Set Bullet Behavior "Strict Subproofs".
Instance CompSpecs : compspecs. make_compspecs prog. Defined.
Definition Vprog : varspecs. mk_varspecs prog. Defined.
Definition release2_spec := DECLARE _release2 release2_spec.
Definition freelock2_spec := DECLARE _freelock2 (freelock2_spec _).
Definition spawn_spec := DECLARE _spawn spawn_spec.
Definition integer_hash_spec :=
DECLARE _integer_hash
WITH i : Z
PRE [ _i OF tint ]
PROP () LOCAL (temp _i (vint i)) SEP ()
POST [ tint ]
PROP () LOCAL (temp ret_temp (vint (i * 654435761))) SEP ().
(* One might think it should just return an unknown number, but in fact it needs to follow a known hash function at the logic level to be useful. *)
Definition tentry := Tstruct _entry noattr.
Instance hf1 : hash_fun := { size := 16384; hash i := (i * 654435761) mod 16384 }.
Opaque upto.
Ltac cancel_for_forward_call ::= repeat (rewrite ?sepcon_andp_prop', ?sepcon_andp_prop);
repeat (apply andp_right; [auto; apply prop_right; auto|]); fast_cancel.
Ltac entailer_for_return ::= go_lower; entailer'.

Lemma incr_invariant : forall (P : _ -> _ -> Prop) i1 i key (h h' : list (hist * hist)) h1
(Hi1 : i1 = (i + hash key) mod size) (Hh' : Zlength h' = size) (Hinv : forall j,
(In j (indices (hash key) (i + hash key)) -> P (Znth j h ([], [])) (Znth j h' ([], []))) /\
(~In j (indices (hash key) (i + hash key)) -> Znth j h' ([], []) = Znth j h ([], [])))
(HP : P (Znth i1 h ([], [])) h1) (Hi : i mod size < size - 1) j,
(In j (indices (hash key) ((i + 1) + hash key)) -> P (Znth j h ([], [])) (Znth j (upd_Znth i1 h' h1) ([], []))) /\
(~In j (indices (hash key) ((i + 1) + hash key)) -> Znth j (upd_Znth i1 h' h1) ([], []) = Znth j h ([], [])).