Hint Rewrite Znth_nthi using (auto; omega) : sublist.
Hint Resolve Zland_in_range.

Lemma Sigma_1_eq: forall f_,
Sigma_1 f_ =
(Int.xor
(Int.xor
(Int.or (Int.shl f_ (Int.repr 26))
(Int.shru (Int.and f_ (Int.repr (-1)))
(Int.sub (Int.repr 32) (Int.repr 26))))
(Int.or (Int.shl f_ (Int.repr 21))
(Int.shru (Int.and f_ (Int.repr (-1)))
(Int.sub (Int.repr 32) (Int.repr 21)))))
(Int.or (Int.shl f_ (Int.repr 7))
(Int.shru (Int.and f_ (Int.repr (-1)))
(Int.sub (Int.repr 32) (Int.repr 7))))).