1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2003, 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_Util; use Exp_Util;
36 with Hostparm; use Hostparm;
37 with Nlists; use Nlists;
38 with Nmake; use Nmake;
40 with Restrict; use Restrict;
41 with Rtsfind; use Rtsfind;
42 with Sinfo; use Sinfo;
44 with Sem_Ch8; use Sem_Ch8;
45 with Sem_Ch13; use Sem_Ch13;
46 with Sem_Eval; use Sem_Eval;
47 with Sem_Res; use Sem_Res;
48 with Sem_Util; use Sem_Util;
49 with Snames; use Snames;
50 with Stand; use Stand;
51 with Tbuild; use Tbuild;
52 with Ttypes; use Ttypes;
53 with Uintp; use Uintp;
54 with Validsw; use Validsw;
56 package body Exp_Ch5 is
58 function Change_Of_Representation (N : Node_Id) return Boolean;
59 -- Determine if the right hand side of the assignment N is a type
60 -- conversion which requires a change of representation. Called
61 -- only for the array and record cases.
63 procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id);
64 -- N is an assignment which assigns an array value. This routine process
65 -- the various special cases and checks required for such assignments,
66 -- including change of representation. Rhs is normally simply the right
67 -- hand side of the assignment, except that if the right hand side is
68 -- a type conversion or a qualified expression, then the Rhs is the
69 -- actual expression inside any such type conversions or qualifications.
71 function Expand_Assign_Array_Loop
80 -- N is an assignment statement which assigns an array value. This routine
81 -- expands the assignment into a loop (or nested loops for the case of a
82 -- multi-dimensional array) to do the assignment component by component.
83 -- Larray and Rarray are the entities of the actual arrays on the left
84 -- hand and right hand sides. L_Type and R_Type are the types of these
85 -- arrays (which may not be the same, due to either sliding, or to a
86 -- change of representation case). Ndim is the number of dimensions and
87 -- the parameter Rev indicates if the loops run normally (Rev = False),
88 -- or reversed (Rev = True). The value returned is the constructed
89 -- loop statement. Auxiliary declarations are inserted before node N
90 -- using the standard Insert_Actions mechanism.
92 procedure Expand_Assign_Record (N : Node_Id);
93 -- N is an assignment of a non-tagged record value. This routine handles
94 -- the case where the assignment must be made component by component,
95 -- either because the target is not byte aligned, or there is a change
98 function Maybe_Bit_Aligned_Large_Component (N : Node_Id) return Boolean;
99 -- This function is used in processing the assignment of a record or
100 -- indexed component. The back end can handle such assignments fine
101 -- if the objects involved are small (64-bits) or are both aligned on
102 -- a byte boundary (starts on a byte, and ends on a byte). However,
103 -- problems arise for large components that are not byte aligned,
104 -- since the assignment may clobber other components that share bit
105 -- positions in the starting or ending bytes, and in the case of
106 -- components not starting on a byte boundary, the back end cannot
107 -- even manage to extract the value. This function is used to detect
108 -- such situations, so that the assignment can be handled component-wise.
109 -- A value of False means that either the object is known to be greater
110 -- than 64 bits, or that it is known to be byte aligned (and occupy an
111 -- integral number of bytes. True is returned if the object is known to
112 -- be greater than 64 bits, and is known to be unaligned. As implied
113 -- by the name, the result is conservative, in that if the compiler
114 -- cannot determine these conditions at compile time, True is returned.
116 function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id;
117 -- Generate the necessary code for controlled and Tagged assignment,
118 -- that is to say, finalization of the target before, adjustement of
119 -- the target after and save and restore of the tag and finalization
120 -- pointers which are not 'part of the value' and must not be changed
121 -- upon assignment. N is the original Assignment node.
123 ------------------------------
124 -- Change_Of_Representation --
125 ------------------------------
127 function Change_Of_Representation (N : Node_Id) return Boolean is
128 Rhs : constant Node_Id := Expression (N);
132 Nkind (Rhs) = N_Type_Conversion
134 not Same_Representation (Etype (Rhs), Etype (Expression (Rhs)));
135 end Change_Of_Representation;
137 -------------------------
138 -- Expand_Assign_Array --
139 -------------------------
141 -- There are two issues here. First, do we let Gigi do a block move, or
142 -- do we expand out into a loop? Second, we need to set the two flags
143 -- Forwards_OK and Backwards_OK which show whether the block move (or
144 -- corresponding loops) can be legitimately done in a forwards (low to
145 -- high) or backwards (high to low) manner.
147 procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id) is
148 Loc : constant Source_Ptr := Sloc (N);
150 Lhs : constant Node_Id := Name (N);
152 Act_Lhs : constant Node_Id := Get_Referenced_Object (Lhs);
153 Act_Rhs : Node_Id := Get_Referenced_Object (Rhs);
155 L_Type : constant Entity_Id :=
156 Underlying_Type (Get_Actual_Subtype (Act_Lhs));
157 R_Type : Entity_Id :=
158 Underlying_Type (Get_Actual_Subtype (Act_Rhs));
160 L_Slice : constant Boolean := Nkind (Act_Lhs) = N_Slice;
161 R_Slice : constant Boolean := Nkind (Act_Rhs) = N_Slice;
163 Crep : constant Boolean := Change_Of_Representation (N);
168 Ndim : constant Pos := Number_Dimensions (L_Type);
170 Loop_Required : Boolean := False;
171 -- This switch is set to True if the array move must be done using
172 -- an explicit front end generated loop.
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 function Possible_Unaligned_Slice (Arg : Node_Id) return Boolean;
190 -- Returns True if Arg (either the left or right hand side of the
191 -- assignment) is a slice that could be unaligned wrt the array type.
192 -- This is true if Arg is a component of a packed record, or is
193 -- a record component to which a component clause applies. This
194 -- is a little pessimistic, but the result of an unnecessary
195 -- decision that something is possibly unaligned is only to
196 -- generate a front end loop, which is not so terrible.
197 -- It would really be better if backend handled this ???
199 ------------------------
200 -- Has_Address_Clause --
201 ------------------------
203 function Has_Address_Clause (Exp : Node_Id) return Boolean is
206 (Is_Entity_Name (Exp) and then
207 Present (Address_Clause (Entity (Exp))))
209 (Nkind (Exp) = N_Slice and then Has_Address_Clause (Prefix (Exp)));
210 end Has_Address_Clause;
212 ---------------------
213 -- Is_Formal_Array --
214 ---------------------
216 function Is_Formal_Array (Exp : Node_Id) return Boolean is
219 (Is_Entity_Name (Exp) and then Is_Formal (Entity (Exp)))
221 (Nkind (Exp) = N_Slice and then Is_Formal_Array (Prefix (Exp)));
224 ------------------------
225 -- Is_Non_Local_Array --
226 ------------------------
228 function Is_Non_Local_Array (Exp : Node_Id) return Boolean is
230 return (Is_Entity_Name (Exp)
231 and then Scope (Entity (Exp)) /= Current_Scope)
232 or else (Nkind (Exp) = N_Slice
233 and then Is_Non_Local_Array (Prefix (Exp)));
234 end Is_Non_Local_Array;
236 ------------------------------
237 -- Possible_Unaligned_Slice --
238 ------------------------------
240 function Possible_Unaligned_Slice (Arg : Node_Id) return Boolean is
242 -- No issue if this is not a slice, or else strict alignment
243 -- is not required in any case.
245 if Nkind (Arg) /= N_Slice
246 or else not Target_Strict_Alignment
251 -- No issue if the component type is a byte or byte aligned
254 Array_Typ : constant Entity_Id := Etype (Arg);
255 Comp_Typ : constant Entity_Id := Component_Type (Array_Typ);
256 Pref : constant Node_Id := Prefix (Arg);
259 if Known_Alignment (Array_Typ) then
260 if Alignment (Array_Typ) = 1 then
264 elsif Known_Component_Size (Array_Typ) then
265 if Component_Size (Array_Typ) = 1 then
269 elsif Known_Esize (Comp_Typ) then
270 if Esize (Comp_Typ) <= System_Storage_Unit then
275 -- No issue if this is not a selected component
277 if Nkind (Pref) /= N_Selected_Component then
281 -- Else we test for a possibly unaligned component
284 Is_Packed (Etype (Pref))
286 Present (Component_Clause (Entity (Selector_Name (Pref))));
288 end Possible_Unaligned_Slice;
290 -- Determine if Lhs, Rhs are formal arrays or nonlocal arrays
292 Lhs_Formal : constant Boolean := Is_Formal_Array (Act_Lhs);
293 Rhs_Formal : constant Boolean := Is_Formal_Array (Act_Rhs);
295 Lhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Lhs);
296 Rhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Rhs);
298 -- Start of processing for Expand_Assign_Array
301 -- Deal with length check, note that the length check is done with
302 -- respect to the right hand side as given, not a possible underlying
303 -- renamed object, since this would generate incorrect extra checks.
305 Apply_Length_Check (Rhs, L_Type);
307 -- We start by assuming that the move can be done in either
308 -- direction, i.e. that the two sides are completely disjoint.
310 Set_Forwards_OK (N, True);
311 Set_Backwards_OK (N, True);
313 -- Normally it is only the slice case that can lead to overlap,
314 -- and explicit checks for slices are made below. But there is
315 -- one case where the slice can be implicit and invisible to us
316 -- and that is the case where we have a one dimensional array,
317 -- and either both operands are parameters, or one is a parameter
318 -- and the other is a global variable. In this case the parameter
319 -- could be a slice that overlaps with the other parameter.
321 -- Check for the case of slices requiring an explicit loop. Normally
322 -- it is only the explicit slice cases that bother us, but in the
323 -- case of one dimensional arrays, parameters can be slices that
324 -- are passed by reference, so we can have aliasing for assignments
325 -- from one parameter to another, or assignments between parameters
326 -- and nonlocal variables. However, if the array subtype is a
327 -- constrained first subtype in the parameter case, then we don't
328 -- have to worry about overlap, since slice assignments aren't
329 -- possible (other than for a slice denoting the whole array).
331 -- Note: overlap is never possible if there is a change of
332 -- representation, so we can exclude this case.
337 ((Lhs_Formal and Rhs_Formal)
339 (Lhs_Formal and Rhs_Non_Local_Var)
341 (Rhs_Formal and Lhs_Non_Local_Var))
343 (not Is_Constrained (Etype (Lhs))
344 or else not Is_First_Subtype (Etype (Lhs)))
346 -- In the case of compiling for the Java Virtual Machine,
347 -- slices are always passed by making a copy, so we don't
348 -- have to worry about overlap. We also want to prevent
349 -- generation of "<" comparisons for array addresses,
350 -- since that's a meaningless operation on the JVM.
354 Set_Forwards_OK (N, False);
355 Set_Backwards_OK (N, False);
357 -- Note: the bit-packed case is not worrisome here, since if
358 -- we have a slice passed as a parameter, it is always aligned
359 -- on a byte boundary, and if there are no explicit slices, the
360 -- assignment can be performed directly.
363 -- We certainly must use a loop for change of representation
364 -- and also we use the operand of the conversion on the right
365 -- hand side as the effective right hand side (the component
366 -- types must match in this situation).
369 Act_Rhs := Get_Referenced_Object (Rhs);
370 R_Type := Get_Actual_Subtype (Act_Rhs);
371 Loop_Required := True;
373 -- We require a loop if the left side is possibly bit unaligned
375 elsif Maybe_Bit_Aligned_Large_Component (Lhs)
377 Maybe_Bit_Aligned_Large_Component (Rhs)
379 Loop_Required := True;
381 -- Arrays with controlled components are expanded into a loop
382 -- to force calls to adjust at the component level.
384 elsif Has_Controlled_Component (L_Type) then
385 Loop_Required := True;
387 -- Case where no slice is involved
389 elsif not L_Slice and not R_Slice then
391 -- The following code deals with the case of unconstrained bit
392 -- packed arrays. The problem is that the template for such
393 -- arrays contains the bounds of the actual source level array,
395 -- But the copy of an entire array requires the bounds of the
396 -- underlying array. It would be nice if the back end could take
397 -- care of this, but right now it does not know how, so if we
398 -- have such a type, then we expand out into a loop, which is
399 -- inefficient but works correctly. If we don't do this, we
400 -- get the wrong length computed for the array to be moved.
401 -- The two cases we need to worry about are:
403 -- Explicit deference of an unconstrained packed array type as
404 -- in the following example:
407 -- type BITS is array(INTEGER range <>) of BOOLEAN;
408 -- pragma PACK(BITS);
409 -- type A is access BITS;
412 -- P1 := new BITS (1 .. 65_535);
413 -- P2 := new BITS (1 .. 65_535);
417 -- A formal parameter reference with an unconstrained bit
418 -- array type is the other case we need to worry about (here
419 -- we assume the same BITS type declared above:
421 -- procedure Write_All (File : out BITS; Contents : in BITS);
423 -- File.Storage := Contents;
426 -- We expand to a loop in either of these two cases.
428 -- Question for future thought. Another potentially more efficient
429 -- approach would be to create the actual subtype, and then do an
430 -- unchecked conversion to this actual subtype ???
432 Check_Unconstrained_Bit_Packed_Array : declare
434 function Is_UBPA_Reference (Opnd : Node_Id) return Boolean;
435 -- Function to perform required test for the first case,
436 -- above (dereference of an unconstrained bit packed array)
438 -----------------------
439 -- Is_UBPA_Reference --
440 -----------------------
442 function Is_UBPA_Reference (Opnd : Node_Id) return Boolean is
443 Typ : constant Entity_Id := Underlying_Type (Etype (Opnd));
445 Des_Type : Entity_Id;
448 if Present (Packed_Array_Type (Typ))
449 and then Is_Array_Type (Packed_Array_Type (Typ))
450 and then not Is_Constrained (Packed_Array_Type (Typ))
454 elsif Nkind (Opnd) = N_Explicit_Dereference then
455 P_Type := Underlying_Type (Etype (Prefix (Opnd)));
457 if not Is_Access_Type (P_Type) then
461 Des_Type := Designated_Type (P_Type);
463 Is_Bit_Packed_Array (Des_Type)
464 and then not Is_Constrained (Des_Type);
470 end Is_UBPA_Reference;
472 -- Start of processing for Check_Unconstrained_Bit_Packed_Array
475 if Is_UBPA_Reference (Lhs)
477 Is_UBPA_Reference (Rhs)
479 Loop_Required := True;
481 -- Here if we do not have the case of a reference to a bit
482 -- packed unconstrained array case. In this case gigi can
483 -- most certainly handle the assignment if a forwards move
486 -- (could it handle the backwards case also???)
488 elsif Forwards_OK (N) then
491 end Check_Unconstrained_Bit_Packed_Array;
493 -- Gigi can always handle the assignment if the right side is a string
494 -- literal (note that overlap is definitely impossible in this case).
495 -- If the type is packed, a string literal is always converted into a
496 -- aggregate, except in the case of a null slice, for which no aggregate
497 -- can be written. In that case, rewrite the assignment as a null
498 -- statement, a length check has already been emitted to verify that
499 -- the range of the left-hand side is empty.
501 elsif Nkind (Rhs) = N_String_Literal then
502 if Ekind (R_Type) = E_String_Literal_Subtype
503 and then String_Literal_Length (R_Type) = 0
504 and then Is_Bit_Packed_Array (L_Type)
506 Rewrite (N, Make_Null_Statement (Loc));
512 -- If either operand is bit packed, then we need a loop, since we
513 -- can't be sure that the slice is byte aligned. Similarly, if either
514 -- operand is a possibly unaligned slice, then we need a loop (since
515 -- gigi cannot handle unaligned slices).
517 elsif Is_Bit_Packed_Array (L_Type)
518 or else Is_Bit_Packed_Array (R_Type)
519 or else Possible_Unaligned_Slice (Lhs)
520 or else Possible_Unaligned_Slice (Rhs)
522 Loop_Required := True;
524 -- If we are not bit-packed, and we have only one slice, then no
525 -- overlap is possible except in the parameter case, so we can let
526 -- gigi handle things.
528 elsif not (L_Slice and R_Slice) then
529 if Forwards_OK (N) then
534 -- Come here to compelete the analysis
536 -- Loop_Required: Set to True if we know that a loop is required
537 -- regardless of overlap considerations.
539 -- Forwards_OK: Set to False if we already know that a forwards
540 -- move is not safe, else set to True.
542 -- Backwards_OK: Set to False if we already know that a backwards
543 -- move is not safe, else set to True
545 -- Our task at this stage is to complete the overlap analysis, which
546 -- can result in possibly setting Forwards_OK or Backwards_OK to
547 -- False, and then generating the final code, either by deciding
548 -- that it is OK after all to let Gigi handle it, or by generating
549 -- appropriate code in the front end.
552 L_Index_Typ : constant Node_Id := Etype (First_Index (L_Type));
553 R_Index_Typ : constant Node_Id := Etype (First_Index (R_Type));
555 Left_Lo : constant Node_Id := Type_Low_Bound (L_Index_Typ);
556 Left_Hi : constant Node_Id := Type_High_Bound (L_Index_Typ);
557 Right_Lo : constant Node_Id := Type_Low_Bound (R_Index_Typ);
558 Right_Hi : constant Node_Id := Type_High_Bound (R_Index_Typ);
560 Act_L_Array : Node_Id;
561 Act_R_Array : Node_Id;
567 Cresult : Compare_Result;
570 -- Get the expressions for the arrays. If we are dealing with a
571 -- private type, then convert to the underlying type. We can do
572 -- direct assignments to an array that is a private type, but
573 -- we cannot assign to elements of the array without this extra
574 -- unchecked conversion.
576 if Nkind (Act_Lhs) = N_Slice then
577 Larray := Prefix (Act_Lhs);
581 if Is_Private_Type (Etype (Larray)) then
584 (Underlying_Type (Etype (Larray)), Larray);
588 if Nkind (Act_Rhs) = N_Slice then
589 Rarray := Prefix (Act_Rhs);
593 if Is_Private_Type (Etype (Rarray)) then
596 (Underlying_Type (Etype (Rarray)), Rarray);
600 -- If both sides are slices, we must figure out whether
601 -- it is safe to do the move in one direction or the other
602 -- It is always safe if there is a change of representation
603 -- since obviously two arrays with different representations
604 -- cannot possibly overlap.
606 if (not Crep) and L_Slice and R_Slice then
607 Act_L_Array := Get_Referenced_Object (Prefix (Act_Lhs));
608 Act_R_Array := Get_Referenced_Object (Prefix (Act_Rhs));
610 -- If both left and right hand arrays are entity names, and
611 -- refer to different entities, then we know that the move
612 -- is safe (the two storage areas are completely disjoint).
614 if Is_Entity_Name (Act_L_Array)
615 and then Is_Entity_Name (Act_R_Array)
616 and then Entity (Act_L_Array) /= Entity (Act_R_Array)
620 -- Otherwise, we assume the worst, which is that the two
621 -- arrays are the same array. There is no need to check if
622 -- we know that is the case, because if we don't know it,
623 -- we still have to assume it!
625 -- Generally if the same array is involved, then we have
626 -- an overlapping case. We will have to really assume the
627 -- worst (i.e. set neither of the OK flags) unless we can
628 -- determine the lower or upper bounds at compile time and
632 Cresult := Compile_Time_Compare (Left_Lo, Right_Lo);
634 if Cresult = Unknown then
635 Cresult := Compile_Time_Compare (Left_Hi, Right_Hi);
639 when LT | LE | EQ => Set_Backwards_OK (N, False);
640 when GT | GE => Set_Forwards_OK (N, False);
641 when NE | Unknown => Set_Backwards_OK (N, False);
642 Set_Forwards_OK (N, False);
647 -- If after that analysis, Forwards_OK is still True, and
648 -- Loop_Required is False, meaning that we have not discovered
649 -- some non-overlap reason for requiring a loop, then we can
650 -- still let gigi handle it.
652 if not Loop_Required then
653 if Forwards_OK (N) then
658 -- Here is where a memmove would be appropriate ???
662 -- At this stage we have to generate an explicit loop, and
663 -- we have the following cases:
665 -- Forwards_OK = True
667 -- Rnn : right_index := right_index'First;
668 -- for Lnn in left-index loop
669 -- left (Lnn) := right (Rnn);
670 -- Rnn := right_index'Succ (Rnn);
673 -- Note: the above code MUST be analyzed with checks off,
674 -- because otherwise the Succ could overflow. But in any
675 -- case this is more efficient!
677 -- Forwards_OK = False, Backwards_OK = True
679 -- Rnn : right_index := right_index'Last;
680 -- for Lnn in reverse left-index loop
681 -- left (Lnn) := right (Rnn);
682 -- Rnn := right_index'Pred (Rnn);
685 -- Note: the above code MUST be analyzed with checks off,
686 -- because otherwise the Pred could overflow. But in any
687 -- case this is more efficient!
689 -- Forwards_OK = Backwards_OK = False
691 -- This only happens if we have the same array on each side. It is
692 -- possible to create situations using overlays that violate this,
693 -- but we simply do not promise to get this "right" in this case.
695 -- There are two possible subcases. If the No_Implicit_Conditionals
696 -- restriction is set, then we generate the following code:
699 -- T : constant <operand-type> := rhs;
704 -- If implicit conditionals are permitted, then we generate:
706 -- if Left_Lo <= Right_Lo then
707 -- <code for Forwards_OK = True above>
709 -- <code for Backwards_OK = True above>
712 -- Cases where either Forwards_OK or Backwards_OK is true
714 if Forwards_OK (N) or else Backwards_OK (N) then
716 Expand_Assign_Array_Loop
717 (N, Larray, Rarray, L_Type, R_Type, Ndim,
718 Rev => not Forwards_OK (N)));
720 -- Case of both are false with No_Implicit_Conditionals
722 elsif Restrictions (No_Implicit_Conditionals) then
724 T : constant Entity_Id := Make_Defining_Identifier (Loc,
729 Make_Block_Statement (Loc,
730 Declarations => New_List (
731 Make_Object_Declaration (Loc,
732 Defining_Identifier => T,
733 Constant_Present => True,
735 New_Occurrence_Of (Etype (Rhs), Loc),
736 Expression => Relocate_Node (Rhs))),
738 Handled_Statement_Sequence =>
739 Make_Handled_Sequence_Of_Statements (Loc,
740 Statements => New_List (
741 Make_Assignment_Statement (Loc,
742 Name => Relocate_Node (Lhs),
743 Expression => New_Occurrence_Of (T, Loc))))));
746 -- Case of both are false with implicit conditionals allowed
749 -- Before we generate this code, we must ensure that the
750 -- left and right side array types are defined. They may
751 -- be itypes, and we cannot let them be defined inside the
752 -- if, since the first use in the then may not be executed.
754 Ensure_Defined (L_Type, N);
755 Ensure_Defined (R_Type, N);
757 -- We normally compare addresses to find out which way round
758 -- to do the loop, since this is realiable, and handles the
759 -- cases of parameters, conversions etc. But we can't do that
760 -- in the bit packed case or the Java VM case, because addresses
763 if not Is_Bit_Packed_Array (L_Type) and then not Java_VM then
767 Unchecked_Convert_To (RTE (RE_Integer_Address),
768 Make_Attribute_Reference (Loc,
770 Make_Indexed_Component (Loc,
772 Duplicate_Subexpr_Move_Checks (Larray, True),
773 Expressions => New_List (
774 Make_Attribute_Reference (Loc,
778 Attribute_Name => Name_First))),
779 Attribute_Name => Name_Address)),
782 Unchecked_Convert_To (RTE (RE_Integer_Address),
783 Make_Attribute_Reference (Loc,
785 Make_Indexed_Component (Loc,
787 Duplicate_Subexpr_Move_Checks (Rarray, True),
788 Expressions => New_List (
789 Make_Attribute_Reference (Loc,
793 Attribute_Name => Name_First))),
794 Attribute_Name => Name_Address)));
796 -- For the bit packed and Java VM cases we use the bounds.
797 -- That's OK, because we don't have to worry about parameters,
798 -- since they cannot cause overlap. Perhaps we should worry
799 -- about weird slice conversions ???
802 -- Copy the bounds and reset the Analyzed flag, because the
803 -- bounds of the index type itself may be universal, and must
804 -- must be reaanalyzed to acquire the proper type for Gigi.
806 Cleft_Lo := New_Copy_Tree (Left_Lo);
807 Cright_Lo := New_Copy_Tree (Right_Lo);
808 Set_Analyzed (Cleft_Lo, False);
809 Set_Analyzed (Cright_Lo, False);
813 Left_Opnd => Cleft_Lo,
814 Right_Opnd => Cright_Lo);
818 Make_Implicit_If_Statement (N,
819 Condition => Condition,
821 Then_Statements => New_List (
822 Expand_Assign_Array_Loop
823 (N, Larray, Rarray, L_Type, R_Type, Ndim,
826 Else_Statements => New_List (
827 Expand_Assign_Array_Loop
828 (N, Larray, Rarray, L_Type, R_Type, Ndim,
832 Analyze (N, Suppress => All_Checks);
836 when RE_Not_Available =>
838 end Expand_Assign_Array;
840 ------------------------------
841 -- Expand_Assign_Array_Loop --
842 ------------------------------
844 -- The following is an example of the loop generated for the case of
845 -- a two-dimensional array:
850 -- for L1b in 1 .. 100 loop
854 -- for L3b in 1 .. 100 loop
855 -- vm1 (L1b, L3b) := vm2 (R2b, R4b);
856 -- R4b := Tm1X2'succ(R4b);
859 -- R2b := Tm1X1'succ(R2b);
863 -- Here Rev is False, and Tm1Xn are the subscript types for the right
864 -- hand side. The declarations of R2b and R4b are inserted before the
865 -- original assignment statement.
867 function Expand_Assign_Array_Loop
877 Loc : constant Source_Ptr := Sloc (N);
879 Lnn : array (1 .. Ndim) of Entity_Id;
880 Rnn : array (1 .. Ndim) of Entity_Id;
881 -- Entities used as subscripts on left and right sides
883 L_Index_Type : array (1 .. Ndim) of Entity_Id;
884 R_Index_Type : array (1 .. Ndim) of Entity_Id;
885 -- Left and right index types
897 F_Or_L := Name_First;
901 -- Setup index types and subscript entities
908 L_Index := First_Index (L_Type);
909 R_Index := First_Index (R_Type);
911 for J in 1 .. Ndim loop
913 Make_Defining_Identifier (Loc,
914 Chars => New_Internal_Name ('L'));
917 Make_Defining_Identifier (Loc,
918 Chars => New_Internal_Name ('R'));
920 L_Index_Type (J) := Etype (L_Index);
921 R_Index_Type (J) := Etype (R_Index);
923 Next_Index (L_Index);
924 Next_Index (R_Index);
928 -- Now construct the assignment statement
931 ExprL : constant List_Id := New_List;
932 ExprR : constant List_Id := New_List;
935 for J in 1 .. Ndim loop
936 Append_To (ExprL, New_Occurrence_Of (Lnn (J), Loc));
937 Append_To (ExprR, New_Occurrence_Of (Rnn (J), Loc));
941 Make_Assignment_Statement (Loc,
943 Make_Indexed_Component (Loc,
944 Prefix => Duplicate_Subexpr (Larray, Name_Req => True),
945 Expressions => ExprL),
947 Make_Indexed_Component (Loc,
948 Prefix => Duplicate_Subexpr (Rarray, Name_Req => True),
949 Expressions => ExprR));
951 -- Propagate the No_Ctrl_Actions flag to individual assignments
953 Set_No_Ctrl_Actions (Assign, No_Ctrl_Actions (N));
956 -- Now construct the loop from the inside out, with the last subscript
957 -- varying most rapidly. Note that Assign is first the raw assignment
958 -- statement, and then subsequently the loop that wraps it up.
960 for J in reverse 1 .. Ndim loop
962 Make_Block_Statement (Loc,
963 Declarations => New_List (
964 Make_Object_Declaration (Loc,
965 Defining_Identifier => Rnn (J),
967 New_Occurrence_Of (R_Index_Type (J), Loc),
969 Make_Attribute_Reference (Loc,
970 Prefix => New_Occurrence_Of (R_Index_Type (J), Loc),
971 Attribute_Name => F_Or_L))),
973 Handled_Statement_Sequence =>
974 Make_Handled_Sequence_Of_Statements (Loc,
975 Statements => New_List (
976 Make_Implicit_Loop_Statement (N,
978 Make_Iteration_Scheme (Loc,
979 Loop_Parameter_Specification =>
980 Make_Loop_Parameter_Specification (Loc,
981 Defining_Identifier => Lnn (J),
982 Reverse_Present => Rev,
983 Discrete_Subtype_Definition =>
984 New_Reference_To (L_Index_Type (J), Loc))),
986 Statements => New_List (
989 Make_Assignment_Statement (Loc,
990 Name => New_Occurrence_Of (Rnn (J), Loc),
992 Make_Attribute_Reference (Loc,
994 New_Occurrence_Of (R_Index_Type (J), Loc),
995 Attribute_Name => S_Or_P,
996 Expressions => New_List (
997 New_Occurrence_Of (Rnn (J), Loc)))))))));
1001 end Expand_Assign_Array_Loop;
1003 --------------------------
1004 -- Expand_Assign_Record --
1005 --------------------------
1007 -- The only processing required is in the change of representation
1008 -- case, where we must expand the assignment to a series of field
1009 -- by field assignments.
1011 procedure Expand_Assign_Record (N : Node_Id) is
1012 Lhs : constant Node_Id := Name (N);
1013 Rhs : Node_Id := Expression (N);
1016 -- If change of representation, then extract the real right hand
1017 -- side from the type conversion, and proceed with component-wise
1018 -- assignment, since the two types are not the same as far as the
1019 -- back end is concerned.
1021 if Change_Of_Representation (N) then
1022 Rhs := Expression (Rhs);
1024 -- If this may be a case of a large bit aligned component, then
1025 -- proceed with component-wise assignment, to avoid possible
1026 -- clobbering of other components sharing bits in the first or
1027 -- last byte of the component to be assigned.
1029 elsif Maybe_Bit_Aligned_Large_Component (Lhs)
1031 Maybe_Bit_Aligned_Large_Component (Rhs)
1035 -- If neither condition met, then nothing special to do, the back end
1036 -- can handle assignment of the entire component as a single entity.
1042 -- At this stage we know that we must do a component wise assignment
1045 Loc : constant Source_Ptr := Sloc (N);
1046 R_Typ : constant Entity_Id := Base_Type (Etype (Rhs));
1047 L_Typ : constant Entity_Id := Base_Type (Etype (Lhs));
1048 Decl : constant Node_Id := Declaration_Node (R_Typ);
1052 function Find_Component
1054 Comp : Entity_Id) return Entity_Id;
1055 -- Find the component with the given name in the underlying record
1056 -- declaration for Typ. We need to use the actual entity because
1057 -- the type may be private and resolution by identifier alone would
1060 function Make_Component_List_Assign (CL : Node_Id) return List_Id;
1061 -- Returns a sequence of statements to assign the components that
1062 -- are referenced in the given component list.
1064 function Make_Field_Assign (C : Entity_Id) return Node_Id;
1065 -- Given C, the entity for a discriminant or component, build
1066 -- an assignment for the corresponding field values.
1068 function Make_Field_Assigns (CI : List_Id) return List_Id;
1069 -- Given CI, a component items list, construct series of statements
1070 -- for fieldwise assignment of the corresponding components.
1072 --------------------
1073 -- Find_Component --
1074 --------------------
1076 function Find_Component
1078 Comp : Entity_Id) return Entity_Id
1080 Utyp : constant Entity_Id := Underlying_Type (Typ);
1084 C := First_Entity (Utyp);
1086 while Present (C) loop
1087 if Chars (C) = Chars (Comp) then
1093 raise Program_Error;
1096 --------------------------------
1097 -- Make_Component_List_Assign --
1098 --------------------------------
1100 function Make_Component_List_Assign (CL : Node_Id) return List_Id is
1101 CI : constant List_Id := Component_Items (CL);
1102 VP : constant Node_Id := Variant_Part (CL);
1111 Result := Make_Field_Assigns (CI);
1113 if Present (VP) then
1115 V := First_Non_Pragma (Variants (VP));
1117 while Present (V) loop
1120 DC := First (Discrete_Choices (V));
1121 while Present (DC) loop
1122 Append_To (DCH, New_Copy_Tree (DC));
1127 Make_Case_Statement_Alternative (Loc,
1128 Discrete_Choices => DCH,
1130 Make_Component_List_Assign (Component_List (V))));
1131 Next_Non_Pragma (V);
1135 Make_Case_Statement (Loc,
1137 Make_Selected_Component (Loc,
1138 Prefix => Duplicate_Subexpr (Rhs),
1140 Make_Identifier (Loc, Chars (Name (VP)))),
1141 Alternatives => Alts));
1146 end Make_Component_List_Assign;
1148 -----------------------
1149 -- Make_Field_Assign --
1150 -----------------------
1152 function Make_Field_Assign (C : Entity_Id) return Node_Id is
1157 Make_Assignment_Statement (Loc,
1159 Make_Selected_Component (Loc,
1160 Prefix => Duplicate_Subexpr (Lhs),
1162 New_Occurrence_Of (Find_Component (L_Typ, C), Loc)),
1164 Make_Selected_Component (Loc,
1165 Prefix => Duplicate_Subexpr (Rhs),
1166 Selector_Name => New_Occurrence_Of (C, Loc)));
1168 -- Set Assignment_OK, so discriminants can be assigned
1170 Set_Assignment_OK (Name (A), True);
1172 end Make_Field_Assign;
1174 ------------------------
1175 -- Make_Field_Assigns --
1176 ------------------------
1178 function Make_Field_Assigns (CI : List_Id) return List_Id is
1186 while Present (Item) loop
1187 if Nkind (Item) = N_Component_Declaration then
1189 (Result, Make_Field_Assign (Defining_Identifier (Item)));
1196 end Make_Field_Assigns;
1198 -- Start of processing for Expand_Assign_Record
1201 -- Note that we use the base types for this processing. This results
1202 -- in some extra work in the constrained case, but the change of
1203 -- representation case is so unusual that it is not worth the effort.
1205 -- First copy the discriminants. This is done unconditionally. It
1206 -- is required in the unconstrained left side case, and also in the
1207 -- case where this assignment was constructed during the expansion
1208 -- of a type conversion (since initialization of discriminants is
1209 -- suppressed in this case). It is unnecessary but harmless in
1212 if Has_Discriminants (L_Typ) then
1213 F := First_Discriminant (R_Typ);
1214 while Present (F) loop
1215 Insert_Action (N, Make_Field_Assign (F));
1216 Next_Discriminant (F);
1220 -- We know the underlying type is a record, but its current view
1221 -- may be private. We must retrieve the usable record declaration.
1223 if Nkind (Decl) = N_Private_Type_Declaration
1224 and then Present (Full_View (R_Typ))
1226 RDef := Type_Definition (Declaration_Node (Full_View (R_Typ)));
1228 RDef := Type_Definition (Decl);
1231 if Nkind (RDef) = N_Record_Definition
1232 and then Present (Component_List (RDef))
1235 (N, Make_Component_List_Assign (Component_List (RDef)));
1237 Rewrite (N, Make_Null_Statement (Loc));
1241 end Expand_Assign_Record;
1243 -----------------------------------
1244 -- Expand_N_Assignment_Statement --
1245 -----------------------------------
1247 -- For array types, deal with slice assignments and setting the flags
1248 -- to indicate if it can be statically determined which direction the
1249 -- move should go in. Also deal with generating range/length checks.
1251 procedure Expand_N_Assignment_Statement (N : Node_Id) is
1252 Loc : constant Source_Ptr := Sloc (N);
1253 Lhs : constant Node_Id := Name (N);
1254 Rhs : constant Node_Id := Expression (N);
1255 Typ : constant Entity_Id := Underlying_Type (Etype (Lhs));
1259 -- First deal with generation of range check if required. For now
1260 -- we do this only for discrete types.
1262 if Do_Range_Check (Rhs)
1263 and then Is_Discrete_Type (Typ)
1265 Set_Do_Range_Check (Rhs, False);
1266 Generate_Range_Check (Rhs, Typ, CE_Range_Check_Failed);
1269 -- Check for a special case where a high level transformation is
1270 -- required. If we have either of:
1275 -- where P is a reference to a bit packed array, then we have to unwind
1276 -- the assignment. The exact meaning of being a reference to a bit
1277 -- packed array is as follows:
1279 -- An indexed component whose prefix is a bit packed array is a
1280 -- reference to a bit packed array.
1282 -- An indexed component or selected component whose prefix is a
1283 -- reference to a bit packed array is itself a reference ot a
1284 -- bit packed array.
1286 -- The required transformation is
1288 -- Tnn : prefix_type := P;
1289 -- Tnn.field := rhs;
1294 -- Tnn : prefix_type := P;
1295 -- Tnn (subscr) := rhs;
1298 -- Since P is going to be evaluated more than once, any subscripts
1299 -- in P must have their evaluation forced.
1301 if (Nkind (Lhs) = N_Indexed_Component
1303 Nkind (Lhs) = N_Selected_Component)
1304 and then Is_Ref_To_Bit_Packed_Array (Prefix (Lhs))
1307 BPAR_Expr : constant Node_Id := Relocate_Node (Prefix (Lhs));
1308 BPAR_Typ : constant Entity_Id := Etype (BPAR_Expr);
1309 Tnn : constant Entity_Id :=
1310 Make_Defining_Identifier (Loc,
1311 Chars => New_Internal_Name ('T'));
1314 -- Insert the post assignment first, because we want to copy
1315 -- the BPAR_Expr tree before it gets analyzed in the context
1316 -- of the pre assignment. Note that we do not analyze the
1317 -- post assignment yet (we cannot till we have completed the
1318 -- analysis of the pre assignment). As usual, the analysis
1319 -- of this post assignment will happen on its own when we
1320 -- "run into" it after finishing the current assignment.
1323 Make_Assignment_Statement (Loc,
1324 Name => New_Copy_Tree (BPAR_Expr),
1325 Expression => New_Occurrence_Of (Tnn, Loc)));
1327 -- At this stage BPAR_Expr is a reference to a bit packed
1328 -- array where the reference was not expanded in the original
1329 -- tree, since it was on the left side of an assignment. But
1330 -- in the pre-assignment statement (the object definition),
1331 -- BPAR_Expr will end up on the right hand side, and must be
1332 -- reexpanded. To achieve this, we reset the analyzed flag
1333 -- of all selected and indexed components down to the actual
1334 -- indexed component for the packed array.
1338 Set_Analyzed (Exp, False);
1340 if Nkind (Exp) = N_Selected_Component
1342 Nkind (Exp) = N_Indexed_Component
1344 Exp := Prefix (Exp);
1350 -- Now we can insert and analyze the pre-assignment.
1352 -- If the right-hand side requires a transient scope, it has
1353 -- already been placed on the stack. However, the declaration is
1354 -- inserted in the tree outside of this scope, and must reflect
1355 -- the proper scope for its variable. This awkward bit is forced
1356 -- by the stricter scope discipline imposed by GCC 2.97.
1359 Uses_Transient_Scope : constant Boolean :=
1360 Scope_Is_Transient and then N = Node_To_Be_Wrapped;
1363 if Uses_Transient_Scope then
1364 New_Scope (Scope (Current_Scope));
1367 Insert_Before_And_Analyze (N,
1368 Make_Object_Declaration (Loc,
1369 Defining_Identifier => Tnn,
1370 Object_Definition => New_Occurrence_Of (BPAR_Typ, Loc),
1371 Expression => BPAR_Expr));
1373 if Uses_Transient_Scope then
1378 -- Now fix up the original assignment and continue processing
1380 Rewrite (Prefix (Lhs),
1381 New_Occurrence_Of (Tnn, Loc));
1383 -- We do not need to reanalyze that assignment, and we do not need
1384 -- to worry about references to the temporary, but we do need to
1385 -- make sure that the temporary is not marked as a true constant
1386 -- since we now have a generate assignment to it!
1388 Set_Is_True_Constant (Tnn, False);
1392 -- When we have the appropriate type of aggregate in the
1393 -- expression (it has been determined during analysis of the
1394 -- aggregate by setting the delay flag), let's perform in place
1395 -- assignment and thus avoid creating a temporay.
1397 if Is_Delayed_Aggregate (Rhs) then
1398 Convert_Aggr_In_Assignment (N);
1399 Rewrite (N, Make_Null_Statement (Loc));
1404 -- Apply discriminant check if required. If Lhs is an access type
1405 -- to a designated type with discriminants, we must always check.
1407 if Has_Discriminants (Etype (Lhs)) then
1409 -- Skip discriminant check if change of representation. Will be
1410 -- done when the change of representation is expanded out.
1412 if not Change_Of_Representation (N) then
1413 Apply_Discriminant_Check (Rhs, Etype (Lhs), Lhs);
1416 -- If the type is private without discriminants, and the full type
1417 -- has discriminants (necessarily with defaults) a check may still be
1418 -- necessary if the Lhs is aliased. The private determinants must be
1419 -- visible to build the discriminant constraints.
1421 -- Only an explicit dereference that comes from source indicates
1422 -- aliasing. Access to formals of protected operations and entries
1423 -- create dereferences but are not semantic aliasings.
1425 elsif Is_Private_Type (Etype (Lhs))
1426 and then Has_Discriminants (Typ)
1427 and then Nkind (Lhs) = N_Explicit_Dereference
1428 and then Comes_From_Source (Lhs)
1431 Lt : constant Entity_Id := Etype (Lhs);
1433 Set_Etype (Lhs, Typ);
1434 Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs));
1435 Apply_Discriminant_Check (Rhs, Typ, Lhs);
1436 Set_Etype (Lhs, Lt);
1439 -- If the Lhs has a private type with unknown discriminants, it
1440 -- may have a full view with discriminants, but those are nameable
1441 -- only in the underlying type, so convert the Rhs to it before
1442 -- potential checking.
1444 elsif Has_Unknown_Discriminants (Base_Type (Etype (Lhs)))
1445 and then Has_Discriminants (Typ)
1447 Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs));
1448 Apply_Discriminant_Check (Rhs, Typ, Lhs);
1450 -- In the access type case, we need the same discriminant check,
1451 -- and also range checks if we have an access to constrained array.
1453 elsif Is_Access_Type (Etype (Lhs))
1454 and then Is_Constrained (Designated_Type (Etype (Lhs)))
1456 if Has_Discriminants (Designated_Type (Etype (Lhs))) then
1458 -- Skip discriminant check if change of representation. Will be
1459 -- done when the change of representation is expanded out.
1461 if not Change_Of_Representation (N) then
1462 Apply_Discriminant_Check (Rhs, Etype (Lhs));
1465 elsif Is_Array_Type (Designated_Type (Etype (Lhs))) then
1466 Apply_Range_Check (Rhs, Etype (Lhs));
1468 if Is_Constrained (Etype (Lhs)) then
1469 Apply_Length_Check (Rhs, Etype (Lhs));
1472 if Nkind (Rhs) = N_Allocator then
1474 Target_Typ : constant Entity_Id := Etype (Expression (Rhs));
1475 C_Es : Check_Result;
1482 Etype (Designated_Type (Etype (Lhs))));
1494 -- Apply range check for access type case
1496 elsif Is_Access_Type (Etype (Lhs))
1497 and then Nkind (Rhs) = N_Allocator
1498 and then Nkind (Expression (Rhs)) = N_Qualified_Expression
1500 Analyze_And_Resolve (Expression (Rhs));
1502 (Expression (Rhs), Designated_Type (Etype (Lhs)));
1505 -- If we are assigning an access type and the left side is an
1506 -- entity, then make sure that Is_Known_Non_Null properly
1507 -- reflects the state of the entity after the assignment
1509 if Is_Access_Type (Typ)
1510 and then Is_Entity_Name (Lhs)
1511 and then Known_Non_Null (Rhs)
1512 and then Safe_To_Capture_Value (N, Entity (Lhs))
1514 Set_Is_Known_Non_Null (Entity (Lhs), Known_Non_Null (Rhs));
1517 -- Case of assignment to a bit packed array element
1519 if Nkind (Lhs) = N_Indexed_Component
1520 and then Is_Bit_Packed_Array (Etype (Prefix (Lhs)))
1522 Expand_Bit_Packed_Element_Set (N);
1525 -- Case of tagged type assignment
1527 elsif Is_Tagged_Type (Typ)
1528 or else (Controlled_Type (Typ) and then not Is_Array_Type (Typ))
1530 Tagged_Case : declare
1531 L : List_Id := No_List;
1532 Expand_Ctrl_Actions : constant Boolean := not No_Ctrl_Actions (N);
1535 -- In the controlled case, we need to make sure that function
1536 -- calls are evaluated before finalizing the target. In all
1537 -- cases, it makes the expansion easier if the side-effects
1538 -- are removed first.
1540 Remove_Side_Effects (Lhs);
1541 Remove_Side_Effects (Rhs);
1543 -- Avoid recursion in the mechanism
1547 -- If dispatching assignment, we need to dispatch to _assign
1549 if Is_Class_Wide_Type (Typ)
1551 -- If the type is tagged, we may as well use the predefined
1552 -- primitive assignment. This avoids inlining a lot of code
1553 -- and in the class-wide case, the assignment is replaced by
1554 -- a dispatch call to _assign. Note that this cannot be done
1555 -- when discriminant checks are locally suppressed (as in
1556 -- extension aggregate expansions) because otherwise the
1557 -- discriminant check will be performed within the _assign
1560 or else (Is_Tagged_Type (Typ)
1561 and then Chars (Current_Scope) /= Name_uAssign
1562 and then Expand_Ctrl_Actions
1563 and then not Discriminant_Checks_Suppressed (Empty))
1565 -- Fetch the primitive op _assign and proper type to call
1566 -- it. Because of possible conflits between private and
1567 -- full view the proper type is fetched directly from the
1568 -- operation profile.
1571 Op : constant Entity_Id :=
1572 Find_Prim_Op (Typ, Name_uAssign);
1573 F_Typ : Entity_Id := Etype (First_Formal (Op));
1576 -- If the assignment is dispatching, make sure to use the
1577 -- ??? where is rest of this comment ???
1579 if Is_Class_Wide_Type (Typ) then
1580 F_Typ := Class_Wide_Type (F_Typ);
1584 Make_Procedure_Call_Statement (Loc,
1585 Name => New_Reference_To (Op, Loc),
1586 Parameter_Associations => New_List (
1587 Unchecked_Convert_To (F_Typ, Duplicate_Subexpr (Lhs)),
1588 Unchecked_Convert_To (F_Typ,
1589 Duplicate_Subexpr (Rhs)))));
1593 L := Make_Tag_Ctrl_Assignment (N);
1595 -- We can't afford to have destructive Finalization Actions
1596 -- in the Self assignment case, so if the target and the
1597 -- source are not obviously different, code is generated to
1598 -- avoid the self assignment case
1600 -- if lhs'address /= rhs'address then
1601 -- <code for controlled and/or tagged assignment>
1604 if not Statically_Different (Lhs, Rhs)
1605 and then Expand_Ctrl_Actions
1608 Make_Implicit_If_Statement (N,
1612 Make_Attribute_Reference (Loc,
1613 Prefix => Duplicate_Subexpr (Lhs),
1614 Attribute_Name => Name_Address),
1617 Make_Attribute_Reference (Loc,
1618 Prefix => Duplicate_Subexpr (Rhs),
1619 Attribute_Name => Name_Address)),
1621 Then_Statements => L));
1624 -- We need to set up an exception handler for implementing
1625 -- 7.6.1 (18). The remaining adjustments are tackled by the
1626 -- implementation of adjust for record_controllers (see
1629 -- This is skipped if we have no finalization
1631 if Expand_Ctrl_Actions
1632 and then not Restrictions (No_Finalization)
1635 Make_Block_Statement (Loc,
1636 Handled_Statement_Sequence =>
1637 Make_Handled_Sequence_Of_Statements (Loc,
1639 Exception_Handlers => New_List (
1640 Make_Exception_Handler (Loc,
1641 Exception_Choices =>
1642 New_List (Make_Others_Choice (Loc)),
1643 Statements => New_List (
1644 Make_Raise_Program_Error (Loc,
1646 PE_Finalize_Raised_Exception)
1652 Make_Block_Statement (Loc,
1653 Handled_Statement_Sequence =>
1654 Make_Handled_Sequence_Of_Statements (Loc, Statements => L)));
1656 -- If no restrictions on aborts, protect the whole assignement
1657 -- for controlled objects as per 9.8(11)
1659 if Controlled_Type (Typ)
1660 and then Expand_Ctrl_Actions
1661 and then Abort_Allowed
1664 Blk : constant Entity_Id :=
1665 New_Internal_Entity (
1666 E_Block, Current_Scope, Sloc (N), 'B');
1669 Set_Scope (Blk, Current_Scope);
1670 Set_Etype (Blk, Standard_Void_Type);
1671 Set_Identifier (N, New_Occurrence_Of (Blk, Sloc (N)));
1673 Prepend_To (L, Build_Runtime_Call (Loc, RE_Abort_Defer));
1674 Set_At_End_Proc (Handled_Statement_Sequence (N),
1675 New_Occurrence_Of (RTE (RE_Abort_Undefer_Direct), Loc));
1676 Expand_At_End_Handler
1677 (Handled_Statement_Sequence (N), Blk);
1687 elsif Is_Array_Type (Typ) then
1689 Actual_Rhs : Node_Id := Rhs;
1692 while Nkind (Actual_Rhs) = N_Type_Conversion
1694 Nkind (Actual_Rhs) = N_Qualified_Expression
1696 Actual_Rhs := Expression (Actual_Rhs);
1699 Expand_Assign_Array (N, Actual_Rhs);
1705 elsif Is_Record_Type (Typ) then
1706 Expand_Assign_Record (N);
1709 -- Scalar types. This is where we perform the processing related
1710 -- to the requirements of (RM 13.9.1(9-11)) concerning the handling
1711 -- of invalid scalar values.
1713 elsif Is_Scalar_Type (Typ) then
1715 -- Case where right side is known valid
1717 if Expr_Known_Valid (Rhs) then
1719 -- Here the right side is valid, so it is fine. The case to
1720 -- deal with is when the left side is a local variable reference
1721 -- whose value is not currently known to be valid. If this is
1722 -- the case, and the assignment appears in an unconditional
1723 -- context, then we can mark the left side as now being valid.
1725 if Is_Local_Variable_Reference (Lhs)
1726 and then not Is_Known_Valid (Entity (Lhs))
1727 and then In_Unconditional_Context (N)
1729 Set_Is_Known_Valid (Entity (Lhs), True);
1732 -- Case where right side may be invalid in the sense of the RM
1733 -- reference above. The RM does not require that we check for
1734 -- the validity on an assignment, but it does require that the
1735 -- assignment of an invalid value not cause erroneous behavior.
1737 -- The general approach in GNAT is to use the Is_Known_Valid flag
1738 -- to avoid the need for validity checking on assignments. However
1739 -- in some cases, we have to do validity checking in order to make
1740 -- sure that the setting of this flag is correct.
1743 -- Validate right side if we are validating copies
1745 if Validity_Checks_On
1746 and then Validity_Check_Copies
1750 -- We can propagate this to the left side where appropriate
1752 if Is_Local_Variable_Reference (Lhs)
1753 and then not Is_Known_Valid (Entity (Lhs))
1754 and then In_Unconditional_Context (N)
1756 Set_Is_Known_Valid (Entity (Lhs), True);
1759 -- Otherwise check to see what should be done
1761 -- If left side is a local variable, then we just set its
1762 -- flag to indicate that its value may no longer be valid,
1763 -- since we are copying a potentially invalid value.
1765 elsif Is_Local_Variable_Reference (Lhs) then
1766 Set_Is_Known_Valid (Entity (Lhs), False);
1768 -- Check for case of a nonlocal variable on the left side
1769 -- which is currently known to be valid. In this case, we
1770 -- simply ensure that the right side is valid. We only play
1771 -- the game of copying validity status for local variables,
1772 -- since we are doing this statically, not by tracing the
1775 elsif Is_Entity_Name (Lhs)
1776 and then Is_Known_Valid (Entity (Lhs))
1778 -- Note that the Ensure_Valid call is ignored if the
1779 -- Validity_Checking mode is set to none so we do not
1780 -- need to worry about that case here.
1784 -- In all other cases, we can safely copy an invalid value
1785 -- without worrying about the status of the left side. Since
1786 -- it is not a variable reference it will not be considered
1787 -- as being known to be valid in any case.
1795 -- Defend against invalid subscripts on left side if we are in
1796 -- standard validity checking mode. No need to do this if we
1797 -- are checking all subscripts.
1799 if Validity_Checks_On
1800 and then Validity_Check_Default
1801 and then not Validity_Check_Subscripts
1803 Check_Valid_Lvalue_Subscripts (Lhs);
1807 when RE_Not_Available =>
1809 end Expand_N_Assignment_Statement;
1811 ------------------------------
1812 -- Expand_N_Block_Statement --
1813 ------------------------------
1815 -- Encode entity names defined in block statement
1817 procedure Expand_N_Block_Statement (N : Node_Id) is
1819 Qualify_Entity_Names (N);
1820 end Expand_N_Block_Statement;
1822 -----------------------------
1823 -- Expand_N_Case_Statement --
1824 -----------------------------
1826 procedure Expand_N_Case_Statement (N : Node_Id) is
1827 Loc : constant Source_Ptr := Sloc (N);
1828 Expr : constant Node_Id := Expression (N);
1836 -- Check for the situation where we know at compile time which
1837 -- branch will be taken
1839 if Compile_Time_Known_Value (Expr) then
1840 Alt := Find_Static_Alternative (N);
1842 -- Move the statements from this alternative after the case
1843 -- statement. They are already analyzed, so will be skipped
1846 Insert_List_After (N, Statements (Alt));
1848 -- That leaves the case statement as a shell. The alternative
1849 -- that will be executed is reset to a null list. So now we can
1850 -- kill the entire case statement.
1852 Kill_Dead_Code (Expression (N));
1853 Kill_Dead_Code (Alternatives (N));
1854 Rewrite (N, Make_Null_Statement (Loc));
1858 -- Here if the choice is not determined at compile time
1861 Last_Alt : constant Node_Id := Last (Alternatives (N));
1863 Others_Present : Boolean;
1864 Others_Node : Node_Id;
1866 Then_Stms : List_Id;
1867 Else_Stms : List_Id;
1870 if Nkind (First (Discrete_Choices (Last_Alt))) = N_Others_Choice then
1871 Others_Present := True;
1872 Others_Node := Last_Alt;
1874 Others_Present := False;
1877 -- First step is to worry about possible invalid argument. The RM
1878 -- requires (RM 5.4(13)) that if the result is invalid (e.g. it is
1879 -- outside the base range), then Constraint_Error must be raised.
1881 -- Case of validity check required (validity checks are on, the
1882 -- expression is not known to be valid, and the case statement
1883 -- comes from source -- no need to validity check internally
1884 -- generated case statements).
1886 if Validity_Check_Default then
1887 Ensure_Valid (Expr);
1890 -- If there is only a single alternative, just replace it with
1891 -- the sequence of statements since obviously that is what is
1892 -- going to be executed in all cases.
1894 Len := List_Length (Alternatives (N));
1897 -- We still need to evaluate the expression if it has any
1900 Remove_Side_Effects (Expression (N));
1902 Insert_List_After (N, Statements (First (Alternatives (N))));
1904 -- That leaves the case statement as a shell. The alternative
1905 -- that will be executed is reset to a null list. So now we can
1906 -- kill the entire case statement.
1908 Kill_Dead_Code (Expression (N));
1909 Rewrite (N, Make_Null_Statement (Loc));
1913 -- An optimization. If there are only two alternatives, and only
1914 -- a single choice, then rewrite the whole case statement as an
1915 -- if statement, since this can result in susbequent optimizations.
1916 -- This helps not only with case statements in the source of a
1917 -- simple form, but also with generated code (discriminant check
1918 -- functions in particular)
1921 Chlist := Discrete_Choices (First (Alternatives (N)));
1923 if List_Length (Chlist) = 1 then
1924 Choice := First (Chlist);
1926 Then_Stms := Statements (First (Alternatives (N)));
1927 Else_Stms := Statements (Last (Alternatives (N)));
1929 -- For TRUE, generate "expression", not expression = true
1931 if Nkind (Choice) = N_Identifier
1932 and then Entity (Choice) = Standard_True
1934 Cond := Expression (N);
1936 -- For FALSE, generate "expression" and switch then/else
1938 elsif Nkind (Choice) = N_Identifier
1939 and then Entity (Choice) = Standard_False
1941 Cond := Expression (N);
1942 Else_Stms := Statements (First (Alternatives (N)));
1943 Then_Stms := Statements (Last (Alternatives (N)));
1945 -- For a range, generate "expression in range"
1947 elsif Nkind (Choice) = N_Range
1948 or else (Nkind (Choice) = N_Attribute_Reference
1949 and then Attribute_Name (Choice) = Name_Range)
1950 or else (Is_Entity_Name (Choice)
1951 and then Is_Type (Entity (Choice)))
1952 or else Nkind (Choice) = N_Subtype_Indication
1956 Left_Opnd => Expression (N),
1957 Right_Opnd => Relocate_Node (Choice));
1959 -- For any other subexpression "expression = value"
1964 Left_Opnd => Expression (N),
1965 Right_Opnd => Relocate_Node (Choice));
1968 -- Now rewrite the case as an IF
1971 Make_If_Statement (Loc,
1973 Then_Statements => Then_Stms,
1974 Else_Statements => Else_Stms));
1980 -- If the last alternative is not an Others choice, replace it
1981 -- with an N_Others_Choice. Note that we do not bother to call
1982 -- Analyze on the modified case statement, since it's only effect
1983 -- would be to compute the contents of the Others_Discrete_Choices
1984 -- which is not needed by the back end anyway.
1986 -- The reason we do this is that the back end always needs some
1987 -- default for a switch, so if we have not supplied one in the
1988 -- processing above for validity checking, then we need to
1991 if not Others_Present then
1992 Others_Node := Make_Others_Choice (Sloc (Last_Alt));
1993 Set_Others_Discrete_Choices
1994 (Others_Node, Discrete_Choices (Last_Alt));
1995 Set_Discrete_Choices (Last_Alt, New_List (Others_Node));
1998 end Expand_N_Case_Statement;
2000 -----------------------------
2001 -- Expand_N_Exit_Statement --
2002 -----------------------------
2004 -- The only processing required is to deal with a possible C/Fortran
2005 -- boolean value used as the condition for the exit statement.
2007 procedure Expand_N_Exit_Statement (N : Node_Id) is
2009 Adjust_Condition (Condition (N));
2010 end Expand_N_Exit_Statement;
2012 -----------------------------
2013 -- Expand_N_Goto_Statement --
2014 -----------------------------
2016 -- Add poll before goto if polling active
2018 procedure Expand_N_Goto_Statement (N : Node_Id) is
2020 Generate_Poll_Call (N);
2021 end Expand_N_Goto_Statement;
2023 ---------------------------
2024 -- Expand_N_If_Statement --
2025 ---------------------------
2027 -- First we deal with the case of C and Fortran convention boolean
2028 -- values, with zero/non-zero semantics.
2030 -- Second, we deal with the obvious rewriting for the cases where the
2031 -- condition of the IF is known at compile time to be True or False.
2033 -- Third, we remove elsif parts which have non-empty Condition_Actions
2034 -- and rewrite as independent if statements. For example:
2045 -- <<condition actions of y>>
2051 -- This rewriting is needed if at least one elsif part has a non-empty
2052 -- Condition_Actions list. We also do the same processing if there is
2053 -- a constant condition in an elsif part (in conjunction with the first
2054 -- processing step mentioned above, for the recursive call made to deal
2055 -- with the created inner if, this deals with properly optimizing the
2056 -- cases of constant elsif conditions).
2058 procedure Expand_N_If_Statement (N : Node_Id) is
2059 Loc : constant Source_Ptr := Sloc (N);
2065 Adjust_Condition (Condition (N));
2067 -- The following loop deals with constant conditions for the IF. We
2068 -- need a loop because as we eliminate False conditions, we grab the
2069 -- first elsif condition and use it as the primary condition.
2071 while Compile_Time_Known_Value (Condition (N)) loop
2073 -- If condition is True, we can simply rewrite the if statement
2074 -- now by replacing it by the series of then statements.
2076 if Is_True (Expr_Value (Condition (N))) then
2078 -- All the else parts can be killed
2080 Kill_Dead_Code (Elsif_Parts (N));
2081 Kill_Dead_Code (Else_Statements (N));
2083 Hed := Remove_Head (Then_Statements (N));
2084 Insert_List_After (N, Then_Statements (N));
2088 -- If condition is False, then we can delete the condition and
2089 -- the Then statements
2092 -- We do not delete the condition if constant condition
2093 -- warnings are enabled, since otherwise we end up deleting
2094 -- the desired warning. Of course the backend will get rid
2095 -- of this True/False test anyway, so nothing is lost here.
2097 if not Constant_Condition_Warnings then
2098 Kill_Dead_Code (Condition (N));
2101 Kill_Dead_Code (Then_Statements (N));
2103 -- If there are no elsif statements, then we simply replace
2104 -- the entire if statement by the sequence of else statements.
2106 if No (Elsif_Parts (N)) then
2108 if No (Else_Statements (N))
2109 or else Is_Empty_List (Else_Statements (N))
2112 Make_Null_Statement (Sloc (N)));
2115 Hed := Remove_Head (Else_Statements (N));
2116 Insert_List_After (N, Else_Statements (N));
2122 -- If there are elsif statements, the first of them becomes
2123 -- the if/then section of the rebuilt if statement This is
2124 -- the case where we loop to reprocess this copied condition.
2127 Hed := Remove_Head (Elsif_Parts (N));
2128 Insert_Actions (N, Condition_Actions (Hed));
2129 Set_Condition (N, Condition (Hed));
2130 Set_Then_Statements (N, Then_Statements (Hed));
2132 if Is_Empty_List (Elsif_Parts (N)) then
2133 Set_Elsif_Parts (N, No_List);
2139 -- Loop through elsif parts, dealing with constant conditions and
2140 -- possible expression actions that are present.
2142 if Present (Elsif_Parts (N)) then
2143 E := First (Elsif_Parts (N));
2144 while Present (E) loop
2145 Adjust_Condition (Condition (E));
2147 -- If there are condition actions, then we rewrite the if
2148 -- statement as indicated above. We also do the same rewrite
2149 -- if the condition is True or False. The further processing
2150 -- of this constant condition is then done by the recursive
2151 -- call to expand the newly created if statement
2153 if Present (Condition_Actions (E))
2154 or else Compile_Time_Known_Value (Condition (E))
2156 -- Note this is not an implicit if statement, since it is
2157 -- part of an explicit if statement in the source (or of an
2158 -- implicit if statement that has already been tested).
2161 Make_If_Statement (Sloc (E),
2162 Condition => Condition (E),
2163 Then_Statements => Then_Statements (E),
2164 Elsif_Parts => No_List,
2165 Else_Statements => Else_Statements (N));
2167 -- Elsif parts for new if come from remaining elsif's of parent
2169 while Present (Next (E)) loop
2170 if No (Elsif_Parts (New_If)) then
2171 Set_Elsif_Parts (New_If, New_List);
2174 Append (Remove_Next (E), Elsif_Parts (New_If));
2177 Set_Else_Statements (N, New_List (New_If));
2179 if Present (Condition_Actions (E)) then
2180 Insert_List_Before (New_If, Condition_Actions (E));
2185 if Is_Empty_List (Elsif_Parts (N)) then
2186 Set_Elsif_Parts (N, No_List);
2192 -- No special processing for that elsif part, move to next
2200 -- Some more optimizations applicable if we still have an IF statement
2202 if Nkind (N) /= N_If_Statement then
2206 -- Another optimization, special cases that can be simplified
2208 -- if expression then
2214 -- can be changed to:
2216 -- return expression;
2220 -- if expression then
2226 -- can be changed to:
2228 -- return not (expression);
2230 if Nkind (N) = N_If_Statement
2231 and then No (Elsif_Parts (N))
2232 and then Present (Else_Statements (N))
2233 and then List_Length (Then_Statements (N)) = 1
2234 and then List_Length (Else_Statements (N)) = 1
2237 Then_Stm : Node_Id := First (Then_Statements (N));
2238 Else_Stm : Node_Id := First (Else_Statements (N));
2241 if Nkind (Then_Stm) = N_Return_Statement
2243 Nkind (Else_Stm) = N_Return_Statement
2246 Then_Expr : constant Node_Id := Expression (Then_Stm);
2247 Else_Expr : constant Node_Id := Expression (Else_Stm);
2250 if Nkind (Then_Expr) = N_Identifier
2252 Nkind (Else_Expr) = N_Identifier
2254 if Entity (Then_Expr) = Standard_True
2255 and then Entity (Else_Expr) = Standard_False
2258 Make_Return_Statement (Loc,
2259 Expression => Relocate_Node (Condition (N))));
2263 elsif Entity (Then_Expr) = Standard_False
2264 and then Entity (Else_Expr) = Standard_True
2267 Make_Return_Statement (Loc,
2270 Right_Opnd => Relocate_Node (Condition (N)))));
2279 end Expand_N_If_Statement;
2281 -----------------------------
2282 -- Expand_N_Loop_Statement --
2283 -----------------------------
2285 -- 1. Deal with while condition for C/Fortran boolean
2286 -- 2. Deal with loops with a non-standard enumeration type range
2287 -- 3. Deal with while loops where Condition_Actions is set
2288 -- 4. Insert polling call if required
2290 procedure Expand_N_Loop_Statement (N : Node_Id) is
2291 Loc : constant Source_Ptr := Sloc (N);
2292 Isc : constant Node_Id := Iteration_Scheme (N);
2295 if Present (Isc) then
2296 Adjust_Condition (Condition (Isc));
2299 if Is_Non_Empty_List (Statements (N)) then
2300 Generate_Poll_Call (First (Statements (N)));
2307 -- Handle the case where we have a for loop with the range type being
2308 -- an enumeration type with non-standard representation. In this case
2311 -- for x in [reverse] a .. b loop
2317 -- for xP in [reverse] integer
2318 -- range etype'Pos (a) .. etype'Pos (b) loop
2320 -- x : constant etype := Pos_To_Rep (xP);
2326 if Present (Loop_Parameter_Specification (Isc)) then
2328 LPS : constant Node_Id := Loop_Parameter_Specification (Isc);
2329 Loop_Id : constant Entity_Id := Defining_Identifier (LPS);
2330 Ltype : constant Entity_Id := Etype (Loop_Id);
2331 Btype : constant Entity_Id := Base_Type (Ltype);
2336 if not Is_Enumeration_Type (Btype)
2337 or else No (Enum_Pos_To_Rep (Btype))
2343 Make_Defining_Identifier (Loc,
2344 Chars => New_External_Name (Chars (Loop_Id), 'P'));
2346 -- If the type has a contiguous representation, successive
2347 -- values can be generated as offsets from the first literal.
2349 if Has_Contiguous_Rep (Btype) then
2351 Unchecked_Convert_To (Btype,
2354 Make_Integer_Literal (Loc,
2355 Enumeration_Rep (First_Literal (Btype))),
2356 Right_Opnd => New_Reference_To (New_Id, Loc)));
2358 -- Use the constructed array Enum_Pos_To_Rep.
2361 Make_Indexed_Component (Loc,
2362 Prefix => New_Reference_To (Enum_Pos_To_Rep (Btype), Loc),
2363 Expressions => New_List (New_Reference_To (New_Id, Loc)));
2367 Make_Loop_Statement (Loc,
2368 Identifier => Identifier (N),
2371 Make_Iteration_Scheme (Loc,
2372 Loop_Parameter_Specification =>
2373 Make_Loop_Parameter_Specification (Loc,
2374 Defining_Identifier => New_Id,
2375 Reverse_Present => Reverse_Present (LPS),
2377 Discrete_Subtype_Definition =>
2378 Make_Subtype_Indication (Loc,
2381 New_Reference_To (Standard_Natural, Loc),
2384 Make_Range_Constraint (Loc,
2389 Make_Attribute_Reference (Loc,
2391 New_Reference_To (Btype, Loc),
2393 Attribute_Name => Name_Pos,
2395 Expressions => New_List (
2397 (Type_Low_Bound (Ltype)))),
2400 Make_Attribute_Reference (Loc,
2402 New_Reference_To (Btype, Loc),
2404 Attribute_Name => Name_Pos,
2406 Expressions => New_List (
2408 (Type_High_Bound (Ltype))))))))),
2410 Statements => New_List (
2411 Make_Block_Statement (Loc,
2412 Declarations => New_List (
2413 Make_Object_Declaration (Loc,
2414 Defining_Identifier => Loop_Id,
2415 Constant_Present => True,
2416 Object_Definition => New_Reference_To (Ltype, Loc),
2417 Expression => Expr)),
2419 Handled_Statement_Sequence =>
2420 Make_Handled_Sequence_Of_Statements (Loc,
2421 Statements => Statements (N)))),
2423 End_Label => End_Label (N)));
2427 -- Second case, if we have a while loop with Condition_Actions set,
2428 -- then we change it into a plain loop:
2437 -- <<condition actions>>
2443 and then Present (Condition_Actions (Isc))
2450 Make_Exit_Statement (Sloc (Condition (Isc)),
2452 Make_Op_Not (Sloc (Condition (Isc)),
2453 Right_Opnd => Condition (Isc)));
2455 Prepend (ES, Statements (N));
2456 Insert_List_Before (ES, Condition_Actions (Isc));
2458 -- This is not an implicit loop, since it is generated in
2459 -- response to the loop statement being processed. If this
2460 -- is itself implicit, the restriction has already been
2461 -- checked. If not, it is an explicit loop.
2464 Make_Loop_Statement (Sloc (N),
2465 Identifier => Identifier (N),
2466 Statements => Statements (N),
2467 End_Label => End_Label (N)));
2472 end Expand_N_Loop_Statement;
2474 -------------------------------
2475 -- Expand_N_Return_Statement --
2476 -------------------------------
2478 procedure Expand_N_Return_Statement (N : Node_Id) is
2479 Loc : constant Source_Ptr := Sloc (N);
2480 Exp : constant Node_Id := Expression (N);
2484 Scope_Id : Entity_Id;
2488 Goto_Stat : Node_Id;
2491 Return_Type : Entity_Id;
2492 Result_Exp : Node_Id;
2493 Result_Id : Entity_Id;
2494 Result_Obj : Node_Id;
2497 -- Case where returned expression is present
2499 if Present (Exp) then
2501 -- Always normalize C/Fortran boolean result. This is not always
2502 -- necessary, but it seems a good idea to minimize the passing
2503 -- around of non-normalized values, and in any case this handles
2504 -- the processing of barrier functions for protected types, which
2505 -- turn the condition into a return statement.
2507 Exptyp := Etype (Exp);
2509 if Is_Boolean_Type (Exptyp)
2510 and then Nonzero_Is_True (Exptyp)
2512 Adjust_Condition (Exp);
2513 Adjust_Result_Type (Exp, Exptyp);
2516 -- Do validity check if enabled for returns
2518 if Validity_Checks_On
2519 and then Validity_Check_Returns
2525 -- Find relevant enclosing scope from which return is returning
2527 Cur_Idx := Scope_Stack.Last;
2529 Scope_Id := Scope_Stack.Table (Cur_Idx).Entity;
2531 if Ekind (Scope_Id) /= E_Block
2532 and then Ekind (Scope_Id) /= E_Loop
2537 Cur_Idx := Cur_Idx - 1;
2538 pragma Assert (Cur_Idx >= 0);
2543 Kind := Ekind (Scope_Id);
2545 -- If it is a return from procedures do no extra steps.
2547 if Kind = E_Procedure or else Kind = E_Generic_Procedure then
2551 pragma Assert (Is_Entry (Scope_Id));
2553 -- Look at the enclosing block to see whether the return is from
2554 -- an accept statement or an entry body.
2556 for J in reverse 0 .. Cur_Idx loop
2557 Scope_Id := Scope_Stack.Table (J).Entity;
2558 exit when Is_Concurrent_Type (Scope_Id);
2561 -- If it is a return from accept statement it should be expanded
2562 -- as a call to RTS Complete_Rendezvous and a goto to the end of
2565 -- (cf : Expand_N_Accept_Statement, Expand_N_Selective_Accept,
2566 -- Expand_N_Accept_Alternative in exp_ch9.adb)
2568 if Is_Task_Type (Scope_Id) then
2570 Call := (Make_Procedure_Call_Statement (Loc,
2571 Name => New_Reference_To
2572 (RTE (RE_Complete_Rendezvous), Loc)));
2573 Insert_Before (N, Call);
2574 -- why not insert actions here???
2577 Acc_Stat := Parent (N);
2578 while Nkind (Acc_Stat) /= N_Accept_Statement loop
2579 Acc_Stat := Parent (Acc_Stat);
2582 Lab_Node := Last (Statements
2583 (Handled_Statement_Sequence (Acc_Stat)));
2585 Goto_Stat := Make_Goto_Statement (Loc,
2586 Name => New_Occurrence_Of
2587 (Entity (Identifier (Lab_Node)), Loc));
2589 Set_Analyzed (Goto_Stat);
2591 Rewrite (N, Goto_Stat);
2594 -- If it is a return from an entry body, put a Complete_Entry_Body
2595 -- call in front of the return.
2597 elsif Is_Protected_Type (Scope_Id) then
2600 Make_Procedure_Call_Statement (Loc,
2601 Name => New_Reference_To
2602 (RTE (RE_Complete_Entry_Body), Loc),
2603 Parameter_Associations => New_List
2604 (Make_Attribute_Reference (Loc,
2608 (Corresponding_Body (Parent (Scope_Id))),
2610 Attribute_Name => Name_Unchecked_Access)));
2612 Insert_Before (N, Call);
2621 Return_Type := Etype (Scope_Id);
2622 Utyp := Underlying_Type (Return_Type);
2624 -- Check the result expression of a scalar function against
2625 -- the subtype of the function by inserting a conversion.
2626 -- This conversion must eventually be performed for other
2627 -- classes of types, but for now it's only done for scalars.
2630 if Is_Scalar_Type (T) then
2631 Rewrite (Exp, Convert_To (Return_Type, Exp));
2635 -- Implement the rules of 6.5(8-10), which require a tag check in
2636 -- the case of a limited tagged return type, and tag reassignment
2637 -- for nonlimited tagged results. These actions are needed when
2638 -- the return type is a specific tagged type and the result
2639 -- expression is a conversion or a formal parameter, because in
2640 -- that case the tag of the expression might differ from the tag
2641 -- of the specific result type.
2643 if Is_Tagged_Type (Utyp)
2644 and then not Is_Class_Wide_Type (Utyp)
2645 and then (Nkind (Exp) = N_Type_Conversion
2646 or else Nkind (Exp) = N_Unchecked_Type_Conversion
2647 or else (Is_Entity_Name (Exp)
2648 and then Ekind (Entity (Exp)) in Formal_Kind))
2650 -- When the return type is limited, perform a check that the
2651 -- tag of the result is the same as the tag of the return type.
2653 if Is_Limited_Type (Return_Type) then
2655 Make_Raise_Constraint_Error (Loc,
2659 Make_Selected_Component (Loc,
2660 Prefix => Duplicate_Subexpr (Exp),
2662 New_Reference_To (Tag_Component (Utyp), Loc)),
2664 Unchecked_Convert_To (RTE (RE_Tag),
2666 (Access_Disp_Table (Base_Type (Utyp)), Loc))),
2667 Reason => CE_Tag_Check_Failed));
2669 -- If the result type is a specific nonlimited tagged type,
2670 -- then we have to ensure that the tag of the result is that
2671 -- of the result type. This is handled by making a copy of the
2672 -- expression in the case where it might have a different tag,
2673 -- namely when the expression is a conversion or a formal
2674 -- parameter. We create a new object of the result type and
2675 -- initialize it from the expression, which will implicitly
2676 -- force the tag to be set appropriately.
2680 Make_Defining_Identifier (Loc, New_Internal_Name ('R'));
2681 Result_Exp := New_Reference_To (Result_Id, Loc);
2684 Make_Object_Declaration (Loc,
2685 Defining_Identifier => Result_Id,
2686 Object_Definition => New_Reference_To (Return_Type, Loc),
2687 Constant_Present => True,
2688 Expression => Relocate_Node (Exp));
2690 Set_Assignment_OK (Result_Obj);
2691 Insert_Action (Exp, Result_Obj);
2693 Rewrite (Exp, Result_Exp);
2694 Analyze_And_Resolve (Exp, Return_Type);
2698 -- Deal with returning variable length objects and controlled types
2700 -- Nothing to do if we are returning by reference, or this is not
2701 -- a type that requires special processing (indicated by the fact
2702 -- that it requires a cleanup scope for the secondary stack case)
2704 if Is_Return_By_Reference_Type (T)
2705 or else not Requires_Transient_Scope (Return_Type)
2709 -- Case of secondary stack not used
2711 elsif Function_Returns_With_DSP (Scope_Id) then
2713 -- Here what we need to do is to always return by reference, since
2714 -- we will return with the stack pointer depressed. We may need to
2715 -- do a copy to a local temporary before doing this return.
2717 No_Secondary_Stack_Case : declare
2718 Local_Copy_Required : Boolean := False;
2719 -- Set to True if a local copy is required
2721 Copy_Ent : Entity_Id;
2722 -- Used for the target entity if a copy is required
2725 -- Declaration used to create copy if needed
2727 procedure Test_Copy_Required (Expr : Node_Id);
2728 -- Determines if Expr represents a return value for which a
2729 -- copy is required. More specifically, a copy is not required
2730 -- if Expr represents an object or component of an object that
2731 -- is either in the local subprogram frame, or is constant.
2732 -- If a copy is required, then Local_Copy_Required is set True.
2734 ------------------------
2735 -- Test_Copy_Required --
2736 ------------------------
2738 procedure Test_Copy_Required (Expr : Node_Id) is
2742 -- If component, test prefix (object containing component)
2744 if Nkind (Expr) = N_Indexed_Component
2746 Nkind (Expr) = N_Selected_Component
2748 Test_Copy_Required (Prefix (Expr));
2751 -- See if we have an entity name
2753 elsif Is_Entity_Name (Expr) then
2754 Ent := Entity (Expr);
2756 -- Constant entity is always OK, no copy required
2758 if Ekind (Ent) = E_Constant then
2761 -- No copy required for local variable
2763 elsif Ekind (Ent) = E_Variable
2764 and then Scope (Ent) = Current_Subprogram
2770 -- All other cases require a copy
2772 Local_Copy_Required := True;
2773 end Test_Copy_Required;
2775 -- Start of processing for No_Secondary_Stack_Case
2778 -- No copy needed if result is from a function call.
2779 -- In this case the result is already being returned by
2780 -- reference with the stack pointer depressed.
2782 -- To make up for a gcc 2.8.1 deficiency (???), we perform
2783 -- the copy for array types if the constrained status of the
2784 -- target type is different from that of the expression.
2786 if Requires_Transient_Scope (T)
2788 (not Is_Array_Type (T)
2789 or else Is_Constrained (T) = Is_Constrained (Return_Type)
2790 or else Controlled_Type (T))
2791 and then Nkind (Exp) = N_Function_Call
2795 -- We always need a local copy for a controlled type, since
2796 -- we are required to finalize the local value before return.
2797 -- The copy will automatically include the required finalize.
2798 -- Moreover, gigi cannot make this copy, since we need special
2799 -- processing to ensure proper behavior for finalization.
2801 -- Note: the reason we are returning with a depressed stack
2802 -- pointer in the controlled case (even if the type involved
2803 -- is constrained) is that we must make a local copy to deal
2804 -- properly with the requirement that the local result be
2807 elsif Controlled_Type (Utyp) then
2809 Make_Defining_Identifier (Loc,
2810 Chars => New_Internal_Name ('R'));
2812 -- Build declaration to do the copy, and insert it, setting
2813 -- Assignment_OK, because we may be copying a limited type.
2814 -- In addition we set the special flag to inhibit finalize
2815 -- attachment if this is a controlled type (since this attach
2816 -- must be done by the caller, otherwise if we attach it here
2817 -- we will finalize the returned result prematurely).
2820 Make_Object_Declaration (Loc,
2821 Defining_Identifier => Copy_Ent,
2822 Object_Definition => New_Occurrence_Of (Return_Type, Loc),
2823 Expression => Relocate_Node (Exp));
2825 Set_Assignment_OK (Decl);
2826 Set_Delay_Finalize_Attach (Decl);
2827 Insert_Action (N, Decl);
2829 -- Now the actual return uses the copied value
2831 Rewrite (Exp, New_Occurrence_Of (Copy_Ent, Loc));
2832 Analyze_And_Resolve (Exp, Return_Type);
2834 -- Since we have made the copy, gigi does not have to, so
2835 -- we set the By_Ref flag to prevent another copy being made.
2839 -- Non-controlled cases
2842 Test_Copy_Required (Exp);
2844 -- If a local copy is required, then gigi will make the
2845 -- copy, otherwise, we can return the result directly,
2846 -- so set By_Ref to suppress the gigi copy.
2848 if not Local_Copy_Required then
2852 end No_Secondary_Stack_Case;
2854 -- Here if secondary stack is used
2857 -- Make sure that no surrounding block will reclaim the
2858 -- secondary-stack on which we are going to put the result.
2859 -- Not only may this introduce secondary stack leaks but worse,
2860 -- if the reclamation is done too early, then the result we are
2861 -- returning may get clobbered. See example in 7417-003.
2864 S : Entity_Id := Current_Scope;
2867 while Ekind (S) = E_Block or else Ekind (S) = E_Loop loop
2868 Set_Sec_Stack_Needed_For_Return (S, True);
2869 S := Enclosing_Dynamic_Scope (S);
2873 -- Optimize the case where the result is a function call. In this
2874 -- case either the result is already on the secondary stack, or is
2875 -- already being returned with the stack pointer depressed and no
2876 -- further processing is required except to set the By_Ref flag to
2877 -- ensure that gigi does not attempt an extra unnecessary copy.
2878 -- (actually not just unnecessary but harmfully wrong in the case
2879 -- of a controlled type, where gigi does not know how to do a copy).
2880 -- To make up for a gcc 2.8.1 deficiency (???), we perform
2881 -- the copy for array types if the constrained status of the
2882 -- target type is different from that of the expression.
2884 if Requires_Transient_Scope (T)
2886 (not Is_Array_Type (T)
2887 or else Is_Constrained (T) = Is_Constrained (Return_Type)
2888 or else Controlled_Type (T))
2889 and then Nkind (Exp) = N_Function_Call
2893 -- For controlled types, do the allocation on the sec-stack
2894 -- manually in order to call adjust at the right time
2895 -- type Anon1 is access Return_Type;
2896 -- for Anon1'Storage_pool use ss_pool;
2897 -- Anon2 : anon1 := new Return_Type'(expr);
2898 -- return Anon2.all;
2900 elsif Controlled_Type (Utyp) then
2902 Loc : constant Source_Ptr := Sloc (N);
2903 Temp : constant Entity_Id :=
2904 Make_Defining_Identifier (Loc,
2905 Chars => New_Internal_Name ('R'));
2906 Acc_Typ : constant Entity_Id :=
2907 Make_Defining_Identifier (Loc,
2908 Chars => New_Internal_Name ('A'));
2909 Alloc_Node : Node_Id;
2912 Set_Ekind (Acc_Typ, E_Access_Type);
2914 Set_Associated_Storage_Pool (Acc_Typ, RTE (RE_SS_Pool));
2917 Make_Allocator (Loc,
2919 Make_Qualified_Expression (Loc,
2920 Subtype_Mark => New_Reference_To (Etype (Exp), Loc),
2921 Expression => Relocate_Node (Exp)));
2923 Insert_List_Before_And_Analyze (N, New_List (
2924 Make_Full_Type_Declaration (Loc,
2925 Defining_Identifier => Acc_Typ,
2927 Make_Access_To_Object_Definition (Loc,
2928 Subtype_Indication =>
2929 New_Reference_To (Return_Type, Loc))),
2931 Make_Object_Declaration (Loc,
2932 Defining_Identifier => Temp,
2933 Object_Definition => New_Reference_To (Acc_Typ, Loc),
2934 Expression => Alloc_Node)));
2937 Make_Explicit_Dereference (Loc,
2938 Prefix => New_Reference_To (Temp, Loc)));
2940 Analyze_And_Resolve (Exp, Return_Type);
2943 -- Otherwise use the gigi mechanism to allocate result on the
2947 Set_Storage_Pool (N, RTE (RE_SS_Pool));
2949 -- If we are generating code for the Java VM do not use
2950 -- SS_Allocate since everything is heap-allocated anyway.
2953 Set_Procedure_To_Call (N, RTE (RE_SS_Allocate));
2959 when RE_Not_Available =>
2961 end Expand_N_Return_Statement;
2963 ------------------------------
2964 -- Make_Tag_Ctrl_Assignment --
2965 ------------------------------
2967 function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id is
2968 Loc : constant Source_Ptr := Sloc (N);
2969 L : constant Node_Id := Name (N);
2970 T : constant Entity_Id := Underlying_Type (Etype (L));
2972 Ctrl_Act : constant Boolean := Controlled_Type (T)
2973 and then not No_Ctrl_Actions (N);
2975 Save_Tag : constant Boolean := Is_Tagged_Type (T)
2976 and then not No_Ctrl_Actions (N)
2977 and then not Java_VM;
2978 -- Tags are not saved and restored when Java_VM because JVM tags
2979 -- are represented implicitly in objects.
2982 Tag_Tmp : Entity_Id;
2983 Prev_Tmp : Entity_Id;
2984 Next_Tmp : Entity_Id;
2986 Ctrl_Ref2 : Node_Id := Empty;
2987 Prev_Tmp2 : Entity_Id := Empty; -- prevent warning
2988 Next_Tmp2 : Entity_Id := Empty; -- prevent warning
2993 -- Finalize the target of the assignment when controlled.
2994 -- We have two exceptions here:
2996 -- 1. If we are in an init proc since it is an initialization
2997 -- more than an assignment
2999 -- 2. If the left-hand side is a temporary that was not initialized
3000 -- (or the parent part of a temporary since it is the case in
3001 -- extension aggregates). Such a temporary does not come from
3002 -- source. We must examine the original node for the prefix, because
3003 -- it may be a component of an entry formal, in which case it has
3004 -- been rewritten and does not appear to come from source either.
3006 -- Case of init proc
3008 if not Ctrl_Act then
3011 -- The left hand side is an uninitialized temporary
3013 elsif Nkind (L) = N_Type_Conversion
3014 and then Is_Entity_Name (Expression (L))
3015 and then No_Initialization (Parent (Entity (Expression (L))))
3019 Append_List_To (Res,
3021 Ref => Duplicate_Subexpr_No_Checks (L),
3023 With_Detach => New_Reference_To (Standard_False, Loc)));
3026 Next_Tmp := Make_Defining_Identifier (Loc, New_Internal_Name ('C'));
3028 -- Save the Tag in a local variable Tag_Tmp
3032 Make_Defining_Identifier (Loc, New_Internal_Name ('A'));
3035 Make_Object_Declaration (Loc,
3036 Defining_Identifier => Tag_Tmp,
3037 Object_Definition => New_Reference_To (RTE (RE_Tag), Loc),
3039 Make_Selected_Component (Loc,
3040 Prefix => Duplicate_Subexpr_No_Checks (L),
3041 Selector_Name => New_Reference_To (Tag_Component (T), Loc))));
3043 -- Otherwise Tag_Tmp not used
3049 -- Save the Finalization Pointers in local variables Prev_Tmp and
3050 -- Next_Tmp. For objects with Has_Controlled_Component set, these
3051 -- pointers are in the Record_Controller and if it is also
3052 -- Is_Controlled, we need to save the object pointers as well.
3055 Ctrl_Ref := Duplicate_Subexpr_No_Checks (L);
3057 if Has_Controlled_Component (T) then
3059 Make_Selected_Component (Loc,
3062 New_Reference_To (Controller_Component (T), Loc));
3064 if Is_Controlled (T) then
3065 Ctrl_Ref2 := Duplicate_Subexpr_No_Checks (L);
3069 Prev_Tmp := Make_Defining_Identifier (Loc, New_Internal_Name ('B'));
3072 Make_Object_Declaration (Loc,
3073 Defining_Identifier => Prev_Tmp,
3075 Object_Definition =>
3076 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc),
3079 Make_Selected_Component (Loc,
3081 Unchecked_Convert_To (RTE (RE_Finalizable), Ctrl_Ref),
3082 Selector_Name => Make_Identifier (Loc, Name_Prev))));
3084 Next_Tmp := Make_Defining_Identifier (Loc, New_Internal_Name ('C'));
3087 Make_Object_Declaration (Loc,
3088 Defining_Identifier => Next_Tmp,
3090 Object_Definition =>
3091 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc),
3094 Make_Selected_Component (Loc,
3096 Unchecked_Convert_To (RTE (RE_Finalizable),
3097 New_Copy_Tree (Ctrl_Ref)),
3098 Selector_Name => Make_Identifier (Loc, Name_Next))));
3100 if Present (Ctrl_Ref2) then
3102 Make_Defining_Identifier (Loc, New_Internal_Name ('B'));
3105 Make_Object_Declaration (Loc,
3106 Defining_Identifier => Prev_Tmp2,
3108 Object_Definition =>
3109 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc),
3112 Make_Selected_Component (Loc,
3114 Unchecked_Convert_To (RTE (RE_Finalizable), Ctrl_Ref2),
3115 Selector_Name => Make_Identifier (Loc, Name_Prev))));
3118 Make_Defining_Identifier (Loc, New_Internal_Name ('C'));
3121 Make_Object_Declaration (Loc,
3122 Defining_Identifier => Next_Tmp2,
3124 Object_Definition =>
3125 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc),
3128 Make_Selected_Component (Loc,
3130 Unchecked_Convert_To (RTE (RE_Finalizable),
3131 New_Copy_Tree (Ctrl_Ref2)),
3132 Selector_Name => Make_Identifier (Loc, Name_Next))));
3135 -- If not controlled type, then Prev_Tmp and Ctrl_Ref unused
3142 -- Do the Assignment
3144 Append_To (Res, Relocate_Node (N));
3150 Make_Assignment_Statement (Loc,
3152 Make_Selected_Component (Loc,
3153 Prefix => Duplicate_Subexpr_No_Checks (L),
3154 Selector_Name => New_Reference_To (Tag_Component (T), Loc)),
3155 Expression => New_Reference_To (Tag_Tmp, Loc)));
3158 -- Restore the finalization pointers
3162 Make_Assignment_Statement (Loc,
3164 Make_Selected_Component (Loc,
3166 Unchecked_Convert_To (RTE (RE_Finalizable),
3167 New_Copy_Tree (Ctrl_Ref)),
3168 Selector_Name => Make_Identifier (Loc, Name_Prev)),
3169 Expression => New_Reference_To (Prev_Tmp, Loc)));
3172 Make_Assignment_Statement (Loc,
3174 Make_Selected_Component (Loc,
3176 Unchecked_Convert_To (RTE (RE_Finalizable),
3177 New_Copy_Tree (Ctrl_Ref)),
3178 Selector_Name => Make_Identifier (Loc, Name_Next)),
3179 Expression => New_Reference_To (Next_Tmp, Loc)));
3181 if Present (Ctrl_Ref2) then
3183 Make_Assignment_Statement (Loc,
3185 Make_Selected_Component (Loc,
3187 Unchecked_Convert_To (RTE (RE_Finalizable),
3188 New_Copy_Tree (Ctrl_Ref2)),
3189 Selector_Name => Make_Identifier (Loc, Name_Prev)),
3190 Expression => New_Reference_To (Prev_Tmp2, Loc)));
3193 Make_Assignment_Statement (Loc,
3195 Make_Selected_Component (Loc,
3197 Unchecked_Convert_To (RTE (RE_Finalizable),
3198 New_Copy_Tree (Ctrl_Ref2)),
3199 Selector_Name => Make_Identifier (Loc, Name_Next)),
3200 Expression => New_Reference_To (Next_Tmp2, Loc)));
3204 -- Adjust the target after the assignment when controlled. (not in
3205 -- the init proc since it is an initialization more than an
3209 Append_List_To (Res,
3211 Ref => Duplicate_Subexpr_Move_Checks (L),
3213 Flist_Ref => New_Reference_To (RTE (RE_Global_Final_List), Loc),
3214 With_Attach => Make_Integer_Literal (Loc, 0)));
3220 when RE_Not_Available =>
3222 end Make_Tag_Ctrl_Assignment;
3224 ---------------------------------------
3225 -- Maybe_Bit_Aligned_Large_Component --
3226 ---------------------------------------
3228 function Maybe_Bit_Aligned_Large_Component (N : Node_Id) return Boolean is
3232 -- Case of indexed component
3234 when N_Indexed_Component =>
3236 P : constant Node_Id := Prefix (N);
3237 Ptyp : constant Entity_Id := Etype (P);
3240 -- If we know the component size and it is less than 64, then
3241 -- we are definitely OK. The back end always does assignment
3242 -- of misaligned small objects correctly.
3244 if Known_Static_Component_Size (Ptyp)
3245 and then Component_Size (Ptyp) <= 64
3249 -- Otherwise, we need to test the prefix, to see if we are
3250 -- indexing from a possibly unaligned component.
3253 return Maybe_Bit_Aligned_Large_Component (P);
3257 -- Case of selected component
3259 when N_Selected_Component =>
3261 P : constant Node_Id := Prefix (N);
3262 Comp : constant Entity_Id := Entity (Selector_Name (N));
3265 -- If there is no component clause, then we are in the clear
3266 -- since the back end will never misalign a large component
3267 -- unless it is forced to do so. In the clear means we need
3268 -- only the recursive test on the prefix.
3270 if No (Component_Clause (Comp)) then
3271 return Maybe_Bit_Aligned_Large_Component (P);
3273 -- Otherwise we have a component clause, which means that
3274 -- the Esize and Normalized_First_Bit fields are set and
3275 -- contain static values known at compile time.
3278 -- If we know the size is 64 bits or less we are fine
3279 -- since the back end always handles small fields right.
3281 if Esize (Comp) <= 64 then
3284 -- Otherwise if the component is not byte aligned, we
3285 -- know we have the nasty unaligned case.
3287 elsif Normalized_First_Bit (Comp) /= Uint_0
3288 or else Esize (Comp) mod System_Storage_Unit /= Uint_0
3292 -- If we are large and byte aligned, then OK at this level
3293 -- but we still need to test our prefix recursively.
3296 return Maybe_Bit_Aligned_Large_Component (P);
3301 -- If we have neither a record nor array component, it means that
3302 -- we have fallen off the top testing prefixes recursively, and
3303 -- we now have a stand alone object, where we don't have a problem
3309 end Maybe_Bit_Aligned_Large_Component;