decl.c (FORCE_PREFERRED_STACK_BOUNDARY_IN_MAIN): Define to 0 if undefined.

2008-06-13  Olivier Hainque  <hainque@adacore.com>

	ada/
	* decl.c (FORCE_PREFERRED_STACK_BOUNDARY_IN_MAIN): Define to 0
	if undefined.
	(gnat_to_gnu_entity) <case E_Function/Procedure>: Request stack
	realignment with force_align_arg_pointer attribute on foreign
	convention subprograms if FORCE_PREFERRED_STACK_BOUNDARY_IN_MAIN.

	testsuite/
	* gnat.dg/task_stack_align.adb: New test.

From-SVN: r136768

gcc/ada/ChangeLog

 2008-06-13  Olivier Hainque  <hainque@adacore.com>
 
+	* decl.c (FORCE_PREFERRED_STACK_BOUNDARY_IN_MAIN): Define to 0
+	if undefined.
+	(gnat_to_gnu_entity) <case E_Function/Procedure>: Request stack
+	realignment with force_align_arg_pointer attribute on foreign
+	convention subprograms if FORCE_PREFERRED_STACK_BOUNDARY_IN_MAIN.
+	
+2008-06-13  Olivier Hainque  <hainque@adacore.com>
+
 	* utils.c (rest_of_record_type_compilation): When computing
 	encodings for the components of a variable size type, early
 	strip conversions on the current position expression to make

gcc/ada/decl.c

@@ -67,6 +67,29 @@
 #define Has_Stdcall_Convention(E) (0)
 #endif
 
+/* Stack realignment for functions with foreign conventions is provided on a
+   per back-end basis now, as it is handled by the prologue expanders and not
+   as part of the function's body any more.  It might be requested by way of a
+   dedicated function type attribute on the targets that support it.
+
+   We need a way to avoid setting the attribute on the targets that don't
+   support it and use FORCE_PREFERRED_STACK_BOUNDARY_IN_MAIN for this purpose.
+
+   It is defined on targets where the circuitry is available, and indicates
+   whether the realignment is needed for 'main'. We use this to decide for
+   foreign subprograms as well.
+
+   It is not defined on targets where the circuitry is not implemented, and
+   we just never set the attribute in these cases.
+
+   Whether it is defined on all targets that would need it in theory is
+   not entirely clear.  We currently trust the base GCC settings for this
+   purpose.  */
+
+#ifndef FORCE_PREFERRED_STACK_BOUNDARY_IN_MAIN
+#define FORCE_PREFERRED_STACK_BOUNDARY_IN_MAIN 0
+#endif
+
 struct incomplete
 {
   struct incomplete *next;
@@ -3951,6 +3974,19 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, int definition)
 	     get_identifier ("stdcall"), NULL_TREE,
 	     gnat_entity);
 
+	/* If we are on a target where stack realignment is needed for 'main'
+	   to honor GCC's implicit expectations (stack alignment greater than
+	   what the base ABI guarantees), ensure we do the same for foreign
+	   convention subprograms as they might be used as callbacks from code
+	   breaking such expectations.  Note that this applies to task entry
+	   points in particular.  */
+	if (FORCE_PREFERRED_STACK_BOUNDARY_IN_MAIN
+	    && Has_Foreign_Convention (gnat_entity))
+	  prepend_one_attribute_to
+	    (&attr_list, ATTR_MACHINE_ATTRIBUTE,
+	     get_identifier ("force_align_arg_pointer"), NULL_TREE,
+	     gnat_entity);
+
 	/* The lists have been built in reverse.  */
 	gnu_param_list = nreverse (gnu_param_list);
 	if (has_stub)

gcc/testsuite/ChangeLog

+2008-06-13  Olivier Hainque  <hainque@adacore.com>
+
+	* gnat.dg/task_stack_align.adb: New test.
+
 2008-06-13  Jerry DeLisle  <jvdelisle@gcc.gnu.org>
 
 	PR fortran/35863

gcc/testsuite/gnat.dg/task_stack_align.adb

+-- { dg-do run }
+
+with Ada.Text_IO; use Ada.Text_IO;
+with System.Storage_Elements; use System.Storage_Elements;
+
+procedure Task_Stack_Align is
+
+   type Align_Me is record
+      Value : Integer;
+   end record;
+   for Align_Me'Alignment use Standard'Maximum_Alignment;
+
+   procedure Check_Local_Alignment_From (Context : String) is
+      Object : Align_Me;
+   begin
+      if To_Integer (Object'Address) mod Object'Alignment /= 0 then
+         Put_Line ("alignment check failed in " & Context);
+      end if;
+   end;
+
+   task type T;
+
+   task body T is
+   begin
+      Check_Local_Alignment_From ("task T");
+   end;
+
+   Tasks : array (1 .. 50) of T;
+begin
+   Check_Local_Alignment_From ("environment");
+end;