(** The simulation diagram. *)
Fixpoint seq_left_depth (s: Csharpminor.stmt) : nat :=
match s with
| Csharpminor.Sseq s1 s2 => S (seq_left_depth s1)
| _ => O
end.
Definition measure (S: Csharpminor.state) : nat :=
match S with
| Csharpminor.State fn s k e le m => seq_left_depth s
| _ => O
end.

Lemma transl_step_correct:
forall S1 t S2, Csharpminor.step ge S1 t S2 ->
forall T1, match_states S1 T1 ->
(exists T2, plus step tge T1 t T2 /\ match_states S2 T2)
\/ (measure S2 < measure S1 /\ t = E0 /\ match_states S2 T1)%nat.