[gcc r12-2032] [Ada] Adapt SPARK RM rule on non-effectively volatile abstract state

[gcc r12-2032] [Ada] Adapt SPARK RM rule on non-effectively volatile abstract state

[Pierre-Marie de Rodat]

https://gcc.gnu.org/g:902d7076663aff56198b81f8efa356c3e1024e80

commit r12-2032-g902d7076663aff56198b81f8efa356c3e1024e80
Author: Yannick Moy <moy@adacore.com>
Date:   Fri Apr 30 12:41:22 2021 +0200

    [Ada] Adapt SPARK RM rule on non-effectively volatile abstract state
    
    gcc/ada/
    
            * sem_prag.adb (Analyze_Global_Item): Adapt to update SPARK RM
            rule.

Diff:
---
 gcc/ada/sem_prag.adb | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/gcc/ada/sem_prag.adb b/gcc/ada/sem_prag.adb
index fa63fdae730..0efdceff5e7 100644
--- a/gcc/ada/sem_prag.adb
+++ b/gcc/ada/sem_prag.adb
@@ -2433,10 +2433,13 @@ package body Sem_Prag is
                      SPARK_Msg_N ("\use its constituents instead", Item);
                      return;
 
-                  --  An external state cannot appear as a global item of a
-                  --  nonvolatile function (SPARK RM 7.1.3(8)).
+                  --  An external state which has Async_Writers or
+                  --  Effective_Reads enabled cannot appear as a global item
+                  --  of a nonvolatile function (SPARK RM 7.1.3(8)).
 
                   elsif Is_External_State (Item_Id)
+                    and then (Async_Writers_Enabled (Item_Id)
+                               or else Effective_Reads_Enabled (Item_Id))
                     and then Ekind (Spec_Id) in E_Function | E_Generic_Function
                     and then not Is_Volatile_Function (Spec_Id)
                   then