Remark int64_shr'_div_two_p:
  forall x y, Int64.shr' x y = Int64.repr (Int64.signed x / two_p (Int.unsigned y)).

Theorem divls_mul_shift_1: forall x y m p, divls_mul_params (Int64.signed y) = Some(p, m) -> m < Int64.half_modulus -> 0 <= p < 64 /\ Int64.divs x y = Int64.add (Int64.shr' (Int64.mulhs x (Int64.repr m)) (Int.repr p)) (Int64.shru' x (Int.repr 63)).