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) 2001-2009, 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 3,  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.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 --  This package provides an interface used in HI-E mode to determine
  33 --  whether or not the back end can handle certain constructs in a manner
  34 --  that is consistent with certification requirements.
  35
  36 --  The approach is to define entities which may or may not be present in
  37 --  a HI-E configured library. If the entity is present then the compiler
  38 --  operating in HI-E mode will allow the corresponding operation. If the
  39 --  entity is not present, the corresponding construct will be flagged as
  40 --  not permitted in High Integrity mode.
  41
  42 --  The default version of this unit delivered with the HI-E compiler is
  43 --  configured in a manner appropriate for the target, but it is possible
  44 --  to reconfigure the run-time to change the settings as required.
  45
  46 --  This unit is not used and never accessed by the compiler unless it is
  47 --  operating in HI-E mode, so the settings are irrelevant. However, we
  48 --  do include a standard version with all entities present in the standard
  49 --  run-time for use when pragma No_Run_Time is specified.
  50
  51 package System.HIE_Back_End is
  52
  53    type Dummy is null record;
  54    pragma Suppress_Initialization (Dummy);
  55    --  This is the type used for the entities below. No properties of this
  56    --  type are ever referenced, and in particular, the entities are defined
  57    --  as variables, but their values are never referenced
  58
  59    HIE_64_Bit_Divides : Dummy;
  60    --  This entity controls whether the front end allows 64-bit integer
  61    --  divide operations, including the case where division of 32-bit
  62    --  fixed-point operands requires 64-bit arithmetic. This can safely
  63    --  be set as High_Integrity on 64-bit machines which provide this
  64    --  operation as a native instruction, but on most 32-bit machines
  65    --  a run time call (e.g. to __divdi3 in gcclib) is required. If a
  66    --  certifiable version of this routine is available, then setting
  67    --  this entity to High_Integrity with a pragma will cause appropriate
  68    --  calls to be generated, allowing 64-bit integer division operations.
  69
  70    HIE_Long_Shifts : Dummy;
  71    --  This entity controls whether the front end allows generation of
  72    --  long shift instructions, i.e. shifts that operate on 64-bit values.
  73    --  Such shifts are required for the implementation of fixed-point
  74    --  types longer than 32 bits. This can safely be set as High_Integrity
  75    --  on 64-bit machines that provide this operation at the hardware level,
  76    --  but on some 32-bit machines a run time call is required. If there
  77    --  is a certifiable version available of the relevant run-time routines,
  78    --  then setting this entity to High_Integrity with a pragma will cause
  79    --  appropriate calls to be generated, allowing the declaration and use
  80    --  of fixed-point types longer than 32 bits.
  81
  82    HIE_Aggregates : Dummy;
  83    --  In the general case, the use of aggregates may generate calls
  84    --  to run-time routines in the C library, including memset, memcpy,
  85    --  memmove, and bcopy. This entity can be set to High_Integrity with
  86    --  a pragma if certifiable versions of all these routines are available,
  87    --  in which case aggregates are permitted in HI-E mode. Otherwise the
  88    --  HI-E compiler will reject any use of aggregates.
  89
  90    HIE_Composite_Assignments : Dummy;
  91    --  The assignment of composite objects other than small records and
  92    --  arrays whose size is 64-bits or less and is set by an explicit
  93    --  size clause may generate calls to memcpy, memmove, and bcopy.
  94    --  If certifiable versions of all these routines are available, then
  95    --  this entity may be set to High_Integrity using a pragma, in which
  96    --  case such assignments are permitted. Otherwise the HI-E compiler
  97    --  will reject any such composite assignments.
  98
  99 end System.HIE_Back_End;