// Returns 0,0 if no such decomposition of v exists.
func immrot2a(v uint32) (uint32, uint32) {
	for i := uint(1); i < 32; i++ {
		m := uint32(1<<i - 1)
		if x, y := immrot(v&m), immrot(v&^m); x != 0 && y != 0 {
			return uint32(x), uint32(y)
		}
	}
	// TODO: handle some more cases, like where
	// the wraparound from the rotate could help.
	return 0, 0
}