[Ada] Fix LTO warning with tagged types

[Eric Botcazou <ebotcazou at adacore dot com>]

Static dispatch tables use a trick to break up circularity problems: first 
they are declared as imported constants then defined as exported constants.
This leads to problems with type merging in LTO mode because a specific 
subtype is used in each case.

Tested on i586-suse-linux, applied on the mainline.


2010-05-08  Eric Botcazou  <ebotcazou@adacore.com>

	* exp_disp.adb (Make_Tags): Mark the imported view of dispatch tables.
	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Variable>: Make imported
	constants really constant.
	<E_Record_Subtype>: Strip the suffix for dispatch table entities.


2010-05-08  Eric Botcazou  <ebotcazou@adacore.com>

	* gnat.dg/lto5.adb: New test.
	* gnat.dg/lto5_pkg.ad[sb]: New helper.


-- 
Eric Botcazou

Index: exp_disp.adb
===================================================================
--- exp_disp.adb	(revision 159144)
+++ exp_disp.adb	(working copy)
@@ -6241,7 +6241,7 @@ package body Exp_Disp is
 
       Tname            : constant Name_Id := Chars (Typ);
       AI_Tag_Comp      : Elmt_Id;
-      DT               : Node_Id;
+      DT               : Node_Id := Empty;
       DT_Ptr           : Node_Id;
       Predef_Prims_Ptr : Node_Id;
       Iface_DT         : Node_Id;
@@ -6562,6 +6562,14 @@ package body Exp_Disp is
          end;
       end if;
 
+      --  Mark entities of dispatch table. Required by the back end to
+      --  handle them properly.
+
+      if Present (DT) then
+         Set_Is_Dispatch_Table_Entity (DT);
+         Set_Is_Dispatch_Table_Entity (Etype (DT));
+      end if;
+
       Set_Ekind        (DT_Ptr, E_Constant);
       Set_Is_Tag       (DT_Ptr);
       Set_Related_Type (DT_Ptr, Typ);
Index: gcc-interface/decl.c
===================================================================
--- gcc-interface/decl.c	(revision 159183)
+++ gcc-interface/decl.c	(working copy)
@@ -560,7 +560,8 @@ gnat_to_gnu_entity (Entity_Id gnat_entit
 	     && (((Nkind (Declaration_Node (gnat_entity))
 		   == N_Object_Declaration)
 		  && Present (Expression (Declaration_Node (gnat_entity))))
-		 || Present (Renamed_Object (gnat_entity))));
+		 || Present (Renamed_Object (gnat_entity))
+		 || Is_Imported (gnat_entity)));
 	bool inner_const_flag = const_flag;
 	bool static_p = Is_Statically_Allocated (gnat_entity);
 	bool mutable_p = false;
@@ -2975,6 +2976,20 @@ gnat_to_gnu_entity (Entity_Id gnat_entit
 	      break;
 	    }
 
+	  /* If this is a record subtype associated with a dispatch table,
+	     strip the suffix.  This is necessary to make sure 2 different
+	     subtypes associated with the imported and exported views of a
+	     dispatch table are properly merged in LTO mode.  */
+	  if (Is_Dispatch_Table_Entity (gnat_entity))
+	    {
+	      char *p;
+	      Get_Encoded_Name (gnat_entity);
+	      p = strrchr (Name_Buffer, '_');
+	      gcc_assert (p);
+	      strcpy (p+1, "dtS");
+	      gnu_entity_name = get_identifier (Name_Buffer);
+	    }
+
 	  /* When the subtype has discriminants and these discriminants affect
 	     the initial shape it has inherited, factor them in.  But for an
 	     Unchecked_Union (it must be an Itype), just return the type.

-- { dg-do run }
-- { dg-options "-flto" }

with Lto5_Pkg;

procedure Lto5 is
begin
   null;
end;

pragma Eliminate (p, d);

package Lto5_Pkg is
   type t is tagged null record;
   procedure d (a : t);
end;

package body Lto5_Pkg is
   procedure d (a : t) is
   begin
      null;
   end;
end;