpr) int {
	t := n.X.Type()
	if !t.IsStruct() {
		panic("ODOT's LHS is not a struct")
	}

	for i, f := range t.Fields() {
		if f.Sym == n.Sel {