Remark int64_shru'_div_two_p:
forall x y, Int64.shru' x y = Int64.repr (Int64.unsigned x / two_p (Int.unsigned y)).

Theorem divlu_mul_shift:
forall x y m p,
divlu_mul_params (Int64.unsigned y) = Some(p, m) ->
0 <= p < 64 /\
Int64.divu x y = Int64.shru' (Int64.mulhu x (Int64.repr m)) (Int.repr p).