split; intros; induction v. simpl in *.
rewrite PTree.gempty in *. congruence.
simpl in *. destruct a. inv H. rewrite PTree.gsspec in *. if_tac in H0.
inv H0. auto. intuition.
inv H0.
simpl in *. destruct a. simpl in *. rewrite PTree.gsspec. destruct H0.
inv H0. if_tac. auto. intuition. inv H. if_tac. subst.
clear - H0 H3. rewrite in_map_iff in *. destruct H3. exists (i,ty). auto.
apply IHv; auto.
Qed.

Lemma func_tycontext_t_sound : func_tycontext_t_denote.
Definition cast_no_val_change (from: type)(to:type) : bool :=
match from, to with
| Tint _ _ _, Tint I32 _ _ => true
| Tpointer _ _, Tpointer _ _ =>
eqb_type from to ||
negb (eqb_type from int_or_ptr_type) &&
negb (eqb_type to int_or_ptr_type)
| Tfloat F64 _ , Tfloat F64 _ => true
| Tfloat F32 _ , Tfloat F32 _ => true
| _, _ => false
end.