[Ada] Fix internal error on double renaming of private constant

The first renaming uses the type of the full view of the constant but not
the second, which introduces problematic view conversions downstream.

gcc/ada/

	* gcc-interface/trans.cc (Full_View_Of_Private_Constant): New
	function returning the Full_View of a private constant, after
	looking through a chain of renamings, if any.
	(Identifier_to_gnu): Call it on the entity.  Small cleanup.

1 files changed, 43 insertions, 25 deletions

diff --git a/gcc/ada/gcc-interface/trans.cc b/gcc/ada/gcc-interface/trans.cc
index eae15dc..b6c42f5 100644
--- a/gcc/ada/gcc-interface/trans.cc
+++ b/gcc/ada/gcc-interface/trans.cc
@@ -1088,6 +1088,28 @@ Gigi_Types_Compatible (Entity_Id type, Entity_Id def_type)
   return false;
 }
 
+/* Return the full view of a private constant E, or of a renaming thereof, if
+   its type has discriminants, and Empty otherwise.  */
+
+static Entity_Id
+Full_View_Of_Private_Constant (Entity_Id E)
+{
+  while (Present (Renamed_Object (E)) && Is_Entity_Name (Renamed_Object (E)))
+    E = Entity (Renamed_Object (E));
+
+  if (Ekind (E) != E_Constant || No (Full_View (E)))
+    return Empty;
+
+  const Entity_Id T = Etype (E);
+
+  if (Is_Private_Type (T)
+      && (Has_Unknown_Discriminants (T)
+	  || (Present (Full_View (T)) && Has_Discriminants (Full_View (T)))))
+    return Full_View (E);
+
+  return Empty;
+}
+
 /* Subroutine of gnat_to_gnu to translate GNAT_NODE, an N_Identifier, to a GCC
    tree, which is returned.  GNU_RESULT_TYPE_P is a pointer to where we should
    place the result type.  */
@@ -1095,21 +1117,19 @@ Gigi_Types_Compatible (Entity_Id type, Entity_Id def_type)
 static tree
 Identifier_to_gnu (Node_Id gnat_node, tree *gnu_result_type_p)
 {
-  /* The entity of GNAT_NODE and its type.  */
-  Node_Id gnat_entity = (Nkind (gnat_node) == N_Defining_Identifier
-			 || Nkind (gnat_node) == N_Defining_Operator_Symbol)
-			? gnat_node : Entity (gnat_node);
-  Node_Id gnat_entity_type = Etype (gnat_entity);
+  Entity_Id gnat_entity = (Nkind (gnat_node) == N_Defining_Identifier
+			   || Nkind (gnat_node) == N_Defining_Operator_Symbol)
+			  ? gnat_node : Entity (gnat_node);
+  Entity_Id gnat_result_type;
+  tree gnu_result, gnu_result_type;
   /* If GNAT_NODE is a constant, whether we should use the initialization
      value instead of the constant entity, typically for scalars with an
      address clause when the parent doesn't require an lvalue.  */
-  bool use_constant_initializer = false;
+  bool use_constant_initializer;
   /* Whether we should require an lvalue for GNAT_NODE.  Needed in
      specific circumstances only, so evaluated lazily.  < 0 means
      unknown, > 0 means known true, 0 means known false.  */
-  int require_lvalue = -1;
-  Entity_Id gnat_result_type;
-  tree gnu_result, gnu_result_type;
+  int require_lvalue;
 
   /* If the Etype of this node is not the same as that of the Entity, then
      something went wrong, probably in generic instantiation.  However, this
@@ -1118,25 +1138,17 @@ Identifier_to_gnu (Node_Id gnat_node, tree *gnu_result_type_p)
      may have been changed to a subtype by Exp_Ch3.Adjust_Discriminants.  */
   gcc_assert (!Is_Object (gnat_entity)
 	      || Ekind (gnat_entity) == E_Discriminant
-	      || Etype (gnat_node) == gnat_entity_type
-	      || Gigi_Types_Compatible (Etype (gnat_node), gnat_entity_type));
+	      || Etype (gnat_node) == Etype (gnat_entity)
+	      || Gigi_Types_Compatible (Etype (gnat_node),
+					Etype (gnat_entity)));
 
-  /* If this is a reference to a deferred constant whose partial view is an
+  /* If this is a reference to a deferred constant whose partial view is of
      unconstrained private type, the proper type is on the full view of the
-     constant, not on the full view of the type, which may be unconstrained.
-
-     This may be a reference to a type, for example in the prefix of the
-     attribute Position, generated for dispatching code (see Make_DT in
-     exp_disp,adb). In that case we need the type itself, not is parent,
-     in particular if it is a derived type  */
-  if (Ekind (gnat_entity) == E_Constant
-      && Is_Private_Type (gnat_entity_type)
-      && (Has_Unknown_Discriminants (gnat_entity_type)
-	  || (Present (Full_View (gnat_entity_type))
- 	      && Has_Discriminants (Full_View (gnat_entity_type))))
-      && Present (Full_View (gnat_entity)))
+     constant, not on the full view of the type which may be unconstrained.  */
+  const Entity_Id gnat_full_view = Full_View_Of_Private_Constant (gnat_entity);
+  if (Present (gnat_full_view))
     {
-      gnat_entity = Full_View (gnat_entity);
+      gnat_entity = gnat_full_view;
       gnat_result_type = Etype (gnat_entity);
     }
   else
@@ -1184,7 +1196,13 @@ Identifier_to_gnu (Node_Id gnat_node, tree *gnu_result_type_p)
 	= lvalue_required_p (gnat_node, gnu_result_type, true, false);
       use_constant_initializer = !require_lvalue;
     }
+  else
+    {
+      require_lvalue = -1;
+      use_constant_initializer = false;
+    }
 
+  /* Fetch the initialization value of a constant if requested.  */
   if (use_constant_initializer)
     {
       /* If this is a deferred constant, the initializer is attached to