[Ada] Subtype inherits Atomic flag from base type

2020-06-05  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* sem_ch3.adb (Analyze_Subtype_Declaration): For scalar types,
	and for subtype declarations without a constraint, subtype
	inherits Atomic flag from base type.

diff --git a/gcc/ada/sem_ch3.adb b/gcc/ada/sem_ch3.adb
index 3c65a340ff1ba4774eafdabb64b128a21a027856..4d6382e59d405ef7fae2490bf9d6ced9d00f3188 100644 (file)
--- a/gcc/ada/sem_ch3.adb
+++ b/gcc/ada/sem_ch3.adb
@@ -5804,6 +5804,15 @@ package body Sem_Ch3 is
          end if;
       end if;
 
+      --  If the base type is a scalar type, or else if there is no
+      --  constraint, the atomic flag is inherited by the subtype.
+
+      if Is_Scalar_Type (Id)
+        or else Is_Entity_Name (Subtype_Indication (N))
+      then
+         Set_Is_Atomic (Id, Is_Atomic (T));
+      end if;
+
       --  Remaining processing depends on characteristics of base type
 
       T := Etype (Id);