exp_ch5.adb (Controlled_Type): New routine.

2008-08-20  Hristian Kirtchev  <kirtchev@adacore.com>

	* exp_ch5.adb (Controlled_Type): New routine.
	(Expand_N_Extended_Return_Statement): When generating a move of the
	final list in extended return statements, check the type of the
	function and in the case of double expanded return statements, the type
	of the returned object.
	(Expand_Simple_Function_Return): Perform an interface conversion when
	the type of the returned object is an interface and the context is an
	extended return statement.

From-SVN: r139305

gcc/ada/exp_ch5.adb

@@ -2371,6 +2371,7 @@ package body Exp_Ch5 is
                                Parent (Return_Object_Entity);
       Parent_Function      : constant Entity_Id :=
                                Return_Applies_To (Return_Statement_Entity (N));
+      Parent_Function_Typ  : constant Entity_Id := Etype (Parent_Function);
       Is_Build_In_Place    : constant Boolean :=
                                Is_Build_In_Place_Function (Parent_Function);
 
@@ -2380,6 +2381,10 @@ package body Exp_Ch5 is
       Result          : Node_Id;
       Exp             : Node_Id;
 
+      function Controlled_Type (Typ : Entity_Id) return Boolean;
+      --  Determine whether type Typ is controlled or contains a controlled
+      --  component.
+
       function Move_Activation_Chain return Node_Id;
       --  Construct a call to System.Tasking.Stages.Move_Activation_Chain
       --  with parameters:
@@ -2394,6 +2399,17 @@ package body Exp_Ch5 is
       --    From         finalization list of the return statement
       --    To           finalization list passed in by the caller
 
+      ---------------------
+      -- Controlled_Type --
+      ---------------------
+
+      function Controlled_Type (Typ : Entity_Id) return Boolean is
+      begin
+         return
+           Is_Controlled (Typ)
+             or else Has_Controlled_Component (Typ);
+      end Controlled_Type;
+
       ---------------------------
       -- Move_Activation_Chain --
       ---------------------------
@@ -2518,23 +2534,24 @@ package body Exp_Ch5 is
          --  in the rather obscure case of a select-then-abort statement whose
          --  abortable part contains the return statement.
 
-         --  We test the type of the expression as well as the return type
-         --  of the function, because the latter may be a class-wide type
-         --  which is always treated as controlled, while the expression itself
-         --  has to have a definite type. The expression may be absent if a
-         --  constrained aggregate has been expanded into component assignments
-         --  so we have to check for this as well.
+         --  Check the type of the function to determine whether to move the
+         --  finalization list. A special case arises when processing a simple
+         --  return statement which has been rewritten as an extended return.
+         --  In that case check the type of the returned object or the original
+         --  expression.
 
          if Is_Build_In_Place
-           and then Controlled_Type (Etype (Parent_Function))
+           and then
+               (Controlled_Type (Parent_Function_Typ)
+             or else
+               (Is_Class_Wide_Type (Parent_Function_Typ)
+                  and then Controlled_Type (Root_Type (Parent_Function_Typ)))
+             or else
+               Controlled_Type (Etype (Return_Object_Entity))
+             or else
+               (Present (Exp) and then Controlled_Type (Etype (Exp))))
          then
-            if not Is_Class_Wide_Type (Etype (Parent_Function))
-              or else
-               (Present (Exp)
-                 and then Controlled_Type (Etype (Exp)))
-            then
-               Append_To (Statements, Move_Final_List);
-            end if;
+            Append_To (Statements, Move_Final_List);
          end if;
 
          --  Similarly to the above Move_Final_List, if the result type
@@ -3678,7 +3695,7 @@ package body Exp_Ch5 is
       --  inherently limited). We might prefer to do this translation in all
       --  cases (except perhaps for the case of Ada 95 inherently limited),
       --  in order to fully exercise the Expand_N_Extended_Return_Statement
-      --  code. This would also allow us to to the build-in-place optimization
+      --  code. This would also allow us to do the build-in-place optimization
       --  for efficiency even in cases where it is semantically not required.
 
       --  As before, we check the type of the return expression rather than the
@@ -3704,8 +3721,11 @@ package body Exp_Ch5 is
             --  expression is an aggregate that is built in place, this avoids
             --  the need for an expensive conversion of the return object to
             --  the specific type on assignments to the individual components.
+            --  Do not perform this high-level optimization if the result type
+            --  is an interface because the "this" pointer must be displaced.
 
             if Is_Class_Wide_Type (R_Type)
+              and then not Is_Interface (R_Type)
               and then not Is_Class_Wide_Type (Etype (Exp))
             then
                Subtype_Ind := New_Occurrence_Of (Etype (Exp), Loc);
@@ -3720,8 +3740,9 @@ package body Exp_Ch5 is
                               Object_Definition   => Subtype_Ind,
                               Expression          => Exp);
 
-               Ext : constant Node_Id := Make_Extended_Return_Statement (Loc,
-                       Return_Object_Declarations => New_List (Obj_Decl));
+               Ext : constant Node_Id :=
+                       Make_Extended_Return_Statement (Loc,
+                         Return_Object_Declarations => New_List (Obj_Decl));
 
             begin
                Rewrite (N, Ext);
@@ -4177,6 +4198,21 @@ package body Exp_Ch5 is
              Name => Make_Identifier (Loc, Name_uPostconditions),
              Parameter_Associations => New_List (Duplicate_Subexpr (Exp))));
       end if;
+
+      --  Ada 2005 (AI-251): If this return statement corresponds with an
+      --  simple return statement associated with an extended return statement
+      --  and the type of the returned object is an interface then generate an
+      --  implicit conversion to force displacement of the "this" pointer.
+
+      if Ada_Version >= Ada_05
+        and then Comes_From_Extended_Return_Statement (N)
+        and then Nkind (Expression (N)) = N_Identifier
+        and then Is_Interface (Utyp)
+        and then Utyp /= Underlying_Type (Exptyp)
+      then
+         Rewrite (Exp, Convert_To (Utyp, Relocate_Node (Exp)));
+         Analyze_And_Resolve (Exp);
+      end if;
    end Expand_Simple_Function_Return;
 
    ------------------------------