Module Wordsize_8.
Definition wordsize := 8%nat.
Remark wordsize_not_zero: wordsize <> 0%nat.

Lemma bits_shru':
forall x y i,
0 <= i < zwordsize ->
testbit (shru' x y) i =
if zlt (i + Int.unsigned y) zwordsize then testbit x (i + Int.unsigned y) else false.