Fixpoint int_of_one_bits' (l: list Int.int) : int :=
match l with
| nil => zero
| a :: b => add (shl' one a) (int_of_one_bits' b)
end.

Lemma is_power2'_correct:
forall n logn,
is_power2' n = Some logn ->
unsigned n = two_p (Int.unsigned logn).