1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2004, Free Software Foundation, Inc. --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 2, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
20 -- MA 02111-1307, USA. --
22 -- GNAT was originally developed by the GNAT team at New York University. --
23 -- Extensive contributions were provided by Ada Core Technologies Inc. --
25 ------------------------------------------------------------------------------
27 with Atree; use Atree;
28 with Checks; use Checks;
29 with Einfo; use Einfo;
30 with Exp_Aggr; use Exp_Aggr;
31 with Exp_Ch7; use Exp_Ch7;
32 with Exp_Ch11; use Exp_Ch11;
33 with Exp_Dbug; use Exp_Dbug;
34 with Exp_Pakd; use Exp_Pakd;
35 with Exp_Tss; use Exp_Tss;
36 with Exp_Util; use Exp_Util;
37 with Hostparm; use Hostparm;
38 with Nlists; use Nlists;
39 with Nmake; use Nmake;
41 with Restrict; use Restrict;
42 with Rident; use Rident;
43 with Rtsfind; use Rtsfind;
44 with Sinfo; use Sinfo;
46 with Sem_Ch8; use Sem_Ch8;
47 with Sem_Ch13; use Sem_Ch13;
48 with Sem_Eval; use Sem_Eval;
49 with Sem_Res; use Sem_Res;
50 with Sem_Util; use Sem_Util;
51 with Snames; use Snames;
52 with Stand; use Stand;
53 with Stringt; use Stringt;
54 with Tbuild; use Tbuild;
55 with Uintp; use Uintp;
56 with Validsw; use Validsw;
58 package body Exp_Ch5 is
60 function Change_Of_Representation (N : Node_Id) return Boolean;
61 -- Determine if the right hand side of the assignment N is a type
62 -- conversion which requires a change of representation. Called
63 -- only for the array and record cases.
65 procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id);
66 -- N is an assignment which assigns an array value. This routine process
67 -- the various special cases and checks required for such assignments,
68 -- including change of representation. Rhs is normally simply the right
69 -- hand side of the assignment, except that if the right hand side is
70 -- a type conversion or a qualified expression, then the Rhs is the
71 -- actual expression inside any such type conversions or qualifications.
73 function Expand_Assign_Array_Loop
80 Rev : Boolean) return Node_Id;
81 -- N is an assignment statement which assigns an array value. This routine
82 -- expands the assignment into a loop (or nested loops for the case of a
83 -- multi-dimensional array) to do the assignment component by component.
84 -- Larray and Rarray are the entities of the actual arrays on the left
85 -- hand and right hand sides. L_Type and R_Type are the types of these
86 -- arrays (which may not be the same, due to either sliding, or to a
87 -- change of representation case). Ndim is the number of dimensions and
88 -- the parameter Rev indicates if the loops run normally (Rev = False),
89 -- or reversed (Rev = True). The value returned is the constructed
90 -- loop statement. Auxiliary declarations are inserted before node N
91 -- using the standard Insert_Actions mechanism.
93 procedure Expand_Assign_Record (N : Node_Id);
94 -- N is an assignment of a non-tagged record value. This routine handles
95 -- the case where the assignment must be made component by component,
96 -- either because the target is not byte aligned, or there is a change
99 function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id;
100 -- Generate the necessary code for controlled and Tagged assignment,
101 -- that is to say, finalization of the target before, adjustement of
102 -- the target after and save and restore of the tag and finalization
103 -- pointers which are not 'part of the value' and must not be changed
104 -- upon assignment. N is the original Assignment node.
106 function Possible_Bit_Aligned_Component (N : Node_Id) return Boolean;
107 -- This function is used in processing the assignment of a record or
108 -- indexed component. The argument N is either the left hand or right
109 -- hand side of an assignment, and this function determines if there
110 -- is a record component reference where the record may be bit aligned
111 -- in a manner that causes trouble for the back end (see description
112 -- of Sem_Util.Component_May_Be_Bit_Aligned for further details).
114 ------------------------------
115 -- Change_Of_Representation --
116 ------------------------------
118 function Change_Of_Representation (N : Node_Id) return Boolean is
119 Rhs : constant Node_Id := Expression (N);
122 Nkind (Rhs) = N_Type_Conversion
124 not Same_Representation (Etype (Rhs), Etype (Expression (Rhs)));
125 end Change_Of_Representation;
127 -------------------------
128 -- Expand_Assign_Array --
129 -------------------------
131 -- There are two issues here. First, do we let Gigi do a block move, or
132 -- do we expand out into a loop? Second, we need to set the two flags
133 -- Forwards_OK and Backwards_OK which show whether the block move (or
134 -- corresponding loops) can be legitimately done in a forwards (low to
135 -- high) or backwards (high to low) manner.
137 procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id) is
138 Loc : constant Source_Ptr := Sloc (N);
140 Lhs : constant Node_Id := Name (N);
142 Act_Lhs : constant Node_Id := Get_Referenced_Object (Lhs);
143 Act_Rhs : Node_Id := Get_Referenced_Object (Rhs);
145 L_Type : constant Entity_Id :=
146 Underlying_Type (Get_Actual_Subtype (Act_Lhs));
147 R_Type : Entity_Id :=
148 Underlying_Type (Get_Actual_Subtype (Act_Rhs));
150 L_Slice : constant Boolean := Nkind (Act_Lhs) = N_Slice;
151 R_Slice : constant Boolean := Nkind (Act_Rhs) = N_Slice;
153 Crep : constant Boolean := Change_Of_Representation (N);
158 Ndim : constant Pos := Number_Dimensions (L_Type);
160 Loop_Required : Boolean := False;
161 -- This switch is set to True if the array move must be done using
162 -- an explicit front end generated loop.
164 procedure Apply_Dereference (Arg : in out Node_Id);
165 -- If the argument is an access to an array, and the assignment is
166 -- converted into a procedure call, apply explicit dereference.
168 function Has_Address_Clause (Exp : Node_Id) return Boolean;
169 -- Test if Exp is a reference to an array whose declaration has
170 -- an address clause, or it is a slice of such an array.
172 function Is_Formal_Array (Exp : Node_Id) return Boolean;
173 -- Test if Exp is a reference to an array which is either a formal
174 -- parameter or a slice of a formal parameter. These are the cases
175 -- where hidden aliasing can occur.
177 function Is_Non_Local_Array (Exp : Node_Id) return Boolean;
178 -- Determine if Exp is a reference to an array variable which is other
179 -- than an object defined in the current scope, or a slice of such
180 -- an object. Such objects can be aliased to parameters (unlike local
181 -- array references).
183 -----------------------
184 -- Apply_Dereference --
185 -----------------------
187 procedure Apply_Dereference (Arg : in out Node_Id) is
188 Typ : constant Entity_Id := Etype (Arg);
190 if Is_Access_Type (Typ) then
191 Rewrite (Arg, Make_Explicit_Dereference (Loc,
192 Prefix => Relocate_Node (Arg)));
193 Analyze_And_Resolve (Arg, Designated_Type (Typ));
195 end Apply_Dereference;
197 ------------------------
198 -- Has_Address_Clause --
199 ------------------------
201 function Has_Address_Clause (Exp : Node_Id) return Boolean is
204 (Is_Entity_Name (Exp) and then
205 Present (Address_Clause (Entity (Exp))))
207 (Nkind (Exp) = N_Slice and then Has_Address_Clause (Prefix (Exp)));
208 end Has_Address_Clause;
210 ---------------------
211 -- Is_Formal_Array --
212 ---------------------
214 function Is_Formal_Array (Exp : Node_Id) return Boolean is
217 (Is_Entity_Name (Exp) and then Is_Formal (Entity (Exp)))
219 (Nkind (Exp) = N_Slice and then Is_Formal_Array (Prefix (Exp)));
222 ------------------------
223 -- Is_Non_Local_Array --
224 ------------------------
226 function Is_Non_Local_Array (Exp : Node_Id) return Boolean is
228 return (Is_Entity_Name (Exp)
229 and then Scope (Entity (Exp)) /= Current_Scope)
230 or else (Nkind (Exp) = N_Slice
231 and then Is_Non_Local_Array (Prefix (Exp)));
232 end Is_Non_Local_Array;
234 -- Determine if Lhs, Rhs are formal arrays or nonlocal arrays
236 Lhs_Formal : constant Boolean := Is_Formal_Array (Act_Lhs);
237 Rhs_Formal : constant Boolean := Is_Formal_Array (Act_Rhs);
239 Lhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Lhs);
240 Rhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Rhs);
242 -- Start of processing for Expand_Assign_Array
245 -- Deal with length check, note that the length check is done with
246 -- respect to the right hand side as given, not a possible underlying
247 -- renamed object, since this would generate incorrect extra checks.
249 Apply_Length_Check (Rhs, L_Type);
251 -- We start by assuming that the move can be done in either
252 -- direction, i.e. that the two sides are completely disjoint.
254 Set_Forwards_OK (N, True);
255 Set_Backwards_OK (N, True);
257 -- Normally it is only the slice case that can lead to overlap,
258 -- and explicit checks for slices are made below. But there is
259 -- one case where the slice can be implicit and invisible to us
260 -- and that is the case where we have a one dimensional array,
261 -- and either both operands are parameters, or one is a parameter
262 -- and the other is a global variable. In this case the parameter
263 -- could be a slice that overlaps with the other parameter.
265 -- Check for the case of slices requiring an explicit loop. Normally
266 -- it is only the explicit slice cases that bother us, but in the
267 -- case of one dimensional arrays, parameters can be slices that
268 -- are passed by reference, so we can have aliasing for assignments
269 -- from one parameter to another, or assignments between parameters
270 -- and nonlocal variables. However, if the array subtype is a
271 -- constrained first subtype in the parameter case, then we don't
272 -- have to worry about overlap, since slice assignments aren't
273 -- possible (other than for a slice denoting the whole array).
275 -- Note: overlap is never possible if there is a change of
276 -- representation, so we can exclude this case.
281 ((Lhs_Formal and Rhs_Formal)
283 (Lhs_Formal and Rhs_Non_Local_Var)
285 (Rhs_Formal and Lhs_Non_Local_Var))
287 (not Is_Constrained (Etype (Lhs))
288 or else not Is_First_Subtype (Etype (Lhs)))
290 -- In the case of compiling for the Java Virtual Machine,
291 -- slices are always passed by making a copy, so we don't
292 -- have to worry about overlap. We also want to prevent
293 -- generation of "<" comparisons for array addresses,
294 -- since that's a meaningless operation on the JVM.
298 Set_Forwards_OK (N, False);
299 Set_Backwards_OK (N, False);
301 -- Note: the bit-packed case is not worrisome here, since if
302 -- we have a slice passed as a parameter, it is always aligned
303 -- on a byte boundary, and if there are no explicit slices, the
304 -- assignment can be performed directly.
307 -- We certainly must use a loop for change of representation
308 -- and also we use the operand of the conversion on the right
309 -- hand side as the effective right hand side (the component
310 -- types must match in this situation).
313 Act_Rhs := Get_Referenced_Object (Rhs);
314 R_Type := Get_Actual_Subtype (Act_Rhs);
315 Loop_Required := True;
317 -- We require a loop if the left side is possibly bit unaligned
319 elsif Possible_Bit_Aligned_Component (Lhs)
321 Possible_Bit_Aligned_Component (Rhs)
323 Loop_Required := True;
325 -- Arrays with controlled components are expanded into a loop
326 -- to force calls to adjust at the component level.
328 elsif Has_Controlled_Component (L_Type) then
329 Loop_Required := True;
331 -- Case where no slice is involved
333 elsif not L_Slice and not R_Slice then
335 -- The following code deals with the case of unconstrained bit
336 -- packed arrays. The problem is that the template for such
337 -- arrays contains the bounds of the actual source level array,
339 -- But the copy of an entire array requires the bounds of the
340 -- underlying array. It would be nice if the back end could take
341 -- care of this, but right now it does not know how, so if we
342 -- have such a type, then we expand out into a loop, which is
343 -- inefficient but works correctly. If we don't do this, we
344 -- get the wrong length computed for the array to be moved.
345 -- The two cases we need to worry about are:
347 -- Explicit deference of an unconstrained packed array type as
348 -- in the following example:
351 -- type BITS is array(INTEGER range <>) of BOOLEAN;
352 -- pragma PACK(BITS);
353 -- type A is access BITS;
356 -- P1 := new BITS (1 .. 65_535);
357 -- P2 := new BITS (1 .. 65_535);
361 -- A formal parameter reference with an unconstrained bit
362 -- array type is the other case we need to worry about (here
363 -- we assume the same BITS type declared above:
365 -- procedure Write_All (File : out BITS; Contents : in BITS);
367 -- File.Storage := Contents;
370 -- We expand to a loop in either of these two cases.
372 -- Question for future thought. Another potentially more efficient
373 -- approach would be to create the actual subtype, and then do an
374 -- unchecked conversion to this actual subtype ???
376 Check_Unconstrained_Bit_Packed_Array : declare
378 function Is_UBPA_Reference (Opnd : Node_Id) return Boolean;
379 -- Function to perform required test for the first case,
380 -- above (dereference of an unconstrained bit packed array)
382 -----------------------
383 -- Is_UBPA_Reference --
384 -----------------------
386 function Is_UBPA_Reference (Opnd : Node_Id) return Boolean is
387 Typ : constant Entity_Id := Underlying_Type (Etype (Opnd));
389 Des_Type : Entity_Id;
392 if Present (Packed_Array_Type (Typ))
393 and then Is_Array_Type (Packed_Array_Type (Typ))
394 and then not Is_Constrained (Packed_Array_Type (Typ))
398 elsif Nkind (Opnd) = N_Explicit_Dereference then
399 P_Type := Underlying_Type (Etype (Prefix (Opnd)));
401 if not Is_Access_Type (P_Type) then
405 Des_Type := Designated_Type (P_Type);
407 Is_Bit_Packed_Array (Des_Type)
408 and then not Is_Constrained (Des_Type);
414 end Is_UBPA_Reference;
416 -- Start of processing for Check_Unconstrained_Bit_Packed_Array
419 if Is_UBPA_Reference (Lhs)
421 Is_UBPA_Reference (Rhs)
423 Loop_Required := True;
425 -- Here if we do not have the case of a reference to a bit
426 -- packed unconstrained array case. In this case gigi can
427 -- most certainly handle the assignment if a forwards move
430 -- (could it handle the backwards case also???)
432 elsif Forwards_OK (N) then
435 end Check_Unconstrained_Bit_Packed_Array;
437 -- Gigi can always handle the assignment if the right side is a string
438 -- literal (note that overlap is definitely impossible in this case).
439 -- If the type is packed, a string literal is always converted into a
440 -- aggregate, except in the case of a null slice, for which no aggregate
441 -- can be written. In that case, rewrite the assignment as a null
442 -- statement, a length check has already been emitted to verify that
443 -- the range of the left-hand side is empty.
445 -- Note that this code is not executed if we had an assignment of
446 -- a string literal to a non-bit aligned component of a record, a
447 -- case which cannot be handled by the backend
449 elsif Nkind (Rhs) = N_String_Literal then
450 if String_Length (Strval (Rhs)) = 0
451 and then Is_Bit_Packed_Array (L_Type)
453 Rewrite (N, Make_Null_Statement (Loc));
459 -- If either operand is bit packed, then we need a loop, since we
460 -- can't be sure that the slice is byte aligned. Similarly, if either
461 -- operand is a possibly unaligned slice, then we need a loop (since
462 -- gigi cannot handle unaligned slices).
464 elsif Is_Bit_Packed_Array (L_Type)
465 or else Is_Bit_Packed_Array (R_Type)
466 or else Is_Possibly_Unaligned_Slice (Lhs)
467 or else Is_Possibly_Unaligned_Slice (Rhs)
469 Loop_Required := True;
471 -- If we are not bit-packed, and we have only one slice, then no
472 -- overlap is possible except in the parameter case, so we can let
473 -- gigi handle things.
475 elsif not (L_Slice and R_Slice) then
476 if Forwards_OK (N) then
481 -- If the right-hand side is a string literal, introduce a temporary
482 -- for it, for use in the generated loop that will follow.
484 if Nkind (Rhs) = N_String_Literal then
486 Temp : constant Entity_Id :=
487 Make_Defining_Identifier (Loc, Name_T);
492 Make_Object_Declaration (Loc,
493 Defining_Identifier => Temp,
494 Object_Definition => New_Occurrence_Of (L_Type, Loc),
495 Expression => Relocate_Node (Rhs));
497 Insert_Action (N, Decl);
498 Rewrite (Rhs, New_Occurrence_Of (Temp, Loc));
499 R_Type := Etype (Temp);
503 -- Come here to complete the analysis
505 -- Loop_Required: Set to True if we know that a loop is required
506 -- regardless of overlap considerations.
508 -- Forwards_OK: Set to False if we already know that a forwards
509 -- move is not safe, else set to True.
511 -- Backwards_OK: Set to False if we already know that a backwards
512 -- move is not safe, else set to True
514 -- Our task at this stage is to complete the overlap analysis, which
515 -- can result in possibly setting Forwards_OK or Backwards_OK to
516 -- False, and then generating the final code, either by deciding
517 -- that it is OK after all to let Gigi handle it, or by generating
518 -- appropriate code in the front end.
521 L_Index_Typ : constant Node_Id := Etype (First_Index (L_Type));
522 R_Index_Typ : constant Node_Id := Etype (First_Index (R_Type));
524 Left_Lo : constant Node_Id := Type_Low_Bound (L_Index_Typ);
525 Left_Hi : constant Node_Id := Type_High_Bound (L_Index_Typ);
526 Right_Lo : constant Node_Id := Type_Low_Bound (R_Index_Typ);
527 Right_Hi : constant Node_Id := Type_High_Bound (R_Index_Typ);
529 Act_L_Array : Node_Id;
530 Act_R_Array : Node_Id;
536 Cresult : Compare_Result;
539 -- Get the expressions for the arrays. If we are dealing with a
540 -- private type, then convert to the underlying type. We can do
541 -- direct assignments to an array that is a private type, but
542 -- we cannot assign to elements of the array without this extra
543 -- unchecked conversion.
545 if Nkind (Act_Lhs) = N_Slice then
546 Larray := Prefix (Act_Lhs);
550 if Is_Private_Type (Etype (Larray)) then
553 (Underlying_Type (Etype (Larray)), Larray);
557 if Nkind (Act_Rhs) = N_Slice then
558 Rarray := Prefix (Act_Rhs);
562 if Is_Private_Type (Etype (Rarray)) then
565 (Underlying_Type (Etype (Rarray)), Rarray);
569 -- If both sides are slices, we must figure out whether
570 -- it is safe to do the move in one direction or the other
571 -- It is always safe if there is a change of representation
572 -- since obviously two arrays with different representations
573 -- cannot possibly overlap.
575 if (not Crep) and L_Slice and R_Slice then
576 Act_L_Array := Get_Referenced_Object (Prefix (Act_Lhs));
577 Act_R_Array := Get_Referenced_Object (Prefix (Act_Rhs));
579 -- If both left and right hand arrays are entity names, and
580 -- refer to different entities, then we know that the move
581 -- is safe (the two storage areas are completely disjoint).
583 if Is_Entity_Name (Act_L_Array)
584 and then Is_Entity_Name (Act_R_Array)
585 and then Entity (Act_L_Array) /= Entity (Act_R_Array)
589 -- Otherwise, we assume the worst, which is that the two
590 -- arrays are the same array. There is no need to check if
591 -- we know that is the case, because if we don't know it,
592 -- we still have to assume it!
594 -- Generally if the same array is involved, then we have
595 -- an overlapping case. We will have to really assume the
596 -- worst (i.e. set neither of the OK flags) unless we can
597 -- determine the lower or upper bounds at compile time and
601 Cresult := Compile_Time_Compare (Left_Lo, Right_Lo);
603 if Cresult = Unknown then
604 Cresult := Compile_Time_Compare (Left_Hi, Right_Hi);
608 when LT | LE | EQ => Set_Backwards_OK (N, False);
609 when GT | GE => Set_Forwards_OK (N, False);
610 when NE | Unknown => Set_Backwards_OK (N, False);
611 Set_Forwards_OK (N, False);
616 -- If after that analysis, Forwards_OK is still True, and
617 -- Loop_Required is False, meaning that we have not discovered
618 -- some non-overlap reason for requiring a loop, then we can
619 -- still let gigi handle it.
621 if not Loop_Required then
622 if Forwards_OK (N) then
627 -- Here is where a memmove would be appropriate ???
631 -- At this stage we have to generate an explicit loop, and
632 -- we have the following cases:
634 -- Forwards_OK = True
636 -- Rnn : right_index := right_index'First;
637 -- for Lnn in left-index loop
638 -- left (Lnn) := right (Rnn);
639 -- Rnn := right_index'Succ (Rnn);
642 -- Note: the above code MUST be analyzed with checks off,
643 -- because otherwise the Succ could overflow. But in any
644 -- case this is more efficient!
646 -- Forwards_OK = False, Backwards_OK = True
648 -- Rnn : right_index := right_index'Last;
649 -- for Lnn in reverse left-index loop
650 -- left (Lnn) := right (Rnn);
651 -- Rnn := right_index'Pred (Rnn);
654 -- Note: the above code MUST be analyzed with checks off,
655 -- because otherwise the Pred could overflow. But in any
656 -- case this is more efficient!
658 -- Forwards_OK = Backwards_OK = False
660 -- This only happens if we have the same array on each side. It is
661 -- possible to create situations using overlays that violate this,
662 -- but we simply do not promise to get this "right" in this case.
664 -- There are two possible subcases. If the No_Implicit_Conditionals
665 -- restriction is set, then we generate the following code:
668 -- T : constant <operand-type> := rhs;
673 -- If implicit conditionals are permitted, then we generate:
675 -- if Left_Lo <= Right_Lo then
676 -- <code for Forwards_OK = True above>
678 -- <code for Backwards_OK = True above>
681 -- Cases where either Forwards_OK or Backwards_OK is true
683 if Forwards_OK (N) or else Backwards_OK (N) then
684 if Controlled_Type (Component_Type (L_Type))
685 and then Base_Type (L_Type) = Base_Type (R_Type)
687 and then not No_Ctrl_Actions (N)
690 Proc : constant Entity_Id :=
691 TSS (Base_Type (L_Type), TSS_Slice_Assign);
695 Apply_Dereference (Larray);
696 Apply_Dereference (Rarray);
697 Actuals := New_List (
698 Duplicate_Subexpr (Larray, Name_Req => True),
699 Duplicate_Subexpr (Rarray, Name_Req => True),
700 Duplicate_Subexpr (Left_Lo, Name_Req => True),
701 Duplicate_Subexpr (Left_Hi, Name_Req => True),
702 Duplicate_Subexpr (Right_Lo, Name_Req => True),
703 Duplicate_Subexpr (Right_Hi, Name_Req => True));
705 if Forwards_OK (N) then
707 New_Occurrence_Of (Standard_False, Loc));
710 New_Occurrence_Of (Standard_True, Loc));
714 Make_Procedure_Call_Statement (Loc,
715 Name => New_Reference_To (Proc, Loc),
716 Parameter_Associations => Actuals));
721 Expand_Assign_Array_Loop
722 (N, Larray, Rarray, L_Type, R_Type, Ndim,
723 Rev => not Forwards_OK (N)));
726 -- Case of both are false with No_Implicit_Conditionals
728 elsif Restriction_Active (No_Implicit_Conditionals) then
730 T : constant Entity_Id :=
731 Make_Defining_Identifier (Loc, Chars => Name_T);
735 Make_Block_Statement (Loc,
736 Declarations => New_List (
737 Make_Object_Declaration (Loc,
738 Defining_Identifier => T,
739 Constant_Present => True,
741 New_Occurrence_Of (Etype (Rhs), Loc),
742 Expression => Relocate_Node (Rhs))),
744 Handled_Statement_Sequence =>
745 Make_Handled_Sequence_Of_Statements (Loc,
746 Statements => New_List (
747 Make_Assignment_Statement (Loc,
748 Name => Relocate_Node (Lhs),
749 Expression => New_Occurrence_Of (T, Loc))))));
752 -- Case of both are false with implicit conditionals allowed
755 -- Before we generate this code, we must ensure that the
756 -- left and right side array types are defined. They may
757 -- be itypes, and we cannot let them be defined inside the
758 -- if, since the first use in the then may not be executed.
760 Ensure_Defined (L_Type, N);
761 Ensure_Defined (R_Type, N);
763 -- We normally compare addresses to find out which way round
764 -- to do the loop, since this is realiable, and handles the
765 -- cases of parameters, conversions etc. But we can't do that
766 -- in the bit packed case or the Java VM case, because addresses
769 if not Is_Bit_Packed_Array (L_Type) and then not Java_VM then
773 Unchecked_Convert_To (RTE (RE_Integer_Address),
774 Make_Attribute_Reference (Loc,
776 Make_Indexed_Component (Loc,
778 Duplicate_Subexpr_Move_Checks (Larray, True),
779 Expressions => New_List (
780 Make_Attribute_Reference (Loc,
784 Attribute_Name => Name_First))),
785 Attribute_Name => Name_Address)),
788 Unchecked_Convert_To (RTE (RE_Integer_Address),
789 Make_Attribute_Reference (Loc,
791 Make_Indexed_Component (Loc,
793 Duplicate_Subexpr_Move_Checks (Rarray, True),
794 Expressions => New_List (
795 Make_Attribute_Reference (Loc,
799 Attribute_Name => Name_First))),
800 Attribute_Name => Name_Address)));
802 -- For the bit packed and Java VM cases we use the bounds.
803 -- That's OK, because we don't have to worry about parameters,
804 -- since they cannot cause overlap. Perhaps we should worry
805 -- about weird slice conversions ???
808 -- Copy the bounds and reset the Analyzed flag, because the
809 -- bounds of the index type itself may be universal, and must
810 -- must be reaanalyzed to acquire the proper type for Gigi.
812 Cleft_Lo := New_Copy_Tree (Left_Lo);
813 Cright_Lo := New_Copy_Tree (Right_Lo);
814 Set_Analyzed (Cleft_Lo, False);
815 Set_Analyzed (Cright_Lo, False);
819 Left_Opnd => Cleft_Lo,
820 Right_Opnd => Cright_Lo);
823 if Controlled_Type (Component_Type (L_Type))
824 and then Base_Type (L_Type) = Base_Type (R_Type)
826 and then not No_Ctrl_Actions (N)
829 -- Call TSS procedure for array assignment, passing the
830 -- the explicit bounds of right- and left-hand side.
833 Proc : constant Node_Id :=
834 TSS (Base_Type (L_Type), TSS_Slice_Assign);
838 Apply_Dereference (Larray);
839 Apply_Dereference (Rarray);
840 Actuals := New_List (
841 Duplicate_Subexpr (Larray, Name_Req => True),
842 Duplicate_Subexpr (Rarray, Name_Req => True),
843 Duplicate_Subexpr (Left_Lo, Name_Req => True),
844 Duplicate_Subexpr (Left_Hi, Name_Req => True),
845 Duplicate_Subexpr (Right_Lo, Name_Req => True),
846 Duplicate_Subexpr (Right_Hi, Name_Req => True));
847 Append_To (Actuals, Condition);
850 Make_Procedure_Call_Statement (Loc,
851 Name => New_Reference_To (Proc, Loc),
852 Parameter_Associations => Actuals));
857 Make_Implicit_If_Statement (N,
858 Condition => Condition,
860 Then_Statements => New_List (
861 Expand_Assign_Array_Loop
862 (N, Larray, Rarray, L_Type, R_Type, Ndim,
865 Else_Statements => New_List (
866 Expand_Assign_Array_Loop
867 (N, Larray, Rarray, L_Type, R_Type, Ndim,
872 Analyze (N, Suppress => All_Checks);
876 when RE_Not_Available =>
878 end Expand_Assign_Array;
880 ------------------------------
881 -- Expand_Assign_Array_Loop --
882 ------------------------------
884 -- The following is an example of the loop generated for the case of
885 -- a two-dimensional array:
890 -- for L1b in 1 .. 100 loop
894 -- for L3b in 1 .. 100 loop
895 -- vm1 (L1b, L3b) := vm2 (R2b, R4b);
896 -- R4b := Tm1X2'succ(R4b);
899 -- R2b := Tm1X1'succ(R2b);
903 -- Here Rev is False, and Tm1Xn are the subscript types for the right
904 -- hand side. The declarations of R2b and R4b are inserted before the
905 -- original assignment statement.
907 function Expand_Assign_Array_Loop
914 Rev : Boolean) return Node_Id
916 Loc : constant Source_Ptr := Sloc (N);
918 Lnn : array (1 .. Ndim) of Entity_Id;
919 Rnn : array (1 .. Ndim) of Entity_Id;
920 -- Entities used as subscripts on left and right sides
922 L_Index_Type : array (1 .. Ndim) of Entity_Id;
923 R_Index_Type : array (1 .. Ndim) of Entity_Id;
924 -- Left and right index types
936 F_Or_L := Name_First;
940 -- Setup index types and subscript entities
947 L_Index := First_Index (L_Type);
948 R_Index := First_Index (R_Type);
950 for J in 1 .. Ndim loop
952 Make_Defining_Identifier (Loc,
953 Chars => New_Internal_Name ('L'));
956 Make_Defining_Identifier (Loc,
957 Chars => New_Internal_Name ('R'));
959 L_Index_Type (J) := Etype (L_Index);
960 R_Index_Type (J) := Etype (R_Index);
962 Next_Index (L_Index);
963 Next_Index (R_Index);
967 -- Now construct the assignment statement
970 ExprL : constant List_Id := New_List;
971 ExprR : constant List_Id := New_List;
974 for J in 1 .. Ndim loop
975 Append_To (ExprL, New_Occurrence_Of (Lnn (J), Loc));
976 Append_To (ExprR, New_Occurrence_Of (Rnn (J), Loc));
980 Make_Assignment_Statement (Loc,
982 Make_Indexed_Component (Loc,
983 Prefix => Duplicate_Subexpr (Larray, Name_Req => True),
984 Expressions => ExprL),
986 Make_Indexed_Component (Loc,
987 Prefix => Duplicate_Subexpr (Rarray, Name_Req => True),
988 Expressions => ExprR));
990 -- Propagate the No_Ctrl_Actions flag to individual assignments
992 Set_No_Ctrl_Actions (Assign, No_Ctrl_Actions (N));
995 -- Now construct the loop from the inside out, with the last subscript
996 -- varying most rapidly. Note that Assign is first the raw assignment
997 -- statement, and then subsequently the loop that wraps it up.
999 for J in reverse 1 .. Ndim loop
1001 Make_Block_Statement (Loc,
1002 Declarations => New_List (
1003 Make_Object_Declaration (Loc,
1004 Defining_Identifier => Rnn (J),
1005 Object_Definition =>
1006 New_Occurrence_Of (R_Index_Type (J), Loc),
1008 Make_Attribute_Reference (Loc,
1009 Prefix => New_Occurrence_Of (R_Index_Type (J), Loc),
1010 Attribute_Name => F_Or_L))),
1012 Handled_Statement_Sequence =>
1013 Make_Handled_Sequence_Of_Statements (Loc,
1014 Statements => New_List (
1015 Make_Implicit_Loop_Statement (N,
1017 Make_Iteration_Scheme (Loc,
1018 Loop_Parameter_Specification =>
1019 Make_Loop_Parameter_Specification (Loc,
1020 Defining_Identifier => Lnn (J),
1021 Reverse_Present => Rev,
1022 Discrete_Subtype_Definition =>
1023 New_Reference_To (L_Index_Type (J), Loc))),
1025 Statements => New_List (
1028 Make_Assignment_Statement (Loc,
1029 Name => New_Occurrence_Of (Rnn (J), Loc),
1031 Make_Attribute_Reference (Loc,
1033 New_Occurrence_Of (R_Index_Type (J), Loc),
1034 Attribute_Name => S_Or_P,
1035 Expressions => New_List (
1036 New_Occurrence_Of (Rnn (J), Loc)))))))));
1040 end Expand_Assign_Array_Loop;
1042 --------------------------
1043 -- Expand_Assign_Record --
1044 --------------------------
1046 -- The only processing required is in the change of representation
1047 -- case, where we must expand the assignment to a series of field
1048 -- by field assignments.
1050 procedure Expand_Assign_Record (N : Node_Id) is
1051 Lhs : constant Node_Id := Name (N);
1052 Rhs : Node_Id := Expression (N);
1055 -- If change of representation, then extract the real right hand
1056 -- side from the type conversion, and proceed with component-wise
1057 -- assignment, since the two types are not the same as far as the
1058 -- back end is concerned.
1060 if Change_Of_Representation (N) then
1061 Rhs := Expression (Rhs);
1063 -- If this may be a case of a large bit aligned component, then
1064 -- proceed with component-wise assignment, to avoid possible
1065 -- clobbering of other components sharing bits in the first or
1066 -- last byte of the component to be assigned.
1068 elsif Possible_Bit_Aligned_Component (Lhs)
1070 Possible_Bit_Aligned_Component (Rhs)
1074 -- If neither condition met, then nothing special to do, the back end
1075 -- can handle assignment of the entire component as a single entity.
1081 -- At this stage we know that we must do a component wise assignment
1084 Loc : constant Source_Ptr := Sloc (N);
1085 R_Typ : constant Entity_Id := Base_Type (Etype (Rhs));
1086 L_Typ : constant Entity_Id := Base_Type (Etype (Lhs));
1087 Decl : constant Node_Id := Declaration_Node (R_Typ);
1091 function Find_Component
1093 Comp : Entity_Id) return Entity_Id;
1094 -- Find the component with the given name in the underlying record
1095 -- declaration for Typ. We need to use the actual entity because
1096 -- the type may be private and resolution by identifier alone would
1099 function Make_Component_List_Assign (CL : Node_Id) return List_Id;
1100 -- Returns a sequence of statements to assign the components that
1101 -- are referenced in the given component list.
1103 function Make_Field_Assign (C : Entity_Id) return Node_Id;
1104 -- Given C, the entity for a discriminant or component, build
1105 -- an assignment for the corresponding field values.
1107 function Make_Field_Assigns (CI : List_Id) return List_Id;
1108 -- Given CI, a component items list, construct series of statements
1109 -- for fieldwise assignment of the corresponding components.
1111 --------------------
1112 -- Find_Component --
1113 --------------------
1115 function Find_Component
1117 Comp : Entity_Id) return Entity_Id
1119 Utyp : constant Entity_Id := Underlying_Type (Typ);
1123 C := First_Entity (Utyp);
1125 while Present (C) loop
1126 if Chars (C) = Chars (Comp) then
1132 raise Program_Error;
1135 --------------------------------
1136 -- Make_Component_List_Assign --
1137 --------------------------------
1139 function Make_Component_List_Assign (CL : Node_Id) return List_Id is
1140 CI : constant List_Id := Component_Items (CL);
1141 VP : constant Node_Id := Variant_Part (CL);
1150 Result := Make_Field_Assigns (CI);
1152 if Present (VP) then
1154 V := First_Non_Pragma (Variants (VP));
1156 while Present (V) loop
1159 DC := First (Discrete_Choices (V));
1160 while Present (DC) loop
1161 Append_To (DCH, New_Copy_Tree (DC));
1166 Make_Case_Statement_Alternative (Loc,
1167 Discrete_Choices => DCH,
1169 Make_Component_List_Assign (Component_List (V))));
1170 Next_Non_Pragma (V);
1174 Make_Case_Statement (Loc,
1176 Make_Selected_Component (Loc,
1177 Prefix => Duplicate_Subexpr (Rhs),
1179 Make_Identifier (Loc, Chars (Name (VP)))),
1180 Alternatives => Alts));
1185 end Make_Component_List_Assign;
1187 -----------------------
1188 -- Make_Field_Assign --
1189 -----------------------
1191 function Make_Field_Assign (C : Entity_Id) return Node_Id is
1196 Make_Assignment_Statement (Loc,
1198 Make_Selected_Component (Loc,
1199 Prefix => Duplicate_Subexpr (Lhs),
1201 New_Occurrence_Of (Find_Component (L_Typ, C), Loc)),
1203 Make_Selected_Component (Loc,
1204 Prefix => Duplicate_Subexpr (Rhs),
1205 Selector_Name => New_Occurrence_Of (C, Loc)));
1207 -- Set Assignment_OK, so discriminants can be assigned
1209 Set_Assignment_OK (Name (A), True);
1211 end Make_Field_Assign;
1213 ------------------------
1214 -- Make_Field_Assigns --
1215 ------------------------
1217 function Make_Field_Assigns (CI : List_Id) return List_Id is
1225 while Present (Item) loop
1226 if Nkind (Item) = N_Component_Declaration then
1228 (Result, Make_Field_Assign (Defining_Identifier (Item)));
1235 end Make_Field_Assigns;
1237 -- Start of processing for Expand_Assign_Record
1240 -- Note that we use the base types for this processing. This results
1241 -- in some extra work in the constrained case, but the change of
1242 -- representation case is so unusual that it is not worth the effort.
1244 -- First copy the discriminants. This is done unconditionally. It
1245 -- is required in the unconstrained left side case, and also in the
1246 -- case where this assignment was constructed during the expansion
1247 -- of a type conversion (since initialization of discriminants is
1248 -- suppressed in this case). It is unnecessary but harmless in
1251 if Has_Discriminants (L_Typ) then
1252 F := First_Discriminant (R_Typ);
1253 while Present (F) loop
1254 Insert_Action (N, Make_Field_Assign (F));
1255 Next_Discriminant (F);
1259 -- We know the underlying type is a record, but its current view
1260 -- may be private. We must retrieve the usable record declaration.
1262 if Nkind (Decl) = N_Private_Type_Declaration
1263 and then Present (Full_View (R_Typ))
1265 RDef := Type_Definition (Declaration_Node (Full_View (R_Typ)));
1267 RDef := Type_Definition (Decl);
1270 if Nkind (RDef) = N_Record_Definition
1271 and then Present (Component_List (RDef))
1274 (N, Make_Component_List_Assign (Component_List (RDef)));
1276 Rewrite (N, Make_Null_Statement (Loc));
1280 end Expand_Assign_Record;
1282 -----------------------------------
1283 -- Expand_N_Assignment_Statement --
1284 -----------------------------------
1286 -- For array types, deal with slice assignments and setting the flags
1287 -- to indicate if it can be statically determined which direction the
1288 -- move should go in. Also deal with generating range/length checks.
1290 procedure Expand_N_Assignment_Statement (N : Node_Id) is
1291 Loc : constant Source_Ptr := Sloc (N);
1292 Lhs : constant Node_Id := Name (N);
1293 Rhs : constant Node_Id := Expression (N);
1294 Typ : constant Entity_Id := Underlying_Type (Etype (Lhs));
1298 -- First deal with generation of range check if required. For now
1299 -- we do this only for discrete types.
1301 if Do_Range_Check (Rhs)
1302 and then Is_Discrete_Type (Typ)
1304 Set_Do_Range_Check (Rhs, False);
1305 Generate_Range_Check (Rhs, Typ, CE_Range_Check_Failed);
1308 -- Check for a special case where a high level transformation is
1309 -- required. If we have either of:
1314 -- where P is a reference to a bit packed array, then we have to unwind
1315 -- the assignment. The exact meaning of being a reference to a bit
1316 -- packed array is as follows:
1318 -- An indexed component whose prefix is a bit packed array is a
1319 -- reference to a bit packed array.
1321 -- An indexed component or selected component whose prefix is a
1322 -- reference to a bit packed array is itself a reference ot a
1323 -- bit packed array.
1325 -- The required transformation is
1327 -- Tnn : prefix_type := P;
1328 -- Tnn.field := rhs;
1333 -- Tnn : prefix_type := P;
1334 -- Tnn (subscr) := rhs;
1337 -- Since P is going to be evaluated more than once, any subscripts
1338 -- in P must have their evaluation forced.
1340 if (Nkind (Lhs) = N_Indexed_Component
1342 Nkind (Lhs) = N_Selected_Component)
1343 and then Is_Ref_To_Bit_Packed_Array (Prefix (Lhs))
1346 BPAR_Expr : constant Node_Id := Relocate_Node (Prefix (Lhs));
1347 BPAR_Typ : constant Entity_Id := Etype (BPAR_Expr);
1348 Tnn : constant Entity_Id :=
1349 Make_Defining_Identifier (Loc,
1350 Chars => New_Internal_Name ('T'));
1353 -- Insert the post assignment first, because we want to copy
1354 -- the BPAR_Expr tree before it gets analyzed in the context
1355 -- of the pre assignment. Note that we do not analyze the
1356 -- post assignment yet (we cannot till we have completed the
1357 -- analysis of the pre assignment). As usual, the analysis
1358 -- of this post assignment will happen on its own when we
1359 -- "run into" it after finishing the current assignment.
1362 Make_Assignment_Statement (Loc,
1363 Name => New_Copy_Tree (BPAR_Expr),
1364 Expression => New_Occurrence_Of (Tnn, Loc)));
1366 -- At this stage BPAR_Expr is a reference to a bit packed
1367 -- array where the reference was not expanded in the original
1368 -- tree, since it was on the left side of an assignment. But
1369 -- in the pre-assignment statement (the object definition),
1370 -- BPAR_Expr will end up on the right hand side, and must be
1371 -- reexpanded. To achieve this, we reset the analyzed flag
1372 -- of all selected and indexed components down to the actual
1373 -- indexed component for the packed array.
1377 Set_Analyzed (Exp, False);
1379 if Nkind (Exp) = N_Selected_Component
1381 Nkind (Exp) = N_Indexed_Component
1383 Exp := Prefix (Exp);
1389 -- Now we can insert and analyze the pre-assignment.
1391 -- If the right-hand side requires a transient scope, it has
1392 -- already been placed on the stack. However, the declaration is
1393 -- inserted in the tree outside of this scope, and must reflect
1394 -- the proper scope for its variable. This awkward bit is forced
1395 -- by the stricter scope discipline imposed by GCC 2.97.
1398 Uses_Transient_Scope : constant Boolean :=
1399 Scope_Is_Transient and then N = Node_To_Be_Wrapped;
1402 if Uses_Transient_Scope then
1403 New_Scope (Scope (Current_Scope));
1406 Insert_Before_And_Analyze (N,
1407 Make_Object_Declaration (Loc,
1408 Defining_Identifier => Tnn,
1409 Object_Definition => New_Occurrence_Of (BPAR_Typ, Loc),
1410 Expression => BPAR_Expr));
1412 if Uses_Transient_Scope then
1417 -- Now fix up the original assignment and continue processing
1419 Rewrite (Prefix (Lhs),
1420 New_Occurrence_Of (Tnn, Loc));
1422 -- We do not need to reanalyze that assignment, and we do not need
1423 -- to worry about references to the temporary, but we do need to
1424 -- make sure that the temporary is not marked as a true constant
1425 -- since we now have a generate assignment to it!
1427 Set_Is_True_Constant (Tnn, False);
1431 -- When we have the appropriate type of aggregate in the
1432 -- expression (it has been determined during analysis of the
1433 -- aggregate by setting the delay flag), let's perform in place
1434 -- assignment and thus avoid creating a temporay.
1436 if Is_Delayed_Aggregate (Rhs) then
1437 Convert_Aggr_In_Assignment (N);
1438 Rewrite (N, Make_Null_Statement (Loc));
1443 -- Apply discriminant check if required. If Lhs is an access type
1444 -- to a designated type with discriminants, we must always check.
1446 if Has_Discriminants (Etype (Lhs)) then
1448 -- Skip discriminant check if change of representation. Will be
1449 -- done when the change of representation is expanded out.
1451 if not Change_Of_Representation (N) then
1452 Apply_Discriminant_Check (Rhs, Etype (Lhs), Lhs);
1455 -- If the type is private without discriminants, and the full type
1456 -- has discriminants (necessarily with defaults) a check may still be
1457 -- necessary if the Lhs is aliased. The private determinants must be
1458 -- visible to build the discriminant constraints.
1460 -- Only an explicit dereference that comes from source indicates
1461 -- aliasing. Access to formals of protected operations and entries
1462 -- create dereferences but are not semantic aliasings.
1464 elsif Is_Private_Type (Etype (Lhs))
1465 and then Has_Discriminants (Typ)
1466 and then Nkind (Lhs) = N_Explicit_Dereference
1467 and then Comes_From_Source (Lhs)
1470 Lt : constant Entity_Id := Etype (Lhs);
1472 Set_Etype (Lhs, Typ);
1473 Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs));
1474 Apply_Discriminant_Check (Rhs, Typ, Lhs);
1475 Set_Etype (Lhs, Lt);
1478 -- If the Lhs has a private type with unknown discriminants, it
1479 -- may have a full view with discriminants, but those are nameable
1480 -- only in the underlying type, so convert the Rhs to it before
1481 -- potential checking.
1483 elsif Has_Unknown_Discriminants (Base_Type (Etype (Lhs)))
1484 and then Has_Discriminants (Typ)
1486 Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs));
1487 Apply_Discriminant_Check (Rhs, Typ, Lhs);
1489 -- In the access type case, we need the same discriminant check,
1490 -- and also range checks if we have an access to constrained array.
1492 elsif Is_Access_Type (Etype (Lhs))
1493 and then Is_Constrained (Designated_Type (Etype (Lhs)))
1495 if Has_Discriminants (Designated_Type (Etype (Lhs))) then
1497 -- Skip discriminant check if change of representation. Will be
1498 -- done when the change of representation is expanded out.
1500 if not Change_Of_Representation (N) then
1501 Apply_Discriminant_Check (Rhs, Etype (Lhs));
1504 elsif Is_Array_Type (Designated_Type (Etype (Lhs))) then
1505 Apply_Range_Check (Rhs, Etype (Lhs));
1507 if Is_Constrained (Etype (Lhs)) then
1508 Apply_Length_Check (Rhs, Etype (Lhs));
1511 if Nkind (Rhs) = N_Allocator then
1513 Target_Typ : constant Entity_Id := Etype (Expression (Rhs));
1514 C_Es : Check_Result;
1521 Etype (Designated_Type (Etype (Lhs))));
1533 -- Apply range check for access type case
1535 elsif Is_Access_Type (Etype (Lhs))
1536 and then Nkind (Rhs) = N_Allocator
1537 and then Nkind (Expression (Rhs)) = N_Qualified_Expression
1539 Analyze_And_Resolve (Expression (Rhs));
1541 (Expression (Rhs), Designated_Type (Etype (Lhs)));
1544 -- If we are assigning an access type and the left side is an
1545 -- entity, then make sure that Is_Known_Non_Null properly
1546 -- reflects the state of the entity after the assignment
1548 if Is_Access_Type (Typ)
1549 and then Is_Entity_Name (Lhs)
1550 and then Known_Non_Null (Rhs)
1551 and then Safe_To_Capture_Value (N, Entity (Lhs))
1553 Set_Is_Known_Non_Null (Entity (Lhs), Known_Non_Null (Rhs));
1556 -- Case of assignment to a bit packed array element
1558 if Nkind (Lhs) = N_Indexed_Component
1559 and then Is_Bit_Packed_Array (Etype (Prefix (Lhs)))
1561 Expand_Bit_Packed_Element_Set (N);
1564 -- Case of tagged type assignment
1566 elsif Is_Tagged_Type (Typ)
1567 or else (Controlled_Type (Typ) and then not Is_Array_Type (Typ))
1569 Tagged_Case : declare
1570 L : List_Id := No_List;
1571 Expand_Ctrl_Actions : constant Boolean := not No_Ctrl_Actions (N);
1574 -- In the controlled case, we need to make sure that function
1575 -- calls are evaluated before finalizing the target. In all
1576 -- cases, it makes the expansion easier if the side-effects
1577 -- are removed first.
1579 Remove_Side_Effects (Lhs);
1580 Remove_Side_Effects (Rhs);
1582 -- Avoid recursion in the mechanism
1586 -- If dispatching assignment, we need to dispatch to _assign
1588 if Is_Class_Wide_Type (Typ)
1590 -- If the type is tagged, we may as well use the predefined
1591 -- primitive assignment. This avoids inlining a lot of code
1592 -- and in the class-wide case, the assignment is replaced by
1593 -- a dispatch call to _assign. Note that this cannot be done
1594 -- when discriminant checks are locally suppressed (as in
1595 -- extension aggregate expansions) because otherwise the
1596 -- discriminant check will be performed within the _assign
1599 or else (Is_Tagged_Type (Typ)
1600 and then Chars (Current_Scope) /= Name_uAssign
1601 and then Expand_Ctrl_Actions
1602 and then not Discriminant_Checks_Suppressed (Empty))
1604 -- Fetch the primitive op _assign and proper type to call
1605 -- it. Because of possible conflits between private and
1606 -- full view the proper type is fetched directly from the
1607 -- operation profile.
1610 Op : constant Entity_Id :=
1611 Find_Prim_Op (Typ, Name_uAssign);
1612 F_Typ : Entity_Id := Etype (First_Formal (Op));
1615 -- If the assignment is dispatching, make sure to use the
1616 -- ??? where is rest of this comment ???
1618 if Is_Class_Wide_Type (Typ) then
1619 F_Typ := Class_Wide_Type (F_Typ);
1623 Make_Procedure_Call_Statement (Loc,
1624 Name => New_Reference_To (Op, Loc),
1625 Parameter_Associations => New_List (
1626 Unchecked_Convert_To (F_Typ, Duplicate_Subexpr (Lhs)),
1627 Unchecked_Convert_To (F_Typ,
1628 Duplicate_Subexpr (Rhs)))));
1632 L := Make_Tag_Ctrl_Assignment (N);
1634 -- We can't afford to have destructive Finalization Actions
1635 -- in the Self assignment case, so if the target and the
1636 -- source are not obviously different, code is generated to
1637 -- avoid the self assignment case
1639 -- if lhs'address /= rhs'address then
1640 -- <code for controlled and/or tagged assignment>
1643 if not Statically_Different (Lhs, Rhs)
1644 and then Expand_Ctrl_Actions
1647 Make_Implicit_If_Statement (N,
1651 Make_Attribute_Reference (Loc,
1652 Prefix => Duplicate_Subexpr (Lhs),
1653 Attribute_Name => Name_Address),
1656 Make_Attribute_Reference (Loc,
1657 Prefix => Duplicate_Subexpr (Rhs),
1658 Attribute_Name => Name_Address)),
1660 Then_Statements => L));
1663 -- We need to set up an exception handler for implementing
1664 -- 7.6.1 (18). The remaining adjustments are tackled by the
1665 -- implementation of adjust for record_controllers (see
1668 -- This is skipped if we have no finalization
1670 if Expand_Ctrl_Actions
1671 and then not Restriction_Active (No_Finalization)
1674 Make_Block_Statement (Loc,
1675 Handled_Statement_Sequence =>
1676 Make_Handled_Sequence_Of_Statements (Loc,
1678 Exception_Handlers => New_List (
1679 Make_Exception_Handler (Loc,
1680 Exception_Choices =>
1681 New_List (Make_Others_Choice (Loc)),
1682 Statements => New_List (
1683 Make_Raise_Program_Error (Loc,
1685 PE_Finalize_Raised_Exception)
1691 Make_Block_Statement (Loc,
1692 Handled_Statement_Sequence =>
1693 Make_Handled_Sequence_Of_Statements (Loc, Statements => L)));
1695 -- If no restrictions on aborts, protect the whole assignement
1696 -- for controlled objects as per 9.8(11)
1698 if Controlled_Type (Typ)
1699 and then Expand_Ctrl_Actions
1700 and then Abort_Allowed
1703 Blk : constant Entity_Id :=
1704 New_Internal_Entity (
1705 E_Block, Current_Scope, Sloc (N), 'B');
1708 Set_Scope (Blk, Current_Scope);
1709 Set_Etype (Blk, Standard_Void_Type);
1710 Set_Identifier (N, New_Occurrence_Of (Blk, Sloc (N)));
1712 Prepend_To (L, Build_Runtime_Call (Loc, RE_Abort_Defer));
1713 Set_At_End_Proc (Handled_Statement_Sequence (N),
1714 New_Occurrence_Of (RTE (RE_Abort_Undefer_Direct), Loc));
1715 Expand_At_End_Handler
1716 (Handled_Statement_Sequence (N), Blk);
1726 elsif Is_Array_Type (Typ) then
1728 Actual_Rhs : Node_Id := Rhs;
1731 while Nkind (Actual_Rhs) = N_Type_Conversion
1733 Nkind (Actual_Rhs) = N_Qualified_Expression
1735 Actual_Rhs := Expression (Actual_Rhs);
1738 Expand_Assign_Array (N, Actual_Rhs);
1744 elsif Is_Record_Type (Typ) then
1745 Expand_Assign_Record (N);
1748 -- Scalar types. This is where we perform the processing related
1749 -- to the requirements of (RM 13.9.1(9-11)) concerning the handling
1750 -- of invalid scalar values.
1752 elsif Is_Scalar_Type (Typ) then
1754 -- Case where right side is known valid
1756 if Expr_Known_Valid (Rhs) then
1758 -- Here the right side is valid, so it is fine. The case to
1759 -- deal with is when the left side is a local variable reference
1760 -- whose value is not currently known to be valid. If this is
1761 -- the case, and the assignment appears in an unconditional
1762 -- context, then we can mark the left side as now being valid.
1764 if Is_Local_Variable_Reference (Lhs)
1765 and then not Is_Known_Valid (Entity (Lhs))
1766 and then In_Unconditional_Context (N)
1768 Set_Is_Known_Valid (Entity (Lhs), True);
1771 -- Case where right side may be invalid in the sense of the RM
1772 -- reference above. The RM does not require that we check for
1773 -- the validity on an assignment, but it does require that the
1774 -- assignment of an invalid value not cause erroneous behavior.
1776 -- The general approach in GNAT is to use the Is_Known_Valid flag
1777 -- to avoid the need for validity checking on assignments. However
1778 -- in some cases, we have to do validity checking in order to make
1779 -- sure that the setting of this flag is correct.
1782 -- Validate right side if we are validating copies
1784 if Validity_Checks_On
1785 and then Validity_Check_Copies
1789 -- We can propagate this to the left side where appropriate
1791 if Is_Local_Variable_Reference (Lhs)
1792 and then not Is_Known_Valid (Entity (Lhs))
1793 and then In_Unconditional_Context (N)
1795 Set_Is_Known_Valid (Entity (Lhs), True);
1798 -- Otherwise check to see what should be done
1800 -- If left side is a local variable, then we just set its
1801 -- flag to indicate that its value may no longer be valid,
1802 -- since we are copying a potentially invalid value.
1804 elsif Is_Local_Variable_Reference (Lhs) then
1805 Set_Is_Known_Valid (Entity (Lhs), False);
1807 -- Check for case of a nonlocal variable on the left side
1808 -- which is currently known to be valid. In this case, we
1809 -- simply ensure that the right side is valid. We only play
1810 -- the game of copying validity status for local variables,
1811 -- since we are doing this statically, not by tracing the
1814 elsif Is_Entity_Name (Lhs)
1815 and then Is_Known_Valid (Entity (Lhs))
1817 -- Note that the Ensure_Valid call is ignored if the
1818 -- Validity_Checking mode is set to none so we do not
1819 -- need to worry about that case here.
1823 -- In all other cases, we can safely copy an invalid value
1824 -- without worrying about the status of the left side. Since
1825 -- it is not a variable reference it will not be considered
1826 -- as being known to be valid in any case.
1834 -- Defend against invalid subscripts on left side if we are in
1835 -- standard validity checking mode. No need to do this if we
1836 -- are checking all subscripts.
1838 if Validity_Checks_On
1839 and then Validity_Check_Default
1840 and then not Validity_Check_Subscripts
1842 Check_Valid_Lvalue_Subscripts (Lhs);
1846 when RE_Not_Available =>
1848 end Expand_N_Assignment_Statement;
1850 ------------------------------
1851 -- Expand_N_Block_Statement --
1852 ------------------------------
1854 -- Encode entity names defined in block statement
1856 procedure Expand_N_Block_Statement (N : Node_Id) is
1858 Qualify_Entity_Names (N);
1859 end Expand_N_Block_Statement;
1861 -----------------------------
1862 -- Expand_N_Case_Statement --
1863 -----------------------------
1865 procedure Expand_N_Case_Statement (N : Node_Id) is
1866 Loc : constant Source_Ptr := Sloc (N);
1867 Expr : constant Node_Id := Expression (N);
1875 -- Check for the situation where we know at compile time which
1876 -- branch will be taken
1878 if Compile_Time_Known_Value (Expr) then
1879 Alt := Find_Static_Alternative (N);
1881 -- Move the statements from this alternative after the case
1882 -- statement. They are already analyzed, so will be skipped
1885 Insert_List_After (N, Statements (Alt));
1887 -- That leaves the case statement as a shell. The alternative
1888 -- that will be executed is reset to a null list. So now we can
1889 -- kill the entire case statement.
1891 Kill_Dead_Code (Expression (N));
1892 Kill_Dead_Code (Alternatives (N));
1893 Rewrite (N, Make_Null_Statement (Loc));
1897 -- Here if the choice is not determined at compile time
1900 Last_Alt : constant Node_Id := Last (Alternatives (N));
1902 Others_Present : Boolean;
1903 Others_Node : Node_Id;
1905 Then_Stms : List_Id;
1906 Else_Stms : List_Id;
1909 if Nkind (First (Discrete_Choices (Last_Alt))) = N_Others_Choice then
1910 Others_Present := True;
1911 Others_Node := Last_Alt;
1913 Others_Present := False;
1916 -- First step is to worry about possible invalid argument. The RM
1917 -- requires (RM 5.4(13)) that if the result is invalid (e.g. it is
1918 -- outside the base range), then Constraint_Error must be raised.
1920 -- Case of validity check required (validity checks are on, the
1921 -- expression is not known to be valid, and the case statement
1922 -- comes from source -- no need to validity check internally
1923 -- generated case statements).
1925 if Validity_Check_Default then
1926 Ensure_Valid (Expr);
1929 -- If there is only a single alternative, just replace it with
1930 -- the sequence of statements since obviously that is what is
1931 -- going to be executed in all cases.
1933 Len := List_Length (Alternatives (N));
1936 -- We still need to evaluate the expression if it has any
1939 Remove_Side_Effects (Expression (N));
1941 Insert_List_After (N, Statements (First (Alternatives (N))));
1943 -- That leaves the case statement as a shell. The alternative
1944 -- that will be executed is reset to a null list. So now we can
1945 -- kill the entire case statement.
1947 Kill_Dead_Code (Expression (N));
1948 Rewrite (N, Make_Null_Statement (Loc));
1952 -- An optimization. If there are only two alternatives, and only
1953 -- a single choice, then rewrite the whole case statement as an
1954 -- if statement, since this can result in susbequent optimizations.
1955 -- This helps not only with case statements in the source of a
1956 -- simple form, but also with generated code (discriminant check
1957 -- functions in particular)
1960 Chlist := Discrete_Choices (First (Alternatives (N)));
1962 if List_Length (Chlist) = 1 then
1963 Choice := First (Chlist);
1965 Then_Stms := Statements (First (Alternatives (N)));
1966 Else_Stms := Statements (Last (Alternatives (N)));
1968 -- For TRUE, generate "expression", not expression = true
1970 if Nkind (Choice) = N_Identifier
1971 and then Entity (Choice) = Standard_True
1973 Cond := Expression (N);
1975 -- For FALSE, generate "expression" and switch then/else
1977 elsif Nkind (Choice) = N_Identifier
1978 and then Entity (Choice) = Standard_False
1980 Cond := Expression (N);
1981 Else_Stms := Statements (First (Alternatives (N)));
1982 Then_Stms := Statements (Last (Alternatives (N)));
1984 -- For a range, generate "expression in range"
1986 elsif Nkind (Choice) = N_Range
1987 or else (Nkind (Choice) = N_Attribute_Reference
1988 and then Attribute_Name (Choice) = Name_Range)
1989 or else (Is_Entity_Name (Choice)
1990 and then Is_Type (Entity (Choice)))
1991 or else Nkind (Choice) = N_Subtype_Indication
1995 Left_Opnd => Expression (N),
1996 Right_Opnd => Relocate_Node (Choice));
1998 -- For any other subexpression "expression = value"
2003 Left_Opnd => Expression (N),
2004 Right_Opnd => Relocate_Node (Choice));
2007 -- Now rewrite the case as an IF
2010 Make_If_Statement (Loc,
2012 Then_Statements => Then_Stms,
2013 Else_Statements => Else_Stms));
2019 -- If the last alternative is not an Others choice, replace it
2020 -- with an N_Others_Choice. Note that we do not bother to call
2021 -- Analyze on the modified case statement, since it's only effect
2022 -- would be to compute the contents of the Others_Discrete_Choices
2023 -- which is not needed by the back end anyway.
2025 -- The reason we do this is that the back end always needs some
2026 -- default for a switch, so if we have not supplied one in the
2027 -- processing above for validity checking, then we need to
2030 if not Others_Present then
2031 Others_Node := Make_Others_Choice (Sloc (Last_Alt));
2032 Set_Others_Discrete_Choices
2033 (Others_Node, Discrete_Choices (Last_Alt));
2034 Set_Discrete_Choices (Last_Alt, New_List (Others_Node));
2037 end Expand_N_Case_Statement;
2039 -----------------------------
2040 -- Expand_N_Exit_Statement --
2041 -----------------------------
2043 -- The only processing required is to deal with a possible C/Fortran
2044 -- boolean value used as the condition for the exit statement.
2046 procedure Expand_N_Exit_Statement (N : Node_Id) is
2048 Adjust_Condition (Condition (N));
2049 end Expand_N_Exit_Statement;
2051 -----------------------------
2052 -- Expand_N_Goto_Statement --
2053 -----------------------------
2055 -- Add poll before goto if polling active
2057 procedure Expand_N_Goto_Statement (N : Node_Id) is
2059 Generate_Poll_Call (N);
2060 end Expand_N_Goto_Statement;
2062 ---------------------------
2063 -- Expand_N_If_Statement --
2064 ---------------------------
2066 -- First we deal with the case of C and Fortran convention boolean
2067 -- values, with zero/non-zero semantics.
2069 -- Second, we deal with the obvious rewriting for the cases where the
2070 -- condition of the IF is known at compile time to be True or False.
2072 -- Third, we remove elsif parts which have non-empty Condition_Actions
2073 -- and rewrite as independent if statements. For example:
2084 -- <<condition actions of y>>
2090 -- This rewriting is needed if at least one elsif part has a non-empty
2091 -- Condition_Actions list. We also do the same processing if there is
2092 -- a constant condition in an elsif part (in conjunction with the first
2093 -- processing step mentioned above, for the recursive call made to deal
2094 -- with the created inner if, this deals with properly optimizing the
2095 -- cases of constant elsif conditions).
2097 procedure Expand_N_If_Statement (N : Node_Id) is
2098 Loc : constant Source_Ptr := Sloc (N);
2104 Adjust_Condition (Condition (N));
2106 -- The following loop deals with constant conditions for the IF. We
2107 -- need a loop because as we eliminate False conditions, we grab the
2108 -- first elsif condition and use it as the primary condition.
2110 while Compile_Time_Known_Value (Condition (N)) loop
2112 -- If condition is True, we can simply rewrite the if statement
2113 -- now by replacing it by the series of then statements.
2115 if Is_True (Expr_Value (Condition (N))) then
2117 -- All the else parts can be killed
2119 Kill_Dead_Code (Elsif_Parts (N));
2120 Kill_Dead_Code (Else_Statements (N));
2122 Hed := Remove_Head (Then_Statements (N));
2123 Insert_List_After (N, Then_Statements (N));
2127 -- If condition is False, then we can delete the condition and
2128 -- the Then statements
2131 -- We do not delete the condition if constant condition
2132 -- warnings are enabled, since otherwise we end up deleting
2133 -- the desired warning. Of course the backend will get rid
2134 -- of this True/False test anyway, so nothing is lost here.
2136 if not Constant_Condition_Warnings then
2137 Kill_Dead_Code (Condition (N));
2140 Kill_Dead_Code (Then_Statements (N));
2142 -- If there are no elsif statements, then we simply replace
2143 -- the entire if statement by the sequence of else statements.
2145 if No (Elsif_Parts (N)) then
2147 if No (Else_Statements (N))
2148 or else Is_Empty_List (Else_Statements (N))
2151 Make_Null_Statement (Sloc (N)));
2154 Hed := Remove_Head (Else_Statements (N));
2155 Insert_List_After (N, Else_Statements (N));
2161 -- If there are elsif statements, the first of them becomes
2162 -- the if/then section of the rebuilt if statement This is
2163 -- the case where we loop to reprocess this copied condition.
2166 Hed := Remove_Head (Elsif_Parts (N));
2167 Insert_Actions (N, Condition_Actions (Hed));
2168 Set_Condition (N, Condition (Hed));
2169 Set_Then_Statements (N, Then_Statements (Hed));
2171 if Is_Empty_List (Elsif_Parts (N)) then
2172 Set_Elsif_Parts (N, No_List);
2178 -- Loop through elsif parts, dealing with constant conditions and
2179 -- possible expression actions that are present.
2181 if Present (Elsif_Parts (N)) then
2182 E := First (Elsif_Parts (N));
2183 while Present (E) loop
2184 Adjust_Condition (Condition (E));
2186 -- If there are condition actions, then we rewrite the if
2187 -- statement as indicated above. We also do the same rewrite
2188 -- if the condition is True or False. The further processing
2189 -- of this constant condition is then done by the recursive
2190 -- call to expand the newly created if statement
2192 if Present (Condition_Actions (E))
2193 or else Compile_Time_Known_Value (Condition (E))
2195 -- Note this is not an implicit if statement, since it is
2196 -- part of an explicit if statement in the source (or of an
2197 -- implicit if statement that has already been tested).
2200 Make_If_Statement (Sloc (E),
2201 Condition => Condition (E),
2202 Then_Statements => Then_Statements (E),
2203 Elsif_Parts => No_List,
2204 Else_Statements => Else_Statements (N));
2206 -- Elsif parts for new if come from remaining elsif's of parent
2208 while Present (Next (E)) loop
2209 if No (Elsif_Parts (New_If)) then
2210 Set_Elsif_Parts (New_If, New_List);
2213 Append (Remove_Next (E), Elsif_Parts (New_If));
2216 Set_Else_Statements (N, New_List (New_If));
2218 if Present (Condition_Actions (E)) then
2219 Insert_List_Before (New_If, Condition_Actions (E));
2224 if Is_Empty_List (Elsif_Parts (N)) then
2225 Set_Elsif_Parts (N, No_List);
2231 -- No special processing for that elsif part, move to next
2239 -- Some more optimizations applicable if we still have an IF statement
2241 if Nkind (N) /= N_If_Statement then
2245 -- Another optimization, special cases that can be simplified
2247 -- if expression then
2253 -- can be changed to:
2255 -- return expression;
2259 -- if expression then
2265 -- can be changed to:
2267 -- return not (expression);
2269 if Nkind (N) = N_If_Statement
2270 and then No (Elsif_Parts (N))
2271 and then Present (Else_Statements (N))
2272 and then List_Length (Then_Statements (N)) = 1
2273 and then List_Length (Else_Statements (N)) = 1
2276 Then_Stm : constant Node_Id := First (Then_Statements (N));
2277 Else_Stm : constant Node_Id := First (Else_Statements (N));
2280 if Nkind (Then_Stm) = N_Return_Statement
2282 Nkind (Else_Stm) = N_Return_Statement
2285 Then_Expr : constant Node_Id := Expression (Then_Stm);
2286 Else_Expr : constant Node_Id := Expression (Else_Stm);
2289 if Nkind (Then_Expr) = N_Identifier
2291 Nkind (Else_Expr) = N_Identifier
2293 if Entity (Then_Expr) = Standard_True
2294 and then Entity (Else_Expr) = Standard_False
2297 Make_Return_Statement (Loc,
2298 Expression => Relocate_Node (Condition (N))));
2302 elsif Entity (Then_Expr) = Standard_False
2303 and then Entity (Else_Expr) = Standard_True
2306 Make_Return_Statement (Loc,
2309 Right_Opnd => Relocate_Node (Condition (N)))));
2318 end Expand_N_If_Statement;
2320 -----------------------------
2321 -- Expand_N_Loop_Statement --
2322 -----------------------------
2324 -- 1. Deal with while condition for C/Fortran boolean
2325 -- 2. Deal with loops with a non-standard enumeration type range
2326 -- 3. Deal with while loops where Condition_Actions is set
2327 -- 4. Insert polling call if required
2329 procedure Expand_N_Loop_Statement (N : Node_Id) is
2330 Loc : constant Source_Ptr := Sloc (N);
2331 Isc : constant Node_Id := Iteration_Scheme (N);
2334 if Present (Isc) then
2335 Adjust_Condition (Condition (Isc));
2338 if Is_Non_Empty_List (Statements (N)) then
2339 Generate_Poll_Call (First (Statements (N)));
2346 -- Handle the case where we have a for loop with the range type being
2347 -- an enumeration type with non-standard representation. In this case
2350 -- for x in [reverse] a .. b loop
2356 -- for xP in [reverse] integer
2357 -- range etype'Pos (a) .. etype'Pos (b) loop
2359 -- x : constant etype := Pos_To_Rep (xP);
2365 if Present (Loop_Parameter_Specification (Isc)) then
2367 LPS : constant Node_Id := Loop_Parameter_Specification (Isc);
2368 Loop_Id : constant Entity_Id := Defining_Identifier (LPS);
2369 Ltype : constant Entity_Id := Etype (Loop_Id);
2370 Btype : constant Entity_Id := Base_Type (Ltype);
2375 if not Is_Enumeration_Type (Btype)
2376 or else No (Enum_Pos_To_Rep (Btype))
2382 Make_Defining_Identifier (Loc,
2383 Chars => New_External_Name (Chars (Loop_Id), 'P'));
2385 -- If the type has a contiguous representation, successive
2386 -- values can be generated as offsets from the first literal.
2388 if Has_Contiguous_Rep (Btype) then
2390 Unchecked_Convert_To (Btype,
2393 Make_Integer_Literal (Loc,
2394 Enumeration_Rep (First_Literal (Btype))),
2395 Right_Opnd => New_Reference_To (New_Id, Loc)));
2397 -- Use the constructed array Enum_Pos_To_Rep.
2400 Make_Indexed_Component (Loc,
2401 Prefix => New_Reference_To (Enum_Pos_To_Rep (Btype), Loc),
2402 Expressions => New_List (New_Reference_To (New_Id, Loc)));
2406 Make_Loop_Statement (Loc,
2407 Identifier => Identifier (N),
2410 Make_Iteration_Scheme (Loc,
2411 Loop_Parameter_Specification =>
2412 Make_Loop_Parameter_Specification (Loc,
2413 Defining_Identifier => New_Id,
2414 Reverse_Present => Reverse_Present (LPS),
2416 Discrete_Subtype_Definition =>
2417 Make_Subtype_Indication (Loc,
2420 New_Reference_To (Standard_Natural, Loc),
2423 Make_Range_Constraint (Loc,
2428 Make_Attribute_Reference (Loc,
2430 New_Reference_To (Btype, Loc),
2432 Attribute_Name => Name_Pos,
2434 Expressions => New_List (
2436 (Type_Low_Bound (Ltype)))),
2439 Make_Attribute_Reference (Loc,
2441 New_Reference_To (Btype, Loc),
2443 Attribute_Name => Name_Pos,
2445 Expressions => New_List (
2447 (Type_High_Bound (Ltype))))))))),
2449 Statements => New_List (
2450 Make_Block_Statement (Loc,
2451 Declarations => New_List (
2452 Make_Object_Declaration (Loc,
2453 Defining_Identifier => Loop_Id,
2454 Constant_Present => True,
2455 Object_Definition => New_Reference_To (Ltype, Loc),
2456 Expression => Expr)),
2458 Handled_Statement_Sequence =>
2459 Make_Handled_Sequence_Of_Statements (Loc,
2460 Statements => Statements (N)))),
2462 End_Label => End_Label (N)));
2466 -- Second case, if we have a while loop with Condition_Actions set,
2467 -- then we change it into a plain loop:
2476 -- <<condition actions>>
2482 and then Present (Condition_Actions (Isc))
2489 Make_Exit_Statement (Sloc (Condition (Isc)),
2491 Make_Op_Not (Sloc (Condition (Isc)),
2492 Right_Opnd => Condition (Isc)));
2494 Prepend (ES, Statements (N));
2495 Insert_List_Before (ES, Condition_Actions (Isc));
2497 -- This is not an implicit loop, since it is generated in
2498 -- response to the loop statement being processed. If this
2499 -- is itself implicit, the restriction has already been
2500 -- checked. If not, it is an explicit loop.
2503 Make_Loop_Statement (Sloc (N),
2504 Identifier => Identifier (N),
2505 Statements => Statements (N),
2506 End_Label => End_Label (N)));
2511 end Expand_N_Loop_Statement;
2513 -------------------------------
2514 -- Expand_N_Return_Statement --
2515 -------------------------------
2517 procedure Expand_N_Return_Statement (N : Node_Id) is
2518 Loc : constant Source_Ptr := Sloc (N);
2519 Exp : constant Node_Id := Expression (N);
2523 Scope_Id : Entity_Id;
2527 Goto_Stat : Node_Id;
2530 Return_Type : Entity_Id;
2531 Result_Exp : Node_Id;
2532 Result_Id : Entity_Id;
2533 Result_Obj : Node_Id;
2536 -- Case where returned expression is present
2538 if Present (Exp) then
2540 -- Always normalize C/Fortran boolean result. This is not always
2541 -- necessary, but it seems a good idea to minimize the passing
2542 -- around of non-normalized values, and in any case this handles
2543 -- the processing of barrier functions for protected types, which
2544 -- turn the condition into a return statement.
2546 Exptyp := Etype (Exp);
2548 if Is_Boolean_Type (Exptyp)
2549 and then Nonzero_Is_True (Exptyp)
2551 Adjust_Condition (Exp);
2552 Adjust_Result_Type (Exp, Exptyp);
2555 -- Do validity check if enabled for returns
2557 if Validity_Checks_On
2558 and then Validity_Check_Returns
2564 -- Find relevant enclosing scope from which return is returning
2566 Cur_Idx := Scope_Stack.Last;
2568 Scope_Id := Scope_Stack.Table (Cur_Idx).Entity;
2570 if Ekind (Scope_Id) /= E_Block
2571 and then Ekind (Scope_Id) /= E_Loop
2576 Cur_Idx := Cur_Idx - 1;
2577 pragma Assert (Cur_Idx >= 0);
2582 Kind := Ekind (Scope_Id);
2584 -- If it is a return from procedures do no extra steps.
2586 if Kind = E_Procedure or else Kind = E_Generic_Procedure then
2590 pragma Assert (Is_Entry (Scope_Id));
2592 -- Look at the enclosing block to see whether the return is from
2593 -- an accept statement or an entry body.
2595 for J in reverse 0 .. Cur_Idx loop
2596 Scope_Id := Scope_Stack.Table (J).Entity;
2597 exit when Is_Concurrent_Type (Scope_Id);
2600 -- If it is a return from accept statement it should be expanded
2601 -- as a call to RTS Complete_Rendezvous and a goto to the end of
2604 -- (cf : Expand_N_Accept_Statement, Expand_N_Selective_Accept,
2605 -- Expand_N_Accept_Alternative in exp_ch9.adb)
2607 if Is_Task_Type (Scope_Id) then
2609 Call := (Make_Procedure_Call_Statement (Loc,
2610 Name => New_Reference_To
2611 (RTE (RE_Complete_Rendezvous), Loc)));
2612 Insert_Before (N, Call);
2613 -- why not insert actions here???
2616 Acc_Stat := Parent (N);
2617 while Nkind (Acc_Stat) /= N_Accept_Statement loop
2618 Acc_Stat := Parent (Acc_Stat);
2621 Lab_Node := Last (Statements
2622 (Handled_Statement_Sequence (Acc_Stat)));
2624 Goto_Stat := Make_Goto_Statement (Loc,
2625 Name => New_Occurrence_Of
2626 (Entity (Identifier (Lab_Node)), Loc));
2628 Set_Analyzed (Goto_Stat);
2630 Rewrite (N, Goto_Stat);
2633 -- If it is a return from an entry body, put a Complete_Entry_Body
2634 -- call in front of the return.
2636 elsif Is_Protected_Type (Scope_Id) then
2639 Make_Procedure_Call_Statement (Loc,
2640 Name => New_Reference_To
2641 (RTE (RE_Complete_Entry_Body), Loc),
2642 Parameter_Associations => New_List
2643 (Make_Attribute_Reference (Loc,
2647 (Corresponding_Body (Parent (Scope_Id))),
2649 Attribute_Name => Name_Unchecked_Access)));
2651 Insert_Before (N, Call);
2660 Return_Type := Etype (Scope_Id);
2661 Utyp := Underlying_Type (Return_Type);
2663 -- Check the result expression of a scalar function against
2664 -- the subtype of the function by inserting a conversion.
2665 -- This conversion must eventually be performed for other
2666 -- classes of types, but for now it's only done for scalars.
2669 if Is_Scalar_Type (T) then
2670 Rewrite (Exp, Convert_To (Return_Type, Exp));
2674 -- Implement the rules of 6.5(8-10), which require a tag check in
2675 -- the case of a limited tagged return type, and tag reassignment
2676 -- for nonlimited tagged results. These actions are needed when
2677 -- the return type is a specific tagged type and the result
2678 -- expression is a conversion or a formal parameter, because in
2679 -- that case the tag of the expression might differ from the tag
2680 -- of the specific result type.
2682 if Is_Tagged_Type (Utyp)
2683 and then not Is_Class_Wide_Type (Utyp)
2684 and then (Nkind (Exp) = N_Type_Conversion
2685 or else Nkind (Exp) = N_Unchecked_Type_Conversion
2686 or else (Is_Entity_Name (Exp)
2687 and then Ekind (Entity (Exp)) in Formal_Kind))
2689 -- When the return type is limited, perform a check that the
2690 -- tag of the result is the same as the tag of the return type.
2692 if Is_Limited_Type (Return_Type) then
2694 Make_Raise_Constraint_Error (Loc,
2698 Make_Selected_Component (Loc,
2699 Prefix => Duplicate_Subexpr (Exp),
2701 New_Reference_To (Tag_Component (Utyp), Loc)),
2703 Unchecked_Convert_To (RTE (RE_Tag),
2705 (Access_Disp_Table (Base_Type (Utyp)), Loc))),
2706 Reason => CE_Tag_Check_Failed));
2708 -- If the result type is a specific nonlimited tagged type,
2709 -- then we have to ensure that the tag of the result is that
2710 -- of the result type. This is handled by making a copy of the
2711 -- expression in the case where it might have a different tag,
2712 -- namely when the expression is a conversion or a formal
2713 -- parameter. We create a new object of the result type and
2714 -- initialize it from the expression, which will implicitly
2715 -- force the tag to be set appropriately.
2719 Make_Defining_Identifier (Loc, New_Internal_Name ('R'));
2720 Result_Exp := New_Reference_To (Result_Id, Loc);
2723 Make_Object_Declaration (Loc,
2724 Defining_Identifier => Result_Id,
2725 Object_Definition => New_Reference_To (Return_Type, Loc),
2726 Constant_Present => True,
2727 Expression => Relocate_Node (Exp));
2729 Set_Assignment_OK (Result_Obj);
2730 Insert_Action (Exp, Result_Obj);
2732 Rewrite (Exp, Result_Exp);
2733 Analyze_And_Resolve (Exp, Return_Type);
2737 -- Deal with returning variable length objects and controlled types
2739 -- Nothing to do if we are returning by reference, or this is not
2740 -- a type that requires special processing (indicated by the fact
2741 -- that it requires a cleanup scope for the secondary stack case)
2743 if Is_Return_By_Reference_Type (T)
2744 or else not Requires_Transient_Scope (Return_Type)
2748 -- Case of secondary stack not used
2750 elsif Function_Returns_With_DSP (Scope_Id) then
2752 -- Here what we need to do is to always return by reference, since
2753 -- we will return with the stack pointer depressed. We may need to
2754 -- do a copy to a local temporary before doing this return.
2756 No_Secondary_Stack_Case : declare
2757 Local_Copy_Required : Boolean := False;
2758 -- Set to True if a local copy is required
2760 Copy_Ent : Entity_Id;
2761 -- Used for the target entity if a copy is required
2764 -- Declaration used to create copy if needed
2766 procedure Test_Copy_Required (Expr : Node_Id);
2767 -- Determines if Expr represents a return value for which a
2768 -- copy is required. More specifically, a copy is not required
2769 -- if Expr represents an object or component of an object that
2770 -- is either in the local subprogram frame, or is constant.
2771 -- If a copy is required, then Local_Copy_Required is set True.
2773 ------------------------
2774 -- Test_Copy_Required --
2775 ------------------------
2777 procedure Test_Copy_Required (Expr : Node_Id) is
2781 -- If component, test prefix (object containing component)
2783 if Nkind (Expr) = N_Indexed_Component
2785 Nkind (Expr) = N_Selected_Component
2787 Test_Copy_Required (Prefix (Expr));
2790 -- See if we have an entity name
2792 elsif Is_Entity_Name (Expr) then
2793 Ent := Entity (Expr);
2795 -- Constant entity is always OK, no copy required
2797 if Ekind (Ent) = E_Constant then
2800 -- No copy required for local variable
2802 elsif Ekind (Ent) = E_Variable
2803 and then Scope (Ent) = Current_Subprogram
2809 -- All other cases require a copy
2811 Local_Copy_Required := True;
2812 end Test_Copy_Required;
2814 -- Start of processing for No_Secondary_Stack_Case
2817 -- No copy needed if result is from a function call.
2818 -- In this case the result is already being returned by
2819 -- reference with the stack pointer depressed.
2821 -- To make up for a gcc 2.8.1 deficiency (???), we perform
2822 -- the copy for array types if the constrained status of the
2823 -- target type is different from that of the expression.
2825 if Requires_Transient_Scope (T)
2827 (not Is_Array_Type (T)
2828 or else Is_Constrained (T) = Is_Constrained (Return_Type)
2829 or else Controlled_Type (T))
2830 and then Nkind (Exp) = N_Function_Call
2834 -- We always need a local copy for a controlled type, since
2835 -- we are required to finalize the local value before return.
2836 -- The copy will automatically include the required finalize.
2837 -- Moreover, gigi cannot make this copy, since we need special
2838 -- processing to ensure proper behavior for finalization.
2840 -- Note: the reason we are returning with a depressed stack
2841 -- pointer in the controlled case (even if the type involved
2842 -- is constrained) is that we must make a local copy to deal
2843 -- properly with the requirement that the local result be
2846 elsif Controlled_Type (Utyp) then
2848 Make_Defining_Identifier (Loc,
2849 Chars => New_Internal_Name ('R'));
2851 -- Build declaration to do the copy, and insert it, setting
2852 -- Assignment_OK, because we may be copying a limited type.
2853 -- In addition we set the special flag to inhibit finalize
2854 -- attachment if this is a controlled type (since this attach
2855 -- must be done by the caller, otherwise if we attach it here
2856 -- we will finalize the returned result prematurely).
2859 Make_Object_Declaration (Loc,
2860 Defining_Identifier => Copy_Ent,
2861 Object_Definition => New_Occurrence_Of (Return_Type, Loc),
2862 Expression => Relocate_Node (Exp));
2864 Set_Assignment_OK (Decl);
2865 Set_Delay_Finalize_Attach (Decl);
2866 Insert_Action (N, Decl);
2868 -- Now the actual return uses the copied value
2870 Rewrite (Exp, New_Occurrence_Of (Copy_Ent, Loc));
2871 Analyze_And_Resolve (Exp, Return_Type);
2873 -- Since we have made the copy, gigi does not have to, so
2874 -- we set the By_Ref flag to prevent another copy being made.
2878 -- Non-controlled cases
2881 Test_Copy_Required (Exp);
2883 -- If a local copy is required, then gigi will make the
2884 -- copy, otherwise, we can return the result directly,
2885 -- so set By_Ref to suppress the gigi copy.
2887 if not Local_Copy_Required then
2891 end No_Secondary_Stack_Case;
2893 -- Here if secondary stack is used
2896 -- Make sure that no surrounding block will reclaim the
2897 -- secondary-stack on which we are going to put the result.
2898 -- Not only may this introduce secondary stack leaks but worse,
2899 -- if the reclamation is done too early, then the result we are
2900 -- returning may get clobbered. See example in 7417-003.
2903 S : Entity_Id := Current_Scope;
2906 while Ekind (S) = E_Block or else Ekind (S) = E_Loop loop
2907 Set_Sec_Stack_Needed_For_Return (S, True);
2908 S := Enclosing_Dynamic_Scope (S);
2912 -- Optimize the case where the result is a function call. In this
2913 -- case either the result is already on the secondary stack, or is
2914 -- already being returned with the stack pointer depressed and no
2915 -- further processing is required except to set the By_Ref flag to
2916 -- ensure that gigi does not attempt an extra unnecessary copy.
2917 -- (actually not just unnecessary but harmfully wrong in the case
2918 -- of a controlled type, where gigi does not know how to do a copy).
2919 -- To make up for a gcc 2.8.1 deficiency (???), we perform
2920 -- the copy for array types if the constrained status of the
2921 -- target type is different from that of the expression.
2923 if Requires_Transient_Scope (T)
2925 (not Is_Array_Type (T)
2926 or else Is_Constrained (T) = Is_Constrained (Return_Type)
2927 or else Controlled_Type (T))
2928 and then Nkind (Exp) = N_Function_Call
2932 -- For controlled types, do the allocation on the sec-stack
2933 -- manually in order to call adjust at the right time
2934 -- type Anon1 is access Return_Type;
2935 -- for Anon1'Storage_pool use ss_pool;
2936 -- Anon2 : anon1 := new Return_Type'(expr);
2937 -- return Anon2.all;
2939 elsif Controlled_Type (Utyp) then
2941 Loc : constant Source_Ptr := Sloc (N);
2942 Temp : constant Entity_Id :=
2943 Make_Defining_Identifier (Loc,
2944 Chars => New_Internal_Name ('R'));
2945 Acc_Typ : constant Entity_Id :=
2946 Make_Defining_Identifier (Loc,
2947 Chars => New_Internal_Name ('A'));
2948 Alloc_Node : Node_Id;
2951 Set_Ekind (Acc_Typ, E_Access_Type);
2953 Set_Associated_Storage_Pool (Acc_Typ, RTE (RE_SS_Pool));
2956 Make_Allocator (Loc,
2958 Make_Qualified_Expression (Loc,
2959 Subtype_Mark => New_Reference_To (Etype (Exp), Loc),
2960 Expression => Relocate_Node (Exp)));
2962 Insert_List_Before_And_Analyze (N, New_List (
2963 Make_Full_Type_Declaration (Loc,
2964 Defining_Identifier => Acc_Typ,
2966 Make_Access_To_Object_Definition (Loc,
2967 Subtype_Indication =>
2968 New_Reference_To (Return_Type, Loc))),
2970 Make_Object_Declaration (Loc,
2971 Defining_Identifier => Temp,
2972 Object_Definition => New_Reference_To (Acc_Typ, Loc),
2973 Expression => Alloc_Node)));
2976 Make_Explicit_Dereference (Loc,
2977 Prefix => New_Reference_To (Temp, Loc)));
2979 Analyze_And_Resolve (Exp, Return_Type);
2982 -- Otherwise use the gigi mechanism to allocate result on the
2986 Set_Storage_Pool (N, RTE (RE_SS_Pool));
2988 -- If we are generating code for the Java VM do not use
2989 -- SS_Allocate since everything is heap-allocated anyway.
2992 Set_Procedure_To_Call (N, RTE (RE_SS_Allocate));
2998 when RE_Not_Available =>
3000 end Expand_N_Return_Statement;
3002 ------------------------------
3003 -- Make_Tag_Ctrl_Assignment --
3004 ------------------------------
3006 function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id is
3007 Loc : constant Source_Ptr := Sloc (N);
3008 L : constant Node_Id := Name (N);
3009 T : constant Entity_Id := Underlying_Type (Etype (L));
3011 Ctrl_Act : constant Boolean := Controlled_Type (T)
3012 and then not No_Ctrl_Actions (N);
3014 Save_Tag : constant Boolean := Is_Tagged_Type (T)
3015 and then not No_Ctrl_Actions (N)
3016 and then not Java_VM;
3017 -- Tags are not saved and restored when Java_VM because JVM tags
3018 -- are represented implicitly in objects.
3021 Tag_Tmp : Entity_Id;
3022 Prev_Tmp : Entity_Id;
3023 Next_Tmp : Entity_Id;
3025 Ctrl_Ref2 : Node_Id := Empty;
3026 Prev_Tmp2 : Entity_Id := Empty; -- prevent warning
3027 Next_Tmp2 : Entity_Id := Empty; -- prevent warning
3032 -- Finalize the target of the assignment when controlled.
3033 -- We have two exceptions here:
3035 -- 1. If we are in an init proc since it is an initialization
3036 -- more than an assignment
3038 -- 2. If the left-hand side is a temporary that was not initialized
3039 -- (or the parent part of a temporary since it is the case in
3040 -- extension aggregates). Such a temporary does not come from
3041 -- source. We must examine the original node for the prefix, because
3042 -- it may be a component of an entry formal, in which case it has
3043 -- been rewritten and does not appear to come from source either.
3045 -- Case of init proc
3047 if not Ctrl_Act then
3050 -- The left hand side is an uninitialized temporary
3052 elsif Nkind (L) = N_Type_Conversion
3053 and then Is_Entity_Name (Expression (L))
3054 and then No_Initialization (Parent (Entity (Expression (L))))
3058 Append_List_To (Res,
3060 Ref => Duplicate_Subexpr_No_Checks (L),
3062 With_Detach => New_Reference_To (Standard_False, Loc)));
3065 Next_Tmp := Make_Defining_Identifier (Loc, New_Internal_Name ('C'));
3067 -- Save the Tag in a local variable Tag_Tmp
3071 Make_Defining_Identifier (Loc, New_Internal_Name ('A'));
3074 Make_Object_Declaration (Loc,
3075 Defining_Identifier => Tag_Tmp,
3076 Object_Definition => New_Reference_To (RTE (RE_Tag), Loc),
3078 Make_Selected_Component (Loc,
3079 Prefix => Duplicate_Subexpr_No_Checks (L),
3080 Selector_Name => New_Reference_To (Tag_Component (T), Loc))));
3082 -- Otherwise Tag_Tmp not used
3088 -- Save the Finalization Pointers in local variables Prev_Tmp and
3089 -- Next_Tmp. For objects with Has_Controlled_Component set, these
3090 -- pointers are in the Record_Controller and if it is also
3091 -- Is_Controlled, we need to save the object pointers as well.
3094 Ctrl_Ref := Duplicate_Subexpr_No_Checks (L);
3096 if Has_Controlled_Component (T) then
3098 Make_Selected_Component (Loc,
3101 New_Reference_To (Controller_Component (T), Loc));
3103 if Is_Controlled (T) then
3104 Ctrl_Ref2 := Duplicate_Subexpr_No_Checks (L);
3108 Prev_Tmp := Make_Defining_Identifier (Loc, New_Internal_Name ('B'));
3111 Make_Object_Declaration (Loc,
3112 Defining_Identifier => Prev_Tmp,
3114 Object_Definition =>
3115 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc),
3118 Make_Selected_Component (Loc,
3120 Unchecked_Convert_To (RTE (RE_Finalizable), Ctrl_Ref),
3121 Selector_Name => Make_Identifier (Loc, Name_Prev))));
3123 Next_Tmp := Make_Defining_Identifier (Loc, New_Internal_Name ('C'));
3126 Make_Object_Declaration (Loc,
3127 Defining_Identifier => Next_Tmp,
3129 Object_Definition =>
3130 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc),
3133 Make_Selected_Component (Loc,
3135 Unchecked_Convert_To (RTE (RE_Finalizable),
3136 New_Copy_Tree (Ctrl_Ref)),
3137 Selector_Name => Make_Identifier (Loc, Name_Next))));
3139 if Present (Ctrl_Ref2) then
3141 Make_Defining_Identifier (Loc, New_Internal_Name ('B'));
3144 Make_Object_Declaration (Loc,
3145 Defining_Identifier => Prev_Tmp2,
3147 Object_Definition =>
3148 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc),
3151 Make_Selected_Component (Loc,
3153 Unchecked_Convert_To (RTE (RE_Finalizable), Ctrl_Ref2),
3154 Selector_Name => Make_Identifier (Loc, Name_Prev))));
3157 Make_Defining_Identifier (Loc, New_Internal_Name ('C'));
3160 Make_Object_Declaration (Loc,
3161 Defining_Identifier => Next_Tmp2,
3163 Object_Definition =>
3164 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc),
3167 Make_Selected_Component (Loc,
3169 Unchecked_Convert_To (RTE (RE_Finalizable),
3170 New_Copy_Tree (Ctrl_Ref2)),
3171 Selector_Name => Make_Identifier (Loc, Name_Next))));
3174 -- If not controlled type, then Prev_Tmp and Ctrl_Ref unused
3181 -- Do the Assignment
3183 Append_To (Res, Relocate_Node (N));
3189 Make_Assignment_Statement (Loc,
3191 Make_Selected_Component (Loc,
3192 Prefix => Duplicate_Subexpr_No_Checks (L),
3193 Selector_Name => New_Reference_To (Tag_Component (T), Loc)),
3194 Expression => New_Reference_To (Tag_Tmp, Loc)));
3197 -- Restore the finalization pointers
3201 Make_Assignment_Statement (Loc,
3203 Make_Selected_Component (Loc,
3205 Unchecked_Convert_To (RTE (RE_Finalizable),
3206 New_Copy_Tree (Ctrl_Ref)),
3207 Selector_Name => Make_Identifier (Loc, Name_Prev)),
3208 Expression => New_Reference_To (Prev_Tmp, Loc)));
3211 Make_Assignment_Statement (Loc,
3213 Make_Selected_Component (Loc,
3215 Unchecked_Convert_To (RTE (RE_Finalizable),
3216 New_Copy_Tree (Ctrl_Ref)),
3217 Selector_Name => Make_Identifier (Loc, Name_Next)),
3218 Expression => New_Reference_To (Next_Tmp, Loc)));
3220 if Present (Ctrl_Ref2) then
3222 Make_Assignment_Statement (Loc,
3224 Make_Selected_Component (Loc,
3226 Unchecked_Convert_To (RTE (RE_Finalizable),
3227 New_Copy_Tree (Ctrl_Ref2)),
3228 Selector_Name => Make_Identifier (Loc, Name_Prev)),
3229 Expression => New_Reference_To (Prev_Tmp2, Loc)));
3232 Make_Assignment_Statement (Loc,
3234 Make_Selected_Component (Loc,
3236 Unchecked_Convert_To (RTE (RE_Finalizable),
3237 New_Copy_Tree (Ctrl_Ref2)),
3238 Selector_Name => Make_Identifier (Loc, Name_Next)),
3239 Expression => New_Reference_To (Next_Tmp2, Loc)));
3243 -- Adjust the target after the assignment when controlled. (not in
3244 -- the init proc since it is an initialization more than an
3248 Append_List_To (Res,
3250 Ref => Duplicate_Subexpr_Move_Checks (L),
3252 Flist_Ref => New_Reference_To (RTE (RE_Global_Final_List), Loc),
3253 With_Attach => Make_Integer_Literal (Loc, 0)));
3259 when RE_Not_Available =>
3261 end Make_Tag_Ctrl_Assignment;
3263 ------------------------------------
3264 -- Possible_Bit_Aligned_Component --
3265 ------------------------------------
3267 function Possible_Bit_Aligned_Component (N : Node_Id) return Boolean is
3271 -- Case of indexed component
3273 when N_Indexed_Component =>
3275 P : constant Node_Id := Prefix (N);
3276 Ptyp : constant Entity_Id := Etype (P);
3279 -- If we know the component size and it is less than 64, then
3280 -- we are definitely OK. The back end always does assignment
3281 -- of misaligned small objects correctly.
3283 if Known_Static_Component_Size (Ptyp)
3284 and then Component_Size (Ptyp) <= 64
3288 -- Otherwise, we need to test the prefix, to see if we are
3289 -- indexing from a possibly unaligned component.
3292 return Possible_Bit_Aligned_Component (P);
3296 -- Case of selected component
3298 when N_Selected_Component =>
3300 P : constant Node_Id := Prefix (N);
3301 Comp : constant Entity_Id := Entity (Selector_Name (N));
3304 -- If there is no component clause, then we are in the clear
3305 -- since the back end will never misalign a large component
3306 -- unless it is forced to do so. In the clear means we need
3307 -- only the recursive test on the prefix.
3309 if Component_May_Be_Bit_Aligned (Comp) then
3312 return Possible_Bit_Aligned_Component (P);
3316 -- If we have neither a record nor array component, it means that
3317 -- we have fallen off the top testing prefixes recursively, and
3318 -- we now have a stand alone object, where we don't have a problem
3324 end Possible_Bit_Aligned_Component;