Dead
[official-gcc.git] / gomp-20050608-branch / gcc / ada / exp_ch5.adb
blob924e3e53d94cbf49a8ab784f7f872a0e28fdd59e
1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT COMPILER COMPONENTS --
4 -- --
5 -- E X P _ C H 5 --
6 -- --
7 -- B o d y --
8 -- --
9 -- Copyright (C) 1992-2006, Free Software Foundation, Inc. --
10 -- --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 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, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
21 -- --
22 -- GNAT was originally developed by the GNAT team at New York University. --
23 -- Extensive contributions were provided by Ada Core Technologies Inc. --
24 -- --
25 ------------------------------------------------------------------------------
27 with Atree; use Atree;
28 with Checks; use Checks;
29 with Einfo; use Einfo;
30 with Elists; use Elists;
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_Tss; use Exp_Tss;
37 with Exp_Util; use Exp_Util;
38 with Hostparm; use Hostparm;
39 with Nlists; use Nlists;
40 with Nmake; use Nmake;
41 with Opt; use Opt;
42 with Restrict; use Restrict;
43 with Rident; use Rident;
44 with Rtsfind; use Rtsfind;
45 with Sinfo; use Sinfo;
46 with Sem; use Sem;
47 with Sem_Ch3; use Sem_Ch3;
48 with Sem_Ch5; use Sem_Ch5;
49 with Sem_Ch8; use Sem_Ch8;
50 with Sem_Ch13; use Sem_Ch13;
51 with Sem_Eval; use Sem_Eval;
52 with Sem_Res; use Sem_Res;
53 with Sem_Util; use Sem_Util;
54 with Snames; use Snames;
55 with Stand; use Stand;
56 with Stringt; use Stringt;
57 with Tbuild; use Tbuild;
58 with Ttypes; use Ttypes;
59 with Uintp; use Uintp;
60 with Validsw; use Validsw;
62 package body Exp_Ch5 is
64 function Change_Of_Representation (N : Node_Id) return Boolean;
65 -- Determine if the right hand side of the assignment N is a type
66 -- conversion which requires a change of representation. Called
67 -- only for the array and record cases.
69 procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id);
70 -- N is an assignment which assigns an array value. This routine process
71 -- the various special cases and checks required for such assignments,
72 -- including change of representation. Rhs is normally simply the right
73 -- hand side of the assignment, except that if the right hand side is
74 -- a type conversion or a qualified expression, then the Rhs is the
75 -- actual expression inside any such type conversions or qualifications.
77 function Expand_Assign_Array_Loop
78 (N : Node_Id;
79 Larray : Entity_Id;
80 Rarray : Entity_Id;
81 L_Type : Entity_Id;
82 R_Type : Entity_Id;
83 Ndim : Pos;
84 Rev : Boolean) return Node_Id;
85 -- N is an assignment statement which assigns an array value. This routine
86 -- expands the assignment into a loop (or nested loops for the case of a
87 -- multi-dimensional array) to do the assignment component by component.
88 -- Larray and Rarray are the entities of the actual arrays on the left
89 -- hand and right hand sides. L_Type and R_Type are the types of these
90 -- arrays (which may not be the same, due to either sliding, or to a
91 -- change of representation case). Ndim is the number of dimensions and
92 -- the parameter Rev indicates if the loops run normally (Rev = False),
93 -- or reversed (Rev = True). The value returned is the constructed
94 -- loop statement. Auxiliary declarations are inserted before node N
95 -- using the standard Insert_Actions mechanism.
97 procedure Expand_Assign_Record (N : Node_Id);
98 -- N is an assignment of a non-tagged record value. This routine handles
99 -- the case where the assignment must be made component by component,
100 -- either because the target is not byte aligned, or there is a change
101 -- of representation.
103 function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id;
104 -- Generate the necessary code for controlled and tagged assignment,
105 -- that is to say, finalization of the target before, adjustement of
106 -- the target after and save and restore of the tag and finalization
107 -- pointers which are not 'part of the value' and must not be changed
108 -- upon assignment. N is the original Assignment node.
110 function Possible_Bit_Aligned_Component (N : Node_Id) return Boolean;
111 -- This function is used in processing the assignment of a record or
112 -- indexed component. The argument N is either the left hand or right
113 -- hand side of an assignment, and this function determines if there
114 -- is a record component reference where the record may be bit aligned
115 -- in a manner that causes trouble for the back end (see description
116 -- of Exp_Util.Component_May_Be_Bit_Aligned for further details).
118 ------------------------------
119 -- Change_Of_Representation --
120 ------------------------------
122 function Change_Of_Representation (N : Node_Id) return Boolean is
123 Rhs : constant Node_Id := Expression (N);
124 begin
125 return
126 Nkind (Rhs) = N_Type_Conversion
127 and then
128 not Same_Representation (Etype (Rhs), Etype (Expression (Rhs)));
129 end Change_Of_Representation;
131 -------------------------
132 -- Expand_Assign_Array --
133 -------------------------
135 -- There are two issues here. First, do we let Gigi do a block move, or
136 -- do we expand out into a loop? Second, we need to set the two flags
137 -- Forwards_OK and Backwards_OK which show whether the block move (or
138 -- corresponding loops) can be legitimately done in a forwards (low to
139 -- high) or backwards (high to low) manner.
141 procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id) is
142 Loc : constant Source_Ptr := Sloc (N);
144 Lhs : constant Node_Id := Name (N);
146 Act_Lhs : constant Node_Id := Get_Referenced_Object (Lhs);
147 Act_Rhs : Node_Id := Get_Referenced_Object (Rhs);
149 L_Type : constant Entity_Id :=
150 Underlying_Type (Get_Actual_Subtype (Act_Lhs));
151 R_Type : Entity_Id :=
152 Underlying_Type (Get_Actual_Subtype (Act_Rhs));
154 L_Slice : constant Boolean := Nkind (Act_Lhs) = N_Slice;
155 R_Slice : constant Boolean := Nkind (Act_Rhs) = N_Slice;
157 Crep : constant Boolean := Change_Of_Representation (N);
159 Larray : Node_Id;
160 Rarray : Node_Id;
162 Ndim : constant Pos := Number_Dimensions (L_Type);
164 Loop_Required : Boolean := False;
165 -- This switch is set to True if the array move must be done using
166 -- an explicit front end generated loop.
168 procedure Apply_Dereference (Arg : in out Node_Id);
169 -- If the argument is an access to an array, and the assignment is
170 -- converted into a procedure call, apply explicit dereference.
172 function Has_Address_Clause (Exp : Node_Id) return Boolean;
173 -- Test if Exp is a reference to an array whose declaration has
174 -- an address clause, or it is a slice of such an array.
176 function Is_Formal_Array (Exp : Node_Id) return Boolean;
177 -- Test if Exp is a reference to an array which is either a formal
178 -- parameter or a slice of a formal parameter. These are the cases
179 -- where hidden aliasing can occur.
181 function Is_Non_Local_Array (Exp : Node_Id) return Boolean;
182 -- Determine if Exp is a reference to an array variable which is other
183 -- than an object defined in the current scope, or a slice of such
184 -- an object. Such objects can be aliased to parameters (unlike local
185 -- array references).
187 -----------------------
188 -- Apply_Dereference --
189 -----------------------
191 procedure Apply_Dereference (Arg : in out Node_Id) is
192 Typ : constant Entity_Id := Etype (Arg);
193 begin
194 if Is_Access_Type (Typ) then
195 Rewrite (Arg, Make_Explicit_Dereference (Loc,
196 Prefix => Relocate_Node (Arg)));
197 Analyze_And_Resolve (Arg, Designated_Type (Typ));
198 end if;
199 end Apply_Dereference;
201 ------------------------
202 -- Has_Address_Clause --
203 ------------------------
205 function Has_Address_Clause (Exp : Node_Id) return Boolean is
206 begin
207 return
208 (Is_Entity_Name (Exp) and then
209 Present (Address_Clause (Entity (Exp))))
210 or else
211 (Nkind (Exp) = N_Slice and then Has_Address_Clause (Prefix (Exp)));
212 end Has_Address_Clause;
214 ---------------------
215 -- Is_Formal_Array --
216 ---------------------
218 function Is_Formal_Array (Exp : Node_Id) return Boolean is
219 begin
220 return
221 (Is_Entity_Name (Exp) and then Is_Formal (Entity (Exp)))
222 or else
223 (Nkind (Exp) = N_Slice and then Is_Formal_Array (Prefix (Exp)));
224 end Is_Formal_Array;
226 ------------------------
227 -- Is_Non_Local_Array --
228 ------------------------
230 function Is_Non_Local_Array (Exp : Node_Id) return Boolean is
231 begin
232 return (Is_Entity_Name (Exp)
233 and then Scope (Entity (Exp)) /= Current_Scope)
234 or else (Nkind (Exp) = N_Slice
235 and then Is_Non_Local_Array (Prefix (Exp)));
236 end Is_Non_Local_Array;
238 -- Determine if Lhs, Rhs are formal arrays or nonlocal arrays
240 Lhs_Formal : constant Boolean := Is_Formal_Array (Act_Lhs);
241 Rhs_Formal : constant Boolean := Is_Formal_Array (Act_Rhs);
243 Lhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Lhs);
244 Rhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Rhs);
246 -- Start of processing for Expand_Assign_Array
248 begin
249 -- Deal with length check, note that the length check is done with
250 -- respect to the right hand side as given, not a possible underlying
251 -- renamed object, since this would generate incorrect extra checks.
253 Apply_Length_Check (Rhs, L_Type);
255 -- We start by assuming that the move can be done in either
256 -- direction, i.e. that the two sides are completely disjoint.
258 Set_Forwards_OK (N, True);
259 Set_Backwards_OK (N, True);
261 -- Normally it is only the slice case that can lead to overlap,
262 -- and explicit checks for slices are made below. But there is
263 -- one case where the slice can be implicit and invisible to us
264 -- and that is the case where we have a one dimensional array,
265 -- and either both operands are parameters, or one is a parameter
266 -- and the other is a global variable. In this case the parameter
267 -- could be a slice that overlaps with the other parameter.
269 -- Check for the case of slices requiring an explicit loop. Normally
270 -- it is only the explicit slice cases that bother us, but in the
271 -- case of one dimensional arrays, parameters can be slices that
272 -- are passed by reference, so we can have aliasing for assignments
273 -- from one parameter to another, or assignments between parameters
274 -- and nonlocal variables. However, if the array subtype is a
275 -- constrained first subtype in the parameter case, then we don't
276 -- have to worry about overlap, since slice assignments aren't
277 -- possible (other than for a slice denoting the whole array).
279 -- Note: overlap is never possible if there is a change of
280 -- representation, so we can exclude this case.
282 if Ndim = 1
283 and then not Crep
284 and then
285 ((Lhs_Formal and Rhs_Formal)
286 or else
287 (Lhs_Formal and Rhs_Non_Local_Var)
288 or else
289 (Rhs_Formal and Lhs_Non_Local_Var))
290 and then
291 (not Is_Constrained (Etype (Lhs))
292 or else not Is_First_Subtype (Etype (Lhs)))
294 -- In the case of compiling for the Java Virtual Machine,
295 -- slices are always passed by making a copy, so we don't
296 -- have to worry about overlap. We also want to prevent
297 -- generation of "<" comparisons for array addresses,
298 -- since that's a meaningless operation on the JVM.
300 and then not Java_VM
301 then
302 Set_Forwards_OK (N, False);
303 Set_Backwards_OK (N, False);
305 -- Note: the bit-packed case is not worrisome here, since if
306 -- we have a slice passed as a parameter, it is always aligned
307 -- on a byte boundary, and if there are no explicit slices, the
308 -- assignment can be performed directly.
309 end if;
311 -- We certainly must use a loop for change of representation
312 -- and also we use the operand of the conversion on the right
313 -- hand side as the effective right hand side (the component
314 -- types must match in this situation).
316 if Crep then
317 Act_Rhs := Get_Referenced_Object (Rhs);
318 R_Type := Get_Actual_Subtype (Act_Rhs);
319 Loop_Required := True;
321 -- We require a loop if the left side is possibly bit unaligned
323 elsif Possible_Bit_Aligned_Component (Lhs)
324 or else
325 Possible_Bit_Aligned_Component (Rhs)
326 then
327 Loop_Required := True;
329 -- Arrays with controlled components are expanded into a loop
330 -- to force calls to adjust at the component level.
332 elsif Has_Controlled_Component (L_Type) then
333 Loop_Required := True;
335 -- If object is atomic, we cannot tolerate a loop
337 elsif Is_Atomic_Object (Act_Lhs)
338 or else
339 Is_Atomic_Object (Act_Rhs)
340 then
341 return;
343 -- Loop is required if we have atomic components since we have to
344 -- be sure to do any accesses on an element by element basis.
346 elsif Has_Atomic_Components (L_Type)
347 or else Has_Atomic_Components (R_Type)
348 or else Is_Atomic (Component_Type (L_Type))
349 or else Is_Atomic (Component_Type (R_Type))
350 then
351 Loop_Required := True;
353 -- Case where no slice is involved
355 elsif not L_Slice and not R_Slice then
357 -- The following code deals with the case of unconstrained bit
358 -- packed arrays. The problem is that the template for such
359 -- arrays contains the bounds of the actual source level array,
361 -- But the copy of an entire array requires the bounds of the
362 -- underlying array. It would be nice if the back end could take
363 -- care of this, but right now it does not know how, so if we
364 -- have such a type, then we expand out into a loop, which is
365 -- inefficient but works correctly. If we don't do this, we
366 -- get the wrong length computed for the array to be moved.
367 -- The two cases we need to worry about are:
369 -- Explicit deference of an unconstrained packed array type as
370 -- in the following example:
372 -- procedure C52 is
373 -- type BITS is array(INTEGER range <>) of BOOLEAN;
374 -- pragma PACK(BITS);
375 -- type A is access BITS;
376 -- P1,P2 : A;
377 -- begin
378 -- P1 := new BITS (1 .. 65_535);
379 -- P2 := new BITS (1 .. 65_535);
380 -- P2.ALL := P1.ALL;
381 -- end C52;
383 -- A formal parameter reference with an unconstrained bit
384 -- array type is the other case we need to worry about (here
385 -- we assume the same BITS type declared above:
387 -- procedure Write_All (File : out BITS; Contents : in BITS);
388 -- begin
389 -- File.Storage := Contents;
390 -- end Write_All;
392 -- We expand to a loop in either of these two cases
394 -- Question for future thought. Another potentially more efficient
395 -- approach would be to create the actual subtype, and then do an
396 -- unchecked conversion to this actual subtype ???
398 Check_Unconstrained_Bit_Packed_Array : declare
400 function Is_UBPA_Reference (Opnd : Node_Id) return Boolean;
401 -- Function to perform required test for the first case,
402 -- above (dereference of an unconstrained bit packed array)
404 -----------------------
405 -- Is_UBPA_Reference --
406 -----------------------
408 function Is_UBPA_Reference (Opnd : Node_Id) return Boolean is
409 Typ : constant Entity_Id := Underlying_Type (Etype (Opnd));
410 P_Type : Entity_Id;
411 Des_Type : Entity_Id;
413 begin
414 if Present (Packed_Array_Type (Typ))
415 and then Is_Array_Type (Packed_Array_Type (Typ))
416 and then not Is_Constrained (Packed_Array_Type (Typ))
417 then
418 return True;
420 elsif Nkind (Opnd) = N_Explicit_Dereference then
421 P_Type := Underlying_Type (Etype (Prefix (Opnd)));
423 if not Is_Access_Type (P_Type) then
424 return False;
426 else
427 Des_Type := Designated_Type (P_Type);
428 return
429 Is_Bit_Packed_Array (Des_Type)
430 and then not Is_Constrained (Des_Type);
431 end if;
433 else
434 return False;
435 end if;
436 end Is_UBPA_Reference;
438 -- Start of processing for Check_Unconstrained_Bit_Packed_Array
440 begin
441 if Is_UBPA_Reference (Lhs)
442 or else
443 Is_UBPA_Reference (Rhs)
444 then
445 Loop_Required := True;
447 -- Here if we do not have the case of a reference to a bit
448 -- packed unconstrained array case. In this case gigi can
449 -- most certainly handle the assignment if a forwards move
450 -- is allowed.
452 -- (could it handle the backwards case also???)
454 elsif Forwards_OK (N) then
455 return;
456 end if;
457 end Check_Unconstrained_Bit_Packed_Array;
459 -- The back end can always handle the assignment if the right side is a
460 -- string literal (note that overlap is definitely impossible in this
461 -- case). If the type is packed, a string literal is always converted
462 -- into aggregate, except in the case of a null slice, for which no
463 -- aggregate can be written. In that case, rewrite the assignment as a
464 -- null statement, a length check has already been emitted to verify
465 -- that the range of the left-hand side is empty.
467 -- Note that this code is not executed if we had an assignment of
468 -- a string literal to a non-bit aligned component of a record, a
469 -- case which cannot be handled by the backend
471 elsif Nkind (Rhs) = N_String_Literal then
472 if String_Length (Strval (Rhs)) = 0
473 and then Is_Bit_Packed_Array (L_Type)
474 then
475 Rewrite (N, Make_Null_Statement (Loc));
476 Analyze (N);
477 end if;
479 return;
481 -- If either operand is bit packed, then we need a loop, since we
482 -- can't be sure that the slice is byte aligned. Similarly, if either
483 -- operand is a possibly unaligned slice, then we need a loop (since
484 -- the back end cannot handle unaligned slices).
486 elsif Is_Bit_Packed_Array (L_Type)
487 or else Is_Bit_Packed_Array (R_Type)
488 or else Is_Possibly_Unaligned_Slice (Lhs)
489 or else Is_Possibly_Unaligned_Slice (Rhs)
490 then
491 Loop_Required := True;
493 -- If we are not bit-packed, and we have only one slice, then no
494 -- overlap is possible except in the parameter case, so we can let
495 -- the back end handle things.
497 elsif not (L_Slice and R_Slice) then
498 if Forwards_OK (N) then
499 return;
500 end if;
501 end if;
503 -- If the right-hand side is a string literal, introduce a temporary
504 -- for it, for use in the generated loop that will follow.
506 if Nkind (Rhs) = N_String_Literal then
507 declare
508 Temp : constant Entity_Id :=
509 Make_Defining_Identifier (Loc, New_Internal_Name ('T'));
510 Decl : Node_Id;
512 begin
513 Decl :=
514 Make_Object_Declaration (Loc,
515 Defining_Identifier => Temp,
516 Object_Definition => New_Occurrence_Of (L_Type, Loc),
517 Expression => Relocate_Node (Rhs));
519 Insert_Action (N, Decl);
520 Rewrite (Rhs, New_Occurrence_Of (Temp, Loc));
521 R_Type := Etype (Temp);
522 end;
523 end if;
525 -- Come here to complete the analysis
527 -- Loop_Required: Set to True if we know that a loop is required
528 -- regardless of overlap considerations.
530 -- Forwards_OK: Set to False if we already know that a forwards
531 -- move is not safe, else set to True.
533 -- Backwards_OK: Set to False if we already know that a backwards
534 -- move is not safe, else set to True
536 -- Our task at this stage is to complete the overlap analysis, which
537 -- can result in possibly setting Forwards_OK or Backwards_OK to
538 -- False, and then generating the final code, either by deciding
539 -- that it is OK after all to let Gigi handle it, or by generating
540 -- appropriate code in the front end.
542 declare
543 L_Index_Typ : constant Node_Id := Etype (First_Index (L_Type));
544 R_Index_Typ : constant Node_Id := Etype (First_Index (R_Type));
546 Left_Lo : constant Node_Id := Type_Low_Bound (L_Index_Typ);
547 Left_Hi : constant Node_Id := Type_High_Bound (L_Index_Typ);
548 Right_Lo : constant Node_Id := Type_Low_Bound (R_Index_Typ);
549 Right_Hi : constant Node_Id := Type_High_Bound (R_Index_Typ);
551 Act_L_Array : Node_Id;
552 Act_R_Array : Node_Id;
554 Cleft_Lo : Node_Id;
555 Cright_Lo : Node_Id;
556 Condition : Node_Id;
558 Cresult : Compare_Result;
560 begin
561 -- Get the expressions for the arrays. If we are dealing with a
562 -- private type, then convert to the underlying type. We can do
563 -- direct assignments to an array that is a private type, but
564 -- we cannot assign to elements of the array without this extra
565 -- unchecked conversion.
567 if Nkind (Act_Lhs) = N_Slice then
568 Larray := Prefix (Act_Lhs);
569 else
570 Larray := Act_Lhs;
572 if Is_Private_Type (Etype (Larray)) then
573 Larray :=
574 Unchecked_Convert_To
575 (Underlying_Type (Etype (Larray)), Larray);
576 end if;
577 end if;
579 if Nkind (Act_Rhs) = N_Slice then
580 Rarray := Prefix (Act_Rhs);
581 else
582 Rarray := Act_Rhs;
584 if Is_Private_Type (Etype (Rarray)) then
585 Rarray :=
586 Unchecked_Convert_To
587 (Underlying_Type (Etype (Rarray)), Rarray);
588 end if;
589 end if;
591 -- If both sides are slices, we must figure out whether
592 -- it is safe to do the move in one direction or the other
593 -- It is always safe if there is a change of representation
594 -- since obviously two arrays with different representations
595 -- cannot possibly overlap.
597 if (not Crep) and L_Slice and R_Slice then
598 Act_L_Array := Get_Referenced_Object (Prefix (Act_Lhs));
599 Act_R_Array := Get_Referenced_Object (Prefix (Act_Rhs));
601 -- If both left and right hand arrays are entity names, and
602 -- refer to different entities, then we know that the move
603 -- is safe (the two storage areas are completely disjoint).
605 if Is_Entity_Name (Act_L_Array)
606 and then Is_Entity_Name (Act_R_Array)
607 and then Entity (Act_L_Array) /= Entity (Act_R_Array)
608 then
609 null;
611 -- Otherwise, we assume the worst, which is that the two
612 -- arrays are the same array. There is no need to check if
613 -- we know that is the case, because if we don't know it,
614 -- we still have to assume it!
616 -- Generally if the same array is involved, then we have
617 -- an overlapping case. We will have to really assume the
618 -- worst (i.e. set neither of the OK flags) unless we can
619 -- determine the lower or upper bounds at compile time and
620 -- compare them.
622 else
623 Cresult := Compile_Time_Compare (Left_Lo, Right_Lo);
625 if Cresult = Unknown then
626 Cresult := Compile_Time_Compare (Left_Hi, Right_Hi);
627 end if;
629 case Cresult is
630 when LT | LE | EQ => Set_Backwards_OK (N, False);
631 when GT | GE => Set_Forwards_OK (N, False);
632 when NE | Unknown => Set_Backwards_OK (N, False);
633 Set_Forwards_OK (N, False);
634 end case;
635 end if;
636 end if;
638 -- If after that analysis, Forwards_OK is still True, and
639 -- Loop_Required is False, meaning that we have not discovered
640 -- some non-overlap reason for requiring a loop, then we can
641 -- still let gigi handle it.
643 if not Loop_Required then
644 if Forwards_OK (N) then
645 return;
646 else
647 null;
648 -- Here is where a memmove would be appropriate ???
649 end if;
650 end if;
652 -- At this stage we have to generate an explicit loop, and
653 -- we have the following cases:
655 -- Forwards_OK = True
657 -- Rnn : right_index := right_index'First;
658 -- for Lnn in left-index loop
659 -- left (Lnn) := right (Rnn);
660 -- Rnn := right_index'Succ (Rnn);
661 -- end loop;
663 -- Note: the above code MUST be analyzed with checks off,
664 -- because otherwise the Succ could overflow. But in any
665 -- case this is more efficient!
667 -- Forwards_OK = False, Backwards_OK = True
669 -- Rnn : right_index := right_index'Last;
670 -- for Lnn in reverse left-index loop
671 -- left (Lnn) := right (Rnn);
672 -- Rnn := right_index'Pred (Rnn);
673 -- end loop;
675 -- Note: the above code MUST be analyzed with checks off,
676 -- because otherwise the Pred could overflow. But in any
677 -- case this is more efficient!
679 -- Forwards_OK = Backwards_OK = False
681 -- This only happens if we have the same array on each side. It is
682 -- possible to create situations using overlays that violate this,
683 -- but we simply do not promise to get this "right" in this case.
685 -- There are two possible subcases. If the No_Implicit_Conditionals
686 -- restriction is set, then we generate the following code:
688 -- declare
689 -- T : constant <operand-type> := rhs;
690 -- begin
691 -- lhs := T;
692 -- end;
694 -- If implicit conditionals are permitted, then we generate:
696 -- if Left_Lo <= Right_Lo then
697 -- <code for Forwards_OK = True above>
698 -- else
699 -- <code for Backwards_OK = True above>
700 -- end if;
702 -- Cases where either Forwards_OK or Backwards_OK is true
704 if Forwards_OK (N) or else Backwards_OK (N) then
705 if Controlled_Type (Component_Type (L_Type))
706 and then Base_Type (L_Type) = Base_Type (R_Type)
707 and then Ndim = 1
708 and then not No_Ctrl_Actions (N)
709 then
710 declare
711 Proc : constant Entity_Id :=
712 TSS (Base_Type (L_Type), TSS_Slice_Assign);
713 Actuals : List_Id;
715 begin
716 Apply_Dereference (Larray);
717 Apply_Dereference (Rarray);
718 Actuals := New_List (
719 Duplicate_Subexpr (Larray, Name_Req => True),
720 Duplicate_Subexpr (Rarray, Name_Req => True),
721 Duplicate_Subexpr (Left_Lo, Name_Req => True),
722 Duplicate_Subexpr (Left_Hi, Name_Req => True),
723 Duplicate_Subexpr (Right_Lo, Name_Req => True),
724 Duplicate_Subexpr (Right_Hi, Name_Req => True));
726 Append_To (Actuals,
727 New_Occurrence_Of (
728 Boolean_Literals (not Forwards_OK (N)), Loc));
730 Rewrite (N,
731 Make_Procedure_Call_Statement (Loc,
732 Name => New_Reference_To (Proc, Loc),
733 Parameter_Associations => Actuals));
734 end;
736 else
737 Rewrite (N,
738 Expand_Assign_Array_Loop
739 (N, Larray, Rarray, L_Type, R_Type, Ndim,
740 Rev => not Forwards_OK (N)));
741 end if;
743 -- Case of both are false with No_Implicit_Conditionals
745 elsif Restriction_Active (No_Implicit_Conditionals) then
746 declare
747 T : constant Entity_Id :=
748 Make_Defining_Identifier (Loc, Chars => Name_T);
750 begin
751 Rewrite (N,
752 Make_Block_Statement (Loc,
753 Declarations => New_List (
754 Make_Object_Declaration (Loc,
755 Defining_Identifier => T,
756 Constant_Present => True,
757 Object_Definition =>
758 New_Occurrence_Of (Etype (Rhs), Loc),
759 Expression => Relocate_Node (Rhs))),
761 Handled_Statement_Sequence =>
762 Make_Handled_Sequence_Of_Statements (Loc,
763 Statements => New_List (
764 Make_Assignment_Statement (Loc,
765 Name => Relocate_Node (Lhs),
766 Expression => New_Occurrence_Of (T, Loc))))));
767 end;
769 -- Case of both are false with implicit conditionals allowed
771 else
772 -- Before we generate this code, we must ensure that the
773 -- left and right side array types are defined. They may
774 -- be itypes, and we cannot let them be defined inside the
775 -- if, since the first use in the then may not be executed.
777 Ensure_Defined (L_Type, N);
778 Ensure_Defined (R_Type, N);
780 -- We normally compare addresses to find out which way round
781 -- to do the loop, since this is realiable, and handles the
782 -- cases of parameters, conversions etc. But we can't do that
783 -- in the bit packed case or the Java VM case, because addresses
784 -- don't work there.
786 if not Is_Bit_Packed_Array (L_Type) and then not Java_VM then
787 Condition :=
788 Make_Op_Le (Loc,
789 Left_Opnd =>
790 Unchecked_Convert_To (RTE (RE_Integer_Address),
791 Make_Attribute_Reference (Loc,
792 Prefix =>
793 Make_Indexed_Component (Loc,
794 Prefix =>
795 Duplicate_Subexpr_Move_Checks (Larray, True),
796 Expressions => New_List (
797 Make_Attribute_Reference (Loc,
798 Prefix =>
799 New_Reference_To
800 (L_Index_Typ, Loc),
801 Attribute_Name => Name_First))),
802 Attribute_Name => Name_Address)),
804 Right_Opnd =>
805 Unchecked_Convert_To (RTE (RE_Integer_Address),
806 Make_Attribute_Reference (Loc,
807 Prefix =>
808 Make_Indexed_Component (Loc,
809 Prefix =>
810 Duplicate_Subexpr_Move_Checks (Rarray, True),
811 Expressions => New_List (
812 Make_Attribute_Reference (Loc,
813 Prefix =>
814 New_Reference_To
815 (R_Index_Typ, Loc),
816 Attribute_Name => Name_First))),
817 Attribute_Name => Name_Address)));
819 -- For the bit packed and Java VM cases we use the bounds.
820 -- That's OK, because we don't have to worry about parameters,
821 -- since they cannot cause overlap. Perhaps we should worry
822 -- about weird slice conversions ???
824 else
825 -- Copy the bounds and reset the Analyzed flag, because the
826 -- bounds of the index type itself may be universal, and must
827 -- must be reaanalyzed to acquire the proper type for Gigi.
829 Cleft_Lo := New_Copy_Tree (Left_Lo);
830 Cright_Lo := New_Copy_Tree (Right_Lo);
831 Set_Analyzed (Cleft_Lo, False);
832 Set_Analyzed (Cright_Lo, False);
834 Condition :=
835 Make_Op_Le (Loc,
836 Left_Opnd => Cleft_Lo,
837 Right_Opnd => Cright_Lo);
838 end if;
840 if Controlled_Type (Component_Type (L_Type))
841 and then Base_Type (L_Type) = Base_Type (R_Type)
842 and then Ndim = 1
843 and then not No_Ctrl_Actions (N)
844 then
846 -- Call TSS procedure for array assignment, passing the
847 -- the explicit bounds of right and left hand sides.
849 declare
850 Proc : constant Node_Id :=
851 TSS (Base_Type (L_Type), TSS_Slice_Assign);
852 Actuals : List_Id;
854 begin
855 Apply_Dereference (Larray);
856 Apply_Dereference (Rarray);
857 Actuals := New_List (
858 Duplicate_Subexpr (Larray, Name_Req => True),
859 Duplicate_Subexpr (Rarray, Name_Req => True),
860 Duplicate_Subexpr (Left_Lo, Name_Req => True),
861 Duplicate_Subexpr (Left_Hi, Name_Req => True),
862 Duplicate_Subexpr (Right_Lo, Name_Req => True),
863 Duplicate_Subexpr (Right_Hi, Name_Req => True));
865 Append_To (Actuals,
866 Make_Op_Not (Loc,
867 Right_Opnd => Condition));
869 Rewrite (N,
870 Make_Procedure_Call_Statement (Loc,
871 Name => New_Reference_To (Proc, Loc),
872 Parameter_Associations => Actuals));
873 end;
875 else
876 Rewrite (N,
877 Make_Implicit_If_Statement (N,
878 Condition => Condition,
880 Then_Statements => New_List (
881 Expand_Assign_Array_Loop
882 (N, Larray, Rarray, L_Type, R_Type, Ndim,
883 Rev => False)),
885 Else_Statements => New_List (
886 Expand_Assign_Array_Loop
887 (N, Larray, Rarray, L_Type, R_Type, Ndim,
888 Rev => True))));
889 end if;
890 end if;
892 Analyze (N, Suppress => All_Checks);
893 end;
895 exception
896 when RE_Not_Available =>
897 return;
898 end Expand_Assign_Array;
900 ------------------------------
901 -- Expand_Assign_Array_Loop --
902 ------------------------------
904 -- The following is an example of the loop generated for the case of
905 -- a two-dimensional array:
907 -- declare
908 -- R2b : Tm1X1 := 1;
909 -- begin
910 -- for L1b in 1 .. 100 loop
911 -- declare
912 -- R4b : Tm1X2 := 1;
913 -- begin
914 -- for L3b in 1 .. 100 loop
915 -- vm1 (L1b, L3b) := vm2 (R2b, R4b);
916 -- R4b := Tm1X2'succ(R4b);
917 -- end loop;
918 -- end;
919 -- R2b := Tm1X1'succ(R2b);
920 -- end loop;
921 -- end;
923 -- Here Rev is False, and Tm1Xn are the subscript types for the right
924 -- hand side. The declarations of R2b and R4b are inserted before the
925 -- original assignment statement.
927 function Expand_Assign_Array_Loop
928 (N : Node_Id;
929 Larray : Entity_Id;
930 Rarray : Entity_Id;
931 L_Type : Entity_Id;
932 R_Type : Entity_Id;
933 Ndim : Pos;
934 Rev : Boolean) return Node_Id
936 Loc : constant Source_Ptr := Sloc (N);
938 Lnn : array (1 .. Ndim) of Entity_Id;
939 Rnn : array (1 .. Ndim) of Entity_Id;
940 -- Entities used as subscripts on left and right sides
942 L_Index_Type : array (1 .. Ndim) of Entity_Id;
943 R_Index_Type : array (1 .. Ndim) of Entity_Id;
944 -- Left and right index types
946 Assign : Node_Id;
948 F_Or_L : Name_Id;
949 S_Or_P : Name_Id;
951 begin
952 if Rev then
953 F_Or_L := Name_Last;
954 S_Or_P := Name_Pred;
955 else
956 F_Or_L := Name_First;
957 S_Or_P := Name_Succ;
958 end if;
960 -- Setup index types and subscript entities
962 declare
963 L_Index : Node_Id;
964 R_Index : Node_Id;
966 begin
967 L_Index := First_Index (L_Type);
968 R_Index := First_Index (R_Type);
970 for J in 1 .. Ndim loop
971 Lnn (J) :=
972 Make_Defining_Identifier (Loc,
973 Chars => New_Internal_Name ('L'));
975 Rnn (J) :=
976 Make_Defining_Identifier (Loc,
977 Chars => New_Internal_Name ('R'));
979 L_Index_Type (J) := Etype (L_Index);
980 R_Index_Type (J) := Etype (R_Index);
982 Next_Index (L_Index);
983 Next_Index (R_Index);
984 end loop;
985 end;
987 -- Now construct the assignment statement
989 declare
990 ExprL : constant List_Id := New_List;
991 ExprR : constant List_Id := New_List;
993 begin
994 for J in 1 .. Ndim loop
995 Append_To (ExprL, New_Occurrence_Of (Lnn (J), Loc));
996 Append_To (ExprR, New_Occurrence_Of (Rnn (J), Loc));
997 end loop;
999 Assign :=
1000 Make_Assignment_Statement (Loc,
1001 Name =>
1002 Make_Indexed_Component (Loc,
1003 Prefix => Duplicate_Subexpr (Larray, Name_Req => True),
1004 Expressions => ExprL),
1005 Expression =>
1006 Make_Indexed_Component (Loc,
1007 Prefix => Duplicate_Subexpr (Rarray, Name_Req => True),
1008 Expressions => ExprR));
1010 -- We set assignment OK, since there are some cases, e.g. in object
1011 -- declarations, where we are actually assigning into a constant.
1012 -- If there really is an illegality, it was caught long before now,
1013 -- and was flagged when the original assignment was analyzed.
1015 Set_Assignment_OK (Name (Assign));
1017 -- Propagate the No_Ctrl_Actions flag to individual assignments
1019 Set_No_Ctrl_Actions (Assign, No_Ctrl_Actions (N));
1020 end;
1022 -- Now construct the loop from the inside out, with the last subscript
1023 -- varying most rapidly. Note that Assign is first the raw assignment
1024 -- statement, and then subsequently the loop that wraps it up.
1026 for J in reverse 1 .. Ndim loop
1027 Assign :=
1028 Make_Block_Statement (Loc,
1029 Declarations => New_List (
1030 Make_Object_Declaration (Loc,
1031 Defining_Identifier => Rnn (J),
1032 Object_Definition =>
1033 New_Occurrence_Of (R_Index_Type (J), Loc),
1034 Expression =>
1035 Make_Attribute_Reference (Loc,
1036 Prefix => New_Occurrence_Of (R_Index_Type (J), Loc),
1037 Attribute_Name => F_Or_L))),
1039 Handled_Statement_Sequence =>
1040 Make_Handled_Sequence_Of_Statements (Loc,
1041 Statements => New_List (
1042 Make_Implicit_Loop_Statement (N,
1043 Iteration_Scheme =>
1044 Make_Iteration_Scheme (Loc,
1045 Loop_Parameter_Specification =>
1046 Make_Loop_Parameter_Specification (Loc,
1047 Defining_Identifier => Lnn (J),
1048 Reverse_Present => Rev,
1049 Discrete_Subtype_Definition =>
1050 New_Reference_To (L_Index_Type (J), Loc))),
1052 Statements => New_List (
1053 Assign,
1055 Make_Assignment_Statement (Loc,
1056 Name => New_Occurrence_Of (Rnn (J), Loc),
1057 Expression =>
1058 Make_Attribute_Reference (Loc,
1059 Prefix =>
1060 New_Occurrence_Of (R_Index_Type (J), Loc),
1061 Attribute_Name => S_Or_P,
1062 Expressions => New_List (
1063 New_Occurrence_Of (Rnn (J), Loc)))))))));
1064 end loop;
1066 return Assign;
1067 end Expand_Assign_Array_Loop;
1069 --------------------------
1070 -- Expand_Assign_Record --
1071 --------------------------
1073 -- The only processing required is in the change of representation
1074 -- case, where we must expand the assignment to a series of field
1075 -- by field assignments.
1077 procedure Expand_Assign_Record (N : Node_Id) is
1078 Lhs : constant Node_Id := Name (N);
1079 Rhs : Node_Id := Expression (N);
1081 begin
1082 -- If change of representation, then extract the real right hand
1083 -- side from the type conversion, and proceed with component-wise
1084 -- assignment, since the two types are not the same as far as the
1085 -- back end is concerned.
1087 if Change_Of_Representation (N) then
1088 Rhs := Expression (Rhs);
1090 -- If this may be a case of a large bit aligned component, then
1091 -- proceed with component-wise assignment, to avoid possible
1092 -- clobbering of other components sharing bits in the first or
1093 -- last byte of the component to be assigned.
1095 elsif Possible_Bit_Aligned_Component (Lhs)
1097 Possible_Bit_Aligned_Component (Rhs)
1098 then
1099 null;
1101 -- If neither condition met, then nothing special to do, the back end
1102 -- can handle assignment of the entire component as a single entity.
1104 else
1105 return;
1106 end if;
1108 -- At this stage we know that we must do a component wise assignment
1110 declare
1111 Loc : constant Source_Ptr := Sloc (N);
1112 R_Typ : constant Entity_Id := Base_Type (Etype (Rhs));
1113 L_Typ : constant Entity_Id := Base_Type (Etype (Lhs));
1114 Decl : constant Node_Id := Declaration_Node (R_Typ);
1115 RDef : Node_Id;
1116 F : Entity_Id;
1118 function Find_Component
1119 (Typ : Entity_Id;
1120 Comp : Entity_Id) return Entity_Id;
1121 -- Find the component with the given name in the underlying record
1122 -- declaration for Typ. We need to use the actual entity because
1123 -- the type may be private and resolution by identifier alone would
1124 -- fail.
1126 function Make_Component_List_Assign
1127 (CL : Node_Id;
1128 U_U : Boolean := False) return List_Id;
1129 -- Returns a sequence of statements to assign the components that
1130 -- are referenced in the given component list. The flag U_U is
1131 -- used to force the usage of the inferred value of the variant
1132 -- part expression as the switch for the generated case statement.
1134 function Make_Field_Assign
1135 (C : Entity_Id;
1136 U_U : Boolean := False) return Node_Id;
1137 -- Given C, the entity for a discriminant or component, build an
1138 -- assignment for the corresponding field values. The flag U_U
1139 -- signals the presence of an Unchecked_Union and forces the usage
1140 -- of the inferred discriminant value of C as the right hand side
1141 -- of the assignment.
1143 function Make_Field_Assigns (CI : List_Id) return List_Id;
1144 -- Given CI, a component items list, construct series of statements
1145 -- for fieldwise assignment of the corresponding components.
1147 --------------------
1148 -- Find_Component --
1149 --------------------
1151 function Find_Component
1152 (Typ : Entity_Id;
1153 Comp : Entity_Id) return Entity_Id
1155 Utyp : constant Entity_Id := Underlying_Type (Typ);
1156 C : Entity_Id;
1158 begin
1159 C := First_Entity (Utyp);
1161 while Present (C) loop
1162 if Chars (C) = Chars (Comp) then
1163 return C;
1164 end if;
1165 Next_Entity (C);
1166 end loop;
1168 raise Program_Error;
1169 end Find_Component;
1171 --------------------------------
1172 -- Make_Component_List_Assign --
1173 --------------------------------
1175 function Make_Component_List_Assign
1176 (CL : Node_Id;
1177 U_U : Boolean := False) return List_Id
1179 CI : constant List_Id := Component_Items (CL);
1180 VP : constant Node_Id := Variant_Part (CL);
1182 Alts : List_Id;
1183 DC : Node_Id;
1184 DCH : List_Id;
1185 Expr : Node_Id;
1186 Result : List_Id;
1187 V : Node_Id;
1189 begin
1190 Result := Make_Field_Assigns (CI);
1192 if Present (VP) then
1194 V := First_Non_Pragma (Variants (VP));
1195 Alts := New_List;
1196 while Present (V) loop
1198 DCH := New_List;
1199 DC := First (Discrete_Choices (V));
1200 while Present (DC) loop
1201 Append_To (DCH, New_Copy_Tree (DC));
1202 Next (DC);
1203 end loop;
1205 Append_To (Alts,
1206 Make_Case_Statement_Alternative (Loc,
1207 Discrete_Choices => DCH,
1208 Statements =>
1209 Make_Component_List_Assign (Component_List (V))));
1210 Next_Non_Pragma (V);
1211 end loop;
1213 -- If we have an Unchecked_Union, use the value of the inferred
1214 -- discriminant of the variant part expression as the switch
1215 -- for the case statement. The case statement may later be
1216 -- folded.
1218 if U_U then
1219 Expr :=
1220 New_Copy (Get_Discriminant_Value (
1221 Entity (Name (VP)),
1222 Etype (Rhs),
1223 Discriminant_Constraint (Etype (Rhs))));
1224 else
1225 Expr :=
1226 Make_Selected_Component (Loc,
1227 Prefix => Duplicate_Subexpr (Rhs),
1228 Selector_Name =>
1229 Make_Identifier (Loc, Chars (Name (VP))));
1230 end if;
1232 Append_To (Result,
1233 Make_Case_Statement (Loc,
1234 Expression => Expr,
1235 Alternatives => Alts));
1236 end if;
1238 return Result;
1239 end Make_Component_List_Assign;
1241 -----------------------
1242 -- Make_Field_Assign --
1243 -----------------------
1245 function Make_Field_Assign
1246 (C : Entity_Id;
1247 U_U : Boolean := False) return Node_Id
1249 A : Node_Id;
1250 Expr : Node_Id;
1252 begin
1253 -- In the case of an Unchecked_Union, use the discriminant
1254 -- constraint value as on the right hand side of the assignment.
1256 if U_U then
1257 Expr :=
1258 New_Copy (Get_Discriminant_Value (C,
1259 Etype (Rhs),
1260 Discriminant_Constraint (Etype (Rhs))));
1261 else
1262 Expr :=
1263 Make_Selected_Component (Loc,
1264 Prefix => Duplicate_Subexpr (Rhs),
1265 Selector_Name => New_Occurrence_Of (C, Loc));
1266 end if;
1268 A :=
1269 Make_Assignment_Statement (Loc,
1270 Name =>
1271 Make_Selected_Component (Loc,
1272 Prefix => Duplicate_Subexpr (Lhs),
1273 Selector_Name =>
1274 New_Occurrence_Of (Find_Component (L_Typ, C), Loc)),
1275 Expression => Expr);
1277 -- Set Assignment_OK, so discriminants can be assigned
1279 Set_Assignment_OK (Name (A), True);
1280 return A;
1281 end Make_Field_Assign;
1283 ------------------------
1284 -- Make_Field_Assigns --
1285 ------------------------
1287 function Make_Field_Assigns (CI : List_Id) return List_Id is
1288 Item : Node_Id;
1289 Result : List_Id;
1291 begin
1292 Item := First (CI);
1293 Result := New_List;
1294 while Present (Item) loop
1295 if Nkind (Item) = N_Component_Declaration then
1296 Append_To
1297 (Result, Make_Field_Assign (Defining_Identifier (Item)));
1298 end if;
1300 Next (Item);
1301 end loop;
1303 return Result;
1304 end Make_Field_Assigns;
1306 -- Start of processing for Expand_Assign_Record
1308 begin
1309 -- Note that we use the base types for this processing. This results
1310 -- in some extra work in the constrained case, but the change of
1311 -- representation case is so unusual that it is not worth the effort.
1313 -- First copy the discriminants. This is done unconditionally. It
1314 -- is required in the unconstrained left side case, and also in the
1315 -- case where this assignment was constructed during the expansion
1316 -- of a type conversion (since initialization of discriminants is
1317 -- suppressed in this case). It is unnecessary but harmless in
1318 -- other cases.
1320 if Has_Discriminants (L_Typ) then
1321 F := First_Discriminant (R_Typ);
1322 while Present (F) loop
1324 if Is_Unchecked_Union (Base_Type (R_Typ)) then
1325 Insert_Action (N, Make_Field_Assign (F, True));
1326 else
1327 Insert_Action (N, Make_Field_Assign (F));
1328 end if;
1330 Next_Discriminant (F);
1331 end loop;
1332 end if;
1334 -- We know the underlying type is a record, but its current view
1335 -- may be private. We must retrieve the usable record declaration.
1337 if Nkind (Decl) = N_Private_Type_Declaration
1338 and then Present (Full_View (R_Typ))
1339 then
1340 RDef := Type_Definition (Declaration_Node (Full_View (R_Typ)));
1341 else
1342 RDef := Type_Definition (Decl);
1343 end if;
1345 if Nkind (RDef) = N_Record_Definition
1346 and then Present (Component_List (RDef))
1347 then
1349 if Is_Unchecked_Union (R_Typ) then
1350 Insert_Actions (N,
1351 Make_Component_List_Assign (Component_List (RDef), True));
1352 else
1353 Insert_Actions
1354 (N, Make_Component_List_Assign (Component_List (RDef)));
1355 end if;
1357 Rewrite (N, Make_Null_Statement (Loc));
1358 end if;
1360 end;
1361 end Expand_Assign_Record;
1363 -----------------------------------
1364 -- Expand_N_Assignment_Statement --
1365 -----------------------------------
1367 -- This procedure implements various cases where an assignment statement
1368 -- cannot just be passed on to the back end in untransformed state.
1370 procedure Expand_N_Assignment_Statement (N : Node_Id) is
1371 Loc : constant Source_Ptr := Sloc (N);
1372 Lhs : constant Node_Id := Name (N);
1373 Rhs : constant Node_Id := Expression (N);
1374 Typ : constant Entity_Id := Underlying_Type (Etype (Lhs));
1375 Exp : Node_Id;
1377 begin
1378 -- First deal with generation of range check if required. For now
1379 -- we do this only for discrete types.
1381 if Do_Range_Check (Rhs)
1382 and then Is_Discrete_Type (Typ)
1383 then
1384 Set_Do_Range_Check (Rhs, False);
1385 Generate_Range_Check (Rhs, Typ, CE_Range_Check_Failed);
1386 end if;
1388 -- Check for a special case where a high level transformation is
1389 -- required. If we have either of:
1391 -- P.field := rhs;
1392 -- P (sub) := rhs;
1394 -- where P is a reference to a bit packed array, then we have to unwind
1395 -- the assignment. The exact meaning of being a reference to a bit
1396 -- packed array is as follows:
1398 -- An indexed component whose prefix is a bit packed array is a
1399 -- reference to a bit packed array.
1401 -- An indexed component or selected component whose prefix is a
1402 -- reference to a bit packed array is itself a reference ot a
1403 -- bit packed array.
1405 -- The required transformation is
1407 -- Tnn : prefix_type := P;
1408 -- Tnn.field := rhs;
1409 -- P := Tnn;
1411 -- or
1413 -- Tnn : prefix_type := P;
1414 -- Tnn (subscr) := rhs;
1415 -- P := Tnn;
1417 -- Since P is going to be evaluated more than once, any subscripts
1418 -- in P must have their evaluation forced.
1420 if (Nkind (Lhs) = N_Indexed_Component
1421 or else
1422 Nkind (Lhs) = N_Selected_Component)
1423 and then Is_Ref_To_Bit_Packed_Array (Prefix (Lhs))
1424 then
1425 declare
1426 BPAR_Expr : constant Node_Id := Relocate_Node (Prefix (Lhs));
1427 BPAR_Typ : constant Entity_Id := Etype (BPAR_Expr);
1428 Tnn : constant Entity_Id :=
1429 Make_Defining_Identifier (Loc,
1430 Chars => New_Internal_Name ('T'));
1432 begin
1433 -- Insert the post assignment first, because we want to copy
1434 -- the BPAR_Expr tree before it gets analyzed in the context
1435 -- of the pre assignment. Note that we do not analyze the
1436 -- post assignment yet (we cannot till we have completed the
1437 -- analysis of the pre assignment). As usual, the analysis
1438 -- of this post assignment will happen on its own when we
1439 -- "run into" it after finishing the current assignment.
1441 Insert_After (N,
1442 Make_Assignment_Statement (Loc,
1443 Name => New_Copy_Tree (BPAR_Expr),
1444 Expression => New_Occurrence_Of (Tnn, Loc)));
1446 -- At this stage BPAR_Expr is a reference to a bit packed
1447 -- array where the reference was not expanded in the original
1448 -- tree, since it was on the left side of an assignment. But
1449 -- in the pre-assignment statement (the object definition),
1450 -- BPAR_Expr will end up on the right hand side, and must be
1451 -- reexpanded. To achieve this, we reset the analyzed flag
1452 -- of all selected and indexed components down to the actual
1453 -- indexed component for the packed array.
1455 Exp := BPAR_Expr;
1456 loop
1457 Set_Analyzed (Exp, False);
1459 if Nkind (Exp) = N_Selected_Component
1460 or else
1461 Nkind (Exp) = N_Indexed_Component
1462 then
1463 Exp := Prefix (Exp);
1464 else
1465 exit;
1466 end if;
1467 end loop;
1469 -- Now we can insert and analyze the pre-assignment
1471 -- If the right-hand side requires a transient scope, it has
1472 -- already been placed on the stack. However, the declaration is
1473 -- inserted in the tree outside of this scope, and must reflect
1474 -- the proper scope for its variable. This awkward bit is forced
1475 -- by the stricter scope discipline imposed by GCC 2.97.
1477 declare
1478 Uses_Transient_Scope : constant Boolean :=
1479 Scope_Is_Transient
1480 and then N = Node_To_Be_Wrapped;
1482 begin
1483 if Uses_Transient_Scope then
1484 New_Scope (Scope (Current_Scope));
1485 end if;
1487 Insert_Before_And_Analyze (N,
1488 Make_Object_Declaration (Loc,
1489 Defining_Identifier => Tnn,
1490 Object_Definition => New_Occurrence_Of (BPAR_Typ, Loc),
1491 Expression => BPAR_Expr));
1493 if Uses_Transient_Scope then
1494 Pop_Scope;
1495 end if;
1496 end;
1498 -- Now fix up the original assignment and continue processing
1500 Rewrite (Prefix (Lhs),
1501 New_Occurrence_Of (Tnn, Loc));
1503 -- We do not need to reanalyze that assignment, and we do not need
1504 -- to worry about references to the temporary, but we do need to
1505 -- make sure that the temporary is not marked as a true constant
1506 -- since we now have a generate assignment to it!
1508 Set_Is_True_Constant (Tnn, False);
1509 end;
1510 end if;
1512 -- When we have the appropriate type of aggregate in the
1513 -- expression (it has been determined during analysis of the
1514 -- aggregate by setting the delay flag), let's perform in place
1515 -- assignment and thus avoid creating a temporay.
1517 if Is_Delayed_Aggregate (Rhs) then
1518 Convert_Aggr_In_Assignment (N);
1519 Rewrite (N, Make_Null_Statement (Loc));
1520 Analyze (N);
1521 return;
1522 end if;
1524 -- Apply discriminant check if required. If Lhs is an access type
1525 -- to a designated type with discriminants, we must always check.
1527 if Has_Discriminants (Etype (Lhs)) then
1529 -- Skip discriminant check if change of representation. Will be
1530 -- done when the change of representation is expanded out.
1532 if not Change_Of_Representation (N) then
1533 Apply_Discriminant_Check (Rhs, Etype (Lhs), Lhs);
1534 end if;
1536 -- If the type is private without discriminants, and the full type
1537 -- has discriminants (necessarily with defaults) a check may still be
1538 -- necessary if the Lhs is aliased. The private determinants must be
1539 -- visible to build the discriminant constraints.
1541 -- Only an explicit dereference that comes from source indicates
1542 -- aliasing. Access to formals of protected operations and entries
1543 -- create dereferences but are not semantic aliasings.
1545 elsif Is_Private_Type (Etype (Lhs))
1546 and then Has_Discriminants (Typ)
1547 and then Nkind (Lhs) = N_Explicit_Dereference
1548 and then Comes_From_Source (Lhs)
1549 then
1550 declare
1551 Lt : constant Entity_Id := Etype (Lhs);
1552 begin
1553 Set_Etype (Lhs, Typ);
1554 Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs));
1555 Apply_Discriminant_Check (Rhs, Typ, Lhs);
1556 Set_Etype (Lhs, Lt);
1557 end;
1559 -- If the Lhs has a private type with unknown discriminants, it
1560 -- may have a full view with discriminants, but those are nameable
1561 -- only in the underlying type, so convert the Rhs to it before
1562 -- potential checking.
1564 elsif Has_Unknown_Discriminants (Base_Type (Etype (Lhs)))
1565 and then Has_Discriminants (Typ)
1566 then
1567 Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs));
1568 Apply_Discriminant_Check (Rhs, Typ, Lhs);
1570 -- In the access type case, we need the same discriminant check,
1571 -- and also range checks if we have an access to constrained array.
1573 elsif Is_Access_Type (Etype (Lhs))
1574 and then Is_Constrained (Designated_Type (Etype (Lhs)))
1575 then
1576 if Has_Discriminants (Designated_Type (Etype (Lhs))) then
1578 -- Skip discriminant check if change of representation. Will be
1579 -- done when the change of representation is expanded out.
1581 if not Change_Of_Representation (N) then
1582 Apply_Discriminant_Check (Rhs, Etype (Lhs));
1583 end if;
1585 elsif Is_Array_Type (Designated_Type (Etype (Lhs))) then
1586 Apply_Range_Check (Rhs, Etype (Lhs));
1588 if Is_Constrained (Etype (Lhs)) then
1589 Apply_Length_Check (Rhs, Etype (Lhs));
1590 end if;
1592 if Nkind (Rhs) = N_Allocator then
1593 declare
1594 Target_Typ : constant Entity_Id := Etype (Expression (Rhs));
1595 C_Es : Check_Result;
1597 begin
1598 C_Es :=
1599 Range_Check
1600 (Lhs,
1601 Target_Typ,
1602 Etype (Designated_Type (Etype (Lhs))));
1604 Insert_Range_Checks
1605 (C_Es,
1607 Target_Typ,
1608 Sloc (Lhs),
1609 Lhs);
1610 end;
1611 end if;
1612 end if;
1614 -- Apply range check for access type case
1616 elsif Is_Access_Type (Etype (Lhs))
1617 and then Nkind (Rhs) = N_Allocator
1618 and then Nkind (Expression (Rhs)) = N_Qualified_Expression
1619 then
1620 Analyze_And_Resolve (Expression (Rhs));
1621 Apply_Range_Check
1622 (Expression (Rhs), Designated_Type (Etype (Lhs)));
1623 end if;
1625 -- Ada 2005 (AI-231): Generate the run-time check
1627 if Is_Access_Type (Typ)
1628 and then Can_Never_Be_Null (Etype (Lhs))
1629 and then not Can_Never_Be_Null (Etype (Rhs))
1630 then
1631 Apply_Constraint_Check (Rhs, Etype (Lhs));
1632 end if;
1634 -- Case of assignment to a bit packed array element
1636 if Nkind (Lhs) = N_Indexed_Component
1637 and then Is_Bit_Packed_Array (Etype (Prefix (Lhs)))
1638 then
1639 Expand_Bit_Packed_Element_Set (N);
1640 return;
1642 elsif Is_Tagged_Type (Typ)
1643 or else (Controlled_Type (Typ) and then not Is_Array_Type (Typ))
1644 then
1645 Tagged_Case : declare
1646 L : List_Id := No_List;
1647 Expand_Ctrl_Actions : constant Boolean := not No_Ctrl_Actions (N);
1649 begin
1650 -- In the controlled case, we need to make sure that function
1651 -- calls are evaluated before finalizing the target. In all
1652 -- cases, it makes the expansion easier if the side-effects
1653 -- are removed first.
1655 Remove_Side_Effects (Lhs);
1656 Remove_Side_Effects (Rhs);
1658 -- Avoid recursion in the mechanism
1660 Set_Analyzed (N);
1662 -- If dispatching assignment, we need to dispatch to _assign
1664 if Is_Class_Wide_Type (Typ)
1666 -- If the type is tagged, we may as well use the predefined
1667 -- primitive assignment. This avoids inlining a lot of code
1668 -- and in the class-wide case, the assignment is replaced by
1669 -- dispatch call to _assign. Note that this cannot be done
1670 -- when discriminant checks are locally suppressed (as in
1671 -- extension aggregate expansions) because otherwise the
1672 -- discriminant check will be performed within the _assign
1673 -- call. It is also suppressed for assignmments created by the
1674 -- expander that correspond to initializations, where we do
1675 -- want to copy the tag (No_Ctrl_Actions flag set True).
1676 -- by the expander and we do not need to mess with tags ever
1677 -- (Expand_Ctrl_Actions flag is set True in this case).
1679 or else (Is_Tagged_Type (Typ)
1680 and then Chars (Current_Scope) /= Name_uAssign
1681 and then Expand_Ctrl_Actions
1682 and then not Discriminant_Checks_Suppressed (Empty))
1683 then
1684 -- Fetch the primitive op _assign and proper type to call
1685 -- it. Because of possible conflits between private and
1686 -- full view the proper type is fetched directly from the
1687 -- operation profile.
1689 declare
1690 Op : constant Entity_Id :=
1691 Find_Prim_Op (Typ, Name_uAssign);
1692 F_Typ : Entity_Id := Etype (First_Formal (Op));
1694 begin
1695 -- If the assignment is dispatching, make sure to use the
1696 -- proper type.
1698 if Is_Class_Wide_Type (Typ) then
1699 F_Typ := Class_Wide_Type (F_Typ);
1700 end if;
1702 L := New_List;
1704 -- In case of assignment to a class-wide tagged type, before
1705 -- the assignment we generate run-time check to ensure that
1706 -- the tag of the Target is covered by the tag of the source
1708 if Is_Class_Wide_Type (Typ)
1709 and then Is_Tagged_Type (Typ)
1710 and then Is_Tagged_Type (Underlying_Type (Etype (Rhs)))
1711 then
1712 Append_To (L,
1713 Make_Raise_Constraint_Error (Loc,
1714 Condition =>
1715 Make_Op_Not (Loc,
1716 Make_Function_Call (Loc,
1717 Name => New_Reference_To
1718 (RTE (RE_CW_Membership), Loc),
1719 Parameter_Associations => New_List (
1720 Make_Selected_Component (Loc,
1721 Prefix =>
1722 Duplicate_Subexpr (Lhs),
1723 Selector_Name =>
1724 Make_Identifier (Loc, Name_uTag)),
1725 Make_Selected_Component (Loc,
1726 Prefix =>
1727 Duplicate_Subexpr (Rhs),
1728 Selector_Name =>
1729 Make_Identifier (Loc, Name_uTag))))),
1730 Reason => CE_Tag_Check_Failed));
1731 end if;
1733 Append_To (L,
1734 Make_Procedure_Call_Statement (Loc,
1735 Name => New_Reference_To (Op, Loc),
1736 Parameter_Associations => New_List (
1737 Unchecked_Convert_To (F_Typ, Duplicate_Subexpr (Lhs)),
1738 Unchecked_Convert_To (F_Typ,
1739 Duplicate_Subexpr (Rhs)))));
1740 end;
1742 else
1743 L := Make_Tag_Ctrl_Assignment (N);
1745 -- We can't afford to have destructive Finalization Actions
1746 -- in the Self assignment case, so if the target and the
1747 -- source are not obviously different, code is generated to
1748 -- avoid the self assignment case
1750 -- if lhs'address /= rhs'address then
1751 -- <code for controlled and/or tagged assignment>
1752 -- end if;
1754 if not Statically_Different (Lhs, Rhs)
1755 and then Expand_Ctrl_Actions
1756 then
1757 L := New_List (
1758 Make_Implicit_If_Statement (N,
1759 Condition =>
1760 Make_Op_Ne (Loc,
1761 Left_Opnd =>
1762 Make_Attribute_Reference (Loc,
1763 Prefix => Duplicate_Subexpr (Lhs),
1764 Attribute_Name => Name_Address),
1766 Right_Opnd =>
1767 Make_Attribute_Reference (Loc,
1768 Prefix => Duplicate_Subexpr (Rhs),
1769 Attribute_Name => Name_Address)),
1771 Then_Statements => L));
1772 end if;
1774 -- We need to set up an exception handler for implementing
1775 -- 7.6.1 (18). The remaining adjustments are tackled by the
1776 -- implementation of adjust for record_controllers (see
1777 -- s-finimp.adb)
1779 -- This is skipped if we have no finalization
1781 if Expand_Ctrl_Actions
1782 and then not Restriction_Active (No_Finalization)
1783 then
1784 L := New_List (
1785 Make_Block_Statement (Loc,
1786 Handled_Statement_Sequence =>
1787 Make_Handled_Sequence_Of_Statements (Loc,
1788 Statements => L,
1789 Exception_Handlers => New_List (
1790 Make_Exception_Handler (Loc,
1791 Exception_Choices =>
1792 New_List (Make_Others_Choice (Loc)),
1793 Statements => New_List (
1794 Make_Raise_Program_Error (Loc,
1795 Reason =>
1796 PE_Finalize_Raised_Exception)
1797 ))))));
1798 end if;
1799 end if;
1801 Rewrite (N,
1802 Make_Block_Statement (Loc,
1803 Handled_Statement_Sequence =>
1804 Make_Handled_Sequence_Of_Statements (Loc, Statements => L)));
1806 -- If no restrictions on aborts, protect the whole assignement
1807 -- for controlled objects as per 9.8(11)
1809 if Controlled_Type (Typ)
1810 and then Expand_Ctrl_Actions
1811 and then Abort_Allowed
1812 then
1813 declare
1814 Blk : constant Entity_Id :=
1815 New_Internal_Entity
1816 (E_Block, Current_Scope, Sloc (N), 'B');
1818 begin
1819 Set_Scope (Blk, Current_Scope);
1820 Set_Etype (Blk, Standard_Void_Type);
1821 Set_Identifier (N, New_Occurrence_Of (Blk, Sloc (N)));
1823 Prepend_To (L, Build_Runtime_Call (Loc, RE_Abort_Defer));
1824 Set_At_End_Proc (Handled_Statement_Sequence (N),
1825 New_Occurrence_Of (RTE (RE_Abort_Undefer_Direct), Loc));
1826 Expand_At_End_Handler
1827 (Handled_Statement_Sequence (N), Blk);
1828 end;
1829 end if;
1831 -- N has been rewritten to a block statement for which it is
1832 -- known by construction that no checks are necessary: analyze
1833 -- it with all checks suppressed.
1835 Analyze (N, Suppress => All_Checks);
1836 return;
1837 end Tagged_Case;
1839 -- Array types
1841 elsif Is_Array_Type (Typ) then
1842 declare
1843 Actual_Rhs : Node_Id := Rhs;
1845 begin
1846 while Nkind (Actual_Rhs) = N_Type_Conversion
1847 or else
1848 Nkind (Actual_Rhs) = N_Qualified_Expression
1849 loop
1850 Actual_Rhs := Expression (Actual_Rhs);
1851 end loop;
1853 Expand_Assign_Array (N, Actual_Rhs);
1854 return;
1855 end;
1857 -- Record types
1859 elsif Is_Record_Type (Typ) then
1860 Expand_Assign_Record (N);
1861 return;
1863 -- Scalar types. This is where we perform the processing related
1864 -- to the requirements of (RM 13.9.1(9-11)) concerning the handling
1865 -- of invalid scalar values.
1867 elsif Is_Scalar_Type (Typ) then
1869 -- Case where right side is known valid
1871 if Expr_Known_Valid (Rhs) then
1873 -- Here the right side is valid, so it is fine. The case to
1874 -- deal with is when the left side is a local variable reference
1875 -- whose value is not currently known to be valid. If this is
1876 -- the case, and the assignment appears in an unconditional
1877 -- context, then we can mark the left side as now being valid.
1879 if Is_Local_Variable_Reference (Lhs)
1880 and then not Is_Known_Valid (Entity (Lhs))
1881 and then In_Unconditional_Context (N)
1882 then
1883 Set_Is_Known_Valid (Entity (Lhs), True);
1884 end if;
1886 -- Case where right side may be invalid in the sense of the RM
1887 -- reference above. The RM does not require that we check for
1888 -- the validity on an assignment, but it does require that the
1889 -- assignment of an invalid value not cause erroneous behavior.
1891 -- The general approach in GNAT is to use the Is_Known_Valid flag
1892 -- to avoid the need for validity checking on assignments. However
1893 -- in some cases, we have to do validity checking in order to make
1894 -- sure that the setting of this flag is correct.
1896 else
1897 -- Validate right side if we are validating copies
1899 if Validity_Checks_On
1900 and then Validity_Check_Copies
1901 then
1902 Ensure_Valid (Rhs);
1904 -- We can propagate this to the left side where appropriate
1906 if Is_Local_Variable_Reference (Lhs)
1907 and then not Is_Known_Valid (Entity (Lhs))
1908 and then In_Unconditional_Context (N)
1909 then
1910 Set_Is_Known_Valid (Entity (Lhs), True);
1911 end if;
1913 -- Otherwise check to see what should be done
1915 -- If left side is a local variable, then we just set its
1916 -- flag to indicate that its value may no longer be valid,
1917 -- since we are copying a potentially invalid value.
1919 elsif Is_Local_Variable_Reference (Lhs) then
1920 Set_Is_Known_Valid (Entity (Lhs), False);
1922 -- Check for case of a nonlocal variable on the left side
1923 -- which is currently known to be valid. In this case, we
1924 -- simply ensure that the right side is valid. We only play
1925 -- the game of copying validity status for local variables,
1926 -- since we are doing this statically, not by tracing the
1927 -- full flow graph.
1929 elsif Is_Entity_Name (Lhs)
1930 and then Is_Known_Valid (Entity (Lhs))
1931 then
1932 -- Note that the Ensure_Valid call is ignored if the
1933 -- Validity_Checking mode is set to none so we do not
1934 -- need to worry about that case here.
1936 Ensure_Valid (Rhs);
1938 -- In all other cases, we can safely copy an invalid value
1939 -- without worrying about the status of the left side. Since
1940 -- it is not a variable reference it will not be considered
1941 -- as being known to be valid in any case.
1943 else
1944 null;
1945 end if;
1946 end if;
1947 end if;
1949 -- Defend against invalid subscripts on left side if we are in
1950 -- standard validity checking mode. No need to do this if we
1951 -- are checking all subscripts.
1953 if Validity_Checks_On
1954 and then Validity_Check_Default
1955 and then not Validity_Check_Subscripts
1956 then
1957 Check_Valid_Lvalue_Subscripts (Lhs);
1958 end if;
1960 exception
1961 when RE_Not_Available =>
1962 return;
1963 end Expand_N_Assignment_Statement;
1965 ------------------------------
1966 -- Expand_N_Block_Statement --
1967 ------------------------------
1969 -- Encode entity names defined in block statement
1971 procedure Expand_N_Block_Statement (N : Node_Id) is
1972 begin
1973 Qualify_Entity_Names (N);
1974 end Expand_N_Block_Statement;
1976 -----------------------------
1977 -- Expand_N_Case_Statement --
1978 -----------------------------
1980 procedure Expand_N_Case_Statement (N : Node_Id) is
1981 Loc : constant Source_Ptr := Sloc (N);
1982 Expr : constant Node_Id := Expression (N);
1983 Alt : Node_Id;
1984 Len : Nat;
1985 Cond : Node_Id;
1986 Choice : Node_Id;
1987 Chlist : List_Id;
1989 begin
1990 -- Check for the situation where we know at compile time which
1991 -- branch will be taken
1993 if Compile_Time_Known_Value (Expr) then
1994 Alt := Find_Static_Alternative (N);
1996 -- Move the statements from this alternative after the case
1997 -- statement. They are already analyzed, so will be skipped
1998 -- by the analyzer.
2000 Insert_List_After (N, Statements (Alt));
2002 -- That leaves the case statement as a shell. The alternative
2003 -- that will be executed is reset to a null list. So now we can
2004 -- kill the entire case statement.
2006 Kill_Dead_Code (Expression (N));
2007 Kill_Dead_Code (Alternatives (N));
2008 Rewrite (N, Make_Null_Statement (Loc));
2009 return;
2010 end if;
2012 -- Here if the choice is not determined at compile time
2014 declare
2015 Last_Alt : constant Node_Id := Last (Alternatives (N));
2017 Others_Present : Boolean;
2018 Others_Node : Node_Id;
2020 Then_Stms : List_Id;
2021 Else_Stms : List_Id;
2023 begin
2024 if Nkind (First (Discrete_Choices (Last_Alt))) = N_Others_Choice then
2025 Others_Present := True;
2026 Others_Node := Last_Alt;
2027 else
2028 Others_Present := False;
2029 end if;
2031 -- First step is to worry about possible invalid argument. The RM
2032 -- requires (RM 5.4(13)) that if the result is invalid (e.g. it is
2033 -- outside the base range), then Constraint_Error must be raised.
2035 -- Case of validity check required (validity checks are on, the
2036 -- expression is not known to be valid, and the case statement
2037 -- comes from source -- no need to validity check internally
2038 -- generated case statements).
2040 if Validity_Check_Default then
2041 Ensure_Valid (Expr);
2042 end if;
2044 -- If there is only a single alternative, just replace it with
2045 -- the sequence of statements since obviously that is what is
2046 -- going to be executed in all cases.
2048 Len := List_Length (Alternatives (N));
2050 if Len = 1 then
2051 -- We still need to evaluate the expression if it has any
2052 -- side effects.
2054 Remove_Side_Effects (Expression (N));
2056 Insert_List_After (N, Statements (First (Alternatives (N))));
2058 -- That leaves the case statement as a shell. The alternative
2059 -- that will be executed is reset to a null list. So now we can
2060 -- kill the entire case statement.
2062 Kill_Dead_Code (Expression (N));
2063 Rewrite (N, Make_Null_Statement (Loc));
2064 return;
2065 end if;
2067 -- An optimization. If there are only two alternatives, and only
2068 -- a single choice, then rewrite the whole case statement as an
2069 -- if statement, since this can result in susbequent optimizations.
2070 -- This helps not only with case statements in the source of a
2071 -- simple form, but also with generated code (discriminant check
2072 -- functions in particular)
2074 if Len = 2 then
2075 Chlist := Discrete_Choices (First (Alternatives (N)));
2077 if List_Length (Chlist) = 1 then
2078 Choice := First (Chlist);
2080 Then_Stms := Statements (First (Alternatives (N)));
2081 Else_Stms := Statements (Last (Alternatives (N)));
2083 -- For TRUE, generate "expression", not expression = true
2085 if Nkind (Choice) = N_Identifier
2086 and then Entity (Choice) = Standard_True
2087 then
2088 Cond := Expression (N);
2090 -- For FALSE, generate "expression" and switch then/else
2092 elsif Nkind (Choice) = N_Identifier
2093 and then Entity (Choice) = Standard_False
2094 then
2095 Cond := Expression (N);
2096 Else_Stms := Statements (First (Alternatives (N)));
2097 Then_Stms := Statements (Last (Alternatives (N)));
2099 -- For a range, generate "expression in range"
2101 elsif Nkind (Choice) = N_Range
2102 or else (Nkind (Choice) = N_Attribute_Reference
2103 and then Attribute_Name (Choice) = Name_Range)
2104 or else (Is_Entity_Name (Choice)
2105 and then Is_Type (Entity (Choice)))
2106 or else Nkind (Choice) = N_Subtype_Indication
2107 then
2108 Cond :=
2109 Make_In (Loc,
2110 Left_Opnd => Expression (N),
2111 Right_Opnd => Relocate_Node (Choice));
2113 -- For any other subexpression "expression = value"
2115 else
2116 Cond :=
2117 Make_Op_Eq (Loc,
2118 Left_Opnd => Expression (N),
2119 Right_Opnd => Relocate_Node (Choice));
2120 end if;
2122 -- Now rewrite the case as an IF
2124 Rewrite (N,
2125 Make_If_Statement (Loc,
2126 Condition => Cond,
2127 Then_Statements => Then_Stms,
2128 Else_Statements => Else_Stms));
2129 Analyze (N);
2130 return;
2131 end if;
2132 end if;
2134 -- If the last alternative is not an Others choice, replace it
2135 -- with an N_Others_Choice. Note that we do not bother to call
2136 -- Analyze on the modified case statement, since it's only effect
2137 -- would be to compute the contents of the Others_Discrete_Choices
2138 -- which is not needed by the back end anyway.
2140 -- The reason we do this is that the back end always needs some
2141 -- default for a switch, so if we have not supplied one in the
2142 -- processing above for validity checking, then we need to
2143 -- supply one here.
2145 if not Others_Present then
2146 Others_Node := Make_Others_Choice (Sloc (Last_Alt));
2147 Set_Others_Discrete_Choices
2148 (Others_Node, Discrete_Choices (Last_Alt));
2149 Set_Discrete_Choices (Last_Alt, New_List (Others_Node));
2150 end if;
2151 end;
2152 end Expand_N_Case_Statement;
2154 -----------------------------
2155 -- Expand_N_Exit_Statement --
2156 -----------------------------
2158 -- The only processing required is to deal with a possible C/Fortran
2159 -- boolean value used as the condition for the exit statement.
2161 procedure Expand_N_Exit_Statement (N : Node_Id) is
2162 begin
2163 Adjust_Condition (Condition (N));
2164 end Expand_N_Exit_Statement;
2166 -----------------------------
2167 -- Expand_N_Goto_Statement --
2168 -----------------------------
2170 -- Add poll before goto if polling active
2172 procedure Expand_N_Goto_Statement (N : Node_Id) is
2173 begin
2174 Generate_Poll_Call (N);
2175 end Expand_N_Goto_Statement;
2177 ---------------------------
2178 -- Expand_N_If_Statement --
2179 ---------------------------
2181 -- First we deal with the case of C and Fortran convention boolean
2182 -- values, with zero/non-zero semantics.
2184 -- Second, we deal with the obvious rewriting for the cases where the
2185 -- condition of the IF is known at compile time to be True or False.
2187 -- Third, we remove elsif parts which have non-empty Condition_Actions
2188 -- and rewrite as independent if statements. For example:
2190 -- if x then xs
2191 -- elsif y then ys
2192 -- ...
2193 -- end if;
2195 -- becomes
2197 -- if x then xs
2198 -- else
2199 -- <<condition actions of y>>
2200 -- if y then ys
2201 -- ...
2202 -- end if;
2203 -- end if;
2205 -- This rewriting is needed if at least one elsif part has a non-empty
2206 -- Condition_Actions list. We also do the same processing if there is
2207 -- a constant condition in an elsif part (in conjunction with the first
2208 -- processing step mentioned above, for the recursive call made to deal
2209 -- with the created inner if, this deals with properly optimizing the
2210 -- cases of constant elsif conditions).
2212 procedure Expand_N_If_Statement (N : Node_Id) is
2213 Loc : constant Source_Ptr := Sloc (N);
2214 Hed : Node_Id;
2215 E : Node_Id;
2216 New_If : Node_Id;
2218 begin
2219 Adjust_Condition (Condition (N));
2221 -- The following loop deals with constant conditions for the IF. We
2222 -- need a loop because as we eliminate False conditions, we grab the
2223 -- first elsif condition and use it as the primary condition.
2225 while Compile_Time_Known_Value (Condition (N)) loop
2227 -- If condition is True, we can simply rewrite the if statement
2228 -- now by replacing it by the series of then statements.
2230 if Is_True (Expr_Value (Condition (N))) then
2232 -- All the else parts can be killed
2234 Kill_Dead_Code (Elsif_Parts (N));
2235 Kill_Dead_Code (Else_Statements (N));
2237 Hed := Remove_Head (Then_Statements (N));
2238 Insert_List_After (N, Then_Statements (N));
2239 Rewrite (N, Hed);
2240 return;
2242 -- If condition is False, then we can delete the condition and
2243 -- the Then statements
2245 else
2246 -- We do not delete the condition if constant condition
2247 -- warnings are enabled, since otherwise we end up deleting
2248 -- the desired warning. Of course the backend will get rid
2249 -- of this True/False test anyway, so nothing is lost here.
2251 if not Constant_Condition_Warnings then
2252 Kill_Dead_Code (Condition (N));
2253 end if;
2255 Kill_Dead_Code (Then_Statements (N));
2257 -- If there are no elsif statements, then we simply replace
2258 -- the entire if statement by the sequence of else statements.
2260 if No (Elsif_Parts (N)) then
2262 if No (Else_Statements (N))
2263 or else Is_Empty_List (Else_Statements (N))
2264 then
2265 Rewrite (N,
2266 Make_Null_Statement (Sloc (N)));
2268 else
2269 Hed := Remove_Head (Else_Statements (N));
2270 Insert_List_After (N, Else_Statements (N));
2271 Rewrite (N, Hed);
2272 end if;
2274 return;
2276 -- If there are elsif statements, the first of them becomes
2277 -- the if/then section of the rebuilt if statement This is
2278 -- the case where we loop to reprocess this copied condition.
2280 else
2281 Hed := Remove_Head (Elsif_Parts (N));
2282 Insert_Actions (N, Condition_Actions (Hed));
2283 Set_Condition (N, Condition (Hed));
2284 Set_Then_Statements (N, Then_Statements (Hed));
2286 -- Hed might have been captured as the condition determining
2287 -- the current value for an entity. Now it is detached from
2288 -- the tree, so a Current_Value pointer in the condition might
2289 -- need to be updated.
2291 Check_Possible_Current_Value_Condition (N);
2293 if Is_Empty_List (Elsif_Parts (N)) then
2294 Set_Elsif_Parts (N, No_List);
2295 end if;
2296 end if;
2297 end if;
2298 end loop;
2300 -- Loop through elsif parts, dealing with constant conditions and
2301 -- possible expression actions that are present.
2303 if Present (Elsif_Parts (N)) then
2304 E := First (Elsif_Parts (N));
2305 while Present (E) loop
2306 Adjust_Condition (Condition (E));
2308 -- If there are condition actions, then we rewrite the if
2309 -- statement as indicated above. We also do the same rewrite
2310 -- if the condition is True or False. The further processing
2311 -- of this constant condition is then done by the recursive
2312 -- call to expand the newly created if statement
2314 if Present (Condition_Actions (E))
2315 or else Compile_Time_Known_Value (Condition (E))
2316 then
2317 -- Note this is not an implicit if statement, since it is
2318 -- part of an explicit if statement in the source (or of an
2319 -- implicit if statement that has already been tested).
2321 New_If :=
2322 Make_If_Statement (Sloc (E),
2323 Condition => Condition (E),
2324 Then_Statements => Then_Statements (E),
2325 Elsif_Parts => No_List,
2326 Else_Statements => Else_Statements (N));
2328 -- Elsif parts for new if come from remaining elsif's of parent
2330 while Present (Next (E)) loop
2331 if No (Elsif_Parts (New_If)) then
2332 Set_Elsif_Parts (New_If, New_List);
2333 end if;
2335 Append (Remove_Next (E), Elsif_Parts (New_If));
2336 end loop;
2338 Set_Else_Statements (N, New_List (New_If));
2340 if Present (Condition_Actions (E)) then
2341 Insert_List_Before (New_If, Condition_Actions (E));
2342 end if;
2344 Remove (E);
2346 if Is_Empty_List (Elsif_Parts (N)) then
2347 Set_Elsif_Parts (N, No_List);
2348 end if;
2350 Analyze (New_If);
2351 return;
2353 -- No special processing for that elsif part, move to next
2355 else
2356 Next (E);
2357 end if;
2358 end loop;
2359 end if;
2361 -- Some more optimizations applicable if we still have an IF statement
2363 if Nkind (N) /= N_If_Statement then
2364 return;
2365 end if;
2367 -- Another optimization, special cases that can be simplified
2369 -- if expression then
2370 -- return true;
2371 -- else
2372 -- return false;
2373 -- end if;
2375 -- can be changed to:
2377 -- return expression;
2379 -- and
2381 -- if expression then
2382 -- return false;
2383 -- else
2384 -- return true;
2385 -- end if;
2387 -- can be changed to:
2389 -- return not (expression);
2391 if Nkind (N) = N_If_Statement
2392 and then No (Elsif_Parts (N))
2393 and then Present (Else_Statements (N))
2394 and then List_Length (Then_Statements (N)) = 1
2395 and then List_Length (Else_Statements (N)) = 1
2396 then
2397 declare
2398 Then_Stm : constant Node_Id := First (Then_Statements (N));
2399 Else_Stm : constant Node_Id := First (Else_Statements (N));
2401 begin
2402 if Nkind (Then_Stm) = N_Return_Statement
2403 and then
2404 Nkind (Else_Stm) = N_Return_Statement
2405 then
2406 declare
2407 Then_Expr : constant Node_Id := Expression (Then_Stm);
2408 Else_Expr : constant Node_Id := Expression (Else_Stm);
2410 begin
2411 if Nkind (Then_Expr) = N_Identifier
2412 and then
2413 Nkind (Else_Expr) = N_Identifier
2414 then
2415 if Entity (Then_Expr) = Standard_True
2416 and then Entity (Else_Expr) = Standard_False
2417 then
2418 Rewrite (N,
2419 Make_Return_Statement (Loc,
2420 Expression => Relocate_Node (Condition (N))));
2421 Analyze (N);
2422 return;
2424 elsif Entity (Then_Expr) = Standard_False
2425 and then Entity (Else_Expr) = Standard_True
2426 then
2427 Rewrite (N,
2428 Make_Return_Statement (Loc,
2429 Expression =>
2430 Make_Op_Not (Loc,
2431 Right_Opnd => Relocate_Node (Condition (N)))));
2432 Analyze (N);
2433 return;
2434 end if;
2435 end if;
2436 end;
2437 end if;
2438 end;
2439 end if;
2440 end Expand_N_If_Statement;
2442 -----------------------------
2443 -- Expand_N_Loop_Statement --
2444 -----------------------------
2446 -- 1. Deal with while condition for C/Fortran boolean
2447 -- 2. Deal with loops with a non-standard enumeration type range
2448 -- 3. Deal with while loops where Condition_Actions is set
2449 -- 4. Insert polling call if required
2451 procedure Expand_N_Loop_Statement (N : Node_Id) is
2452 Loc : constant Source_Ptr := Sloc (N);
2453 Isc : constant Node_Id := Iteration_Scheme (N);
2455 begin
2456 if Present (Isc) then
2457 Adjust_Condition (Condition (Isc));
2458 end if;
2460 if Is_Non_Empty_List (Statements (N)) then
2461 Generate_Poll_Call (First (Statements (N)));
2462 end if;
2464 if No (Isc) then
2465 return;
2466 end if;
2468 -- Handle the case where we have a for loop with the range type being
2469 -- an enumeration type with non-standard representation. In this case
2470 -- we expand:
2472 -- for x in [reverse] a .. b loop
2473 -- ...
2474 -- end loop;
2476 -- to
2478 -- for xP in [reverse] integer
2479 -- range etype'Pos (a) .. etype'Pos (b) loop
2480 -- declare
2481 -- x : constant etype := Pos_To_Rep (xP);
2482 -- begin
2483 -- ...
2484 -- end;
2485 -- end loop;
2487 if Present (Loop_Parameter_Specification (Isc)) then
2488 declare
2489 LPS : constant Node_Id := Loop_Parameter_Specification (Isc);
2490 Loop_Id : constant Entity_Id := Defining_Identifier (LPS);
2491 Ltype : constant Entity_Id := Etype (Loop_Id);
2492 Btype : constant Entity_Id := Base_Type (Ltype);
2493 Expr : Node_Id;
2494 New_Id : Entity_Id;
2496 begin
2497 if not Is_Enumeration_Type (Btype)
2498 or else No (Enum_Pos_To_Rep (Btype))
2499 then
2500 return;
2501 end if;
2503 New_Id :=
2504 Make_Defining_Identifier (Loc,
2505 Chars => New_External_Name (Chars (Loop_Id), 'P'));
2507 -- If the type has a contiguous representation, successive
2508 -- values can be generated as offsets from the first literal.
2510 if Has_Contiguous_Rep (Btype) then
2511 Expr :=
2512 Unchecked_Convert_To (Btype,
2513 Make_Op_Add (Loc,
2514 Left_Opnd =>
2515 Make_Integer_Literal (Loc,
2516 Enumeration_Rep (First_Literal (Btype))),
2517 Right_Opnd => New_Reference_To (New_Id, Loc)));
2518 else
2519 -- Use the constructed array Enum_Pos_To_Rep
2521 Expr :=
2522 Make_Indexed_Component (Loc,
2523 Prefix => New_Reference_To (Enum_Pos_To_Rep (Btype), Loc),
2524 Expressions => New_List (New_Reference_To (New_Id, Loc)));
2525 end if;
2527 Rewrite (N,
2528 Make_Loop_Statement (Loc,
2529 Identifier => Identifier (N),
2531 Iteration_Scheme =>
2532 Make_Iteration_Scheme (Loc,
2533 Loop_Parameter_Specification =>
2534 Make_Loop_Parameter_Specification (Loc,
2535 Defining_Identifier => New_Id,
2536 Reverse_Present => Reverse_Present (LPS),
2538 Discrete_Subtype_Definition =>
2539 Make_Subtype_Indication (Loc,
2541 Subtype_Mark =>
2542 New_Reference_To (Standard_Natural, Loc),
2544 Constraint =>
2545 Make_Range_Constraint (Loc,
2546 Range_Expression =>
2547 Make_Range (Loc,
2549 Low_Bound =>
2550 Make_Attribute_Reference (Loc,
2551 Prefix =>
2552 New_Reference_To (Btype, Loc),
2554 Attribute_Name => Name_Pos,
2556 Expressions => New_List (
2557 Relocate_Node
2558 (Type_Low_Bound (Ltype)))),
2560 High_Bound =>
2561 Make_Attribute_Reference (Loc,
2562 Prefix =>
2563 New_Reference_To (Btype, Loc),
2565 Attribute_Name => Name_Pos,
2567 Expressions => New_List (
2568 Relocate_Node
2569 (Type_High_Bound (Ltype))))))))),
2571 Statements => New_List (
2572 Make_Block_Statement (Loc,
2573 Declarations => New_List (
2574 Make_Object_Declaration (Loc,
2575 Defining_Identifier => Loop_Id,
2576 Constant_Present => True,
2577 Object_Definition => New_Reference_To (Ltype, Loc),
2578 Expression => Expr)),
2580 Handled_Statement_Sequence =>
2581 Make_Handled_Sequence_Of_Statements (Loc,
2582 Statements => Statements (N)))),
2584 End_Label => End_Label (N)));
2585 Analyze (N);
2586 end;
2588 -- Second case, if we have a while loop with Condition_Actions set,
2589 -- then we change it into a plain loop:
2591 -- while C loop
2592 -- ...
2593 -- end loop;
2595 -- changed to:
2597 -- loop
2598 -- <<condition actions>>
2599 -- exit when not C;
2600 -- ...
2601 -- end loop
2603 elsif Present (Isc)
2604 and then Present (Condition_Actions (Isc))
2605 then
2606 declare
2607 ES : Node_Id;
2609 begin
2610 ES :=
2611 Make_Exit_Statement (Sloc (Condition (Isc)),
2612 Condition =>
2613 Make_Op_Not (Sloc (Condition (Isc)),
2614 Right_Opnd => Condition (Isc)));
2616 Prepend (ES, Statements (N));
2617 Insert_List_Before (ES, Condition_Actions (Isc));
2619 -- This is not an implicit loop, since it is generated in
2620 -- response to the loop statement being processed. If this
2621 -- is itself implicit, the restriction has already been
2622 -- checked. If not, it is an explicit loop.
2624 Rewrite (N,
2625 Make_Loop_Statement (Sloc (N),
2626 Identifier => Identifier (N),
2627 Statements => Statements (N),
2628 End_Label => End_Label (N)));
2630 Analyze (N);
2631 end;
2632 end if;
2633 end Expand_N_Loop_Statement;
2635 -------------------------------
2636 -- Expand_N_Return_Statement --
2637 -------------------------------
2639 procedure Expand_N_Return_Statement (N : Node_Id) is
2640 Loc : constant Source_Ptr := Sloc (N);
2641 Exp : constant Node_Id := Expression (N);
2642 Exptyp : Entity_Id;
2643 T : Entity_Id;
2644 Utyp : Entity_Id;
2645 Scope_Id : Entity_Id;
2646 Kind : Entity_Kind;
2647 Call : Node_Id;
2648 Acc_Stat : Node_Id;
2649 Goto_Stat : Node_Id;
2650 Lab_Node : Node_Id;
2651 Cur_Idx : Nat;
2652 Return_Type : Entity_Id;
2653 Result_Exp : Node_Id;
2654 Result_Id : Entity_Id;
2655 Result_Obj : Node_Id;
2657 begin
2658 -- Case where returned expression is present
2660 if Present (Exp) then
2662 -- Always normalize C/Fortran boolean result. This is not always
2663 -- necessary, but it seems a good idea to minimize the passing
2664 -- around of non-normalized values, and in any case this handles
2665 -- the processing of barrier functions for protected types, which
2666 -- turn the condition into a return statement.
2668 Exptyp := Etype (Exp);
2670 if Is_Boolean_Type (Exptyp)
2671 and then Nonzero_Is_True (Exptyp)
2672 then
2673 Adjust_Condition (Exp);
2674 Adjust_Result_Type (Exp, Exptyp);
2675 end if;
2677 -- Do validity check if enabled for returns
2679 if Validity_Checks_On
2680 and then Validity_Check_Returns
2681 then
2682 Ensure_Valid (Exp);
2683 end if;
2684 end if;
2686 -- Find relevant enclosing scope from which return is returning
2688 Cur_Idx := Scope_Stack.Last;
2689 loop
2690 Scope_Id := Scope_Stack.Table (Cur_Idx).Entity;
2692 if Ekind (Scope_Id) /= E_Block
2693 and then Ekind (Scope_Id) /= E_Loop
2694 then
2695 exit;
2697 else
2698 Cur_Idx := Cur_Idx - 1;
2699 pragma Assert (Cur_Idx >= 0);
2700 end if;
2701 end loop;
2703 if No (Exp) then
2704 Kind := Ekind (Scope_Id);
2706 -- If it is a return from procedures do no extra steps
2708 if Kind = E_Procedure or else Kind = E_Generic_Procedure then
2709 return;
2710 end if;
2712 pragma Assert (Is_Entry (Scope_Id));
2714 -- Look at the enclosing block to see whether the return is from
2715 -- an accept statement or an entry body.
2717 for J in reverse 0 .. Cur_Idx loop
2718 Scope_Id := Scope_Stack.Table (J).Entity;
2719 exit when Is_Concurrent_Type (Scope_Id);
2720 end loop;
2722 -- If it is a return from accept statement it should be expanded
2723 -- as a call to RTS Complete_Rendezvous and a goto to the end of
2724 -- the accept body.
2726 -- (cf : Expand_N_Accept_Statement, Expand_N_Selective_Accept,
2727 -- Expand_N_Accept_Alternative in exp_ch9.adb)
2729 if Is_Task_Type (Scope_Id) then
2731 Call := (Make_Procedure_Call_Statement (Loc,
2732 Name => New_Reference_To
2733 (RTE (RE_Complete_Rendezvous), Loc)));
2734 Insert_Before (N, Call);
2735 -- why not insert actions here???
2736 Analyze (Call);
2738 Acc_Stat := Parent (N);
2739 while Nkind (Acc_Stat) /= N_Accept_Statement loop
2740 Acc_Stat := Parent (Acc_Stat);
2741 end loop;
2743 Lab_Node := Last (Statements
2744 (Handled_Statement_Sequence (Acc_Stat)));
2746 Goto_Stat := Make_Goto_Statement (Loc,
2747 Name => New_Occurrence_Of
2748 (Entity (Identifier (Lab_Node)), Loc));
2750 Set_Analyzed (Goto_Stat);
2752 Rewrite (N, Goto_Stat);
2753 Analyze (N);
2755 -- If it is a return from an entry body, put a Complete_Entry_Body
2756 -- call in front of the return.
2758 elsif Is_Protected_Type (Scope_Id) then
2760 Call :=
2761 Make_Procedure_Call_Statement (Loc,
2762 Name => New_Reference_To
2763 (RTE (RE_Complete_Entry_Body), Loc),
2764 Parameter_Associations => New_List
2765 (Make_Attribute_Reference (Loc,
2766 Prefix =>
2767 New_Reference_To
2768 (Object_Ref
2769 (Corresponding_Body (Parent (Scope_Id))),
2770 Loc),
2771 Attribute_Name => Name_Unchecked_Access)));
2773 Insert_Before (N, Call);
2774 Analyze (Call);
2776 end if;
2778 return;
2779 end if;
2781 T := Etype (Exp);
2782 Return_Type := Etype (Scope_Id);
2783 Utyp := Underlying_Type (Return_Type);
2785 -- Check the result expression of a scalar function against
2786 -- the subtype of the function by inserting a conversion.
2787 -- This conversion must eventually be performed for other
2788 -- classes of types, but for now it's only done for scalars.
2789 -- ???
2791 if Is_Scalar_Type (T) then
2792 Rewrite (Exp, Convert_To (Return_Type, Exp));
2793 Analyze (Exp);
2794 end if;
2796 -- Deal with returning variable length objects and controlled types
2798 -- Nothing to do if we are returning by reference, or this is not
2799 -- a type that requires special processing (indicated by the fact
2800 -- that it requires a cleanup scope for the secondary stack case).
2802 if Is_Return_By_Reference_Type (T) then
2803 null;
2805 elsif not Requires_Transient_Scope (Return_Type) then
2807 -- Mutable records with no variable length components are not
2808 -- returned on the sec-stack so we need to make sure that the
2809 -- backend will only copy back the size of the actual value and not
2810 -- the maximum size. We create an actual subtype for this purpose
2812 declare
2813 Ubt : constant Entity_Id := Underlying_Type (Base_Type (T));
2814 Decl : Node_Id;
2815 Ent : Entity_Id;
2816 begin
2817 if Has_Discriminants (Ubt)
2818 and then not Is_Constrained (Ubt)
2819 and then not Has_Unchecked_Union (Ubt)
2820 then
2821 Decl := Build_Actual_Subtype (Ubt, Exp);
2822 Ent := Defining_Identifier (Decl);
2823 Insert_Action (Exp, Decl);
2824 Rewrite (Exp, Unchecked_Convert_To (Ent, Exp));
2825 end if;
2826 end;
2828 -- Case of secondary stack not used
2830 elsif Function_Returns_With_DSP (Scope_Id) then
2832 -- Here what we need to do is to always return by reference, since
2833 -- we will return with the stack pointer depressed. We may need to
2834 -- do a copy to a local temporary before doing this return.
2836 No_Secondary_Stack_Case : declare
2837 Local_Copy_Required : Boolean := False;
2838 -- Set to True if a local copy is required
2840 Copy_Ent : Entity_Id;
2841 -- Used for the target entity if a copy is required
2843 Decl : Node_Id;
2844 -- Declaration used to create copy if needed
2846 procedure Test_Copy_Required (Expr : Node_Id);
2847 -- Determines if Expr represents a return value for which a
2848 -- copy is required. More specifically, a copy is not required
2849 -- if Expr represents an object or component of an object that
2850 -- is either in the local subprogram frame, or is constant.
2851 -- If a copy is required, then Local_Copy_Required is set True.
2853 ------------------------
2854 -- Test_Copy_Required --
2855 ------------------------
2857 procedure Test_Copy_Required (Expr : Node_Id) is
2858 Ent : Entity_Id;
2860 begin
2861 -- If component, test prefix (object containing component)
2863 if Nkind (Expr) = N_Indexed_Component
2864 or else
2865 Nkind (Expr) = N_Selected_Component
2866 then
2867 Test_Copy_Required (Prefix (Expr));
2868 return;
2870 -- See if we have an entity name
2872 elsif Is_Entity_Name (Expr) then
2873 Ent := Entity (Expr);
2875 -- Constant entity is always OK, no copy required
2877 if Ekind (Ent) = E_Constant then
2878 return;
2880 -- No copy required for local variable
2882 elsif Ekind (Ent) = E_Variable
2883 and then Scope (Ent) = Current_Subprogram
2884 then
2885 return;
2886 end if;
2887 end if;
2889 -- All other cases require a copy
2891 Local_Copy_Required := True;
2892 end Test_Copy_Required;
2894 -- Start of processing for No_Secondary_Stack_Case
2896 begin
2897 -- No copy needed if result is from a function call.
2898 -- In this case the result is already being returned by
2899 -- reference with the stack pointer depressed.
2901 -- To make up for a gcc 2.8.1 deficiency (???), we perform
2902 -- the copy for array types if the constrained status of the
2903 -- target type is different from that of the expression.
2905 if Requires_Transient_Scope (T)
2906 and then
2907 (not Is_Array_Type (T)
2908 or else Is_Constrained (T) = Is_Constrained (Return_Type)
2909 or else Controlled_Type (T))
2910 and then Nkind (Exp) = N_Function_Call
2911 then
2912 Set_By_Ref (N);
2914 -- We always need a local copy for a controlled type, since
2915 -- we are required to finalize the local value before return.
2916 -- The copy will automatically include the required finalize.
2917 -- Moreover, gigi cannot make this copy, since we need special
2918 -- processing to ensure proper behavior for finalization.
2920 -- Note: the reason we are returning with a depressed stack
2921 -- pointer in the controlled case (even if the type involved
2922 -- is constrained) is that we must make a local copy to deal
2923 -- properly with the requirement that the local result be
2924 -- finalized.
2926 elsif Controlled_Type (Utyp) then
2927 Copy_Ent :=
2928 Make_Defining_Identifier (Loc,
2929 Chars => New_Internal_Name ('R'));
2931 -- Build declaration to do the copy, and insert it, setting
2932 -- Assignment_OK, because we may be copying a limited type.
2933 -- In addition we set the special flag to inhibit finalize
2934 -- attachment if this is a controlled type (since this attach
2935 -- must be done by the caller, otherwise if we attach it here
2936 -- we will finalize the returned result prematurely).
2938 Decl :=
2939 Make_Object_Declaration (Loc,
2940 Defining_Identifier => Copy_Ent,
2941 Object_Definition => New_Occurrence_Of (Return_Type, Loc),
2942 Expression => Relocate_Node (Exp));
2944 Set_Assignment_OK (Decl);
2945 Set_Delay_Finalize_Attach (Decl);
2946 Insert_Action (N, Decl);
2948 -- Now the actual return uses the copied value
2950 Rewrite (Exp, New_Occurrence_Of (Copy_Ent, Loc));
2951 Analyze_And_Resolve (Exp, Return_Type);
2953 -- Since we have made the copy, gigi does not have to, so
2954 -- we set the By_Ref flag to prevent another copy being made.
2956 Set_By_Ref (N);
2958 -- Non-controlled cases
2960 else
2961 Test_Copy_Required (Exp);
2963 -- If a local copy is required, then gigi will make the
2964 -- copy, otherwise, we can return the result directly,
2965 -- so set By_Ref to suppress the gigi copy.
2967 if not Local_Copy_Required then
2968 Set_By_Ref (N);
2969 end if;
2970 end if;
2971 end No_Secondary_Stack_Case;
2973 -- Here if secondary stack is used
2975 else
2976 -- Make sure that no surrounding block will reclaim the
2977 -- secondary-stack on which we are going to put the result.
2978 -- Not only may this introduce secondary stack leaks but worse,
2979 -- if the reclamation is done too early, then the result we are
2980 -- returning may get clobbered. See example in 7417-003.
2982 declare
2983 S : Entity_Id := Current_Scope;
2985 begin
2986 while Ekind (S) = E_Block or else Ekind (S) = E_Loop loop
2987 Set_Sec_Stack_Needed_For_Return (S, True);
2988 S := Enclosing_Dynamic_Scope (S);
2989 end loop;
2990 end;
2992 -- Optimize the case where the result is a function call. In this
2993 -- case either the result is already on the secondary stack, or is
2994 -- already being returned with the stack pointer depressed and no
2995 -- further processing is required except to set the By_Ref flag to
2996 -- ensure that gigi does not attempt an extra unnecessary copy.
2997 -- (actually not just unnecessary but harmfully wrong in the case
2998 -- of a controlled type, where gigi does not know how to do a copy).
2999 -- To make up for a gcc 2.8.1 deficiency (???), we perform
3000 -- the copy for array types if the constrained status of the
3001 -- target type is different from that of the expression.
3003 if Requires_Transient_Scope (T)
3004 and then
3005 (not Is_Array_Type (T)
3006 or else Is_Constrained (T) = Is_Constrained (Return_Type)
3007 or else Controlled_Type (T))
3008 and then Nkind (Exp) = N_Function_Call
3009 then
3010 Set_By_Ref (N);
3012 -- Remove side effects from the expression now so that
3013 -- other part of the expander do not have to reanalyze
3014 -- this node without this optimization
3016 Rewrite (Exp, Duplicate_Subexpr_No_Checks (Exp));
3018 -- For controlled types, do the allocation on the sec-stack
3019 -- manually in order to call adjust at the right time
3020 -- type Anon1 is access Return_Type;
3021 -- for Anon1'Storage_pool use ss_pool;
3022 -- Anon2 : anon1 := new Return_Type'(expr);
3023 -- return Anon2.all;
3025 elsif Controlled_Type (Utyp) then
3026 declare
3027 Loc : constant Source_Ptr := Sloc (N);
3028 Temp : constant Entity_Id :=
3029 Make_Defining_Identifier (Loc,
3030 Chars => New_Internal_Name ('R'));
3031 Acc_Typ : constant Entity_Id :=
3032 Make_Defining_Identifier (Loc,
3033 Chars => New_Internal_Name ('A'));
3034 Alloc_Node : Node_Id;
3036 begin
3037 Set_Ekind (Acc_Typ, E_Access_Type);
3039 Set_Associated_Storage_Pool (Acc_Typ, RTE (RE_SS_Pool));
3041 Alloc_Node :=
3042 Make_Allocator (Loc,
3043 Expression =>
3044 Make_Qualified_Expression (Loc,
3045 Subtype_Mark => New_Reference_To (Etype (Exp), Loc),
3046 Expression => Relocate_Node (Exp)));
3048 Insert_List_Before_And_Analyze (N, New_List (
3049 Make_Full_Type_Declaration (Loc,
3050 Defining_Identifier => Acc_Typ,
3051 Type_Definition =>
3052 Make_Access_To_Object_Definition (Loc,
3053 Subtype_Indication =>
3054 New_Reference_To (Return_Type, Loc))),
3056 Make_Object_Declaration (Loc,
3057 Defining_Identifier => Temp,
3058 Object_Definition => New_Reference_To (Acc_Typ, Loc),
3059 Expression => Alloc_Node)));
3061 Rewrite (Exp,
3062 Make_Explicit_Dereference (Loc,
3063 Prefix => New_Reference_To (Temp, Loc)));
3065 Analyze_And_Resolve (Exp, Return_Type);
3066 end;
3068 -- Otherwise use the gigi mechanism to allocate result on the
3069 -- secondary stack.
3071 else
3072 Set_Storage_Pool (N, RTE (RE_SS_Pool));
3074 -- If we are generating code for the Java VM do not use
3075 -- SS_Allocate since everything is heap-allocated anyway.
3077 if not Java_VM then
3078 Set_Procedure_To_Call (N, RTE (RE_SS_Allocate));
3079 end if;
3080 end if;
3081 end if;
3083 -- Implement the rules of 6.5(8-10), which require a tag check in
3084 -- the case of a limited tagged return type, and tag reassignment
3085 -- for nonlimited tagged results. These actions are needed when
3086 -- the return type is a specific tagged type and the result
3087 -- expression is a conversion or a formal parameter, because in
3088 -- that case the tag of the expression might differ from the tag
3089 -- of the specific result type.
3091 if Is_Tagged_Type (Utyp)
3092 and then not Is_Class_Wide_Type (Utyp)
3093 and then (Nkind (Exp) = N_Type_Conversion
3094 or else Nkind (Exp) = N_Unchecked_Type_Conversion
3095 or else (Is_Entity_Name (Exp)
3096 and then Ekind (Entity (Exp)) in Formal_Kind))
3097 then
3098 -- When the return type is limited, perform a check that the
3099 -- tag of the result is the same as the tag of the return type.
3101 if Is_Limited_Type (Return_Type) then
3102 Insert_Action (Exp,
3103 Make_Raise_Constraint_Error (Loc,
3104 Condition =>
3105 Make_Op_Ne (Loc,
3106 Left_Opnd =>
3107 Make_Selected_Component (Loc,
3108 Prefix => Duplicate_Subexpr (Exp),
3109 Selector_Name =>
3110 New_Reference_To (First_Tag_Component (Utyp), Loc)),
3111 Right_Opnd =>
3112 Unchecked_Convert_To (RTE (RE_Tag),
3113 New_Reference_To
3114 (Node (First_Elmt
3115 (Access_Disp_Table (Base_Type (Utyp)))),
3116 Loc))),
3117 Reason => CE_Tag_Check_Failed));
3119 -- If the result type is a specific nonlimited tagged type,
3120 -- then we have to ensure that the tag of the result is that
3121 -- of the result type. This is handled by making a copy of the
3122 -- expression in the case where it might have a different tag,
3123 -- namely when the expression is a conversion or a formal
3124 -- parameter. We create a new object of the result type and
3125 -- initialize it from the expression, which will implicitly
3126 -- force the tag to be set appropriately.
3128 else
3129 Result_Id :=
3130 Make_Defining_Identifier (Loc, New_Internal_Name ('R'));
3131 Result_Exp := New_Reference_To (Result_Id, Loc);
3133 Result_Obj :=
3134 Make_Object_Declaration (Loc,
3135 Defining_Identifier => Result_Id,
3136 Object_Definition => New_Reference_To (Return_Type, Loc),
3137 Constant_Present => True,
3138 Expression => Relocate_Node (Exp));
3140 Set_Assignment_OK (Result_Obj);
3141 Insert_Action (Exp, Result_Obj);
3143 Rewrite (Exp, Result_Exp);
3144 Analyze_And_Resolve (Exp, Return_Type);
3145 end if;
3147 -- Ada 2005 (AI-344): If the result type is class-wide, then insert
3148 -- a check that the level of the return expression's underlying type
3149 -- is not deeper than the level of the master enclosing the function.
3150 -- Always generate the check when the type of the return expression
3151 -- is class-wide, when it's a type conversion, or when it's a formal
3152 -- parameter. Otherwise, suppress the check in the case where the
3153 -- return expression has a specific type whose level is known not to
3154 -- be statically deeper than the function's result type.
3156 elsif Ada_Version >= Ada_05
3157 and then Is_Class_Wide_Type (Return_Type)
3158 and then not Scope_Suppress (Accessibility_Check)
3159 and then
3160 (Is_Class_Wide_Type (Etype (Exp))
3161 or else Nkind (Exp) = N_Type_Conversion
3162 or else Nkind (Exp) = N_Unchecked_Type_Conversion
3163 or else (Is_Entity_Name (Exp)
3164 and then Ekind (Entity (Exp)) in Formal_Kind)
3165 or else Scope_Depth (Enclosing_Dynamic_Scope (Etype (Exp))) >
3166 Scope_Depth (Enclosing_Dynamic_Scope (Scope_Id)))
3167 then
3168 Insert_Action (Exp,
3169 Make_Raise_Program_Error (Loc,
3170 Condition =>
3171 Make_Op_Gt (Loc,
3172 Left_Opnd =>
3173 Make_Function_Call (Loc,
3174 Name =>
3175 New_Reference_To
3176 (RTE (RE_Get_Access_Level), Loc),
3177 Parameter_Associations =>
3178 New_List (Make_Attribute_Reference (Loc,
3179 Prefix =>
3180 Duplicate_Subexpr (Exp),
3181 Attribute_Name =>
3182 Name_Tag))),
3183 Right_Opnd =>
3184 Make_Integer_Literal (Loc,
3185 Scope_Depth (Enclosing_Dynamic_Scope (Scope_Id)))),
3186 Reason => PE_Accessibility_Check_Failed));
3187 end if;
3189 exception
3190 when RE_Not_Available =>
3191 return;
3192 end Expand_N_Return_Statement;
3194 ------------------------------
3195 -- Make_Tag_Ctrl_Assignment --
3196 ------------------------------
3198 function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id is
3199 Loc : constant Source_Ptr := Sloc (N);
3200 L : constant Node_Id := Name (N);
3201 T : constant Entity_Id := Underlying_Type (Etype (L));
3203 Ctrl_Act : constant Boolean := Controlled_Type (T)
3204 and then not No_Ctrl_Actions (N);
3206 Save_Tag : constant Boolean := Is_Tagged_Type (T)
3207 and then not No_Ctrl_Actions (N)
3208 and then not Java_VM;
3209 -- Tags are not saved and restored when Java_VM because JVM tags
3210 -- are represented implicitly in objects.
3212 Res : List_Id;
3213 Tag_Tmp : Entity_Id;
3215 begin
3216 Res := New_List;
3218 -- Finalize the target of the assignment when controlled.
3219 -- We have two exceptions here:
3221 -- 1. If we are in an init proc since it is an initialization
3222 -- more than an assignment
3224 -- 2. If the left-hand side is a temporary that was not initialized
3225 -- (or the parent part of a temporary since it is the case in
3226 -- extension aggregates). Such a temporary does not come from
3227 -- source. We must examine the original node for the prefix, because
3228 -- it may be a component of an entry formal, in which case it has
3229 -- been rewritten and does not appear to come from source either.
3231 -- Case of init proc
3233 if not Ctrl_Act then
3234 null;
3236 -- The left hand side is an uninitialized temporary
3238 elsif Nkind (L) = N_Type_Conversion
3239 and then Is_Entity_Name (Expression (L))
3240 and then No_Initialization (Parent (Entity (Expression (L))))
3241 then
3242 null;
3243 else
3244 Append_List_To (Res,
3245 Make_Final_Call (
3246 Ref => Duplicate_Subexpr_No_Checks (L),
3247 Typ => Etype (L),
3248 With_Detach => New_Reference_To (Standard_False, Loc)));
3249 end if;
3251 -- Save the Tag in a local variable Tag_Tmp
3253 if Save_Tag then
3254 Tag_Tmp :=
3255 Make_Defining_Identifier (Loc, New_Internal_Name ('A'));
3257 Append_To (Res,
3258 Make_Object_Declaration (Loc,
3259 Defining_Identifier => Tag_Tmp,
3260 Object_Definition => New_Reference_To (RTE (RE_Tag), Loc),
3261 Expression =>
3262 Make_Selected_Component (Loc,
3263 Prefix => Duplicate_Subexpr_No_Checks (L),
3264 Selector_Name => New_Reference_To (First_Tag_Component (T),
3265 Loc))));
3267 -- Otherwise Tag_Tmp not used
3269 else
3270 Tag_Tmp := Empty;
3271 end if;
3273 -- Processing for controlled types and types with controlled components
3275 -- Variables of such types contain pointers used to chain them in
3276 -- finalization lists, in addition to user data. These pointers are
3277 -- specific to each object of the type, not to the value being assigned.
3278 -- Thus they need to be left intact during the assignment. We achieve
3279 -- this by constructing a Storage_Array subtype, and by overlaying
3280 -- objects of this type on the source and target of the assignment.
3281 -- The assignment is then rewritten to assignments of slices of these
3282 -- arrays, copying the user data, and leaving the pointers untouched.
3284 if Ctrl_Act then
3285 Controlled_Actions : declare
3286 Prev_Ref : Node_Id;
3287 -- A reference to the Prev component of the record controller
3289 First_After_Root : Node_Id := Empty;
3290 -- Index of first byte to be copied (used to skip
3291 -- Root_Controlled in controlled objects).
3293 Last_Before_Hole : Node_Id := Empty;
3294 -- Index of last byte to be copied before outermost record
3295 -- controller data.
3297 Hole_Length : Node_Id := Empty;
3298 -- Length of record controller data (Prev and Next pointers)
3300 First_After_Hole : Node_Id := Empty;
3301 -- Index of first byte to be copied after outermost record
3302 -- controller data.
3304 Expr, Source_Size : Node_Id;
3305 Source_Actual_Subtype : Entity_Id;
3306 -- Used for computation of the size of the data to be copied
3308 Range_Type : Entity_Id;
3309 Opaque_Type : Entity_Id;
3311 function Build_Slice
3312 (Rec : Entity_Id;
3313 Lo : Node_Id;
3314 Hi : Node_Id) return Node_Id;
3315 -- Build and return a slice of an array of type S overlaid
3316 -- on object Rec, with bounds specified by Lo and Hi. If either
3317 -- bound is empty, a default of S'First (respectively S'Last)
3318 -- is used.
3320 -----------------
3321 -- Build_Slice --
3322 -----------------
3324 function Build_Slice
3325 (Rec : Node_Id;
3326 Lo : Node_Id;
3327 Hi : Node_Id) return Node_Id
3329 Lo_Bound : Node_Id;
3330 Hi_Bound : Node_Id;
3332 Opaque : constant Node_Id :=
3333 Unchecked_Convert_To (Opaque_Type,
3334 Make_Attribute_Reference (Loc,
3335 Prefix => Rec,
3336 Attribute_Name => Name_Address));
3337 -- Access value designating an opaque storage array of
3338 -- type S overlaid on record Rec.
3340 begin
3341 -- Compute slice bounds using S'First (1) and S'Last
3342 -- as default values when not specified by the caller.
3344 if No (Lo) then
3345 Lo_Bound := Make_Integer_Literal (Loc, 1);
3346 else
3347 Lo_Bound := Lo;
3348 end if;
3350 if No (Hi) then
3351 Hi_Bound := Make_Attribute_Reference (Loc,
3352 Prefix => New_Occurrence_Of (Range_Type, Loc),
3353 Attribute_Name => Name_Last);
3354 else
3355 Hi_Bound := Hi;
3356 end if;
3358 return Make_Slice (Loc,
3359 Prefix =>
3360 Opaque,
3361 Discrete_Range => Make_Range (Loc,
3362 Lo_Bound, Hi_Bound));
3363 end Build_Slice;
3365 -- Start of processing for Controlled_Actions
3367 begin
3368 -- Create a constrained subtype of Storage_Array whose size
3369 -- corresponds to the value being assigned.
3371 -- subtype G is Storage_Offset range
3372 -- 1 .. (Expr'Size + Storage_Unit - 1) / Storage_Unit
3374 Expr := Duplicate_Subexpr_No_Checks (Expression (N));
3376 if Nkind (Expr) = N_Qualified_Expression then
3377 Expr := Expression (Expr);
3378 end if;
3380 Source_Actual_Subtype := Etype (Expr);
3382 if Has_Discriminants (Source_Actual_Subtype)
3383 and then not Is_Constrained (Source_Actual_Subtype)
3384 then
3385 Append_To (Res,
3386 Build_Actual_Subtype (Source_Actual_Subtype, Expr));
3387 Source_Actual_Subtype := Defining_Identifier (Last (Res));
3388 end if;
3390 Source_Size :=
3391 Make_Op_Add (Loc,
3392 Left_Opnd =>
3393 Make_Attribute_Reference (Loc,
3394 Prefix =>
3395 New_Occurrence_Of (Source_Actual_Subtype, Loc),
3396 Attribute_Name =>
3397 Name_Size),
3398 Right_Opnd =>
3399 Make_Integer_Literal (Loc,
3400 System_Storage_Unit - 1));
3401 Source_Size :=
3402 Make_Op_Divide (Loc,
3403 Left_Opnd => Source_Size,
3404 Right_Opnd =>
3405 Make_Integer_Literal (Loc,
3406 Intval => System_Storage_Unit));
3408 Range_Type :=
3409 Make_Defining_Identifier (Loc,
3410 New_Internal_Name ('G'));
3412 Append_To (Res,
3413 Make_Subtype_Declaration (Loc,
3414 Defining_Identifier => Range_Type,
3415 Subtype_Indication =>
3416 Make_Subtype_Indication (Loc,
3417 Subtype_Mark =>
3418 New_Reference_To (RTE (RE_Storage_Offset), Loc),
3419 Constraint => Make_Range_Constraint (Loc,
3420 Range_Expression =>
3421 Make_Range (Loc,
3422 Low_Bound => Make_Integer_Literal (Loc, 1),
3423 High_Bound => Source_Size)))));
3425 -- subtype S is Storage_Array (G)
3427 Append_To (Res,
3428 Make_Subtype_Declaration (Loc,
3429 Defining_Identifier =>
3430 Make_Defining_Identifier (Loc,
3431 New_Internal_Name ('S')),
3432 Subtype_Indication =>
3433 Make_Subtype_Indication (Loc,
3434 Subtype_Mark =>
3435 New_Reference_To (RTE (RE_Storage_Array), Loc),
3436 Constraint =>
3437 Make_Index_Or_Discriminant_Constraint (Loc,
3438 Constraints =>
3439 New_List (New_Reference_To (Range_Type, Loc))))));
3441 -- type A is access S
3443 Opaque_Type :=
3444 Make_Defining_Identifier (Loc,
3445 Chars => New_Internal_Name ('A'));
3447 Append_To (Res,
3448 Make_Full_Type_Declaration (Loc,
3449 Defining_Identifier => Opaque_Type,
3450 Type_Definition =>
3451 Make_Access_To_Object_Definition (Loc,
3452 Subtype_Indication =>
3453 New_Occurrence_Of (
3454 Defining_Identifier (Last (Res)), Loc))));
3456 -- Generate appropriate slice assignments
3458 First_After_Root := Make_Integer_Literal (Loc, 1);
3460 -- For the case of a controlled object, skip the
3461 -- Root_Controlled part.
3463 if Is_Controlled (T) then
3464 First_After_Root :=
3465 Make_Op_Add (Loc,
3466 First_After_Root,
3467 Make_Op_Divide (Loc,
3468 Make_Attribute_Reference (Loc,
3469 Prefix =>
3470 New_Occurrence_Of (RTE (RE_Root_Controlled), Loc),
3471 Attribute_Name => Name_Size),
3472 Make_Integer_Literal (Loc, System_Storage_Unit)));
3473 end if;
3475 -- For the case of a record with controlled components, skip
3476 -- the Prev and Next components of the record controller.
3477 -- These components constitute a 'hole' in the middle of the
3478 -- data to be copied.
3480 if Has_Controlled_Component (T) then
3481 Prev_Ref :=
3482 Make_Selected_Component (Loc,
3483 Prefix =>
3484 Make_Selected_Component (Loc,
3485 Prefix => Duplicate_Subexpr_No_Checks (L),
3486 Selector_Name =>
3487 New_Reference_To (Controller_Component (T), Loc)),
3488 Selector_Name => Make_Identifier (Loc, Name_Prev));
3490 -- Last index before hole: determined by position of
3491 -- the _Controller.Prev component.
3493 Last_Before_Hole :=
3494 Make_Defining_Identifier (Loc,
3495 New_Internal_Name ('L'));
3497 Append_To (Res,
3498 Make_Object_Declaration (Loc,
3499 Defining_Identifier => Last_Before_Hole,
3500 Object_Definition => New_Occurrence_Of (
3501 RTE (RE_Storage_Offset), Loc),
3502 Constant_Present => True,
3503 Expression => Make_Op_Add (Loc,
3504 Make_Attribute_Reference (Loc,
3505 Prefix => Prev_Ref,
3506 Attribute_Name => Name_Position),
3507 Make_Attribute_Reference (Loc,
3508 Prefix => New_Copy_Tree (Prefix (Prev_Ref)),
3509 Attribute_Name => Name_Position))));
3511 -- Hole length: size of the Prev and Next components
3513 Hole_Length :=
3514 Make_Op_Multiply (Loc,
3515 Left_Opnd => Make_Integer_Literal (Loc, Uint_2),
3516 Right_Opnd =>
3517 Make_Op_Divide (Loc,
3518 Left_Opnd =>
3519 Make_Attribute_Reference (Loc,
3520 Prefix => New_Copy_Tree (Prev_Ref),
3521 Attribute_Name => Name_Size),
3522 Right_Opnd =>
3523 Make_Integer_Literal (Loc,
3524 Intval => System_Storage_Unit)));
3526 -- First index after hole
3528 First_After_Hole :=
3529 Make_Defining_Identifier (Loc,
3530 New_Internal_Name ('F'));
3532 Append_To (Res,
3533 Make_Object_Declaration (Loc,
3534 Defining_Identifier => First_After_Hole,
3535 Object_Definition => New_Occurrence_Of (
3536 RTE (RE_Storage_Offset), Loc),
3537 Constant_Present => True,
3538 Expression =>
3539 Make_Op_Add (Loc,
3540 Left_Opnd =>
3541 Make_Op_Add (Loc,
3542 Left_Opnd =>
3543 New_Occurrence_Of (Last_Before_Hole, Loc),
3544 Right_Opnd => Hole_Length),
3545 Right_Opnd => Make_Integer_Literal (Loc, 1))));
3547 Last_Before_Hole := New_Occurrence_Of (Last_Before_Hole, Loc);
3548 First_After_Hole := New_Occurrence_Of (First_After_Hole, Loc);
3549 end if;
3551 -- Assign the first slice (possibly skipping Root_Controlled,
3552 -- up to the beginning of the record controller if present,
3553 -- up to the end of the object if not).
3555 Append_To (Res, Make_Assignment_Statement (Loc,
3556 Name => Build_Slice (
3557 Rec => Duplicate_Subexpr_No_Checks (L),
3558 Lo => First_After_Root,
3559 Hi => Last_Before_Hole),
3561 Expression => Build_Slice (
3562 Rec => Expression (N),
3563 Lo => First_After_Root,
3564 Hi => New_Copy_Tree (Last_Before_Hole))));
3566 if Present (First_After_Hole) then
3568 -- If a record controller is present, copy the second slice,
3569 -- from right after the _Controller.Next component up to the
3570 -- end of the object.
3572 Append_To (Res, Make_Assignment_Statement (Loc,
3573 Name => Build_Slice (
3574 Rec => Duplicate_Subexpr_No_Checks (L),
3575 Lo => First_After_Hole,
3576 Hi => Empty),
3577 Expression => Build_Slice (
3578 Rec => Duplicate_Subexpr_No_Checks (Expression (N)),
3579 Lo => New_Copy_Tree (First_After_Hole),
3580 Hi => Empty)));
3581 end if;
3582 end Controlled_Actions;
3584 else
3585 Append_To (Res, Relocate_Node (N));
3586 end if;
3588 -- Restore the tag
3590 if Save_Tag then
3591 Append_To (Res,
3592 Make_Assignment_Statement (Loc,
3593 Name =>
3594 Make_Selected_Component (Loc,
3595 Prefix => Duplicate_Subexpr_No_Checks (L),
3596 Selector_Name => New_Reference_To (First_Tag_Component (T),
3597 Loc)),
3598 Expression => New_Reference_To (Tag_Tmp, Loc)));
3599 end if;
3601 -- Adjust the target after the assignment when controlled (not in the
3602 -- init proc since it is an initialization more than an assignment).
3604 if Ctrl_Act then
3605 Append_List_To (Res,
3606 Make_Adjust_Call (
3607 Ref => Duplicate_Subexpr_Move_Checks (L),
3608 Typ => Etype (L),
3609 Flist_Ref => New_Reference_To (RTE (RE_Global_Final_List), Loc),
3610 With_Attach => Make_Integer_Literal (Loc, 0)));
3611 end if;
3613 return Res;
3615 exception
3616 -- Could use comment here ???
3618 when RE_Not_Available =>
3619 return Empty_List;
3620 end Make_Tag_Ctrl_Assignment;
3622 ------------------------------------
3623 -- Possible_Bit_Aligned_Component --
3624 ------------------------------------
3626 function Possible_Bit_Aligned_Component (N : Node_Id) return Boolean is
3627 begin
3628 case Nkind (N) is
3630 -- Case of indexed component
3632 when N_Indexed_Component =>
3633 declare
3634 P : constant Node_Id := Prefix (N);
3635 Ptyp : constant Entity_Id := Etype (P);
3637 begin
3638 -- If we know the component size and it is less than 64, then
3639 -- we are definitely OK. The back end always does assignment
3640 -- of misaligned small objects correctly.
3642 if Known_Static_Component_Size (Ptyp)
3643 and then Component_Size (Ptyp) <= 64
3644 then
3645 return False;
3647 -- Otherwise, we need to test the prefix, to see if we are
3648 -- indexing from a possibly unaligned component.
3650 else
3651 return Possible_Bit_Aligned_Component (P);
3652 end if;
3653 end;
3655 -- Case of selected component
3657 when N_Selected_Component =>
3658 declare
3659 P : constant Node_Id := Prefix (N);
3660 Comp : constant Entity_Id := Entity (Selector_Name (N));
3662 begin
3663 -- If there is no component clause, then we are in the clear
3664 -- since the back end will never misalign a large component
3665 -- unless it is forced to do so. In the clear means we need
3666 -- only the recursive test on the prefix.
3668 if Component_May_Be_Bit_Aligned (Comp) then
3669 return True;
3670 else
3671 return Possible_Bit_Aligned_Component (P);
3672 end if;
3673 end;
3675 -- If we have neither a record nor array component, it means that
3676 -- we have fallen off the top testing prefixes recursively, and
3677 -- we now have a stand alone object, where we don't have a problem
3679 when others =>
3680 return False;
3682 end case;
3683 end Possible_Bit_Aligned_Component;
3685 end Exp_Ch5;