Commit 42dfffc9 authored by Ralf Jung's avatar Ralf Jung

add a strong form of atomicity, for weak forms of weakest-pre

parent 180cd032
......@@ -52,9 +52,15 @@ Section language.
Definition irreducible (e : expr Λ) (σ : state Λ) :=
e' σ' efs, ¬prim_step e σ e' σ' efs.
(* This (weak) form of atomicity is enough to open invariants when WP is safe,
i.e., programs never can get stuck. *)
Definition atomic (e : expr Λ) : Prop :=
σ e' σ' efs, prim_step e σ e' σ' efs irreducible e' σ'.
(* To open invariants with unsafe WP, we need a stronger form of atomicity. *)
Definition strongly_atomic (e : expr Λ) : Prop :=
σ e' σ' efs, prim_step e σ e' σ' efs is_Some (to_val e').
Inductive step (ρ1 ρ2 : cfg Λ) : Prop :=
| step_atomic e1 σ1 e2 σ2 efs t1 t2 :
ρ1 = (t1 ++ e1 :: t2, σ1)
......@@ -74,6 +80,10 @@ Section language.
Global Instance of_val_inj : Inj (=) (=) (@of_val Λ).
Proof. by intros v v' Hv; apply (inj Some); rewrite -!to_of_val Hv. Qed.
Lemma strongly_atomic_atomic e :
strongly_atomic e atomic e.
Proof. unfold strongly_atomic, atomic. eauto using val_irreducible. Qed.
Lemma reducible_fill `{LanguageCtx Λ K} e σ :
to_val e = None reducible (K e) σ reducible e σ.
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