show that atomic_wp masks have the opposite monotonicity compared to HT

theories/bi/lib/atomic.v

@@ -226,6 +226,7 @@ Section lemmas.
 
   Local Existing Instance atomic_update_pre_mono.
 
+  (* Can't be in the section above as that fixes the parameters *)
   Global Instance atomic_acc_ne Eo Ei n :
     Proper (
         pointwise_relation TA (dist n) ==>
@@ -247,6 +248,18 @@ Section lemmas.
     rewrite atomic_update_eq /atomic_update_def /atomic_update_pre. solve_proper.
   Qed.
 
+  Lemma atomic_update_mask_weaken Eo1 Eo2 Ei α β Φ :
+    Eo1 ⊆ Eo2 →
+    atomic_update Eo1 Ei α β Φ -∗ atomic_update Eo2 Ei α β Φ.
+  Proof.
+    rewrite atomic_update_eq {2}/atomic_update_def /=.
+    iIntros (Heo) "HAU".
+    iApply (greatest_fixpoint_coind _ (λ _, atomic_update_def Eo1 Ei α β Φ)); last done.
+    iIntros "!# *". rewrite {1}/atomic_update_def /= greatest_fixpoint_unfold.
+    iApply make_laterable_wand. iIntros "!#".
+    iApply atomic_acc_mask_weaken. done.
+  Qed.
+
   (** The ellimination form: an atomic accessor *)
   Lemma aupd_aacc  Eo Ei α β Φ :
     atomic_update Eo Ei α β Φ -∗

theories/program_logic/atomic.v

@@ -99,6 +99,13 @@ Section lemmas.
   Notation iProp := (iProp Σ).
   Implicit Types (α : TA → iProp) (β : TA → TB → iProp) (f : TA → TB → val Λ).
 
+  Lemma atomic_wp_mask_weaken e Eo1 Eo2 α β f :
+    Eo2 ⊆ Eo1 → atomic_wp e Eo1 α β f -∗ atomic_wp e Eo2 α β f.
+  Proof.
+    iIntros (HEo) "Hwp". iIntros (Φ) "AU". iApply "Hwp".
+    iApply atomic_update_mask_weaken; last done. done.
+  Qed.
+
   (* Atomic triples imply sequential triples if the precondition is laterable. *)
   Lemma atomic_wp_seq e Eo α β f {HL : ∀.. x, Laterable (α x)} :
     atomic_wp e Eo α β f -∗