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--                                                                          --

--                         GNAT RUN-TIME COMPONENTS                         --

--                                                                          --

--                  S Y S T E M . H I E _ B A C K _ E N D                   --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--          Copyright (C) 2001-2009, Free Software Foundation, Inc.         --

--                                                                          --

-- GNAT is free software;  you can  redistribute it  and/or modify it under --

-- terms of the  GNU General Public License as published  by the Free Soft- --

-- ware  Foundation;  either version 3,  or (at your option) any later ver- --

-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --

-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --

-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --

--                                                                          --

-- As a special exception under Section 7 of GPL version 3, you are granted --

-- additional permissions described in the GCC Runtime Library Exception,   --

-- version 3.1, as published by the Free Software Foundation.               --

--                                                                          --

-- You should have received a copy of the GNU General Public License and    --

-- a copy of the GCC Runtime Library Exception along with this program;     --

-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --

-- <http://www.gnu.org/licenses/>.                                          --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

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--  This package provides an interface used in HI-E mode to determine

--  whether or not the back end can handle certain constructs in a manner

--  that is consistent with certification requirements.

--  The approach is to define entities which may or may not be present in

--  a HI-E configured library. If the entity is present then the compiler

--  operating in HI-E mode will allow the corresponding operation. If the

--  entity is not present, the corresponding construct will be flagged as

--  not permitted in High Integrity mode.

--  The default version of this unit delivered with the HI-E compiler is

--  configured in a manner appropriate for the target, but it is possible

--  to reconfigure the run-time to change the settings as required.

--  This unit is not used and never accessed by the compiler unless it is

--  operating in HI-E mode, so the settings are irrelevant. However, we

--  do include a standard version with all entities present in the standard

--  run-time for use when pragma No_Run_Time is specified.

package System.HIE_Back_End is

   type Dummy is null record;

   pragma Suppress_Initialization (Dummy);

   --  This is the type used for the entities below. No properties of this

   --  type are ever referenced, and in particular, the entities are defined

   --  as variables, but their values are never referenced

   HIE_64_Bit_Divides : Dummy;

   --  This entity controls whether the front end allows 64-bit integer

   --  divide operations, including the case where division of 32-bit

   --  fixed-point operands requires 64-bit arithmetic. This can safely

   --  be set as High_Integrity on 64-bit machines which provide this

   --  operation as a native instruction, but on most 32-bit machines

   --  a run time call (e.g. to __divdi3 in gcclib) is required. If a

   --  certifiable version of this routine is available, then setting

   --  this entity to High_Integrity with a pragma will cause appropriate

   --  calls to be generated, allowing 64-bit integer division operations.

   HIE_Long_Shifts : Dummy;

   --  This entity controls whether the front end allows generation of

   --  long shift instructions, i.e. shifts that operate on 64-bit values.

   --  Such shifts are required for the implementation of fixed-point

   --  types longer than 32 bits. This can safely be set as High_Integrity

   --  on 64-bit machines that provide this operation at the hardware level,

   --  but on some 32-bit machines a run time call is required. If there

   --  is a certifiable version available of the relevant run-time routines,

   --  then setting this entity to High_Integrity with a pragma will cause

   --  appropriate calls to be generated, allowing the declaration and use

   --  of fixed-point types longer than 32 bits.

   HIE_Aggregates : Dummy;

   --  In the general case, the use of aggregates may generate calls

   --  to run-time routines in the C library, including memset, memcpy,

   --  memmove, and bcopy. This entity can be set to High_Integrity with

   --  a pragma if certifiable versions of all these routines are available,

   --  in which case aggregates are permitted in HI-E mode. Otherwise the

   --  HI-E compiler will reject any use of aggregates.

   HIE_Composite_Assignments : Dummy;

   --  The assignment of composite objects other than small records and

   --  arrays whose size is 64-bits or less and is set by an explicit

   --  size clause may generate calls to memcpy, memmove, and bcopy.

   --  If certifiable versions of all these routines are available, then

   --  this entity may be set to High_Integrity using a pragma, in which

   --  case such assignments are permitted. Otherwise the HI-E compiler

   --  will reject any such composite assignments.

end System.HIE_Back_End;