Open Scope pred.
Section estep.
Variable X:Type.
Variable x:X.
Inductive estep : program X -> store -> list (instr X) -> store -> list (instr X) -> Prop :=
| estep_assert : forall p r i stk (P:X),
(*----------------------------------------------------*)
estep p r ((instr_assert P ;; i) :: stk) r (i :: stk)
| estep_getlabel: forall p r l v i stk,
(*----------------------------------------------------*)
estep p r ((instr_getlabel l v ;; i) :: stk) (r#v <- (value_label l)) (i :: stk)
| estep_fetch_field_0: forall p r v1 v2 i a0 a1 stk,
r#v1 = Some (value_cons a0 a1) ->
(*----------------------------------------------------*)
estep p r ((instr_fetch_field v1 0 v2 ;; i) :: stk) (r#v2 <- a0) (i :: stk)
| estep_fetch_field_1: forall p r v1 v2 i a0 a1 stk,
r#v1 = Some (value_cons a0 a1) ->
(*----------------------------------------------------*)
estep p r ((instr_fetch_field v1 1 v2 ;; i) :: stk) (r#v2 <- a1) (i :: stk)
| estep_cons: forall p r v1 v2 v3 i a1 a2 stk,
r#v1 = Some a1 ->
r#v2 = Some a2 ->
(*----------------------------------------------------*)
estep p r ((instr_cons v1 v2 v3 ;; i) :: stk) (r#v3 <- (value_cons a1 a2)) (i :: stk)
| estep_seq: forall p r i1 i2 i3 stk,
(*----------------------------------------------------*)
estep p r (((i1 ;; i2) ;; i3) :: stk) r ((i1 ;; i2 ;; i3) :: stk)
| estep_if_nil1 : forall p r v i1 i2 i stk,
r#v = Some (value_label (L 0)) ->
(*----------------------------------------------------*)
estep p r ((instr_if_nil v i1 i2 ;; i) :: stk) r ((i1 ;; i) :: stk)
| estep_if_nil2 : forall p r v i1 i2 i a1 a2 stk,
r#v = Some (value_cons a1 a2) ->
(*----------------------------------------------------*)
estep p r ((instr_if_nil v i1 i2 ;; i) :: stk) r ((i2 ;; i) :: stk)
| estep_call : forall p r v l i i' stk,
r#v = Some (value_label l) ->
p#l = Some i' ->
(*----------------------------------------------------*)
estep p r ((instr_call v ;; i) :: stk) r ((i' ;; instr_assert x) :: i :: stk)
| estep_return : forall p r stk i,
(*----------------------------------------------------*)
estep p r ((instr_return ;; i) :: stk) r stk.
Inductive estepstar : program X -> store -> list (instr X) -> store -> list (instr X) ->  Prop :=
| estepstar_O: forall p s i, estepstar p s i s i
| estepstar_S: forall p s i s' i' s'' i'',
estep p s i s' i' ->
estepstar p s' i' s'' i'' ->
estepstar p s i s'' i''.
Definition eventually_ehalts (p:program X) (r:store) (s:list (instr X)) : Prop :=
exists r', estepstar p r s r' nil.
Definition erase_instr : instruction -> instr X :=
fmap_instr (fun _ => x).
Definition erase_prog := map_fmap _ _ erase_instr.

Theorem erase_step : forall p p' n r r' s s',
step (K.squash (n,p)) p' r s r' s' ->
estep (erase_prog p) r (List.map erase_instr s) r' (List.map erase_instr s') /\
exists n', p' = K.squash (n',p).