[Ada] Implement new legality rules introduced in C.6(13) by AI12-0128

2019-12-16  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* doc/gnat_rm/implementation_defined_pragmas.rst (VFA): Document
	extension of the no-aliasing rule to any subcomponent.
	* freeze.adb (Freeze_Object_Declaration): Small comment tweak.
	(Freeze_Record_Type): Do not deal with delayed aspect
	specifications for components here but...
	(Freeze_Entity): ...here instead.
	* sem_ch12.adb (Instantiate_Object): Improve wording of errors
	given for legality rules in C.6(12) and implement the new rule
	in C.6(13).
	* sem_res.adb (Resolve_Actuals): Likewise.
	* sem_prag.adb (Check_Atomic_VFA): New procedure implementing
	the new legality rules in C.6(13).
	(Process_Atomic_Independent_Shared_Volatile): Call
	Check_Atomic_VFA to check the legality rules.  Factor out code
	marking types into...
	(Mark_Type): ...this new procedure.
	(Check_VFA_Conflicts): Do not check the legality rules here.
	(Pragma_Atomic_Components): Call Check_Atomic_VFA on component
	type.
	* sem_util.ads (Is_Subcomponent_Of_Atomic_Object): Declare.
	* sem_util.adb (Is_Subcomponent_Of_Atomic_Object): New
	predicate.
	* gnat_rm.texi: Regenerate.

From-SVN: r279412

1 files changed, 24 insertions, 7 deletions

diff --git a/gcc/ada/sem_ch12.adb b/gcc/ada/sem_ch12.adb
index 6932368..d405297 100644
--- a/gcc/ada/sem_ch12.adb
+++ b/gcc/ada/sem_ch12.adb
@@ -11111,19 +11111,36 @@ package body Sem_Ch12 is
 
          Note_Possible_Modification (Actual, Sure => True);
 
-         --  Check for instantiation of atomic/volatile actual for
-         --  non-atomic/volatile formal (RM C.6 (12)).
+         --  Check for instantiation with atomic/volatile object actual for
+         --  nonatomic/nonvolatile formal (RM C.6 (12)).
 
          if Is_Atomic_Object (Actual) and then not Is_Atomic (Orig_Ftyp) then
-            Error_Msg_N
-              ("cannot instantiate non-atomic formal object "
-               & "with atomic actual", Actual);
+            Error_Msg_NE
+              ("cannot instantiate nonatomic formal & of mode in out",
+               Actual, Gen_Obj);
+            Error_Msg_N ("\with atomic object actual (RM C.6(12))", Actual);
 
          elsif Is_Volatile_Object (Actual) and then not Is_Volatile (Orig_Ftyp)
          then
+            Error_Msg_NE
+              ("cannot instantiate nonvolatile formal & of mode in out",
+               Actual, Gen_Obj);
+            Error_Msg_N ("\with volatile object actual (RM C.6(12))", Actual);
+         end if;
+
+         --  Check for instantiation on nonatomic subcomponent of an atomic
+         --  object in Ada 2020 (RM C.6 (13)).
+
+         if Ada_Version >= Ada_2020
+            and then Is_Subcomponent_Of_Atomic_Object (Actual)
+            and then not Is_Atomic_Object (Actual)
+         then
+            Error_Msg_NE
+              ("cannot instantiate formal & of mode in out with actual",
+               Actual, Gen_Obj);
             Error_Msg_N
-              ("cannot instantiate non-volatile formal object "
-               & "with volatile actual", Actual);
+              ("\nonatomic subcomponent of atomic object (RM C.6(13))",
+               Actual);
          end if;
 
       --  Formal in-parameter