[Ada] Fix internal error on semi-circular record types

The front-end properly computes a linear elaboration order for them, but
there was a loophole in the handling of the delayed case.

gcc/ada/

	* gcc-interface/decl.cc (gnat_to_gnu_entity) <E_Access_Subtype>: And
	skip the elaboration of the designated subtype when that of its base
	type has been delayed.

diff --git a/gcc/ada/gcc-interface/decl.cc b/gcc/ada/gcc-interface/decl.cc
index 075a7ebd372998e6357a377b955aed8576579008..aa8736c7a8615bf6e01f0a5c4775ab137d8b06e8 100644 (file)
--- a/gcc/ada/gcc-interface/decl.cc
+++ b/gcc/ada/gcc-interface/decl.cc
@@ -3846,17 +3846,18 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
       maybe_present = true;
 
       /* The designated subtype must be elaborated as well, if it does
-        not have its own freeze node.  But designated subtypes created
-        for constrained components of records with discriminants are
-        not frozen by the front-end and not elaborated here, because
-        their use may appear before the base type is frozen and it is
-        not clear that they are needed in gigi.  With the current model,
-        there is no correct place where they could be elaborated.  */
+        not have its own freeze node.  */
       if (Is_Itype (Directly_Designated_Type (gnat_entity))
          && !present_gnu_tree (Directly_Designated_Type (gnat_entity))
          && Is_Frozen (Directly_Designated_Type (gnat_entity))
          && No (Freeze_Node (Directly_Designated_Type (gnat_entity))))
        {
+         tree gnu_base_type = TREE_TYPE (gnu_decl);
+         tree gnu_desig_base_type
+           = TYPE_IS_FAT_POINTER_P (gnu_base_type)
+             ? TREE_TYPE (TREE_TYPE (TYPE_FIELDS (gnu_base_type)))
+             : TREE_TYPE (gnu_base_type);
+
          /* If we are to defer elaborating incomplete types, make a dummy
             type node and elaborate it later.  */
          if (defer_incomplete_level != 0)
@@ -3869,8 +3870,10 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
              p->next = defer_incomplete_list;
              defer_incomplete_list = p;
            }
-         else if (!Is_Incomplete_Or_Private_Type
-                     (Base_Type (Directly_Designated_Type (gnat_entity))))
+
+         /* Otherwise elaborate the designated subtype only if its base type
+            has already been elaborated.  */
+         else if (!TYPE_IS_DUMMY_P (gnu_desig_base_type))
            gnat_to_gnu_entity (Directly_Designated_Type (gnat_entity),
                                NULL_TREE, false);
        }