gcc/ada/s-hibaen.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                  S Y S T E M . H I E _ B A C K _ E N D                   --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 2001-2003 Free Software Foundation, Inc.          --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  20 -- MA 02111-1307, USA.                                                      --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNAT was originally developed  by the GNAT team at  New York University. --
  30 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 --  This package provides an interface used in HI-E mode to determine
  35 --  whether or not the back end can handle certain constructs in a manner
  36 --  that is consistent with certification requirements.
  37
  38 --  The approach is to define entities which may or may not be present in
  39 --  a HI-E configured library. If the entity is present then the compiler
  40 --  operating in HI-E mode will allow the corresponding operation. If the
  41 --  entity is not present, the corresponding construct will be flagged as
  42 --  not permitted in High Integrity mode.
  43
  44 --  The default version of this unit delivered with the HI-E compiler is
  45 --  configured in a manner appropriate for the target, but it is possible
  46 --  to reconfigure the run-time to change the settings as required.
  47
  48 --  This unit is not used and never accessed by the compiler unless it is
  49 --  operating in HI-E mode, so the settings are irrelevant. However, we
  50 --  do include a standard version with all entities present in the standard
  51 --  run-time for use when pragma No_Run_Time is specified.
  52
  53 package System.HIE_Back_End is
  54
  55    type Dummy is null record;
  56    pragma Suppress_Initialization (Dummy);
  57    --  This is the type used for the entities below. No properties of this
  58    --  type are ever referenced, and in particular, the entities are defined
  59    --  as variables, but their values are never referenced
  60
  61    HIE_64_Bit_Divides : Dummy;
  62    --  This entity controls whether the front end allows 64-bit integer
  63    --  divide operations, including the case where division of 32-bit
  64    --  fixed-point operands requires 64-bit arithmetic. This can safely
  65    --  be set as High_Integrity on 64-bit machines which provide this
  66    --  operation as a native instruction, but on most 32-bit machines
  67    --  a run time call (e.g. to __divdi3 in gcclib) is required. If a
  68    --  certifiable version of this routine is available, then setting
  69    --  this entity to High_Integrity with a pragma will cause appropriate
  70    --  calls to be generated, allowing 64-bit integer division operations.
  71
  72    HIE_Long_Shifts : Dummy;
  73    --  This entity controls whether the front end allows generation of
  74    --  long shift instructions, i.e. shifts that operate on 64-bit values.
  75    --  Such shifts are required for the implementation of fixed-point
  76    --  types longer than 32 bits. This can safetly be set as High_Integrity
  77    --  on 64-bit machines that provide this operation at the hardware level,
  78    --  but on some 32-bit machines a run time call is required. If there
  79    --  is a certifiable version available of the relevant run-time routines,
  80    --  then setting this entity to High_Integrity with a pragma will cause
  81    --  appropriate calls to be generated, allowing the declaration and use
  82    --  of fixed-point types longer than 32 bits.
  83
  84    HIE_Aggregates : Dummy;
  85    --  In the general case, the use of aggregates may generate calls
  86    --  to run-time routines in the C library, including memset, memcpy,
  87    --  memmove, and bcopy. This entity can be set to High_Integrity with
  88    --  a pragma if certifiable versions of all these routines are available,
  89    --  in which case aggregates are permitted in HI-E mode. Otherwise the
  90    --  HI-E compiler will reject any use of aggregates.
  91
  92    HIE_Composite_Assignments : Dummy;
  93    --  The assignment of composite objects other than small records and
  94    --  arrays whose size is 64-bits or less and is set by an explicit
  95    --  size clause may generate calls to memcpy, memmove, and bcopy.
  96    --  If certifiable versions of all these routines are available, then
  97    --  this entity may be set to High_Integrity using a pragma, in which
  98    --  case such assignments are permitted. Otherwise the HI-E compiler
  99    --  will reject any such composite assignments.
 100
 101 end System.HIE_Back_End;