gcc/ada/sem_elim.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                             S E M _ E L I M                              --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1997-2010, 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 with Atree;    use Atree;
  27 with Einfo;    use Einfo;
  28 with Errout;   use Errout;
  29 with Lib;      use Lib;
  30 with Namet;    use Namet;
  31 with Nlists;   use Nlists;
  32 with Opt;      use Opt;
  33 with Sem;      use Sem;
  34 with Sem_Aux;  use Sem_Aux;
  35 with Sem_Prag; use Sem_Prag;
  36 with Sem_Util; use Sem_Util;
  37 with Sinput;   use Sinput;
  38 with Sinfo;    use Sinfo;
  39 with Snames;   use Snames;
  40 with Stand;    use Stand;
  41 with Stringt;  use Stringt;
  42 with Table;
  43
  44 with GNAT.HTable; use GNAT.HTable;
  45
  46 package body Sem_Elim is
  47
  48    No_Elimination : Boolean;
  49    --  Set True if no Eliminate pragmas active
  50
  51    ---------------------
  52    -- Data Structures --
  53    ---------------------
  54
  55    --  A single pragma Eliminate is represented by the following record
  56
  57    type Elim_Data;
  58    type Access_Elim_Data is access Elim_Data;
  59
  60    type Names is array (Nat range <>) of Name_Id;
  61    --  Type used to represent set of names. Used for names in Unit_Name
  62    --  and also the set of names in Argument_Types.
  63
  64    type Access_Names is access Names;
  65
  66    type Elim_Data is record
  67
  68       Unit_Name : Access_Names;
  69       --  Unit name, broken down into a set of names (e.g. A.B.C is
  70       --  represented as Name_Id values for A, B, C in sequence).
  71
  72       Entity_Name : Name_Id;
  73       --  Entity name if Entity parameter if present. If no Entity parameter
  74       --  was supplied, then Entity_Node is set to Empty, and the Entity_Name
  75       --  field contains the last identifier name in the Unit_Name.
  76
  77       Entity_Scope : Access_Names;
  78       --  Static scope of the entity within the compilation unit represented by
  79       --  Unit_Name.
  80
  81       Entity_Node : Node_Id;
  82       --  Save node of entity argument, for posting error messages. Set
  83       --  to Empty if there is no entity argument.
  84
  85       Parameter_Types : Access_Names;
  86       --  Set to set of names given for parameter types. If no parameter
  87       --  types argument is present, this argument is set to null.
  88
  89       Result_Type : Name_Id;
  90       --  Result type name if Result_Types parameter present, No_Name if not
  91
  92       Source_Location : Name_Id;
  93       --  String describing the source location of subprogram defining name if
  94       --  Source_Location parameter present, No_Name if not
  95
  96       Hash_Link : Access_Elim_Data;
  97       --  Link for hash table use
  98
  99       Homonym : Access_Elim_Data;
 100       --  Pointer to next entry with same key
 101
 102       Prag : Node_Id;
 103       --  Node_Id for Eliminate pragma
 104
 105    end record;
 106
 107    ----------------
 108    -- Hash_Table --
 109    ----------------
 110
 111    --  Setup hash table using the Entity_Name field as the hash key
 112
 113    subtype Element is Elim_Data;
 114    subtype Elmt_Ptr is Access_Elim_Data;
 115
 116    subtype Key is Name_Id;
 117
 118    type Header_Num is range 0 .. 1023;
 119
 120    Null_Ptr : constant Elmt_Ptr := null;
 121
 122    ----------------------
 123    -- Hash_Subprograms --
 124    ----------------------
 125
 126    package Hash_Subprograms is
 127
 128       function Equal (F1, F2 : Key) return Boolean;
 129       pragma Inline (Equal);
 130
 131       function Get_Key (E : Elmt_Ptr) return Key;
 132       pragma Inline (Get_Key);
 133
 134       function Hash (F : Key) return Header_Num;
 135       pragma Inline (Hash);
 136
 137       function Next (E : Elmt_Ptr) return Elmt_Ptr;
 138       pragma Inline (Next);
 139
 140       procedure Set_Next (E : Elmt_Ptr; Next : Elmt_Ptr);
 141       pragma Inline (Set_Next);
 142
 143    end Hash_Subprograms;
 144
 145    package body Hash_Subprograms is
 146
 147       -----------
 148       -- Equal --
 149       -----------
 150
 151       function Equal (F1, F2 : Key) return Boolean is
 152       begin
 153          return F1 = F2;
 154       end Equal;
 155
 156       -------------
 157       -- Get_Key --
 158       -------------
 159
 160       function Get_Key (E : Elmt_Ptr) return Key is
 161       begin
 162          return E.Entity_Name;
 163       end Get_Key;
 164
 165       ----------
 166       -- Hash --
 167       ----------
 168
 169       function Hash (F : Key) return Header_Num is
 170       begin
 171          return Header_Num (Int (F) mod 1024);
 172       end Hash;
 173
 174       ----------
 175       -- Next --
 176       ----------
 177
 178       function Next (E : Elmt_Ptr) return Elmt_Ptr is
 179       begin
 180          return E.Hash_Link;
 181       end Next;
 182
 183       --------------
 184       -- Set_Next --
 185       --------------
 186
 187       procedure Set_Next (E : Elmt_Ptr; Next : Elmt_Ptr) is
 188       begin
 189          E.Hash_Link := Next;
 190       end Set_Next;
 191    end Hash_Subprograms;
 192
 193    ------------
 194    -- Tables --
 195    ------------
 196
 197    --  The following table records the data for each pragmas, using the
 198    --  entity name as the hash key for retrieval. Entries in this table
 199    --  are set by Process_Eliminate_Pragma and read by Check_Eliminated.
 200
 201    package Elim_Hash_Table is new Static_HTable (
 202       Header_Num => Header_Num,
 203       Element    => Element,
 204       Elmt_Ptr   => Elmt_Ptr,
 205       Null_Ptr   => Null_Ptr,
 206       Set_Next   => Hash_Subprograms.Set_Next,
 207       Next       => Hash_Subprograms.Next,
 208       Key        => Key,
 209       Get_Key    => Hash_Subprograms.Get_Key,
 210       Hash       => Hash_Subprograms.Hash,
 211       Equal      => Hash_Subprograms.Equal);
 212
 213    --  The following table records entities for subprograms that are
 214    --  eliminated, and corresponding eliminate pragmas that caused the
 215    --  elimination. Entries in this table are set by Check_Eliminated
 216    --  and read by Eliminate_Error_Msg.
 217
 218    type Elim_Entity_Entry is record
 219       Prag : Node_Id;
 220       Subp : Entity_Id;
 221    end record;
 222
 223    package Elim_Entities is new Table.Table (
 224      Table_Component_Type => Elim_Entity_Entry,
 225      Table_Index_Type     => Name_Id'Base,
 226      Table_Low_Bound      => First_Name_Id,
 227      Table_Initial        => 50,
 228      Table_Increment      => 200,
 229      Table_Name           => "Elim_Entries");
 230
 231    ----------------------
 232    -- Check_Eliminated --
 233    ----------------------
 234
 235    procedure Check_Eliminated (E : Entity_Id) is
 236       Elmt : Access_Elim_Data;
 237       Scop : Entity_Id;
 238       Form : Entity_Id;
 239       Up   : Nat;
 240
 241    begin
 242       if No_Elimination then
 243          return;
 244
 245       --  Elimination of objects and types is not implemented yet
 246
 247       elsif Ekind (E) not in Subprogram_Kind then
 248          return;
 249       end if;
 250
 251       --  Loop through homonyms for this key
 252
 253       Elmt := Elim_Hash_Table.Get (Chars (E));
 254       while Elmt /= null loop
 255          Check_Homonyms : declare
 256             procedure Set_Eliminated;
 257             --  Set current subprogram entity as eliminated
 258
 259             --------------------
 260             -- Set_Eliminated --
 261             --------------------
 262
 263             procedure Set_Eliminated is
 264             begin
 265                if Is_Dispatching_Operation (E) then
 266
 267                   --  If an overriding dispatching primitive is eliminated then
 268                   --  its parent must have been eliminated.
 269
 270                   if Is_Overriding_Operation (E)
 271                     and then not Is_Eliminated (Overridden_Operation (E))
 272                   then
 273                      Error_Msg_Name_1 := Chars (E);
 274                      Error_Msg_N ("cannot eliminate subprogram %", E);
 275                      return;
 276                   end if;
 277                end if;
 278
 279                Set_Is_Eliminated (E);
 280                Elim_Entities.Append ((Prag => Elmt.Prag, Subp => E));
 281             end Set_Eliminated;
 282
 283          --  Start of processing for Check_Homonyms
 284
 285          begin
 286             --  First we check that the name of the entity matches
 287
 288             if Elmt.Entity_Name /= Chars (E) then
 289                goto Continue;
 290             end if;
 291
 292             --  Find enclosing unit, and verify that its name and those of its
 293             --  parents match.
 294
 295             Scop := Cunit_Entity (Current_Sem_Unit);
 296
 297             --  Now see if compilation unit matches
 298
 299             Up := Elmt.Unit_Name'Last;
 300
 301             --  If we are within a subunit, the name in the pragma has been
 302             --  parsed as a child unit, but the current compilation unit is in
 303             --  fact the parent in which the subunit is embedded. We must skip
 304             --  the first name which is that of the subunit to match the pragma
 305             --  specification. Body may be that of a package or subprogram.
 306
 307             declare
 308                Par : Node_Id;
 309
 310             begin
 311                Par := Parent (E);
 312                while Present (Par) loop
 313                   if Nkind (Par) = N_Subunit then
 314                      if Chars (Defining_Entity (Proper_Body (Par))) =
 315                                                          Elmt.Unit_Name (Up)
 316                      then
 317                         Up := Up - 1;
 318                         exit;
 319
 320                      else
 321                         goto Continue;
 322                      end if;
 323                   end if;
 324
 325                   Par := Parent (Par);
 326                end loop;
 327             end;
 328
 329             for J in reverse Elmt.Unit_Name'First .. Up loop
 330                if Elmt.Unit_Name (J) /= Chars (Scop) then
 331                   goto Continue;
 332                end if;
 333
 334                Scop := Scope (Scop);
 335
 336                if Scop /= Standard_Standard and then J = 1 then
 337                   goto Continue;
 338                end if;
 339             end loop;
 340
 341             if Scop /= Standard_Standard then
 342                goto Continue;
 343             end if;
 344
 345             if Present (Elmt.Entity_Node)
 346               and then Elmt.Entity_Scope /= null
 347             then
 348                --  Check that names of enclosing scopes match. Skip blocks and
 349                --  wrapper package of subprogram instances, which do not appear
 350                --  in the pragma.
 351
 352                Scop := Scope (E);
 353
 354                for J in reverse  Elmt.Entity_Scope'Range loop
 355                   while Ekind (Scop) = E_Block
 356                     or else
 357                      (Ekind (Scop) = E_Package
 358                        and then Is_Wrapper_Package (Scop))
 359                   loop
 360                      Scop := Scope (Scop);
 361                   end loop;
 362
 363                   if Elmt.Entity_Scope (J) /= Chars (Scop) then
 364                      if Ekind (Scop) /= E_Protected_Type
 365                        or else Comes_From_Source (Scop)
 366                      then
 367                         goto Continue;
 368
 369                      --  For simple protected declarations, retrieve the source
 370                      --  name of the object, which appeared in the Eliminate
 371                      --  pragma.
 372
 373                      else
 374                         declare
 375                            Decl : constant Node_Id :=
 376                              Original_Node (Parent (Scop));
 377
 378                         begin
 379                            if Elmt.Entity_Scope (J) /=
 380                              Chars (Defining_Identifier (Decl))
 381                            then
 382                               if J > 0 then
 383                                  null;
 384                               end if;
 385                               goto Continue;
 386                            end if;
 387                         end;
 388                      end if;
 389
 390                   end if;
 391
 392                   Scop := Scope (Scop);
 393                end loop;
 394             end if;
 395
 396             --  If given entity is a library level subprogram and pragma had a
 397             --  single parameter, a match!
 398
 399             if Is_Compilation_Unit (E)
 400               and then Is_Subprogram (E)
 401               and then No (Elmt.Entity_Node)
 402             then
 403                Set_Eliminated;
 404                return;
 405
 406                --  Check for case of type or object with two parameter case
 407
 408             elsif (Is_Type (E) or else Is_Object (E))
 409               and then Elmt.Result_Type = No_Name
 410               and then Elmt.Parameter_Types = null
 411             then
 412                Set_Eliminated;
 413                return;
 414
 415             --  Check for case of subprogram
 416
 417             elsif Ekind_In (E, E_Function, E_Procedure) then
 418
 419                --  If Source_Location present, then see if it matches
 420
 421                if Elmt.Source_Location /= No_Name then
 422                   Get_Name_String (Elmt.Source_Location);
 423
 424                   declare
 425                      Sloc_Trace : constant String :=
 426                                     Name_Buffer (1 .. Name_Len);
 427
 428                      Idx : Natural := Sloc_Trace'First;
 429                      --  Index in Sloc_Trace, if equals to 0, then we have
 430                      --  completely traversed Sloc_Trace
 431
 432                      Last : constant Natural := Sloc_Trace'Last;
 433
 434                      P      : Source_Ptr;
 435                      Sindex : Source_File_Index;
 436
 437                      function File_Name_Match return Boolean;
 438                      --  This function is supposed to be called when Idx points
 439                      --  to the beginning of the new file name, and Name_Buffer
 440                      --  is set to contain the name of the proper source file
 441                      --  from the chain corresponding to the Sloc of E. First
 442                      --  it checks that these two files have the same name. If
 443                      --  this check is successful, moves Idx to point to the
 444                      --  beginning of the column number.
 445
 446                      function Line_Num_Match return Boolean;
 447                      --  This function is supposed to be called when Idx points
 448                      --  to the beginning of the column number, and P is
 449                      --  set to point to the proper Sloc the chain
 450                      --  corresponding to the Sloc of E. First it checks that
 451                      --  the line number Idx points on and the line number
 452                      --  corresponding to P are the same. If this check is
 453                      --  successful, moves Idx to point to the beginning of
 454                      --  the next file name in Sloc_Trace. If there is no file
 455                      --  name any more, Idx is set to 0.
 456
 457                      function Different_Trace_Lengths return Boolean;
 458                      --  From Idx and P, defines if there are in both traces
 459                      --  more element(s) in the instantiation chains. Returns
 460                      --  False if one trace contains more element(s), but
 461                      --  another does not. If both traces contains more
 462                      --  elements (that is, the function returns False), moves
 463                      --  P ahead in the chain corresponding to E, recomputes
 464                      --  Sindex and sets the name of the corresponding file in
 465                      --  Name_Buffer
 466
 467                      function Skip_Spaces return Natural;
 468                      --  If Sloc_Trace (Idx) is not space character, returns
 469                      --  Idx. Otherwise returns the index of the nearest
 470                      --  non-space character in Sloc_Trace to the right of Idx.
 471                      --  Returns 0 if there is no such character.
 472
 473                      -----------------------------
 474                      -- Different_Trace_Lengths --
 475                      -----------------------------
 476
 477                      function Different_Trace_Lengths return Boolean is
 478                      begin
 479                         P := Instantiation (Sindex);
 480
 481                         if (P = No_Location and then Idx /= 0)
 482                           or else
 483                            (P /= No_Location and then Idx = 0)
 484                         then
 485                            return True;
 486
 487                         else
 488                            if P /= No_Location then
 489                               Sindex := Get_Source_File_Index (P);
 490                               Get_Name_String (File_Name (Sindex));
 491                            end if;
 492
 493                            return False;
 494                         end if;
 495                      end Different_Trace_Lengths;
 496
 497                      ---------------------
 498                      -- File_Name_Match --
 499                      ---------------------
 500
 501                      function File_Name_Match return Boolean is
 502                         Tmp_Idx : Natural;
 503                         End_Idx : Natural;
 504
 505                      begin
 506                         if Idx = 0 then
 507                            return False;
 508                         end if;
 509
 510                         --  Find first colon. If no colon, then return False.
 511                         --  If there is a colon, Tmp_Idx is set to point just
 512                         --  before the colon.
 513
 514                         Tmp_Idx := Idx - 1;
 515                         loop
 516                            if Tmp_Idx >= Last then
 517                               return False;
 518                            elsif Sloc_Trace (Tmp_Idx + 1) = ':' then
 519                               exit;
 520                            else
 521                               Tmp_Idx := Tmp_Idx + 1;
 522                            end if;
 523                         end loop;
 524
 525                         --  Find last non-space before this colon. If there is
 526                         --  no space character before this colon, then return
 527                         --  False. Otherwise, End_Idx is set to point to this
 528                         --  non-space character.
 529
 530                         End_Idx := Tmp_Idx;
 531                         loop
 532                            if End_Idx < Idx then
 533                               return False;
 534
 535                            elsif Sloc_Trace (End_Idx) /= ' ' then
 536                               exit;
 537
 538                            else
 539                               End_Idx := End_Idx - 1;
 540                            end if;
 541                         end loop;
 542
 543                         --  Now see if file name matches what is in Name_Buffer
 544                         --  and if so, step Idx past it and return True. If the
 545                         --  name does not match, return False.
 546
 547                         if Sloc_Trace (Idx .. End_Idx) =
 548                            Name_Buffer (1 .. Name_Len)
 549                         then
 550                            Idx := Tmp_Idx + 2;
 551                            Idx := Skip_Spaces;
 552                            return True;
 553                         else
 554                            return False;
 555                         end if;
 556                      end File_Name_Match;
 557
 558                      --------------------
 559                      -- Line_Num_Match --
 560                      --------------------
 561
 562                      function Line_Num_Match return Boolean is
 563                         N : Int := 0;
 564
 565                      begin
 566                         if Idx = 0 then
 567                            return False;
 568                         end if;
 569
 570                         while Idx <= Last
 571                            and then Sloc_Trace (Idx) in '0' .. '9'
 572                         loop
 573                            N := N * 10 +
 574                             (Character'Pos (Sloc_Trace (Idx)) -
 575                              Character'Pos ('0'));
 576                            Idx := Idx + 1;
 577                         end loop;
 578
 579                         if Get_Physical_Line_Number (P) =
 580                            Physical_Line_Number (N)
 581                         then
 582                            while Idx <= Last and then
 583                               Sloc_Trace (Idx) /= '['
 584                            loop
 585                               Idx := Idx + 1;
 586                            end loop;
 587
 588                            if Idx <= Last and then
 589                              Sloc_Trace (Idx) = '['
 590                            then
 591                               Idx := Idx + 1;
 592                               Idx := Skip_Spaces;
 593                            else
 594                               Idx := 0;
 595                            end if;
 596
 597                            return True;
 598
 599                         else
 600                            return False;
 601                         end if;
 602                      end Line_Num_Match;
 603
 604                      -----------------
 605                      -- Skip_Spaces --
 606                      -----------------
 607
 608                      function Skip_Spaces return Natural is
 609                         Res : Natural;
 610
 611                      begin
 612                         Res := Idx;
 613                         while Sloc_Trace (Res) = ' ' loop
 614                            Res := Res + 1;
 615
 616                            if Res > Last then
 617                               Res := 0;
 618                               exit;
 619                            end if;
 620                         end loop;
 621
 622                         return Res;
 623                      end Skip_Spaces;
 624
 625                   begin
 626                      P := Sloc (E);
 627                      Sindex := Get_Source_File_Index (P);
 628                      Get_Name_String (File_Name (Sindex));
 629
 630                      Idx := Skip_Spaces;
 631                      while Idx > 0 loop
 632                         if not File_Name_Match then
 633                            goto Continue;
 634                         elsif not Line_Num_Match then
 635                            goto Continue;
 636                         end if;
 637
 638                         if Different_Trace_Lengths then
 639                            goto Continue;
 640                         end if;
 641                      end loop;
 642                   end;
 643                end if;
 644
 645                --  If we have a Result_Type, then we must have a function with
 646                --  the proper result type.
 647
 648                if Elmt.Result_Type /= No_Name then
 649                   if Ekind (E) /= E_Function
 650                     or else Chars (Etype (E)) /= Elmt.Result_Type
 651                   then
 652                      goto Continue;
 653                   end if;
 654                end if;
 655
 656                --  If we have Parameter_Types, they must match
 657
 658                if Elmt.Parameter_Types /= null then
 659                   Form := First_Formal (E);
 660
 661                   if No (Form)
 662                     and then Elmt.Parameter_Types'Length = 1
 663                     and then Elmt.Parameter_Types (1) = No_Name
 664                   then
 665                      --  Parameterless procedure matches
 666
 667                      null;
 668
 669                   elsif Elmt.Parameter_Types = null then
 670                      goto Continue;
 671
 672                   else
 673                      for J in Elmt.Parameter_Types'Range loop
 674                         if No (Form)
 675                           or else
 676                             Chars (Etype (Form)) /= Elmt.Parameter_Types (J)
 677                         then
 678                            goto Continue;
 679                         else
 680                            Next_Formal (Form);
 681                         end if;
 682                      end loop;
 683
 684                      if Present (Form) then
 685                         goto Continue;
 686                      end if;
 687                   end if;
 688                end if;
 689
 690                --  If we fall through, this is match
 691
 692                Set_Eliminated;
 693                return;
 694             end if;
 695          end Check_Homonyms;
 696
 697       <<Continue>>
 698          Elmt := Elmt.Homonym;
 699       end loop;
 700
 701       return;
 702    end Check_Eliminated;
 703
 704    -------------------------------------
 705    -- Check_For_Eliminated_Subprogram --
 706    -------------------------------------
 707
 708    procedure Check_For_Eliminated_Subprogram (N : Node_Id; S : Entity_Id) is
 709       Ultimate_Subp  : constant Entity_Id := Ultimate_Alias (S);
 710       Enclosing_Subp : Entity_Id;
 711
 712    begin
 713       if Is_Eliminated (Ultimate_Subp)
 714         and then not Inside_A_Generic
 715         and then not Is_Generic_Unit (Cunit_Entity (Current_Sem_Unit))
 716       then
 717          Enclosing_Subp := Current_Subprogram;
 718          while Present (Enclosing_Subp) loop
 719             if Is_Eliminated (Enclosing_Subp) then
 720                return;
 721             end if;
 722
 723             Enclosing_Subp := Enclosing_Subprogram (Enclosing_Subp);
 724          end loop;
 725
 726          --  Emit error, unless we are within an instance body and the expander
 727          --  is disabled, indicating an instance within an enclosing generic.
 728          --  In an instance, the ultimate alias is an internal entity, so place
 729          --  the message on the original subprogram.
 730
 731          if In_Instance_Body and then not Expander_Active then
 732             null;
 733
 734          elsif Comes_From_Source (Ultimate_Subp) then
 735             Eliminate_Error_Msg (N, Ultimate_Subp);
 736
 737          else
 738             Eliminate_Error_Msg (N, S);
 739          end if;
 740       end if;
 741    end Check_For_Eliminated_Subprogram;
 742
 743    -------------------------
 744    -- Eliminate_Error_Msg --
 745    -------------------------
 746
 747    procedure Eliminate_Error_Msg (N : Node_Id; E : Entity_Id) is
 748    begin
 749       for J in Elim_Entities.First .. Elim_Entities.Last loop
 750          if E = Elim_Entities.Table (J).Subp then
 751             Error_Msg_Sloc := Sloc (Elim_Entities.Table (J).Prag);
 752             Error_Msg_NE ("cannot reference subprogram & eliminated #", N, E);
 753             return;
 754          end if;
 755       end loop;
 756
 757       --  If this is an internal operation generated for a protected operation,
 758       --  its name does not match the source name, so just report the error.
 759
 760       if not Comes_From_Source (E)
 761         and then Present (First_Entity (E))
 762         and then Is_Concurrent_Record_Type (Etype (First_Entity (E)))
 763       then
 764          Error_Msg_NE
 765            ("cannot reference eliminated protected subprogram", N, E);
 766
 767       --  Otherwise should not fall through, entry should be in table
 768
 769       else
 770          Error_Msg_NE
 771            ("subprogram& is called but its alias is eliminated", N, E);
 772          --  raise Program_Error;
 773       end if;
 774    end Eliminate_Error_Msg;
 775
 776    ----------------
 777    -- Initialize --
 778    ----------------
 779
 780    procedure Initialize is
 781    begin
 782       Elim_Hash_Table.Reset;
 783       Elim_Entities.Init;
 784       No_Elimination := True;
 785    end Initialize;
 786
 787    ------------------------------
 788    -- Process_Eliminate_Pragma --
 789    ------------------------------
 790
 791    procedure Process_Eliminate_Pragma
 792      (Pragma_Node         : Node_Id;
 793       Arg_Unit_Name       : Node_Id;
 794       Arg_Entity          : Node_Id;
 795       Arg_Parameter_Types : Node_Id;
 796       Arg_Result_Type     : Node_Id;
 797       Arg_Source_Location : Node_Id)
 798    is
 799       Data : constant Access_Elim_Data := new Elim_Data;
 800       --  Build result data here
 801
 802       Elmt : Access_Elim_Data;
 803
 804       Num_Names : Nat := 0;
 805       --  Number of names in unit name
 806
 807       Lit       : Node_Id;
 808       Arg_Ent   : Entity_Id;
 809       Arg_Uname : Node_Id;
 810
 811       function OK_Selected_Component (N : Node_Id) return Boolean;
 812       --  Test if N is a selected component with all identifiers, or a
 813       --  selected component whose selector is an operator symbol. As a
 814       --  side effect if result is True, sets Num_Names to the number
 815       --  of names present (identifiers and operator if any).
 816
 817       ---------------------------
 818       -- OK_Selected_Component --
 819       ---------------------------
 820
 821       function OK_Selected_Component (N : Node_Id) return Boolean is
 822       begin
 823          if Nkind (N) = N_Identifier
 824            or else Nkind (N) = N_Operator_Symbol
 825          then
 826             Num_Names := Num_Names + 1;
 827             return True;
 828
 829          elsif Nkind (N) = N_Selected_Component then
 830             return OK_Selected_Component (Prefix (N))
 831               and then OK_Selected_Component (Selector_Name (N));
 832
 833          else
 834             return False;
 835          end if;
 836       end OK_Selected_Component;
 837
 838    --  Start of processing for Process_Eliminate_Pragma
 839
 840    begin
 841       Data.Prag := Pragma_Node;
 842       Error_Msg_Name_1 := Name_Eliminate;
 843
 844       --  Process Unit_Name argument
 845
 846       if Nkind (Arg_Unit_Name) = N_Identifier then
 847          Data.Unit_Name := new Names'(1 => Chars (Arg_Unit_Name));
 848          Num_Names := 1;
 849
 850       elsif OK_Selected_Component (Arg_Unit_Name) then
 851          Data.Unit_Name := new Names (1 .. Num_Names);
 852
 853          Arg_Uname := Arg_Unit_Name;
 854          for J in reverse 2 .. Num_Names loop
 855             Data.Unit_Name (J) := Chars (Selector_Name (Arg_Uname));
 856             Arg_Uname := Prefix (Arg_Uname);
 857          end loop;
 858
 859          Data.Unit_Name (1) := Chars (Arg_Uname);
 860
 861       else
 862          Error_Msg_N
 863            ("wrong form for Unit_Name parameter of pragma%", Arg_Unit_Name);
 864          return;
 865       end if;
 866
 867       --  Process Entity argument
 868
 869       if Present (Arg_Entity) then
 870          Num_Names := 0;
 871
 872          if Nkind (Arg_Entity) = N_Identifier
 873            or else Nkind (Arg_Entity) = N_Operator_Symbol
 874          then
 875             Data.Entity_Name  := Chars (Arg_Entity);
 876             Data.Entity_Node  := Arg_Entity;
 877             Data.Entity_Scope := null;
 878
 879          elsif OK_Selected_Component (Arg_Entity) then
 880             Data.Entity_Scope := new Names (1 .. Num_Names - 1);
 881             Data.Entity_Name  := Chars (Selector_Name (Arg_Entity));
 882             Data.Entity_Node  := Arg_Entity;
 883
 884             Arg_Ent := Prefix (Arg_Entity);
 885             for J in reverse 2 .. Num_Names - 1 loop
 886                Data.Entity_Scope (J) := Chars (Selector_Name (Arg_Ent));
 887                Arg_Ent := Prefix (Arg_Ent);
 888             end loop;
 889
 890             Data.Entity_Scope (1) := Chars (Arg_Ent);
 891
 892          elsif Is_Config_Static_String (Arg_Entity) then
 893             Data.Entity_Name := Name_Find;
 894             Data.Entity_Node := Arg_Entity;
 895
 896          else
 897             return;
 898          end if;
 899       else
 900          Data.Entity_Node := Empty;
 901          Data.Entity_Name := Data.Unit_Name (Num_Names);
 902       end if;
 903
 904       --  Process Parameter_Types argument
 905
 906       if Present (Arg_Parameter_Types) then
 907
 908          --  Here for aggregate case
 909
 910          if Nkind (Arg_Parameter_Types) = N_Aggregate then
 911             Data.Parameter_Types :=
 912               new Names
 913                 (1 .. List_Length (Expressions (Arg_Parameter_Types)));
 914
 915             Lit := First (Expressions (Arg_Parameter_Types));
 916             for J in Data.Parameter_Types'Range loop
 917                if Is_Config_Static_String (Lit) then
 918                   Data.Parameter_Types (J) := Name_Find;
 919                   Next (Lit);
 920                else
 921                   return;
 922                end if;
 923             end loop;
 924
 925          --  Otherwise we must have case of one name, which looks like a
 926          --  parenthesized literal rather than an aggregate.
 927
 928          elsif Paren_Count (Arg_Parameter_Types) /= 1 then
 929             Error_Msg_N
 930               ("wrong form for argument of pragma Eliminate",
 931                Arg_Parameter_Types);
 932             return;
 933
 934          elsif Is_Config_Static_String (Arg_Parameter_Types) then
 935             String_To_Name_Buffer (Strval (Arg_Parameter_Types));
 936
 937             if Name_Len = 0 then
 938
 939                --  Parameterless procedure
 940
 941                Data.Parameter_Types := new Names'(1 => No_Name);
 942
 943             else
 944                Data.Parameter_Types := new Names'(1 => Name_Find);
 945             end if;
 946
 947          else
 948             return;
 949          end if;
 950       end if;
 951
 952       --  Process Result_Types argument
 953
 954       if Present (Arg_Result_Type) then
 955          if Is_Config_Static_String (Arg_Result_Type) then
 956             Data.Result_Type := Name_Find;
 957          else
 958             return;
 959          end if;
 960
 961       --  Here if no Result_Types argument
 962
 963       else
 964          Data.Result_Type := No_Name;
 965       end if;
 966
 967       --  Process Source_Location argument
 968
 969       if Present (Arg_Source_Location) then
 970          if Is_Config_Static_String (Arg_Source_Location) then
 971             Data.Source_Location := Name_Find;
 972          else
 973             return;
 974          end if;
 975       else
 976          Data.Source_Location := No_Name;
 977       end if;
 978
 979       Elmt := Elim_Hash_Table.Get (Hash_Subprograms.Get_Key (Data));
 980
 981       --  If we already have an entry with this same key, then link
 982       --  it into the chain of entries for this key.
 983
 984       if Elmt /= null then
 985          Data.Homonym := Elmt.Homonym;
 986          Elmt.Homonym := Data;
 987
 988       --  Otherwise create a new entry
 989
 990       else
 991          Elim_Hash_Table.Set (Data);
 992       end if;
 993
 994       No_Elimination := False;
 995    end Process_Eliminate_Pragma;
 996
 997 end Sem_Elim;