File : layout.ads
1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT COMPILER COMPONENTS --
4 -- --
5 -- L A Y O U T --
6 -- --
7 -- S p e c --
8 -- --
9 -- Copyright (C) 2000-2007, 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);
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, since the processing is the same.
82
83 end Layout;