gcc/ada/sem_maps.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                             S E M _ M A P S                              --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1996-2007, 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 contains the operations on the renaming maps used for
  27 --  generic analysis and instantiation. Renaming maps are created when
  28 --  a generic unit is analyzed, in order to capture all references to
  29 --  global variables within the unit. The renaming map of a generic unit
  30 --  copied prior to each instantiation, and then updated by mapping the
  31 --  formals into the actuals and the local entities into entities local to
  32 --  the instance. When the generic tree is copied to produce the instance,
  33 --  all references are updated by means of the renaming map.
  34
  35 --  Map composition of renaming maps takes place for nested instantiations,
  36 --  for generic child units, and for formal packages.
  37
  38 --  For additional details, see the documentation in sem_ch12
  39
  40 with Table;
  41 with Types; use Types;
  42
  43 package Sem_Maps is
  44
  45    type Map is new Int;
  46
  47    type Assoc is private;
  48
  49    type Scope_Kind is (S_Global, S_Formal, S_Local);
  50
  51    function New_Map (Num_Assoc : Int) return Map;
  52    --  Build empty map with the given number of associations, and a
  53    --  headers table of the appropriate size.
  54
  55    function Compose (Orig_Map : Map; New_Map : Map) return Map;
  56    --  Update the associations in Orig_Map, so that if Orig_Map (e1) = e2
  57    --  and New_Map (e2) = e3, then the image of e1 under the result is e3.
  58
  59    function Copy (M : Map) return Map;
  60    --  Full copy of contents and headers
  61
  62    function Lookup (M : Map; E : Entity_Id) return Entity_Id;
  63    --  Retrieve image of E under M, Empty if undefined
  64
  65    procedure Add_Association
  66      (M    : Map;
  67       O_Id : Entity_Id;
  68       N_Id : Entity_Id;
  69       Kind : Scope_Kind := S_Local);
  70    --  Update M in place. On entry M (O_Id) must not be defined
  71
  72    procedure Update_Association
  73      (M    : Map;
  74       O_Id : Entity_Id;
  75       N_Id : Entity_Id;
  76       Kind : Scope_Kind := S_Local);
  77    --  Update the entry in M for O_Id
  78
  79    function Build_Instance_Map (M : Map) return Map;
  80    --  Copy renaming map of generic, and create new entities for all the
  81    --  local entities within.
  82
  83 private
  84
  85    --  New maps are created when a generic is analyzed, and for each of
  86    --  its instantiations. Maps are also updated for nested generics, for
  87    --  child units, and for formal packages. As a result we need to allocate
  88    --  maps dynamically.
  89
  90    --  When analyzing a generic, we do not know how many references are
  91    --  in it. We build an initial map after generic analysis, using a static
  92    --  structure that relies on the compiler's extensible table mechanism.
  93    --  After constructing this initial map, all subsequent uses and updates
  94    --  of this map do not modify its domain, so that dynamically allocated
  95    --  maps have a fixed size and never need to be reallocated. Furthermore,
  96    --  the headers of the hash table of a dynamically allocated map can be
  97    --  chosen according to the total number of entries in the map, to
  98    --  accommodate efficiently generic units of different sizes (Unchecked_
  99    --  Conversion vs. Generic_Elementary_Functions, for example). So in
 100    --  fact both components of a map have fixed size, and can be allocated
 101    --  using the standard table mechanism. A Maps_Table holds records that
 102    --  contain indices into the global Headers table and the Associations
 103    --  table, and a Map is an index into the Maps_Table.
 104    --
 105    --              Maps_Table          Headers_Table     Associations_Table
 106    --
 107    --                                    |_____|          |___________ |
 108    --               |_____|              |     |          |            |
 109    --        ------>|Map  |------------------------------>|Associations|
 110    --               |Info |------------->|     |=========>| for one    |
 111    --               |_____|              |     |====|     |   unit     |
 112    --               |     |              |     |    |====>|            |
 113    --                                    |_____|          |____________|
 114    --                                    |     |          |            |
 115    type Header_Index is new Int;
 116    type Assoc_Index  is new Int;
 117    No_Assoc : constant Assoc_Index := -1;
 118
 119    type Map_Info is record
 120       Header_Offset : Header_Index;
 121       Header_Num    : Header_Index;
 122       Assoc_Offset  : Assoc_Index;
 123       Assoc_Num     : Assoc_Index;
 124       Assoc_Next    : Assoc_Index;
 125    end record;
 126
 127    type Assoc is record
 128       Old_Id : Entity_Id   := Empty;
 129       New_Id : Entity_Id   := Empty;
 130       Kind   : Scope_Kind  := S_Local;
 131       Next   : Assoc_Index := No_Assoc;
 132    end record;
 133
 134    --  All maps are accessed through the following table. The map attribute
 135    --  of a generic unit or an instance is an index into this table.
 136
 137    package Maps_Table is new Table.Table (
 138       Table_Component_Type => Map_Info,
 139       Table_Index_Type     => Map,
 140       Table_Low_Bound      => 0,
 141       Table_Initial        => 100,
 142       Table_Increment      => 100,
 143       Table_Name           => "Maps_Table");
 144
 145    --  All headers for hash tables are allocated in one global table. Each
 146    --  map stores the offset into this table at which its own headers start.
 147
 148    package Headers_Table is new Table.Table (
 149       Table_Component_Type => Assoc_Index,
 150       Table_Index_Type     => Header_Index,
 151       Table_Low_Bound      => 0,
 152       Table_Initial        => 1000,
 153       Table_Increment      => 100,
 154       Table_Name           => "Headers_Table");
 155
 156    --  All associations are allocated in one global table. Each map stores
 157    --  the offset into this table at which its own associations start.
 158
 159    package Associations_Table is new Table.Table (
 160       Table_Component_Type => Assoc,
 161       Table_Index_Type     => Assoc_Index,
 162       Table_Low_Bound      => 1,
 163       Table_Initial        => 1000,
 164       Table_Increment      => 100,
 165       Table_Name           => "Associations_Table");
 166
 167 end Sem_Maps;