1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2010, Free Software Foundation, Inc. --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 3, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING3. If not, go to --
19 -- http://www.gnu.org/licenses for a complete copy of the license. --
21 -- GNAT was originally developed by the GNAT team at New York University. --
22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
24 ------------------------------------------------------------------------------
26 with Atree; use Atree;
27 with Checks; use Checks;
28 with Debug; use Debug;
29 with Einfo; use Einfo;
30 with Exp_Aggr; use Exp_Aggr;
31 with Exp_Ch6; use Exp_Ch6;
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 Namet; use Namet;
39 with Nlists; use Nlists;
40 with Nmake; use Nmake;
42 with Restrict; use Restrict;
43 with Rident; use Rident;
44 with Rtsfind; use Rtsfind;
45 with Sinfo; use Sinfo;
47 with Sem_Aux; use Sem_Aux;
48 with Sem_Ch3; use Sem_Ch3;
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 Targparm; use Targparm;
58 with Tbuild; use Tbuild;
59 with Ttypes; use Ttypes;
60 with Uintp; use Uintp;
61 with Validsw; use Validsw;
63 package body Exp_Ch5 is
65 function Change_Of_Representation (N : Node_Id) return Boolean;
66 -- Determine if the right hand side of the assignment N is a type
67 -- conversion which requires a change of representation. Called
68 -- only for the array and record cases.
70 procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id);
71 -- N is an assignment which assigns an array value. This routine process
72 -- the various special cases and checks required for such assignments,
73 -- including change of representation. Rhs is normally simply the right
74 -- hand side of the assignment, except that if the right hand side is
75 -- a type conversion or a qualified expression, then the Rhs is the
76 -- actual expression inside any such type conversions or qualifications.
78 function Expand_Assign_Array_Loop
85 Rev : Boolean) return Node_Id;
86 -- N is an assignment statement which assigns an array value. This routine
87 -- expands the assignment into a loop (or nested loops for the case of a
88 -- multi-dimensional array) to do the assignment component by component.
89 -- Larray and Rarray are the entities of the actual arrays on the left
90 -- hand and right hand sides. L_Type and R_Type are the types of these
91 -- arrays (which may not be the same, due to either sliding, or to a
92 -- change of representation case). Ndim is the number of dimensions and
93 -- the parameter Rev indicates if the loops run normally (Rev = False),
94 -- or reversed (Rev = True). The value returned is the constructed
95 -- loop statement. Auxiliary declarations are inserted before node N
96 -- using the standard Insert_Actions mechanism.
98 procedure Expand_Assign_Record (N : Node_Id);
99 -- N is an assignment of a non-tagged record value. This routine handles
100 -- the case where the assignment must be made component by component,
101 -- either because the target is not byte aligned, or there is a change
102 -- of representation, or when we have a tagged type with a representation
103 -- clause (this last case is required because holes in the tagged type
104 -- might be filled with components from child types).
106 procedure Expand_Iterator_Loop (N : Node_Id);
107 -- Expand loop over arrays and containers that uses the form "for X of C"
108 -- with an optional subtype mark, or "for Y in C".
110 procedure Expand_Predicated_Loop (N : Node_Id);
111 -- Expand for loop over predicated subtype
113 function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id;
114 -- Generate the necessary code for controlled and tagged assignment, that
115 -- is to say, finalization of the target before, adjustment of the target
116 -- after and save and restore of the tag and finalization pointers which
117 -- are not 'part of the value' and must not be changed upon assignment. N
118 -- is the original Assignment node.
120 ------------------------------
121 -- Change_Of_Representation --
122 ------------------------------
124 function Change_Of_Representation (N : Node_Id) return Boolean is
125 Rhs : constant Node_Id := Expression (N);
128 Nkind (Rhs) = N_Type_Conversion
130 not Same_Representation (Etype (Rhs), Etype (Expression (Rhs)));
131 end Change_Of_Representation;
133 -------------------------
134 -- Expand_Assign_Array --
135 -------------------------
137 -- There are two issues here. First, do we let Gigi do a block move, or
138 -- do we expand out into a loop? Second, we need to set the two flags
139 -- Forwards_OK and Backwards_OK which show whether the block move (or
140 -- corresponding loops) can be legitimately done in a forwards (low to
141 -- high) or backwards (high to low) manner.
143 procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id) is
144 Loc : constant Source_Ptr := Sloc (N);
146 Lhs : constant Node_Id := Name (N);
148 Act_Lhs : constant Node_Id := Get_Referenced_Object (Lhs);
149 Act_Rhs : Node_Id := Get_Referenced_Object (Rhs);
151 L_Type : constant Entity_Id :=
152 Underlying_Type (Get_Actual_Subtype (Act_Lhs));
153 R_Type : Entity_Id :=
154 Underlying_Type (Get_Actual_Subtype (Act_Rhs));
156 L_Slice : constant Boolean := Nkind (Act_Lhs) = N_Slice;
157 R_Slice : constant Boolean := Nkind (Act_Rhs) = N_Slice;
159 Crep : constant Boolean := Change_Of_Representation (N);
164 Ndim : constant Pos := Number_Dimensions (L_Type);
166 Loop_Required : Boolean := False;
167 -- This switch is set to True if the array move must be done using
168 -- an explicit front end generated loop.
170 procedure Apply_Dereference (Arg : Node_Id);
171 -- If the argument is an access to an array, and the assignment is
172 -- converted into a procedure call, apply explicit dereference.
174 function Has_Address_Clause (Exp : Node_Id) return Boolean;
175 -- Test if Exp is a reference to an array whose declaration has
176 -- an address clause, or it is a slice of such an array.
178 function Is_Formal_Array (Exp : Node_Id) return Boolean;
179 -- Test if Exp is a reference to an array which is either a formal
180 -- parameter or a slice of a formal parameter. These are the cases
181 -- where hidden aliasing can occur.
183 function Is_Non_Local_Array (Exp : Node_Id) return Boolean;
184 -- Determine if Exp is a reference to an array variable which is other
185 -- than an object defined in the current scope, or a slice of such
186 -- an object. Such objects can be aliased to parameters (unlike local
187 -- array references).
189 -----------------------
190 -- Apply_Dereference --
191 -----------------------
193 procedure Apply_Dereference (Arg : Node_Id) is
194 Typ : constant Entity_Id := Etype (Arg);
196 if Is_Access_Type (Typ) then
197 Rewrite (Arg, Make_Explicit_Dereference (Loc,
198 Prefix => Relocate_Node (Arg)));
199 Analyze_And_Resolve (Arg, Designated_Type (Typ));
201 end Apply_Dereference;
203 ------------------------
204 -- Has_Address_Clause --
205 ------------------------
207 function Has_Address_Clause (Exp : Node_Id) return Boolean is
210 (Is_Entity_Name (Exp) and then
211 Present (Address_Clause (Entity (Exp))))
213 (Nkind (Exp) = N_Slice and then Has_Address_Clause (Prefix (Exp)));
214 end Has_Address_Clause;
216 ---------------------
217 -- Is_Formal_Array --
218 ---------------------
220 function Is_Formal_Array (Exp : Node_Id) return Boolean is
223 (Is_Entity_Name (Exp) and then Is_Formal (Entity (Exp)))
225 (Nkind (Exp) = N_Slice and then Is_Formal_Array (Prefix (Exp)));
228 ------------------------
229 -- Is_Non_Local_Array --
230 ------------------------
232 function Is_Non_Local_Array (Exp : Node_Id) return Boolean is
234 return (Is_Entity_Name (Exp)
235 and then Scope (Entity (Exp)) /= Current_Scope)
236 or else (Nkind (Exp) = N_Slice
237 and then Is_Non_Local_Array (Prefix (Exp)));
238 end Is_Non_Local_Array;
240 -- Determine if Lhs, Rhs are formal arrays or nonlocal arrays
242 Lhs_Formal : constant Boolean := Is_Formal_Array (Act_Lhs);
243 Rhs_Formal : constant Boolean := Is_Formal_Array (Act_Rhs);
245 Lhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Lhs);
246 Rhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Rhs);
248 -- Start of processing for Expand_Assign_Array
251 -- Deal with length check. Note that the length check is done with
252 -- respect to the right hand side as given, not a possible underlying
253 -- renamed object, since this would generate incorrect extra checks.
255 Apply_Length_Check (Rhs, L_Type);
257 -- We start by assuming that the move can be done in either direction,
258 -- i.e. that the two sides are completely disjoint.
260 Set_Forwards_OK (N, True);
261 Set_Backwards_OK (N, True);
263 -- Normally it is only the slice case that can lead to overlap, and
264 -- explicit checks for slices are made below. But there is one case
265 -- where the slice can be implicit and invisible to us: when we have a
266 -- one dimensional array, and either both operands are parameters, or
267 -- one is a parameter (which can be a slice passed by reference) and the
268 -- other is a non-local variable. In this case the parameter could be a
269 -- slice that overlaps with the other operand.
271 -- However, if the array subtype is a constrained first subtype in the
272 -- parameter case, then we don't have to worry about overlap, since
273 -- slice assignments aren't possible (other than for a slice denoting
276 -- Note: No overlap is possible if there is a change of representation,
277 -- so we can exclude this case.
282 ((Lhs_Formal and Rhs_Formal)
284 (Lhs_Formal and Rhs_Non_Local_Var)
286 (Rhs_Formal and Lhs_Non_Local_Var))
288 (not Is_Constrained (Etype (Lhs))
289 or else not Is_First_Subtype (Etype (Lhs)))
291 -- In the case of compiling for the Java or .NET Virtual Machine,
292 -- slices are always passed by making a copy, so we don't have to
293 -- worry about overlap. We also want to prevent generation of "<"
294 -- comparisons for array addresses, since that's a meaningless
295 -- operation on the VM.
297 and then VM_Target = No_VM
299 Set_Forwards_OK (N, False);
300 Set_Backwards_OK (N, False);
302 -- Note: the bit-packed case is not worrisome here, since if we have
303 -- a slice passed as a parameter, it is always aligned on a byte
304 -- boundary, and if there are no explicit slices, the assignment
305 -- can be performed directly.
308 -- If either operand has an address clause clear Backwards_OK and
309 -- Forwards_OK, since we cannot tell if the operands overlap. We
310 -- exclude this treatment when Rhs is an aggregate, since we know
311 -- that overlap can't occur.
313 if (Has_Address_Clause (Lhs) and then Nkind (Rhs) /= N_Aggregate)
314 or else Has_Address_Clause (Rhs)
316 Set_Forwards_OK (N, False);
317 Set_Backwards_OK (N, False);
320 -- We certainly must use a loop for change of representation and also
321 -- we use the operand of the conversion on the right hand side as the
322 -- effective right hand side (the component types must match in this
326 Act_Rhs := Get_Referenced_Object (Rhs);
327 R_Type := Get_Actual_Subtype (Act_Rhs);
328 Loop_Required := True;
330 -- We require a loop if the left side is possibly bit unaligned
332 elsif Possible_Bit_Aligned_Component (Lhs)
334 Possible_Bit_Aligned_Component (Rhs)
336 Loop_Required := True;
338 -- Arrays with controlled components are expanded into a loop to force
339 -- calls to Adjust at the component level.
341 elsif Has_Controlled_Component (L_Type) then
342 Loop_Required := True;
344 -- If object is atomic, we cannot tolerate a loop
346 elsif Is_Atomic_Object (Act_Lhs)
348 Is_Atomic_Object (Act_Rhs)
352 -- Loop is required if we have atomic components since we have to
353 -- be sure to do any accesses on an element by element basis.
355 elsif Has_Atomic_Components (L_Type)
356 or else Has_Atomic_Components (R_Type)
357 or else Is_Atomic (Component_Type (L_Type))
358 or else Is_Atomic (Component_Type (R_Type))
360 Loop_Required := True;
362 -- Case where no slice is involved
364 elsif not L_Slice and not R_Slice then
366 -- The following code deals with the case of unconstrained bit packed
367 -- arrays. The problem is that the template for such arrays contains
368 -- the bounds of the actual source level array, but the copy of an
369 -- entire array requires the bounds of the underlying array. It would
370 -- be nice if the back end could take care of this, but right now it
371 -- does not know how, so if we have such a type, then we expand out
372 -- into a loop, which is inefficient but works correctly. If we don't
373 -- do this, we get the wrong length computed for the array to be
374 -- moved. The two cases we need to worry about are:
376 -- Explicit dereference of an unconstrained packed array type as in
377 -- the following example:
380 -- type BITS is array(INTEGER range <>) of BOOLEAN;
381 -- pragma PACK(BITS);
382 -- type A is access BITS;
385 -- P1 := new BITS (1 .. 65_535);
386 -- P2 := new BITS (1 .. 65_535);
390 -- A formal parameter reference with an unconstrained bit array type
391 -- is the other case we need to worry about (here we assume the same
392 -- BITS type declared above):
394 -- procedure Write_All (File : out BITS; Contents : BITS);
396 -- File.Storage := Contents;
399 -- We expand to a loop in either of these two cases
401 -- Question for future thought. Another potentially more efficient
402 -- approach would be to create the actual subtype, and then do an
403 -- unchecked conversion to this actual subtype ???
405 Check_Unconstrained_Bit_Packed_Array : declare
407 function Is_UBPA_Reference (Opnd : Node_Id) return Boolean;
408 -- Function to perform required test for the first case, above
409 -- (dereference of an unconstrained bit packed array).
411 -----------------------
412 -- Is_UBPA_Reference --
413 -----------------------
415 function Is_UBPA_Reference (Opnd : Node_Id) return Boolean is
416 Typ : constant Entity_Id := Underlying_Type (Etype (Opnd));
418 Des_Type : Entity_Id;
421 if Present (Packed_Array_Type (Typ))
422 and then Is_Array_Type (Packed_Array_Type (Typ))
423 and then not Is_Constrained (Packed_Array_Type (Typ))
427 elsif Nkind (Opnd) = N_Explicit_Dereference then
428 P_Type := Underlying_Type (Etype (Prefix (Opnd)));
430 if not Is_Access_Type (P_Type) then
434 Des_Type := Designated_Type (P_Type);
436 Is_Bit_Packed_Array (Des_Type)
437 and then not Is_Constrained (Des_Type);
443 end Is_UBPA_Reference;
445 -- Start of processing for Check_Unconstrained_Bit_Packed_Array
448 if Is_UBPA_Reference (Lhs)
450 Is_UBPA_Reference (Rhs)
452 Loop_Required := True;
454 -- Here if we do not have the case of a reference to a bit packed
455 -- unconstrained array case. In this case gigi can most certainly
456 -- handle the assignment if a forwards move is allowed.
458 -- (could it handle the backwards case also???)
460 elsif Forwards_OK (N) then
463 end Check_Unconstrained_Bit_Packed_Array;
465 -- The back end can always handle the assignment if the right side is a
466 -- string literal (note that overlap is definitely impossible in this
467 -- case). If the type is packed, a string literal is always converted
468 -- into an aggregate, except in the case of a null slice, for which no
469 -- aggregate can be written. In that case, rewrite the assignment as a
470 -- null statement, a length check has already been emitted to verify
471 -- that the range of the left-hand side is empty.
473 -- Note that this code is not executed if we have an assignment of a
474 -- string literal to a non-bit aligned component of a record, a case
475 -- which cannot be handled by the backend.
477 elsif Nkind (Rhs) = N_String_Literal then
478 if String_Length (Strval (Rhs)) = 0
479 and then Is_Bit_Packed_Array (L_Type)
481 Rewrite (N, Make_Null_Statement (Loc));
487 -- If either operand is bit packed, then we need a loop, since we can't
488 -- be sure that the slice is byte aligned. Similarly, if either operand
489 -- is a possibly unaligned slice, then we need a loop (since the back
490 -- end cannot handle unaligned slices).
492 elsif Is_Bit_Packed_Array (L_Type)
493 or else Is_Bit_Packed_Array (R_Type)
494 or else Is_Possibly_Unaligned_Slice (Lhs)
495 or else Is_Possibly_Unaligned_Slice (Rhs)
497 Loop_Required := True;
499 -- If we are not bit-packed, and we have only one slice, then no overlap
500 -- is possible except in the parameter case, so we can let the back end
503 elsif not (L_Slice and R_Slice) then
504 if Forwards_OK (N) then
509 -- If the right-hand side is a string literal, introduce a temporary for
510 -- it, for use in the generated loop that will follow.
512 if Nkind (Rhs) = N_String_Literal then
514 Temp : constant Entity_Id := Make_Temporary (Loc, 'T', Rhs);
519 Make_Object_Declaration (Loc,
520 Defining_Identifier => Temp,
521 Object_Definition => New_Occurrence_Of (L_Type, Loc),
522 Expression => Relocate_Node (Rhs));
524 Insert_Action (N, Decl);
525 Rewrite (Rhs, New_Occurrence_Of (Temp, Loc));
526 R_Type := Etype (Temp);
530 -- Come here to complete the analysis
532 -- Loop_Required: Set to True if we know that a loop is required
533 -- regardless of overlap considerations.
535 -- Forwards_OK: Set to False if we already know that a forwards
536 -- move is not safe, else set to True.
538 -- Backwards_OK: Set to False if we already know that a backwards
539 -- move is not safe, else set to True
541 -- Our task at this stage is to complete the overlap analysis, which can
542 -- result in possibly setting Forwards_OK or Backwards_OK to False, and
543 -- then generating the final code, either by deciding that it is OK
544 -- after all to let Gigi handle it, or by generating appropriate code
548 L_Index_Typ : constant Node_Id := Etype (First_Index (L_Type));
549 R_Index_Typ : constant Node_Id := Etype (First_Index (R_Type));
551 Left_Lo : constant Node_Id := Type_Low_Bound (L_Index_Typ);
552 Left_Hi : constant Node_Id := Type_High_Bound (L_Index_Typ);
553 Right_Lo : constant Node_Id := Type_Low_Bound (R_Index_Typ);
554 Right_Hi : constant Node_Id := Type_High_Bound (R_Index_Typ);
556 Act_L_Array : Node_Id;
557 Act_R_Array : Node_Id;
563 Cresult : Compare_Result;
566 -- Get the expressions for the arrays. If we are dealing with a
567 -- private type, then convert to the underlying type. We can do
568 -- direct assignments to an array that is a private type, but we
569 -- cannot assign to elements of the array without this extra
570 -- unchecked conversion.
572 -- Note: We propagate Parent to the conversion nodes to generate
573 -- a well-formed subtree.
575 if Nkind (Act_Lhs) = N_Slice then
576 Larray := Prefix (Act_Lhs);
580 if Is_Private_Type (Etype (Larray)) then
582 Par : constant Node_Id := Parent (Larray);
586 (Underlying_Type (Etype (Larray)), Larray);
587 Set_Parent (Larray, Par);
592 if Nkind (Act_Rhs) = N_Slice then
593 Rarray := Prefix (Act_Rhs);
597 if Is_Private_Type (Etype (Rarray)) then
599 Par : constant Node_Id := Parent (Rarray);
603 (Underlying_Type (Etype (Rarray)), Rarray);
604 Set_Parent (Rarray, Par);
609 -- If both sides are slices, we must figure out whether it is safe
610 -- to do the move in one direction or the other. It is always safe
611 -- if there is a change of representation since obviously two arrays
612 -- with different representations cannot possibly overlap.
614 if (not Crep) and L_Slice and R_Slice then
615 Act_L_Array := Get_Referenced_Object (Prefix (Act_Lhs));
616 Act_R_Array := Get_Referenced_Object (Prefix (Act_Rhs));
618 -- If both left and right hand arrays are entity names, and refer
619 -- to different entities, then we know that the move is safe (the
620 -- two storage areas are completely disjoint).
622 if Is_Entity_Name (Act_L_Array)
623 and then Is_Entity_Name (Act_R_Array)
624 and then Entity (Act_L_Array) /= Entity (Act_R_Array)
628 -- Otherwise, we assume the worst, which is that the two arrays
629 -- are the same array. There is no need to check if we know that
630 -- is the case, because if we don't know it, we still have to
633 -- Generally if the same array is involved, then we have an
634 -- overlapping case. We will have to really assume the worst (i.e.
635 -- set neither of the OK flags) unless we can determine the lower
636 -- or upper bounds at compile time and compare them.
641 (Left_Lo, Right_Lo, Assume_Valid => True);
643 if Cresult = Unknown then
646 (Left_Hi, Right_Hi, Assume_Valid => True);
650 when LT | LE | EQ => Set_Backwards_OK (N, False);
651 when GT | GE => Set_Forwards_OK (N, False);
652 when NE | Unknown => Set_Backwards_OK (N, False);
653 Set_Forwards_OK (N, False);
658 -- If after that analysis Loop_Required is False, meaning that we
659 -- have not discovered some non-overlap reason for requiring a loop,
660 -- then the outcome depends on the capabilities of the back end.
662 if not Loop_Required then
664 -- The GCC back end can deal with all cases of overlap by falling
665 -- back to memmove if it cannot use a more efficient approach.
667 if VM_Target = No_VM and not AAMP_On_Target then
670 -- Assume other back ends can handle it if Forwards_OK is set
672 elsif Forwards_OK (N) then
675 -- If Forwards_OK is not set, the back end will need something
676 -- like memmove to handle the move. For now, this processing is
677 -- activated using the .s debug flag (-gnatd.s).
679 elsif Debug_Flag_Dot_S then
684 -- At this stage we have to generate an explicit loop, and we have
685 -- the following cases:
687 -- Forwards_OK = True
689 -- Rnn : right_index := right_index'First;
690 -- for Lnn in left-index loop
691 -- left (Lnn) := right (Rnn);
692 -- Rnn := right_index'Succ (Rnn);
695 -- Note: the above code MUST be analyzed with checks off, because
696 -- otherwise the Succ could overflow. But in any case this is more
699 -- Forwards_OK = False, Backwards_OK = True
701 -- Rnn : right_index := right_index'Last;
702 -- for Lnn in reverse left-index loop
703 -- left (Lnn) := right (Rnn);
704 -- Rnn := right_index'Pred (Rnn);
707 -- Note: the above code MUST be analyzed with checks off, because
708 -- otherwise the Pred could overflow. But in any case this is more
711 -- Forwards_OK = Backwards_OK = False
713 -- This only happens if we have the same array on each side. It is
714 -- possible to create situations using overlays that violate this,
715 -- but we simply do not promise to get this "right" in this case.
717 -- There are two possible subcases. If the No_Implicit_Conditionals
718 -- restriction is set, then we generate the following code:
721 -- T : constant <operand-type> := rhs;
726 -- If implicit conditionals are permitted, then we generate:
728 -- if Left_Lo <= Right_Lo then
729 -- <code for Forwards_OK = True above>
731 -- <code for Backwards_OK = True above>
734 -- In order to detect possible aliasing, we examine the renamed
735 -- expression when the source or target is a renaming. However,
736 -- the renaming may be intended to capture an address that may be
737 -- affected by subsequent code, and therefore we must recover
738 -- the actual entity for the expansion that follows, not the
739 -- object it renames. In particular, if source or target designate
740 -- a portion of a dynamically allocated object, the pointer to it
741 -- may be reassigned but the renaming preserves the proper location.
743 if Is_Entity_Name (Rhs)
745 Nkind (Parent (Entity (Rhs))) = N_Object_Renaming_Declaration
746 and then Nkind (Act_Rhs) = N_Slice
751 if Is_Entity_Name (Lhs)
753 Nkind (Parent (Entity (Lhs))) = N_Object_Renaming_Declaration
754 and then Nkind (Act_Lhs) = N_Slice
759 -- Cases where either Forwards_OK or Backwards_OK is true
761 if Forwards_OK (N) or else Backwards_OK (N) then
762 if Needs_Finalization (Component_Type (L_Type))
763 and then Base_Type (L_Type) = Base_Type (R_Type)
765 and then not No_Ctrl_Actions (N)
768 Proc : constant Entity_Id :=
769 TSS (Base_Type (L_Type), TSS_Slice_Assign);
773 Apply_Dereference (Larray);
774 Apply_Dereference (Rarray);
775 Actuals := New_List (
776 Duplicate_Subexpr (Larray, Name_Req => True),
777 Duplicate_Subexpr (Rarray, Name_Req => True),
778 Duplicate_Subexpr (Left_Lo, Name_Req => True),
779 Duplicate_Subexpr (Left_Hi, Name_Req => True),
780 Duplicate_Subexpr (Right_Lo, Name_Req => True),
781 Duplicate_Subexpr (Right_Hi, Name_Req => True));
785 Boolean_Literals (not Forwards_OK (N)), Loc));
788 Make_Procedure_Call_Statement (Loc,
789 Name => New_Reference_To (Proc, Loc),
790 Parameter_Associations => Actuals));
795 Expand_Assign_Array_Loop
796 (N, Larray, Rarray, L_Type, R_Type, Ndim,
797 Rev => not Forwards_OK (N)));
800 -- Case of both are false with No_Implicit_Conditionals
802 elsif Restriction_Active (No_Implicit_Conditionals) then
804 T : constant Entity_Id :=
805 Make_Defining_Identifier (Loc, Chars => Name_T);
809 Make_Block_Statement (Loc,
810 Declarations => New_List (
811 Make_Object_Declaration (Loc,
812 Defining_Identifier => T,
813 Constant_Present => True,
815 New_Occurrence_Of (Etype (Rhs), Loc),
816 Expression => Relocate_Node (Rhs))),
818 Handled_Statement_Sequence =>
819 Make_Handled_Sequence_Of_Statements (Loc,
820 Statements => New_List (
821 Make_Assignment_Statement (Loc,
822 Name => Relocate_Node (Lhs),
823 Expression => New_Occurrence_Of (T, Loc))))));
826 -- Case of both are false with implicit conditionals allowed
829 -- Before we generate this code, we must ensure that the left and
830 -- right side array types are defined. They may be itypes, and we
831 -- cannot let them be defined inside the if, since the first use
832 -- in the then may not be executed.
834 Ensure_Defined (L_Type, N);
835 Ensure_Defined (R_Type, N);
837 -- We normally compare addresses to find out which way round to
838 -- do the loop, since this is reliable, and handles the cases of
839 -- parameters, conversions etc. But we can't do that in the bit
840 -- packed case or the VM case, because addresses don't work there.
842 if not Is_Bit_Packed_Array (L_Type) and then VM_Target = No_VM then
846 Unchecked_Convert_To (RTE (RE_Integer_Address),
847 Make_Attribute_Reference (Loc,
849 Make_Indexed_Component (Loc,
851 Duplicate_Subexpr_Move_Checks (Larray, True),
852 Expressions => New_List (
853 Make_Attribute_Reference (Loc,
857 Attribute_Name => Name_First))),
858 Attribute_Name => Name_Address)),
861 Unchecked_Convert_To (RTE (RE_Integer_Address),
862 Make_Attribute_Reference (Loc,
864 Make_Indexed_Component (Loc,
866 Duplicate_Subexpr_Move_Checks (Rarray, True),
867 Expressions => New_List (
868 Make_Attribute_Reference (Loc,
872 Attribute_Name => Name_First))),
873 Attribute_Name => Name_Address)));
875 -- For the bit packed and VM cases we use the bounds. That's OK,
876 -- because we don't have to worry about parameters, since they
877 -- cannot cause overlap. Perhaps we should worry about weird slice
883 Cleft_Lo := New_Copy_Tree (Left_Lo);
884 Cright_Lo := New_Copy_Tree (Right_Lo);
886 -- If the types do not match we add an implicit conversion
887 -- here to ensure proper match
889 if Etype (Left_Lo) /= Etype (Right_Lo) then
891 Unchecked_Convert_To (Etype (Left_Lo), Cright_Lo);
894 -- Reset the Analyzed flag, because the bounds of the index
895 -- type itself may be universal, and must must be reaanalyzed
896 -- to acquire the proper type for the back end.
898 Set_Analyzed (Cleft_Lo, False);
899 Set_Analyzed (Cright_Lo, False);
903 Left_Opnd => Cleft_Lo,
904 Right_Opnd => Cright_Lo);
907 if Needs_Finalization (Component_Type (L_Type))
908 and then Base_Type (L_Type) = Base_Type (R_Type)
910 and then not No_Ctrl_Actions (N)
913 -- Call TSS procedure for array assignment, passing the
914 -- explicit bounds of right and left hand sides.
917 Proc : constant Entity_Id :=
918 TSS (Base_Type (L_Type), TSS_Slice_Assign);
922 Apply_Dereference (Larray);
923 Apply_Dereference (Rarray);
924 Actuals := New_List (
925 Duplicate_Subexpr (Larray, Name_Req => True),
926 Duplicate_Subexpr (Rarray, Name_Req => True),
927 Duplicate_Subexpr (Left_Lo, Name_Req => True),
928 Duplicate_Subexpr (Left_Hi, Name_Req => True),
929 Duplicate_Subexpr (Right_Lo, Name_Req => True),
930 Duplicate_Subexpr (Right_Hi, Name_Req => True));
934 Right_Opnd => Condition));
937 Make_Procedure_Call_Statement (Loc,
938 Name => New_Reference_To (Proc, Loc),
939 Parameter_Associations => Actuals));
944 Make_Implicit_If_Statement (N,
945 Condition => Condition,
947 Then_Statements => New_List (
948 Expand_Assign_Array_Loop
949 (N, Larray, Rarray, L_Type, R_Type, Ndim,
952 Else_Statements => New_List (
953 Expand_Assign_Array_Loop
954 (N, Larray, Rarray, L_Type, R_Type, Ndim,
959 Analyze (N, Suppress => All_Checks);
963 when RE_Not_Available =>
965 end Expand_Assign_Array;
967 ------------------------------
968 -- Expand_Assign_Array_Loop --
969 ------------------------------
971 -- The following is an example of the loop generated for the case of a
972 -- two-dimensional array:
977 -- for L1b in 1 .. 100 loop
981 -- for L3b in 1 .. 100 loop
982 -- vm1 (L1b, L3b) := vm2 (R2b, R4b);
983 -- R4b := Tm1X2'succ(R4b);
986 -- R2b := Tm1X1'succ(R2b);
990 -- Here Rev is False, and Tm1Xn are the subscript types for the right hand
991 -- side. The declarations of R2b and R4b are inserted before the original
992 -- assignment statement.
994 function Expand_Assign_Array_Loop
1001 Rev : Boolean) return Node_Id
1003 Loc : constant Source_Ptr := Sloc (N);
1005 Lnn : array (1 .. Ndim) of Entity_Id;
1006 Rnn : array (1 .. Ndim) of Entity_Id;
1007 -- Entities used as subscripts on left and right sides
1009 L_Index_Type : array (1 .. Ndim) of Entity_Id;
1010 R_Index_Type : array (1 .. Ndim) of Entity_Id;
1011 -- Left and right index types
1018 function Build_Step (J : Nat) return Node_Id;
1019 -- The increment step for the index of the right-hand side is written
1020 -- as an attribute reference (Succ or Pred). This function returns
1021 -- the corresponding node, which is placed at the end of the loop body.
1027 function Build_Step (J : Nat) return Node_Id is
1039 Make_Assignment_Statement (Loc,
1040 Name => New_Occurrence_Of (Rnn (J), Loc),
1042 Make_Attribute_Reference (Loc,
1044 New_Occurrence_Of (R_Index_Type (J), Loc),
1045 Attribute_Name => S_Or_P,
1046 Expressions => New_List (
1047 New_Occurrence_Of (Rnn (J), Loc))));
1049 -- Note that on the last iteration of the loop, the index is increased
1050 -- (or decreased) past the corresponding bound. This is consistent with
1051 -- the C semantics of the back-end, where such an off-by-one value on a
1052 -- dead index variable is OK. However, in CodePeer mode this leads to
1053 -- spurious warnings, and thus we place a guard around the attribute
1054 -- reference. For obvious reasons we only do this for CodePeer.
1056 if CodePeer_Mode then
1058 Make_If_Statement (Loc,
1061 Left_Opnd => New_Occurrence_Of (Lnn (J), Loc),
1063 Make_Attribute_Reference (Loc,
1064 Prefix => New_Occurrence_Of (L_Index_Type (J), Loc),
1065 Attribute_Name => Lim)),
1066 Then_Statements => New_List (Step));
1072 -- Start of processing for Expand_Assign_Array_Loop
1076 F_Or_L := Name_Last;
1077 S_Or_P := Name_Pred;
1079 F_Or_L := Name_First;
1080 S_Or_P := Name_Succ;
1083 -- Setup index types and subscript entities
1090 L_Index := First_Index (L_Type);
1091 R_Index := First_Index (R_Type);
1093 for J in 1 .. Ndim loop
1094 Lnn (J) := Make_Temporary (Loc, 'L');
1095 Rnn (J) := Make_Temporary (Loc, 'R');
1097 L_Index_Type (J) := Etype (L_Index);
1098 R_Index_Type (J) := Etype (R_Index);
1100 Next_Index (L_Index);
1101 Next_Index (R_Index);
1105 -- Now construct the assignment statement
1108 ExprL : constant List_Id := New_List;
1109 ExprR : constant List_Id := New_List;
1112 for J in 1 .. Ndim loop
1113 Append_To (ExprL, New_Occurrence_Of (Lnn (J), Loc));
1114 Append_To (ExprR, New_Occurrence_Of (Rnn (J), Loc));
1118 Make_Assignment_Statement (Loc,
1120 Make_Indexed_Component (Loc,
1121 Prefix => Duplicate_Subexpr (Larray, Name_Req => True),
1122 Expressions => ExprL),
1124 Make_Indexed_Component (Loc,
1125 Prefix => Duplicate_Subexpr (Rarray, Name_Req => True),
1126 Expressions => ExprR));
1128 -- We set assignment OK, since there are some cases, e.g. in object
1129 -- declarations, where we are actually assigning into a constant.
1130 -- If there really is an illegality, it was caught long before now,
1131 -- and was flagged when the original assignment was analyzed.
1133 Set_Assignment_OK (Name (Assign));
1135 -- Propagate the No_Ctrl_Actions flag to individual assignments
1137 Set_No_Ctrl_Actions (Assign, No_Ctrl_Actions (N));
1140 -- Now construct the loop from the inside out, with the last subscript
1141 -- varying most rapidly. Note that Assign is first the raw assignment
1142 -- statement, and then subsequently the loop that wraps it up.
1144 for J in reverse 1 .. Ndim loop
1146 Make_Block_Statement (Loc,
1147 Declarations => New_List (
1148 Make_Object_Declaration (Loc,
1149 Defining_Identifier => Rnn (J),
1150 Object_Definition =>
1151 New_Occurrence_Of (R_Index_Type (J), Loc),
1153 Make_Attribute_Reference (Loc,
1154 Prefix => New_Occurrence_Of (R_Index_Type (J), Loc),
1155 Attribute_Name => F_Or_L))),
1157 Handled_Statement_Sequence =>
1158 Make_Handled_Sequence_Of_Statements (Loc,
1159 Statements => New_List (
1160 Make_Implicit_Loop_Statement (N,
1162 Make_Iteration_Scheme (Loc,
1163 Loop_Parameter_Specification =>
1164 Make_Loop_Parameter_Specification (Loc,
1165 Defining_Identifier => Lnn (J),
1166 Reverse_Present => Rev,
1167 Discrete_Subtype_Definition =>
1168 New_Reference_To (L_Index_Type (J), Loc))),
1170 Statements => New_List (Assign, Build_Step (J))))));
1174 end Expand_Assign_Array_Loop;
1176 --------------------------
1177 -- Expand_Assign_Record --
1178 --------------------------
1180 procedure Expand_Assign_Record (N : Node_Id) is
1181 Lhs : constant Node_Id := Name (N);
1182 Rhs : Node_Id := Expression (N);
1183 L_Typ : constant Entity_Id := Base_Type (Etype (Lhs));
1186 -- If change of representation, then extract the real right hand side
1187 -- from the type conversion, and proceed with component-wise assignment,
1188 -- since the two types are not the same as far as the back end is
1191 if Change_Of_Representation (N) then
1192 Rhs := Expression (Rhs);
1194 -- If this may be a case of a large bit aligned component, then proceed
1195 -- with component-wise assignment, to avoid possible clobbering of other
1196 -- components sharing bits in the first or last byte of the component to
1199 elsif Possible_Bit_Aligned_Component (Lhs)
1201 Possible_Bit_Aligned_Component (Rhs)
1205 -- If we have a tagged type that has a complete record representation
1206 -- clause, we must do we must do component-wise assignments, since child
1207 -- types may have used gaps for their components, and we might be
1208 -- dealing with a view conversion.
1210 elsif Is_Fully_Repped_Tagged_Type (L_Typ) then
1213 -- If neither condition met, then nothing special to do, the back end
1214 -- can handle assignment of the entire component as a single entity.
1220 -- At this stage we know that we must do a component wise assignment
1223 Loc : constant Source_Ptr := Sloc (N);
1224 R_Typ : constant Entity_Id := Base_Type (Etype (Rhs));
1225 Decl : constant Node_Id := Declaration_Node (R_Typ);
1229 function Find_Component
1231 Comp : Entity_Id) return Entity_Id;
1232 -- Find the component with the given name in the underlying record
1233 -- declaration for Typ. We need to use the actual entity because the
1234 -- type may be private and resolution by identifier alone would fail.
1236 function Make_Component_List_Assign
1238 U_U : Boolean := False) return List_Id;
1239 -- Returns a sequence of statements to assign the components that
1240 -- are referenced in the given component list. The flag U_U is
1241 -- used to force the usage of the inferred value of the variant
1242 -- part expression as the switch for the generated case statement.
1244 function Make_Field_Assign
1246 U_U : Boolean := False) return Node_Id;
1247 -- Given C, the entity for a discriminant or component, build an
1248 -- assignment for the corresponding field values. The flag U_U
1249 -- signals the presence of an Unchecked_Union and forces the usage
1250 -- of the inferred discriminant value of C as the right hand side
1251 -- of the assignment.
1253 function Make_Field_Assigns (CI : List_Id) return List_Id;
1254 -- Given CI, a component items list, construct series of statements
1255 -- for fieldwise assignment of the corresponding components.
1257 --------------------
1258 -- Find_Component --
1259 --------------------
1261 function Find_Component
1263 Comp : Entity_Id) return Entity_Id
1265 Utyp : constant Entity_Id := Underlying_Type (Typ);
1269 C := First_Entity (Utyp);
1270 while Present (C) loop
1271 if Chars (C) = Chars (Comp) then
1278 raise Program_Error;
1281 --------------------------------
1282 -- Make_Component_List_Assign --
1283 --------------------------------
1285 function Make_Component_List_Assign
1287 U_U : Boolean := False) return List_Id
1289 CI : constant List_Id := Component_Items (CL);
1290 VP : constant Node_Id := Variant_Part (CL);
1300 Result := Make_Field_Assigns (CI);
1302 if Present (VP) then
1303 V := First_Non_Pragma (Variants (VP));
1305 while Present (V) loop
1307 DC := First (Discrete_Choices (V));
1308 while Present (DC) loop
1309 Append_To (DCH, New_Copy_Tree (DC));
1314 Make_Case_Statement_Alternative (Loc,
1315 Discrete_Choices => DCH,
1317 Make_Component_List_Assign (Component_List (V))));
1318 Next_Non_Pragma (V);
1321 -- If we have an Unchecked_Union, use the value of the inferred
1322 -- discriminant of the variant part expression as the switch
1323 -- for the case statement. The case statement may later be
1328 New_Copy (Get_Discriminant_Value (
1331 Discriminant_Constraint (Etype (Rhs))));
1334 Make_Selected_Component (Loc,
1335 Prefix => Duplicate_Subexpr (Rhs),
1337 Make_Identifier (Loc, Chars (Name (VP))));
1341 Make_Case_Statement (Loc,
1343 Alternatives => Alts));
1347 end Make_Component_List_Assign;
1349 -----------------------
1350 -- Make_Field_Assign --
1351 -----------------------
1353 function Make_Field_Assign
1355 U_U : Boolean := False) return Node_Id
1361 -- In the case of an Unchecked_Union, use the discriminant
1362 -- constraint value as on the right hand side of the assignment.
1366 New_Copy (Get_Discriminant_Value (C,
1368 Discriminant_Constraint (Etype (Rhs))));
1371 Make_Selected_Component (Loc,
1372 Prefix => Duplicate_Subexpr (Rhs),
1373 Selector_Name => New_Occurrence_Of (C, Loc));
1377 Make_Assignment_Statement (Loc,
1379 Make_Selected_Component (Loc,
1380 Prefix => Duplicate_Subexpr (Lhs),
1382 New_Occurrence_Of (Find_Component (L_Typ, C), Loc)),
1383 Expression => Expr);
1385 -- Set Assignment_OK, so discriminants can be assigned
1387 Set_Assignment_OK (Name (A), True);
1389 if Componentwise_Assignment (N)
1390 and then Nkind (Name (A)) = N_Selected_Component
1391 and then Chars (Selector_Name (Name (A))) = Name_uParent
1393 Set_Componentwise_Assignment (A);
1397 end Make_Field_Assign;
1399 ------------------------
1400 -- Make_Field_Assigns --
1401 ------------------------
1403 function Make_Field_Assigns (CI : List_Id) return List_Id is
1411 while Present (Item) loop
1413 -- Look for components, but exclude _tag field assignment if
1414 -- the special Componentwise_Assignment flag is set.
1416 if Nkind (Item) = N_Component_Declaration
1417 and then not (Is_Tag (Defining_Identifier (Item))
1418 and then Componentwise_Assignment (N))
1421 (Result, Make_Field_Assign (Defining_Identifier (Item)));
1428 end Make_Field_Assigns;
1430 -- Start of processing for Expand_Assign_Record
1433 -- Note that we use the base types for this processing. This results
1434 -- in some extra work in the constrained case, but the change of
1435 -- representation case is so unusual that it is not worth the effort.
1437 -- First copy the discriminants. This is done unconditionally. It
1438 -- is required in the unconstrained left side case, and also in the
1439 -- case where this assignment was constructed during the expansion
1440 -- of a type conversion (since initialization of discriminants is
1441 -- suppressed in this case). It is unnecessary but harmless in
1444 if Has_Discriminants (L_Typ) then
1445 F := First_Discriminant (R_Typ);
1446 while Present (F) loop
1448 -- If we are expanding the initialization of a derived record
1449 -- that constrains or renames discriminants of the parent, we
1450 -- must use the corresponding discriminant in the parent.
1457 and then Present (Corresponding_Discriminant (F))
1459 CF := Corresponding_Discriminant (F);
1464 if Is_Unchecked_Union (Base_Type (R_Typ)) then
1465 Insert_Action (N, Make_Field_Assign (CF, True));
1467 Insert_Action (N, Make_Field_Assign (CF));
1470 Next_Discriminant (F);
1475 -- We know the underlying type is a record, but its current view
1476 -- may be private. We must retrieve the usable record declaration.
1478 if Nkind_In (Decl, N_Private_Type_Declaration,
1479 N_Private_Extension_Declaration)
1480 and then Present (Full_View (R_Typ))
1482 RDef := Type_Definition (Declaration_Node (Full_View (R_Typ)));
1484 RDef := Type_Definition (Decl);
1487 if Nkind (RDef) = N_Derived_Type_Definition then
1488 RDef := Record_Extension_Part (RDef);
1491 if Nkind (RDef) = N_Record_Definition
1492 and then Present (Component_List (RDef))
1494 if Is_Unchecked_Union (R_Typ) then
1496 Make_Component_List_Assign (Component_List (RDef), True));
1499 (N, Make_Component_List_Assign (Component_List (RDef)));
1502 Rewrite (N, Make_Null_Statement (Loc));
1505 end Expand_Assign_Record;
1507 -----------------------------------
1508 -- Expand_N_Assignment_Statement --
1509 -----------------------------------
1511 -- This procedure implements various cases where an assignment statement
1512 -- cannot just be passed on to the back end in untransformed state.
1514 procedure Expand_N_Assignment_Statement (N : Node_Id) is
1515 Loc : constant Source_Ptr := Sloc (N);
1516 Lhs : constant Node_Id := Name (N);
1517 Rhs : constant Node_Id := Expression (N);
1518 Typ : constant Entity_Id := Underlying_Type (Etype (Lhs));
1522 -- Special case to check right away, if the Componentwise_Assignment
1523 -- flag is set, this is a reanalysis from the expansion of the primitive
1524 -- assignment procedure for a tagged type, and all we need to do is to
1525 -- expand to assignment of components, because otherwise, we would get
1526 -- infinite recursion (since this looks like a tagged assignment which
1527 -- would normally try to *call* the primitive assignment procedure).
1529 if Componentwise_Assignment (N) then
1530 Expand_Assign_Record (N);
1534 -- Defend against invalid subscripts on left side if we are in standard
1535 -- validity checking mode. No need to do this if we are checking all
1538 -- Note that we do this right away, because there are some early return
1539 -- paths in this procedure, and this is required on all paths.
1541 if Validity_Checks_On
1542 and then Validity_Check_Default
1543 and then not Validity_Check_Subscripts
1545 Check_Valid_Lvalue_Subscripts (Lhs);
1548 -- Ada 2005 (AI-327): Handle assignment to priority of protected object
1550 -- Rewrite an assignment to X'Priority into a run-time call
1552 -- For example: X'Priority := New_Prio_Expr;
1553 -- ...is expanded into Set_Ceiling (X._Object, New_Prio_Expr);
1555 -- Note that although X'Priority is notionally an object, it is quite
1556 -- deliberately not defined as an aliased object in the RM. This means
1557 -- that it works fine to rewrite it as a call, without having to worry
1558 -- about complications that would other arise from X'Priority'Access,
1559 -- which is illegal, because of the lack of aliasing.
1561 if Ada_Version >= Ada_2005 then
1564 Conctyp : Entity_Id;
1567 RT_Subprg_Name : Node_Id;
1570 -- Handle chains of renamings
1573 while Nkind (Ent) in N_Has_Entity
1574 and then Present (Entity (Ent))
1575 and then Present (Renamed_Object (Entity (Ent)))
1577 Ent := Renamed_Object (Entity (Ent));
1580 -- The attribute Priority applied to protected objects has been
1581 -- previously expanded into a call to the Get_Ceiling run-time
1584 if Nkind (Ent) = N_Function_Call
1585 and then (Entity (Name (Ent)) = RTE (RE_Get_Ceiling)
1587 Entity (Name (Ent)) = RTE (RO_PE_Get_Ceiling))
1589 -- Look for the enclosing concurrent type
1591 Conctyp := Current_Scope;
1592 while not Is_Concurrent_Type (Conctyp) loop
1593 Conctyp := Scope (Conctyp);
1596 pragma Assert (Is_Protected_Type (Conctyp));
1598 -- Generate the first actual of the call
1600 Subprg := Current_Scope;
1601 while not Present (Protected_Body_Subprogram (Subprg)) loop
1602 Subprg := Scope (Subprg);
1605 -- Select the appropriate run-time call
1607 if Number_Entries (Conctyp) = 0 then
1609 New_Reference_To (RTE (RE_Set_Ceiling), Loc);
1612 New_Reference_To (RTE (RO_PE_Set_Ceiling), Loc);
1616 Make_Procedure_Call_Statement (Loc,
1617 Name => RT_Subprg_Name,
1618 Parameter_Associations => New_List (
1619 New_Copy_Tree (First (Parameter_Associations (Ent))),
1620 Relocate_Node (Expression (N))));
1629 -- Deal with assignment checks unless suppressed
1631 if not Suppress_Assignment_Checks (N) then
1633 -- First deal with generation of range check if required
1635 if Do_Range_Check (Rhs) then
1636 Set_Do_Range_Check (Rhs, False);
1637 Generate_Range_Check (Rhs, Typ, CE_Range_Check_Failed);
1640 -- Then generate predicate check if required
1642 Apply_Predicate_Check (Rhs, Typ);
1645 -- Check for a special case where a high level transformation is
1646 -- required. If we have either of:
1651 -- where P is a reference to a bit packed array, then we have to unwind
1652 -- the assignment. The exact meaning of being a reference to a bit
1653 -- packed array is as follows:
1655 -- An indexed component whose prefix is a bit packed array is a
1656 -- reference to a bit packed array.
1658 -- An indexed component or selected component whose prefix is a
1659 -- reference to a bit packed array is itself a reference ot a
1660 -- bit packed array.
1662 -- The required transformation is
1664 -- Tnn : prefix_type := P;
1665 -- Tnn.field := rhs;
1670 -- Tnn : prefix_type := P;
1671 -- Tnn (subscr) := rhs;
1674 -- Since P is going to be evaluated more than once, any subscripts
1675 -- in P must have their evaluation forced.
1677 if Nkind_In (Lhs, N_Indexed_Component, N_Selected_Component)
1678 and then Is_Ref_To_Bit_Packed_Array (Prefix (Lhs))
1681 BPAR_Expr : constant Node_Id := Relocate_Node (Prefix (Lhs));
1682 BPAR_Typ : constant Entity_Id := Etype (BPAR_Expr);
1683 Tnn : constant Entity_Id :=
1684 Make_Temporary (Loc, 'T', BPAR_Expr);
1687 -- Insert the post assignment first, because we want to copy the
1688 -- BPAR_Expr tree before it gets analyzed in the context of the
1689 -- pre assignment. Note that we do not analyze the post assignment
1690 -- yet (we cannot till we have completed the analysis of the pre
1691 -- assignment). As usual, the analysis of this post assignment
1692 -- will happen on its own when we "run into" it after finishing
1693 -- the current assignment.
1696 Make_Assignment_Statement (Loc,
1697 Name => New_Copy_Tree (BPAR_Expr),
1698 Expression => New_Occurrence_Of (Tnn, Loc)));
1700 -- At this stage BPAR_Expr is a reference to a bit packed array
1701 -- where the reference was not expanded in the original tree,
1702 -- since it was on the left side of an assignment. But in the
1703 -- pre-assignment statement (the object definition), BPAR_Expr
1704 -- will end up on the right hand side, and must be reexpanded. To
1705 -- achieve this, we reset the analyzed flag of all selected and
1706 -- indexed components down to the actual indexed component for
1707 -- the packed array.
1711 Set_Analyzed (Exp, False);
1714 (Exp, N_Selected_Component, N_Indexed_Component)
1716 Exp := Prefix (Exp);
1722 -- Now we can insert and analyze the pre-assignment
1724 -- If the right-hand side requires a transient scope, it has
1725 -- already been placed on the stack. However, the declaration is
1726 -- inserted in the tree outside of this scope, and must reflect
1727 -- the proper scope for its variable. This awkward bit is forced
1728 -- by the stricter scope discipline imposed by GCC 2.97.
1731 Uses_Transient_Scope : constant Boolean :=
1733 and then N = Node_To_Be_Wrapped;
1736 if Uses_Transient_Scope then
1737 Push_Scope (Scope (Current_Scope));
1740 Insert_Before_And_Analyze (N,
1741 Make_Object_Declaration (Loc,
1742 Defining_Identifier => Tnn,
1743 Object_Definition => New_Occurrence_Of (BPAR_Typ, Loc),
1744 Expression => BPAR_Expr));
1746 if Uses_Transient_Scope then
1751 -- Now fix up the original assignment and continue processing
1753 Rewrite (Prefix (Lhs),
1754 New_Occurrence_Of (Tnn, Loc));
1756 -- We do not need to reanalyze that assignment, and we do not need
1757 -- to worry about references to the temporary, but we do need to
1758 -- make sure that the temporary is not marked as a true constant
1759 -- since we now have a generated assignment to it!
1761 Set_Is_True_Constant (Tnn, False);
1765 -- When we have the appropriate type of aggregate in the expression (it
1766 -- has been determined during analysis of the aggregate by setting the
1767 -- delay flag), let's perform in place assignment and thus avoid
1768 -- creating a temporary.
1770 if Is_Delayed_Aggregate (Rhs) then
1771 Convert_Aggr_In_Assignment (N);
1772 Rewrite (N, Make_Null_Statement (Loc));
1777 -- Apply discriminant check if required. If Lhs is an access type to a
1778 -- designated type with discriminants, we must always check.
1780 if Has_Discriminants (Etype (Lhs)) then
1782 -- Skip discriminant check if change of representation. Will be
1783 -- done when the change of representation is expanded out.
1785 if not Change_Of_Representation (N) then
1786 Apply_Discriminant_Check (Rhs, Etype (Lhs), Lhs);
1789 -- If the type is private without discriminants, and the full type
1790 -- has discriminants (necessarily with defaults) a check may still be
1791 -- necessary if the Lhs is aliased. The private determinants must be
1792 -- visible to build the discriminant constraints.
1793 -- What is a "determinant"???
1795 -- Only an explicit dereference that comes from source indicates
1796 -- aliasing. Access to formals of protected operations and entries
1797 -- create dereferences but are not semantic aliasings.
1799 elsif Is_Private_Type (Etype (Lhs))
1800 and then Has_Discriminants (Typ)
1801 and then Nkind (Lhs) = N_Explicit_Dereference
1802 and then Comes_From_Source (Lhs)
1805 Lt : constant Entity_Id := Etype (Lhs);
1807 Set_Etype (Lhs, Typ);
1808 Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs));
1809 Apply_Discriminant_Check (Rhs, Typ, Lhs);
1810 Set_Etype (Lhs, Lt);
1813 -- If the Lhs has a private type with unknown discriminants, it
1814 -- may have a full view with discriminants, but those are nameable
1815 -- only in the underlying type, so convert the Rhs to it before
1816 -- potential checking.
1818 elsif Has_Unknown_Discriminants (Base_Type (Etype (Lhs)))
1819 and then Has_Discriminants (Typ)
1821 Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs));
1822 Apply_Discriminant_Check (Rhs, Typ, Lhs);
1824 -- In the access type case, we need the same discriminant check, and
1825 -- also range checks if we have an access to constrained array.
1827 elsif Is_Access_Type (Etype (Lhs))
1828 and then Is_Constrained (Designated_Type (Etype (Lhs)))
1830 if Has_Discriminants (Designated_Type (Etype (Lhs))) then
1832 -- Skip discriminant check if change of representation. Will be
1833 -- done when the change of representation is expanded out.
1835 if not Change_Of_Representation (N) then
1836 Apply_Discriminant_Check (Rhs, Etype (Lhs));
1839 elsif Is_Array_Type (Designated_Type (Etype (Lhs))) then
1840 Apply_Range_Check (Rhs, Etype (Lhs));
1842 if Is_Constrained (Etype (Lhs)) then
1843 Apply_Length_Check (Rhs, Etype (Lhs));
1846 if Nkind (Rhs) = N_Allocator then
1848 Target_Typ : constant Entity_Id := Etype (Expression (Rhs));
1849 C_Es : Check_Result;
1856 Etype (Designated_Type (Etype (Lhs))));
1868 -- Apply range check for access type case
1870 elsif Is_Access_Type (Etype (Lhs))
1871 and then Nkind (Rhs) = N_Allocator
1872 and then Nkind (Expression (Rhs)) = N_Qualified_Expression
1874 Analyze_And_Resolve (Expression (Rhs));
1876 (Expression (Rhs), Designated_Type (Etype (Lhs)));
1879 -- Ada 2005 (AI-231): Generate the run-time check
1881 if Is_Access_Type (Typ)
1882 and then Can_Never_Be_Null (Etype (Lhs))
1883 and then not Can_Never_Be_Null (Etype (Rhs))
1885 Apply_Constraint_Check (Rhs, Etype (Lhs));
1888 -- Case of assignment to a bit packed array element
1890 if Nkind (Lhs) = N_Indexed_Component
1891 and then Is_Bit_Packed_Array (Etype (Prefix (Lhs)))
1893 Expand_Bit_Packed_Element_Set (N);
1896 -- Build-in-place function call case. Note that we're not yet doing
1897 -- build-in-place for user-written assignment statements (the assignment
1898 -- here came from an aggregate.)
1900 elsif Ada_Version >= Ada_2005
1901 and then Is_Build_In_Place_Function_Call (Rhs)
1903 Make_Build_In_Place_Call_In_Assignment (N, Rhs);
1905 elsif Is_Tagged_Type (Typ) and then Is_Value_Type (Etype (Lhs)) then
1907 -- Nothing to do for valuetypes
1908 -- ??? Set_Scope_Is_Transient (False);
1912 elsif Is_Tagged_Type (Typ)
1913 or else (Needs_Finalization (Typ) and then not Is_Array_Type (Typ))
1915 Tagged_Case : declare
1916 L : List_Id := No_List;
1917 Expand_Ctrl_Actions : constant Boolean := not No_Ctrl_Actions (N);
1920 -- In the controlled case, we ensure that function calls are
1921 -- evaluated before finalizing the target. In all cases, it makes
1922 -- the expansion easier if the side-effects are removed first.
1924 Remove_Side_Effects (Lhs);
1925 Remove_Side_Effects (Rhs);
1927 -- Avoid recursion in the mechanism
1931 -- If dispatching assignment, we need to dispatch to _assign
1933 if Is_Class_Wide_Type (Typ)
1935 -- If the type is tagged, we may as well use the predefined
1936 -- primitive assignment. This avoids inlining a lot of code
1937 -- and in the class-wide case, the assignment is replaced by
1938 -- dispatch call to _assign. Note that this cannot be done when
1939 -- discriminant checks are locally suppressed (as in extension
1940 -- aggregate expansions) because otherwise the discriminant
1941 -- check will be performed within the _assign call. It is also
1942 -- suppressed for assignments created by the expander that
1943 -- correspond to initializations, where we do want to copy the
1944 -- tag (No_Ctrl_Actions flag set True) by the expander and we
1945 -- do not need to mess with tags ever (Expand_Ctrl_Actions flag
1946 -- is set True in this case).
1948 or else (Is_Tagged_Type (Typ)
1949 and then not Is_Value_Type (Etype (Lhs))
1950 and then Chars (Current_Scope) /= Name_uAssign
1951 and then Expand_Ctrl_Actions
1952 and then not Discriminant_Checks_Suppressed (Empty))
1954 -- Fetch the primitive op _assign and proper type to call it.
1955 -- Because of possible conflicts between private and full view,
1956 -- fetch the proper type directly from the operation profile.
1959 Op : constant Entity_Id :=
1960 Find_Prim_Op (Typ, Name_uAssign);
1961 F_Typ : Entity_Id := Etype (First_Formal (Op));
1964 -- If the assignment is dispatching, make sure to use the
1967 if Is_Class_Wide_Type (Typ) then
1968 F_Typ := Class_Wide_Type (F_Typ);
1973 -- In case of assignment to a class-wide tagged type, before
1974 -- the assignment we generate run-time check to ensure that
1975 -- the tags of source and target match.
1977 if Is_Class_Wide_Type (Typ)
1978 and then Is_Tagged_Type (Typ)
1979 and then Is_Tagged_Type (Underlying_Type (Etype (Rhs)))
1982 Make_Raise_Constraint_Error (Loc,
1986 Make_Selected_Component (Loc,
1987 Prefix => Duplicate_Subexpr (Lhs),
1989 Make_Identifier (Loc, Name_uTag)),
1991 Make_Selected_Component (Loc,
1992 Prefix => Duplicate_Subexpr (Rhs),
1994 Make_Identifier (Loc, Name_uTag))),
1995 Reason => CE_Tag_Check_Failed));
1999 Left_N : Node_Id := Duplicate_Subexpr (Lhs);
2000 Right_N : Node_Id := Duplicate_Subexpr (Rhs);
2003 -- In order to dispatch the call to _assign the type of
2004 -- the actuals must match. Add conversion (if required).
2006 if Etype (Lhs) /= F_Typ then
2007 Left_N := Unchecked_Convert_To (F_Typ, Left_N);
2010 if Etype (Rhs) /= F_Typ then
2011 Right_N := Unchecked_Convert_To (F_Typ, Right_N);
2015 Make_Procedure_Call_Statement (Loc,
2016 Name => New_Reference_To (Op, Loc),
2017 Parameter_Associations => New_List (
2019 Node2 => Right_N)));
2024 L := Make_Tag_Ctrl_Assignment (N);
2026 -- We can't afford to have destructive Finalization Actions in
2027 -- the Self assignment case, so if the target and the source
2028 -- are not obviously different, code is generated to avoid the
2029 -- self assignment case:
2031 -- if lhs'address /= rhs'address then
2032 -- <code for controlled and/or tagged assignment>
2035 -- Skip this if Restriction (No_Finalization) is active
2037 if not Statically_Different (Lhs, Rhs)
2038 and then Expand_Ctrl_Actions
2039 and then not Restriction_Active (No_Finalization)
2042 Make_Implicit_If_Statement (N,
2046 Make_Attribute_Reference (Loc,
2047 Prefix => Duplicate_Subexpr (Lhs),
2048 Attribute_Name => Name_Address),
2051 Make_Attribute_Reference (Loc,
2052 Prefix => Duplicate_Subexpr (Rhs),
2053 Attribute_Name => Name_Address)),
2055 Then_Statements => L));
2058 -- We need to set up an exception handler for implementing
2059 -- 7.6.1(18). The remaining adjustments are tackled by the
2060 -- implementation of adjust for record_controllers (see
2063 -- This is skipped if we have no finalization
2065 if Expand_Ctrl_Actions
2066 and then not Restriction_Active (No_Finalization)
2069 Make_Block_Statement (Loc,
2070 Handled_Statement_Sequence =>
2071 Make_Handled_Sequence_Of_Statements (Loc,
2073 Exception_Handlers => New_List (
2074 Make_Handler_For_Ctrl_Operation (Loc)))));
2079 Make_Block_Statement (Loc,
2080 Handled_Statement_Sequence =>
2081 Make_Handled_Sequence_Of_Statements (Loc, Statements => L)));
2083 -- If no restrictions on aborts, protect the whole assignment
2084 -- for controlled objects as per 9.8(11).
2086 if Needs_Finalization (Typ)
2087 and then Expand_Ctrl_Actions
2088 and then Abort_Allowed
2091 Blk : constant Entity_Id :=
2093 (E_Block, Current_Scope, Sloc (N), 'B');
2096 Set_Scope (Blk, Current_Scope);
2097 Set_Etype (Blk, Standard_Void_Type);
2098 Set_Identifier (N, New_Occurrence_Of (Blk, Sloc (N)));
2100 Prepend_To (L, Build_Runtime_Call (Loc, RE_Abort_Defer));
2101 Set_At_End_Proc (Handled_Statement_Sequence (N),
2102 New_Occurrence_Of (RTE (RE_Abort_Undefer_Direct), Loc));
2103 Expand_At_End_Handler
2104 (Handled_Statement_Sequence (N), Blk);
2108 -- N has been rewritten to a block statement for which it is
2109 -- known by construction that no checks are necessary: analyze
2110 -- it with all checks suppressed.
2112 Analyze (N, Suppress => All_Checks);
2118 elsif Is_Array_Type (Typ) then
2120 Actual_Rhs : Node_Id := Rhs;
2123 while Nkind_In (Actual_Rhs, N_Type_Conversion,
2124 N_Qualified_Expression)
2126 Actual_Rhs := Expression (Actual_Rhs);
2129 Expand_Assign_Array (N, Actual_Rhs);
2135 elsif Is_Record_Type (Typ) then
2136 Expand_Assign_Record (N);
2139 -- Scalar types. This is where we perform the processing related to the
2140 -- requirements of (RM 13.9.1(9-11)) concerning the handling of invalid
2143 elsif Is_Scalar_Type (Typ) then
2145 -- Case where right side is known valid
2147 if Expr_Known_Valid (Rhs) then
2149 -- Here the right side is valid, so it is fine. The case to deal
2150 -- with is when the left side is a local variable reference whose
2151 -- value is not currently known to be valid. If this is the case,
2152 -- and the assignment appears in an unconditional context, then
2153 -- we can mark the left side as now being valid if one of these
2154 -- conditions holds:
2156 -- The expression of the right side has Do_Range_Check set so
2157 -- that we know a range check will be performed. Note that it
2158 -- can be the case that a range check is omitted because we
2159 -- make the assumption that we can assume validity for operands
2160 -- appearing in the right side in determining whether a range
2161 -- check is required
2163 -- The subtype of the right side matches the subtype of the
2164 -- left side. In this case, even though we have not checked
2165 -- the range of the right side, we know it is in range of its
2166 -- subtype if the expression is valid.
2168 if Is_Local_Variable_Reference (Lhs)
2169 and then not Is_Known_Valid (Entity (Lhs))
2170 and then In_Unconditional_Context (N)
2172 if Do_Range_Check (Rhs)
2173 or else Etype (Lhs) = Etype (Rhs)
2175 Set_Is_Known_Valid (Entity (Lhs), True);
2179 -- Case where right side may be invalid in the sense of the RM
2180 -- reference above. The RM does not require that we check for the
2181 -- validity on an assignment, but it does require that the assignment
2182 -- of an invalid value not cause erroneous behavior.
2184 -- The general approach in GNAT is to use the Is_Known_Valid flag
2185 -- to avoid the need for validity checking on assignments. However
2186 -- in some cases, we have to do validity checking in order to make
2187 -- sure that the setting of this flag is correct.
2190 -- Validate right side if we are validating copies
2192 if Validity_Checks_On
2193 and then Validity_Check_Copies
2195 -- Skip this if left hand side is an array or record component
2196 -- and elementary component validity checks are suppressed.
2198 if Nkind_In (Lhs, N_Selected_Component, N_Indexed_Component)
2199 and then not Validity_Check_Components
2206 -- We can propagate this to the left side where appropriate
2208 if Is_Local_Variable_Reference (Lhs)
2209 and then not Is_Known_Valid (Entity (Lhs))
2210 and then In_Unconditional_Context (N)
2212 Set_Is_Known_Valid (Entity (Lhs), True);
2215 -- Otherwise check to see what should be done
2217 -- If left side is a local variable, then we just set its flag to
2218 -- indicate that its value may no longer be valid, since we are
2219 -- copying a potentially invalid value.
2221 elsif Is_Local_Variable_Reference (Lhs) then
2222 Set_Is_Known_Valid (Entity (Lhs), False);
2224 -- Check for case of a nonlocal variable on the left side which
2225 -- is currently known to be valid. In this case, we simply ensure
2226 -- that the right side is valid. We only play the game of copying
2227 -- validity status for local variables, since we are doing this
2228 -- statically, not by tracing the full flow graph.
2230 elsif Is_Entity_Name (Lhs)
2231 and then Is_Known_Valid (Entity (Lhs))
2233 -- Note: If Validity_Checking mode is set to none, we ignore
2234 -- the Ensure_Valid call so don't worry about that case here.
2238 -- In all other cases, we can safely copy an invalid value without
2239 -- worrying about the status of the left side. Since it is not a
2240 -- variable reference it will not be considered
2241 -- as being known to be valid in any case.
2250 when RE_Not_Available =>
2252 end Expand_N_Assignment_Statement;
2254 ------------------------------
2255 -- Expand_N_Block_Statement --
2256 ------------------------------
2258 -- Encode entity names defined in block statement
2260 procedure Expand_N_Block_Statement (N : Node_Id) is
2262 Qualify_Entity_Names (N);
2263 end Expand_N_Block_Statement;
2265 -----------------------------
2266 -- Expand_N_Case_Statement --
2267 -----------------------------
2269 procedure Expand_N_Case_Statement (N : Node_Id) is
2270 Loc : constant Source_Ptr := Sloc (N);
2271 Expr : constant Node_Id := Expression (N);
2279 -- Check for the situation where we know at compile time which branch
2282 if Compile_Time_Known_Value (Expr) then
2283 Alt := Find_Static_Alternative (N);
2285 -- Move statements from this alternative after the case statement.
2286 -- They are already analyzed, so will be skipped by the analyzer.
2288 Insert_List_After (N, Statements (Alt));
2290 -- That leaves the case statement as a shell. So now we can kill all
2291 -- other alternatives in the case statement.
2293 Kill_Dead_Code (Expression (N));
2299 -- Loop through case alternatives, skipping pragmas, and skipping
2300 -- the one alternative that we select (and therefore retain).
2302 A := First (Alternatives (N));
2303 while Present (A) loop
2305 and then Nkind (A) = N_Case_Statement_Alternative
2307 Kill_Dead_Code (Statements (A), Warn_On_Deleted_Code);
2314 Rewrite (N, Make_Null_Statement (Loc));
2318 -- Here if the choice is not determined at compile time
2321 Last_Alt : constant Node_Id := Last (Alternatives (N));
2323 Others_Present : Boolean;
2324 Others_Node : Node_Id;
2326 Then_Stms : List_Id;
2327 Else_Stms : List_Id;
2330 if Nkind (First (Discrete_Choices (Last_Alt))) = N_Others_Choice then
2331 Others_Present := True;
2332 Others_Node := Last_Alt;
2334 Others_Present := False;
2337 -- First step is to worry about possible invalid argument. The RM
2338 -- requires (RM 5.4(13)) that if the result is invalid (e.g. it is
2339 -- outside the base range), then Constraint_Error must be raised.
2341 -- Case of validity check required (validity checks are on, the
2342 -- expression is not known to be valid, and the case statement
2343 -- comes from source -- no need to validity check internally
2344 -- generated case statements).
2346 if Validity_Check_Default then
2347 Ensure_Valid (Expr);
2350 -- If there is only a single alternative, just replace it with the
2351 -- sequence of statements since obviously that is what is going to
2352 -- be executed in all cases.
2354 Len := List_Length (Alternatives (N));
2357 -- We still need to evaluate the expression if it has any
2360 Remove_Side_Effects (Expression (N));
2362 Insert_List_After (N, Statements (First (Alternatives (N))));
2364 -- That leaves the case statement as a shell. The alternative that
2365 -- will be executed is reset to a null list. So now we can kill
2366 -- the entire case statement.
2368 Kill_Dead_Code (Expression (N));
2369 Rewrite (N, Make_Null_Statement (Loc));
2373 -- An optimization. If there are only two alternatives, and only
2374 -- a single choice, then rewrite the whole case statement as an
2375 -- if statement, since this can result in subsequent optimizations.
2376 -- This helps not only with case statements in the source of a
2377 -- simple form, but also with generated code (discriminant check
2378 -- functions in particular)
2381 Chlist := Discrete_Choices (First (Alternatives (N)));
2383 if List_Length (Chlist) = 1 then
2384 Choice := First (Chlist);
2386 Then_Stms := Statements (First (Alternatives (N)));
2387 Else_Stms := Statements (Last (Alternatives (N)));
2389 -- For TRUE, generate "expression", not expression = true
2391 if Nkind (Choice) = N_Identifier
2392 and then Entity (Choice) = Standard_True
2394 Cond := Expression (N);
2396 -- For FALSE, generate "expression" and switch then/else
2398 elsif Nkind (Choice) = N_Identifier
2399 and then Entity (Choice) = Standard_False
2401 Cond := Expression (N);
2402 Else_Stms := Statements (First (Alternatives (N)));
2403 Then_Stms := Statements (Last (Alternatives (N)));
2405 -- For a range, generate "expression in range"
2407 elsif Nkind (Choice) = N_Range
2408 or else (Nkind (Choice) = N_Attribute_Reference
2409 and then Attribute_Name (Choice) = Name_Range)
2410 or else (Is_Entity_Name (Choice)
2411 and then Is_Type (Entity (Choice)))
2412 or else Nkind (Choice) = N_Subtype_Indication
2416 Left_Opnd => Expression (N),
2417 Right_Opnd => Relocate_Node (Choice));
2419 -- For any other subexpression "expression = value"
2424 Left_Opnd => Expression (N),
2425 Right_Opnd => Relocate_Node (Choice));
2428 -- Now rewrite the case as an IF
2431 Make_If_Statement (Loc,
2433 Then_Statements => Then_Stms,
2434 Else_Statements => Else_Stms));
2440 -- If the last alternative is not an Others choice, replace it with
2441 -- an N_Others_Choice. Note that we do not bother to call Analyze on
2442 -- the modified case statement, since it's only effect would be to
2443 -- compute the contents of the Others_Discrete_Choices which is not
2444 -- needed by the back end anyway.
2446 -- The reason we do this is that the back end always needs some
2447 -- default for a switch, so if we have not supplied one in the
2448 -- processing above for validity checking, then we need to supply
2451 if not Others_Present then
2452 Others_Node := Make_Others_Choice (Sloc (Last_Alt));
2453 Set_Others_Discrete_Choices
2454 (Others_Node, Discrete_Choices (Last_Alt));
2455 Set_Discrete_Choices (Last_Alt, New_List (Others_Node));
2458 end Expand_N_Case_Statement;
2460 -----------------------------
2461 -- Expand_N_Exit_Statement --
2462 -----------------------------
2464 -- The only processing required is to deal with a possible C/Fortran
2465 -- boolean value used as the condition for the exit statement.
2467 procedure Expand_N_Exit_Statement (N : Node_Id) is
2469 Adjust_Condition (Condition (N));
2470 end Expand_N_Exit_Statement;
2472 -----------------------------
2473 -- Expand_N_Goto_Statement --
2474 -----------------------------
2476 -- Add poll before goto if polling active
2478 procedure Expand_N_Goto_Statement (N : Node_Id) is
2480 Generate_Poll_Call (N);
2481 end Expand_N_Goto_Statement;
2483 ---------------------------
2484 -- Expand_N_If_Statement --
2485 ---------------------------
2487 -- First we deal with the case of C and Fortran convention boolean values,
2488 -- with zero/non-zero semantics.
2490 -- Second, we deal with the obvious rewriting for the cases where the
2491 -- condition of the IF is known at compile time to be True or False.
2493 -- Third, we remove elsif parts which have non-empty Condition_Actions and
2494 -- rewrite as independent if statements. For example:
2505 -- <<condition actions of y>>
2511 -- This rewriting is needed if at least one elsif part has a non-empty
2512 -- Condition_Actions list. We also do the same processing if there is a
2513 -- constant condition in an elsif part (in conjunction with the first
2514 -- processing step mentioned above, for the recursive call made to deal
2515 -- with the created inner if, this deals with properly optimizing the
2516 -- cases of constant elsif conditions).
2518 procedure Expand_N_If_Statement (N : Node_Id) is
2519 Loc : constant Source_Ptr := Sloc (N);
2524 Warn_If_Deleted : constant Boolean :=
2525 Warn_On_Deleted_Code and then Comes_From_Source (N);
2526 -- Indicates whether we want warnings when we delete branches of the
2527 -- if statement based on constant condition analysis. We never want
2528 -- these warnings for expander generated code.
2531 Adjust_Condition (Condition (N));
2533 -- The following loop deals with constant conditions for the IF. We
2534 -- need a loop because as we eliminate False conditions, we grab the
2535 -- first elsif condition and use it as the primary condition.
2537 while Compile_Time_Known_Value (Condition (N)) loop
2539 -- If condition is True, we can simply rewrite the if statement now
2540 -- by replacing it by the series of then statements.
2542 if Is_True (Expr_Value (Condition (N))) then
2544 -- All the else parts can be killed
2546 Kill_Dead_Code (Elsif_Parts (N), Warn_If_Deleted);
2547 Kill_Dead_Code (Else_Statements (N), Warn_If_Deleted);
2549 Hed := Remove_Head (Then_Statements (N));
2550 Insert_List_After (N, Then_Statements (N));
2554 -- If condition is False, then we can delete the condition and
2555 -- the Then statements
2558 -- We do not delete the condition if constant condition warnings
2559 -- are enabled, since otherwise we end up deleting the desired
2560 -- warning. Of course the backend will get rid of this True/False
2561 -- test anyway, so nothing is lost here.
2563 if not Constant_Condition_Warnings then
2564 Kill_Dead_Code (Condition (N));
2567 Kill_Dead_Code (Then_Statements (N), Warn_If_Deleted);
2569 -- If there are no elsif statements, then we simply replace the
2570 -- entire if statement by the sequence of else statements.
2572 if No (Elsif_Parts (N)) then
2573 if No (Else_Statements (N))
2574 or else Is_Empty_List (Else_Statements (N))
2577 Make_Null_Statement (Sloc (N)));
2579 Hed := Remove_Head (Else_Statements (N));
2580 Insert_List_After (N, Else_Statements (N));
2586 -- If there are elsif statements, the first of them becomes the
2587 -- if/then section of the rebuilt if statement This is the case
2588 -- where we loop to reprocess this copied condition.
2591 Hed := Remove_Head (Elsif_Parts (N));
2592 Insert_Actions (N, Condition_Actions (Hed));
2593 Set_Condition (N, Condition (Hed));
2594 Set_Then_Statements (N, Then_Statements (Hed));
2596 -- Hed might have been captured as the condition determining
2597 -- the current value for an entity. Now it is detached from
2598 -- the tree, so a Current_Value pointer in the condition might
2599 -- need to be updated.
2601 Set_Current_Value_Condition (N);
2603 if Is_Empty_List (Elsif_Parts (N)) then
2604 Set_Elsif_Parts (N, No_List);
2610 -- Loop through elsif parts, dealing with constant conditions and
2611 -- possible expression actions that are present.
2613 if Present (Elsif_Parts (N)) then
2614 E := First (Elsif_Parts (N));
2615 while Present (E) loop
2616 Adjust_Condition (Condition (E));
2618 -- If there are condition actions, then rewrite the if statement
2619 -- as indicated above. We also do the same rewrite for a True or
2620 -- False condition. The further processing of this constant
2621 -- condition is then done by the recursive call to expand the
2622 -- newly created if statement
2624 if Present (Condition_Actions (E))
2625 or else Compile_Time_Known_Value (Condition (E))
2627 -- Note this is not an implicit if statement, since it is part
2628 -- of an explicit if statement in the source (or of an implicit
2629 -- if statement that has already been tested).
2632 Make_If_Statement (Sloc (E),
2633 Condition => Condition (E),
2634 Then_Statements => Then_Statements (E),
2635 Elsif_Parts => No_List,
2636 Else_Statements => Else_Statements (N));
2638 -- Elsif parts for new if come from remaining elsif's of parent
2640 while Present (Next (E)) loop
2641 if No (Elsif_Parts (New_If)) then
2642 Set_Elsif_Parts (New_If, New_List);
2645 Append (Remove_Next (E), Elsif_Parts (New_If));
2648 Set_Else_Statements (N, New_List (New_If));
2650 if Present (Condition_Actions (E)) then
2651 Insert_List_Before (New_If, Condition_Actions (E));
2656 if Is_Empty_List (Elsif_Parts (N)) then
2657 Set_Elsif_Parts (N, No_List);
2663 -- No special processing for that elsif part, move to next
2671 -- Some more optimizations applicable if we still have an IF statement
2673 if Nkind (N) /= N_If_Statement then
2677 -- Another optimization, special cases that can be simplified
2679 -- if expression then
2685 -- can be changed to:
2687 -- return expression;
2691 -- if expression then
2697 -- can be changed to:
2699 -- return not (expression);
2701 -- Only do these optimizations if we are at least at -O1 level and
2702 -- do not do them if control flow optimizations are suppressed.
2704 if Optimization_Level > 0
2705 and then not Opt.Suppress_Control_Flow_Optimizations
2707 if Nkind (N) = N_If_Statement
2708 and then No (Elsif_Parts (N))
2709 and then Present (Else_Statements (N))
2710 and then List_Length (Then_Statements (N)) = 1
2711 and then List_Length (Else_Statements (N)) = 1
2714 Then_Stm : constant Node_Id := First (Then_Statements (N));
2715 Else_Stm : constant Node_Id := First (Else_Statements (N));
2718 if Nkind (Then_Stm) = N_Simple_Return_Statement
2720 Nkind (Else_Stm) = N_Simple_Return_Statement
2723 Then_Expr : constant Node_Id := Expression (Then_Stm);
2724 Else_Expr : constant Node_Id := Expression (Else_Stm);
2727 if Nkind (Then_Expr) = N_Identifier
2729 Nkind (Else_Expr) = N_Identifier
2731 if Entity (Then_Expr) = Standard_True
2732 and then Entity (Else_Expr) = Standard_False
2735 Make_Simple_Return_Statement (Loc,
2736 Expression => Relocate_Node (Condition (N))));
2740 elsif Entity (Then_Expr) = Standard_False
2741 and then Entity (Else_Expr) = Standard_True
2744 Make_Simple_Return_Statement (Loc,
2748 Relocate_Node (Condition (N)))));
2758 end Expand_N_If_Statement;
2760 --------------------------
2761 -- Expand_Iterator_Loop --
2762 --------------------------
2764 procedure Expand_Iterator_Loop (N : Node_Id) is
2765 Loc : constant Source_Ptr := Sloc (N);
2766 Isc : constant Node_Id := Iteration_Scheme (N);
2767 I_Spec : constant Node_Id := Iterator_Specification (Isc);
2768 Id : constant Entity_Id := Defining_Identifier (I_Spec);
2769 Container : constant Entity_Id := Entity (Name (I_Spec));
2770 Typ : constant Entity_Id := Etype (Container);
2777 if Is_Array_Type (Typ) then
2778 if Of_Present (I_Spec) then
2779 Cursor := Make_Temporary (Loc, 'C');
2781 -- for Elem of Arr loop ...
2784 Decl : constant Node_Id :=
2785 Make_Object_Renaming_Declaration (Loc,
2786 Defining_Identifier => Id,
2788 New_Occurrence_Of (Component_Type (Typ), Loc),
2790 Make_Indexed_Component (Loc,
2792 New_Occurrence_Of (Container, Loc),
2794 New_List (New_Occurrence_Of (Cursor, Loc))));
2796 Stats := Statements (N);
2797 Prepend (Decl, Stats);
2800 Make_Loop_Statement (Loc,
2802 Make_Iteration_Scheme (Loc,
2803 Loop_Parameter_Specification =>
2804 Make_Loop_Parameter_Specification (Loc,
2805 Defining_Identifier => Cursor,
2806 Discrete_Subtype_Definition =>
2807 Make_Attribute_Reference (Loc,
2809 New_Occurrence_Of (Container, Loc),
2810 Attribute_Name => Name_Range),
2811 Reverse_Present => Reverse_Present (I_Spec))),
2812 Statements => Stats,
2813 End_Label => Empty);
2817 -- for Index in Array loop ...
2819 -- The cursor (index into the array) is the source Id
2823 Make_Loop_Statement (Loc,
2825 Make_Iteration_Scheme (Loc,
2826 Loop_Parameter_Specification =>
2827 Make_Loop_Parameter_Specification (Loc,
2828 Defining_Identifier => Cursor,
2829 Discrete_Subtype_Definition =>
2830 Make_Attribute_Reference (Loc,
2832 New_Occurrence_Of (Container, Loc),
2833 Attribute_Name => Name_Range),
2834 Reverse_Present => Reverse_Present (I_Spec))),
2835 Statements => Statements (N),
2836 End_Label => Empty);
2839 -- Iterators over containers
2842 -- In both cases these require a cursor of the proper type
2844 -- Cursor : P.Cursor_Type := Container.First;
2845 -- while Cursor /= P.No_Element loop
2847 -- Obj : P.Element_Type renames Element (Cursor);
2848 -- -- For the "of" form, the element name renames the element
2849 -- -- designated by the cursor.
2855 -- with the obvious replacements if "reverse" is specified.
2858 Element_Type : constant Entity_Id := Etype (Id);
2859 Pack : constant Entity_Id := Scope (Etype (Container));
2860 Name_Init : Name_Id;
2861 Name_Step : Name_Id;
2863 Cursor_Decl : Node_Id;
2864 Renaming_Decl : Node_Id;
2867 Stats := Statements (N);
2869 if Of_Present (I_Spec) then
2870 Cursor := Make_Temporary (Loc, 'C');
2875 if Reverse_Present (I_Spec) then
2877 -- Must verify that the container has a reverse iterator ???
2879 Name_Init := Name_Last;
2880 Name_Step := Name_Previous;
2883 Name_Init := Name_First;
2884 Name_Step := Name_Next;
2887 -- C : Cursor_Type := Container.First;
2890 Make_Object_Declaration (Loc,
2891 Defining_Identifier => Cursor,
2892 Object_Definition =>
2893 Make_Selected_Component (Loc,
2894 Prefix => New_Occurrence_Of (Pack, Loc),
2895 Selector_Name => Make_Identifier (Loc, Name_Cursor)),
2897 Make_Selected_Component (Loc,
2898 Prefix => New_Occurrence_Of (Container, Loc),
2899 Selector_Name => Make_Identifier (Loc, Name_Init)));
2901 Insert_Action (N, Cursor_Decl);
2903 -- while C /= No_Element loop
2905 Cond := Make_Op_Ne (Loc,
2906 Left_Opnd => New_Occurrence_Of (Cursor, Loc),
2907 Right_Opnd => Make_Selected_Component (Loc,
2908 Prefix => New_Occurrence_Of (Pack, Loc),
2910 Make_Identifier (Loc, Name_No_Element)));
2912 if Of_Present (I_Spec) then
2914 -- Id : Element_Type renames Pack.Element (Cursor);
2917 Make_Object_Renaming_Declaration (Loc,
2918 Defining_Identifier => Id,
2920 New_Occurrence_Of (Element_Type, Loc),
2922 Make_Indexed_Component (Loc,
2924 Make_Selected_Component (Loc,
2925 Prefix => New_Occurrence_Of (Pack, Loc),
2927 Make_Identifier (Loc, Chars => Name_Element)),
2929 New_List (New_Occurrence_Of (Cursor, Loc))));
2931 Prepend (Renaming_Decl, Stats);
2934 -- For both iterator forms, add call to step operation (Next or
2935 -- Previous) to advance cursor.
2938 Make_Procedure_Call_Statement (Loc,
2940 Make_Selected_Component (Loc,
2941 Prefix => New_Occurrence_Of (Pack, Loc),
2942 Selector_Name => Make_Identifier (Loc, Name_Step)),
2943 Parameter_Associations =>
2944 New_List (New_Occurrence_Of (Cursor, Loc))));
2946 New_Loop := Make_Loop_Statement (Loc,
2948 Make_Iteration_Scheme (Loc, Condition => Cond),
2949 Statements => Stats,
2950 End_Label => Empty);
2954 -- Set_Analyzed (I_Spec);
2955 -- Why is this commented out???
2957 Rewrite (N, New_Loop);
2959 end Expand_Iterator_Loop;
2961 -----------------------------
2962 -- Expand_N_Loop_Statement --
2963 -----------------------------
2965 -- 1. Remove null loop entirely
2966 -- 2. Deal with while condition for C/Fortran boolean
2967 -- 3. Deal with loops with a non-standard enumeration type range
2968 -- 4. Deal with while loops where Condition_Actions is set
2969 -- 5. Deal with loops over predicated subtypes
2970 -- 6. Deal with loops with iterators over arrays and containers
2971 -- 7. Insert polling call if required
2973 procedure Expand_N_Loop_Statement (N : Node_Id) is
2974 Loc : constant Source_Ptr := Sloc (N);
2975 Isc : constant Node_Id := Iteration_Scheme (N);
2980 if Is_Null_Loop (N) then
2981 Rewrite (N, Make_Null_Statement (Loc));
2985 -- Deal with condition for C/Fortran Boolean
2987 if Present (Isc) then
2988 Adjust_Condition (Condition (Isc));
2991 -- Generate polling call
2993 if Is_Non_Empty_List (Statements (N)) then
2994 Generate_Poll_Call (First (Statements (N)));
2997 -- Nothing more to do for plain loop with no iteration scheme
3002 -- Case of for loop (Loop_Parameter_Specification present)
3004 -- Note: we do not have to worry about validity checking of the for loop
3005 -- range bounds here, since they were frozen with constant declarations
3006 -- and it is during that process that the validity checking is done.
3008 elsif Present (Loop_Parameter_Specification (Isc)) then
3010 LPS : constant Node_Id := Loop_Parameter_Specification (Isc);
3011 Loop_Id : constant Entity_Id := Defining_Identifier (LPS);
3012 Ltype : constant Entity_Id := Etype (Loop_Id);
3013 Btype : constant Entity_Id := Base_Type (Ltype);
3018 -- Deal with loop over predicates
3020 if Is_Discrete_Type (Ltype)
3021 and then Present (Predicate_Function (Ltype))
3023 Expand_Predicated_Loop (N);
3025 -- Handle the case where we have a for loop with the range type
3026 -- being an enumeration type with non-standard representation.
3027 -- In this case we expand:
3029 -- for x in [reverse] a .. b loop
3035 -- for xP in [reverse] integer
3036 -- range etype'Pos (a) .. etype'Pos (b)
3039 -- x : constant etype := Pos_To_Rep (xP);
3045 elsif Is_Enumeration_Type (Btype)
3046 and then Present (Enum_Pos_To_Rep (Btype))
3049 Make_Defining_Identifier (Loc,
3050 Chars => New_External_Name (Chars (Loop_Id), 'P'));
3052 -- If the type has a contiguous representation, successive
3053 -- values can be generated as offsets from the first literal.
3055 if Has_Contiguous_Rep (Btype) then
3057 Unchecked_Convert_To (Btype,
3060 Make_Integer_Literal (Loc,
3061 Enumeration_Rep (First_Literal (Btype))),
3062 Right_Opnd => New_Reference_To (New_Id, Loc)));
3064 -- Use the constructed array Enum_Pos_To_Rep
3067 Make_Indexed_Component (Loc,
3069 New_Reference_To (Enum_Pos_To_Rep (Btype), Loc),
3071 New_List (New_Reference_To (New_Id, Loc)));
3075 Make_Loop_Statement (Loc,
3076 Identifier => Identifier (N),
3079 Make_Iteration_Scheme (Loc,
3080 Loop_Parameter_Specification =>
3081 Make_Loop_Parameter_Specification (Loc,
3082 Defining_Identifier => New_Id,
3083 Reverse_Present => Reverse_Present (LPS),
3085 Discrete_Subtype_Definition =>
3086 Make_Subtype_Indication (Loc,
3089 New_Reference_To (Standard_Natural, Loc),
3092 Make_Range_Constraint (Loc,
3097 Make_Attribute_Reference (Loc,
3099 New_Reference_To (Btype, Loc),
3101 Attribute_Name => Name_Pos,
3103 Expressions => New_List (
3105 (Type_Low_Bound (Ltype)))),
3108 Make_Attribute_Reference (Loc,
3110 New_Reference_To (Btype, Loc),
3112 Attribute_Name => Name_Pos,
3114 Expressions => New_List (
3119 Statements => New_List (
3120 Make_Block_Statement (Loc,
3121 Declarations => New_List (
3122 Make_Object_Declaration (Loc,
3123 Defining_Identifier => Loop_Id,
3124 Constant_Present => True,
3125 Object_Definition =>
3126 New_Reference_To (Ltype, Loc),
3127 Expression => Expr)),
3129 Handled_Statement_Sequence =>
3130 Make_Handled_Sequence_Of_Statements (Loc,
3131 Statements => Statements (N)))),
3133 End_Label => End_Label (N)));
3136 -- Nothing to do with other cases of for loops
3143 -- Second case, if we have a while loop with Condition_Actions set, then
3144 -- we change it into a plain loop:
3153 -- <<condition actions>>
3159 and then Present (Condition_Actions (Isc))
3166 Make_Exit_Statement (Sloc (Condition (Isc)),
3168 Make_Op_Not (Sloc (Condition (Isc)),
3169 Right_Opnd => Condition (Isc)));
3171 Prepend (ES, Statements (N));
3172 Insert_List_Before (ES, Condition_Actions (Isc));
3174 -- This is not an implicit loop, since it is generated in response
3175 -- to the loop statement being processed. If this is itself
3176 -- implicit, the restriction has already been checked. If not,
3177 -- it is an explicit loop.
3180 Make_Loop_Statement (Sloc (N),
3181 Identifier => Identifier (N),
3182 Statements => Statements (N),
3183 End_Label => End_Label (N)));
3188 -- Here to deal with iterator case
3191 and then Present (Iterator_Specification (Isc))
3193 Expand_Iterator_Loop (N);
3195 end Expand_N_Loop_Statement;
3197 ----------------------------
3198 -- Expand_Predicated_Loop --
3199 ----------------------------
3201 -- Note: the expander can handle generation of loops over predicated
3202 -- subtypes for both the dynamic and static cases. Depending on what
3203 -- we decide is allowed in Ada 2012 mode and/or extentions allowed
3204 -- mode, the semantic analyzer may disallow one or both forms.
3206 procedure Expand_Predicated_Loop (N : Node_Id) is
3207 Loc : constant Source_Ptr := Sloc (N);
3208 Isc : constant Node_Id := Iteration_Scheme (N);
3209 LPS : constant Node_Id := Loop_Parameter_Specification (Isc);
3210 Loop_Id : constant Entity_Id := Defining_Identifier (LPS);
3211 Ltype : constant Entity_Id := Etype (Loop_Id);
3212 Stat : constant List_Id := Static_Predicate (Ltype);
3213 Stmts : constant List_Id := Statements (N);
3216 -- Case of iteration over non-static predicate, should not be possible
3217 -- since this is not allowed by the semantics and should have been
3218 -- caught during analysis of the loop statement.
3221 raise Program_Error;
3223 -- If the predicate list is empty, that corresponds to a predicate of
3224 -- False, in which case the loop won't run at all, and we rewrite the
3225 -- entire loop as a null statement.
3227 elsif Is_Empty_List (Stat) then
3228 Rewrite (N, Make_Null_Statement (Loc));
3231 -- For expansion over a static predicate we generate the following
3234 -- J : Ltype := min-val;
3239 -- when endpoint => J := startpoint;
3240 -- when endpoint => J := startpoint;
3242 -- when max-val => exit;
3243 -- when others => J := Lval'Succ (J);
3248 -- To make this a little clearer, let's take a specific example:
3250 -- type Int is range 1 .. 10;
3251 -- subtype L is Int with
3252 -- predicate => L in 3 | 10 | 5 .. 7;
3254 -- for L in StaticP loop
3255 -- Put_Line ("static:" & J'Img);
3258 -- In this case, the loop is transformed into
3265 -- when 3 => J := 5;
3266 -- when 7 => J := 10;
3268 -- when others => J := L'Succ (J);
3274 Static_Predicate : declare
3281 function Lo_Val (N : Node_Id) return Node_Id;
3282 -- Given static expression or static range, returns an identifier
3283 -- whose value is the low bound of the expression value or range.
3285 function Hi_Val (N : Node_Id) return Node_Id;
3286 -- Given static expression or static range, returns an identifier
3287 -- whose value is the high bound of the expression value or range.
3293 function Hi_Val (N : Node_Id) return Node_Id is
3295 if Is_Static_Expression (N) then
3296 return New_Copy (N);
3298 pragma Assert (Nkind (N) = N_Range);
3299 return New_Copy (High_Bound (N));
3307 function Lo_Val (N : Node_Id) return Node_Id is
3309 if Is_Static_Expression (N) then
3310 return New_Copy (N);
3312 pragma Assert (Nkind (N) = N_Range);
3313 return New_Copy (Low_Bound (N));
3317 -- Start of processing for Static_Predicate
3320 -- Convert loop identifier to normal variable and reanalyze it so
3321 -- that this conversion works. We have to use the same defining
3322 -- identifier, since there may be references in the loop body.
3324 Set_Analyzed (Loop_Id, False);
3325 Set_Ekind (Loop_Id, E_Variable);
3327 -- Loop to create branches of case statement
3331 while Present (P) loop
3332 if No (Next (P)) then
3333 S := Make_Exit_Statement (Loc);
3336 Make_Assignment_Statement (Loc,
3337 Name => New_Occurrence_Of (Loop_Id, Loc),
3338 Expression => Lo_Val (Next (P)));
3339 Set_Suppress_Assignment_Checks (S);
3343 Make_Case_Statement_Alternative (Loc,
3344 Statements => New_List (S),
3345 Discrete_Choices => New_List (Hi_Val (P))));
3350 -- Add others choice
3353 Make_Assignment_Statement (Loc,
3354 Name => New_Occurrence_Of (Loop_Id, Loc),
3356 Make_Attribute_Reference (Loc,
3357 Prefix => New_Occurrence_Of (Ltype, Loc),
3358 Attribute_Name => Name_Succ,
3359 Expressions => New_List (
3360 New_Occurrence_Of (Loop_Id, Loc))));
3361 Set_Suppress_Assignment_Checks (S);
3364 Make_Case_Statement_Alternative (Loc,
3365 Discrete_Choices => New_List (Make_Others_Choice (Loc)),
3366 Statements => New_List (S)));
3368 -- Construct case statement and append to body statements
3371 Make_Case_Statement (Loc,
3372 Expression => New_Occurrence_Of (Loop_Id, Loc),
3373 Alternatives => Alts);
3374 Append_To (Stmts, Cstm);
3379 Make_Object_Declaration (Loc,
3380 Defining_Identifier => Loop_Id,
3381 Object_Definition => New_Occurrence_Of (Ltype, Loc),
3382 Expression => Lo_Val (First (Stat)));
3383 Set_Suppress_Assignment_Checks (D);
3386 Make_Block_Statement (Loc,
3387 Declarations => New_List (D),
3388 Handled_Statement_Sequence =>
3389 Make_Handled_Sequence_Of_Statements (Loc,
3390 Statements => New_List (
3391 Make_Loop_Statement (Loc,
3392 Statements => Stmts,
3393 End_Label => Empty)))));
3396 end Static_Predicate;
3398 end Expand_Predicated_Loop;
3400 ------------------------------
3401 -- Make_Tag_Ctrl_Assignment --
3402 ------------------------------
3404 function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id is
3405 Loc : constant Source_Ptr := Sloc (N);
3406 L : constant Node_Id := Name (N);
3407 T : constant Entity_Id := Underlying_Type (Etype (L));
3409 Ctrl_Act : constant Boolean := Needs_Finalization (T)
3410 and then not No_Ctrl_Actions (N);
3412 Component_Assign : constant Boolean :=
3413 Is_Fully_Repped_Tagged_Type (T);
3415 Save_Tag : constant Boolean := Is_Tagged_Type (T)
3416 and then not Component_Assign
3417 and then not No_Ctrl_Actions (N)
3418 and then Tagged_Type_Expansion;
3419 -- Tags are not saved and restored when VM_Target because VM tags are
3420 -- represented implicitly in objects.
3423 Tag_Tmp : Entity_Id;
3425 Prev_Tmp : Entity_Id;
3426 Next_Tmp : Entity_Id;
3432 -- Finalize the target of the assignment when controlled
3434 -- We have two exceptions here:
3436 -- 1. If we are in an init proc since it is an initialization more
3437 -- than an assignment.
3439 -- 2. If the left-hand side is a temporary that was not initialized
3440 -- (or the parent part of a temporary since it is the case in
3441 -- extension aggregates). Such a temporary does not come from
3442 -- source. We must examine the original node for the prefix, because
3443 -- it may be a component of an entry formal, in which case it has
3444 -- been rewritten and does not appear to come from source either.
3446 -- Case of init proc
3448 if not Ctrl_Act then
3451 -- The left hand side is an uninitialized temporary object
3453 elsif Nkind (L) = N_Type_Conversion
3454 and then Is_Entity_Name (Expression (L))
3455 and then Nkind (Parent (Entity (Expression (L)))) =
3456 N_Object_Declaration
3457 and then No_Initialization (Parent (Entity (Expression (L))))
3462 Append_List_To (Res,
3464 (Ref => Duplicate_Subexpr_No_Checks (L),
3466 With_Detach => New_Reference_To (Standard_False, Loc)));
3469 -- Save the Tag in a local variable Tag_Tmp
3472 Tag_Tmp := Make_Temporary (Loc, 'A');
3475 Make_Object_Declaration (Loc,
3476 Defining_Identifier => Tag_Tmp,
3477 Object_Definition => New_Reference_To (RTE (RE_Tag), Loc),
3479 Make_Selected_Component (Loc,
3480 Prefix => Duplicate_Subexpr_No_Checks (L),
3481 Selector_Name => New_Reference_To (First_Tag_Component (T),
3484 -- Otherwise Tag_Tmp not used
3491 if VM_Target /= No_VM then
3493 -- Cannot assign part of the object in a VM context, so instead
3494 -- fallback to the previous mechanism, even though it is not
3495 -- completely correct ???
3497 -- Save the Finalization Pointers in local variables Prev_Tmp and
3498 -- Next_Tmp. For objects with Has_Controlled_Component set, these
3499 -- pointers are in the Record_Controller
3501 Ctrl_Ref := Duplicate_Subexpr (L);
3503 if Has_Controlled_Component (T) then
3505 Make_Selected_Component (Loc,
3508 New_Reference_To (Controller_Component (T), Loc));
3511 Prev_Tmp := Make_Temporary (Loc, 'B');
3514 Make_Object_Declaration (Loc,
3515 Defining_Identifier => Prev_Tmp,
3517 Object_Definition =>
3518 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc),
3521 Make_Selected_Component (Loc,
3523 Unchecked_Convert_To (RTE (RE_Finalizable), Ctrl_Ref),
3524 Selector_Name => Make_Identifier (Loc, Name_Prev))));
3526 Next_Tmp := Make_Temporary (Loc, 'C');
3529 Make_Object_Declaration (Loc,
3530 Defining_Identifier => Next_Tmp,
3532 Object_Definition =>
3533 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc),
3536 Make_Selected_Component (Loc,
3538 Unchecked_Convert_To (RTE (RE_Finalizable),
3539 New_Copy_Tree (Ctrl_Ref)),
3540 Selector_Name => Make_Identifier (Loc, Name_Next))));
3542 -- Do the Assignment
3544 Append_To (Res, Relocate_Node (N));
3547 -- Regular (non VM) processing for controlled types and types with
3548 -- controlled components
3550 -- Variables of such types contain pointers used to chain them in
3551 -- finalization lists, in addition to user data. These pointers
3552 -- are specific to each object of the type, not to the value being
3555 -- Thus they need to be left intact during the assignment. We
3556 -- achieve this by constructing a Storage_Array subtype, and by
3557 -- overlaying objects of this type on the source and target of the
3558 -- assignment. The assignment is then rewritten to assignments of
3559 -- slices of these arrays, copying the user data, and leaving the
3560 -- pointers untouched.
3562 Controlled_Actions : declare
3564 -- A reference to the Prev component of the record controller
3566 First_After_Root : Node_Id := Empty;
3567 -- Index of first byte to be copied (used to skip
3568 -- Root_Controlled in controlled objects).
3570 Last_Before_Hole : Node_Id := Empty;
3571 -- Index of last byte to be copied before outermost record
3574 Hole_Length : Node_Id := Empty;
3575 -- Length of record controller data (Prev and Next pointers)
3577 First_After_Hole : Node_Id := Empty;
3578 -- Index of first byte to be copied after outermost record
3581 Expr, Source_Size : Node_Id;
3582 Source_Actual_Subtype : Entity_Id;
3583 -- Used for computation of the size of the data to be copied
3585 Range_Type : Entity_Id;
3586 Opaque_Type : Entity_Id;
3588 function Build_Slice
3591 Hi : Node_Id) return Node_Id;
3592 -- Build and return a slice of an array of type S overlaid on
3593 -- object Rec, with bounds specified by Lo and Hi. If either
3594 -- bound is empty, a default of S'First (respectively S'Last)
3601 function Build_Slice
3604 Hi : Node_Id) return Node_Id
3609 Opaque : constant Node_Id :=
3610 Unchecked_Convert_To (Opaque_Type,
3611 Make_Attribute_Reference (Loc,
3613 Attribute_Name => Name_Address));
3614 -- Access value designating an opaque storage array of type
3615 -- S overlaid on record Rec.
3618 -- Compute slice bounds using S'First (1) and S'Last as
3619 -- default values when not specified by the caller.
3622 Lo_Bound := Make_Integer_Literal (Loc, 1);
3628 Hi_Bound := Make_Attribute_Reference (Loc,
3629 Prefix => New_Occurrence_Of (Range_Type, Loc),
3630 Attribute_Name => Name_Last);
3635 return Make_Slice (Loc,
3638 Discrete_Range => Make_Range (Loc,
3639 Lo_Bound, Hi_Bound));
3642 -- Start of processing for Controlled_Actions
3645 -- Create a constrained subtype of Storage_Array whose size
3646 -- corresponds to the value being assigned.
3648 -- subtype G is Storage_Offset range
3649 -- 1 .. (Expr'Size + Storage_Unit - 1) / Storage_Unit
3651 Expr := Duplicate_Subexpr_No_Checks (Expression (N));
3653 if Nkind (Expr) = N_Qualified_Expression then
3654 Expr := Expression (Expr);
3657 Source_Actual_Subtype := Etype (Expr);
3659 if Has_Discriminants (Source_Actual_Subtype)
3660 and then not Is_Constrained (Source_Actual_Subtype)
3663 Build_Actual_Subtype (Source_Actual_Subtype, Expr));
3664 Source_Actual_Subtype := Defining_Identifier (Last (Res));
3670 Make_Attribute_Reference (Loc,
3672 New_Occurrence_Of (Source_Actual_Subtype, Loc),
3673 Attribute_Name => Name_Size),
3675 Make_Integer_Literal (Loc,
3676 Intval => System_Storage_Unit - 1));
3679 Make_Op_Divide (Loc,
3680 Left_Opnd => Source_Size,
3682 Make_Integer_Literal (Loc,
3683 Intval => System_Storage_Unit));
3685 Range_Type := Make_Temporary (Loc, 'G');
3688 Make_Subtype_Declaration (Loc,
3689 Defining_Identifier => Range_Type,
3690 Subtype_Indication =>
3691 Make_Subtype_Indication (Loc,
3693 New_Reference_To (RTE (RE_Storage_Offset), Loc),
3694 Constraint => Make_Range_Constraint (Loc,
3697 Low_Bound => Make_Integer_Literal (Loc, 1),
3698 High_Bound => Source_Size)))));
3700 -- subtype S is Storage_Array (G)
3703 Make_Subtype_Declaration (Loc,
3704 Defining_Identifier => Make_Temporary (Loc, 'S'),
3705 Subtype_Indication =>
3706 Make_Subtype_Indication (Loc,
3708 New_Reference_To (RTE (RE_Storage_Array), Loc),
3710 Make_Index_Or_Discriminant_Constraint (Loc,
3712 New_List (New_Reference_To (Range_Type, Loc))))));
3714 -- type A is access S
3716 Opaque_Type := Make_Temporary (Loc, 'A');
3719 Make_Full_Type_Declaration (Loc,
3720 Defining_Identifier => Opaque_Type,
3722 Make_Access_To_Object_Definition (Loc,
3723 Subtype_Indication =>
3725 Defining_Identifier (Last (Res)), Loc))));
3727 -- Generate appropriate slice assignments
3729 First_After_Root := Make_Integer_Literal (Loc, 1);
3731 -- For controlled object, skip Root_Controlled part
3733 if Is_Controlled (T) then
3737 Make_Op_Divide (Loc,
3738 Make_Attribute_Reference (Loc,
3740 New_Occurrence_Of (RTE (RE_Root_Controlled), Loc),
3741 Attribute_Name => Name_Size),
3742 Make_Integer_Literal (Loc, System_Storage_Unit)));
3745 -- For the case of a record with controlled components, skip
3746 -- record controller Prev/Next components. These components
3747 -- constitute a 'hole' in the middle of the data to be copied.
3749 if Has_Controlled_Component (T) then
3751 Make_Selected_Component (Loc,
3753 Make_Selected_Component (Loc,
3754 Prefix => Duplicate_Subexpr_No_Checks (L),
3756 New_Reference_To (Controller_Component (T), Loc)),
3757 Selector_Name => Make_Identifier (Loc, Name_Prev));
3759 -- Last index before hole: determined by position of the
3760 -- _Controller.Prev component.
3762 Last_Before_Hole := Make_Temporary (Loc, 'L');
3765 Make_Object_Declaration (Loc,
3766 Defining_Identifier => Last_Before_Hole,
3767 Object_Definition => New_Occurrence_Of (
3768 RTE (RE_Storage_Offset), Loc),
3769 Constant_Present => True,
3772 Make_Attribute_Reference (Loc,
3774 Attribute_Name => Name_Position),
3775 Make_Attribute_Reference (Loc,
3776 Prefix => New_Copy_Tree (Prefix (Prev_Ref)),
3777 Attribute_Name => Name_Position))));
3779 -- Hole length: size of the Prev and Next components
3782 Make_Op_Multiply (Loc,
3783 Left_Opnd => Make_Integer_Literal (Loc, Uint_2),
3785 Make_Op_Divide (Loc,
3787 Make_Attribute_Reference (Loc,
3788 Prefix => New_Copy_Tree (Prev_Ref),
3789 Attribute_Name => Name_Size),
3791 Make_Integer_Literal (Loc,
3792 Intval => System_Storage_Unit)));
3794 -- First index after hole
3796 First_After_Hole := Make_Temporary (Loc, 'F');
3799 Make_Object_Declaration (Loc,
3800 Defining_Identifier => First_After_Hole,
3801 Object_Definition => New_Occurrence_Of (
3802 RTE (RE_Storage_Offset), Loc),
3803 Constant_Present => True,
3809 New_Occurrence_Of (Last_Before_Hole, Loc),
3810 Right_Opnd => Hole_Length),
3811 Right_Opnd => Make_Integer_Literal (Loc, 1))));
3814 New_Occurrence_Of (Last_Before_Hole, Loc);
3816 New_Occurrence_Of (First_After_Hole, Loc);
3819 -- Assign the first slice (possibly skipping Root_Controlled,
3820 -- up to the beginning of the record controller if present,
3821 -- up to the end of the object if not).
3823 Append_To (Res, Make_Assignment_Statement (Loc,
3824 Name => Build_Slice (
3825 Rec => Duplicate_Subexpr_No_Checks (L),
3826 Lo => First_After_Root,
3827 Hi => Last_Before_Hole),
3829 Expression => Build_Slice (
3830 Rec => Expression (N),
3831 Lo => First_After_Root,
3832 Hi => New_Copy_Tree (Last_Before_Hole))));
3834 if Present (First_After_Hole) then
3836 -- If a record controller is present, copy the second slice,
3837 -- from right after the _Controller.Next component up to the
3838 -- end of the object.
3840 Append_To (Res, Make_Assignment_Statement (Loc,
3841 Name => Build_Slice (
3842 Rec => Duplicate_Subexpr_No_Checks (L),
3843 Lo => First_After_Hole,
3845 Expression => Build_Slice (
3846 Rec => Duplicate_Subexpr_No_Checks (Expression (N)),
3847 Lo => New_Copy_Tree (First_After_Hole),
3850 end Controlled_Actions;
3853 -- Not controlled case
3857 Asn : constant Node_Id := Relocate_Node (N);
3860 -- If this is the case of a tagged type with a full rep clause,
3861 -- we must expand it into component assignments, so we mark the
3862 -- node as unanalyzed, to get it reanalyzed, but flag it has
3863 -- requiring component-wise assignment so we don't get infinite
3866 if Component_Assign then
3867 Set_Analyzed (Asn, False);
3868 Set_Componentwise_Assignment (Asn, True);
3871 Append_To (Res, Asn);
3879 Make_Assignment_Statement (Loc,
3881 Make_Selected_Component (Loc,
3882 Prefix => Duplicate_Subexpr_No_Checks (L),
3883 Selector_Name => New_Reference_To (First_Tag_Component (T),
3885 Expression => New_Reference_To (Tag_Tmp, Loc)));
3889 if VM_Target /= No_VM then
3890 -- Restore the finalization pointers
3893 Make_Assignment_Statement (Loc,
3895 Make_Selected_Component (Loc,
3897 Unchecked_Convert_To (RTE (RE_Finalizable),
3898 New_Copy_Tree (Ctrl_Ref)),
3899 Selector_Name => Make_Identifier (Loc, Name_Prev)),
3900 Expression => New_Reference_To (Prev_Tmp, Loc)));
3903 Make_Assignment_Statement (Loc,
3905 Make_Selected_Component (Loc,
3907 Unchecked_Convert_To (RTE (RE_Finalizable),
3908 New_Copy_Tree (Ctrl_Ref)),
3909 Selector_Name => Make_Identifier (Loc, Name_Next)),
3910 Expression => New_Reference_To (Next_Tmp, Loc)));
3913 -- Adjust the target after the assignment when controlled (not in the
3914 -- init proc since it is an initialization more than an assignment).
3916 Append_List_To (Res,
3918 Ref => Duplicate_Subexpr_Move_Checks (L),
3920 Flist_Ref => New_Reference_To (RTE (RE_Global_Final_List), Loc),
3921 With_Attach => Make_Integer_Literal (Loc, 0)));
3927 -- Could use comment here ???
3929 when RE_Not_Available =>
3931 end Make_Tag_Ctrl_Assignment;