Fixpoint iterShr8 u n :=
  match n with O => u
   | S n' => Int.shru (iterShr8 u n') (Int.repr 8)
  end.

Lemma Zlor_Byteor b1 b2: Z.lor (Byte.unsigned b1) (Byte.unsigned b2) = Byte.unsigned (Byte.or b1 b2).