1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2005 Free Software Foundation, Inc. --
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 2, 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 COPYING. If not, write --
19 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
20 -- MA 02111-1307, USA. --
22 -- GNAT was originally developed by the GNAT team at New York University. --
23 -- Extensive contributions were provided by Ada Core Technologies Inc. --
25 ------------------------------------------------------------------------------
27 with Atree; use Atree;
28 with Debug; use Debug;
29 with Einfo; use Einfo;
30 with Elists; use Elists;
31 with Errout; use Errout;
32 with Exp_Smem; use Exp_Smem;
33 with Exp_Tss; use Exp_Tss;
34 with Exp_Util; use Exp_Util;
35 with Exp_VFpt; use Exp_VFpt;
36 with Nmake; use Nmake;
39 with Sem_Eval; use Sem_Eval;
40 with Sem_Res; use Sem_Res;
41 with Sem_Util; use Sem_Util;
42 with Sem_Warn; use Sem_Warn;
43 with Sinfo; use Sinfo;
44 with Snames; use Snames;
45 with Stand; use Stand;
46 with Tbuild; use Tbuild;
47 with Uintp; use Uintp;
49 package body Exp_Ch2 is
51 -----------------------
52 -- Local Subprograms --
53 -----------------------
55 procedure Expand_Current_Value (N : Node_Id);
56 -- Given a node N for a variable whose Current_Value field is set.
57 -- If the node is for a discrete type, replaces the node with a
58 -- copy of the referenced value. This provides a limited form of
59 -- value propagation for variables which are initialized or assigned
60 -- not been further modified at the time of reference. The call has
61 -- no effect if the Current_Value refers to a conditional with a
62 -- condition other than equality.
64 procedure Expand_Discriminant (N : Node_Id);
65 -- An occurrence of a discriminant within a discriminated type is replaced
66 -- with the corresponding discriminal, that is to say the formal parameter
67 -- of the initialization procedure for the type that is associated with
68 -- that particular discriminant. This replacement is not performed for
69 -- discriminants of records that appear in constraints of component of the
70 -- record, because Gigi uses the discriminant name to retrieve its value.
71 -- In the other hand, it has to be performed for default expressions of
72 -- components because they are used in the record init procedure. See
73 -- Einfo for more details, and Exp_Ch3, Exp_Ch9 for examples of use.
74 -- For discriminants of tasks and protected types, the transformation is
75 -- more complex when it occurs within a default expression for an entry
76 -- or protected operation. The corresponding default_expression_function
77 -- has an additional parameter which is the target of an entry call, and
78 -- the discriminant of the task must be replaced with a reference to the
79 -- discriminant of that formal parameter.
81 procedure Expand_Entity_Reference (N : Node_Id);
82 -- Common processing for expansion of identifiers and expanded names
84 procedure Expand_Entry_Index_Parameter (N : Node_Id);
85 -- A reference to the identifier in the entry index specification
86 -- of a protected entry body is modified to a reference to a constant
87 -- definintion equal to the index of the entry family member being
88 -- called. This constant is calculated as part of the elaboration
89 -- of the expanded code for the body, and is calculated from the
90 -- object-wide entry index returned by Next_Entry_Call.
92 procedure Expand_Entry_Parameter (N : Node_Id);
93 -- A reference to an entry parameter is modified to be a reference to
94 -- the corresponding component of the entry parameter record that is
95 -- passed by the runtime to the accept body procedure
97 procedure Expand_Formal (N : Node_Id);
98 -- A reference to a formal parameter of a protected subprogram is
99 -- expanded to the corresponding formal of the unprotected procedure
100 -- used to represent the protected subprogram within the protected object.
102 procedure Expand_Protected_Private (N : Node_Id);
103 -- A reference to a private object of a protected type is expanded
104 -- to a component selected from the record used to implement
105 -- the protected object. Such a record is passed to all operations
106 -- on a protected object in a parameter named _object. Such an object
107 -- is a constant within a function, and a variable otherwise.
109 procedure Expand_Renaming (N : Node_Id);
110 -- For renamings, just replace the identifier by the corresponding
111 -- name expression. Note that this has been evaluated (see routine
112 -- Exp_Ch8.Expand_N_Object_Renaming.Evaluate_Name) so this gives
113 -- the correct renaming semantics.
115 --------------------------
116 -- Expand_Current_Value --
117 --------------------------
119 procedure Expand_Current_Value (N : Node_Id) is
120 Loc : constant Source_Ptr := Sloc (N);
121 E : constant Entity_Id := Entity (N);
122 CV : constant Node_Id := Current_Value (E);
123 T : constant Entity_Id := Etype (N);
127 function In_Appropriate_Scope return Boolean;
128 -- Returns true if the current scope is the scope of E, or is a nested
129 -- (to any level) package declaration, package body, or block of this
130 -- scope. The idea is that such references are in the sequential
131 -- execution sequence of statements executed after E is elaborated.
133 --------------------------
134 -- In_Appropriate_Scope --
135 --------------------------
137 function In_Appropriate_Scope return Boolean is
138 ES : constant Entity_Id := Scope (E);
145 -- If we are in right scope, replacement is safe
150 -- Packages do not affect the determination of safety
152 elsif Ekind (CS) = E_Package then
154 exit when CS = Standard_Standard;
156 -- Blocks do not affect the determination of safety
158 elsif Ekind (CS) = E_Block then
161 -- Otherwise, the reference is dubious, and we cannot be
162 -- sure that it is safe to do the replacement.
170 end In_Appropriate_Scope;
172 -- Start of processing for Expand_Current_Value
177 -- No replacement if value raises constraint error
179 and then Nkind (CV) /= N_Raise_Constraint_Error
181 -- Do this only for discrete types
183 and then Is_Discrete_Type (T)
185 -- Do not replace biased types, since it is problematic to
186 -- consistently generate a sensible constant value in this case.
188 and then not Has_Biased_Representation (T)
190 -- Do not replace lvalues
192 and then not Is_Lvalue (N)
194 -- Do not replace occurrences that are not in the current scope,
195 -- because in a nested subprogram we know absolutely nothing about
196 -- the sequence of execution.
198 and then In_Appropriate_Scope
200 -- Do not replace statically allocated objects, because they may
201 -- be modified outside the current scope.
203 and then not Is_Statically_Allocated (E)
205 -- Do not replace aliased or volatile objects, since we don't know
206 -- what else might change the value
208 and then not Is_Aliased (E) and then not Treat_As_Volatile (E)
210 -- Debug flag -gnatdM disconnects this optimization
212 and then not Debug_Flag_MM
214 -- Do not replace occurrences in pragmas (where names typically
215 -- appear not as values, but as simply names. If there are cases
216 -- where values are required, it is only a very minor efficiency
217 -- issue that they do not get replaced when they could be).
219 and then Nkind (Parent (N)) /= N_Pragma_Argument_Association
221 -- Same for Asm_Input and Asm_Output attribute references
223 and then not (Nkind (Parent (N)) = N_Attribute_Reference
225 (Attribute_Name (Parent (N)) = Name_Asm_Input
227 Attribute_Name (Parent (N)) = Name_Asm_Output))
229 -- Case of Current_Value is a compile time known value
231 if Nkind (CV) in N_Subexpr then
234 -- Case of Current_Value is a conditional expression reference
237 Get_Current_Value_Condition (N, Op, Val);
239 if Op /= N_Op_Eq then
244 -- If constant value is an occurrence of an enumeration literal,
245 -- then we just make another occurence of the same literal.
247 if Is_Entity_Name (Val)
248 and then Ekind (Entity (Val)) = E_Enumeration_Literal
251 Unchecked_Convert_To (T,
252 New_Occurrence_Of (Entity (Val), Loc)));
254 -- Otherwise get the value, and convert to appropriate type
258 Unchecked_Convert_To (T,
259 Make_Integer_Literal (Loc,
260 Intval => Expr_Rep_Value (Val))));
263 Analyze_And_Resolve (N, T);
264 Set_Is_Static_Expression (N, False);
266 end Expand_Current_Value;
268 -------------------------
269 -- Expand_Discriminant --
270 -------------------------
272 procedure Expand_Discriminant (N : Node_Id) is
273 Scop : constant Entity_Id := Scope (Entity (N));
275 Parent_P : Node_Id := Parent (P);
276 In_Entry : Boolean := False;
279 -- The Incomplete_Or_Private_Kind happens while resolving the
280 -- discriminant constraint involved in a derived full type,
283 -- type D is private;
284 -- type D(C : ...) is new T(C);
286 if Ekind (Scop) = E_Record_Type
287 or Ekind (Scop) in Incomplete_Or_Private_Kind
289 -- Find the origin by walking up the tree till the component
292 while Present (Parent_P)
293 and then Nkind (Parent_P) /= N_Component_Declaration
296 Parent_P := Parent (P);
299 -- If the discriminant reference was part of the default expression
300 -- it has to be "discriminalized"
302 if Present (Parent_P) and then P = Expression (Parent_P) then
303 Set_Entity (N, Discriminal (Entity (N)));
306 elsif Is_Concurrent_Type (Scop) then
307 while Present (Parent_P)
308 and then Nkind (Parent_P) /= N_Subprogram_Body
312 if Nkind (P) = N_Entry_Declaration then
316 Parent_P := Parent (Parent_P);
319 -- If the discriminant occurs within the default expression for
320 -- a formal of an entry or protected operation, create a default
321 -- function for it, and replace the discriminant with a reference
322 -- to the discriminant of the formal of the default function.
323 -- The discriminant entity is the one defined in the corresponding
326 if Present (Parent_P)
327 and then Present (Corresponding_Spec (Parent_P))
330 Loc : constant Source_Ptr := Sloc (N);
331 D_Fun : constant Entity_Id := Corresponding_Spec (Parent_P);
332 Formal : constant Entity_Id := First_Formal (D_Fun);
337 -- Verify that we are within a default function: the type of
338 -- its formal parameter is the same task or protected type.
341 and then Etype (Formal) = Scope (Entity (N))
343 Disc := CR_Discriminant (Entity (N));
346 Make_Selected_Component (Loc,
347 Prefix => New_Occurrence_Of (Formal, Loc),
348 Selector_Name => New_Occurrence_Of (Disc, Loc));
350 Set_Etype (New_N, Etype (N));
354 Set_Entity (N, Discriminal (Entity (N)));
358 elsif Nkind (Parent (N)) = N_Range
361 Set_Entity (N, CR_Discriminant (Entity (N)));
363 Set_Entity (N, Discriminal (Entity (N)));
367 Set_Entity (N, Discriminal (Entity (N)));
369 end Expand_Discriminant;
371 -----------------------------
372 -- Expand_Entity_Reference --
373 -----------------------------
375 procedure Expand_Entity_Reference (N : Node_Id) is
376 E : constant Entity_Id := Entity (N);
379 -- Defend against errors
381 if No (E) and then Total_Errors_Detected /= 0 then
385 if Ekind (E) = E_Discriminant then
386 Expand_Discriminant (N);
388 elsif Is_Entry_Formal (E) then
389 Expand_Entry_Parameter (N);
391 elsif Ekind (E) = E_Component
392 and then Is_Protected_Private (E)
394 -- Protect against junk use of tasking in no run time mode
396 if No_Run_Time_Mode then
400 Expand_Protected_Private (N);
402 elsif Ekind (E) = E_Entry_Index_Parameter then
403 Expand_Entry_Index_Parameter (N);
405 elsif Is_Formal (E) then
408 elsif Is_Renaming_Of_Object (E) then
411 elsif Ekind (E) = E_Variable
412 and then Is_Shared_Passive (E)
414 Expand_Shared_Passive_Variable (N);
416 elsif (Ekind (E) = E_Variable
418 Ekind (E) = E_In_Out_Parameter
420 Ekind (E) = E_Out_Parameter)
421 and then Present (Current_Value (E))
423 Expand_Current_Value (N);
425 -- We do want to warn for the case of a boolean variable (not
426 -- a boolean constant) whose value is known at compile time.
428 if Is_Boolean_Type (Etype (N)) then
429 Warn_On_Known_Condition (N);
432 end Expand_Entity_Reference;
434 ----------------------------------
435 -- Expand_Entry_Index_Parameter --
436 ----------------------------------
438 procedure Expand_Entry_Index_Parameter (N : Node_Id) is
440 Set_Entity (N, Entry_Index_Constant (Entity (N)));
441 end Expand_Entry_Index_Parameter;
443 ----------------------------
444 -- Expand_Entry_Parameter --
445 ----------------------------
447 procedure Expand_Entry_Parameter (N : Node_Id) is
448 Loc : constant Source_Ptr := Sloc (N);
449 Ent_Formal : constant Entity_Id := Entity (N);
450 Ent_Spec : constant Entity_Id := Scope (Ent_Formal);
451 Parm_Type : constant Entity_Id := Entry_Parameters_Type (Ent_Spec);
452 Acc_Stack : constant Elist_Id := Accept_Address (Ent_Spec);
453 Addr_Ent : constant Entity_Id := Node (Last_Elmt (Acc_Stack));
454 P_Comp_Ref : Entity_Id;
456 function In_Assignment_Context (N : Node_Id) return Boolean;
457 -- Check whether this is a context in which the entry formal may
460 ---------------------------
461 -- In_Assignment_Context --
462 ---------------------------
464 function In_Assignment_Context (N : Node_Id) return Boolean is
466 if Nkind (Parent (N)) = N_Procedure_Call_Statement
467 or else Nkind (Parent (N)) = N_Entry_Call_Statement
469 (Nkind (Parent (N)) = N_Assignment_Statement
470 and then N = Name (Parent (N)))
474 elsif Nkind (Parent (N)) = N_Parameter_Association then
475 return In_Assignment_Context (Parent (N));
477 elsif (Nkind (Parent (N)) = N_Selected_Component
478 or else Nkind (Parent (N)) = N_Indexed_Component
479 or else Nkind (Parent (N)) = N_Slice)
480 and then In_Assignment_Context (Parent (N))
486 end In_Assignment_Context;
488 -- Start of processing for Expand_Entry_Parameter
491 if Is_Task_Type (Scope (Ent_Spec))
492 and then Comes_From_Source (Ent_Formal)
494 -- Before replacing the formal with the local renaming that is
495 -- used in the accept block, note if this is an assignment
496 -- context, and note the modification to avoid spurious warnings,
497 -- because the original entity is not used further.
498 -- If the formal is unconstrained, we also generate an extra
499 -- parameter to hold the Constrained attribute of the actual. No
500 -- renaming is generated for this flag.
502 if Ekind (Entity (N)) /= E_In_Parameter
503 and then In_Assignment_Context (N)
505 Note_Possible_Modification (N);
508 Rewrite (N, New_Occurrence_Of (Renamed_Object (Entity (N)), Loc));
512 -- What we need is a reference to the corresponding component of the
513 -- parameter record object. The Accept_Address field of the entry
514 -- entity references the address variable that contains the address
515 -- of the accept parameters record. We first have to do an unchecked
516 -- conversion to turn this into a pointer to the parameter record and
517 -- then we select the required parameter field.
520 Make_Selected_Component (Loc,
522 Make_Explicit_Dereference (Loc,
523 Unchecked_Convert_To (Parm_Type,
524 New_Reference_To (Addr_Ent, Loc))),
526 New_Reference_To (Entry_Component (Ent_Formal), Loc));
528 -- For all types of parameters, the constructed parameter record
529 -- object contains a pointer to the parameter. Thus we must
530 -- dereference them to access them (this will often be redundant,
531 -- since the needed deference is implicit, but no harm is done by
532 -- making it explicit).
535 Make_Explicit_Dereference (Loc, P_Comp_Ref));
538 end Expand_Entry_Parameter;
544 procedure Expand_Formal (N : Node_Id) is
545 E : constant Entity_Id := Entity (N);
546 Subp : constant Entity_Id := Scope (E);
549 if Is_Protected_Type (Scope (Subp))
550 and then not Is_Init_Proc (Subp)
551 and then Present (Protected_Formal (E))
553 Set_Entity (N, Protected_Formal (E));
557 ----------------------------
558 -- Expand_N_Expanded_Name --
559 ----------------------------
561 procedure Expand_N_Expanded_Name (N : Node_Id) is
563 Expand_Entity_Reference (N);
564 end Expand_N_Expanded_Name;
566 -------------------------
567 -- Expand_N_Identifier --
568 -------------------------
570 procedure Expand_N_Identifier (N : Node_Id) is
572 Expand_Entity_Reference (N);
573 end Expand_N_Identifier;
575 ---------------------------
576 -- Expand_N_Real_Literal --
577 ---------------------------
579 procedure Expand_N_Real_Literal (N : Node_Id) is
581 if Vax_Float (Etype (N)) then
582 Expand_Vax_Real_Literal (N);
584 end Expand_N_Real_Literal;
586 ------------------------------
587 -- Expand_Protected_Private --
588 ------------------------------
590 procedure Expand_Protected_Private (N : Node_Id) is
591 Loc : constant Source_Ptr := Sloc (N);
592 E : constant Entity_Id := Entity (N);
593 Op : constant Node_Id := Protected_Operation (E);
600 if Nkind (Op) /= N_Subprogram_Body
601 or else Nkind (Specification (Op)) /= N_Function_Specification
603 Set_Ekind (Prival (E), E_Variable);
605 Set_Ekind (Prival (E), E_Constant);
608 -- If the private component appears in an assignment (either lhs or
609 -- rhs) and is a one-dimensional array constrained by a discriminant,
610 -- rewrite as P (Lo .. Hi) with an explicit range, so that discriminal
611 -- is directly visible. This solves delicate visibility problems.
613 if Comes_From_Source (N)
614 and then Is_Array_Type (Etype (E))
615 and then Number_Dimensions (Etype (E)) = 1
616 and then not Within_Init_Proc
618 Lo := Type_Low_Bound (Etype (First_Index (Etype (E))));
619 Hi := Type_High_Bound (Etype (First_Index (Etype (E))));
621 if Nkind (Parent (N)) = N_Assignment_Statement
622 and then ((Is_Entity_Name (Lo)
623 and then Ekind (Entity (Lo)) = E_In_Parameter)
624 or else (Is_Entity_Name (Hi)
626 Ekind (Entity (Hi)) = E_In_Parameter))
628 D_Range := New_Node (N_Range, Loc);
630 if Is_Entity_Name (Lo)
631 and then Ekind (Entity (Lo)) = E_In_Parameter
633 Set_Low_Bound (D_Range,
634 Make_Identifier (Loc, Chars (Entity (Lo))));
636 Set_Low_Bound (D_Range, Duplicate_Subexpr (Lo));
639 if Is_Entity_Name (Hi)
640 and then Ekind (Entity (Hi)) = E_In_Parameter
642 Set_High_Bound (D_Range,
643 Make_Identifier (Loc, Chars (Entity (Hi))));
645 Set_High_Bound (D_Range, Duplicate_Subexpr (Hi));
650 Prefix => New_Occurrence_Of (E, Loc),
651 Discrete_Range => D_Range));
653 Analyze_And_Resolve (N, Etype (E));
658 -- The type of the reference is the type of the prival, which may
659 -- differ from that of the original component if it is an itype.
661 Set_Entity (N, Prival (E));
662 Set_Etype (N, Etype (Prival (E)));
663 Scop := Current_Scope;
665 -- Find entity for protected operation, which must be on scope stack
667 while not Is_Protected_Type (Scope (Scop)) loop
668 Scop := Scope (Scop);
671 Append_Elmt (N, Privals_Chain (Scop));
672 end Expand_Protected_Private;
674 ---------------------
675 -- Expand_Renaming --
676 ---------------------
678 procedure Expand_Renaming (N : Node_Id) is
679 E : constant Entity_Id := Entity (N);
680 T : constant Entity_Id := Etype (N);
683 Rewrite (N, New_Copy_Tree (Renamed_Object (E)));
685 -- We mark the copy as unanalyzed, so that it is sure to be
686 -- reanalyzed at the top level. This is needed in the packed
687 -- case since we specifically avoided expanding packed array
688 -- references when the renaming declaration was analyzed.
690 Reset_Analyzed_Flags (N);
691 Analyze_And_Resolve (N, T);
698 -- This would be trivial, simply a test for an identifier that was a
699 -- reference to a formal, if it were not for the fact that a previous
700 -- call to Expand_Entry_Parameter will have modified the reference
701 -- to the identifier. A formal of a protected entity is rewritten as
703 -- typ!(recobj).rec.all'Constrained
705 -- where rec is a selector whose Entry_Formal link points to the formal
706 -- For a formal of a task entity, the formal is rewritten as a local
709 -- In addition, a formal that is marked volatile because it is aliased
710 -- through an address clause is rewritten as dereference as well.
712 function Param_Entity (N : Node_Id) return Entity_Id is
714 -- Simple reference case
716 if Nkind (N) = N_Identifier then
717 if Is_Formal (Entity (N)) then
720 elsif Nkind (Parent (Entity (N))) = N_Object_Renaming_Declaration
721 and then Nkind (Parent (Parent (Entity (N)))) = N_Accept_Statement
727 if Nkind (N) = N_Explicit_Dereference then
729 P : constant Node_Id := Prefix (N);
733 if Nkind (P) = N_Selected_Component then
734 S := Selector_Name (P);
736 if Present (Entry_Formal (Entity (S))) then
737 return Entry_Formal (Entity (S));
740 elsif Nkind (Original_Node (N)) = N_Identifier then
741 return Param_Entity (Original_Node (N));