Proof with (try discriminate).
intros. unfold is_intconst in *.
destruct a... destruct o... inv H. inv H0. destruct vl; inv H5. auto.
Qed.

Theorem eval_modsimm:
forall le e1 x n2 z,
eval_expr ge sp e m le e1 x ->
Val.mods x (Vint n2) = Some z ->
exists v, eval_expr ge sp e m le (modsimm e1 n2) v /\ Val.lessdef z v.