1 -----------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
10 -- Copyright (C) 1992-2002, Free Software Foundation, Inc. --
12 -- GNAT is free software; you can redistribute it and/or modify it under --
13 -- terms of the GNU General Public License as published by the Free Soft- --
14 -- ware Foundation; either version 2, or (at your option) any later ver- --
15 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
16 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
17 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
18 -- for more details. You should have received a copy of the GNU General --
19 -- Public License distributed with GNAT; see file COPYING. If not, write --
20 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
21 -- MA 02111-1307, USA. --
23 -- GNAT was originally developed by the GNAT team at New York University. --
24 -- Extensive contributions were provided by Ada Core Technologies Inc. --
26 ------------------------------------------------------------------------------
28 with Atree; use Atree;
29 with Checks; use Checks;
30 with Einfo; use Einfo;
31 with Exp_Aggr; use Exp_Aggr;
32 with Exp_Ch7; use Exp_Ch7;
33 with Exp_Ch11; use Exp_Ch11;
34 with Exp_Dbug; use Exp_Dbug;
35 with Exp_Pakd; use Exp_Pakd;
36 with Exp_Util; use Exp_Util;
37 with Hostparm; use Hostparm;
38 with Nlists; use Nlists;
39 with Nmake; use Nmake;
41 with Restrict; use Restrict;
42 with Rtsfind; use Rtsfind;
43 with Sinfo; use Sinfo;
45 with Sem_Ch8; use Sem_Ch8;
46 with Sem_Ch13; use Sem_Ch13;
47 with Sem_Eval; use Sem_Eval;
48 with Sem_Res; use Sem_Res;
49 with Sem_Util; use Sem_Util;
50 with Snames; use Snames;
51 with Stand; use Stand;
52 with Tbuild; use Tbuild;
53 with Ttypes; use Ttypes;
54 with Uintp; use Uintp;
55 with Validsw; use Validsw;
57 package body Exp_Ch5 is
59 function Change_Of_Representation (N : Node_Id) return Boolean;
60 -- Determine if the right hand side of the assignment N is a type
61 -- conversion which requires a change of representation. Called
62 -- only for the array and record cases.
64 procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id);
65 -- N is an assignment which assigns an array value. This routine process
66 -- the various special cases and checks required for such assignments,
67 -- including change of representation. Rhs is normally simply the right
68 -- hand side of the assignment, except that if the right hand side is
69 -- a type conversion or a qualified expression, then the Rhs is the
70 -- actual expression inside any such type conversions or qualifications.
72 function Expand_Assign_Array_Loop
81 -- N is an assignment statement which assigns an array value. This routine
82 -- expands the assignment into a loop (or nested loops for the case of a
83 -- multi-dimensional array) to do the assignment component by component.
84 -- Larray and Rarray are the entities of the actual arrays on the left
85 -- hand and right hand sides. L_Type and R_Type are the types of these
86 -- arrays (which may not be the same, due to either sliding, or to a
87 -- change of representation case). Ndim is the number of dimensions and
88 -- the parameter Rev indicates if the loops run normally (Rev = False),
89 -- or reversed (Rev = True). The value returned is the constructed
90 -- loop statement. Auxiliary declarations are inserted before node N
91 -- using the standard Insert_Actions mechanism.
93 procedure Expand_Assign_Record (N : Node_Id);
94 -- N is an assignment of a non-tagged record value. This routine handles
95 -- the special cases and checks required for such assignments, including
96 -- change of representation.
98 function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id;
99 -- Generate the necessary code for controlled and Tagged assignment,
100 -- that is to say, finalization of the target before, adjustement of
101 -- the target after and save and restore of the tag and finalization
102 -- pointers which are not 'part of the value' and must not be changed
103 -- upon assignment. N is the original Assignment node.
105 ------------------------------
106 -- Change_Of_Representation --
107 ------------------------------
109 function Change_Of_Representation (N : Node_Id) return Boolean is
110 Rhs : constant Node_Id := Expression (N);
114 Nkind (Rhs) = N_Type_Conversion
116 not Same_Representation (Etype (Rhs), Etype (Expression (Rhs)));
117 end Change_Of_Representation;
119 -------------------------
120 -- Expand_Assign_Array --
121 -------------------------
123 -- There are two issues here. First, do we let Gigi do a block move, or
124 -- do we expand out into a loop? Second, we need to set the two flags
125 -- Forwards_OK and Backwards_OK which show whether the block move (or
126 -- corresponding loops) can be legitimately done in a forwards (low to
127 -- high) or backwards (high to low) manner.
129 procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id) is
130 Loc : constant Source_Ptr := Sloc (N);
132 Lhs : constant Node_Id := Name (N);
134 Act_Lhs : constant Node_Id := Get_Referenced_Object (Lhs);
135 Act_Rhs : Node_Id := Get_Referenced_Object (Rhs);
137 L_Type : constant Entity_Id :=
138 Underlying_Type (Get_Actual_Subtype (Act_Lhs));
139 R_Type : Entity_Id :=
140 Underlying_Type (Get_Actual_Subtype (Act_Rhs));
142 L_Slice : constant Boolean := Nkind (Act_Lhs) = N_Slice;
143 R_Slice : constant Boolean := Nkind (Act_Rhs) = N_Slice;
145 Crep : constant Boolean := Change_Of_Representation (N);
150 Ndim : constant Pos := Number_Dimensions (L_Type);
152 Loop_Required : Boolean := False;
153 -- This switch is set to True if the array move must be done using
154 -- an explicit front end generated loop.
156 function Has_Address_Clause (Exp : Node_Id) return Boolean;
157 -- Test if Exp is a reference to an array whose declaration has
158 -- an address clause, or it is a slice of such an array.
160 function Is_Formal_Array (Exp : Node_Id) return Boolean;
161 -- Test if Exp is a reference to an array which is either a formal
162 -- parameter or a slice of a formal parameter. These are the cases
163 -- where hidden aliasing can occur.
165 function Is_Non_Local_Array (Exp : Node_Id) return Boolean;
166 -- Determine if Exp is a reference to an array variable which is other
167 -- than an object defined in the current scope, or a slice of such
168 -- an object. Such objects can be aliased to parameters (unlike local
169 -- array references).
171 function Possible_Unaligned_Slice (Arg : Node_Id) return Boolean;
172 -- Returns True if Arg (either the left or right hand side of the
173 -- assignment) is a slice that could be unaligned wrt the array type.
174 -- This is true if Arg is a component of a packed record, or is
175 -- a record component to which a component clause applies. This
176 -- is a little pessimistic, but the result of an unnecessary
177 -- decision that something is possibly unaligned is only to
178 -- generate a front end loop, which is not so terrible.
179 -- It would really be better if backend handled this ???
181 ------------------------
182 -- Has_Address_Clause --
183 ------------------------
185 function Has_Address_Clause (Exp : Node_Id) return Boolean is
188 (Is_Entity_Name (Exp) and then
189 Present (Address_Clause (Entity (Exp))))
191 (Nkind (Exp) = N_Slice and then Has_Address_Clause (Prefix (Exp)));
192 end Has_Address_Clause;
194 ---------------------
195 -- Is_Formal_Array --
196 ---------------------
198 function Is_Formal_Array (Exp : Node_Id) return Boolean is
201 (Is_Entity_Name (Exp) and then Is_Formal (Entity (Exp)))
203 (Nkind (Exp) = N_Slice and then Is_Formal_Array (Prefix (Exp)));
206 ------------------------
207 -- Is_Non_Local_Array --
208 ------------------------
210 function Is_Non_Local_Array (Exp : Node_Id) return Boolean is
212 return (Is_Entity_Name (Exp)
213 and then Scope (Entity (Exp)) /= Current_Scope)
214 or else (Nkind (Exp) = N_Slice
215 and then Is_Non_Local_Array (Prefix (Exp)));
216 end Is_Non_Local_Array;
218 ------------------------------
219 -- Possible_Unaligned_Slice --
220 ------------------------------
222 function Possible_Unaligned_Slice (Arg : Node_Id) return Boolean is
224 -- No issue if this is not a slice, or else strict alignment
225 -- is not required in any case.
227 if Nkind (Arg) /= N_Slice
228 or else not Target_Strict_Alignment
233 -- No issue if the component type is a byte or byte aligned
236 Array_Typ : constant Entity_Id := Etype (Arg);
237 Comp_Typ : constant Entity_Id := Component_Type (Array_Typ);
238 Pref : constant Node_Id := Prefix (Arg);
241 if Known_Alignment (Array_Typ) then
242 if Alignment (Array_Typ) = 1 then
246 elsif Known_Component_Size (Array_Typ) then
247 if Component_Size (Array_Typ) = 1 then
251 elsif Known_Esize (Comp_Typ) then
252 if Esize (Comp_Typ) <= System_Storage_Unit then
257 -- No issue if this is not a selected component
259 if Nkind (Pref) /= N_Selected_Component then
263 -- Else we test for a possibly unaligned component
266 Is_Packed (Etype (Pref))
268 Present (Component_Clause (Entity (Selector_Name (Pref))));
270 end Possible_Unaligned_Slice;
272 -- Determine if Lhs, Rhs are formal arrays or non-local arrays
274 Lhs_Formal : constant Boolean := Is_Formal_Array (Act_Lhs);
275 Rhs_Formal : constant Boolean := Is_Formal_Array (Act_Rhs);
277 Lhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Lhs);
278 Rhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Rhs);
280 -- Start of processing for Expand_Assign_Array
283 -- Deal with length check, note that the length check is done with
284 -- respect to the right hand side as given, not a possible underlying
285 -- renamed object, since this would generate incorrect extra checks.
287 Apply_Length_Check (Rhs, L_Type);
289 -- We start by assuming that the move can be done in either
290 -- direction, i.e. that the two sides are completely disjoint.
292 Set_Forwards_OK (N, True);
293 Set_Backwards_OK (N, True);
295 -- Normally it is only the slice case that can lead to overlap,
296 -- and explicit checks for slices are made below. But there is
297 -- one case where the slice can be implicit and invisible to us
298 -- and that is the case where we have a one dimensional array,
299 -- and either both operands are parameters, or one is a parameter
300 -- and the other is a global variable. In this case the parameter
301 -- could be a slice that overlaps with the other parameter.
303 -- Check for the case of slices requiring an explicit loop. Normally
304 -- it is only the explicit slice cases that bother us, but in the
305 -- case of one dimensional arrays, parameters can be slices that
306 -- are passed by reference, so we can have aliasing for assignments
307 -- from one parameter to another, or assignments between parameters
308 -- and non-local variables.
310 -- Note: overlap is never possible if there is a change of
311 -- representation, so we can exclude this case
316 ((Lhs_Formal and Rhs_Formal)
318 (Lhs_Formal and Rhs_Non_Local_Var)
320 (Rhs_Formal and Lhs_Non_Local_Var))
322 -- In the case of compiling for the Java Virtual Machine,
323 -- slices are always passed by making a copy, so we don't
324 -- have to worry about overlap. We also want to prevent
325 -- generation of "<" comparisons for array addresses,
326 -- since that's a meaningless operation on the JVM.
330 Set_Forwards_OK (N, False);
331 Set_Backwards_OK (N, False);
333 -- Note: the bit-packed case is not worrisome here, since if
334 -- we have a slice passed as a parameter, it is always aligned
335 -- on a byte boundary, and if there are no explicit slices, the
336 -- assignment can be performed directly.
339 -- We certainly must use a loop for change of representation
340 -- and also we use the operand of the conversion on the right
341 -- hand side as the effective right hand side (the component
342 -- types must match in this situation).
345 Act_Rhs := Get_Referenced_Object (Rhs);
346 R_Type := Get_Actual_Subtype (Act_Rhs);
347 Loop_Required := True;
349 -- Arrays with controlled components are expanded into a loop
350 -- to force calls to adjust at the component level.
352 elsif Has_Controlled_Component (L_Type) then
353 Loop_Required := True;
355 -- Case where no slice is involved
357 elsif not L_Slice and not R_Slice then
359 -- The following code deals with the case of unconstrained bit
360 -- packed arrays. The problem is that the template for such
361 -- arrays contains the bounds of the actual source level array,
363 -- But the copy of an entire array requires the bounds of the
364 -- underlying array. It would be nice if the back end could take
365 -- care of this, but right now it does not know how, so if we
366 -- have such a type, then we expand out into a loop, which is
367 -- inefficient but works correctly. If we don't do this, we
368 -- get the wrong length computed for the array to be moved.
369 -- The two cases we need to worry about are:
371 -- Explicit deference of an unconstrained packed array type as
372 -- in the following example:
375 -- type BITS is array(INTEGER range <>) of BOOLEAN;
376 -- pragma PACK(BITS);
377 -- type A is access BITS;
380 -- P1 := new BITS (1 .. 65_535);
381 -- P2 := new BITS (1 .. 65_535);
385 -- A formal parameter reference with an unconstrained bit
386 -- array type is the other case we need to worry about (here
387 -- we assume the same BITS type declared above:
389 -- procedure Write_All (File : out BITS; Contents : in BITS);
391 -- File.Storage := Contents;
394 -- We expand to a loop in either of these two cases.
396 -- Question for future thought. Another potentially more efficient
397 -- approach would be to create the actual subtype, and then do an
398 -- unchecked conversion to this actual subtype ???
400 Check_Unconstrained_Bit_Packed_Array : declare
402 function Is_UBPA_Reference (Opnd : Node_Id) return Boolean;
403 -- Function to perform required test for the first case,
404 -- above (dereference of an unconstrained bit packed array)
406 -----------------------
407 -- Is_UBPA_Reference --
408 -----------------------
410 function Is_UBPA_Reference (Opnd : Node_Id) return Boolean is
411 Typ : constant Entity_Id := Underlying_Type (Etype (Opnd));
413 Des_Type : Entity_Id;
416 if Present (Packed_Array_Type (Typ))
417 and then Is_Array_Type (Packed_Array_Type (Typ))
418 and then not Is_Constrained (Packed_Array_Type (Typ))
422 elsif Nkind (Opnd) = N_Explicit_Dereference then
423 P_Type := Underlying_Type (Etype (Prefix (Opnd)));
425 if not Is_Access_Type (P_Type) then
429 Des_Type := Designated_Type (P_Type);
431 Is_Bit_Packed_Array (Des_Type)
432 and then not Is_Constrained (Des_Type);
438 end Is_UBPA_Reference;
440 -- Start of processing for Check_Unconstrained_Bit_Packed_Array
443 if Is_UBPA_Reference (Lhs)
445 Is_UBPA_Reference (Rhs)
447 Loop_Required := True;
449 -- Here if we do not have the case of a reference to a bit
450 -- packed unconstrained array case. In this case gigi can
451 -- most certainly handle the assignment if a forwards move
454 -- (could it handle the backwards case also???)
456 elsif Forwards_OK (N) then
459 end Check_Unconstrained_Bit_Packed_Array;
461 -- Gigi can always handle the assignment if the right side is a string
462 -- literal (note that overlap is definitely impossible in this case).
464 elsif Nkind (Rhs) = N_String_Literal then
467 -- If either operand is bit packed, then we need a loop, since we
468 -- can't be sure that the slice is byte aligned. Similarly, if either
469 -- operand is a possibly unaligned slice, then we need a loop (since
470 -- gigi cannot handle unaligned slices).
472 elsif Is_Bit_Packed_Array (L_Type)
473 or else Is_Bit_Packed_Array (R_Type)
474 or else Possible_Unaligned_Slice (Lhs)
475 or else Possible_Unaligned_Slice (Rhs)
477 Loop_Required := True;
479 -- If we are not bit-packed, and we have only one slice, then no
480 -- overlap is possible except in the parameter case, so we can let
481 -- gigi handle things.
483 elsif not (L_Slice and R_Slice) then
484 if Forwards_OK (N) then
489 -- Come here to compelete the analysis
491 -- Loop_Required: Set to True if we know that a loop is required
492 -- regardless of overlap considerations.
494 -- Forwards_OK: Set to False if we already know that a forwards
495 -- move is not safe, else set to True.
497 -- Backwards_OK: Set to False if we already know that a backwards
498 -- move is not safe, else set to True
500 -- Our task at this stage is to complete the overlap analysis, which
501 -- can result in possibly setting Forwards_OK or Backwards_OK to
502 -- False, and then generating the final code, either by deciding
503 -- that it is OK after all to let Gigi handle it, or by generating
504 -- appropriate code in the front end.
507 L_Index_Typ : constant Node_Id := Etype (First_Index (L_Type));
508 R_Index_Typ : constant Node_Id := Etype (First_Index (R_Type));
510 Left_Lo : constant Node_Id := Type_Low_Bound (L_Index_Typ);
511 Left_Hi : constant Node_Id := Type_High_Bound (L_Index_Typ);
512 Right_Lo : constant Node_Id := Type_Low_Bound (R_Index_Typ);
513 Right_Hi : constant Node_Id := Type_High_Bound (R_Index_Typ);
515 Act_L_Array : Node_Id;
516 Act_R_Array : Node_Id;
522 Cresult : Compare_Result;
525 -- Get the expressions for the arrays. If we are dealing with a
526 -- private type, then convert to the underlying type. We can do
527 -- direct assignments to an array that is a private type, but
528 -- we cannot assign to elements of the array without this extra
529 -- unchecked conversion.
531 if Nkind (Act_Lhs) = N_Slice then
532 Larray := Prefix (Act_Lhs);
536 if Is_Private_Type (Etype (Larray)) then
539 (Underlying_Type (Etype (Larray)), Larray);
543 if Nkind (Act_Rhs) = N_Slice then
544 Rarray := Prefix (Act_Rhs);
548 if Is_Private_Type (Etype (Rarray)) then
551 (Underlying_Type (Etype (Rarray)), Rarray);
555 -- If both sides are slices, we must figure out whether
556 -- it is safe to do the move in one direction or the other
557 -- It is always safe if there is a change of representation
558 -- since obviously two arrays with different representations
559 -- cannot possibly overlap.
561 if (not Crep) and L_Slice and R_Slice then
562 Act_L_Array := Get_Referenced_Object (Prefix (Act_Lhs));
563 Act_R_Array := Get_Referenced_Object (Prefix (Act_Rhs));
565 -- If both left and right hand arrays are entity names, and
566 -- refer to different entities, then we know that the move
567 -- is safe (the two storage areas are completely disjoint).
569 if Is_Entity_Name (Act_L_Array)
570 and then Is_Entity_Name (Act_R_Array)
571 and then Entity (Act_L_Array) /= Entity (Act_R_Array)
575 -- Otherwise, we assume the worst, which is that the two
576 -- arrays are the same array. There is no need to check if
577 -- we know that is the case, because if we don't know it,
578 -- we still have to assume it!
580 -- Generally if the same array is involved, then we have
581 -- an overlapping case. We will have to really assume the
582 -- worst (i.e. set neither of the OK flags) unless we can
583 -- determine the lower or upper bounds at compile time and
587 Cresult := Compile_Time_Compare (Left_Lo, Right_Lo);
589 if Cresult = Unknown then
590 Cresult := Compile_Time_Compare (Left_Hi, Right_Hi);
594 when LT | LE | EQ => Set_Backwards_OK (N, False);
595 when GT | GE => Set_Forwards_OK (N, False);
596 when NE | Unknown => Set_Backwards_OK (N, False);
597 Set_Forwards_OK (N, False);
602 -- If after that analysis, Forwards_OK is still True, and
603 -- Loop_Required is False, meaning that we have not discovered
604 -- some non-overlap reason for requiring a loop, then we can
605 -- still let gigi handle it.
607 if not Loop_Required then
608 if Forwards_OK (N) then
613 -- Here is where a memmove would be appropriate ???
617 -- At this stage we have to generate an explicit loop, and
618 -- we have the following cases:
620 -- Forwards_OK = True
622 -- Rnn : right_index := right_index'First;
623 -- for Lnn in left-index loop
624 -- left (Lnn) := right (Rnn);
625 -- Rnn := right_index'Succ (Rnn);
628 -- Note: the above code MUST be analyzed with checks off,
629 -- because otherwise the Succ could overflow. But in any
630 -- case this is more efficient!
632 -- Forwards_OK = False, Backwards_OK = True
634 -- Rnn : right_index := right_index'Last;
635 -- for Lnn in reverse left-index loop
636 -- left (Lnn) := right (Rnn);
637 -- Rnn := right_index'Pred (Rnn);
640 -- Note: the above code MUST be analyzed with checks off,
641 -- because otherwise the Pred could overflow. But in any
642 -- case this is more efficient!
644 -- Forwards_OK = Backwards_OK = False
646 -- This only happens if we have the same array on each side. It is
647 -- possible to create situations using overlays that violate this,
648 -- but we simply do not promise to get this "right" in this case.
650 -- There are two possible subcases. If the No_Implicit_Conditionals
651 -- restriction is set, then we generate the following code:
654 -- T : constant <operand-type> := rhs;
659 -- If implicit conditionals are permitted, then we generate:
661 -- if Left_Lo <= Right_Lo then
662 -- <code for Forwards_OK = True above>
664 -- <code for Backwards_OK = True above>
667 -- Cases where either Forwards_OK or Backwards_OK is true
669 if Forwards_OK (N) or else Backwards_OK (N) then
671 Expand_Assign_Array_Loop
672 (N, Larray, Rarray, L_Type, R_Type, Ndim,
673 Rev => not Forwards_OK (N)));
675 -- Case of both are false with No_Implicit_Conditionals
677 elsif Restrictions (No_Implicit_Conditionals) then
679 T : Entity_Id := Make_Defining_Identifier (Loc,
684 Make_Block_Statement (Loc,
685 Declarations => New_List (
686 Make_Object_Declaration (Loc,
687 Defining_Identifier => T,
688 Constant_Present => True,
690 New_Occurrence_Of (Etype (Rhs), Loc),
691 Expression => Relocate_Node (Rhs))),
693 Handled_Statement_Sequence =>
694 Make_Handled_Sequence_Of_Statements (Loc,
695 Statements => New_List (
696 Make_Assignment_Statement (Loc,
697 Name => Relocate_Node (Lhs),
698 Expression => New_Occurrence_Of (T, Loc))))));
701 -- Case of both are false with implicit conditionals allowed
704 -- Before we generate this code, we must ensure that the
705 -- left and right side array types are defined. They may
706 -- be itypes, and we cannot let them be defined inside the
707 -- if, since the first use in the then may not be executed.
709 Ensure_Defined (L_Type, N);
710 Ensure_Defined (R_Type, N);
712 -- We normally compare addresses to find out which way round
713 -- to do the loop, since this is realiable, and handles the
714 -- cases of parameters, conversions etc. But we can't do that
715 -- in the bit packed case or the Java VM case, because addresses
718 if not Is_Bit_Packed_Array (L_Type) and then not Java_VM then
722 Unchecked_Convert_To (RTE (RE_Integer_Address),
723 Make_Attribute_Reference (Loc,
725 Make_Indexed_Component (Loc,
727 Duplicate_Subexpr (Larray, True),
728 Expressions => New_List (
729 Make_Attribute_Reference (Loc,
733 Attribute_Name => Name_First))),
734 Attribute_Name => Name_Address)),
737 Unchecked_Convert_To (RTE (RE_Integer_Address),
738 Make_Attribute_Reference (Loc,
740 Make_Indexed_Component (Loc,
742 Duplicate_Subexpr (Rarray, True),
743 Expressions => New_List (
744 Make_Attribute_Reference (Loc,
748 Attribute_Name => Name_First))),
749 Attribute_Name => Name_Address)));
751 -- For the bit packed and Java VM cases we use the bounds.
752 -- That's OK, because we don't have to worry about parameters,
753 -- since they cannot cause overlap. Perhaps we should worry
754 -- about weird slice conversions ???
757 -- Copy the bounds and reset the Analyzed flag, because the
758 -- bounds of the index type itself may be universal, and must
759 -- must be reaanalyzed to acquire the proper type for Gigi.
761 Cleft_Lo := New_Copy_Tree (Left_Lo);
762 Cright_Lo := New_Copy_Tree (Right_Lo);
763 Set_Analyzed (Cleft_Lo, False);
764 Set_Analyzed (Cright_Lo, False);
768 Left_Opnd => Cleft_Lo,
769 Right_Opnd => Cright_Lo);
773 Make_Implicit_If_Statement (N,
774 Condition => Condition,
776 Then_Statements => New_List (
777 Expand_Assign_Array_Loop
778 (N, Larray, Rarray, L_Type, R_Type, Ndim,
781 Else_Statements => New_List (
782 Expand_Assign_Array_Loop
783 (N, Larray, Rarray, L_Type, R_Type, Ndim,
787 Analyze (N, Suppress => All_Checks);
789 end Expand_Assign_Array;
791 ------------------------------
792 -- Expand_Assign_Array_Loop --
793 ------------------------------
795 -- The following is an example of the loop generated for the case of
796 -- a two-dimensional array:
801 -- for L1b in 1 .. 100 loop
805 -- for L3b in 1 .. 100 loop
806 -- vm1 (L1b, L3b) := vm2 (R2b, R4b);
807 -- R4b := Tm1X2'succ(R4b);
810 -- R2b := Tm1X1'succ(R2b);
814 -- Here Rev is False, and Tm1Xn are the subscript types for the right
815 -- hand side. The declarations of R2b and R4b are inserted before the
816 -- original assignment statement.
818 function Expand_Assign_Array_Loop
828 Loc : constant Source_Ptr := Sloc (N);
830 Lnn : array (1 .. Ndim) of Entity_Id;
831 Rnn : array (1 .. Ndim) of Entity_Id;
832 -- Entities used as subscripts on left and right sides
834 L_Index_Type : array (1 .. Ndim) of Entity_Id;
835 R_Index_Type : array (1 .. Ndim) of Entity_Id;
836 -- Left and right index types
848 F_Or_L := Name_First;
852 -- Setup index types and subscript entities
859 L_Index := First_Index (L_Type);
860 R_Index := First_Index (R_Type);
862 for J in 1 .. Ndim loop
864 Make_Defining_Identifier (Loc,
865 Chars => New_Internal_Name ('L'));
868 Make_Defining_Identifier (Loc,
869 Chars => New_Internal_Name ('R'));
871 L_Index_Type (J) := Etype (L_Index);
872 R_Index_Type (J) := Etype (R_Index);
874 Next_Index (L_Index);
875 Next_Index (R_Index);
879 -- Now construct the assignment statement
882 ExprL : List_Id := New_List;
883 ExprR : List_Id := New_List;
886 for J in 1 .. Ndim loop
887 Append_To (ExprL, New_Occurrence_Of (Lnn (J), Loc));
888 Append_To (ExprR, New_Occurrence_Of (Rnn (J), Loc));
892 Make_Assignment_Statement (Loc,
894 Make_Indexed_Component (Loc,
895 Prefix => Duplicate_Subexpr (Larray, Name_Req => True),
896 Expressions => ExprL),
898 Make_Indexed_Component (Loc,
899 Prefix => Duplicate_Subexpr (Rarray, Name_Req => True),
900 Expressions => ExprR));
902 -- Propagate the No_Ctrl_Actions flag to individual assignments
904 Set_No_Ctrl_Actions (Assign, No_Ctrl_Actions (N));
907 -- Now construct the loop from the inside out, with the last subscript
908 -- varying most rapidly. Note that Assign is first the raw assignment
909 -- statement, and then subsequently the loop that wraps it up.
911 for J in reverse 1 .. Ndim loop
913 Make_Block_Statement (Loc,
914 Declarations => New_List (
915 Make_Object_Declaration (Loc,
916 Defining_Identifier => Rnn (J),
918 New_Occurrence_Of (R_Index_Type (J), Loc),
920 Make_Attribute_Reference (Loc,
921 Prefix => New_Occurrence_Of (R_Index_Type (J), Loc),
922 Attribute_Name => F_Or_L))),
924 Handled_Statement_Sequence =>
925 Make_Handled_Sequence_Of_Statements (Loc,
926 Statements => New_List (
927 Make_Implicit_Loop_Statement (N,
929 Make_Iteration_Scheme (Loc,
930 Loop_Parameter_Specification =>
931 Make_Loop_Parameter_Specification (Loc,
932 Defining_Identifier => Lnn (J),
933 Reverse_Present => Rev,
934 Discrete_Subtype_Definition =>
935 New_Reference_To (L_Index_Type (J), Loc))),
937 Statements => New_List (
940 Make_Assignment_Statement (Loc,
941 Name => New_Occurrence_Of (Rnn (J), Loc),
943 Make_Attribute_Reference (Loc,
945 New_Occurrence_Of (R_Index_Type (J), Loc),
946 Attribute_Name => S_Or_P,
947 Expressions => New_List (
948 New_Occurrence_Of (Rnn (J), Loc)))))))));
952 end Expand_Assign_Array_Loop;
954 --------------------------
955 -- Expand_Assign_Record --
956 --------------------------
958 -- The only processing required is in the change of representation
959 -- case, where we must expand the assignment to a series of field
960 -- by field assignments.
962 procedure Expand_Assign_Record (N : Node_Id) is
964 if not Change_Of_Representation (N) then
968 -- At this stage we know that the right hand side is a conversion
971 Loc : constant Source_Ptr := Sloc (N);
972 Lhs : constant Node_Id := Name (N);
973 Rhs : constant Node_Id := Expression (Expression (N));
974 R_Rec : constant Node_Id := Expression (Expression (N));
975 R_Typ : constant Entity_Id := Base_Type (Etype (R_Rec));
976 L_Typ : constant Entity_Id := Etype (Lhs);
977 Decl : constant Node_Id := Declaration_Node (R_Typ);
981 function Find_Component
985 -- Find the component with the given name in the underlying record
986 -- declaration for Typ. We need to use the actual entity because
987 -- the type may be private and resolution by identifier alone would
990 function Make_Component_List_Assign (CL : Node_Id) return List_Id;
991 -- Returns a sequence of statements to assign the components that
992 -- are referenced in the given component list.
994 function Make_Field_Assign (C : Entity_Id) return Node_Id;
995 -- Given C, the entity for a discriminant or component, build
996 -- an assignment for the corresponding field values.
998 function Make_Field_Assigns (CI : List_Id) return List_Id;
999 -- Given CI, a component items list, construct series of statements
1000 -- for fieldwise assignment of the corresponding components.
1002 --------------------
1003 -- Find_Component --
1004 --------------------
1006 function Find_Component
1012 Utyp : constant Entity_Id := Underlying_Type (Typ);
1016 C := First_Entity (Utyp);
1018 while Present (C) loop
1019 if Chars (C) = Chars (Comp) then
1025 raise Program_Error;
1028 --------------------------------
1029 -- Make_Component_List_Assign --
1030 --------------------------------
1032 function Make_Component_List_Assign (CL : Node_Id) return List_Id is
1033 CI : constant List_Id := Component_Items (CL);
1034 VP : constant Node_Id := Variant_Part (CL);
1043 Result := Make_Field_Assigns (CI);
1045 if Present (VP) then
1047 V := First_Non_Pragma (Variants (VP));
1049 while Present (V) loop
1052 DC := First (Discrete_Choices (V));
1053 while Present (DC) loop
1054 Append_To (DCH, New_Copy_Tree (DC));
1059 Make_Case_Statement_Alternative (Loc,
1060 Discrete_Choices => DCH,
1062 Make_Component_List_Assign (Component_List (V))));
1063 Next_Non_Pragma (V);
1067 Make_Case_Statement (Loc,
1069 Make_Selected_Component (Loc,
1070 Prefix => Duplicate_Subexpr (Rhs),
1072 Make_Identifier (Loc, Chars (Name (VP)))),
1073 Alternatives => Alts));
1078 end Make_Component_List_Assign;
1080 -----------------------
1081 -- Make_Field_Assign --
1082 -----------------------
1084 function Make_Field_Assign (C : Entity_Id) return Node_Id is
1089 Make_Assignment_Statement (Loc,
1091 Make_Selected_Component (Loc,
1092 Prefix => Duplicate_Subexpr (Lhs),
1094 New_Occurrence_Of (Find_Component (L_Typ, C), Loc)),
1096 Make_Selected_Component (Loc,
1097 Prefix => Duplicate_Subexpr (Rhs),
1098 Selector_Name => New_Occurrence_Of (C, Loc)));
1100 -- Set Assignment_OK, so discriminants can be assigned
1102 Set_Assignment_OK (Name (A), True);
1104 end Make_Field_Assign;
1106 ------------------------
1107 -- Make_Field_Assigns --
1108 ------------------------
1110 function Make_Field_Assigns (CI : List_Id) return List_Id is
1118 while Present (Item) loop
1119 if Nkind (Item) = N_Component_Declaration then
1121 (Result, Make_Field_Assign (Defining_Identifier (Item)));
1128 end Make_Field_Assigns;
1130 -- Start of processing for Expand_Assign_Record
1133 -- Note that we use the base type for this processing. This results
1134 -- in some extra work in the constrained case, but the change of
1135 -- representation case is so unusual that it is not worth the effort.
1137 -- First copy the discriminants. This is done unconditionally. It
1138 -- is required in the unconstrained left side case, and also in the
1139 -- case where this assignment was constructed during the expansion
1140 -- of a type conversion (since initialization of discriminants is
1141 -- suppressed in this case). It is unnecessary but harmless in
1144 if Has_Discriminants (L_Typ) then
1145 F := First_Discriminant (R_Typ);
1146 while Present (F) loop
1147 Insert_Action (N, Make_Field_Assign (F));
1148 Next_Discriminant (F);
1152 -- We know the underlying type is a record, but its current view
1153 -- may be private. We must retrieve the usable record declaration.
1155 if Nkind (Decl) = N_Private_Type_Declaration
1156 and then Present (Full_View (R_Typ))
1158 RDef := Type_Definition (Declaration_Node (Full_View (R_Typ)));
1160 RDef := Type_Definition (Decl);
1163 if Nkind (RDef) = N_Record_Definition
1164 and then Present (Component_List (RDef))
1167 (N, Make_Component_List_Assign (Component_List (RDef)));
1169 Rewrite (N, Make_Null_Statement (Loc));
1173 end Expand_Assign_Record;
1175 -----------------------------------
1176 -- Expand_N_Assignment_Statement --
1177 -----------------------------------
1179 -- For array types, deal with slice assignments and setting the flags
1180 -- to indicate if it can be statically determined which direction the
1181 -- move should go in. Also deal with generating length checks.
1183 procedure Expand_N_Assignment_Statement (N : Node_Id) is
1184 Loc : constant Source_Ptr := Sloc (N);
1185 Lhs : constant Node_Id := Name (N);
1186 Rhs : constant Node_Id := Expression (N);
1187 Typ : constant Entity_Id := Underlying_Type (Etype (Lhs));
1191 -- Check for a special case where a high level transformation is
1192 -- required. If we have either of:
1197 -- where P is a reference to a bit packed array, then we have to unwind
1198 -- the assignment. The exact meaning of being a reference to a bit
1199 -- packed array is as follows:
1201 -- An indexed component whose prefix is a bit packed array is a
1202 -- reference to a bit packed array.
1204 -- An indexed component or selected component whose prefix is a
1205 -- reference to a bit packed array is itself a reference ot a
1206 -- bit packed array.
1208 -- The required transformation is
1210 -- Tnn : prefix_type := P;
1211 -- Tnn.field := rhs;
1216 -- Tnn : prefix_type := P;
1217 -- Tnn (subscr) := rhs;
1220 -- Since P is going to be evaluated more than once, any subscripts
1221 -- in P must have their evaluation forced.
1223 if (Nkind (Lhs) = N_Indexed_Component
1225 Nkind (Lhs) = N_Selected_Component)
1226 and then Is_Ref_To_Bit_Packed_Array (Prefix (Lhs))
1229 BPAR_Expr : constant Node_Id := Relocate_Node (Prefix (Lhs));
1230 BPAR_Typ : constant Entity_Id := Etype (BPAR_Expr);
1231 Tnn : constant Entity_Id :=
1232 Make_Defining_Identifier (Loc,
1233 Chars => New_Internal_Name ('T'));
1236 -- Insert the post assignment first, because we want to copy
1237 -- the BPAR_Expr tree before it gets analyzed in the context
1238 -- of the pre assignment. Note that we do not analyze the
1239 -- post assignment yet (we cannot till we have completed the
1240 -- analysis of the pre assignment). As usual, the analysis
1241 -- of this post assignment will happen on its own when we
1242 -- "run into" it after finishing the current assignment.
1245 Make_Assignment_Statement (Loc,
1246 Name => New_Copy_Tree (BPAR_Expr),
1247 Expression => New_Occurrence_Of (Tnn, Loc)));
1249 -- At this stage BPAR_Expr is a reference to a bit packed
1250 -- array where the reference was not expanded in the original
1251 -- tree, since it was on the left side of an assignment. But
1252 -- in the pre-assignment statement (the object definition),
1253 -- BPAR_Expr will end up on the right hand side, and must be
1254 -- reexpanded. To achieve this, we reset the analyzed flag
1255 -- of all selected and indexed components down to the actual
1256 -- indexed component for the packed array.
1260 Set_Analyzed (Exp, False);
1262 if Nkind (Exp) = N_Selected_Component
1264 Nkind (Exp) = N_Indexed_Component
1266 Exp := Prefix (Exp);
1272 -- Now we can insert and analyze the pre-assignment.
1274 -- If the right-hand side requires a transient scope, it has
1275 -- already been placed on the stack. However, the declaration is
1276 -- inserted in the tree outside of this scope, and must reflect
1277 -- the proper scope for its variable. This awkward bit is forced
1278 -- by the stricter scope discipline imposed by GCC 2.97.
1281 Uses_Transient_Scope : constant Boolean :=
1282 Scope_Is_Transient and then N = Node_To_Be_Wrapped;
1285 if Uses_Transient_Scope then
1286 New_Scope (Scope (Current_Scope));
1289 Insert_Before_And_Analyze (N,
1290 Make_Object_Declaration (Loc,
1291 Defining_Identifier => Tnn,
1292 Object_Definition => New_Occurrence_Of (BPAR_Typ, Loc),
1293 Expression => BPAR_Expr));
1295 if Uses_Transient_Scope then
1300 -- Now fix up the original assignment and continue processing
1302 Rewrite (Prefix (Lhs),
1303 New_Occurrence_Of (Tnn, Loc));
1307 -- When we have the appropriate type of aggregate in the
1308 -- expression (it has been determined during analysis of the
1309 -- aggregate by setting the delay flag), let's perform in place
1310 -- assignment and thus avoid creating a temporay.
1312 if Is_Delayed_Aggregate (Rhs) then
1313 Convert_Aggr_In_Assignment (N);
1314 Rewrite (N, Make_Null_Statement (Loc));
1319 -- Apply discriminant check if required. If Lhs is an access type
1320 -- to a designated type with discriminants, we must always check.
1322 if Has_Discriminants (Etype (Lhs)) then
1324 -- Skip discriminant check if change of representation. Will be
1325 -- done when the change of representation is expanded out.
1327 if not Change_Of_Representation (N) then
1328 Apply_Discriminant_Check (Rhs, Etype (Lhs), Lhs);
1331 -- If the type is private without discriminants, and the full type
1332 -- has discriminants (necessarily with defaults) a check may still be
1333 -- necessary if the Lhs is aliased. The private determinants must be
1334 -- visible to build the discriminant constraints.
1336 elsif Is_Private_Type (Etype (Lhs))
1337 and then Has_Discriminants (Typ)
1338 and then Nkind (Lhs) = N_Explicit_Dereference
1341 Lt : constant Entity_Id := Etype (Lhs);
1343 Set_Etype (Lhs, Typ);
1344 Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs));
1345 Apply_Discriminant_Check (Rhs, Typ, Lhs);
1346 Set_Etype (Lhs, Lt);
1349 -- If the Lhs has a private type with unknown discriminants, it
1350 -- may have a full view with discriminants, but those are nameable
1351 -- only in the underlying type, so convert the Rhs to it before
1352 -- potential checking.
1354 elsif Has_Unknown_Discriminants (Base_Type (Etype (Lhs)))
1355 and then Has_Discriminants (Typ)
1357 Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs));
1358 Apply_Discriminant_Check (Rhs, Typ, Lhs);
1360 -- In the access type case, we need the same discriminant check,
1361 -- and also range checks if we have an access to constrained array.
1363 elsif Is_Access_Type (Etype (Lhs))
1364 and then Is_Constrained (Designated_Type (Etype (Lhs)))
1366 if Has_Discriminants (Designated_Type (Etype (Lhs))) then
1368 -- Skip discriminant check if change of representation. Will be
1369 -- done when the change of representation is expanded out.
1371 if not Change_Of_Representation (N) then
1372 Apply_Discriminant_Check (Rhs, Etype (Lhs));
1375 elsif Is_Array_Type (Designated_Type (Etype (Lhs))) then
1376 Apply_Range_Check (Rhs, Etype (Lhs));
1378 if Is_Constrained (Etype (Lhs)) then
1379 Apply_Length_Check (Rhs, Etype (Lhs));
1382 if Nkind (Rhs) = N_Allocator then
1384 Target_Typ : constant Entity_Id := Etype (Expression (Rhs));
1385 C_Es : Check_Result;
1392 Etype (Designated_Type (Etype (Lhs))));
1404 -- Apply range check for access type case
1406 elsif Is_Access_Type (Etype (Lhs))
1407 and then Nkind (Rhs) = N_Allocator
1408 and then Nkind (Expression (Rhs)) = N_Qualified_Expression
1410 Analyze_And_Resolve (Expression (Rhs));
1412 (Expression (Rhs), Designated_Type (Etype (Lhs)));
1415 -- Case of assignment to a bit packed array element
1417 if Nkind (Lhs) = N_Indexed_Component
1418 and then Is_Bit_Packed_Array (Etype (Prefix (Lhs)))
1420 Expand_Bit_Packed_Element_Set (N);
1423 -- Case of tagged type assignment
1425 elsif Is_Tagged_Type (Typ)
1426 or else (Controlled_Type (Typ) and then not Is_Array_Type (Typ))
1428 Tagged_Case : declare
1429 L : List_Id := No_List;
1430 Expand_Ctrl_Actions : constant Boolean := not No_Ctrl_Actions (N);
1433 -- In the controlled case, we need to make sure that function
1434 -- calls are evaluated before finalizing the target. In all
1435 -- cases, it makes the expansion easier if the side-effects
1436 -- are removed first.
1438 Remove_Side_Effects (Lhs);
1439 Remove_Side_Effects (Rhs);
1441 -- Avoid recursion in the mechanism
1445 -- If dispatching assignment, we need to dispatch to _assign
1447 if Is_Class_Wide_Type (Typ)
1449 -- If the type is tagged, we may as well use the predefined
1450 -- primitive assignment. This avoids inlining a lot of code
1451 -- and in the class-wide case, the assignment is replaced by
1452 -- a dispatch call to _assign. Note that this cannot be done
1453 -- when discriminant checks are locally suppressed (as in
1454 -- extension aggregate expansions) because otherwise the
1455 -- discriminant check will be performed within the _assign
1458 or else (Is_Tagged_Type (Typ)
1459 and then Chars (Current_Scope) /= Name_uAssign
1460 and then Expand_Ctrl_Actions
1461 and then not Discriminant_Checks_Suppressed (Empty))
1463 -- Fetch the primitive op _assign and proper type to call
1464 -- it. Because of possible conflits between private and
1465 -- full view the proper type is fetched directly from the
1466 -- operation profile.
1469 Op : constant Entity_Id
1470 := Find_Prim_Op (Typ, Name_uAssign);
1471 F_Typ : Entity_Id := Etype (First_Formal (Op));
1474 -- If the assignment is dispatching, make sure to use the
1475 -- ??? where is rest of this comment ???
1477 if Is_Class_Wide_Type (Typ) then
1478 F_Typ := Class_Wide_Type (F_Typ);
1482 Make_Procedure_Call_Statement (Loc,
1483 Name => New_Reference_To (Op, Loc),
1484 Parameter_Associations => New_List (
1485 Unchecked_Convert_To (F_Typ, Duplicate_Subexpr (Lhs)),
1486 Unchecked_Convert_To (F_Typ,
1487 Duplicate_Subexpr (Rhs)))));
1491 L := Make_Tag_Ctrl_Assignment (N);
1493 -- We can't afford to have destructive Finalization Actions
1494 -- in the Self assignment case, so if the target and the
1495 -- source are not obviously different, code is generated to
1496 -- avoid the self assignment case
1498 -- if lhs'address /= rhs'address then
1499 -- <code for controlled and/or tagged assignment>
1502 if not Statically_Different (Lhs, Rhs)
1503 and then Expand_Ctrl_Actions
1506 Make_Implicit_If_Statement (N,
1510 Make_Attribute_Reference (Loc,
1511 Prefix => Duplicate_Subexpr (Lhs),
1512 Attribute_Name => Name_Address),
1515 Make_Attribute_Reference (Loc,
1516 Prefix => Duplicate_Subexpr (Rhs),
1517 Attribute_Name => Name_Address)),
1519 Then_Statements => L));
1522 -- We need to set up an exception handler for implementing
1523 -- 7.6.1 (18). The remaining adjustments are tackled by the
1524 -- implementation of adjust for record_controllers (see
1527 -- This is skipped in No_Run_Time mode, where we in any
1528 -- case exclude the possibility of finalization going on!
1530 if Expand_Ctrl_Actions and then not No_Run_Time then
1532 Make_Block_Statement (Loc,
1533 Handled_Statement_Sequence =>
1534 Make_Handled_Sequence_Of_Statements (Loc,
1536 Exception_Handlers => New_List (
1537 Make_Exception_Handler (Loc,
1538 Exception_Choices =>
1539 New_List (Make_Others_Choice (Loc)),
1540 Statements => New_List (
1541 Make_Raise_Program_Error (Loc,
1543 PE_Finalize_Raised_Exception)
1549 Make_Block_Statement (Loc,
1550 Handled_Statement_Sequence =>
1551 Make_Handled_Sequence_Of_Statements (Loc, Statements => L)));
1553 -- If no restrictions on aborts, protect the whole assignement
1554 -- for controlled objects as per 9.8(11)
1556 if Controlled_Type (Typ)
1557 and then Expand_Ctrl_Actions
1558 and then Abort_Allowed
1561 Blk : constant Entity_Id :=
1562 New_Internal_Entity (
1563 E_Block, Current_Scope, Sloc (N), 'B');
1566 Set_Scope (Blk, Current_Scope);
1567 Set_Etype (Blk, Standard_Void_Type);
1568 Set_Identifier (N, New_Occurrence_Of (Blk, Sloc (N)));
1570 Prepend_To (L, Build_Runtime_Call (Loc, RE_Abort_Defer));
1571 Set_At_End_Proc (Handled_Statement_Sequence (N),
1572 New_Occurrence_Of (RTE (RE_Abort_Undefer_Direct), Loc));
1573 Expand_At_End_Handler
1574 (Handled_Statement_Sequence (N), Blk);
1584 elsif Is_Array_Type (Typ) then
1586 Actual_Rhs : Node_Id := Rhs;
1589 while Nkind (Actual_Rhs) = N_Type_Conversion
1591 Nkind (Actual_Rhs) = N_Qualified_Expression
1593 Actual_Rhs := Expression (Actual_Rhs);
1596 Expand_Assign_Array (N, Actual_Rhs);
1602 elsif Is_Record_Type (Typ) then
1603 Expand_Assign_Record (N);
1606 -- Scalar types. This is where we perform the processing related
1607 -- to the requirements of (RM 13.9.1(9-11)) concerning the handling
1608 -- of invalid scalar values.
1610 elsif Is_Scalar_Type (Typ) then
1612 -- Case where right side is known valid
1614 if Expr_Known_Valid (Rhs) then
1616 -- Here the right side is valid, so it is fine. The case to
1617 -- deal with is when the left side is a local variable reference
1618 -- whose value is not currently known to be valid. If this is
1619 -- the case, and the assignment appears in an unconditional
1620 -- context, then we can mark the left side as now being valid.
1622 if Is_Local_Variable_Reference (Lhs)
1623 and then not Is_Known_Valid (Entity (Lhs))
1624 and then In_Unconditional_Context (N)
1626 Set_Is_Known_Valid (Entity (Lhs), True);
1629 -- Case where right side may be invalid in the sense of the RM
1630 -- reference above. The RM does not require that we check for
1631 -- the validity on an assignment, but it does require that the
1632 -- assignment of an invalid value not cause erroneous behavior.
1634 -- The general approach in GNAT is to use the Is_Known_Valid flag
1635 -- to avoid the need for validity checking on assignments. However
1636 -- in some cases, we have to do validity checking in order to make
1637 -- sure that the setting of this flag is correct.
1640 -- Validate right side if we are validating copies
1642 if Validity_Checks_On
1643 and then Validity_Check_Copies
1647 -- We can propagate this to the left side where appropriate
1649 if Is_Local_Variable_Reference (Lhs)
1650 and then not Is_Known_Valid (Entity (Lhs))
1651 and then In_Unconditional_Context (N)
1653 Set_Is_Known_Valid (Entity (Lhs), True);
1656 -- Otherwise check to see what should be done
1658 -- If left side is a local variable, then we just set its
1659 -- flag to indicate that its value may no longer be valid,
1660 -- since we are copying a potentially invalid value.
1662 elsif Is_Local_Variable_Reference (Lhs) then
1663 Set_Is_Known_Valid (Entity (Lhs), False);
1665 -- Check for case of a non-local variable on the left side
1666 -- which is currently known to be valid. In this case, we
1667 -- simply ensure that the right side is valid. We only play
1668 -- the game of copying validity status for local variables,
1669 -- since we are doing this statically, not by tracing the
1672 elsif Is_Entity_Name (Lhs)
1673 and then Is_Known_Valid (Entity (Lhs))
1675 -- Note that the Ensure_Valid call is ignored if the
1676 -- Validity_Checking mode is set to none so we do not
1677 -- need to worry about that case here.
1681 -- In all other cases, we can safely copy an invalid value
1682 -- without worrying about the status of the left side. Since
1683 -- it is not a variable reference it will not be considered
1684 -- as being known to be valid in any case.
1692 -- Defend against invalid subscripts on left side if we are in
1693 -- standard validity checking mode. No need to do this if we
1694 -- are checking all subscripts.
1696 if Validity_Checks_On
1697 and then Validity_Check_Default
1698 and then not Validity_Check_Subscripts
1700 Check_Valid_Lvalue_Subscripts (Lhs);
1702 end Expand_N_Assignment_Statement;
1704 ------------------------------
1705 -- Expand_N_Block_Statement --
1706 ------------------------------
1708 -- Encode entity names defined in block statement
1710 procedure Expand_N_Block_Statement (N : Node_Id) is
1712 Qualify_Entity_Names (N);
1713 end Expand_N_Block_Statement;
1715 -----------------------------
1716 -- Expand_N_Case_Statement --
1717 -----------------------------
1719 procedure Expand_N_Case_Statement (N : Node_Id) is
1720 Loc : constant Source_Ptr := Sloc (N);
1721 Expr : constant Node_Id := Expression (N);
1724 -- Check for the situation where we know at compile time which
1725 -- branch will be taken
1727 if Compile_Time_Known_Value (Expr) then
1729 Val : constant Uint := Expr_Value (Expr);
1734 Alt := First (Alternatives (N));
1736 Choice := First (Discrete_Choices (Alt));
1737 while Present (Choice) loop
1739 -- Others choice, always matches
1741 if Nkind (Choice) = N_Others_Choice then
1744 -- Range, check if value is in the range
1746 elsif Nkind (Choice) = N_Range then
1748 Val >= Expr_Value (Low_Bound (Choice))
1750 Val <= Expr_Value (High_Bound (Choice));
1752 -- Choice is a subtype name. Note that we know it must
1753 -- be a static subtype, since otherwise it would have
1754 -- been diagnosed as illegal.
1756 elsif Is_Entity_Name (Choice)
1757 and then Is_Type (Entity (Choice))
1759 exit when Is_In_Range (Expr, Etype (Choice));
1761 -- Choice is a subtype indication
1763 elsif Nkind (Choice) = N_Subtype_Indication then
1765 C : constant Node_Id := Constraint (Choice);
1766 R : constant Node_Id := Range_Expression (C);
1770 Val >= Expr_Value (Low_Bound (R))
1772 Val <= Expr_Value (High_Bound (R));
1775 -- Choice is a simple expression
1778 exit Search when Val = Expr_Value (Choice);
1785 pragma Assert (Present (Alt));
1788 -- The above loop *must* terminate by finding a match, since
1789 -- we know the case statement is valid, and the value of the
1790 -- expression is known at compile time. When we fall out of
1791 -- the loop, Alt points to the alternative that we know will
1792 -- be selected at run time.
1794 -- Move the statements from this alternative after the case
1795 -- statement. They are already analyzed, so will be skipped
1798 Insert_List_After (N, Statements (Alt));
1800 -- That leaves the case statement as a shell. The alternative
1801 -- that wlil be executed is reset to a null list. So now we can
1802 -- kill the entire case statement.
1804 Kill_Dead_Code (Expression (N));
1805 Kill_Dead_Code (Alternatives (N));
1806 Rewrite (N, Make_Null_Statement (Loc));
1809 -- Here if the choice is not determined at compile time
1811 -- If the last alternative is not an Others choice, replace it with an
1812 -- N_Others_Choice. Note that we do not bother to call Analyze on the
1813 -- modified case statement, since it's only effect would be to compute
1814 -- the contents of the Others_Discrete_Choices node laboriously, and of
1815 -- course we already know the list of choices that corresponds to the
1816 -- others choice (it's the list we are replacing!)
1820 Altnode : constant Node_Id := Last (Alternatives (N));
1821 Others_Node : Node_Id;
1824 if Nkind (First (Discrete_Choices (Altnode)))
1827 Others_Node := Make_Others_Choice (Sloc (Altnode));
1828 Set_Others_Discrete_Choices
1829 (Others_Node, Discrete_Choices (Altnode));
1830 Set_Discrete_Choices (Altnode, New_List (Others_Node));
1833 -- If checks are on, ensure argument is valid (RM 5.4(13)). This
1834 -- is only done for case statements frpm in the source program.
1835 -- We don't just call Ensure_Valid here, because the requirement
1836 -- is more strenous than usual, in that it is required that
1837 -- Constraint_Error be raised.
1839 if Comes_From_Source (N)
1840 and then Validity_Checks_On
1841 and then Validity_Check_Default
1842 and then not Expr_Known_Valid (Expr)
1844 Insert_Valid_Check (Expr);
1848 end Expand_N_Case_Statement;
1850 -----------------------------
1851 -- Expand_N_Exit_Statement --
1852 -----------------------------
1854 -- The only processing required is to deal with a possible C/Fortran
1855 -- boolean value used as the condition for the exit statement.
1857 procedure Expand_N_Exit_Statement (N : Node_Id) is
1859 Adjust_Condition (Condition (N));
1860 end Expand_N_Exit_Statement;
1862 -----------------------------
1863 -- Expand_N_Goto_Statement --
1864 -----------------------------
1866 -- Add poll before goto if polling active
1868 procedure Expand_N_Goto_Statement (N : Node_Id) is
1870 Generate_Poll_Call (N);
1871 end Expand_N_Goto_Statement;
1873 ---------------------------
1874 -- Expand_N_If_Statement --
1875 ---------------------------
1877 -- First we deal with the case of C and Fortran convention boolean
1878 -- values, with zero/non-zero semantics.
1880 -- Second, we deal with the obvious rewriting for the cases where the
1881 -- condition of the IF is known at compile time to be True or False.
1883 -- Third, we remove elsif parts which have non-empty Condition_Actions
1884 -- and rewrite as independent if statements. For example:
1895 -- <<condition actions of y>>
1901 -- This rewriting is needed if at least one elsif part has a non-empty
1902 -- Condition_Actions list. We also do the same processing if there is
1903 -- a constant condition in an elsif part (in conjunction with the first
1904 -- processing step mentioned above, for the recursive call made to deal
1905 -- with the created inner if, this deals with properly optimizing the
1906 -- cases of constant elsif conditions).
1908 procedure Expand_N_If_Statement (N : Node_Id) is
1914 Adjust_Condition (Condition (N));
1916 -- The following loop deals with constant conditions for the IF. We
1917 -- need a loop because as we eliminate False conditions, we grab the
1918 -- first elsif condition and use it as the primary condition.
1920 while Compile_Time_Known_Value (Condition (N)) loop
1922 -- If condition is True, we can simply rewrite the if statement
1923 -- now by replacing it by the series of then statements.
1925 if Is_True (Expr_Value (Condition (N))) then
1927 -- All the else parts can be killed
1929 Kill_Dead_Code (Elsif_Parts (N));
1930 Kill_Dead_Code (Else_Statements (N));
1932 Hed := Remove_Head (Then_Statements (N));
1933 Insert_List_After (N, Then_Statements (N));
1937 -- If condition is False, then we can delete the condition and
1938 -- the Then statements
1941 -- We do not delete the condition if constant condition
1942 -- warnings are enabled, since otherwise we end up deleting
1943 -- the desired warning. Of course the backend will get rid
1944 -- of this True/False test anyway, so nothing is lost here.
1946 if not Constant_Condition_Warnings then
1947 Kill_Dead_Code (Condition (N));
1950 Kill_Dead_Code (Then_Statements (N));
1952 -- If there are no elsif statements, then we simply replace
1953 -- the entire if statement by the sequence of else statements.
1955 if No (Elsif_Parts (N)) then
1957 if No (Else_Statements (N))
1958 or else Is_Empty_List (Else_Statements (N))
1961 Make_Null_Statement (Sloc (N)));
1964 Hed := Remove_Head (Else_Statements (N));
1965 Insert_List_After (N, Else_Statements (N));
1971 -- If there are elsif statements, the first of them becomes
1972 -- the if/then section of the rebuilt if statement This is
1973 -- the case where we loop to reprocess this copied condition.
1976 Hed := Remove_Head (Elsif_Parts (N));
1977 Insert_Actions (N, Condition_Actions (Hed));
1978 Set_Condition (N, Condition (Hed));
1979 Set_Then_Statements (N, Then_Statements (Hed));
1981 if Is_Empty_List (Elsif_Parts (N)) then
1982 Set_Elsif_Parts (N, No_List);
1988 -- Loop through elsif parts, dealing with constant conditions and
1989 -- possible expression actions that are present.
1991 if Present (Elsif_Parts (N)) then
1992 E := First (Elsif_Parts (N));
1993 while Present (E) loop
1994 Adjust_Condition (Condition (E));
1996 -- If there are condition actions, then we rewrite the if
1997 -- statement as indicated above. We also do the same rewrite
1998 -- if the condition is True or False. The further processing
1999 -- of this constant condition is then done by the recursive
2000 -- call to expand the newly created if statement
2002 if Present (Condition_Actions (E))
2003 or else Compile_Time_Known_Value (Condition (E))
2005 -- Note this is not an implicit if statement, since it is
2006 -- part of an explicit if statement in the source (or of an
2007 -- implicit if statement that has already been tested).
2010 Make_If_Statement (Sloc (E),
2011 Condition => Condition (E),
2012 Then_Statements => Then_Statements (E),
2013 Elsif_Parts => No_List,
2014 Else_Statements => Else_Statements (N));
2016 -- Elsif parts for new if come from remaining elsif's of parent
2018 while Present (Next (E)) loop
2019 if No (Elsif_Parts (New_If)) then
2020 Set_Elsif_Parts (New_If, New_List);
2023 Append (Remove_Next (E), Elsif_Parts (New_If));
2026 Set_Else_Statements (N, New_List (New_If));
2028 if Present (Condition_Actions (E)) then
2029 Insert_List_Before (New_If, Condition_Actions (E));
2034 if Is_Empty_List (Elsif_Parts (N)) then
2035 Set_Elsif_Parts (N, No_List);
2041 -- No special processing for that elsif part, move to next
2048 end Expand_N_If_Statement;
2050 -----------------------------
2051 -- Expand_N_Loop_Statement --
2052 -----------------------------
2054 -- 1. Deal with while condition for C/Fortran boolean
2055 -- 2. Deal with loops with a non-standard enumeration type range
2056 -- 3. Deal with while loops where Condition_Actions is set
2057 -- 4. Insert polling call if required
2059 procedure Expand_N_Loop_Statement (N : Node_Id) is
2060 Loc : constant Source_Ptr := Sloc (N);
2061 Isc : constant Node_Id := Iteration_Scheme (N);
2064 if Present (Isc) then
2065 Adjust_Condition (Condition (Isc));
2068 if Is_Non_Empty_List (Statements (N)) then
2069 Generate_Poll_Call (First (Statements (N)));
2076 -- Handle the case where we have a for loop with the range type being
2077 -- an enumeration type with non-standard representation. In this case
2080 -- for x in [reverse] a .. b loop
2086 -- for xP in [reverse] integer
2087 -- range etype'Pos (a) .. etype'Pos (b) loop
2089 -- x : constant etype := Pos_To_Rep (xP);
2095 if Present (Loop_Parameter_Specification (Isc)) then
2097 LPS : constant Node_Id := Loop_Parameter_Specification (Isc);
2098 Loop_Id : constant Entity_Id := Defining_Identifier (LPS);
2099 Ltype : constant Entity_Id := Etype (Loop_Id);
2100 Btype : constant Entity_Id := Base_Type (Ltype);
2105 if not Is_Enumeration_Type (Btype)
2106 or else No (Enum_Pos_To_Rep (Btype))
2112 Make_Defining_Identifier (Loc,
2113 Chars => New_External_Name (Chars (Loop_Id), 'P'));
2115 Lo := Type_Low_Bound (Ltype);
2116 Hi := Type_High_Bound (Ltype);
2119 Make_Loop_Statement (Loc,
2120 Identifier => Identifier (N),
2123 Make_Iteration_Scheme (Loc,
2124 Loop_Parameter_Specification =>
2125 Make_Loop_Parameter_Specification (Loc,
2126 Defining_Identifier => New_Id,
2127 Reverse_Present => Reverse_Present (LPS),
2129 Discrete_Subtype_Definition =>
2130 Make_Subtype_Indication (Loc,
2133 New_Reference_To (Standard_Natural, Loc),
2136 Make_Range_Constraint (Loc,
2141 Make_Attribute_Reference (Loc,
2143 New_Reference_To (Btype, Loc),
2145 Attribute_Name => Name_Pos,
2147 Expressions => New_List (
2149 (Type_Low_Bound (Ltype)))),
2152 Make_Attribute_Reference (Loc,
2154 New_Reference_To (Btype, Loc),
2156 Attribute_Name => Name_Pos,
2158 Expressions => New_List (
2160 (Type_High_Bound (Ltype))))))))),
2162 Statements => New_List (
2163 Make_Block_Statement (Loc,
2164 Declarations => New_List (
2165 Make_Object_Declaration (Loc,
2166 Defining_Identifier => Loop_Id,
2167 Constant_Present => True,
2168 Object_Definition => New_Reference_To (Ltype, Loc),
2170 Make_Indexed_Component (Loc,
2172 New_Reference_To (Enum_Pos_To_Rep (Btype), Loc),
2173 Expressions => New_List (
2174 New_Reference_To (New_Id, Loc))))),
2176 Handled_Statement_Sequence =>
2177 Make_Handled_Sequence_Of_Statements (Loc,
2178 Statements => Statements (N)))),
2180 End_Label => End_Label (N)));
2185 -- Second case, if we have a while loop with Condition_Actions set,
2186 -- then we change it into a plain loop:
2195 -- <<condition actions>>
2201 and then Present (Condition_Actions (Isc))
2208 Make_Exit_Statement (Sloc (Condition (Isc)),
2210 Make_Op_Not (Sloc (Condition (Isc)),
2211 Right_Opnd => Condition (Isc)));
2213 Prepend (ES, Statements (N));
2214 Insert_List_Before (ES, Condition_Actions (Isc));
2216 -- This is not an implicit loop, since it is generated in
2217 -- response to the loop statement being processed. If this
2218 -- is itself implicit, the restriction has already been
2219 -- checked. If not, it is an explicit loop.
2222 Make_Loop_Statement (Sloc (N),
2223 Identifier => Identifier (N),
2224 Statements => Statements (N),
2225 End_Label => End_Label (N)));
2230 end Expand_N_Loop_Statement;
2232 -------------------------------
2233 -- Expand_N_Return_Statement --
2234 -------------------------------
2236 procedure Expand_N_Return_Statement (N : Node_Id) is
2237 Loc : constant Source_Ptr := Sloc (N);
2238 Exp : constant Node_Id := Expression (N);
2242 Scope_Id : Entity_Id;
2246 Goto_Stat : Node_Id;
2249 Return_Type : Entity_Id;
2250 Result_Exp : Node_Id;
2251 Result_Id : Entity_Id;
2252 Result_Obj : Node_Id;
2255 -- Case where returned expression is present
2257 if Present (Exp) then
2259 -- Always normalize C/Fortran boolean result. This is not always
2260 -- necessary, but it seems a good idea to minimize the passing
2261 -- around of non-normalized values, and in any case this handles
2262 -- the processing of barrier functions for protected types, which
2263 -- turn the condition into a return statement.
2265 Exptyp := Etype (Exp);
2267 if Is_Boolean_Type (Exptyp)
2268 and then Nonzero_Is_True (Exptyp)
2270 Adjust_Condition (Exp);
2271 Adjust_Result_Type (Exp, Exptyp);
2274 -- Do validity check if enabled for returns
2276 if Validity_Checks_On
2277 and then Validity_Check_Returns
2283 -- Find relevant enclosing scope from which return is returning
2285 Cur_Idx := Scope_Stack.Last;
2287 Scope_Id := Scope_Stack.Table (Cur_Idx).Entity;
2289 if Ekind (Scope_Id) /= E_Block
2290 and then Ekind (Scope_Id) /= E_Loop
2295 Cur_Idx := Cur_Idx - 1;
2296 pragma Assert (Cur_Idx >= 0);
2301 Kind := Ekind (Scope_Id);
2303 -- If it is a return from procedures do no extra steps.
2305 if Kind = E_Procedure or else Kind = E_Generic_Procedure then
2309 pragma Assert (Is_Entry (Scope_Id));
2311 -- Look at the enclosing block to see whether the return is from
2312 -- an accept statement or an entry body.
2314 for J in reverse 0 .. Cur_Idx loop
2315 Scope_Id := Scope_Stack.Table (J).Entity;
2316 exit when Is_Concurrent_Type (Scope_Id);
2319 -- If it is a return from accept statement it should be expanded
2320 -- as a call to RTS Complete_Rendezvous and a goto to the end of
2323 -- (cf : Expand_N_Accept_Statement, Expand_N_Selective_Accept,
2324 -- Expand_N_Accept_Alternative in exp_ch9.adb)
2326 if Is_Task_Type (Scope_Id) then
2328 Call := (Make_Procedure_Call_Statement (Loc,
2329 Name => New_Reference_To
2330 (RTE (RE_Complete_Rendezvous), Loc)));
2331 Insert_Before (N, Call);
2332 -- why not insert actions here???
2335 Acc_Stat := Parent (N);
2336 while Nkind (Acc_Stat) /= N_Accept_Statement loop
2337 Acc_Stat := Parent (Acc_Stat);
2340 Lab_Node := Last (Statements
2341 (Handled_Statement_Sequence (Acc_Stat)));
2343 Goto_Stat := Make_Goto_Statement (Loc,
2344 Name => New_Occurrence_Of
2345 (Entity (Identifier (Lab_Node)), Loc));
2347 Set_Analyzed (Goto_Stat);
2349 Rewrite (N, Goto_Stat);
2352 -- If it is a return from an entry body, put a Complete_Entry_Body
2353 -- call in front of the return.
2355 elsif Is_Protected_Type (Scope_Id) then
2358 Make_Procedure_Call_Statement (Loc,
2359 Name => New_Reference_To
2360 (RTE (RE_Complete_Entry_Body), Loc),
2361 Parameter_Associations => New_List
2362 (Make_Attribute_Reference (Loc,
2366 (Corresponding_Body (Parent (Scope_Id))),
2368 Attribute_Name => Name_Unchecked_Access)));
2370 Insert_Before (N, Call);
2379 Return_Type := Etype (Scope_Id);
2380 Utyp := Underlying_Type (Return_Type);
2382 -- Check the result expression of a scalar function against
2383 -- the subtype of the function by inserting a conversion.
2384 -- This conversion must eventually be performed for other
2385 -- classes of types, but for now it's only done for scalars.
2388 if Is_Scalar_Type (T) then
2389 Rewrite (Exp, Convert_To (Return_Type, Exp));
2393 -- Implement the rules of 6.5(8-10), which require a tag check in
2394 -- the case of a limited tagged return type, and tag reassignment
2395 -- for nonlimited tagged results. These actions are needed when
2396 -- the return type is a specific tagged type and the result
2397 -- expression is a conversion or a formal parameter, because in
2398 -- that case the tag of the expression might differ from the tag
2399 -- of the specific result type.
2401 if Is_Tagged_Type (Utyp)
2402 and then not Is_Class_Wide_Type (Utyp)
2403 and then (Nkind (Exp) = N_Type_Conversion
2404 or else Nkind (Exp) = N_Unchecked_Type_Conversion
2405 or else (Is_Entity_Name (Exp)
2406 and then Ekind (Entity (Exp)) in Formal_Kind))
2408 -- When the return type is limited, perform a check that the
2409 -- tag of the result is the same as the tag of the return type.
2411 if Is_Limited_Type (Return_Type) then
2413 Make_Raise_Constraint_Error (Loc,
2417 Make_Selected_Component (Loc,
2418 Prefix => Duplicate_Subexpr (Exp),
2420 New_Reference_To (Tag_Component (Utyp), Loc)),
2422 Unchecked_Convert_To (RTE (RE_Tag),
2424 (Access_Disp_Table (Base_Type (Utyp)), Loc))),
2425 Reason => CE_Tag_Check_Failed));
2427 -- If the result type is a specific nonlimited tagged type,
2428 -- then we have to ensure that the tag of the result is that
2429 -- of the result type. This is handled by making a copy of the
2430 -- expression in the case where it might have a different tag,
2431 -- namely when the expression is a conversion or a formal
2432 -- parameter. We create a new object of the result type and
2433 -- initialize it from the expression, which will implicitly
2434 -- force the tag to be set appropriately.
2438 Make_Defining_Identifier (Loc, New_Internal_Name ('R'));
2439 Result_Exp := New_Reference_To (Result_Id, Loc);
2442 Make_Object_Declaration (Loc,
2443 Defining_Identifier => Result_Id,
2444 Object_Definition => New_Reference_To (Return_Type, Loc),
2445 Constant_Present => True,
2446 Expression => Relocate_Node (Exp));
2448 Set_Assignment_OK (Result_Obj);
2449 Insert_Action (Exp, Result_Obj);
2451 Rewrite (Exp, Result_Exp);
2452 Analyze_And_Resolve (Exp, Return_Type);
2456 -- Deal with returning variable length objects and controlled types
2458 -- Nothing to do if we are returning by reference, or this is not
2459 -- a type that requires special processing (indicated by the fact
2460 -- that it requires a cleanup scope for the secondary stack case)
2462 if Is_Return_By_Reference_Type (T)
2463 or else not Requires_Transient_Scope (Return_Type)
2467 -- Case of secondary stack not used
2469 elsif Function_Returns_With_DSP (Scope_Id) then
2471 -- Here what we need to do is to always return by reference, since
2472 -- we will return with the stack pointer depressed. We may need to
2473 -- do a copy to a local temporary before doing this return.
2475 No_Secondary_Stack_Case : declare
2476 Local_Copy_Required : Boolean := False;
2477 -- Set to True if a local copy is required
2479 Copy_Ent : Entity_Id;
2480 -- Used for the target entity if a copy is required
2483 -- Declaration used to create copy if needed
2485 procedure Test_Copy_Required (Expr : Node_Id);
2486 -- Determines if Expr represents a return value for which a
2487 -- copy is required. More specifically, a copy is not required
2488 -- if Expr represents an object or component of an object that
2489 -- is either in the local subprogram frame, or is constant.
2490 -- If a copy is required, then Local_Copy_Required is set True.
2492 ------------------------
2493 -- Test_Copy_Required --
2494 ------------------------
2496 procedure Test_Copy_Required (Expr : Node_Id) is
2500 -- If component, test prefix (object containing component)
2502 if Nkind (Expr) = N_Indexed_Component
2504 Nkind (Expr) = N_Selected_Component
2506 Test_Copy_Required (Prefix (Expr));
2509 -- See if we have an entity name
2511 elsif Is_Entity_Name (Expr) then
2512 Ent := Entity (Expr);
2514 -- Constant entity is always OK, no copy required
2516 if Ekind (Ent) = E_Constant then
2519 -- No copy required for local variable
2521 elsif Ekind (Ent) = E_Variable
2522 and then Scope (Ent) = Current_Subprogram
2528 -- All other cases require a copy
2530 Local_Copy_Required := True;
2531 end Test_Copy_Required;
2533 -- Start of processing for No_Secondary_Stack_Case
2536 -- No copy needed if result is from a function call for the
2537 -- same type with the same constrainedness (is the latter a
2538 -- necessary check, or could gigi produce the bounds ???).
2539 -- In this case the result is already being returned by
2540 -- reference with the stack pointer depressed.
2542 if Requires_Transient_Scope (T)
2543 and then Is_Constrained (T) = Is_Constrained (Return_Type)
2544 and then (Nkind (Exp) = N_Function_Call
2546 Nkind (Original_Node (Exp)) = N_Function_Call)
2550 -- We always need a local copy for a controlled type, since
2551 -- we are required to finalize the local value before return.
2552 -- The copy will automatically include the required finalize.
2553 -- Moreover, gigi cannot make this copy, since we need special
2554 -- processing to ensure proper behavior for finalization.
2556 -- Note: the reason we are returning with a depressed stack
2557 -- pointer in the controlled case (even if the type involved
2558 -- is constrained) is that we must make a local copy to deal
2559 -- properly with the requirement that the local result be
2562 elsif Controlled_Type (Utyp) then
2564 Make_Defining_Identifier (Loc,
2565 Chars => New_Internal_Name ('R'));
2567 -- Build declaration to do the copy, and insert it, setting
2568 -- Assignment_OK, because we may be copying a limited type.
2569 -- In addition we set the special flag to inhibit finalize
2570 -- attachment if this is a controlled type (since this attach
2571 -- must be done by the caller, otherwise if we attach it here
2572 -- we will finalize the returned result prematurely).
2575 Make_Object_Declaration (Loc,
2576 Defining_Identifier => Copy_Ent,
2577 Object_Definition => New_Occurrence_Of (Return_Type, Loc),
2578 Expression => Relocate_Node (Exp));
2580 Set_Assignment_OK (Decl);
2581 Set_Delay_Finalize_Attach (Decl);
2582 Insert_Action (N, Decl);
2584 -- Now the actual return uses the copied value
2586 Rewrite (Exp, New_Occurrence_Of (Copy_Ent, Loc));
2587 Analyze_And_Resolve (Exp, Return_Type);
2589 -- Since we have made the copy, gigi does not have to, so
2590 -- we set the By_Ref flag to prevent another copy being made.
2594 -- Non-controlled cases
2597 Test_Copy_Required (Exp);
2599 -- If a local copy is required, then gigi will make the
2600 -- copy, otherwise, we can return the result directly,
2601 -- so set By_Ref to suppress the gigi copy.
2603 if not Local_Copy_Required then
2607 end No_Secondary_Stack_Case;
2609 -- Here if secondary stack is used
2612 -- Make sure that no surrounding block will reclaim the
2613 -- secondary-stack on which we are going to put the result.
2614 -- Not only may this introduce secondary stack leaks but worse,
2615 -- if the reclamation is done too early, then the result we are
2616 -- returning may get clobbered. See example in 7417-003.
2619 S : Entity_Id := Current_Scope;
2622 while Ekind (S) = E_Block or else Ekind (S) = E_Loop loop
2623 Set_Sec_Stack_Needed_For_Return (S, True);
2624 S := Enclosing_Dynamic_Scope (S);
2628 -- Optimize the case where the result is from a function call for
2629 -- the same type with the same constrainedness (is the latter a
2630 -- necessary check, or could gigi produce the bounds ???). In this
2631 -- case either the result is already on the secondary stack, or is
2632 -- already being returned with the stack pointer depressed and no
2633 -- further processing is required except to set the By_Ref flag to
2634 -- ensure that gigi does not attempt an extra unnecessary copy.
2635 -- (actually not just unnecessary but harmfully wrong in the case
2636 -- of a controlled type, where gigi does not know how to do a copy).
2638 if Requires_Transient_Scope (T)
2639 and then Is_Constrained (T) = Is_Constrained (Return_Type)
2640 and then (Nkind (Exp) = N_Function_Call
2641 or else Nkind (Original_Node (Exp)) = N_Function_Call)
2645 -- For controlled types, do the allocation on the sec-stack
2646 -- manually in order to call adjust at the right time
2647 -- type Anon1 is access Return_Type;
2648 -- for Anon1'Storage_pool use ss_pool;
2649 -- Anon2 : anon1 := new Return_Type'(expr);
2650 -- return Anon2.all;
2652 elsif Controlled_Type (Utyp) then
2654 Loc : constant Source_Ptr := Sloc (N);
2655 Temp : constant Entity_Id :=
2656 Make_Defining_Identifier (Loc,
2657 Chars => New_Internal_Name ('R'));
2658 Acc_Typ : constant Entity_Id :=
2659 Make_Defining_Identifier (Loc,
2660 Chars => New_Internal_Name ('A'));
2661 Alloc_Node : Node_Id;
2664 Set_Ekind (Acc_Typ, E_Access_Type);
2666 Set_Associated_Storage_Pool (Acc_Typ, RTE (RE_SS_Pool));
2669 Make_Allocator (Loc,
2671 Make_Qualified_Expression (Loc,
2672 Subtype_Mark => New_Reference_To (Etype (Exp), Loc),
2673 Expression => Relocate_Node (Exp)));
2675 Insert_List_Before_And_Analyze (N, New_List (
2676 Make_Full_Type_Declaration (Loc,
2677 Defining_Identifier => Acc_Typ,
2679 Make_Access_To_Object_Definition (Loc,
2680 Subtype_Indication =>
2681 New_Reference_To (Return_Type, Loc))),
2683 Make_Object_Declaration (Loc,
2684 Defining_Identifier => Temp,
2685 Object_Definition => New_Reference_To (Acc_Typ, Loc),
2686 Expression => Alloc_Node)));
2689 Make_Explicit_Dereference (Loc,
2690 Prefix => New_Reference_To (Temp, Loc)));
2692 Analyze_And_Resolve (Exp, Return_Type);
2695 -- Otherwise use the gigi mechanism to allocate result on the
2699 Set_Storage_Pool (N, RTE (RE_SS_Pool));
2701 -- If we are generating code for the Java VM do not use
2702 -- SS_Allocate since everything is heap-allocated anyway.
2705 Set_Procedure_To_Call (N, RTE (RE_SS_Allocate));
2709 end Expand_N_Return_Statement;
2711 ------------------------------
2712 -- Make_Tag_Ctrl_Assignment --
2713 ------------------------------
2715 function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id is
2716 Loc : constant Source_Ptr := Sloc (N);
2717 L : constant Node_Id := Name (N);
2718 T : constant Entity_Id := Underlying_Type (Etype (L));
2720 Ctrl_Act : constant Boolean := Controlled_Type (T)
2721 and then not No_Ctrl_Actions (N);
2723 Save_Tag : constant Boolean := Is_Tagged_Type (T)
2724 and then not No_Ctrl_Actions (N)
2725 and then not Java_VM;
2726 -- Tags are not saved and restored when Java_VM because JVM tags
2727 -- are represented implicitly in objects.
2730 Tag_Tmp : Entity_Id;
2731 Prev_Tmp : Entity_Id;
2732 Next_Tmp : Entity_Id;
2738 -- Finalize the target of the assignment when controlled.
2739 -- We have two exceptions here:
2741 -- 1. If we are in an init_proc since it is an initialization
2742 -- more than an assignment
2744 -- 2. If the left-hand side is a temporary that was not initialized
2745 -- (or the parent part of a temporary since it is the case in
2746 -- extension aggregates). Such a temporary does not come from
2747 -- source. We must examine the original node for the prefix, because
2748 -- it may be a component of an entry formal, in which case it has
2749 -- been rewritten and does not appear to come from source either.
2753 if not Ctrl_Act then
2756 -- The left hand side is an uninitialized temporary
2758 elsif Nkind (L) = N_Type_Conversion
2759 and then Is_Entity_Name (Expression (L))
2760 and then No_Initialization (Parent (Entity (Expression (L))))
2764 Append_List_To (Res,
2766 Ref => Duplicate_Subexpr (L),
2768 With_Detach => New_Reference_To (Standard_False, Loc)));
2771 Next_Tmp := Make_Defining_Identifier (Loc, New_Internal_Name ('C'));
2773 -- Save the Tag in a local variable Tag_Tmp
2777 Make_Defining_Identifier (Loc, New_Internal_Name ('A'));
2780 Make_Object_Declaration (Loc,
2781 Defining_Identifier => Tag_Tmp,
2782 Object_Definition => New_Reference_To (RTE (RE_Tag), Loc),
2784 Make_Selected_Component (Loc,
2785 Prefix => Duplicate_Subexpr (L),
2786 Selector_Name => New_Reference_To (Tag_Component (T), Loc))));
2788 -- Otherwise Tag_Tmp not used
2794 -- Save the Finalization Pointers in local variables Prev_Tmp and
2795 -- Next_Tmp. For objects with Has_Controlled_Component set, these
2796 -- pointers are in the Record_Controller
2799 Ctrl_Ref := Duplicate_Subexpr (L);
2801 if Has_Controlled_Component (T) then
2803 Make_Selected_Component (Loc,
2806 New_Reference_To (Controller_Component (T), Loc));
2809 Prev_Tmp := Make_Defining_Identifier (Loc, New_Internal_Name ('B'));
2812 Make_Object_Declaration (Loc,
2813 Defining_Identifier => Prev_Tmp,
2815 Object_Definition =>
2816 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc),
2819 Make_Selected_Component (Loc,
2821 Unchecked_Convert_To (RTE (RE_Finalizable), Ctrl_Ref),
2822 Selector_Name => Make_Identifier (Loc, Name_Prev))));
2824 Next_Tmp := Make_Defining_Identifier (Loc, New_Internal_Name ('C'));
2827 Make_Object_Declaration (Loc,
2828 Defining_Identifier => Next_Tmp,
2830 Object_Definition =>
2831 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc),
2834 Make_Selected_Component (Loc,
2836 Unchecked_Convert_To (RTE (RE_Finalizable),
2837 New_Copy_Tree (Ctrl_Ref)),
2838 Selector_Name => Make_Identifier (Loc, Name_Next))));
2840 -- If not controlled type, then Prev_Tmp and Ctrl_Ref unused
2847 -- Do the Assignment
2849 Append_To (Res, Relocate_Node (N));
2855 Make_Assignment_Statement (Loc,
2857 Make_Selected_Component (Loc,
2858 Prefix => Duplicate_Subexpr (L),
2859 Selector_Name => New_Reference_To (Tag_Component (T), Loc)),
2860 Expression => New_Reference_To (Tag_Tmp, Loc)));
2863 -- Restore the finalization pointers
2867 Make_Assignment_Statement (Loc,
2869 Make_Selected_Component (Loc,
2871 Unchecked_Convert_To (RTE (RE_Finalizable),
2872 New_Copy_Tree (Ctrl_Ref)),
2873 Selector_Name => Make_Identifier (Loc, Name_Prev)),
2874 Expression => New_Reference_To (Prev_Tmp, Loc)));
2877 Make_Assignment_Statement (Loc,
2879 Make_Selected_Component (Loc,
2881 Unchecked_Convert_To (RTE (RE_Finalizable),
2882 New_Copy_Tree (Ctrl_Ref)),
2883 Selector_Name => Make_Identifier (Loc, Name_Next)),
2884 Expression => New_Reference_To (Next_Tmp, Loc)));
2887 -- Adjust the target after the assignment when controlled. (not in
2888 -- the init_proc since it is an initialization more than an
2892 Append_List_To (Res,
2894 Ref => Duplicate_Subexpr (L),
2896 Flist_Ref => New_Reference_To (RTE (RE_Global_Final_List), Loc),
2897 With_Attach => Make_Integer_Literal (Loc, 0)));
2901 end Make_Tag_Ctrl_Assignment;