(* Why isn't this automatic? *)
Instance zero_ord_preorder : RelationClasses.PreOrder zero_ord.
Instance table_incl_preorder : RelationClasses.PreOrder table_incl.

Lemma lock_struct_array : forall sh z (v : list val) p,
data_at sh (tarray (tptr (Tstruct _lock_t noattr)) z) v p =
data_at sh (tarray (tptr tlock) z) v p.