func (re *Regexp) put(m *machine) {
	m.re = nil
	m.p = nil
	m.inputs.clear()
	matchPool[re.mpool].Put(m)
}

// minInputLen walks the regexp to find the minimum length of any matchable input.
func minInputLen(re *syntax.Regexp) int {
	switch re.Op {
	default:
		return 0
	case syntax.OpAnyChar, syntax.OpAnyCharNotNL, syntax.OpCharClass:
		return 1
	case syntax.OpLiteral:
		l := 0