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 --          Copyright (C) 1992-2007, 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 with Atree;    use Atree;
  27 with Einfo;    use Einfo;
  28 with Elists;   use Elists;
  29 with Errout;   use Errout;
  30 with Exp_Smem; use Exp_Smem;
  31 with Exp_Tss;  use Exp_Tss;
  32 with Exp_Util; use Exp_Util;
  33 with Exp_VFpt; use Exp_VFpt;
  34 with Namet;    use Namet;
  35 with Nmake;    use Nmake;
  36 with Opt;      use Opt;
  37 with Sem;      use Sem;
  38 with Sem_Eval; use Sem_Eval;
  39 with Sem_Res;  use Sem_Res;
  40 with Sem_Util; use Sem_Util;
  41 with Sem_Warn; use Sem_Warn;
  42 with Sinfo;    use Sinfo;
  43 with Snames;   use Snames;
  44 with Tbuild;   use Tbuild;
  45 with Uintp;    use Uintp;
  46
  47 package body Exp_Ch2 is
  48
  49    -----------------------
  50    -- Local Subprograms --
  51    -----------------------
  52
  53    procedure Expand_Current_Value (N : Node_Id);
  54    --  N is a node for a variable whose Current_Value field is set. If N is
  55    --  node is for a discrete type, replaces node with a copy of the referenced
  56    --  value. This provides a limited form of value propagation for variables
  57    --  which are initialized or assigned not been further modified at the time
  58    --  of reference. The call has no effect if the Current_Value refers to a
  59    --  conditional with condition other than equality.
  60
  61    procedure Expand_Discriminant (N : Node_Id);
  62    --  An occurrence of a discriminant within a discriminated type is replaced
  63    --  with the corresponding discriminal, that is to say the formal parameter
  64    --  of the initialization procedure for the type that is associated with
  65    --  that particular discriminant. This replacement is not performed for
  66    --  discriminants of records that appear in constraints of component of the
  67    --  record, because Gigi uses the discriminant name to retrieve its value.
  68    --  In the other hand, it has to be performed for default expressions of
  69    --  components because they are used in the record init procedure. See Einfo
  70    --  for more details, and Exp_Ch3, Exp_Ch9 for examples of use. For
  71    --  discriminants of tasks and protected types, the transformation is more
  72    --  complex when it occurs within a default expression for an entry or
  73    --  protected operation. The corresponding default_expression_function has
  74    --  an additional parameter which is the target of an entry call, and the
  75    --  discriminant of the task must be replaced with a reference to the
  76    --  discriminant of that formal parameter.
  77
  78    procedure Expand_Entity_Reference (N : Node_Id);
  79    --  Common processing for expansion of identifiers and expanded names
  80    --  Dispatches to specific expansion procedures.
  81
  82    procedure Expand_Entry_Index_Parameter (N : Node_Id);
  83    --  A reference to the identifier in the entry index specification of
  84    --  protected entry body is modified to a reference to a constant definition
  85    --  equal to the index of the entry family member being called. This
  86    --  constant is calculated as part of the elaboration of the expanded code
  87    --  for the body, and is calculated from the object-wide entry index
  88    --  returned by Next_Entry_Call.
  89
  90    procedure Expand_Entry_Parameter (N : Node_Id);
  91    --  A reference to an entry parameter is modified to be a reference to the
  92    --  corresponding component of the entry parameter record that is passed by
  93    --  the runtime to the accept body procedure.
  94
  95    procedure Expand_Formal (N : Node_Id);
  96    --  A reference to a formal parameter of a protected subprogram is expanded
  97    --  into the corresponding formal of the unprotected procedure used to
  98    --  represent the operation within the protected object. In other cases
  99    --  Expand_Formal is a no-op.
 100
 101    procedure Expand_Protected_Private (N : Node_Id);
 102    --  A reference to a private component of a protected type is expanded to a
 103    --  component selected from the record used to implement the protected
 104    --  object. Such a record is passed to all operations on a protected object
 105    --  in a parameter named _object. This object is a constant in the body of a
 106    --  function, and a variable within a procedure or entry body.
 107
 108    procedure Expand_Renaming (N : Node_Id);
 109    --  For renamings, just replace the identifier by the corresponding
 110    --  named expression. Note that this has been evaluated (see routine
 111    --  Exp_Ch8.Expand_N_Object_Renaming.Evaluate_Name) so this gives
 112    --  the correct renaming semantics.
 113
 114    --------------------------
 115    -- Expand_Current_Value --
 116    --------------------------
 117
 118    procedure Expand_Current_Value (N : Node_Id) is
 119       Loc : constant Source_Ptr := Sloc (N);
 120       E   : constant Entity_Id  := Entity (N);
 121       CV  : constant Node_Id    := Current_Value (E);
 122       T   : constant Entity_Id  := Etype (N);
 123       Val : Node_Id;
 124       Op  : Node_Kind;
 125
 126    --  Start of processing for Expand_Current_Value
 127
 128    begin
 129       if True
 130
 131          --  No replacement if value raises constraint error
 132
 133          and then Nkind (CV) /= N_Raise_Constraint_Error
 134
 135          --  Do this only for discrete types
 136
 137          and then Is_Discrete_Type (T)
 138
 139          --  Do not replace biased types, since it is problematic to
 140          --  consistently generate a sensible constant value in this case.
 141
 142          and then not Has_Biased_Representation (T)
 143
 144          --  Do not replace lvalues
 145
 146          and then not May_Be_Lvalue (N)
 147
 148          --  Check that entity is suitable for replacement
 149
 150          and then OK_To_Do_Constant_Replacement (E)
 151
 152          --  Do not replace occurrences in pragmas (where names typically
 153          --  appear not as values, but as simply names. If there are cases
 154          --  where values are required, it is only a very minor efficiency
 155          --  issue that they do not get replaced when they could be).
 156
 157          and then Nkind (Parent (N)) /= N_Pragma_Argument_Association
 158
 159          --  Do not replace the prefixes of attribute references, since this
 160          --  causes trouble with cases like 4'Size. Also for Name_Asm_Input and
 161          --  Name_Asm_Output, don't do replacement anywhere, since we can have
 162          --  lvalue references in the arguments.
 163
 164          and then not (Nkind (Parent (N)) = N_Attribute_Reference
 165                          and then
 166                            (Attribute_Name (Parent (N)) = Name_Asm_Input
 167                               or else
 168                             Attribute_Name (Parent (N)) = Name_Asm_Output
 169                               or else
 170                             Prefix (Parent (N)) = N))
 171
 172       then
 173          --  Case of Current_Value is a compile time known value
 174
 175          if Nkind (CV) in N_Subexpr then
 176             Val := CV;
 177
 178          --  Case of Current_Value is a conditional expression reference
 179
 180          else
 181             Get_Current_Value_Condition (N, Op, Val);
 182
 183             if Op /= N_Op_Eq then
 184                return;
 185             end if;
 186          end if;
 187
 188          --  If constant value is an occurrence of an enumeration literal,
 189          --  then we just make another occurence of the same literal.
 190
 191          if Is_Entity_Name (Val)
 192            and then Ekind (Entity (Val)) = E_Enumeration_Literal
 193          then
 194             Rewrite (N,
 195               Unchecked_Convert_To (T,
 196                 New_Occurrence_Of (Entity (Val), Loc)));
 197
 198          --  Otherwise get the value, and convert to appropriate type
 199
 200          else
 201             Rewrite (N,
 202               Unchecked_Convert_To (T,
 203                 Make_Integer_Literal (Loc,
 204                   Intval => Expr_Rep_Value (Val))));
 205          end if;
 206
 207          Analyze_And_Resolve (N, T);
 208          Set_Is_Static_Expression (N, False);
 209       end if;
 210    end Expand_Current_Value;
 211
 212    -------------------------
 213    -- Expand_Discriminant --
 214    -------------------------
 215
 216    procedure Expand_Discriminant (N : Node_Id) is
 217       Scop     : constant Entity_Id := Scope (Entity (N));
 218       P        : Node_Id := N;
 219       Parent_P : Node_Id := Parent (P);
 220       In_Entry : Boolean := False;
 221
 222    begin
 223       --  The Incomplete_Or_Private_Kind happens while resolving the
 224       --  discriminant constraint involved in a derived full type,
 225       --  such as:
 226
 227       --    type D is private;
 228       --    type D(C : ...) is new T(C);
 229
 230       if Ekind (Scop) = E_Record_Type
 231         or Ekind (Scop) in Incomplete_Or_Private_Kind
 232       then
 233          --  Find the origin by walking up the tree till the component
 234          --  declaration
 235
 236          while Present (Parent_P)
 237            and then Nkind (Parent_P) /= N_Component_Declaration
 238          loop
 239             P := Parent_P;
 240             Parent_P := Parent (P);
 241          end loop;
 242
 243          --  If the discriminant reference was part of the default expression
 244          --  it has to be "discriminalized"
 245
 246          if Present (Parent_P) and then P = Expression (Parent_P) then
 247             Set_Entity (N, Discriminal (Entity (N)));
 248          end if;
 249
 250       elsif Is_Concurrent_Type (Scop) then
 251          while Present (Parent_P)
 252            and then Nkind (Parent_P) /= N_Subprogram_Body
 253          loop
 254             P := Parent_P;
 255
 256             if Nkind (P) = N_Entry_Declaration then
 257                In_Entry := True;
 258             end if;
 259
 260             Parent_P := Parent (Parent_P);
 261          end loop;
 262
 263          --  If the discriminant occurs within the default expression for a
 264          --  formal of an entry or protected operation, create a default
 265          --  function for it, and replace the discriminant with a reference to
 266          --  the discriminant of the formal of the default function. The
 267          --  discriminant entity is the one defined in the corresponding
 268          --  record.
 269
 270          if Present (Parent_P)
 271            and then Present (Corresponding_Spec (Parent_P))
 272          then
 273             declare
 274                Loc    : constant Source_Ptr := Sloc (N);
 275                D_Fun  : constant Entity_Id := Corresponding_Spec  (Parent_P);
 276                Formal : constant Entity_Id := First_Formal (D_Fun);
 277                New_N  : Node_Id;
 278                Disc   : Entity_Id;
 279
 280             begin
 281                --  Verify that we are within a default function: the type of
 282                --  its formal parameter is the same task or protected type.
 283
 284                if Present (Formal)
 285                  and then Etype (Formal) = Scope (Entity (N))
 286                then
 287                   Disc := CR_Discriminant (Entity (N));
 288
 289                   New_N :=
 290                     Make_Selected_Component (Loc,
 291                       Prefix => New_Occurrence_Of (Formal, Loc),
 292                       Selector_Name => New_Occurrence_Of (Disc, Loc));
 293
 294                   Set_Etype (New_N, Etype (N));
 295                   Rewrite (N, New_N);
 296
 297                else
 298                   Set_Entity (N, Discriminal (Entity (N)));
 299                end if;
 300             end;
 301
 302          elsif Nkind (Parent (N)) = N_Range
 303            and then In_Entry
 304          then
 305             Set_Entity (N, CR_Discriminant (Entity (N)));
 306          else
 307             Set_Entity (N, Discriminal (Entity (N)));
 308          end if;
 309
 310       else
 311          Set_Entity (N, Discriminal (Entity (N)));
 312       end if;
 313    end Expand_Discriminant;
 314
 315    -----------------------------
 316    -- Expand_Entity_Reference --
 317    -----------------------------
 318
 319    procedure Expand_Entity_Reference (N : Node_Id) is
 320       E : constant Entity_Id := Entity (N);
 321
 322    begin
 323       --  Defend against errors
 324
 325       if No (E) and then Total_Errors_Detected /= 0 then
 326          return;
 327       end if;
 328
 329       if Ekind (E) = E_Discriminant then
 330          Expand_Discriminant (N);
 331
 332       elsif Is_Entry_Formal (E) then
 333          Expand_Entry_Parameter (N);
 334
 335       elsif Ekind (E) = E_Component
 336         and then Is_Protected_Private (E)
 337       then
 338          --  Protect against junk use of tasking in no run time mode
 339
 340          if No_Run_Time_Mode then
 341             return;
 342          end if;
 343
 344          Expand_Protected_Private (N);
 345
 346       elsif Ekind (E) = E_Entry_Index_Parameter then
 347          Expand_Entry_Index_Parameter (N);
 348
 349       elsif Is_Formal (E) then
 350          Expand_Formal (N);
 351
 352       elsif Is_Renaming_Of_Object (E) then
 353          Expand_Renaming (N);
 354
 355       elsif Ekind (E) = E_Variable
 356         and then Is_Shared_Passive (E)
 357       then
 358          Expand_Shared_Passive_Variable (N);
 359       end if;
 360
 361       --  Interpret possible Current_Value for variable case
 362
 363       if (Ekind (E) = E_Variable
 364             or else
 365           Ekind (E) = E_In_Out_Parameter
 366             or else
 367           Ekind (E) = E_Out_Parameter)
 368         and then Present (Current_Value (E))
 369       then
 370          Expand_Current_Value (N);
 371
 372          --  We do want to warn for the case of a boolean variable (not a
 373          --  boolean constant) whose value is known at compile time.
 374
 375          if Is_Boolean_Type (Etype (N)) then
 376             Warn_On_Known_Condition (N);
 377          end if;
 378
 379       --  Don't mess with Current_Value for compile time known values. Not
 380       --  only is it unnecessary, but we could disturb an indication of a
 381       --  static value, which could cause semantic trouble.
 382
 383       elsif Compile_Time_Known_Value (N) then
 384          null;
 385
 386       --  Interpret possible Current_Value for constant case
 387
 388       elsif (Ekind (E) = E_Constant
 389                or else
 390              Ekind (E) = E_In_Parameter
 391                or else
 392              Ekind (E) = E_Loop_Parameter)
 393         and then Present (Current_Value (E))
 394       then
 395          Expand_Current_Value (N);
 396       end if;
 397    end Expand_Entity_Reference;
 398
 399    ----------------------------------
 400    -- Expand_Entry_Index_Parameter --
 401    ----------------------------------
 402
 403    procedure Expand_Entry_Index_Parameter (N : Node_Id) is
 404    begin
 405       Set_Entity (N, Entry_Index_Constant (Entity (N)));
 406    end Expand_Entry_Index_Parameter;
 407
 408    ----------------------------
 409    -- Expand_Entry_Parameter --
 410    ----------------------------
 411
 412    procedure Expand_Entry_Parameter (N : Node_Id) is
 413       Loc        : constant Source_Ptr := Sloc (N);
 414       Ent_Formal : constant Entity_Id  := Entity (N);
 415       Ent_Spec   : constant Entity_Id  := Scope (Ent_Formal);
 416       Parm_Type  : constant Entity_Id  := Entry_Parameters_Type (Ent_Spec);
 417       Acc_Stack  : constant Elist_Id   := Accept_Address (Ent_Spec);
 418       Addr_Ent   : constant Entity_Id  := Node (Last_Elmt (Acc_Stack));
 419       P_Comp_Ref : Entity_Id;
 420
 421       function In_Assignment_Context (N : Node_Id) return Boolean;
 422       --  Check whether this is a context in which the entry formal may be
 423       --  assigned to.
 424
 425       ---------------------------
 426       -- In_Assignment_Context --
 427       ---------------------------
 428
 429       function In_Assignment_Context (N : Node_Id) return Boolean is
 430       begin
 431          --  Case of use in a call
 432
 433          --  ??? passing a formal as actual for a mode IN formal is
 434          --  considered as an assignment?
 435
 436          if Nkind (Parent (N)) = N_Procedure_Call_Statement
 437            or else Nkind (Parent (N)) = N_Entry_Call_Statement
 438            or else
 439              (Nkind (Parent (N)) = N_Assignment_Statement
 440                  and then N = Name (Parent (N)))
 441          then
 442             return True;
 443
 444          --  Case of a parameter association: climb up to enclosing call
 445
 446          elsif Nkind (Parent (N)) = N_Parameter_Association then
 447             return In_Assignment_Context (Parent (N));
 448
 449          --  Case of a selected component, indexed component or slice prefix:
 450          --  climb up the tree, unless the prefix is of an access type (in
 451          --  which case there is an implicit dereference, and the formal itself
 452          --  is not being assigned to).
 453
 454          elsif (Nkind (Parent (N)) = N_Selected_Component
 455                  or else Nkind (Parent (N)) = N_Indexed_Component
 456                  or else Nkind (Parent (N)) = N_Slice)
 457            and then N = Prefix (Parent (N))
 458            and then not Is_Access_Type (Etype (N))
 459            and then In_Assignment_Context (Parent (N))
 460          then
 461             return True;
 462
 463          else
 464             return False;
 465          end if;
 466       end In_Assignment_Context;
 467
 468    --  Start of processing for Expand_Entry_Parameter
 469
 470    begin
 471       if Is_Task_Type (Scope (Ent_Spec))
 472         and then Comes_From_Source (Ent_Formal)
 473       then
 474          --  Before replacing the formal with the local renaming that is used
 475          --  in the accept block, note if this is an assignment context, and
 476          --  note the modification to avoid spurious warnings, because the
 477          --  original entity is not used further. If formal is unconstrained,
 478          --  we also generate an extra parameter to hold the Constrained
 479          --  attribute of the actual. No renaming is generated for this flag.
 480
 481          if Ekind (Entity (N)) /= E_In_Parameter
 482            and then In_Assignment_Context (N)
 483          then
 484             Note_Possible_Modification (N);
 485          end if;
 486
 487          Rewrite (N, New_Occurrence_Of (Renamed_Object (Entity (N)), Loc));
 488          return;
 489       end if;
 490
 491       --  What we need is a reference to the corresponding component of the
 492       --  parameter record object. The Accept_Address field of the entry entity
 493       --  references the address variable that contains the address of the
 494       --  accept parameters record. We first have to do an unchecked conversion
 495       --  to turn this into a pointer to the parameter record and then we
 496       --  select the required parameter field.
 497
 498       P_Comp_Ref :=
 499         Make_Selected_Component (Loc,
 500           Prefix =>
 501             Make_Explicit_Dereference (Loc,
 502               Unchecked_Convert_To (Parm_Type,
 503                 New_Reference_To (Addr_Ent, Loc))),
 504           Selector_Name =>
 505             New_Reference_To (Entry_Component (Ent_Formal), Loc));
 506
 507       --  For all types of parameters, the constructed parameter record object
 508       --  contains a pointer to the parameter. Thus we must dereference them to
 509       --  access them (this will often be redundant, since the needed deference
 510       --  is implicit, but no harm is done by making it explicit).
 511
 512       Rewrite (N,
 513         Make_Explicit_Dereference (Loc, P_Comp_Ref));
 514
 515       Analyze (N);
 516    end Expand_Entry_Parameter;
 517
 518    -------------------
 519    -- Expand_Formal --
 520    -------------------
 521
 522    procedure Expand_Formal (N : Node_Id) is
 523       E    : constant Entity_Id  := Entity (N);
 524       Scop : constant Entity_Id  := Scope (E);
 525
 526    begin
 527       --  Check whether the subprogram of which this is a formal is
 528       --  a protected operation. The initialization procedure for
 529       --  the corresponding record type is not itself a protected operation.
 530
 531       if Is_Protected_Type (Scope (Scop))
 532         and then not Is_Init_Proc (Scop)
 533         and then Present (Protected_Formal (E))
 534       then
 535          Set_Entity (N, Protected_Formal (E));
 536       end if;
 537    end Expand_Formal;
 538
 539    ----------------------------
 540    -- Expand_N_Expanded_Name --
 541    ----------------------------
 542
 543    procedure Expand_N_Expanded_Name (N : Node_Id) is
 544    begin
 545       Expand_Entity_Reference (N);
 546    end Expand_N_Expanded_Name;
 547
 548    -------------------------
 549    -- Expand_N_Identifier --
 550    -------------------------
 551
 552    procedure Expand_N_Identifier (N : Node_Id) is
 553    begin
 554       Expand_Entity_Reference (N);
 555    end Expand_N_Identifier;
 556
 557    ---------------------------
 558    -- Expand_N_Real_Literal --
 559    ---------------------------
 560
 561    procedure Expand_N_Real_Literal (N : Node_Id) is
 562    begin
 563       if Vax_Float (Etype (N)) then
 564          Expand_Vax_Real_Literal (N);
 565       end if;
 566    end Expand_N_Real_Literal;
 567
 568    ------------------------------
 569    -- Expand_Protected_Private --
 570    ------------------------------
 571
 572    procedure Expand_Protected_Private (N : Node_Id) is
 573       Loc      : constant Source_Ptr := Sloc (N);
 574       E        : constant Entity_Id  := Entity (N);
 575       Op       : constant Node_Id    := Protected_Operation (E);
 576       Scop     : Entity_Id;
 577       Lo       : Node_Id;
 578       Hi       : Node_Id;
 579       D_Range  : Node_Id;
 580
 581    begin
 582       if Nkind (Op) /= N_Subprogram_Body
 583         or else Nkind (Specification (Op)) /= N_Function_Specification
 584       then
 585          Set_Ekind (Prival (E), E_Variable);
 586       else
 587          Set_Ekind (Prival (E), E_Constant);
 588       end if;
 589
 590       --  If the private component appears in an assignment (either lhs or
 591       --  rhs) and is a one-dimensional array constrained by a discriminant,
 592       --  rewrite as  P (Lo .. Hi) with an explicit range, so that discriminal
 593       --  is directly visible. This solves delicate visibility problems.
 594
 595       if Comes_From_Source (N)
 596         and then Is_Array_Type (Etype (E))
 597         and then Number_Dimensions (Etype (E)) = 1
 598         and then not Within_Init_Proc
 599       then
 600          Lo := Type_Low_Bound  (Etype (First_Index (Etype (E))));
 601          Hi := Type_High_Bound (Etype (First_Index (Etype (E))));
 602
 603          if Nkind (Parent (N)) = N_Assignment_Statement
 604            and then ((Is_Entity_Name (Lo)
 605                           and then Ekind (Entity (Lo)) = E_In_Parameter)
 606                        or else (Is_Entity_Name (Hi)
 607                                   and then
 608                                     Ekind (Entity (Hi)) = E_In_Parameter))
 609          then
 610             D_Range := New_Node (N_Range, Loc);
 611
 612             if Is_Entity_Name (Lo)
 613               and then Ekind (Entity (Lo)) = E_In_Parameter
 614             then
 615                Set_Low_Bound (D_Range,
 616                  Make_Identifier (Loc, Chars (Entity (Lo))));
 617             else
 618                Set_Low_Bound (D_Range, Duplicate_Subexpr (Lo));
 619             end if;
 620
 621             if Is_Entity_Name (Hi)
 622               and then Ekind (Entity (Hi)) = E_In_Parameter
 623             then
 624                Set_High_Bound (D_Range,
 625                  Make_Identifier (Loc, Chars (Entity (Hi))));
 626             else
 627                Set_High_Bound (D_Range, Duplicate_Subexpr (Hi));
 628             end if;
 629
 630             Rewrite (N,
 631               Make_Slice (Loc,
 632                 Prefix => New_Occurrence_Of (E, Loc),
 633                 Discrete_Range => D_Range));
 634
 635             Analyze_And_Resolve (N, Etype (E));
 636             return;
 637          end if;
 638       end if;
 639
 640       --  The type of the reference is the type of the prival, which may differ
 641       --  from that of the original component if it is an itype.
 642
 643       Set_Entity (N, Prival (E));
 644       Set_Etype  (N, Etype (Prival (E)));
 645       Scop := Current_Scope;
 646
 647       --  Find entity for protected operation, which must be on scope stack
 648
 649       while not Is_Protected_Type (Scope (Scop)) loop
 650          Scop := Scope (Scop);
 651       end loop;
 652
 653       Append_Elmt (N, Privals_Chain (Scop));
 654    end Expand_Protected_Private;
 655
 656    ---------------------
 657    -- Expand_Renaming --
 658    ---------------------
 659
 660    procedure Expand_Renaming (N : Node_Id) is
 661       E : constant Entity_Id := Entity (N);
 662       T : constant Entity_Id := Etype (N);
 663
 664    begin
 665       Rewrite (N, New_Copy_Tree (Renamed_Object (E)));
 666
 667       --  We mark the copy as unanalyzed, so that it is sure to be reanalyzed
 668       --  at the top level. This is needed in the packed case since we
 669       --  specifically avoided expanding packed array references when the
 670       --  renaming declaration was analyzed.
 671
 672       Reset_Analyzed_Flags (N);
 673       Analyze_And_Resolve (N, T);
 674    end Expand_Renaming;
 675
 676    ------------------
 677    -- Param_Entity --
 678    ------------------
 679
 680    --  This would be trivial, simply a test for an identifier that was a
 681    --  reference to a formal, if it were not for the fact that a previous call
 682    --  to Expand_Entry_Parameter will have modified the reference to the
 683    --  identifier. A formal of a protected entity is rewritten as
 684
 685    --    typ!(recobj).rec.all'Constrained
 686
 687    --  where rec is a selector whose Entry_Formal link points to the formal
 688    --  For a formal of a task entity, the formal is rewritten as a local
 689    --  renaming.
 690
 691    --  In addition, a formal that is marked volatile because it is aliased
 692    --  through an address clause is rewritten as dereference as well.
 693
 694    function Param_Entity (N : Node_Id) return Entity_Id is
 695       Renamed_Obj : Node_Id;
 696
 697    begin
 698       --  Simple reference case
 699
 700       if Nkind (N) = N_Identifier or else Nkind (N) = N_Expanded_Name then
 701          if Is_Formal (Entity (N)) then
 702             return Entity (N);
 703
 704          --  Handle renamings of formal parameters and formals of tasks that
 705          --  are rewritten as renamings.
 706
 707          elsif Nkind (Parent (Entity (N))) = N_Object_Renaming_Declaration then
 708             Renamed_Obj := Get_Referenced_Object (Renamed_Object (Entity (N)));
 709
 710             if Is_Entity_Name (Renamed_Obj)
 711               and then Is_Formal (Entity (Renamed_Obj))
 712             then
 713                return Entity (Renamed_Obj);
 714
 715             elsif
 716               Nkind (Parent (Parent (Entity (N)))) = N_Accept_Statement
 717             then
 718                return Entity (N);
 719             end if;
 720          end if;
 721
 722       else
 723          if Nkind (N) = N_Explicit_Dereference then
 724             declare
 725                P : constant Node_Id := Prefix (N);
 726                S : Node_Id;
 727
 728             begin
 729                if Nkind (P) = N_Selected_Component then
 730                   S := Selector_Name (P);
 731
 732                   if Present (Entry_Formal (Entity (S))) then
 733                      return Entry_Formal (Entity (S));
 734                   end if;
 735
 736                elsif Nkind (Original_Node (N)) = N_Identifier then
 737                   return Param_Entity (Original_Node (N));
 738                end if;
 739             end;
 740          end if;
 741       end if;
 742
 743       return (Empty);
 744    end Param_Entity;
 745
 746 end Exp_Ch2;