1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2004, 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 Checks; use Checks;
29 with Einfo; use Einfo;
30 with Exp_Aggr; use Exp_Aggr;
31 with Exp_Ch7; use Exp_Ch7;
32 with Exp_Ch11; use Exp_Ch11;
33 with Exp_Dbug; use Exp_Dbug;
34 with Exp_Pakd; use Exp_Pakd;
35 with Exp_Tss; use Exp_Tss;
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 Rident; use Rident;
43 with Rtsfind; use Rtsfind;
44 with Sinfo; use Sinfo;
46 with Sem_Ch8; use Sem_Ch8;
47 with Sem_Ch13; use Sem_Ch13;
48 with Sem_Eval; use Sem_Eval;
49 with Sem_Res; use Sem_Res;
50 with Sem_Util; use Sem_Util;
51 with Snames; use Snames;
52 with Stand; use Stand;
53 with Stringt; use Stringt;
54 with Tbuild; use Tbuild;
55 with Uintp; use Uintp;
56 with Validsw; use Validsw;
58 package body Exp_Ch5 is
60 function Change_Of_Representation (N : Node_Id) return Boolean;
61 -- Determine if the right hand side of the assignment N is a type
62 -- conversion which requires a change of representation. Called
63 -- only for the array and record cases.
65 procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id);
66 -- N is an assignment which assigns an array value. This routine process
67 -- the various special cases and checks required for such assignments,
68 -- including change of representation. Rhs is normally simply the right
69 -- hand side of the assignment, except that if the right hand side is
70 -- a type conversion or a qualified expression, then the Rhs is the
71 -- actual expression inside any such type conversions or qualifications.
73 function Expand_Assign_Array_Loop
80 Rev : Boolean) return Node_Id;
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 case where the assignment must be made component by component,
96 -- either because the target is not byte aligned, or there is a change
99 function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id;
100 -- Generate the necessary code for controlled and Tagged assignment,
101 -- that is to say, finalization of the target before, adjustement of
102 -- the target after and save and restore of the tag and finalization
103 -- pointers which are not 'part of the value' and must not be changed
104 -- upon assignment. N is the original Assignment node.
106 function Possible_Bit_Aligned_Component (N : Node_Id) return Boolean;
107 -- This function is used in processing the assignment of a record or
108 -- indexed component. The argument N is either the left hand or right
109 -- hand side of an assignment, and this function determines if there
110 -- is a record component reference where the record may be bit aligned
111 -- in a manner that causes trouble for the back end (see description
112 -- of Exp_Util.Component_May_Be_Bit_Aligned for further details).
114 ------------------------------
115 -- Change_Of_Representation --
116 ------------------------------
118 function Change_Of_Representation (N : Node_Id) return Boolean is
119 Rhs : constant Node_Id := Expression (N);
122 Nkind (Rhs) = N_Type_Conversion
124 not Same_Representation (Etype (Rhs), Etype (Expression (Rhs)));
125 end Change_Of_Representation;
127 -------------------------
128 -- Expand_Assign_Array --
129 -------------------------
131 -- There are two issues here. First, do we let Gigi do a block move, or
132 -- do we expand out into a loop? Second, we need to set the two flags
133 -- Forwards_OK and Backwards_OK which show whether the block move (or
134 -- corresponding loops) can be legitimately done in a forwards (low to
135 -- high) or backwards (high to low) manner.
137 procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id) is
138 Loc : constant Source_Ptr := Sloc (N);
140 Lhs : constant Node_Id := Name (N);
142 Act_Lhs : constant Node_Id := Get_Referenced_Object (Lhs);
143 Act_Rhs : Node_Id := Get_Referenced_Object (Rhs);
145 L_Type : constant Entity_Id :=
146 Underlying_Type (Get_Actual_Subtype (Act_Lhs));
147 R_Type : Entity_Id :=
148 Underlying_Type (Get_Actual_Subtype (Act_Rhs));
150 L_Slice : constant Boolean := Nkind (Act_Lhs) = N_Slice;
151 R_Slice : constant Boolean := Nkind (Act_Rhs) = N_Slice;
153 Crep : constant Boolean := Change_Of_Representation (N);
158 Ndim : constant Pos := Number_Dimensions (L_Type);
160 Loop_Required : Boolean := False;
161 -- This switch is set to True if the array move must be done using
162 -- an explicit front end generated loop.
164 procedure Apply_Dereference (Arg : in out Node_Id);
165 -- If the argument is an access to an array, and the assignment is
166 -- converted into a procedure call, apply explicit dereference.
168 function Has_Address_Clause (Exp : Node_Id) return Boolean;
169 -- Test if Exp is a reference to an array whose declaration has
170 -- an address clause, or it is a slice of such an array.
172 function Is_Formal_Array (Exp : Node_Id) return Boolean;
173 -- Test if Exp is a reference to an array which is either a formal
174 -- parameter or a slice of a formal parameter. These are the cases
175 -- where hidden aliasing can occur.
177 function Is_Non_Local_Array (Exp : Node_Id) return Boolean;
178 -- Determine if Exp is a reference to an array variable which is other
179 -- than an object defined in the current scope, or a slice of such
180 -- an object. Such objects can be aliased to parameters (unlike local
181 -- array references).
183 -----------------------
184 -- Apply_Dereference --
185 -----------------------
187 procedure Apply_Dereference (Arg : in out Node_Id) is
188 Typ : constant Entity_Id := Etype (Arg);
190 if Is_Access_Type (Typ) then
191 Rewrite (Arg, Make_Explicit_Dereference (Loc,
192 Prefix => Relocate_Node (Arg)));
193 Analyze_And_Resolve (Arg, Designated_Type (Typ));
195 end Apply_Dereference;
197 ------------------------
198 -- Has_Address_Clause --
199 ------------------------
201 function Has_Address_Clause (Exp : Node_Id) return Boolean is
204 (Is_Entity_Name (Exp) and then
205 Present (Address_Clause (Entity (Exp))))
207 (Nkind (Exp) = N_Slice and then Has_Address_Clause (Prefix (Exp)));
208 end Has_Address_Clause;
210 ---------------------
211 -- Is_Formal_Array --
212 ---------------------
214 function Is_Formal_Array (Exp : Node_Id) return Boolean is
217 (Is_Entity_Name (Exp) and then Is_Formal (Entity (Exp)))
219 (Nkind (Exp) = N_Slice and then Is_Formal_Array (Prefix (Exp)));
222 ------------------------
223 -- Is_Non_Local_Array --
224 ------------------------
226 function Is_Non_Local_Array (Exp : Node_Id) return Boolean is
228 return (Is_Entity_Name (Exp)
229 and then Scope (Entity (Exp)) /= Current_Scope)
230 or else (Nkind (Exp) = N_Slice
231 and then Is_Non_Local_Array (Prefix (Exp)));
232 end Is_Non_Local_Array;
234 -- Determine if Lhs, Rhs are formal arrays or nonlocal arrays
236 Lhs_Formal : constant Boolean := Is_Formal_Array (Act_Lhs);
237 Rhs_Formal : constant Boolean := Is_Formal_Array (Act_Rhs);
239 Lhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Lhs);
240 Rhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Rhs);
242 -- Start of processing for Expand_Assign_Array
245 -- Deal with length check, note that the length check is done with
246 -- respect to the right hand side as given, not a possible underlying
247 -- renamed object, since this would generate incorrect extra checks.
249 Apply_Length_Check (Rhs, L_Type);
251 -- We start by assuming that the move can be done in either
252 -- direction, i.e. that the two sides are completely disjoint.
254 Set_Forwards_OK (N, True);
255 Set_Backwards_OK (N, True);
257 -- Normally it is only the slice case that can lead to overlap,
258 -- and explicit checks for slices are made below. But there is
259 -- one case where the slice can be implicit and invisible to us
260 -- and that is the case where we have a one dimensional array,
261 -- and either both operands are parameters, or one is a parameter
262 -- and the other is a global variable. In this case the parameter
263 -- could be a slice that overlaps with the other parameter.
265 -- Check for the case of slices requiring an explicit loop. Normally
266 -- it is only the explicit slice cases that bother us, but in the
267 -- case of one dimensional arrays, parameters can be slices that
268 -- are passed by reference, so we can have aliasing for assignments
269 -- from one parameter to another, or assignments between parameters
270 -- and nonlocal variables. However, if the array subtype is a
271 -- constrained first subtype in the parameter case, then we don't
272 -- have to worry about overlap, since slice assignments aren't
273 -- possible (other than for a slice denoting the whole array).
275 -- Note: overlap is never possible if there is a change of
276 -- representation, so we can exclude this case.
281 ((Lhs_Formal and Rhs_Formal)
283 (Lhs_Formal and Rhs_Non_Local_Var)
285 (Rhs_Formal and Lhs_Non_Local_Var))
287 (not Is_Constrained (Etype (Lhs))
288 or else not Is_First_Subtype (Etype (Lhs)))
290 -- In the case of compiling for the Java Virtual Machine,
291 -- slices are always passed by making a copy, so we don't
292 -- have to worry about overlap. We also want to prevent
293 -- generation of "<" comparisons for array addresses,
294 -- since that's a meaningless operation on the JVM.
298 Set_Forwards_OK (N, False);
299 Set_Backwards_OK (N, False);
301 -- Note: the bit-packed case is not worrisome here, since if
302 -- we have a slice passed as a parameter, it is always aligned
303 -- on a byte boundary, and if there are no explicit slices, the
304 -- assignment can be performed directly.
307 -- We certainly must use a loop for change of representation
308 -- and also we use the operand of the conversion on the right
309 -- hand side as the effective right hand side (the component
310 -- types must match in this situation).
313 Act_Rhs := Get_Referenced_Object (Rhs);
314 R_Type := Get_Actual_Subtype (Act_Rhs);
315 Loop_Required := True;
317 -- We require a loop if the left side is possibly bit unaligned
319 elsif Possible_Bit_Aligned_Component (Lhs)
321 Possible_Bit_Aligned_Component (Rhs)
323 Loop_Required := True;
325 -- Arrays with controlled components are expanded into a loop
326 -- to force calls to adjust at the component level.
328 elsif Has_Controlled_Component (L_Type) then
329 Loop_Required := True;
331 -- Case where no slice is involved
333 elsif not L_Slice and not R_Slice then
335 -- The following code deals with the case of unconstrained bit
336 -- packed arrays. The problem is that the template for such
337 -- arrays contains the bounds of the actual source level array,
339 -- But the copy of an entire array requires the bounds of the
340 -- underlying array. It would be nice if the back end could take
341 -- care of this, but right now it does not know how, so if we
342 -- have such a type, then we expand out into a loop, which is
343 -- inefficient but works correctly. If we don't do this, we
344 -- get the wrong length computed for the array to be moved.
345 -- The two cases we need to worry about are:
347 -- Explicit deference of an unconstrained packed array type as
348 -- in the following example:
351 -- type BITS is array(INTEGER range <>) of BOOLEAN;
352 -- pragma PACK(BITS);
353 -- type A is access BITS;
356 -- P1 := new BITS (1 .. 65_535);
357 -- P2 := new BITS (1 .. 65_535);
361 -- A formal parameter reference with an unconstrained bit
362 -- array type is the other case we need to worry about (here
363 -- we assume the same BITS type declared above:
365 -- procedure Write_All (File : out BITS; Contents : in BITS);
367 -- File.Storage := Contents;
370 -- We expand to a loop in either of these two cases.
372 -- Question for future thought. Another potentially more efficient
373 -- approach would be to create the actual subtype, and then do an
374 -- unchecked conversion to this actual subtype ???
376 Check_Unconstrained_Bit_Packed_Array : declare
378 function Is_UBPA_Reference (Opnd : Node_Id) return Boolean;
379 -- Function to perform required test for the first case,
380 -- above (dereference of an unconstrained bit packed array)
382 -----------------------
383 -- Is_UBPA_Reference --
384 -----------------------
386 function Is_UBPA_Reference (Opnd : Node_Id) return Boolean is
387 Typ : constant Entity_Id := Underlying_Type (Etype (Opnd));
389 Des_Type : Entity_Id;
392 if Present (Packed_Array_Type (Typ))
393 and then Is_Array_Type (Packed_Array_Type (Typ))
394 and then not Is_Constrained (Packed_Array_Type (Typ))
398 elsif Nkind (Opnd) = N_Explicit_Dereference then
399 P_Type := Underlying_Type (Etype (Prefix (Opnd)));
401 if not Is_Access_Type (P_Type) then
405 Des_Type := Designated_Type (P_Type);
407 Is_Bit_Packed_Array (Des_Type)
408 and then not Is_Constrained (Des_Type);
414 end Is_UBPA_Reference;
416 -- Start of processing for Check_Unconstrained_Bit_Packed_Array
419 if Is_UBPA_Reference (Lhs)
421 Is_UBPA_Reference (Rhs)
423 Loop_Required := True;
425 -- Here if we do not have the case of a reference to a bit
426 -- packed unconstrained array case. In this case gigi can
427 -- most certainly handle the assignment if a forwards move
430 -- (could it handle the backwards case also???)
432 elsif Forwards_OK (N) then
435 end Check_Unconstrained_Bit_Packed_Array;
437 -- Gigi can always handle the assignment if the right side is a string
438 -- literal (note that overlap is definitely impossible in this case).
439 -- If the type is packed, a string literal is always converted into a
440 -- aggregate, except in the case of a null slice, for which no aggregate
441 -- can be written. In that case, rewrite the assignment as a null
442 -- statement, a length check has already been emitted to verify that
443 -- the range of the left-hand side is empty.
445 -- Note that this code is not executed if we had an assignment of
446 -- a string literal to a non-bit aligned component of a record, a
447 -- case which cannot be handled by the backend
449 elsif Nkind (Rhs) = N_String_Literal then
450 if String_Length (Strval (Rhs)) = 0
451 and then Is_Bit_Packed_Array (L_Type)
453 Rewrite (N, Make_Null_Statement (Loc));
459 -- If either operand is bit packed, then we need a loop, since we
460 -- can't be sure that the slice is byte aligned. Similarly, if either
461 -- operand is a possibly unaligned slice, then we need a loop (since
462 -- gigi cannot handle unaligned slices).
464 elsif Is_Bit_Packed_Array (L_Type)
465 or else Is_Bit_Packed_Array (R_Type)
466 or else Is_Possibly_Unaligned_Slice (Lhs)
467 or else Is_Possibly_Unaligned_Slice (Rhs)
469 Loop_Required := True;
471 -- If we are not bit-packed, and we have only one slice, then no
472 -- overlap is possible except in the parameter case, so we can let
473 -- gigi handle things.
475 elsif not (L_Slice and R_Slice) then
476 if Forwards_OK (N) then
481 -- If the right-hand side is a string literal, introduce a temporary
482 -- for it, for use in the generated loop that will follow.
484 if Nkind (Rhs) = N_String_Literal then
486 Temp : constant Entity_Id :=
487 Make_Defining_Identifier (Loc, Name_T);
492 Make_Object_Declaration (Loc,
493 Defining_Identifier => Temp,
494 Object_Definition => New_Occurrence_Of (L_Type, Loc),
495 Expression => Relocate_Node (Rhs));
497 Insert_Action (N, Decl);
498 Rewrite (Rhs, New_Occurrence_Of (Temp, Loc));
499 R_Type := Etype (Temp);
503 -- Come here to complete the analysis
505 -- Loop_Required: Set to True if we know that a loop is required
506 -- regardless of overlap considerations.
508 -- Forwards_OK: Set to False if we already know that a forwards
509 -- move is not safe, else set to True.
511 -- Backwards_OK: Set to False if we already know that a backwards
512 -- move is not safe, else set to True
514 -- Our task at this stage is to complete the overlap analysis, which
515 -- can result in possibly setting Forwards_OK or Backwards_OK to
516 -- False, and then generating the final code, either by deciding
517 -- that it is OK after all to let Gigi handle it, or by generating
518 -- appropriate code in the front end.
521 L_Index_Typ : constant Node_Id := Etype (First_Index (L_Type));
522 R_Index_Typ : constant Node_Id := Etype (First_Index (R_Type));
524 Left_Lo : constant Node_Id := Type_Low_Bound (L_Index_Typ);
525 Left_Hi : constant Node_Id := Type_High_Bound (L_Index_Typ);
526 Right_Lo : constant Node_Id := Type_Low_Bound (R_Index_Typ);
527 Right_Hi : constant Node_Id := Type_High_Bound (R_Index_Typ);
529 Act_L_Array : Node_Id;
530 Act_R_Array : Node_Id;
536 Cresult : Compare_Result;
539 -- Get the expressions for the arrays. If we are dealing with a
540 -- private type, then convert to the underlying type. We can do
541 -- direct assignments to an array that is a private type, but
542 -- we cannot assign to elements of the array without this extra
543 -- unchecked conversion.
545 if Nkind (Act_Lhs) = N_Slice then
546 Larray := Prefix (Act_Lhs);
550 if Is_Private_Type (Etype (Larray)) then
553 (Underlying_Type (Etype (Larray)), Larray);
557 if Nkind (Act_Rhs) = N_Slice then
558 Rarray := Prefix (Act_Rhs);
562 if Is_Private_Type (Etype (Rarray)) then
565 (Underlying_Type (Etype (Rarray)), Rarray);
569 -- If both sides are slices, we must figure out whether
570 -- it is safe to do the move in one direction or the other
571 -- It is always safe if there is a change of representation
572 -- since obviously two arrays with different representations
573 -- cannot possibly overlap.
575 if (not Crep) and L_Slice and R_Slice then
576 Act_L_Array := Get_Referenced_Object (Prefix (Act_Lhs));
577 Act_R_Array := Get_Referenced_Object (Prefix (Act_Rhs));
579 -- If both left and right hand arrays are entity names, and
580 -- refer to different entities, then we know that the move
581 -- is safe (the two storage areas are completely disjoint).
583 if Is_Entity_Name (Act_L_Array)
584 and then Is_Entity_Name (Act_R_Array)
585 and then Entity (Act_L_Array) /= Entity (Act_R_Array)
589 -- Otherwise, we assume the worst, which is that the two
590 -- arrays are the same array. There is no need to check if
591 -- we know that is the case, because if we don't know it,
592 -- we still have to assume it!
594 -- Generally if the same array is involved, then we have
595 -- an overlapping case. We will have to really assume the
596 -- worst (i.e. set neither of the OK flags) unless we can
597 -- determine the lower or upper bounds at compile time and
601 Cresult := Compile_Time_Compare (Left_Lo, Right_Lo);
603 if Cresult = Unknown then
604 Cresult := Compile_Time_Compare (Left_Hi, Right_Hi);
608 when LT | LE | EQ => Set_Backwards_OK (N, False);
609 when GT | GE => Set_Forwards_OK (N, False);
610 when NE | Unknown => Set_Backwards_OK (N, False);
611 Set_Forwards_OK (N, False);
616 -- If after that analysis, Forwards_OK is still True, and
617 -- Loop_Required is False, meaning that we have not discovered
618 -- some non-overlap reason for requiring a loop, then we can
619 -- still let gigi handle it.
621 if not Loop_Required then
622 if Forwards_OK (N) then
627 -- Here is where a memmove would be appropriate ???
631 -- At this stage we have to generate an explicit loop, and
632 -- we have the following cases:
634 -- Forwards_OK = True
636 -- Rnn : right_index := right_index'First;
637 -- for Lnn in left-index loop
638 -- left (Lnn) := right (Rnn);
639 -- Rnn := right_index'Succ (Rnn);
642 -- Note: the above code MUST be analyzed with checks off,
643 -- because otherwise the Succ could overflow. But in any
644 -- case this is more efficient!
646 -- Forwards_OK = False, Backwards_OK = True
648 -- Rnn : right_index := right_index'Last;
649 -- for Lnn in reverse left-index loop
650 -- left (Lnn) := right (Rnn);
651 -- Rnn := right_index'Pred (Rnn);
654 -- Note: the above code MUST be analyzed with checks off,
655 -- because otherwise the Pred could overflow. But in any
656 -- case this is more efficient!
658 -- Forwards_OK = Backwards_OK = False
660 -- This only happens if we have the same array on each side. It is
661 -- possible to create situations using overlays that violate this,
662 -- but we simply do not promise to get this "right" in this case.
664 -- There are two possible subcases. If the No_Implicit_Conditionals
665 -- restriction is set, then we generate the following code:
668 -- T : constant <operand-type> := rhs;
673 -- If implicit conditionals are permitted, then we generate:
675 -- if Left_Lo <= Right_Lo then
676 -- <code for Forwards_OK = True above>
678 -- <code for Backwards_OK = True above>
681 -- Cases where either Forwards_OK or Backwards_OK is true
683 if Forwards_OK (N) or else Backwards_OK (N) then
684 if Controlled_Type (Component_Type (L_Type))
685 and then Base_Type (L_Type) = Base_Type (R_Type)
687 and then not No_Ctrl_Actions (N)
690 Proc : constant Entity_Id :=
691 TSS (Base_Type (L_Type), TSS_Slice_Assign);
695 Apply_Dereference (Larray);
696 Apply_Dereference (Rarray);
697 Actuals := New_List (
698 Duplicate_Subexpr (Larray, Name_Req => True),
699 Duplicate_Subexpr (Rarray, Name_Req => True),
700 Duplicate_Subexpr (Left_Lo, Name_Req => True),
701 Duplicate_Subexpr (Left_Hi, Name_Req => True),
702 Duplicate_Subexpr (Right_Lo, Name_Req => True),
703 Duplicate_Subexpr (Right_Hi, Name_Req => True));
707 Boolean_Literals (not Forwards_OK (N)), Loc));
710 Make_Procedure_Call_Statement (Loc,
711 Name => New_Reference_To (Proc, Loc),
712 Parameter_Associations => Actuals));
717 Expand_Assign_Array_Loop
718 (N, Larray, Rarray, L_Type, R_Type, Ndim,
719 Rev => not Forwards_OK (N)));
722 -- Case of both are false with No_Implicit_Conditionals
724 elsif Restriction_Active (No_Implicit_Conditionals) then
726 T : constant Entity_Id :=
727 Make_Defining_Identifier (Loc, Chars => Name_T);
731 Make_Block_Statement (Loc,
732 Declarations => New_List (
733 Make_Object_Declaration (Loc,
734 Defining_Identifier => T,
735 Constant_Present => True,
737 New_Occurrence_Of (Etype (Rhs), Loc),
738 Expression => Relocate_Node (Rhs))),
740 Handled_Statement_Sequence =>
741 Make_Handled_Sequence_Of_Statements (Loc,
742 Statements => New_List (
743 Make_Assignment_Statement (Loc,
744 Name => Relocate_Node (Lhs),
745 Expression => New_Occurrence_Of (T, Loc))))));
748 -- Case of both are false with implicit conditionals allowed
751 -- Before we generate this code, we must ensure that the
752 -- left and right side array types are defined. They may
753 -- be itypes, and we cannot let them be defined inside the
754 -- if, since the first use in the then may not be executed.
756 Ensure_Defined (L_Type, N);
757 Ensure_Defined (R_Type, N);
759 -- We normally compare addresses to find out which way round
760 -- to do the loop, since this is realiable, and handles the
761 -- cases of parameters, conversions etc. But we can't do that
762 -- in the bit packed case or the Java VM case, because addresses
765 if not Is_Bit_Packed_Array (L_Type) and then not Java_VM then
769 Unchecked_Convert_To (RTE (RE_Integer_Address),
770 Make_Attribute_Reference (Loc,
772 Make_Indexed_Component (Loc,
774 Duplicate_Subexpr_Move_Checks (Larray, True),
775 Expressions => New_List (
776 Make_Attribute_Reference (Loc,
780 Attribute_Name => Name_First))),
781 Attribute_Name => Name_Address)),
784 Unchecked_Convert_To (RTE (RE_Integer_Address),
785 Make_Attribute_Reference (Loc,
787 Make_Indexed_Component (Loc,
789 Duplicate_Subexpr_Move_Checks (Rarray, True),
790 Expressions => New_List (
791 Make_Attribute_Reference (Loc,
795 Attribute_Name => Name_First))),
796 Attribute_Name => Name_Address)));
798 -- For the bit packed and Java VM cases we use the bounds.
799 -- That's OK, because we don't have to worry about parameters,
800 -- since they cannot cause overlap. Perhaps we should worry
801 -- about weird slice conversions ???
804 -- Copy the bounds and reset the Analyzed flag, because the
805 -- bounds of the index type itself may be universal, and must
806 -- must be reaanalyzed to acquire the proper type for Gigi.
808 Cleft_Lo := New_Copy_Tree (Left_Lo);
809 Cright_Lo := New_Copy_Tree (Right_Lo);
810 Set_Analyzed (Cleft_Lo, False);
811 Set_Analyzed (Cright_Lo, False);
815 Left_Opnd => Cleft_Lo,
816 Right_Opnd => Cright_Lo);
819 if Controlled_Type (Component_Type (L_Type))
820 and then Base_Type (L_Type) = Base_Type (R_Type)
822 and then not No_Ctrl_Actions (N)
825 -- Call TSS procedure for array assignment, passing the
826 -- the explicit bounds of right- and left-hand side.
829 Proc : constant Node_Id :=
830 TSS (Base_Type (L_Type), TSS_Slice_Assign);
834 Apply_Dereference (Larray);
835 Apply_Dereference (Rarray);
836 Actuals := New_List (
837 Duplicate_Subexpr (Larray, Name_Req => True),
838 Duplicate_Subexpr (Rarray, Name_Req => True),
839 Duplicate_Subexpr (Left_Lo, Name_Req => True),
840 Duplicate_Subexpr (Left_Hi, Name_Req => True),
841 Duplicate_Subexpr (Right_Lo, Name_Req => True),
842 Duplicate_Subexpr (Right_Hi, Name_Req => True));
843 Append_To (Actuals, Condition);
846 Make_Procedure_Call_Statement (Loc,
847 Name => New_Reference_To (Proc, Loc),
848 Parameter_Associations => Actuals));
853 Make_Implicit_If_Statement (N,
854 Condition => Condition,
856 Then_Statements => New_List (
857 Expand_Assign_Array_Loop
858 (N, Larray, Rarray, L_Type, R_Type, Ndim,
861 Else_Statements => New_List (
862 Expand_Assign_Array_Loop
863 (N, Larray, Rarray, L_Type, R_Type, Ndim,
868 Analyze (N, Suppress => All_Checks);
872 when RE_Not_Available =>
874 end Expand_Assign_Array;
876 ------------------------------
877 -- Expand_Assign_Array_Loop --
878 ------------------------------
880 -- The following is an example of the loop generated for the case of
881 -- a two-dimensional array:
886 -- for L1b in 1 .. 100 loop
890 -- for L3b in 1 .. 100 loop
891 -- vm1 (L1b, L3b) := vm2 (R2b, R4b);
892 -- R4b := Tm1X2'succ(R4b);
895 -- R2b := Tm1X1'succ(R2b);
899 -- Here Rev is False, and Tm1Xn are the subscript types for the right
900 -- hand side. The declarations of R2b and R4b are inserted before the
901 -- original assignment statement.
903 function Expand_Assign_Array_Loop
910 Rev : Boolean) return Node_Id
912 Loc : constant Source_Ptr := Sloc (N);
914 Lnn : array (1 .. Ndim) of Entity_Id;
915 Rnn : array (1 .. Ndim) of Entity_Id;
916 -- Entities used as subscripts on left and right sides
918 L_Index_Type : array (1 .. Ndim) of Entity_Id;
919 R_Index_Type : array (1 .. Ndim) of Entity_Id;
920 -- Left and right index types
932 F_Or_L := Name_First;
936 -- Setup index types and subscript entities
943 L_Index := First_Index (L_Type);
944 R_Index := First_Index (R_Type);
946 for J in 1 .. Ndim loop
948 Make_Defining_Identifier (Loc,
949 Chars => New_Internal_Name ('L'));
952 Make_Defining_Identifier (Loc,
953 Chars => New_Internal_Name ('R'));
955 L_Index_Type (J) := Etype (L_Index);
956 R_Index_Type (J) := Etype (R_Index);
958 Next_Index (L_Index);
959 Next_Index (R_Index);
963 -- Now construct the assignment statement
966 ExprL : constant List_Id := New_List;
967 ExprR : constant List_Id := New_List;
970 for J in 1 .. Ndim loop
971 Append_To (ExprL, New_Occurrence_Of (Lnn (J), Loc));
972 Append_To (ExprR, New_Occurrence_Of (Rnn (J), Loc));
976 Make_Assignment_Statement (Loc,
978 Make_Indexed_Component (Loc,
979 Prefix => Duplicate_Subexpr (Larray, Name_Req => True),
980 Expressions => ExprL),
982 Make_Indexed_Component (Loc,
983 Prefix => Duplicate_Subexpr (Rarray, Name_Req => True),
984 Expressions => ExprR));
986 -- Propagate the No_Ctrl_Actions flag to individual assignments
988 Set_No_Ctrl_Actions (Assign, No_Ctrl_Actions (N));
991 -- Now construct the loop from the inside out, with the last subscript
992 -- varying most rapidly. Note that Assign is first the raw assignment
993 -- statement, and then subsequently the loop that wraps it up.
995 for J in reverse 1 .. Ndim loop
997 Make_Block_Statement (Loc,
998 Declarations => New_List (
999 Make_Object_Declaration (Loc,
1000 Defining_Identifier => Rnn (J),
1001 Object_Definition =>
1002 New_Occurrence_Of (R_Index_Type (J), Loc),
1004 Make_Attribute_Reference (Loc,
1005 Prefix => New_Occurrence_Of (R_Index_Type (J), Loc),
1006 Attribute_Name => F_Or_L))),
1008 Handled_Statement_Sequence =>
1009 Make_Handled_Sequence_Of_Statements (Loc,
1010 Statements => New_List (
1011 Make_Implicit_Loop_Statement (N,
1013 Make_Iteration_Scheme (Loc,
1014 Loop_Parameter_Specification =>
1015 Make_Loop_Parameter_Specification (Loc,
1016 Defining_Identifier => Lnn (J),
1017 Reverse_Present => Rev,
1018 Discrete_Subtype_Definition =>
1019 New_Reference_To (L_Index_Type (J), Loc))),
1021 Statements => New_List (
1024 Make_Assignment_Statement (Loc,
1025 Name => New_Occurrence_Of (Rnn (J), Loc),
1027 Make_Attribute_Reference (Loc,
1029 New_Occurrence_Of (R_Index_Type (J), Loc),
1030 Attribute_Name => S_Or_P,
1031 Expressions => New_List (
1032 New_Occurrence_Of (Rnn (J), Loc)))))))));
1036 end Expand_Assign_Array_Loop;
1038 --------------------------
1039 -- Expand_Assign_Record --
1040 --------------------------
1042 -- The only processing required is in the change of representation
1043 -- case, where we must expand the assignment to a series of field
1044 -- by field assignments.
1046 procedure Expand_Assign_Record (N : Node_Id) is
1047 Lhs : constant Node_Id := Name (N);
1048 Rhs : Node_Id := Expression (N);
1051 -- If change of representation, then extract the real right hand
1052 -- side from the type conversion, and proceed with component-wise
1053 -- assignment, since the two types are not the same as far as the
1054 -- back end is concerned.
1056 if Change_Of_Representation (N) then
1057 Rhs := Expression (Rhs);
1059 -- If this may be a case of a large bit aligned component, then
1060 -- proceed with component-wise assignment, to avoid possible
1061 -- clobbering of other components sharing bits in the first or
1062 -- last byte of the component to be assigned.
1064 elsif Possible_Bit_Aligned_Component (Lhs)
1066 Possible_Bit_Aligned_Component (Rhs)
1070 -- If neither condition met, then nothing special to do, the back end
1071 -- can handle assignment of the entire component as a single entity.
1077 -- At this stage we know that we must do a component wise assignment
1080 Loc : constant Source_Ptr := Sloc (N);
1081 R_Typ : constant Entity_Id := Base_Type (Etype (Rhs));
1082 L_Typ : constant Entity_Id := Base_Type (Etype (Lhs));
1083 Decl : constant Node_Id := Declaration_Node (R_Typ);
1087 function Find_Component
1089 Comp : Entity_Id) return Entity_Id;
1090 -- Find the component with the given name in the underlying record
1091 -- declaration for Typ. We need to use the actual entity because
1092 -- the type may be private and resolution by identifier alone would
1095 function Make_Component_List_Assign (CL : Node_Id) return List_Id;
1096 -- Returns a sequence of statements to assign the components that
1097 -- are referenced in the given component list.
1099 function Make_Field_Assign (C : Entity_Id) return Node_Id;
1100 -- Given C, the entity for a discriminant or component, build
1101 -- an assignment for the corresponding field values.
1103 function Make_Field_Assigns (CI : List_Id) return List_Id;
1104 -- Given CI, a component items list, construct series of statements
1105 -- for fieldwise assignment of the corresponding components.
1107 --------------------
1108 -- Find_Component --
1109 --------------------
1111 function Find_Component
1113 Comp : Entity_Id) return Entity_Id
1115 Utyp : constant Entity_Id := Underlying_Type (Typ);
1119 C := First_Entity (Utyp);
1121 while Present (C) loop
1122 if Chars (C) = Chars (Comp) then
1128 raise Program_Error;
1131 --------------------------------
1132 -- Make_Component_List_Assign --
1133 --------------------------------
1135 function Make_Component_List_Assign (CL : Node_Id) return List_Id is
1136 CI : constant List_Id := Component_Items (CL);
1137 VP : constant Node_Id := Variant_Part (CL);
1146 Result := Make_Field_Assigns (CI);
1148 if Present (VP) then
1150 V := First_Non_Pragma (Variants (VP));
1152 while Present (V) loop
1155 DC := First (Discrete_Choices (V));
1156 while Present (DC) loop
1157 Append_To (DCH, New_Copy_Tree (DC));
1162 Make_Case_Statement_Alternative (Loc,
1163 Discrete_Choices => DCH,
1165 Make_Component_List_Assign (Component_List (V))));
1166 Next_Non_Pragma (V);
1170 Make_Case_Statement (Loc,
1172 Make_Selected_Component (Loc,
1173 Prefix => Duplicate_Subexpr (Rhs),
1175 Make_Identifier (Loc, Chars (Name (VP)))),
1176 Alternatives => Alts));
1181 end Make_Component_List_Assign;
1183 -----------------------
1184 -- Make_Field_Assign --
1185 -----------------------
1187 function Make_Field_Assign (C : Entity_Id) return Node_Id is
1192 Make_Assignment_Statement (Loc,
1194 Make_Selected_Component (Loc,
1195 Prefix => Duplicate_Subexpr (Lhs),
1197 New_Occurrence_Of (Find_Component (L_Typ, C), Loc)),
1199 Make_Selected_Component (Loc,
1200 Prefix => Duplicate_Subexpr (Rhs),
1201 Selector_Name => New_Occurrence_Of (C, Loc)));
1203 -- Set Assignment_OK, so discriminants can be assigned
1205 Set_Assignment_OK (Name (A), True);
1207 end Make_Field_Assign;
1209 ------------------------
1210 -- Make_Field_Assigns --
1211 ------------------------
1213 function Make_Field_Assigns (CI : List_Id) return List_Id is
1221 while Present (Item) loop
1222 if Nkind (Item) = N_Component_Declaration then
1224 (Result, Make_Field_Assign (Defining_Identifier (Item)));
1231 end Make_Field_Assigns;
1233 -- Start of processing for Expand_Assign_Record
1236 -- Note that we use the base types for this processing. This results
1237 -- in some extra work in the constrained case, but the change of
1238 -- representation case is so unusual that it is not worth the effort.
1240 -- First copy the discriminants. This is done unconditionally. It
1241 -- is required in the unconstrained left side case, and also in the
1242 -- case where this assignment was constructed during the expansion
1243 -- of a type conversion (since initialization of discriminants is
1244 -- suppressed in this case). It is unnecessary but harmless in
1247 if Has_Discriminants (L_Typ) then
1248 F := First_Discriminant (R_Typ);
1249 while Present (F) loop
1250 Insert_Action (N, Make_Field_Assign (F));
1251 Next_Discriminant (F);
1255 -- We know the underlying type is a record, but its current view
1256 -- may be private. We must retrieve the usable record declaration.
1258 if Nkind (Decl) = N_Private_Type_Declaration
1259 and then Present (Full_View (R_Typ))
1261 RDef := Type_Definition (Declaration_Node (Full_View (R_Typ)));
1263 RDef := Type_Definition (Decl);
1266 if Nkind (RDef) = N_Record_Definition
1267 and then Present (Component_List (RDef))
1270 (N, Make_Component_List_Assign (Component_List (RDef)));
1272 Rewrite (N, Make_Null_Statement (Loc));
1276 end Expand_Assign_Record;
1278 -----------------------------------
1279 -- Expand_N_Assignment_Statement --
1280 -----------------------------------
1282 -- For array types, deal with slice assignments and setting the flags
1283 -- to indicate if it can be statically determined which direction the
1284 -- move should go in. Also deal with generating range/length checks.
1286 procedure Expand_N_Assignment_Statement (N : Node_Id) is
1287 Loc : constant Source_Ptr := Sloc (N);
1288 Lhs : constant Node_Id := Name (N);
1289 Rhs : constant Node_Id := Expression (N);
1290 Typ : constant Entity_Id := Underlying_Type (Etype (Lhs));
1294 -- First deal with generation of range check if required. For now
1295 -- we do this only for discrete types.
1297 if Do_Range_Check (Rhs)
1298 and then Is_Discrete_Type (Typ)
1300 Set_Do_Range_Check (Rhs, False);
1301 Generate_Range_Check (Rhs, Typ, CE_Range_Check_Failed);
1304 -- Check for a special case where a high level transformation is
1305 -- required. If we have either of:
1310 -- where P is a reference to a bit packed array, then we have to unwind
1311 -- the assignment. The exact meaning of being a reference to a bit
1312 -- packed array is as follows:
1314 -- An indexed component whose prefix is a bit packed array is a
1315 -- reference to a bit packed array.
1317 -- An indexed component or selected component whose prefix is a
1318 -- reference to a bit packed array is itself a reference ot a
1319 -- bit packed array.
1321 -- The required transformation is
1323 -- Tnn : prefix_type := P;
1324 -- Tnn.field := rhs;
1329 -- Tnn : prefix_type := P;
1330 -- Tnn (subscr) := rhs;
1333 -- Since P is going to be evaluated more than once, any subscripts
1334 -- in P must have their evaluation forced.
1336 if (Nkind (Lhs) = N_Indexed_Component
1338 Nkind (Lhs) = N_Selected_Component)
1339 and then Is_Ref_To_Bit_Packed_Array (Prefix (Lhs))
1342 BPAR_Expr : constant Node_Id := Relocate_Node (Prefix (Lhs));
1343 BPAR_Typ : constant Entity_Id := Etype (BPAR_Expr);
1344 Tnn : constant Entity_Id :=
1345 Make_Defining_Identifier (Loc,
1346 Chars => New_Internal_Name ('T'));
1349 -- Insert the post assignment first, because we want to copy
1350 -- the BPAR_Expr tree before it gets analyzed in the context
1351 -- of the pre assignment. Note that we do not analyze the
1352 -- post assignment yet (we cannot till we have completed the
1353 -- analysis of the pre assignment). As usual, the analysis
1354 -- of this post assignment will happen on its own when we
1355 -- "run into" it after finishing the current assignment.
1358 Make_Assignment_Statement (Loc,
1359 Name => New_Copy_Tree (BPAR_Expr),
1360 Expression => New_Occurrence_Of (Tnn, Loc)));
1362 -- At this stage BPAR_Expr is a reference to a bit packed
1363 -- array where the reference was not expanded in the original
1364 -- tree, since it was on the left side of an assignment. But
1365 -- in the pre-assignment statement (the object definition),
1366 -- BPAR_Expr will end up on the right hand side, and must be
1367 -- reexpanded. To achieve this, we reset the analyzed flag
1368 -- of all selected and indexed components down to the actual
1369 -- indexed component for the packed array.
1373 Set_Analyzed (Exp, False);
1375 if Nkind (Exp) = N_Selected_Component
1377 Nkind (Exp) = N_Indexed_Component
1379 Exp := Prefix (Exp);
1385 -- Now we can insert and analyze the pre-assignment.
1387 -- If the right-hand side requires a transient scope, it has
1388 -- already been placed on the stack. However, the declaration is
1389 -- inserted in the tree outside of this scope, and must reflect
1390 -- the proper scope for its variable. This awkward bit is forced
1391 -- by the stricter scope discipline imposed by GCC 2.97.
1394 Uses_Transient_Scope : constant Boolean :=
1395 Scope_Is_Transient and then N = Node_To_Be_Wrapped;
1398 if Uses_Transient_Scope then
1399 New_Scope (Scope (Current_Scope));
1402 Insert_Before_And_Analyze (N,
1403 Make_Object_Declaration (Loc,
1404 Defining_Identifier => Tnn,
1405 Object_Definition => New_Occurrence_Of (BPAR_Typ, Loc),
1406 Expression => BPAR_Expr));
1408 if Uses_Transient_Scope then
1413 -- Now fix up the original assignment and continue processing
1415 Rewrite (Prefix (Lhs),
1416 New_Occurrence_Of (Tnn, Loc));
1418 -- We do not need to reanalyze that assignment, and we do not need
1419 -- to worry about references to the temporary, but we do need to
1420 -- make sure that the temporary is not marked as a true constant
1421 -- since we now have a generate assignment to it!
1423 Set_Is_True_Constant (Tnn, False);
1427 -- When we have the appropriate type of aggregate in the
1428 -- expression (it has been determined during analysis of the
1429 -- aggregate by setting the delay flag), let's perform in place
1430 -- assignment and thus avoid creating a temporay.
1432 if Is_Delayed_Aggregate (Rhs) then
1433 Convert_Aggr_In_Assignment (N);
1434 Rewrite (N, Make_Null_Statement (Loc));
1439 -- Apply discriminant check if required. If Lhs is an access type
1440 -- to a designated type with discriminants, we must always check.
1442 if Has_Discriminants (Etype (Lhs)) then
1444 -- Skip discriminant check if change of representation. Will be
1445 -- done when the change of representation is expanded out.
1447 if not Change_Of_Representation (N) then
1448 Apply_Discriminant_Check (Rhs, Etype (Lhs), Lhs);
1451 -- If the type is private without discriminants, and the full type
1452 -- has discriminants (necessarily with defaults) a check may still be
1453 -- necessary if the Lhs is aliased. The private determinants must be
1454 -- visible to build the discriminant constraints.
1456 -- Only an explicit dereference that comes from source indicates
1457 -- aliasing. Access to formals of protected operations and entries
1458 -- create dereferences but are not semantic aliasings.
1460 elsif Is_Private_Type (Etype (Lhs))
1461 and then Has_Discriminants (Typ)
1462 and then Nkind (Lhs) = N_Explicit_Dereference
1463 and then Comes_From_Source (Lhs)
1466 Lt : constant Entity_Id := Etype (Lhs);
1468 Set_Etype (Lhs, Typ);
1469 Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs));
1470 Apply_Discriminant_Check (Rhs, Typ, Lhs);
1471 Set_Etype (Lhs, Lt);
1474 -- If the Lhs has a private type with unknown discriminants, it
1475 -- may have a full view with discriminants, but those are nameable
1476 -- only in the underlying type, so convert the Rhs to it before
1477 -- potential checking.
1479 elsif Has_Unknown_Discriminants (Base_Type (Etype (Lhs)))
1480 and then Has_Discriminants (Typ)
1482 Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs));
1483 Apply_Discriminant_Check (Rhs, Typ, Lhs);
1485 -- In the access type case, we need the same discriminant check,
1486 -- and also range checks if we have an access to constrained array.
1488 elsif Is_Access_Type (Etype (Lhs))
1489 and then Is_Constrained (Designated_Type (Etype (Lhs)))
1491 if Has_Discriminants (Designated_Type (Etype (Lhs))) then
1493 -- Skip discriminant check if change of representation. Will be
1494 -- done when the change of representation is expanded out.
1496 if not Change_Of_Representation (N) then
1497 Apply_Discriminant_Check (Rhs, Etype (Lhs));
1500 elsif Is_Array_Type (Designated_Type (Etype (Lhs))) then
1501 Apply_Range_Check (Rhs, Etype (Lhs));
1503 if Is_Constrained (Etype (Lhs)) then
1504 Apply_Length_Check (Rhs, Etype (Lhs));
1507 if Nkind (Rhs) = N_Allocator then
1509 Target_Typ : constant Entity_Id := Etype (Expression (Rhs));
1510 C_Es : Check_Result;
1517 Etype (Designated_Type (Etype (Lhs))));
1529 -- Apply range check for access type case
1531 elsif Is_Access_Type (Etype (Lhs))
1532 and then Nkind (Rhs) = N_Allocator
1533 and then Nkind (Expression (Rhs)) = N_Qualified_Expression
1535 Analyze_And_Resolve (Expression (Rhs));
1537 (Expression (Rhs), Designated_Type (Etype (Lhs)));
1540 -- Ada 2005 (AI-231): Generate conversion to the null-excluding
1541 -- type to force the corresponding run-time check
1543 if Is_Access_Type (Typ)
1545 ((Is_Entity_Name (Lhs) and then Can_Never_Be_Null (Entity (Lhs)))
1546 or else Can_Never_Be_Null (Etype (Lhs)))
1548 Rewrite (Rhs, Convert_To (Etype (Lhs),
1549 Relocate_Node (Rhs)));
1550 Analyze_And_Resolve (Rhs, Etype (Lhs));
1553 -- If we are assigning an access type and the left side is an
1554 -- entity, then make sure that Is_Known_Non_Null properly
1555 -- reflects the state of the entity after the assignment
1557 if Is_Access_Type (Typ)
1558 and then Is_Entity_Name (Lhs)
1559 and then Known_Non_Null (Rhs)
1560 and then Safe_To_Capture_Value (N, Entity (Lhs))
1562 Set_Is_Known_Non_Null (Entity (Lhs), Known_Non_Null (Rhs));
1565 -- Case of assignment to a bit packed array element
1567 if Nkind (Lhs) = N_Indexed_Component
1568 and then Is_Bit_Packed_Array (Etype (Prefix (Lhs)))
1570 Expand_Bit_Packed_Element_Set (N);
1573 -- Case of tagged type assignment
1575 elsif Is_Tagged_Type (Typ)
1576 or else (Controlled_Type (Typ) and then not Is_Array_Type (Typ))
1578 Tagged_Case : declare
1579 L : List_Id := No_List;
1580 Expand_Ctrl_Actions : constant Boolean := not No_Ctrl_Actions (N);
1583 -- In the controlled case, we need to make sure that function
1584 -- calls are evaluated before finalizing the target. In all
1585 -- cases, it makes the expansion easier if the side-effects
1586 -- are removed first.
1588 Remove_Side_Effects (Lhs);
1589 Remove_Side_Effects (Rhs);
1591 -- Avoid recursion in the mechanism
1595 -- If dispatching assignment, we need to dispatch to _assign
1597 if Is_Class_Wide_Type (Typ)
1599 -- If the type is tagged, we may as well use the predefined
1600 -- primitive assignment. This avoids inlining a lot of code
1601 -- and in the class-wide case, the assignment is replaced by
1602 -- a dispatch call to _assign. Note that this cannot be done
1603 -- when discriminant checks are locally suppressed (as in
1604 -- extension aggregate expansions) because otherwise the
1605 -- discriminant check will be performed within the _assign
1608 or else (Is_Tagged_Type (Typ)
1609 and then Chars (Current_Scope) /= Name_uAssign
1610 and then Expand_Ctrl_Actions
1611 and then not Discriminant_Checks_Suppressed (Empty))
1613 -- Fetch the primitive op _assign and proper type to call
1614 -- it. Because of possible conflits between private and
1615 -- full view the proper type is fetched directly from the
1616 -- operation profile.
1619 Op : constant Entity_Id :=
1620 Find_Prim_Op (Typ, Name_uAssign);
1621 F_Typ : Entity_Id := Etype (First_Formal (Op));
1624 -- If the assignment is dispatching, make sure to use the
1625 -- ??? where is rest of this comment ???
1627 if Is_Class_Wide_Type (Typ) then
1628 F_Typ := Class_Wide_Type (F_Typ);
1632 Make_Procedure_Call_Statement (Loc,
1633 Name => New_Reference_To (Op, Loc),
1634 Parameter_Associations => New_List (
1635 Unchecked_Convert_To (F_Typ, Duplicate_Subexpr (Lhs)),
1636 Unchecked_Convert_To (F_Typ,
1637 Duplicate_Subexpr (Rhs)))));
1641 L := Make_Tag_Ctrl_Assignment (N);
1643 -- We can't afford to have destructive Finalization Actions
1644 -- in the Self assignment case, so if the target and the
1645 -- source are not obviously different, code is generated to
1646 -- avoid the self assignment case
1648 -- if lhs'address /= rhs'address then
1649 -- <code for controlled and/or tagged assignment>
1652 if not Statically_Different (Lhs, Rhs)
1653 and then Expand_Ctrl_Actions
1656 Make_Implicit_If_Statement (N,
1660 Make_Attribute_Reference (Loc,
1661 Prefix => Duplicate_Subexpr (Lhs),
1662 Attribute_Name => Name_Address),
1665 Make_Attribute_Reference (Loc,
1666 Prefix => Duplicate_Subexpr (Rhs),
1667 Attribute_Name => Name_Address)),
1669 Then_Statements => L));
1672 -- We need to set up an exception handler for implementing
1673 -- 7.6.1 (18). The remaining adjustments are tackled by the
1674 -- implementation of adjust for record_controllers (see
1677 -- This is skipped if we have no finalization
1679 if Expand_Ctrl_Actions
1680 and then not Restriction_Active (No_Finalization)
1683 Make_Block_Statement (Loc,
1684 Handled_Statement_Sequence =>
1685 Make_Handled_Sequence_Of_Statements (Loc,
1687 Exception_Handlers => New_List (
1688 Make_Exception_Handler (Loc,
1689 Exception_Choices =>
1690 New_List (Make_Others_Choice (Loc)),
1691 Statements => New_List (
1692 Make_Raise_Program_Error (Loc,
1694 PE_Finalize_Raised_Exception)
1700 Make_Block_Statement (Loc,
1701 Handled_Statement_Sequence =>
1702 Make_Handled_Sequence_Of_Statements (Loc, Statements => L)));
1704 -- If no restrictions on aborts, protect the whole assignement
1705 -- for controlled objects as per 9.8(11)
1707 if Controlled_Type (Typ)
1708 and then Expand_Ctrl_Actions
1709 and then Abort_Allowed
1712 Blk : constant Entity_Id :=
1713 New_Internal_Entity (
1714 E_Block, Current_Scope, Sloc (N), 'B');
1717 Set_Scope (Blk, Current_Scope);
1718 Set_Etype (Blk, Standard_Void_Type);
1719 Set_Identifier (N, New_Occurrence_Of (Blk, Sloc (N)));
1721 Prepend_To (L, Build_Runtime_Call (Loc, RE_Abort_Defer));
1722 Set_At_End_Proc (Handled_Statement_Sequence (N),
1723 New_Occurrence_Of (RTE (RE_Abort_Undefer_Direct), Loc));
1724 Expand_At_End_Handler
1725 (Handled_Statement_Sequence (N), Blk);
1735 elsif Is_Array_Type (Typ) then
1737 Actual_Rhs : Node_Id := Rhs;
1740 while Nkind (Actual_Rhs) = N_Type_Conversion
1742 Nkind (Actual_Rhs) = N_Qualified_Expression
1744 Actual_Rhs := Expression (Actual_Rhs);
1747 Expand_Assign_Array (N, Actual_Rhs);
1753 elsif Is_Record_Type (Typ) then
1754 Expand_Assign_Record (N);
1757 -- Scalar types. This is where we perform the processing related
1758 -- to the requirements of (RM 13.9.1(9-11)) concerning the handling
1759 -- of invalid scalar values.
1761 elsif Is_Scalar_Type (Typ) then
1763 -- Case where right side is known valid
1765 if Expr_Known_Valid (Rhs) then
1767 -- Here the right side is valid, so it is fine. The case to
1768 -- deal with is when the left side is a local variable reference
1769 -- whose value is not currently known to be valid. If this is
1770 -- the case, and the assignment appears in an unconditional
1771 -- context, then we can mark the left side as now being valid.
1773 if Is_Local_Variable_Reference (Lhs)
1774 and then not Is_Known_Valid (Entity (Lhs))
1775 and then In_Unconditional_Context (N)
1777 Set_Is_Known_Valid (Entity (Lhs), True);
1780 -- Case where right side may be invalid in the sense of the RM
1781 -- reference above. The RM does not require that we check for
1782 -- the validity on an assignment, but it does require that the
1783 -- assignment of an invalid value not cause erroneous behavior.
1785 -- The general approach in GNAT is to use the Is_Known_Valid flag
1786 -- to avoid the need for validity checking on assignments. However
1787 -- in some cases, we have to do validity checking in order to make
1788 -- sure that the setting of this flag is correct.
1791 -- Validate right side if we are validating copies
1793 if Validity_Checks_On
1794 and then Validity_Check_Copies
1798 -- We can propagate this to the left side where appropriate
1800 if Is_Local_Variable_Reference (Lhs)
1801 and then not Is_Known_Valid (Entity (Lhs))
1802 and then In_Unconditional_Context (N)
1804 Set_Is_Known_Valid (Entity (Lhs), True);
1807 -- Otherwise check to see what should be done
1809 -- If left side is a local variable, then we just set its
1810 -- flag to indicate that its value may no longer be valid,
1811 -- since we are copying a potentially invalid value.
1813 elsif Is_Local_Variable_Reference (Lhs) then
1814 Set_Is_Known_Valid (Entity (Lhs), False);
1816 -- Check for case of a nonlocal variable on the left side
1817 -- which is currently known to be valid. In this case, we
1818 -- simply ensure that the right side is valid. We only play
1819 -- the game of copying validity status for local variables,
1820 -- since we are doing this statically, not by tracing the
1823 elsif Is_Entity_Name (Lhs)
1824 and then Is_Known_Valid (Entity (Lhs))
1826 -- Note that the Ensure_Valid call is ignored if the
1827 -- Validity_Checking mode is set to none so we do not
1828 -- need to worry about that case here.
1832 -- In all other cases, we can safely copy an invalid value
1833 -- without worrying about the status of the left side. Since
1834 -- it is not a variable reference it will not be considered
1835 -- as being known to be valid in any case.
1843 -- Defend against invalid subscripts on left side if we are in
1844 -- standard validity checking mode. No need to do this if we
1845 -- are checking all subscripts.
1847 if Validity_Checks_On
1848 and then Validity_Check_Default
1849 and then not Validity_Check_Subscripts
1851 Check_Valid_Lvalue_Subscripts (Lhs);
1855 when RE_Not_Available =>
1857 end Expand_N_Assignment_Statement;
1859 ------------------------------
1860 -- Expand_N_Block_Statement --
1861 ------------------------------
1863 -- Encode entity names defined in block statement
1865 procedure Expand_N_Block_Statement (N : Node_Id) is
1867 Qualify_Entity_Names (N);
1868 end Expand_N_Block_Statement;
1870 -----------------------------
1871 -- Expand_N_Case_Statement --
1872 -----------------------------
1874 procedure Expand_N_Case_Statement (N : Node_Id) is
1875 Loc : constant Source_Ptr := Sloc (N);
1876 Expr : constant Node_Id := Expression (N);
1884 -- Check for the situation where we know at compile time which
1885 -- branch will be taken
1887 if Compile_Time_Known_Value (Expr) then
1888 Alt := Find_Static_Alternative (N);
1890 -- Move the statements from this alternative after the case
1891 -- statement. They are already analyzed, so will be skipped
1894 Insert_List_After (N, Statements (Alt));
1896 -- That leaves the case statement as a shell. The alternative
1897 -- that will be executed is reset to a null list. So now we can
1898 -- kill the entire case statement.
1900 Kill_Dead_Code (Expression (N));
1901 Kill_Dead_Code (Alternatives (N));
1902 Rewrite (N, Make_Null_Statement (Loc));
1906 -- Here if the choice is not determined at compile time
1909 Last_Alt : constant Node_Id := Last (Alternatives (N));
1911 Others_Present : Boolean;
1912 Others_Node : Node_Id;
1914 Then_Stms : List_Id;
1915 Else_Stms : List_Id;
1918 if Nkind (First (Discrete_Choices (Last_Alt))) = N_Others_Choice then
1919 Others_Present := True;
1920 Others_Node := Last_Alt;
1922 Others_Present := False;
1925 -- First step is to worry about possible invalid argument. The RM
1926 -- requires (RM 5.4(13)) that if the result is invalid (e.g. it is
1927 -- outside the base range), then Constraint_Error must be raised.
1929 -- Case of validity check required (validity checks are on, the
1930 -- expression is not known to be valid, and the case statement
1931 -- comes from source -- no need to validity check internally
1932 -- generated case statements).
1934 if Validity_Check_Default then
1935 Ensure_Valid (Expr);
1938 -- If there is only a single alternative, just replace it with
1939 -- the sequence of statements since obviously that is what is
1940 -- going to be executed in all cases.
1942 Len := List_Length (Alternatives (N));
1945 -- We still need to evaluate the expression if it has any
1948 Remove_Side_Effects (Expression (N));
1950 Insert_List_After (N, Statements (First (Alternatives (N))));
1952 -- That leaves the case statement as a shell. The alternative
1953 -- that will be executed is reset to a null list. So now we can
1954 -- kill the entire case statement.
1956 Kill_Dead_Code (Expression (N));
1957 Rewrite (N, Make_Null_Statement (Loc));
1961 -- An optimization. If there are only two alternatives, and only
1962 -- a single choice, then rewrite the whole case statement as an
1963 -- if statement, since this can result in susbequent optimizations.
1964 -- This helps not only with case statements in the source of a
1965 -- simple form, but also with generated code (discriminant check
1966 -- functions in particular)
1969 Chlist := Discrete_Choices (First (Alternatives (N)));
1971 if List_Length (Chlist) = 1 then
1972 Choice := First (Chlist);
1974 Then_Stms := Statements (First (Alternatives (N)));
1975 Else_Stms := Statements (Last (Alternatives (N)));
1977 -- For TRUE, generate "expression", not expression = true
1979 if Nkind (Choice) = N_Identifier
1980 and then Entity (Choice) = Standard_True
1982 Cond := Expression (N);
1984 -- For FALSE, generate "expression" and switch then/else
1986 elsif Nkind (Choice) = N_Identifier
1987 and then Entity (Choice) = Standard_False
1989 Cond := Expression (N);
1990 Else_Stms := Statements (First (Alternatives (N)));
1991 Then_Stms := Statements (Last (Alternatives (N)));
1993 -- For a range, generate "expression in range"
1995 elsif Nkind (Choice) = N_Range
1996 or else (Nkind (Choice) = N_Attribute_Reference
1997 and then Attribute_Name (Choice) = Name_Range)
1998 or else (Is_Entity_Name (Choice)
1999 and then Is_Type (Entity (Choice)))
2000 or else Nkind (Choice) = N_Subtype_Indication
2004 Left_Opnd => Expression (N),
2005 Right_Opnd => Relocate_Node (Choice));
2007 -- For any other subexpression "expression = value"
2012 Left_Opnd => Expression (N),
2013 Right_Opnd => Relocate_Node (Choice));
2016 -- Now rewrite the case as an IF
2019 Make_If_Statement (Loc,
2021 Then_Statements => Then_Stms,
2022 Else_Statements => Else_Stms));
2028 -- If the last alternative is not an Others choice, replace it
2029 -- with an N_Others_Choice. Note that we do not bother to call
2030 -- Analyze on the modified case statement, since it's only effect
2031 -- would be to compute the contents of the Others_Discrete_Choices
2032 -- which is not needed by the back end anyway.
2034 -- The reason we do this is that the back end always needs some
2035 -- default for a switch, so if we have not supplied one in the
2036 -- processing above for validity checking, then we need to
2039 if not Others_Present then
2040 Others_Node := Make_Others_Choice (Sloc (Last_Alt));
2041 Set_Others_Discrete_Choices
2042 (Others_Node, Discrete_Choices (Last_Alt));
2043 Set_Discrete_Choices (Last_Alt, New_List (Others_Node));
2046 end Expand_N_Case_Statement;
2048 -----------------------------
2049 -- Expand_N_Exit_Statement --
2050 -----------------------------
2052 -- The only processing required is to deal with a possible C/Fortran
2053 -- boolean value used as the condition for the exit statement.
2055 procedure Expand_N_Exit_Statement (N : Node_Id) is
2057 Adjust_Condition (Condition (N));
2058 end Expand_N_Exit_Statement;
2060 -----------------------------
2061 -- Expand_N_Goto_Statement --
2062 -----------------------------
2064 -- Add poll before goto if polling active
2066 procedure Expand_N_Goto_Statement (N : Node_Id) is
2068 Generate_Poll_Call (N);
2069 end Expand_N_Goto_Statement;
2071 ---------------------------
2072 -- Expand_N_If_Statement --
2073 ---------------------------
2075 -- First we deal with the case of C and Fortran convention boolean
2076 -- values, with zero/non-zero semantics.
2078 -- Second, we deal with the obvious rewriting for the cases where the
2079 -- condition of the IF is known at compile time to be True or False.
2081 -- Third, we remove elsif parts which have non-empty Condition_Actions
2082 -- and rewrite as independent if statements. For example:
2093 -- <<condition actions of y>>
2099 -- This rewriting is needed if at least one elsif part has a non-empty
2100 -- Condition_Actions list. We also do the same processing if there is
2101 -- a constant condition in an elsif part (in conjunction with the first
2102 -- processing step mentioned above, for the recursive call made to deal
2103 -- with the created inner if, this deals with properly optimizing the
2104 -- cases of constant elsif conditions).
2106 procedure Expand_N_If_Statement (N : Node_Id) is
2107 Loc : constant Source_Ptr := Sloc (N);
2113 Adjust_Condition (Condition (N));
2115 -- The following loop deals with constant conditions for the IF. We
2116 -- need a loop because as we eliminate False conditions, we grab the
2117 -- first elsif condition and use it as the primary condition.
2119 while Compile_Time_Known_Value (Condition (N)) loop
2121 -- If condition is True, we can simply rewrite the if statement
2122 -- now by replacing it by the series of then statements.
2124 if Is_True (Expr_Value (Condition (N))) then
2126 -- All the else parts can be killed
2128 Kill_Dead_Code (Elsif_Parts (N));
2129 Kill_Dead_Code (Else_Statements (N));
2131 Hed := Remove_Head (Then_Statements (N));
2132 Insert_List_After (N, Then_Statements (N));
2136 -- If condition is False, then we can delete the condition and
2137 -- the Then statements
2140 -- We do not delete the condition if constant condition
2141 -- warnings are enabled, since otherwise we end up deleting
2142 -- the desired warning. Of course the backend will get rid
2143 -- of this True/False test anyway, so nothing is lost here.
2145 if not Constant_Condition_Warnings then
2146 Kill_Dead_Code (Condition (N));
2149 Kill_Dead_Code (Then_Statements (N));
2151 -- If there are no elsif statements, then we simply replace
2152 -- the entire if statement by the sequence of else statements.
2154 if No (Elsif_Parts (N)) then
2156 if No (Else_Statements (N))
2157 or else Is_Empty_List (Else_Statements (N))
2160 Make_Null_Statement (Sloc (N)));
2163 Hed := Remove_Head (Else_Statements (N));
2164 Insert_List_After (N, Else_Statements (N));
2170 -- If there are elsif statements, the first of them becomes
2171 -- the if/then section of the rebuilt if statement This is
2172 -- the case where we loop to reprocess this copied condition.
2175 Hed := Remove_Head (Elsif_Parts (N));
2176 Insert_Actions (N, Condition_Actions (Hed));
2177 Set_Condition (N, Condition (Hed));
2178 Set_Then_Statements (N, Then_Statements (Hed));
2180 if Is_Empty_List (Elsif_Parts (N)) then
2181 Set_Elsif_Parts (N, No_List);
2187 -- Loop through elsif parts, dealing with constant conditions and
2188 -- possible expression actions that are present.
2190 if Present (Elsif_Parts (N)) then
2191 E := First (Elsif_Parts (N));
2192 while Present (E) loop
2193 Adjust_Condition (Condition (E));
2195 -- If there are condition actions, then we rewrite the if
2196 -- statement as indicated above. We also do the same rewrite
2197 -- if the condition is True or False. The further processing
2198 -- of this constant condition is then done by the recursive
2199 -- call to expand the newly created if statement
2201 if Present (Condition_Actions (E))
2202 or else Compile_Time_Known_Value (Condition (E))
2204 -- Note this is not an implicit if statement, since it is
2205 -- part of an explicit if statement in the source (or of an
2206 -- implicit if statement that has already been tested).
2209 Make_If_Statement (Sloc (E),
2210 Condition => Condition (E),
2211 Then_Statements => Then_Statements (E),
2212 Elsif_Parts => No_List,
2213 Else_Statements => Else_Statements (N));
2215 -- Elsif parts for new if come from remaining elsif's of parent
2217 while Present (Next (E)) loop
2218 if No (Elsif_Parts (New_If)) then
2219 Set_Elsif_Parts (New_If, New_List);
2222 Append (Remove_Next (E), Elsif_Parts (New_If));
2225 Set_Else_Statements (N, New_List (New_If));
2227 if Present (Condition_Actions (E)) then
2228 Insert_List_Before (New_If, Condition_Actions (E));
2233 if Is_Empty_List (Elsif_Parts (N)) then
2234 Set_Elsif_Parts (N, No_List);
2240 -- No special processing for that elsif part, move to next
2248 -- Some more optimizations applicable if we still have an IF statement
2250 if Nkind (N) /= N_If_Statement then
2254 -- Another optimization, special cases that can be simplified
2256 -- if expression then
2262 -- can be changed to:
2264 -- return expression;
2268 -- if expression then
2274 -- can be changed to:
2276 -- return not (expression);
2278 if Nkind (N) = N_If_Statement
2279 and then No (Elsif_Parts (N))
2280 and then Present (Else_Statements (N))
2281 and then List_Length (Then_Statements (N)) = 1
2282 and then List_Length (Else_Statements (N)) = 1
2285 Then_Stm : constant Node_Id := First (Then_Statements (N));
2286 Else_Stm : constant Node_Id := First (Else_Statements (N));
2289 if Nkind (Then_Stm) = N_Return_Statement
2291 Nkind (Else_Stm) = N_Return_Statement
2294 Then_Expr : constant Node_Id := Expression (Then_Stm);
2295 Else_Expr : constant Node_Id := Expression (Else_Stm);
2298 if Nkind (Then_Expr) = N_Identifier
2300 Nkind (Else_Expr) = N_Identifier
2302 if Entity (Then_Expr) = Standard_True
2303 and then Entity (Else_Expr) = Standard_False
2306 Make_Return_Statement (Loc,
2307 Expression => Relocate_Node (Condition (N))));
2311 elsif Entity (Then_Expr) = Standard_False
2312 and then Entity (Else_Expr) = Standard_True
2315 Make_Return_Statement (Loc,
2318 Right_Opnd => Relocate_Node (Condition (N)))));
2327 end Expand_N_If_Statement;
2329 -----------------------------
2330 -- Expand_N_Loop_Statement --
2331 -----------------------------
2333 -- 1. Deal with while condition for C/Fortran boolean
2334 -- 2. Deal with loops with a non-standard enumeration type range
2335 -- 3. Deal with while loops where Condition_Actions is set
2336 -- 4. Insert polling call if required
2338 procedure Expand_N_Loop_Statement (N : Node_Id) is
2339 Loc : constant Source_Ptr := Sloc (N);
2340 Isc : constant Node_Id := Iteration_Scheme (N);
2343 if Present (Isc) then
2344 Adjust_Condition (Condition (Isc));
2347 if Is_Non_Empty_List (Statements (N)) then
2348 Generate_Poll_Call (First (Statements (N)));
2355 -- Handle the case where we have a for loop with the range type being
2356 -- an enumeration type with non-standard representation. In this case
2359 -- for x in [reverse] a .. b loop
2365 -- for xP in [reverse] integer
2366 -- range etype'Pos (a) .. etype'Pos (b) loop
2368 -- x : constant etype := Pos_To_Rep (xP);
2374 if Present (Loop_Parameter_Specification (Isc)) then
2376 LPS : constant Node_Id := Loop_Parameter_Specification (Isc);
2377 Loop_Id : constant Entity_Id := Defining_Identifier (LPS);
2378 Ltype : constant Entity_Id := Etype (Loop_Id);
2379 Btype : constant Entity_Id := Base_Type (Ltype);
2384 if not Is_Enumeration_Type (Btype)
2385 or else No (Enum_Pos_To_Rep (Btype))
2391 Make_Defining_Identifier (Loc,
2392 Chars => New_External_Name (Chars (Loop_Id), 'P'));
2394 -- If the type has a contiguous representation, successive
2395 -- values can be generated as offsets from the first literal.
2397 if Has_Contiguous_Rep (Btype) then
2399 Unchecked_Convert_To (Btype,
2402 Make_Integer_Literal (Loc,
2403 Enumeration_Rep (First_Literal (Btype))),
2404 Right_Opnd => New_Reference_To (New_Id, Loc)));
2406 -- Use the constructed array Enum_Pos_To_Rep.
2409 Make_Indexed_Component (Loc,
2410 Prefix => New_Reference_To (Enum_Pos_To_Rep (Btype), Loc),
2411 Expressions => New_List (New_Reference_To (New_Id, Loc)));
2415 Make_Loop_Statement (Loc,
2416 Identifier => Identifier (N),
2419 Make_Iteration_Scheme (Loc,
2420 Loop_Parameter_Specification =>
2421 Make_Loop_Parameter_Specification (Loc,
2422 Defining_Identifier => New_Id,
2423 Reverse_Present => Reverse_Present (LPS),
2425 Discrete_Subtype_Definition =>
2426 Make_Subtype_Indication (Loc,
2429 New_Reference_To (Standard_Natural, Loc),
2432 Make_Range_Constraint (Loc,
2437 Make_Attribute_Reference (Loc,
2439 New_Reference_To (Btype, Loc),
2441 Attribute_Name => Name_Pos,
2443 Expressions => New_List (
2445 (Type_Low_Bound (Ltype)))),
2448 Make_Attribute_Reference (Loc,
2450 New_Reference_To (Btype, Loc),
2452 Attribute_Name => Name_Pos,
2454 Expressions => New_List (
2456 (Type_High_Bound (Ltype))))))))),
2458 Statements => New_List (
2459 Make_Block_Statement (Loc,
2460 Declarations => New_List (
2461 Make_Object_Declaration (Loc,
2462 Defining_Identifier => Loop_Id,
2463 Constant_Present => True,
2464 Object_Definition => New_Reference_To (Ltype, Loc),
2465 Expression => Expr)),
2467 Handled_Statement_Sequence =>
2468 Make_Handled_Sequence_Of_Statements (Loc,
2469 Statements => Statements (N)))),
2471 End_Label => End_Label (N)));
2475 -- Second case, if we have a while loop with Condition_Actions set,
2476 -- then we change it into a plain loop:
2485 -- <<condition actions>>
2491 and then Present (Condition_Actions (Isc))
2498 Make_Exit_Statement (Sloc (Condition (Isc)),
2500 Make_Op_Not (Sloc (Condition (Isc)),
2501 Right_Opnd => Condition (Isc)));
2503 Prepend (ES, Statements (N));
2504 Insert_List_Before (ES, Condition_Actions (Isc));
2506 -- This is not an implicit loop, since it is generated in
2507 -- response to the loop statement being processed. If this
2508 -- is itself implicit, the restriction has already been
2509 -- checked. If not, it is an explicit loop.
2512 Make_Loop_Statement (Sloc (N),
2513 Identifier => Identifier (N),
2514 Statements => Statements (N),
2515 End_Label => End_Label (N)));
2520 end Expand_N_Loop_Statement;
2522 -------------------------------
2523 -- Expand_N_Return_Statement --
2524 -------------------------------
2526 procedure Expand_N_Return_Statement (N : Node_Id) is
2527 Loc : constant Source_Ptr := Sloc (N);
2528 Exp : constant Node_Id := Expression (N);
2532 Scope_Id : Entity_Id;
2536 Goto_Stat : Node_Id;
2539 Return_Type : Entity_Id;
2540 Result_Exp : Node_Id;
2541 Result_Id : Entity_Id;
2542 Result_Obj : Node_Id;
2545 -- Case where returned expression is present
2547 if Present (Exp) then
2549 -- Always normalize C/Fortran boolean result. This is not always
2550 -- necessary, but it seems a good idea to minimize the passing
2551 -- around of non-normalized values, and in any case this handles
2552 -- the processing of barrier functions for protected types, which
2553 -- turn the condition into a return statement.
2555 Exptyp := Etype (Exp);
2557 if Is_Boolean_Type (Exptyp)
2558 and then Nonzero_Is_True (Exptyp)
2560 Adjust_Condition (Exp);
2561 Adjust_Result_Type (Exp, Exptyp);
2564 -- Do validity check if enabled for returns
2566 if Validity_Checks_On
2567 and then Validity_Check_Returns
2573 -- Find relevant enclosing scope from which return is returning
2575 Cur_Idx := Scope_Stack.Last;
2577 Scope_Id := Scope_Stack.Table (Cur_Idx).Entity;
2579 if Ekind (Scope_Id) /= E_Block
2580 and then Ekind (Scope_Id) /= E_Loop
2585 Cur_Idx := Cur_Idx - 1;
2586 pragma Assert (Cur_Idx >= 0);
2591 Kind := Ekind (Scope_Id);
2593 -- If it is a return from procedures do no extra steps.
2595 if Kind = E_Procedure or else Kind = E_Generic_Procedure then
2599 pragma Assert (Is_Entry (Scope_Id));
2601 -- Look at the enclosing block to see whether the return is from
2602 -- an accept statement or an entry body.
2604 for J in reverse 0 .. Cur_Idx loop
2605 Scope_Id := Scope_Stack.Table (J).Entity;
2606 exit when Is_Concurrent_Type (Scope_Id);
2609 -- If it is a return from accept statement it should be expanded
2610 -- as a call to RTS Complete_Rendezvous and a goto to the end of
2613 -- (cf : Expand_N_Accept_Statement, Expand_N_Selective_Accept,
2614 -- Expand_N_Accept_Alternative in exp_ch9.adb)
2616 if Is_Task_Type (Scope_Id) then
2618 Call := (Make_Procedure_Call_Statement (Loc,
2619 Name => New_Reference_To
2620 (RTE (RE_Complete_Rendezvous), Loc)));
2621 Insert_Before (N, Call);
2622 -- why not insert actions here???
2625 Acc_Stat := Parent (N);
2626 while Nkind (Acc_Stat) /= N_Accept_Statement loop
2627 Acc_Stat := Parent (Acc_Stat);
2630 Lab_Node := Last (Statements
2631 (Handled_Statement_Sequence (Acc_Stat)));
2633 Goto_Stat := Make_Goto_Statement (Loc,
2634 Name => New_Occurrence_Of
2635 (Entity (Identifier (Lab_Node)), Loc));
2637 Set_Analyzed (Goto_Stat);
2639 Rewrite (N, Goto_Stat);
2642 -- If it is a return from an entry body, put a Complete_Entry_Body
2643 -- call in front of the return.
2645 elsif Is_Protected_Type (Scope_Id) then
2648 Make_Procedure_Call_Statement (Loc,
2649 Name => New_Reference_To
2650 (RTE (RE_Complete_Entry_Body), Loc),
2651 Parameter_Associations => New_List
2652 (Make_Attribute_Reference (Loc,
2656 (Corresponding_Body (Parent (Scope_Id))),
2658 Attribute_Name => Name_Unchecked_Access)));
2660 Insert_Before (N, Call);
2669 Return_Type := Etype (Scope_Id);
2670 Utyp := Underlying_Type (Return_Type);
2672 -- Check the result expression of a scalar function against
2673 -- the subtype of the function by inserting a conversion.
2674 -- This conversion must eventually be performed for other
2675 -- classes of types, but for now it's only done for scalars.
2678 if Is_Scalar_Type (T) then
2679 Rewrite (Exp, Convert_To (Return_Type, Exp));
2683 -- Implement the rules of 6.5(8-10), which require a tag check in
2684 -- the case of a limited tagged return type, and tag reassignment
2685 -- for nonlimited tagged results. These actions are needed when
2686 -- the return type is a specific tagged type and the result
2687 -- expression is a conversion or a formal parameter, because in
2688 -- that case the tag of the expression might differ from the tag
2689 -- of the specific result type.
2691 if Is_Tagged_Type (Utyp)
2692 and then not Is_Class_Wide_Type (Utyp)
2693 and then (Nkind (Exp) = N_Type_Conversion
2694 or else Nkind (Exp) = N_Unchecked_Type_Conversion
2695 or else (Is_Entity_Name (Exp)
2696 and then Ekind (Entity (Exp)) in Formal_Kind))
2698 -- When the return type is limited, perform a check that the
2699 -- tag of the result is the same as the tag of the return type.
2701 if Is_Limited_Type (Return_Type) then
2703 Make_Raise_Constraint_Error (Loc,
2707 Make_Selected_Component (Loc,
2708 Prefix => Duplicate_Subexpr (Exp),
2710 New_Reference_To (Tag_Component (Utyp), Loc)),
2712 Unchecked_Convert_To (RTE (RE_Tag),
2714 (Access_Disp_Table (Base_Type (Utyp)), Loc))),
2715 Reason => CE_Tag_Check_Failed));
2717 -- If the result type is a specific nonlimited tagged type,
2718 -- then we have to ensure that the tag of the result is that
2719 -- of the result type. This is handled by making a copy of the
2720 -- expression in the case where it might have a different tag,
2721 -- namely when the expression is a conversion or a formal
2722 -- parameter. We create a new object of the result type and
2723 -- initialize it from the expression, which will implicitly
2724 -- force the tag to be set appropriately.
2728 Make_Defining_Identifier (Loc, New_Internal_Name ('R'));
2729 Result_Exp := New_Reference_To (Result_Id, Loc);
2732 Make_Object_Declaration (Loc,
2733 Defining_Identifier => Result_Id,
2734 Object_Definition => New_Reference_To (Return_Type, Loc),
2735 Constant_Present => True,
2736 Expression => Relocate_Node (Exp));
2738 Set_Assignment_OK (Result_Obj);
2739 Insert_Action (Exp, Result_Obj);
2741 Rewrite (Exp, Result_Exp);
2742 Analyze_And_Resolve (Exp, Return_Type);
2746 -- Deal with returning variable length objects and controlled types
2748 -- Nothing to do if we are returning by reference, or this is not
2749 -- a type that requires special processing (indicated by the fact
2750 -- that it requires a cleanup scope for the secondary stack case)
2752 if Is_Return_By_Reference_Type (T)
2753 or else not Requires_Transient_Scope (Return_Type)
2757 -- Case of secondary stack not used
2759 elsif Function_Returns_With_DSP (Scope_Id) then
2761 -- Here what we need to do is to always return by reference, since
2762 -- we will return with the stack pointer depressed. We may need to
2763 -- do a copy to a local temporary before doing this return.
2765 No_Secondary_Stack_Case : declare
2766 Local_Copy_Required : Boolean := False;
2767 -- Set to True if a local copy is required
2769 Copy_Ent : Entity_Id;
2770 -- Used for the target entity if a copy is required
2773 -- Declaration used to create copy if needed
2775 procedure Test_Copy_Required (Expr : Node_Id);
2776 -- Determines if Expr represents a return value for which a
2777 -- copy is required. More specifically, a copy is not required
2778 -- if Expr represents an object or component of an object that
2779 -- is either in the local subprogram frame, or is constant.
2780 -- If a copy is required, then Local_Copy_Required is set True.
2782 ------------------------
2783 -- Test_Copy_Required --
2784 ------------------------
2786 procedure Test_Copy_Required (Expr : Node_Id) is
2790 -- If component, test prefix (object containing component)
2792 if Nkind (Expr) = N_Indexed_Component
2794 Nkind (Expr) = N_Selected_Component
2796 Test_Copy_Required (Prefix (Expr));
2799 -- See if we have an entity name
2801 elsif Is_Entity_Name (Expr) then
2802 Ent := Entity (Expr);
2804 -- Constant entity is always OK, no copy required
2806 if Ekind (Ent) = E_Constant then
2809 -- No copy required for local variable
2811 elsif Ekind (Ent) = E_Variable
2812 and then Scope (Ent) = Current_Subprogram
2818 -- All other cases require a copy
2820 Local_Copy_Required := True;
2821 end Test_Copy_Required;
2823 -- Start of processing for No_Secondary_Stack_Case
2826 -- No copy needed if result is from a function call.
2827 -- In this case the result is already being returned by
2828 -- reference with the stack pointer depressed.
2830 -- To make up for a gcc 2.8.1 deficiency (???), we perform
2831 -- the copy for array types if the constrained status of the
2832 -- target type is different from that of the expression.
2834 if Requires_Transient_Scope (T)
2836 (not Is_Array_Type (T)
2837 or else Is_Constrained (T) = Is_Constrained (Return_Type)
2838 or else Controlled_Type (T))
2839 and then Nkind (Exp) = N_Function_Call
2843 -- We always need a local copy for a controlled type, since
2844 -- we are required to finalize the local value before return.
2845 -- The copy will automatically include the required finalize.
2846 -- Moreover, gigi cannot make this copy, since we need special
2847 -- processing to ensure proper behavior for finalization.
2849 -- Note: the reason we are returning with a depressed stack
2850 -- pointer in the controlled case (even if the type involved
2851 -- is constrained) is that we must make a local copy to deal
2852 -- properly with the requirement that the local result be
2855 elsif Controlled_Type (Utyp) then
2857 Make_Defining_Identifier (Loc,
2858 Chars => New_Internal_Name ('R'));
2860 -- Build declaration to do the copy, and insert it, setting
2861 -- Assignment_OK, because we may be copying a limited type.
2862 -- In addition we set the special flag to inhibit finalize
2863 -- attachment if this is a controlled type (since this attach
2864 -- must be done by the caller, otherwise if we attach it here
2865 -- we will finalize the returned result prematurely).
2868 Make_Object_Declaration (Loc,
2869 Defining_Identifier => Copy_Ent,
2870 Object_Definition => New_Occurrence_Of (Return_Type, Loc),
2871 Expression => Relocate_Node (Exp));
2873 Set_Assignment_OK (Decl);
2874 Set_Delay_Finalize_Attach (Decl);
2875 Insert_Action (N, Decl);
2877 -- Now the actual return uses the copied value
2879 Rewrite (Exp, New_Occurrence_Of (Copy_Ent, Loc));
2880 Analyze_And_Resolve (Exp, Return_Type);
2882 -- Since we have made the copy, gigi does not have to, so
2883 -- we set the By_Ref flag to prevent another copy being made.
2887 -- Non-controlled cases
2890 Test_Copy_Required (Exp);
2892 -- If a local copy is required, then gigi will make the
2893 -- copy, otherwise, we can return the result directly,
2894 -- so set By_Ref to suppress the gigi copy.
2896 if not Local_Copy_Required then
2900 end No_Secondary_Stack_Case;
2902 -- Here if secondary stack is used
2905 -- Make sure that no surrounding block will reclaim the
2906 -- secondary-stack on which we are going to put the result.
2907 -- Not only may this introduce secondary stack leaks but worse,
2908 -- if the reclamation is done too early, then the result we are
2909 -- returning may get clobbered. See example in 7417-003.
2912 S : Entity_Id := Current_Scope;
2915 while Ekind (S) = E_Block or else Ekind (S) = E_Loop loop
2916 Set_Sec_Stack_Needed_For_Return (S, True);
2917 S := Enclosing_Dynamic_Scope (S);
2921 -- Optimize the case where the result is a function call. In this
2922 -- case either the result is already on the secondary stack, or is
2923 -- already being returned with the stack pointer depressed and no
2924 -- further processing is required except to set the By_Ref flag to
2925 -- ensure that gigi does not attempt an extra unnecessary copy.
2926 -- (actually not just unnecessary but harmfully wrong in the case
2927 -- of a controlled type, where gigi does not know how to do a copy).
2928 -- To make up for a gcc 2.8.1 deficiency (???), we perform
2929 -- the copy for array types if the constrained status of the
2930 -- target type is different from that of the expression.
2932 if Requires_Transient_Scope (T)
2934 (not Is_Array_Type (T)
2935 or else Is_Constrained (T) = Is_Constrained (Return_Type)
2936 or else Controlled_Type (T))
2937 and then Nkind (Exp) = N_Function_Call
2941 -- For controlled types, do the allocation on the sec-stack
2942 -- manually in order to call adjust at the right time
2943 -- type Anon1 is access Return_Type;
2944 -- for Anon1'Storage_pool use ss_pool;
2945 -- Anon2 : anon1 := new Return_Type'(expr);
2946 -- return Anon2.all;
2948 elsif Controlled_Type (Utyp) then
2950 Loc : constant Source_Ptr := Sloc (N);
2951 Temp : constant Entity_Id :=
2952 Make_Defining_Identifier (Loc,
2953 Chars => New_Internal_Name ('R'));
2954 Acc_Typ : constant Entity_Id :=
2955 Make_Defining_Identifier (Loc,
2956 Chars => New_Internal_Name ('A'));
2957 Alloc_Node : Node_Id;
2960 Set_Ekind (Acc_Typ, E_Access_Type);
2962 Set_Associated_Storage_Pool (Acc_Typ, RTE (RE_SS_Pool));
2965 Make_Allocator (Loc,
2967 Make_Qualified_Expression (Loc,
2968 Subtype_Mark => New_Reference_To (Etype (Exp), Loc),
2969 Expression => Relocate_Node (Exp)));
2971 Insert_List_Before_And_Analyze (N, New_List (
2972 Make_Full_Type_Declaration (Loc,
2973 Defining_Identifier => Acc_Typ,
2975 Make_Access_To_Object_Definition (Loc,
2976 Subtype_Indication =>
2977 New_Reference_To (Return_Type, Loc))),
2979 Make_Object_Declaration (Loc,
2980 Defining_Identifier => Temp,
2981 Object_Definition => New_Reference_To (Acc_Typ, Loc),
2982 Expression => Alloc_Node)));
2985 Make_Explicit_Dereference (Loc,
2986 Prefix => New_Reference_To (Temp, Loc)));
2988 Analyze_And_Resolve (Exp, Return_Type);
2991 -- Otherwise use the gigi mechanism to allocate result on the
2995 Set_Storage_Pool (N, RTE (RE_SS_Pool));
2997 -- If we are generating code for the Java VM do not use
2998 -- SS_Allocate since everything is heap-allocated anyway.
3001 Set_Procedure_To_Call (N, RTE (RE_SS_Allocate));
3007 when RE_Not_Available =>
3009 end Expand_N_Return_Statement;
3011 ------------------------------
3012 -- Make_Tag_Ctrl_Assignment --
3013 ------------------------------
3015 function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id is
3016 Loc : constant Source_Ptr := Sloc (N);
3017 L : constant Node_Id := Name (N);
3018 T : constant Entity_Id := Underlying_Type (Etype (L));
3020 Ctrl_Act : constant Boolean := Controlled_Type (T)
3021 and then not No_Ctrl_Actions (N);
3023 Save_Tag : constant Boolean := Is_Tagged_Type (T)
3024 and then not No_Ctrl_Actions (N)
3025 and then not Java_VM;
3026 -- Tags are not saved and restored when Java_VM because JVM tags
3027 -- are represented implicitly in objects.
3030 Tag_Tmp : Entity_Id;
3031 Prev_Tmp : Entity_Id;
3032 Next_Tmp : Entity_Id;
3034 Ctrl_Ref2 : Node_Id := Empty;
3035 Prev_Tmp2 : Entity_Id := Empty; -- prevent warning
3036 Next_Tmp2 : Entity_Id := Empty; -- prevent warning
3041 -- Finalize the target of the assignment when controlled.
3042 -- We have two exceptions here:
3044 -- 1. If we are in an init proc since it is an initialization
3045 -- more than an assignment
3047 -- 2. If the left-hand side is a temporary that was not initialized
3048 -- (or the parent part of a temporary since it is the case in
3049 -- extension aggregates). Such a temporary does not come from
3050 -- source. We must examine the original node for the prefix, because
3051 -- it may be a component of an entry formal, in which case it has
3052 -- been rewritten and does not appear to come from source either.
3054 -- Case of init proc
3056 if not Ctrl_Act then
3059 -- The left hand side is an uninitialized temporary
3061 elsif Nkind (L) = N_Type_Conversion
3062 and then Is_Entity_Name (Expression (L))
3063 and then No_Initialization (Parent (Entity (Expression (L))))
3067 Append_List_To (Res,
3069 Ref => Duplicate_Subexpr_No_Checks (L),
3071 With_Detach => New_Reference_To (Standard_False, Loc)));
3074 Next_Tmp := Make_Defining_Identifier (Loc, New_Internal_Name ('C'));
3076 -- Save the Tag in a local variable Tag_Tmp
3080 Make_Defining_Identifier (Loc, New_Internal_Name ('A'));
3083 Make_Object_Declaration (Loc,
3084 Defining_Identifier => Tag_Tmp,
3085 Object_Definition => New_Reference_To (RTE (RE_Tag), Loc),
3087 Make_Selected_Component (Loc,
3088 Prefix => Duplicate_Subexpr_No_Checks (L),
3089 Selector_Name => New_Reference_To (Tag_Component (T), Loc))));
3091 -- Otherwise Tag_Tmp not used
3097 -- Save the Finalization Pointers in local variables Prev_Tmp and
3098 -- Next_Tmp. For objects with Has_Controlled_Component set, these
3099 -- pointers are in the Record_Controller and if it is also
3100 -- Is_Controlled, we need to save the object pointers as well.
3103 Ctrl_Ref := Duplicate_Subexpr_No_Checks (L);
3105 if Has_Controlled_Component (T) then
3107 Make_Selected_Component (Loc,
3110 New_Reference_To (Controller_Component (T), Loc));
3112 if Is_Controlled (T) then
3113 Ctrl_Ref2 := Duplicate_Subexpr_No_Checks (L);
3117 Prev_Tmp := Make_Defining_Identifier (Loc, New_Internal_Name ('B'));
3120 Make_Object_Declaration (Loc,
3121 Defining_Identifier => Prev_Tmp,
3123 Object_Definition =>
3124 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc),
3127 Make_Selected_Component (Loc,
3129 Unchecked_Convert_To (RTE (RE_Finalizable), Ctrl_Ref),
3130 Selector_Name => Make_Identifier (Loc, Name_Prev))));
3132 Next_Tmp := Make_Defining_Identifier (Loc, New_Internal_Name ('C'));
3135 Make_Object_Declaration (Loc,
3136 Defining_Identifier => Next_Tmp,
3138 Object_Definition =>
3139 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc),
3142 Make_Selected_Component (Loc,
3144 Unchecked_Convert_To (RTE (RE_Finalizable),
3145 New_Copy_Tree (Ctrl_Ref)),
3146 Selector_Name => Make_Identifier (Loc, Name_Next))));
3148 if Present (Ctrl_Ref2) then
3150 Make_Defining_Identifier (Loc, New_Internal_Name ('B'));
3153 Make_Object_Declaration (Loc,
3154 Defining_Identifier => Prev_Tmp2,
3156 Object_Definition =>
3157 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc),
3160 Make_Selected_Component (Loc,
3162 Unchecked_Convert_To (RTE (RE_Finalizable), Ctrl_Ref2),
3163 Selector_Name => Make_Identifier (Loc, Name_Prev))));
3166 Make_Defining_Identifier (Loc, New_Internal_Name ('C'));
3169 Make_Object_Declaration (Loc,
3170 Defining_Identifier => Next_Tmp2,
3172 Object_Definition =>
3173 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc),
3176 Make_Selected_Component (Loc,
3178 Unchecked_Convert_To (RTE (RE_Finalizable),
3179 New_Copy_Tree (Ctrl_Ref2)),
3180 Selector_Name => Make_Identifier (Loc, Name_Next))));
3183 -- If not controlled type, then Prev_Tmp and Ctrl_Ref unused
3190 -- Do the Assignment
3192 Append_To (Res, Relocate_Node (N));
3198 Make_Assignment_Statement (Loc,
3200 Make_Selected_Component (Loc,
3201 Prefix => Duplicate_Subexpr_No_Checks (L),
3202 Selector_Name => New_Reference_To (Tag_Component (T), Loc)),
3203 Expression => New_Reference_To (Tag_Tmp, Loc)));
3206 -- Restore the finalization pointers
3210 Make_Assignment_Statement (Loc,
3212 Make_Selected_Component (Loc,
3214 Unchecked_Convert_To (RTE (RE_Finalizable),
3215 New_Copy_Tree (Ctrl_Ref)),
3216 Selector_Name => Make_Identifier (Loc, Name_Prev)),
3217 Expression => New_Reference_To (Prev_Tmp, Loc)));
3220 Make_Assignment_Statement (Loc,
3222 Make_Selected_Component (Loc,
3224 Unchecked_Convert_To (RTE (RE_Finalizable),
3225 New_Copy_Tree (Ctrl_Ref)),
3226 Selector_Name => Make_Identifier (Loc, Name_Next)),
3227 Expression => New_Reference_To (Next_Tmp, Loc)));
3229 if Present (Ctrl_Ref2) then
3231 Make_Assignment_Statement (Loc,
3233 Make_Selected_Component (Loc,
3235 Unchecked_Convert_To (RTE (RE_Finalizable),
3236 New_Copy_Tree (Ctrl_Ref2)),
3237 Selector_Name => Make_Identifier (Loc, Name_Prev)),
3238 Expression => New_Reference_To (Prev_Tmp2, Loc)));
3241 Make_Assignment_Statement (Loc,
3243 Make_Selected_Component (Loc,
3245 Unchecked_Convert_To (RTE (RE_Finalizable),
3246 New_Copy_Tree (Ctrl_Ref2)),
3247 Selector_Name => Make_Identifier (Loc, Name_Next)),
3248 Expression => New_Reference_To (Next_Tmp2, Loc)));
3252 -- Adjust the target after the assignment when controlled. (not in
3253 -- the init proc since it is an initialization more than an
3257 Append_List_To (Res,
3259 Ref => Duplicate_Subexpr_Move_Checks (L),
3261 Flist_Ref => New_Reference_To (RTE (RE_Global_Final_List), Loc),
3262 With_Attach => Make_Integer_Literal (Loc, 0)));
3268 when RE_Not_Available =>
3270 end Make_Tag_Ctrl_Assignment;
3272 ------------------------------------
3273 -- Possible_Bit_Aligned_Component --
3274 ------------------------------------
3276 function Possible_Bit_Aligned_Component (N : Node_Id) return Boolean is
3280 -- Case of indexed component
3282 when N_Indexed_Component =>
3284 P : constant Node_Id := Prefix (N);
3285 Ptyp : constant Entity_Id := Etype (P);
3288 -- If we know the component size and it is less than 64, then
3289 -- we are definitely OK. The back end always does assignment
3290 -- of misaligned small objects correctly.
3292 if Known_Static_Component_Size (Ptyp)
3293 and then Component_Size (Ptyp) <= 64
3297 -- Otherwise, we need to test the prefix, to see if we are
3298 -- indexing from a possibly unaligned component.
3301 return Possible_Bit_Aligned_Component (P);
3305 -- Case of selected component
3307 when N_Selected_Component =>
3309 P : constant Node_Id := Prefix (N);
3310 Comp : constant Entity_Id := Entity (Selector_Name (N));
3313 -- If there is no component clause, then we are in the clear
3314 -- since the back end will never misalign a large component
3315 -- unless it is forced to do so. In the clear means we need
3316 -- only the recursive test on the prefix.
3318 if Component_May_Be_Bit_Aligned (Comp) then
3321 return Possible_Bit_Aligned_Component (P);
3325 -- If we have neither a record nor array component, it means that
3326 -- we have fallen off the top testing prefixes recursively, and
3327 -- we now have a stand alone object, where we don't have a problem
3333 end Possible_Bit_Aligned_Component;