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

Theorem eval_modu: forall le a b x y z, eval_expr ge sp e m le a x -> eval_expr ge sp e m le b y -> Val.modu x y = Some z -> exists v, eval_expr ge sp e m le (modu a b) v /\ Val.lessdef z v.