(** * Additional syntactic properties *)
(** We now show an additional property of the sequence of moves generated by [parmove mu]: any such move [s -> d] is either already present in [mu], or of the form [temp s -> d] or [s -> temp s] for some [s -> d] in [mu].  This syntactic property is useful to show that [parmove] preserves register classes, for instance. *)
Section PROPERTIES.
Variable initial_move: moves.
Inductive wf_move: reg -> reg -> Prop :=
| wf_move_same: forall s d,
In (s, d) initial_move -> wf_move s d
| wf_move_temp_left: forall s d,
wf_move s d -> wf_move (temp s) d
| wf_move_temp_right: forall s d,
wf_move s d -> wf_move s (temp s).
Definition wf_moves (m: moves) : Prop :=
forall s d, In (s, d) m -> wf_move s d.

Lemma wf_moves_cons: forall s d m,
wf_moves ((s, d) :: m) <-> wf_move s d /\ wf_moves m.