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   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                               L A Y O U T                                --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 2000-2018, 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.  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 COPYING3.  If not, go to --
  19 -- http://www.gnu.org/licenses for a complete copy of the license.          --
  20 --                                                                          --
  21 -- GNAT was originally developed  by the GNAT team at  New York University. --
  22 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  23 --                                                                          --
  24 ------------------------------------------------------------------------------
  25
  26 --  This package does front-end layout of types and objects. The result is
  27 --  to annotate the tree with information on size and alignment of types
  28 --  and objects. How much layout is performed depends on the setting of the
  29 --  target dependent parameter Backend_Layout.
  30
  31 with Types; use Types;
  32
  33 package Layout is
  34
  35    --  The following procedures are called from Freeze, so all entities
  36    --  for types and objects that get frozen (which should be all such
  37    --  entities which are seen by the back end) will get layed out by one
  38    --  of these two procedures.
  39
  40    procedure Layout_Type (E : Entity_Id);
  41    --  This procedure may set or adjust the fields Esize, RM_Size and
  42    --  Alignment in the non-generic type or subtype entity E. If the
  43    --  Backend_Layout switch is False, then it is guaranteed that all
  44    --  three fields will be properly set on return. Regardless of the
  45    --  Backend_Layout value, it is guaranteed that all discrete types
  46    --  will have both Esize and RM_Size fields set on return (since
  47    --  these are static values). Note that Layout_Type is not called
  48    --  for generic types, since these play no part in code generation,
  49    --  and hence representation aspects are irrelevant.
  50
  51    procedure Layout_Object (E : Entity_Id);
  52    --  E is either a variable (E_Variable), a constant (E_Constant),
  53    --  a loop parameter (E_Loop_Parameter), or a formal parameter of
  54    --  a non-generic subprogram (E_In_Parameter, E_In_Out_Parameter,
  55    --  or E_Out_Parameter). This procedure may set or adjust the
  56    --  Esize and Alignment fields of E. If Backend_Layout is False,
  57    --  then it is guaranteed that both fields will be properly set
  58    --  on return. If the Esize is still unknown in the latter case,
  59    --  it means that the object must be allocated dynamically, since
  60    --  its length is not known at compile time.
  61
  62    --  The following are utility routines, called from various places
  63
  64    procedure Adjust_Esize_Alignment (E : Entity_Id);
  65    --  E is the entity for a type or object. This procedure checks that the
  66    --  size and alignment are compatible, and if not either gives an error
  67    --  message if they cannot be adjusted or else adjusts them appropriately.
  68
  69    procedure Set_Discrete_RM_Size (Def_Id : Entity_Id);
  70    --  Set proper RM_Size for discrete size, this is normally the minimum
  71    --  number of bits to accommodate the range given, except in the case
  72    --  where the subtype statically matches the first subtype, in which
  73    --  case the size must be copied from the first subtype. For generic
  74    --  types, the RM_Size is simply set to zero. This routine also sets
  75    --  the Is_Constrained flag in Def_Id.
  76
  77    procedure Set_Elem_Alignment (E : Entity_Id; Align : Nat := 0);
  78    --  The front end always sets alignments for elementary types by calling
  79    --  this procedure. Note that we have to do this for discrete types (since
  80    --  the Alignment attribute is static), so we might as well do it for all
  81    --  elementary types, as the processing is the same. If Align is nonzero,
  82    --  it is an external alignment setting that we must respect.
  83
  84 end Layout;