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

Lemma bits_shr':
forall x y i,
0 <= i < zwordsize ->
testbit (shr' x y) i =
testbit x (if zlt (i + Int.unsigned y) zwordsize then i + Int.unsigned y else zwordsize - 1).