Proof with (try discriminate).
intros. unfold is_longconst in *. destruct Archi.splitlong.
eapply SplitLongproof.is_longconst_sound; eauto.
assert (a = Eop (Olongconst n) Enil).
{ destruct a... destruct o... destruct e0... congruence. }
subst a. InvEval. auto.
Qed.

Theorem eval_shllimm: forall n, unary_constructor_sound (fun e => shllimm e n) (fun v => Val.shll v (Vint n)).