[Ada] Constants no longer synchronised if they are access-to-variable

[Pierre-Marie de Rodat]

Implement changes in SPARK RM 9(1): previously an object was
'synchronized' if it was a constant, now constants are only synchronized
if they are not of an access-to-variable type.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

        * sem_util.ads, sem_util.adb (Is_Access_Variable): New function.
        (Is_Synchronized_Object): Call new function when determining if
        a constant can be regarded as synchronized.
diff --git a/gcc/ada/sem_util.adb b/gcc/ada/sem_util.adb
--- a/gcc/ada/sem_util.adb
+++ b/gcc/ada/sem_util.adb
@@ -14337,6 +14337,16 @@ package body Sem_Util is
       return Nkind (Par) in N_Subprogram_Call;
    end Is_Anonymous_Access_Actual;
 
+   ------------------------
+   -- Is_Access_Variable --
+   ------------------------
+
+   function Is_Access_Variable (E : Entity_Id) return Boolean is
+   begin
+      return Is_Access_Object_Type (E)
+        and then not Is_Access_Constant (E);
+   end Is_Access_Variable;
+
    -----------------------------
    -- Is_Actual_Out_Parameter --
    -----------------------------
@@ -19149,9 +19159,12 @@ package body Sem_Util is
          then
             return True;
 
-         --  A constant is a synchronized object by default
+         --  A constant is a synchronized object by default, unless its type is
+         --  access-to-variable type.
 
-         elsif Ekind (Id) = E_Constant then
+         elsif Ekind (Id) = E_Constant
+           and then not Is_Access_Variable (Etype (Id))
+         then
             return True;
 
          --  A variable is a synchronized object if it is subject to pragma


diff --git a/gcc/ada/sem_util.ads b/gcc/ada/sem_util.ads
--- a/gcc/ada/sem_util.ads
+++ b/gcc/ada/sem_util.ads
@@ -1596,6 +1596,9 @@ package Sem_Util is
    --  True if E is the constructed wrapper for an access_to_subprogram
    --  type with Pre/Postconditions.
 
+   function Is_Access_Variable (E : Entity_Id) return Boolean;
+   --  Determines if type E is an access-to-variable
+
    function Is_Actual_In_Out_Parameter (N : Node_Id) return Boolean;
    --  Determines if N is an actual parameter of in-out mode in a subprogram
    --  call.
@@ -2166,7 +2169,7 @@ package Sem_Util is
    --  such, the object must be
    --    * Of a type that yields a synchronized object
    --    * An atomic object with enabled Async_Writers
-   --    * A constant
+   --    * A constant not of access-to-variable type
    --    * A variable subject to pragma Constant_After_Elaboration
 
    function Is_Synchronized_Tagged_Type (E : Entity_Id) return Boolean;