gcc/ada/exp_ch2.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                              E X P _ C H 2                               --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --                            $Revision: 1.1 $
  10 --                                                                          --
  11 --          Copyright (C) 1992-2001 Free Software Foundation, Inc.          --
  12 --                                                                          --
  13 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  14 -- terms of the  GNU General Public License as published  by the Free Soft- --
  15 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  16 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  17 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  18 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  19 -- for  more details.  You should have  received  a copy of the GNU General --
  20 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  21 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  22 -- MA 02111-1307, USA.                                                      --
  23 --                                                                          --
  24 -- GNAT was originally developed  by the GNAT team at  New York University. --
  25 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
  26 --                                                                          --
  27 ------------------------------------------------------------------------------
  28
  29 with Atree;    use Atree;
  30 with Einfo;    use Einfo;
  31 with Elists;   use Elists;
  32 with Exp_Smem; use Exp_Smem;
  33 with Exp_Util; use Exp_Util;
  34 with Exp_VFpt; use Exp_VFpt;
  35 with Nmake;    use Nmake;
  36 with Sem;      use Sem;
  37 with Sem_Res;  use Sem_Res;
  38 with Sem_Util; use Sem_Util;
  39 with Sinfo;    use Sinfo;
  40 with Tbuild;   use Tbuild;
  41 with Snames;   use Snames;
  42
  43 package body Exp_Ch2 is
  44
  45    -----------------------
  46    -- Local Subprograms --
  47    -----------------------
  48
  49    procedure Expand_Discriminant (N : Node_Id);
  50    --  An occurrence of a discriminant within a discriminated type is replaced
  51    --  with the corresponding discriminal, that is to say the formal parameter
  52    --  of the initialization procedure for the type that is associated with
  53    --  that particular discriminant. This replacement is not performed for
  54    --  discriminants of records that appear in constraints of component of the
  55    --  record, because Gigi uses the discriminant name to retrieve its value.
  56    --  In the other hand, it has to be performed for default expressions of
  57    --  components because they are used in the record init procedure. See
  58    --  Einfo for more details, and Exp_Ch3, Exp_Ch9 for examples of use.
  59    --  For discriminants of tasks and protected types, the transformation is
  60    --  more complex when it occurs within a default expression for an entry
  61    --  or protected operation. The corresponding default_expression_function
  62    --  has an additional parameter which is the target of an entry call, and
  63    --  the discriminant of the task must be replaced with a reference to the
  64    --  discriminant of that formal parameter.
  65
  66    procedure Expand_Entity_Reference (N : Node_Id);
  67    --  Common processing for expansion of identifiers and expanded names
  68
  69    procedure Expand_Entry_Index_Parameter (N : Node_Id);
  70    --  A reference to the identifier in the entry index specification
  71    --  of a protected entry body is modified to a reference to a constant
  72    --  definintion equal to the index of the entry family member being
  73    --  called. This constant is calculated as part of the elaboration
  74    --  of the expanded code for the body, and is calculated from the
  75    --  object-wide entry index returned by Next_Entry_Call.
  76
  77    procedure Expand_Entry_Parameter (N : Node_Id);
  78    --  A reference to an entry parameter is modified to be a reference to
  79    --  the corresponding component of the entry parameter record that is
  80    --  passed by the runtime to the accept body procedure
  81
  82    procedure Expand_Formal (N : Node_Id);
  83    --  A reference to a formal parameter of a protected subprogram is
  84    --  expanded to the corresponding formal of the unprotected procedure
  85    --  used to represent the protected subprogram within the protected object.
  86
  87    procedure Expand_Protected_Private (N : Node_Id);
  88    --  A reference to a private object of a protected type is expanded
  89    --  to a component selected from the record used to implement
  90    --  the protected object. Such a record is passed to all operations
  91    --  on a protected object in a parameter named _object. Such an object
  92    --  is a constant within a function, and a variable otherwise.
  93
  94    procedure Expand_Renaming (N : Node_Id);
  95    --  For renamings, just replace the identifier by the corresponding
  96    --  name expression. Note that this has been evaluated (see routine
  97    --  Exp_Ch8.Expand_N_Object_Renaming.Evaluate_Name) so this gives
  98    --  the correct renaming semantics.
  99
 100    -------------------------
 101    -- Expand_Discriminant --
 102    -------------------------
 103
 104    procedure Expand_Discriminant (N : Node_Id) is
 105       Scop     : constant Entity_Id := Scope (Entity (N));
 106       P        : Node_Id := N;
 107       Parent_P : Node_Id := Parent (P);
 108       In_Entry : Boolean := False;
 109
 110    begin
 111       --  The Incomplete_Or_Private_Kind happens while resolving the
 112       --  discriminant constraint involved in a derived full type,
 113       --  such as:
 114
 115       --    type D is private;
 116       --    type D(C : ...) is new T(C);
 117
 118       if Ekind (Scop) = E_Record_Type
 119         or Ekind (Scop) in Incomplete_Or_Private_Kind
 120       then
 121
 122          --  Find the origin by walking up the tree till the component
 123          --  declaration
 124
 125          while Present (Parent_P)
 126            and then Nkind (Parent_P) /= N_Component_Declaration
 127          loop
 128             P := Parent_P;
 129             Parent_P := Parent (P);
 130          end loop;
 131
 132          --  If the discriminant reference was part of the default expression
 133          --  it has to be "discriminalized"
 134
 135          if Present (Parent_P) and then P = Expression (Parent_P) then
 136             Set_Entity (N, Discriminal (Entity (N)));
 137          end if;
 138
 139       elsif Is_Concurrent_Type (Scop) then
 140          while Present (Parent_P)
 141            and then Nkind (Parent_P) /= N_Subprogram_Body
 142          loop
 143             P := Parent_P;
 144
 145             if Nkind (P) = N_Entry_Declaration then
 146                In_Entry := True;
 147             end if;
 148
 149             Parent_P := Parent (Parent_P);
 150          end loop;
 151
 152          --  If the discriminant occurs within the default expression for
 153          --  a formal of an entry or protected operation, create a default
 154          --  function for it, and replace the discriminant with a reference
 155          --  to the discriminant of the formal of the default function.
 156          --  The discriminant entity is the one defined in the corresponding
 157          --  record.
 158
 159          if Present (Parent_P)
 160            and then Present (Corresponding_Spec (Parent_P))
 161          then
 162
 163             declare
 164                Loc    : constant Source_Ptr := Sloc (N);
 165                D_Fun  : Entity_Id := Corresponding_Spec  (Parent_P);
 166                Formal : Entity_Id := First_Formal (D_Fun);
 167                New_N  : Node_Id;
 168                Disc   : Entity_Id;
 169
 170             begin
 171                --  Verify that we are within a default function: the type of
 172                --  its formal parameter is the same task or protected type.
 173
 174                if Present (Formal)
 175                  and then Etype (Formal) = Scope (Entity (N))
 176                then
 177                   Disc := CR_Discriminant (Entity (N));
 178
 179                   New_N :=
 180                     Make_Selected_Component (Loc,
 181                       Prefix => New_Occurrence_Of (Formal, Loc),
 182                       Selector_Name => New_Occurrence_Of (Disc, Loc));
 183
 184                   Set_Etype (New_N, Etype (N));
 185                   Rewrite (N, New_N);
 186
 187                else
 188                   Set_Entity (N, Discriminal (Entity (N)));
 189                end if;
 190             end;
 191
 192          elsif Nkind (Parent (N)) = N_Range
 193            and then In_Entry
 194          then
 195             Set_Entity (N, CR_Discriminant (Entity (N)));
 196          else
 197             Set_Entity (N, Discriminal (Entity (N)));
 198          end if;
 199
 200       else
 201          Set_Entity (N, Discriminal (Entity (N)));
 202       end if;
 203    end Expand_Discriminant;
 204
 205    -----------------------------
 206    -- Expand_Entity_Reference --
 207    -----------------------------
 208
 209    procedure Expand_Entity_Reference (N : Node_Id) is
 210       E : constant Entity_Id := Entity (N);
 211
 212    begin
 213       if Ekind (E) = E_Discriminant then
 214          Expand_Discriminant (N);
 215
 216       elsif Is_Entry_Formal (E) then
 217          Expand_Entry_Parameter (N);
 218
 219       elsif Ekind (E) = E_Component
 220         and then Is_Protected_Private (E)
 221       then
 222          Expand_Protected_Private (N);
 223
 224       elsif Ekind (E) = E_Entry_Index_Parameter then
 225          Expand_Entry_Index_Parameter (N);
 226
 227       elsif Is_Formal (E) then
 228          Expand_Formal (N);
 229
 230       elsif Is_Renaming_Of_Object (E) then
 231          Expand_Renaming (N);
 232
 233       elsif Ekind (E) = E_Variable
 234         and then Is_Shared_Passive (E)
 235       then
 236          Expand_Shared_Passive_Variable (N);
 237       end if;
 238    end Expand_Entity_Reference;
 239
 240    ----------------------------------
 241    -- Expand_Entry_Index_Parameter --
 242    ----------------------------------
 243
 244    procedure Expand_Entry_Index_Parameter (N : Node_Id) is
 245    begin
 246       Set_Entity (N, Entry_Index_Constant (Entity (N)));
 247    end Expand_Entry_Index_Parameter;
 248
 249    ----------------------------
 250    -- Expand_Entry_Parameter --
 251    ----------------------------
 252
 253    procedure Expand_Entry_Parameter (N : Node_Id) is
 254       Loc        : constant Source_Ptr := Sloc (N);
 255       Ent_Formal : constant Entity_Id  := Entity (N);
 256       Ent_Spec   : constant Entity_Id  := Scope (Ent_Formal);
 257       Parm_Type  : constant Entity_Id  := Entry_Parameters_Type (Ent_Spec);
 258       Acc_Stack  : constant Elist_Id   := Accept_Address (Ent_Spec);
 259       Addr_Ent   : constant Entity_Id  := Node (Last_Elmt (Acc_Stack));
 260       P_Comp_Ref : Entity_Id;
 261
 262    begin
 263       --  What we need is a reference to the corresponding component of the
 264       --  parameter record object. The Accept_Address field of the entry
 265       --  entity references the address variable that contains the address
 266       --  of the accept parameters record. We first have to do an unchecked
 267       --  conversion to turn this into a pointer to the parameter record and
 268       --  then we select the required parameter field.
 269
 270       P_Comp_Ref :=
 271         Make_Selected_Component (Loc,
 272           Prefix =>
 273             Unchecked_Convert_To (Parm_Type,
 274               New_Reference_To (Addr_Ent, Loc)),
 275           Selector_Name =>
 276             New_Reference_To (Entry_Component (Ent_Formal), Loc));
 277
 278       --  For all types of parameters, the constructed parameter record
 279       --  object contains a pointer to the parameter. Thus we must
 280       --  dereference them to access them (this will often be redundant,
 281       --  since the needed deference is implicit, but no harm is done by
 282       --  making it explicit).
 283
 284       Rewrite (N,
 285         Make_Explicit_Dereference (Loc, P_Comp_Ref));
 286
 287       Analyze (N);
 288    end Expand_Entry_Parameter;
 289
 290    -------------------
 291    -- Expand_Formal --
 292    -------------------
 293
 294    procedure Expand_Formal (N : Node_Id) is
 295       E    : constant Entity_Id  := Entity (N);
 296       Subp : constant Entity_Id  := Scope (E);
 297
 298    begin
 299       if Is_Protected_Type (Scope (Subp))
 300         and then Chars (Subp) /= Name_uInit_Proc
 301         and then Present (Protected_Formal (E))
 302       then
 303          Set_Entity (N, Protected_Formal (E));
 304       end if;
 305    end Expand_Formal;
 306
 307    ----------------------------
 308    -- Expand_N_Expanded_Name --
 309    ----------------------------
 310
 311    procedure Expand_N_Expanded_Name (N : Node_Id) is
 312    begin
 313       Expand_Entity_Reference (N);
 314    end Expand_N_Expanded_Name;
 315
 316    -------------------------
 317    -- Expand_N_Identifier --
 318    -------------------------
 319
 320    procedure Expand_N_Identifier (N : Node_Id) is
 321    begin
 322       Expand_Entity_Reference (N);
 323    end Expand_N_Identifier;
 324
 325    ---------------------------
 326    -- Expand_N_Real_Literal --
 327    ---------------------------
 328
 329    procedure Expand_N_Real_Literal (N : Node_Id) is
 330    begin
 331       if Vax_Float (Etype (N)) then
 332          Expand_Vax_Real_Literal (N);
 333       end if;
 334    end Expand_N_Real_Literal;
 335
 336    ------------------------------
 337    -- Expand_Protected_Private --
 338    ------------------------------
 339
 340    procedure Expand_Protected_Private (N : Node_Id) is
 341       Loc      : constant Source_Ptr := Sloc (N);
 342       E        : constant Entity_Id  := Entity (N);
 343       Op       : constant Node_Id    := Protected_Operation (E);
 344       Scop     : Entity_Id;
 345       Lo       : Node_Id;
 346       Hi       : Node_Id;
 347       D_Range  : Node_Id;
 348
 349    begin
 350       if Nkind (Op) /= N_Subprogram_Body
 351         or else Nkind (Specification (Op)) /= N_Function_Specification
 352       then
 353          Set_Ekind (Prival (E), E_Variable);
 354       else
 355          Set_Ekind (Prival (E), E_Constant);
 356       end if;
 357
 358       --  If the private component appears in an assignment (either lhs or
 359       --  rhs) and is a one-dimensional array constrained by a discriminant,
 360       --  rewrite as  P (Lo .. Hi) with an explicit range, so that discriminal
 361       --  is directly visible. This solves delicate visibility problems.
 362
 363       if Comes_From_Source (N)
 364         and then Is_Array_Type (Etype (E))
 365         and then Number_Dimensions (Etype (E)) = 1
 366         and then not Within_Init_Proc
 367       then
 368          Lo := Type_Low_Bound  (Etype (First_Index (Etype (E))));
 369          Hi := Type_High_Bound (Etype (First_Index (Etype (E))));
 370
 371          if Nkind (Parent (N)) = N_Assignment_Statement
 372            and then ((Is_Entity_Name (Lo)
 373                           and then Ekind (Entity (Lo)) = E_In_Parameter)
 374                        or else (Is_Entity_Name (Hi)
 375                                   and then
 376                                     Ekind (Entity (Hi)) = E_In_Parameter))
 377          then
 378             D_Range := New_Node (N_Range, Loc);
 379
 380             if Is_Entity_Name (Lo)
 381               and then Ekind (Entity (Lo)) = E_In_Parameter
 382             then
 383                Set_Low_Bound (D_Range,
 384                  Make_Identifier (Loc, Chars (Entity (Lo))));
 385             else
 386                Set_Low_Bound (D_Range, Duplicate_Subexpr (Lo));
 387             end if;
 388
 389             if Is_Entity_Name (Hi)
 390               and then Ekind (Entity (Hi)) = E_In_Parameter
 391             then
 392                Set_High_Bound (D_Range,
 393                  Make_Identifier (Loc, Chars (Entity (Hi))));
 394             else
 395                Set_High_Bound (D_Range, Duplicate_Subexpr (Hi));
 396             end if;
 397
 398             Rewrite (N,
 399               Make_Slice (Loc,
 400                 Prefix => New_Occurrence_Of (E, Loc),
 401                 Discrete_Range => D_Range));
 402
 403             Analyze_And_Resolve (N, Etype (E));
 404             return;
 405          end if;
 406       end if;
 407
 408       --  The type of the reference is the type of the prival, which may
 409       --  differ from that of the original component if it is an itype.
 410
 411       Set_Entity (N, Prival (E));
 412       Set_Etype  (N, Etype (Prival (E)));
 413       Scop := Current_Scope;
 414
 415       --  Find entity for protected operation, which must be on scope stack.
 416
 417       while not Is_Protected_Type (Scope (Scop)) loop
 418          Scop := Scope (Scop);
 419       end loop;
 420
 421       Append_Elmt (N, Privals_Chain (Scop));
 422    end Expand_Protected_Private;
 423
 424    ---------------------
 425    -- Expand_Renaming --
 426    ---------------------
 427
 428    procedure Expand_Renaming (N : Node_Id) is
 429       E : constant Entity_Id := Entity (N);
 430       T : constant Entity_Id := Etype (N);
 431
 432    begin
 433       Rewrite (N, New_Copy_Tree (Renamed_Object (E)));
 434
 435       --  We mark the copy as unanalyzed, so that it is sure to be
 436       --  reanalyzed at the top level. This is needed in the packed
 437       --  case since we specifically avoided expanding packed array
 438       --  references when the renaming declaration was analyzed.
 439
 440       Reset_Analyzed_Flags (N);
 441       Analyze_And_Resolve (N, T);
 442    end Expand_Renaming;
 443
 444    ------------------
 445    -- Param_Entity --
 446    ------------------
 447
 448    --  This would be trivial, simply a test for an identifier that was a
 449    --  reference to a formal, if it were not for the fact that a previous
 450    --  call to Expand_Entry_Parameter will have modified the reference
 451    --  to the identifier to be of the form
 452
 453    --    typ!(recobj).rec.all'Constrained
 454
 455    --  where rec is a selector whose Entry_Formal link points to the formal
 456
 457    function Param_Entity (N : Node_Id) return Entity_Id is
 458    begin
 459       --  Simple reference case
 460
 461       if Nkind (N) = N_Identifier then
 462          if Is_Formal (Entity (N)) then
 463             return Entity (N);
 464          end if;
 465
 466       else
 467          if Nkind (N) = N_Explicit_Dereference then
 468             declare
 469                P : constant Node_Id := Prefix (N);
 470                S : Node_Id;
 471
 472             begin
 473                if Nkind (P) = N_Selected_Component then
 474                   S := Selector_Name (P);
 475
 476                   if Present (Entry_Formal (Entity (S))) then
 477                      return Entry_Formal (Entity (S));
 478                   end if;
 479                end if;
 480             end;
 481          end if;
 482       end if;
 483
 484       return (Empty);
 485    end Param_Entity;
 486
 487 end Exp_Ch2;