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objc/
[official-gcc.git] / gcc / ada / exp_pakd.adb
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1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT COMPILER COMPONENTS --
4 -- --
5 -- E X P _ P A K D --
6 -- --
7 -- B o d y --
8 -- --
9 -- Copyright (C) 1992-2005 Free Software Foundation, Inc. --
10 -- --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 2, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
21 -- --
22 -- GNAT was originally developed by the GNAT team at New York University. --
23 -- Extensive contributions were provided by Ada Core Technologies Inc. --
24 -- --
25 ------------------------------------------------------------------------------
26
27 with Atree; use Atree;
28 with Checks; use Checks;
29 with Einfo; use Einfo;
30 with Exp_Dbug; use Exp_Dbug;
31 with Exp_Util; use Exp_Util;
32 with Nlists; use Nlists;
33 with Nmake; use Nmake;
34 with Rtsfind; use Rtsfind;
35 with Sem; use Sem;
36 with Sem_Ch3; use Sem_Ch3;
37 with Sem_Ch8; use Sem_Ch8;
38 with Sem_Ch13; use Sem_Ch13;
39 with Sem_Eval; use Sem_Eval;
40 with Sem_Res; use Sem_Res;
41 with Sem_Util; use Sem_Util;
42 with Sinfo; use Sinfo;
43 with Snames; use Snames;
44 with Stand; use Stand;
45 with Targparm; use Targparm;
46 with Tbuild; use Tbuild;
47 with Ttypes; use Ttypes;
48 with Uintp; use Uintp;
49
50 package body Exp_Pakd is
51
52 ---------------------------
53 -- Endian Considerations --
54 ---------------------------
55
56 -- As described in the specification, bit numbering in a packed array
57 -- is consistent with bit numbering in a record representation clause,
58 -- and hence dependent on the endianness of the machine:
59
60 -- For little-endian machines, element zero is at the right hand end
61 -- (low order end) of a bit field.
62
63 -- For big-endian machines, element zero is at the left hand end
64 -- (high order end) of a bit field.
65
66 -- The shifts that are used to right justify a field therefore differ
67 -- in the two cases. For the little-endian case, we can simply use the
68 -- bit number (i.e. the element number * element size) as the count for
69 -- a right shift. For the big-endian case, we have to subtract the shift
70 -- count from an appropriate constant to use in the right shift. We use
71 -- rotates instead of shifts (which is necessary in the store case to
72 -- preserve other fields), and we expect that the backend will be able
73 -- to change the right rotate into a left rotate, avoiding the subtract,
74 -- if the architecture provides such an instruction.
75
76 ----------------------------------------------
77 -- Entity Tables for Packed Access Routines --
78 ----------------------------------------------
79
80 -- For the cases of component size = 3,5-7,9-15,17-31,33-63 we call
81 -- library routines. This table is used to obtain the entity for the
82 -- proper routine.
83
84 type E_Array is array (Int range 01 .. 63) of RE_Id;
85
86 -- Array of Bits_nn entities. Note that we do not use library routines
87 -- for the 8-bit and 16-bit cases, but we still fill in the table, using
88 -- entries from System.Unsigned, because we also use this table for
89 -- certain special unchecked conversions in the big-endian case.
90
91 Bits_Id : constant E_Array :=
92 (01 => RE_Bits_1,
93 02 => RE_Bits_2,
94 03 => RE_Bits_03,
95 04 => RE_Bits_4,
96 05 => RE_Bits_05,
97 06 => RE_Bits_06,
98 07 => RE_Bits_07,
99 08 => RE_Unsigned_8,
100 09 => RE_Bits_09,
101 10 => RE_Bits_10,
102 11 => RE_Bits_11,
103 12 => RE_Bits_12,
104 13 => RE_Bits_13,
105 14 => RE_Bits_14,
106 15 => RE_Bits_15,
107 16 => RE_Unsigned_16,
108 17 => RE_Bits_17,
109 18 => RE_Bits_18,
110 19 => RE_Bits_19,
111 20 => RE_Bits_20,
112 21 => RE_Bits_21,
113 22 => RE_Bits_22,
114 23 => RE_Bits_23,
115 24 => RE_Bits_24,
116 25 => RE_Bits_25,
117 26 => RE_Bits_26,
118 27 => RE_Bits_27,
119 28 => RE_Bits_28,
120 29 => RE_Bits_29,
121 30 => RE_Bits_30,
122 31 => RE_Bits_31,
123 32 => RE_Unsigned_32,
124 33 => RE_Bits_33,
125 34 => RE_Bits_34,
126 35 => RE_Bits_35,
127 36 => RE_Bits_36,
128 37 => RE_Bits_37,
129 38 => RE_Bits_38,
130 39 => RE_Bits_39,
131 40 => RE_Bits_40,
132 41 => RE_Bits_41,
133 42 => RE_Bits_42,
134 43 => RE_Bits_43,
135 44 => RE_Bits_44,
136 45 => RE_Bits_45,
137 46 => RE_Bits_46,
138 47 => RE_Bits_47,
139 48 => RE_Bits_48,
140 49 => RE_Bits_49,
141 50 => RE_Bits_50,
142 51 => RE_Bits_51,
143 52 => RE_Bits_52,
144 53 => RE_Bits_53,
145 54 => RE_Bits_54,
146 55 => RE_Bits_55,
147 56 => RE_Bits_56,
148 57 => RE_Bits_57,
149 58 => RE_Bits_58,
150 59 => RE_Bits_59,
151 60 => RE_Bits_60,
152 61 => RE_Bits_61,
153 62 => RE_Bits_62,
154 63 => RE_Bits_63);
155
156 -- Array of Get routine entities. These are used to obtain an element
157 -- from a packed array. The N'th entry is used to obtain elements from
158 -- a packed array whose component size is N. RE_Null is used as a null
159 -- entry, for the cases where a library routine is not used.
160
161 Get_Id : constant E_Array :=
162 (01 => RE_Null,
163 02 => RE_Null,
164 03 => RE_Get_03,
165 04 => RE_Null,
166 05 => RE_Get_05,
167 06 => RE_Get_06,
168 07 => RE_Get_07,
169 08 => RE_Null,
170 09 => RE_Get_09,
171 10 => RE_Get_10,
172 11 => RE_Get_11,
173 12 => RE_Get_12,
174 13 => RE_Get_13,
175 14 => RE_Get_14,
176 15 => RE_Get_15,
177 16 => RE_Null,
178 17 => RE_Get_17,
179 18 => RE_Get_18,
180 19 => RE_Get_19,
181 20 => RE_Get_20,
182 21 => RE_Get_21,
183 22 => RE_Get_22,
184 23 => RE_Get_23,
185 24 => RE_Get_24,
186 25 => RE_Get_25,
187 26 => RE_Get_26,
188 27 => RE_Get_27,
189 28 => RE_Get_28,
190 29 => RE_Get_29,
191 30 => RE_Get_30,
192 31 => RE_Get_31,
193 32 => RE_Null,
194 33 => RE_Get_33,
195 34 => RE_Get_34,
196 35 => RE_Get_35,
197 36 => RE_Get_36,
198 37 => RE_Get_37,
199 38 => RE_Get_38,
200 39 => RE_Get_39,
201 40 => RE_Get_40,
202 41 => RE_Get_41,
203 42 => RE_Get_42,
204 43 => RE_Get_43,
205 44 => RE_Get_44,
206 45 => RE_Get_45,
207 46 => RE_Get_46,
208 47 => RE_Get_47,
209 48 => RE_Get_48,
210 49 => RE_Get_49,
211 50 => RE_Get_50,
212 51 => RE_Get_51,
213 52 => RE_Get_52,
214 53 => RE_Get_53,
215 54 => RE_Get_54,
216 55 => RE_Get_55,
217 56 => RE_Get_56,
218 57 => RE_Get_57,
219 58 => RE_Get_58,
220 59 => RE_Get_59,
221 60 => RE_Get_60,
222 61 => RE_Get_61,
223 62 => RE_Get_62,
224 63 => RE_Get_63);
225
226 -- Array of Get routine entities to be used in the case where the packed
227 -- array is itself a component of a packed structure, and therefore may
228 -- not be fully aligned. This only affects the even sizes, since for the
229 -- odd sizes, we do not get any fixed alignment in any case.
230
231 GetU_Id : constant E_Array :=
232 (01 => RE_Null,
233 02 => RE_Null,
234 03 => RE_Get_03,
235 04 => RE_Null,
236 05 => RE_Get_05,
237 06 => RE_GetU_06,
238 07 => RE_Get_07,
239 08 => RE_Null,
240 09 => RE_Get_09,
241 10 => RE_GetU_10,
242 11 => RE_Get_11,
243 12 => RE_GetU_12,
244 13 => RE_Get_13,
245 14 => RE_GetU_14,
246 15 => RE_Get_15,
247 16 => RE_Null,
248 17 => RE_Get_17,
249 18 => RE_GetU_18,
250 19 => RE_Get_19,
251 20 => RE_GetU_20,
252 21 => RE_Get_21,
253 22 => RE_GetU_22,
254 23 => RE_Get_23,
255 24 => RE_GetU_24,
256 25 => RE_Get_25,
257 26 => RE_GetU_26,
258 27 => RE_Get_27,
259 28 => RE_GetU_28,
260 29 => RE_Get_29,
261 30 => RE_GetU_30,
262 31 => RE_Get_31,
263 32 => RE_Null,
264 33 => RE_Get_33,
265 34 => RE_GetU_34,
266 35 => RE_Get_35,
267 36 => RE_GetU_36,
268 37 => RE_Get_37,
269 38 => RE_GetU_38,
270 39 => RE_Get_39,
271 40 => RE_GetU_40,
272 41 => RE_Get_41,
273 42 => RE_GetU_42,
274 43 => RE_Get_43,
275 44 => RE_GetU_44,
276 45 => RE_Get_45,
277 46 => RE_GetU_46,
278 47 => RE_Get_47,
279 48 => RE_GetU_48,
280 49 => RE_Get_49,
281 50 => RE_GetU_50,
282 51 => RE_Get_51,
283 52 => RE_GetU_52,
284 53 => RE_Get_53,
285 54 => RE_GetU_54,
286 55 => RE_Get_55,
287 56 => RE_GetU_56,
288 57 => RE_Get_57,
289 58 => RE_GetU_58,
290 59 => RE_Get_59,
291 60 => RE_GetU_60,
292 61 => RE_Get_61,
293 62 => RE_GetU_62,
294 63 => RE_Get_63);
295
296 -- Array of Set routine entities. These are used to assign an element
297 -- of a packed array. The N'th entry is used to assign elements for
298 -- a packed array whose component size is N. RE_Null is used as a null
299 -- entry, for the cases where a library routine is not used.
300
301 Set_Id : constant E_Array :=
302 (01 => RE_Null,
303 02 => RE_Null,
304 03 => RE_Set_03,
305 04 => RE_Null,
306 05 => RE_Set_05,
307 06 => RE_Set_06,
308 07 => RE_Set_07,
309 08 => RE_Null,
310 09 => RE_Set_09,
311 10 => RE_Set_10,
312 11 => RE_Set_11,
313 12 => RE_Set_12,
314 13 => RE_Set_13,
315 14 => RE_Set_14,
316 15 => RE_Set_15,
317 16 => RE_Null,
318 17 => RE_Set_17,
319 18 => RE_Set_18,
320 19 => RE_Set_19,
321 20 => RE_Set_20,
322 21 => RE_Set_21,
323 22 => RE_Set_22,
324 23 => RE_Set_23,
325 24 => RE_Set_24,
326 25 => RE_Set_25,
327 26 => RE_Set_26,
328 27 => RE_Set_27,
329 28 => RE_Set_28,
330 29 => RE_Set_29,
331 30 => RE_Set_30,
332 31 => RE_Set_31,
333 32 => RE_Null,
334 33 => RE_Set_33,
335 34 => RE_Set_34,
336 35 => RE_Set_35,
337 36 => RE_Set_36,
338 37 => RE_Set_37,
339 38 => RE_Set_38,
340 39 => RE_Set_39,
341 40 => RE_Set_40,
342 41 => RE_Set_41,
343 42 => RE_Set_42,
344 43 => RE_Set_43,
345 44 => RE_Set_44,
346 45 => RE_Set_45,
347 46 => RE_Set_46,
348 47 => RE_Set_47,
349 48 => RE_Set_48,
350 49 => RE_Set_49,
351 50 => RE_Set_50,
352 51 => RE_Set_51,
353 52 => RE_Set_52,
354 53 => RE_Set_53,
355 54 => RE_Set_54,
356 55 => RE_Set_55,
357 56 => RE_Set_56,
358 57 => RE_Set_57,
359 58 => RE_Set_58,
360 59 => RE_Set_59,
361 60 => RE_Set_60,
362 61 => RE_Set_61,
363 62 => RE_Set_62,
364 63 => RE_Set_63);
365
366 -- Array of Set routine entities to be used in the case where the packed
367 -- array is itself a component of a packed structure, and therefore may
368 -- not be fully aligned. This only affects the even sizes, since for the
369 -- odd sizes, we do not get any fixed alignment in any case.
370
371 SetU_Id : constant E_Array :=
372 (01 => RE_Null,
373 02 => RE_Null,
374 03 => RE_Set_03,
375 04 => RE_Null,
376 05 => RE_Set_05,
377 06 => RE_SetU_06,
378 07 => RE_Set_07,
379 08 => RE_Null,
380 09 => RE_Set_09,
381 10 => RE_SetU_10,
382 11 => RE_Set_11,
383 12 => RE_SetU_12,
384 13 => RE_Set_13,
385 14 => RE_SetU_14,
386 15 => RE_Set_15,
387 16 => RE_Null,
388 17 => RE_Set_17,
389 18 => RE_SetU_18,
390 19 => RE_Set_19,
391 20 => RE_SetU_20,
392 21 => RE_Set_21,
393 22 => RE_SetU_22,
394 23 => RE_Set_23,
395 24 => RE_SetU_24,
396 25 => RE_Set_25,
397 26 => RE_SetU_26,
398 27 => RE_Set_27,
399 28 => RE_SetU_28,
400 29 => RE_Set_29,
401 30 => RE_SetU_30,
402 31 => RE_Set_31,
403 32 => RE_Null,
404 33 => RE_Set_33,
405 34 => RE_SetU_34,
406 35 => RE_Set_35,
407 36 => RE_SetU_36,
408 37 => RE_Set_37,
409 38 => RE_SetU_38,
410 39 => RE_Set_39,
411 40 => RE_SetU_40,
412 41 => RE_Set_41,
413 42 => RE_SetU_42,
414 43 => RE_Set_43,
415 44 => RE_SetU_44,
416 45 => RE_Set_45,
417 46 => RE_SetU_46,
418 47 => RE_Set_47,
419 48 => RE_SetU_48,
420 49 => RE_Set_49,
421 50 => RE_SetU_50,
422 51 => RE_Set_51,
423 52 => RE_SetU_52,
424 53 => RE_Set_53,
425 54 => RE_SetU_54,
426 55 => RE_Set_55,
427 56 => RE_SetU_56,
428 57 => RE_Set_57,
429 58 => RE_SetU_58,
430 59 => RE_Set_59,
431 60 => RE_SetU_60,
432 61 => RE_Set_61,
433 62 => RE_SetU_62,
434 63 => RE_Set_63);
435
436 -----------------------
437 -- Local Subprograms --
438 -----------------------
439
440 procedure Compute_Linear_Subscript
441 (Atyp : Entity_Id;
442 N : Node_Id;
443 Subscr : out Node_Id);
444 -- Given a constrained array type Atyp, and an indexed component node
445 -- N referencing an array object of this type, build an expression of
446 -- type Standard.Integer representing the zero-based linear subscript
447 -- value. This expression includes any required range checks.
448
449 procedure Convert_To_PAT_Type (Aexp : Node_Id);
450 -- Given an expression of a packed array type, builds a corresponding
451 -- expression whose type is the implementation type used to represent
452 -- the packed array. Aexp is analyzed and resolved on entry and on exit.
453
454 function Known_Aligned_Enough (Obj : Node_Id; Csiz : Nat) return Boolean;
455 -- There are two versions of the Set routines, the ones used when the
456 -- object is known to be sufficiently well aligned given the number of
457 -- bits, and the ones used when the object is not known to be aligned.
458 -- This routine is used to determine which set to use. Obj is a reference
459 -- to the object, and Csiz is the component size of the packed array.
460 -- True is returned if the alignment of object is known to be sufficient,
461 -- defined as 1 for odd bit sizes, 4 for bit sizes divisible by 4, and
462 -- 2 otherwise.
463
464 function Make_Shift_Left (N : Node_Id; S : Node_Id) return Node_Id;
465 -- Build a left shift node, checking for the case of a shift count of zero
466
467 function Make_Shift_Right (N : Node_Id; S : Node_Id) return Node_Id;
468 -- Build a right shift node, checking for the case of a shift count of zero
469
470 function RJ_Unchecked_Convert_To
471 (Typ : Entity_Id;
472 Expr : Node_Id) return Node_Id;
473 -- The packed array code does unchecked conversions which in some cases
474 -- may involve non-discrete types with differing sizes. The semantics of
475 -- such conversions is potentially endian dependent, and the effect we
476 -- want here for such a conversion is to do the conversion in size as
477 -- though numeric items are involved, and we extend or truncate on the
478 -- left side. This happens naturally in the little-endian case, but in
479 -- the big endian case we can get left justification, when what we want
480 -- is right justification. This routine does the unchecked conversion in
481 -- a stepwise manner to ensure that it gives the expected result. Hence
482 -- the name (RJ = Right justified). The parameters Typ and Expr are as
483 -- for the case of a normal Unchecked_Convert_To call.
484
485 procedure Setup_Enumeration_Packed_Array_Reference (N : Node_Id);
486 -- This routine is called in the Get and Set case for arrays that are
487 -- packed but not bit-packed, meaning that they have at least one
488 -- subscript that is of an enumeration type with a non-standard
489 -- representation. This routine modifies the given node to properly
490 -- reference the corresponding packed array type.
491
492 procedure Setup_Inline_Packed_Array_Reference
493 (N : Node_Id;
494 Atyp : Entity_Id;
495 Obj : in out Node_Id;
496 Cmask : out Uint;
497 Shift : out Node_Id);
498 -- This procedure performs common processing on the N_Indexed_Component
499 -- parameter given as N, whose prefix is a reference to a packed array.
500 -- This is used for the get and set when the component size is 1,2,4
501 -- or for other component sizes when the packed array type is a modular
502 -- type (i.e. the cases that are handled with inline code).
503 --
504 -- On entry:
505 --
506 -- N is the N_Indexed_Component node for the packed array reference
507 --
508 -- Atyp is the constrained array type (the actual subtype has been
509 -- computed if necessary to obtain the constraints, but this is still
510 -- the original array type, not the Packed_Array_Type value).
511 --
512 -- Obj is the object which is to be indexed. It is always of type Atyp.
513 --
514 -- On return:
515 --
516 -- Obj is the object containing the desired bit field. It is of type
517 -- Unsigned, Long_Unsigned, or Long_Long_Unsigned, and is either the
518 -- entire value, for the small static case, or the proper selected byte
519 -- from the array in the large or dynamic case. This node is analyzed
520 -- and resolved on return.
521 --
522 -- Shift is a node representing the shift count to be used in the
523 -- rotate right instruction that positions the field for access.
524 -- This node is analyzed and resolved on return.
525 --
526 -- Cmask is a mask corresponding to the width of the component field.
527 -- Its value is 2 ** Csize - 1 (e.g. 2#1111# for component size of 4).
528 --
529 -- Note: in some cases the call to this routine may generate actions
530 -- (for handling multi-use references and the generation of the packed
531 -- array type on the fly). Such actions are inserted into the tree
532 -- directly using Insert_Action.
533
534 ------------------------------
535 -- Compute_Linear_Subcsript --
536 ------------------------------
537
538 procedure Compute_Linear_Subscript
539 (Atyp : Entity_Id;
540 N : Node_Id;
541 Subscr : out Node_Id)
542 is
543 Loc : constant Source_Ptr := Sloc (N);
544 Oldsub : Node_Id;
545 Newsub : Node_Id;
546 Indx : Node_Id;
547 Styp : Entity_Id;
548
549 begin
550 Subscr := Empty;
551
552 -- Loop through dimensions
553
554 Indx := First_Index (Atyp);
555 Oldsub := First (Expressions (N));
556
557 while Present (Indx) loop
558 Styp := Etype (Indx);
559 Newsub := Relocate_Node (Oldsub);
560
561 -- Get expression for the subscript value. First, if Do_Range_Check
562 -- is set on a subscript, then we must do a range check against the
563 -- original bounds (not the bounds of the packed array type). We do
564 -- this by introducing a subtype conversion.
565
566 if Do_Range_Check (Newsub)
567 and then Etype (Newsub) /= Styp
568 then
569 Newsub := Convert_To (Styp, Newsub);
570 end if;
571
572 -- Now evolve the expression for the subscript. First convert
573 -- the subscript to be zero based and of an integer type.
574
575 -- Case of integer type, where we just subtract to get lower bound
576
577 if Is_Integer_Type (Styp) then
578
579 -- If length of integer type is smaller than standard integer,
580 -- then we convert to integer first, then do the subtract
581
582 -- Integer (subscript) - Integer (Styp'First)
583
584 if Esize (Styp) < Esize (Standard_Integer) then
585 Newsub :=
586 Make_Op_Subtract (Loc,
587 Left_Opnd => Convert_To (Standard_Integer, Newsub),
588 Right_Opnd =>
589 Convert_To (Standard_Integer,
590 Make_Attribute_Reference (Loc,
591 Prefix => New_Occurrence_Of (Styp, Loc),
592 Attribute_Name => Name_First)));
593
594 -- For larger integer types, subtract first, then convert to
595 -- integer, this deals with strange long long integer bounds.
596
597 -- Integer (subscript - Styp'First)
598
599 else
600 Newsub :=
601 Convert_To (Standard_Integer,
602 Make_Op_Subtract (Loc,
603 Left_Opnd => Newsub,
604 Right_Opnd =>
605 Make_Attribute_Reference (Loc,
606 Prefix => New_Occurrence_Of (Styp, Loc),
607 Attribute_Name => Name_First)));
608 end if;
609
610 -- For the enumeration case, we have to use 'Pos to get the value
611 -- to work with before subtracting the lower bound.
612
613 -- Integer (Styp'Pos (subscr)) - Integer (Styp'Pos (Styp'First));
614
615 -- This is not quite right for bizarre cases where the size of the
616 -- enumeration type is > Integer'Size bits due to rep clause ???
617
618 else
619 pragma Assert (Is_Enumeration_Type (Styp));
620
621 Newsub :=
622 Make_Op_Subtract (Loc,
623 Left_Opnd => Convert_To (Standard_Integer,
624 Make_Attribute_Reference (Loc,
625 Prefix => New_Occurrence_Of (Styp, Loc),
626 Attribute_Name => Name_Pos,
627 Expressions => New_List (Newsub))),
628
629 Right_Opnd =>
630 Convert_To (Standard_Integer,
631 Make_Attribute_Reference (Loc,
632 Prefix => New_Occurrence_Of (Styp, Loc),
633 Attribute_Name => Name_Pos,
634 Expressions => New_List (
635 Make_Attribute_Reference (Loc,
636 Prefix => New_Occurrence_Of (Styp, Loc),
637 Attribute_Name => Name_First)))));
638 end if;
639
640 Set_Paren_Count (Newsub, 1);
641
642 -- For the first subscript, we just copy that subscript value
643
644 if No (Subscr) then
645 Subscr := Newsub;
646
647 -- Otherwise, we must multiply what we already have by the current
648 -- stride and then add in the new value to the evolving subscript.
649
650 else
651 Subscr :=
652 Make_Op_Add (Loc,
653 Left_Opnd =>
654 Make_Op_Multiply (Loc,
655 Left_Opnd => Subscr,
656 Right_Opnd =>
657 Make_Attribute_Reference (Loc,
658 Attribute_Name => Name_Range_Length,
659 Prefix => New_Occurrence_Of (Styp, Loc))),
660 Right_Opnd => Newsub);
661 end if;
662
663 -- Move to next subscript
664
665 Next_Index (Indx);
666 Next (Oldsub);
667 end loop;
668 end Compute_Linear_Subscript;
669
670 -------------------------
671 -- Convert_To_PAT_Type --
672 -------------------------
673
674 -- The PAT is always obtained from the actual subtype
675
676 procedure Convert_To_PAT_Type (Aexp : Entity_Id) is
677 Act_ST : Entity_Id;
678
679 begin
680 Convert_To_Actual_Subtype (Aexp);
681 Act_ST := Underlying_Type (Etype (Aexp));
682 Create_Packed_Array_Type (Act_ST);
683
684 -- Just replace the etype with the packed array type. This works
685 -- because the expression will not be further analyzed, and Gigi
686 -- considers the two types equivalent in any case.
687
688 -- This is not strictly the case ??? If the reference is an actual
689 -- in a call, the expansion of the prefix is delayed, and must be
690 -- reanalyzed, see Reset_Packed_Prefix. On the other hand, if the
691 -- prefix is a simple array reference, reanalysis can produce spurious
692 -- type errors when the PAT type is replaced again with the original
693 -- type of the array. The following is correct and minimal, but the
694 -- handling of more complex packed expressions in actuals is confused.
695 -- It is likely that the problem only remains for actuals in calls.
696
697 Set_Etype (Aexp, Packed_Array_Type (Act_ST));
698
699 if Is_Entity_Name (Aexp)
700 or else
701 (Nkind (Aexp) = N_Indexed_Component
702 and then Is_Entity_Name (Prefix (Aexp)))
703 then
704 Set_Analyzed (Aexp);
705 end if;
706 end Convert_To_PAT_Type;
707
708 ------------------------------
709 -- Create_Packed_Array_Type --
710 ------------------------------
711
712 procedure Create_Packed_Array_Type (Typ : Entity_Id) is
713 Loc : constant Source_Ptr := Sloc (Typ);
714 Ctyp : constant Entity_Id := Component_Type (Typ);
715 Csize : constant Uint := Component_Size (Typ);
716
717 Ancest : Entity_Id;
718 PB_Type : Entity_Id;
719 PASize : Uint;
720 Decl : Node_Id;
721 PAT : Entity_Id;
722 Len_Dim : Node_Id;
723 Len_Expr : Node_Id;
724 Len_Bits : Uint;
725 Bits_U1 : Node_Id;
726 PAT_High : Node_Id;
727 Btyp : Entity_Id;
728 Lit : Node_Id;
729
730 procedure Install_PAT;
731 -- This procedure is called with Decl set to the declaration for the
732 -- packed array type. It creates the type and installs it as required.
733
734 procedure Set_PB_Type;
735 -- Sets PB_Type to Packed_Bytes{1,2,4} as required by the alignment
736 -- requirements (see documentation in the spec of this package).
737
738 -----------------
739 -- Install_PAT --
740 -----------------
741
742 procedure Install_PAT is
743 Pushed_Scope : Boolean := False;
744
745 begin
746 -- We do not want to put the declaration we have created in the tree
747 -- since it is often hard, and sometimes impossible to find a proper
748 -- place for it (the impossible case arises for a packed array type
749 -- with bounds depending on the discriminant, a declaration cannot
750 -- be put inside the record, and the reference to the discriminant
751 -- cannot be outside the record).
752
753 -- The solution is to analyze the declaration while temporarily
754 -- attached to the tree at an appropriate point, and then we install
755 -- the resulting type as an Itype in the packed array type field of
756 -- the original type, so that no explicit declaration is required.
757
758 -- Note: the packed type is created in the scope of its parent
759 -- type. There are at least some cases where the current scope
760 -- is deeper, and so when this is the case, we temporarily reset
761 -- the scope for the definition. This is clearly safe, since the
762 -- first use of the packed array type will be the implicit
763 -- reference from the corresponding unpacked type when it is
764 -- elaborated.
765
766 if Is_Itype (Typ) then
767 Set_Parent (Decl, Associated_Node_For_Itype (Typ));
768 else
769 Set_Parent (Decl, Declaration_Node (Typ));
770 end if;
771
772 if Scope (Typ) /= Current_Scope then
773 New_Scope (Scope (Typ));
774 Pushed_Scope := True;
775 end if;
776
777 Set_Is_Itype (PAT, True);
778 Set_Packed_Array_Type (Typ, PAT);
779 Analyze (Decl, Suppress => All_Checks);
780
781 if Pushed_Scope then
782 Pop_Scope;
783 end if;
784
785 -- Set Esize and RM_Size to the actual size of the packed object
786 -- Do not reset RM_Size if already set, as happens in the case
787 -- of a modular type.
788
789 Set_Esize (PAT, PASize);
790
791 if Unknown_RM_Size (PAT) then
792 Set_RM_Size (PAT, PASize);
793 end if;
794
795 -- Set remaining fields of packed array type
796
797 Init_Alignment (PAT);
798 Set_Parent (PAT, Empty);
799 Set_Associated_Node_For_Itype (PAT, Typ);
800 Set_Is_Packed_Array_Type (PAT, True);
801 Set_Original_Array_Type (PAT, Typ);
802
803 -- We definitely do not want to delay freezing for packed array
804 -- types. This is of particular importance for the itypes that
805 -- are generated for record components depending on discriminants
806 -- where there is no place to put the freeze node.
807
808 Set_Has_Delayed_Freeze (PAT, False);
809 Set_Has_Delayed_Freeze (Etype (PAT), False);
810
811 -- If we did allocate a freeze node, then clear out the reference
812 -- since it is obsolete (should we delete the freeze node???)
813
814 Set_Freeze_Node (PAT, Empty);
815 Set_Freeze_Node (Etype (PAT), Empty);
816 end Install_PAT;
817
818 -----------------
819 -- Set_PB_Type --
820 -----------------
821
822 procedure Set_PB_Type is
823 begin
824 -- If the user has specified an explicit alignment for the
825 -- type or component, take it into account.
826
827 if Csize <= 2 or else Csize = 4 or else Csize mod 2 /= 0
828 or else Alignment (Typ) = 1
829 or else Component_Alignment (Typ) = Calign_Storage_Unit
830 then
831 PB_Type := RTE (RE_Packed_Bytes1);
832
833 elsif Csize mod 4 /= 0
834 or else Alignment (Typ) = 2
835 then
836 PB_Type := RTE (RE_Packed_Bytes2);
837
838 else
839 PB_Type := RTE (RE_Packed_Bytes4);
840 end if;
841 end Set_PB_Type;
842
843 -- Start of processing for Create_Packed_Array_Type
844
845 begin
846 -- If we already have a packed array type, nothing to do
847
848 if Present (Packed_Array_Type (Typ)) then
849 return;
850 end if;
851
852 -- If our immediate ancestor subtype is constrained, and it already
853 -- has a packed array type, then just share the same type, since the
854 -- bounds must be the same. If the ancestor is not an array type but
855 -- a private type, as can happen with multiple instantiations, create
856 -- a new packed type, to avoid privacy issues.
857
858 if Ekind (Typ) = E_Array_Subtype then
859 Ancest := Ancestor_Subtype (Typ);
860
861 if Present (Ancest)
862 and then Is_Array_Type (Ancest)
863 and then Is_Constrained (Ancest)
864 and then Present (Packed_Array_Type (Ancest))
865 then
866 Set_Packed_Array_Type (Typ, Packed_Array_Type (Ancest));
867 return;
868 end if;
869 end if;
870
871 -- We preset the result type size from the size of the original array
872 -- type, since this size clearly belongs to the packed array type. The
873 -- size of the conceptual unpacked type is always set to unknown.
874
875 PASize := Esize (Typ);
876
877 -- Case of an array where at least one index is of an enumeration
878 -- type with a non-standard representation, but the component size
879 -- is not appropriate for bit packing. This is the case where we
880 -- have Is_Packed set (we would never be in this unit otherwise),
881 -- but Is_Bit_Packed_Array is false.
882
883 -- Note that if the component size is appropriate for bit packing,
884 -- then the circuit for the computation of the subscript properly
885 -- deals with the non-standard enumeration type case by taking the
886 -- Pos anyway.
887
888 if not Is_Bit_Packed_Array (Typ) then
889
890 -- Here we build a declaration:
891
892 -- type tttP is array (index1, index2, ...) of component_type
893
894 -- where index1, index2, are the index types. These are the same
895 -- as the index types of the original array, except for the non-
896 -- standard representation enumeration type case, where we have
897 -- two subcases.
898
899 -- For the unconstrained array case, we use
900
901 -- Natural range <>
902
903 -- For the constrained case, we use
904
905 -- Natural range Enum_Type'Pos (Enum_Type'First) ..
906 -- Enum_Type'Pos (Enum_Type'Last);
907
908 PAT :=
909 Make_Defining_Identifier (Loc,
910 Chars => New_External_Name (Chars (Typ), 'P'));
911
912 Set_Packed_Array_Type (Typ, PAT);
913
914 declare
915 Indexes : constant List_Id := New_List;
916 Indx : Node_Id;
917 Indx_Typ : Entity_Id;
918 Enum_Case : Boolean;
919 Typedef : Node_Id;
920
921 begin
922 Indx := First_Index (Typ);
923
924 while Present (Indx) loop
925 Indx_Typ := Etype (Indx);
926
927 Enum_Case := Is_Enumeration_Type (Indx_Typ)
928 and then Has_Non_Standard_Rep (Indx_Typ);
929
930 -- Unconstrained case
931
932 if not Is_Constrained (Typ) then
933 if Enum_Case then
934 Indx_Typ := Standard_Natural;
935 end if;
936
937 Append_To (Indexes, New_Occurrence_Of (Indx_Typ, Loc));
938
939 -- Constrained case
940
941 else
942 if not Enum_Case then
943 Append_To (Indexes, New_Occurrence_Of (Indx_Typ, Loc));
944
945 else
946 Append_To (Indexes,
947 Make_Subtype_Indication (Loc,
948 Subtype_Mark =>
949 New_Occurrence_Of (Standard_Natural, Loc),
950 Constraint =>
951 Make_Range_Constraint (Loc,
952 Range_Expression =>
953 Make_Range (Loc,
954 Low_Bound =>
955 Make_Attribute_Reference (Loc,
956 Prefix =>
957 New_Occurrence_Of (Indx_Typ, Loc),
958 Attribute_Name => Name_Pos,
959 Expressions => New_List (
960 Make_Attribute_Reference (Loc,
961 Prefix =>
962 New_Occurrence_Of (Indx_Typ, Loc),
963 Attribute_Name => Name_First))),
964
965 High_Bound =>
966 Make_Attribute_Reference (Loc,
967 Prefix =>
968 New_Occurrence_Of (Indx_Typ, Loc),
969 Attribute_Name => Name_Pos,
970 Expressions => New_List (
971 Make_Attribute_Reference (Loc,
972 Prefix =>
973 New_Occurrence_Of (Indx_Typ, Loc),
974 Attribute_Name => Name_Last)))))));
975
976 end if;
977 end if;
978
979 Next_Index (Indx);
980 end loop;
981
982 if not Is_Constrained (Typ) then
983 Typedef :=
984 Make_Unconstrained_Array_Definition (Loc,
985 Subtype_Marks => Indexes,
986 Component_Definition =>
987 Make_Component_Definition (Loc,
988 Aliased_Present => False,
989 Subtype_Indication =>
990 New_Occurrence_Of (Ctyp, Loc)));
991
992 else
993 Typedef :=
994 Make_Constrained_Array_Definition (Loc,
995 Discrete_Subtype_Definitions => Indexes,
996 Component_Definition =>
997 Make_Component_Definition (Loc,
998 Aliased_Present => False,
999 Subtype_Indication =>
1000 New_Occurrence_Of (Ctyp, Loc)));
1001 end if;
1002
1003 Decl :=
1004 Make_Full_Type_Declaration (Loc,
1005 Defining_Identifier => PAT,
1006 Type_Definition => Typedef);
1007 end;
1008
1009 -- Set type as packed array type and install it
1010
1011 Set_Is_Packed_Array_Type (PAT);
1012 Install_PAT;
1013 return;
1014
1015 -- Case of bit-packing required for unconstrained array. We create
1016 -- a subtype that is equivalent to use Packed_Bytes{1,2,4} as needed.
1017
1018 elsif not Is_Constrained (Typ) then
1019 PAT :=
1020 Make_Defining_Identifier (Loc,
1021 Chars => Make_Packed_Array_Type_Name (Typ, Csize));
1022
1023 Set_Packed_Array_Type (Typ, PAT);
1024 Set_PB_Type;
1025
1026 Decl :=
1027 Make_Subtype_Declaration (Loc,
1028 Defining_Identifier => PAT,
1029 Subtype_Indication => New_Occurrence_Of (PB_Type, Loc));
1030 Install_PAT;
1031 return;
1032
1033 -- Remaining code is for the case of bit-packing for constrained array
1034
1035 -- The name of the packed array subtype is
1036
1037 -- ttt___Xsss
1038
1039 -- where sss is the component size in bits and ttt is the name of
1040 -- the parent packed type.
1041
1042 else
1043 PAT :=
1044 Make_Defining_Identifier (Loc,
1045 Chars => Make_Packed_Array_Type_Name (Typ, Csize));
1046
1047 Set_Packed_Array_Type (Typ, PAT);
1048
1049 -- Build an expression for the length of the array in bits.
1050 -- This is the product of the length of each of the dimensions
1051
1052 declare
1053 J : Nat := 1;
1054
1055 begin
1056 Len_Expr := Empty; -- suppress junk warning
1057
1058 loop
1059 Len_Dim :=
1060 Make_Attribute_Reference (Loc,
1061 Attribute_Name => Name_Length,
1062 Prefix => New_Occurrence_Of (Typ, Loc),
1063 Expressions => New_List (
1064 Make_Integer_Literal (Loc, J)));
1065
1066 if J = 1 then
1067 Len_Expr := Len_Dim;
1068
1069 else
1070 Len_Expr :=
1071 Make_Op_Multiply (Loc,
1072 Left_Opnd => Len_Expr,
1073 Right_Opnd => Len_Dim);
1074 end if;
1075
1076 J := J + 1;
1077 exit when J > Number_Dimensions (Typ);
1078 end loop;
1079 end;
1080
1081 -- Temporarily attach the length expression to the tree and analyze
1082 -- and resolve it, so that we can test its value. We assume that the
1083 -- total length fits in type Integer. This expression may involve
1084 -- discriminants, so we treat it as a default/per-object expression.
1085
1086 Set_Parent (Len_Expr, Typ);
1087 Analyze_Per_Use_Expression (Len_Expr, Standard_Integer);
1088
1089 -- Use a modular type if possible. We can do this if we have
1090 -- static bounds, and the length is small enough, and the length
1091 -- is not zero. We exclude the zero length case because the size
1092 -- of things is always at least one, and the zero length object
1093 -- would have an anomalous size.
1094
1095 if Compile_Time_Known_Value (Len_Expr) then
1096 Len_Bits := Expr_Value (Len_Expr) * Csize;
1097
1098 -- We normally consider small enough to mean no larger than the
1099 -- value of System_Max_Binary_Modulus_Power, checking that in the
1100 -- case of values longer than word size, we have long shifts.
1101
1102 if Len_Bits > 0
1103 and then
1104 (Len_Bits <= System_Word_Size
1105 or else (Len_Bits <= System_Max_Binary_Modulus_Power
1106 and then Support_Long_Shifts_On_Target))
1107
1108 -- Also test for alignment given. If an alignment is given which
1109 -- is smaller than the natural modular alignment, force the array
1110 -- of bytes representation to accommodate the alignment.
1111
1112 and then
1113 (No (Alignment_Clause (Typ))
1114 or else
1115 Alignment (Typ) >= ((Len_Bits + System_Storage_Unit)
1116 / System_Storage_Unit))
1117 then
1118 -- We can use the modular type, it has the form:
1119
1120 -- subtype tttPn is btyp
1121 -- range 0 .. 2 ** ((Typ'Length (1)
1122 -- * ... * Typ'Length (n)) * Csize) - 1;
1123
1124 -- The bounds are statically known, and btyp is one
1125 -- of the unsigned types, depending on the length. If the
1126 -- type is its first subtype, i.e. it is a user-defined
1127 -- type, no object of the type will be larger, and it is
1128 -- worthwhile to use a small unsigned type.
1129
1130 if Len_Bits <= Standard_Short_Integer_Size
1131 and then First_Subtype (Typ) = Typ
1132 then
1133 Btyp := RTE (RE_Short_Unsigned);
1134
1135 elsif Len_Bits <= Standard_Integer_Size then
1136 Btyp := RTE (RE_Unsigned);
1137
1138 elsif Len_Bits <= Standard_Long_Integer_Size then
1139 Btyp := RTE (RE_Long_Unsigned);
1140
1141 else
1142 Btyp := RTE (RE_Long_Long_Unsigned);
1143 end if;
1144
1145 Lit := Make_Integer_Literal (Loc, 2 ** Len_Bits - 1);
1146 Set_Print_In_Hex (Lit);
1147
1148 Decl :=
1149 Make_Subtype_Declaration (Loc,
1150 Defining_Identifier => PAT,
1151 Subtype_Indication =>
1152 Make_Subtype_Indication (Loc,
1153 Subtype_Mark => New_Occurrence_Of (Btyp, Loc),
1154
1155 Constraint =>
1156 Make_Range_Constraint (Loc,
1157 Range_Expression =>
1158 Make_Range (Loc,
1159 Low_Bound =>
1160 Make_Integer_Literal (Loc, 0),
1161 High_Bound => Lit))));
1162
1163 if PASize = Uint_0 then
1164 PASize := Len_Bits;
1165 end if;
1166
1167 Install_PAT;
1168 return;
1169 end if;
1170 end if;
1171
1172 -- Could not use a modular type, for all other cases, we build
1173 -- a packed array subtype:
1174
1175 -- subtype tttPn is
1176 -- System.Packed_Bytes{1,2,4} (0 .. (Bits + 7) / 8 - 1);
1177
1178 -- Bits is the length of the array in bits
1179
1180 Set_PB_Type;
1181
1182 Bits_U1 :=
1183 Make_Op_Add (Loc,
1184 Left_Opnd =>
1185 Make_Op_Multiply (Loc,
1186 Left_Opnd =>
1187 Make_Integer_Literal (Loc, Csize),
1188 Right_Opnd => Len_Expr),
1189
1190 Right_Opnd =>
1191 Make_Integer_Literal (Loc, 7));
1192
1193 Set_Paren_Count (Bits_U1, 1);
1194
1195 PAT_High :=
1196 Make_Op_Subtract (Loc,
1197 Left_Opnd =>
1198 Make_Op_Divide (Loc,
1199 Left_Opnd => Bits_U1,
1200 Right_Opnd => Make_Integer_Literal (Loc, 8)),
1201 Right_Opnd => Make_Integer_Literal (Loc, 1));
1202
1203 Decl :=
1204 Make_Subtype_Declaration (Loc,
1205 Defining_Identifier => PAT,
1206 Subtype_Indication =>
1207 Make_Subtype_Indication (Loc,
1208 Subtype_Mark => New_Occurrence_Of (PB_Type, Loc),
1209 Constraint =>
1210
1211 Make_Index_Or_Discriminant_Constraint (Loc,
1212 Constraints => New_List (
1213 Make_Range (Loc,
1214 Low_Bound =>
1215 Make_Integer_Literal (Loc, 0),
1216 High_Bound => PAT_High)))));
1217
1218 Install_PAT;
1219
1220 -- Currently the code in this unit requires that packed arrays
1221 -- represented by non-modular arrays of bytes be on a byte
1222 -- boundary for bit sizes handled by System.Pack_nn units.
1223 -- That's because these units assume the array being accessed
1224 -- starts on a byte boundary.
1225
1226 if Get_Id (UI_To_Int (Csize)) /= RE_Null then
1227 Set_Must_Be_On_Byte_Boundary (Typ);
1228 end if;
1229 end if;
1230 end Create_Packed_Array_Type;
1231
1232 -----------------------------------
1233 -- Expand_Bit_Packed_Element_Set --
1234 -----------------------------------
1235
1236 procedure Expand_Bit_Packed_Element_Set (N : Node_Id) is
1237 Loc : constant Source_Ptr := Sloc (N);
1238 Lhs : constant Node_Id := Name (N);
1239
1240 Ass_OK : constant Boolean := Assignment_OK (Lhs);
1241 -- Used to preserve assignment OK status when assignment is rewritten
1242
1243 Rhs : Node_Id := Expression (N);
1244 -- Initially Rhs is the right hand side value, it will be replaced
1245 -- later by an appropriate unchecked conversion for the assignment.
1246
1247 Obj : Node_Id;
1248 Atyp : Entity_Id;
1249 PAT : Entity_Id;
1250 Ctyp : Entity_Id;
1251 Csiz : Int;
1252 Cmask : Uint;
1253
1254 Shift : Node_Id;
1255 -- The expression for the shift value that is required
1256
1257 Shift_Used : Boolean := False;
1258 -- Set True if Shift has been used in the generated code at least
1259 -- once, so that it must be duplicated if used again
1260
1261 New_Lhs : Node_Id;
1262 New_Rhs : Node_Id;
1263
1264 Rhs_Val_Known : Boolean;
1265 Rhs_Val : Uint;
1266 -- If the value of the right hand side as an integer constant is
1267 -- known at compile time, Rhs_Val_Known is set True, and Rhs_Val
1268 -- contains the value. Otherwise Rhs_Val_Known is set False, and
1269 -- the Rhs_Val is undefined.
1270
1271 function Get_Shift return Node_Id;
1272 -- Function used to get the value of Shift, making sure that it
1273 -- gets duplicated if the function is called more than once.
1274
1275 ---------------
1276 -- Get_Shift --
1277 ---------------
1278
1279 function Get_Shift return Node_Id is
1280 begin
1281 -- If we used the shift value already, then duplicate it. We
1282 -- set a temporary parent in case actions have to be inserted.
1283
1284 if Shift_Used then
1285 Set_Parent (Shift, N);
1286 return Duplicate_Subexpr_No_Checks (Shift);
1287
1288 -- If first time, use Shift unchanged, and set flag for first use
1289
1290 else
1291 Shift_Used := True;
1292 return Shift;
1293 end if;
1294 end Get_Shift;
1295
1296 -- Start of processing for Expand_Bit_Packed_Element_Set
1297
1298 begin
1299 pragma Assert (Is_Bit_Packed_Array (Etype (Prefix (Lhs))));
1300
1301 Obj := Relocate_Node (Prefix (Lhs));
1302 Convert_To_Actual_Subtype (Obj);
1303 Atyp := Etype (Obj);
1304 PAT := Packed_Array_Type (Atyp);
1305 Ctyp := Component_Type (Atyp);
1306 Csiz := UI_To_Int (Component_Size (Atyp));
1307
1308 -- We convert the right hand side to the proper subtype to ensure
1309 -- that an appropriate range check is made (since the normal range
1310 -- check from assignment will be lost in the transformations). This
1311 -- conversion is analyzed immediately so that subsequent processing
1312 -- can work with an analyzed Rhs (and e.g. look at its Etype)
1313
1314 -- If the right-hand side is a string literal, create a temporary for
1315 -- it, constant-folding is not ready to wrap the bit representation
1316 -- of a string literal.
1317
1318 if Nkind (Rhs) = N_String_Literal then
1319 declare
1320 Decl : Node_Id;
1321 begin
1322 Decl :=
1323 Make_Object_Declaration (Loc,
1324 Defining_Identifier =>
1325 Make_Defining_Identifier (Loc, New_Internal_Name ('T')),
1326 Object_Definition => New_Occurrence_Of (Ctyp, Loc),
1327 Expression => New_Copy_Tree (Rhs));
1328
1329 Insert_Actions (N, New_List (Decl));
1330 Rhs := New_Occurrence_Of (Defining_Identifier (Decl), Loc);
1331 end;
1332 end if;
1333
1334 Rhs := Convert_To (Ctyp, Rhs);
1335 Set_Parent (Rhs, N);
1336 Analyze_And_Resolve (Rhs, Ctyp);
1337
1338 -- Case of component size 1,2,4 or any component size for the modular
1339 -- case. These are the cases for which we can inline the code.
1340
1341 if Csiz = 1 or else Csiz = 2 or else Csiz = 4
1342 or else (Present (PAT) and then Is_Modular_Integer_Type (PAT))
1343 then
1344 Setup_Inline_Packed_Array_Reference (Lhs, Atyp, Obj, Cmask, Shift);
1345
1346 -- The statement to be generated is:
1347
1348 -- Obj := atyp!((Obj and Mask1) or (shift_left (rhs, shift)))
1349
1350 -- where mask1 is obtained by shifting Cmask left Shift bits
1351 -- and then complementing the result.
1352
1353 -- the "and Mask1" is omitted if rhs is constant and all 1 bits
1354
1355 -- the "or ..." is omitted if rhs is constant and all 0 bits
1356
1357 -- rhs is converted to the appropriate type
1358
1359 -- The result is converted back to the array type, since
1360 -- otherwise we lose knowledge of the packed nature.
1361
1362 -- Determine if right side is all 0 bits or all 1 bits
1363
1364 if Compile_Time_Known_Value (Rhs) then
1365 Rhs_Val := Expr_Rep_Value (Rhs);
1366 Rhs_Val_Known := True;
1367
1368 -- The following test catches the case of an unchecked conversion
1369 -- of an integer literal. This results from optimizing aggregates
1370 -- of packed types.
1371
1372 elsif Nkind (Rhs) = N_Unchecked_Type_Conversion
1373 and then Compile_Time_Known_Value (Expression (Rhs))
1374 then
1375 Rhs_Val := Expr_Rep_Value (Expression (Rhs));
1376 Rhs_Val_Known := True;
1377
1378 else
1379 Rhs_Val := No_Uint;
1380 Rhs_Val_Known := False;
1381 end if;
1382
1383 -- Some special checks for the case where the right hand value
1384 -- is known at compile time. Basically we have to take care of
1385 -- the implicit conversion to the subtype of the component object.
1386
1387 if Rhs_Val_Known then
1388
1389 -- If we have a biased component type then we must manually do
1390 -- the biasing, since we are taking responsibility in this case
1391 -- for constructing the exact bit pattern to be used.
1392
1393 if Has_Biased_Representation (Ctyp) then
1394 Rhs_Val := Rhs_Val - Expr_Rep_Value (Type_Low_Bound (Ctyp));
1395 end if;
1396
1397 -- For a negative value, we manually convert the twos complement
1398 -- value to a corresponding unsigned value, so that the proper
1399 -- field width is maintained. If we did not do this, we would
1400 -- get too many leading sign bits later on.
1401
1402 if Rhs_Val < 0 then
1403 Rhs_Val := 2 ** UI_From_Int (Csiz) + Rhs_Val;
1404 end if;
1405 end if;
1406
1407 New_Lhs := Duplicate_Subexpr (Obj, True);
1408 New_Rhs := Duplicate_Subexpr_No_Checks (Obj);
1409
1410 -- First we deal with the "and"
1411
1412 if not Rhs_Val_Known or else Rhs_Val /= Cmask then
1413 declare
1414 Mask1 : Node_Id;
1415 Lit : Node_Id;
1416
1417 begin
1418 if Compile_Time_Known_Value (Shift) then
1419 Mask1 :=
1420 Make_Integer_Literal (Loc,
1421 Modulus (Etype (Obj)) - 1 -
1422 (Cmask * (2 ** Expr_Value (Get_Shift))));
1423 Set_Print_In_Hex (Mask1);
1424
1425 else
1426 Lit := Make_Integer_Literal (Loc, Cmask);
1427 Set_Print_In_Hex (Lit);
1428 Mask1 :=
1429 Make_Op_Not (Loc,
1430 Right_Opnd => Make_Shift_Left (Lit, Get_Shift));
1431 end if;
1432
1433 New_Rhs :=
1434 Make_Op_And (Loc,
1435 Left_Opnd => New_Rhs,
1436 Right_Opnd => Mask1);
1437 end;
1438 end if;
1439
1440 -- Then deal with the "or"
1441
1442 if not Rhs_Val_Known or else Rhs_Val /= 0 then
1443 declare
1444 Or_Rhs : Node_Id;
1445
1446 procedure Fixup_Rhs;
1447 -- Adjust Rhs by bias if biased representation for components
1448 -- or remove extraneous high order sign bits if signed.
1449
1450 procedure Fixup_Rhs is
1451 Etyp : constant Entity_Id := Etype (Rhs);
1452
1453 begin
1454 -- For biased case, do the required biasing by simply
1455 -- converting to the biased subtype (the conversion
1456 -- will generate the required bias).
1457
1458 if Has_Biased_Representation (Ctyp) then
1459 Rhs := Convert_To (Ctyp, Rhs);
1460
1461 -- For a signed integer type that is not biased, generate
1462 -- a conversion to unsigned to strip high order sign bits.
1463
1464 elsif Is_Signed_Integer_Type (Ctyp) then
1465 Rhs := Unchecked_Convert_To (RTE (Bits_Id (Csiz)), Rhs);
1466 end if;
1467
1468 -- Set Etype, since it can be referenced before the
1469 -- node is completely analyzed.
1470
1471 Set_Etype (Rhs, Etyp);
1472
1473 -- We now need to do an unchecked conversion of the
1474 -- result to the target type, but it is important that
1475 -- this conversion be a right justified conversion and
1476 -- not a left justified conversion.
1477
1478 Rhs := RJ_Unchecked_Convert_To (Etype (Obj), Rhs);
1479
1480 end Fixup_Rhs;
1481
1482 begin
1483 if Rhs_Val_Known
1484 and then Compile_Time_Known_Value (Get_Shift)
1485 then
1486 Or_Rhs :=
1487 Make_Integer_Literal (Loc,
1488 Rhs_Val * (2 ** Expr_Value (Get_Shift)));
1489 Set_Print_In_Hex (Or_Rhs);
1490
1491 else
1492 -- We have to convert the right hand side to Etype (Obj).
1493 -- A special case case arises if what we have now is a Val
1494 -- attribute reference whose expression type is Etype (Obj).
1495 -- This happens for assignments of fields from the same
1496 -- array. In this case we get the required right hand side
1497 -- by simply removing the inner attribute reference.
1498
1499 if Nkind (Rhs) = N_Attribute_Reference
1500 and then Attribute_Name (Rhs) = Name_Val
1501 and then Etype (First (Expressions (Rhs))) = Etype (Obj)
1502 then
1503 Rhs := Relocate_Node (First (Expressions (Rhs)));
1504 Fixup_Rhs;
1505
1506 -- If the value of the right hand side is a known integer
1507 -- value, then just replace it by an untyped constant,
1508 -- which will be properly retyped when we analyze and
1509 -- resolve the expression.
1510
1511 elsif Rhs_Val_Known then
1512
1513 -- Note that Rhs_Val has already been normalized to
1514 -- be an unsigned value with the proper number of bits.
1515
1516 Rhs :=
1517 Make_Integer_Literal (Loc, Rhs_Val);
1518
1519 -- Otherwise we need an unchecked conversion
1520
1521 else
1522 Fixup_Rhs;
1523 end if;
1524
1525 Or_Rhs := Make_Shift_Left (Rhs, Get_Shift);
1526 end if;
1527
1528 if Nkind (New_Rhs) = N_Op_And then
1529 Set_Paren_Count (New_Rhs, 1);
1530 end if;
1531
1532 New_Rhs :=
1533 Make_Op_Or (Loc,
1534 Left_Opnd => New_Rhs,
1535 Right_Opnd => Or_Rhs);
1536 end;
1537 end if;
1538
1539 -- Now do the rewrite
1540
1541 Rewrite (N,
1542 Make_Assignment_Statement (Loc,
1543 Name => New_Lhs,
1544 Expression =>
1545 Unchecked_Convert_To (Etype (New_Lhs), New_Rhs)));
1546 Set_Assignment_OK (Name (N), Ass_OK);
1547
1548 -- All other component sizes for non-modular case
1549
1550 else
1551 -- We generate
1552
1553 -- Set_nn (Arr'address, Subscr, Bits_nn!(Rhs))
1554
1555 -- where Subscr is the computed linear subscript
1556
1557 declare
1558 Bits_nn : constant Entity_Id := RTE (Bits_Id (Csiz));
1559 Set_nn : Entity_Id;
1560 Subscr : Node_Id;
1561 Atyp : Entity_Id;
1562
1563 begin
1564 if No (Bits_nn) then
1565
1566 -- Error, most likely High_Integrity_Mode restriction
1567
1568 return;
1569 end if;
1570
1571 -- Acquire proper Set entity. We use the aligned or unaligned
1572 -- case as appropriate.
1573
1574 if Known_Aligned_Enough (Obj, Csiz) then
1575 Set_nn := RTE (Set_Id (Csiz));
1576 else
1577 Set_nn := RTE (SetU_Id (Csiz));
1578 end if;
1579
1580 -- Now generate the set reference
1581
1582 Obj := Relocate_Node (Prefix (Lhs));
1583 Convert_To_Actual_Subtype (Obj);
1584 Atyp := Etype (Obj);
1585 Compute_Linear_Subscript (Atyp, Lhs, Subscr);
1586
1587 -- Below we must make the assumption that Obj is
1588 -- at least byte aligned, since otherwise its address
1589 -- cannot be taken. The assumption holds since the
1590 -- only arrays that can be misaligned are small packed
1591 -- arrays which are implemented as a modular type, and
1592 -- that is not the case here.
1593
1594 Rewrite (N,
1595 Make_Procedure_Call_Statement (Loc,
1596 Name => New_Occurrence_Of (Set_nn, Loc),
1597 Parameter_Associations => New_List (
1598 Make_Attribute_Reference (Loc,
1599 Attribute_Name => Name_Address,
1600 Prefix => Obj),
1601 Subscr,
1602 Unchecked_Convert_To (Bits_nn,
1603 Convert_To (Ctyp, Rhs)))));
1604
1605 end;
1606 end if;
1607
1608 Analyze (N, Suppress => All_Checks);
1609 end Expand_Bit_Packed_Element_Set;
1610
1611 -------------------------------------
1612 -- Expand_Packed_Address_Reference --
1613 -------------------------------------
1614
1615 procedure Expand_Packed_Address_Reference (N : Node_Id) is
1616 Loc : constant Source_Ptr := Sloc (N);
1617 Ploc : Source_Ptr;
1618 Pref : Node_Id;
1619 Expr : Node_Id;
1620 Term : Node_Id;
1621 Atyp : Entity_Id;
1622 Subscr : Node_Id;
1623
1624 begin
1625 Pref := Prefix (N);
1626 Expr := Empty;
1627
1628 -- We build up an expression serially that has the form
1629
1630 -- outer_object'Address
1631 -- + (linear-subscript * component_size for each array reference
1632 -- + field'Bit_Position for each record field
1633 -- + ...
1634 -- + ...) / Storage_Unit;
1635
1636 -- Some additional conversions are required to deal with the addition
1637 -- operation, which is not normally visible to generated code.
1638
1639 loop
1640 Ploc := Sloc (Pref);
1641
1642 if Nkind (Pref) = N_Indexed_Component then
1643 Convert_To_Actual_Subtype (Prefix (Pref));
1644 Atyp := Etype (Prefix (Pref));
1645 Compute_Linear_Subscript (Atyp, Pref, Subscr);
1646
1647 Term :=
1648 Make_Op_Multiply (Ploc,
1649 Left_Opnd => Subscr,
1650 Right_Opnd =>
1651 Make_Attribute_Reference (Ploc,
1652 Prefix => New_Occurrence_Of (Atyp, Ploc),
1653 Attribute_Name => Name_Component_Size));
1654
1655 elsif Nkind (Pref) = N_Selected_Component then
1656 Term :=
1657 Make_Attribute_Reference (Ploc,
1658 Prefix => Selector_Name (Pref),
1659 Attribute_Name => Name_Bit_Position);
1660
1661 else
1662 exit;
1663 end if;
1664
1665 Term := Convert_To (RTE (RE_Integer_Address), Term);
1666
1667 if No (Expr) then
1668 Expr := Term;
1669
1670 else
1671 Expr :=
1672 Make_Op_Add (Ploc,
1673 Left_Opnd => Expr,
1674 Right_Opnd => Term);
1675 end if;
1676
1677 Pref := Prefix (Pref);
1678 end loop;
1679
1680 Rewrite (N,
1681 Unchecked_Convert_To (RTE (RE_Address),
1682 Make_Op_Add (Loc,
1683 Left_Opnd =>
1684 Unchecked_Convert_To (RTE (RE_Integer_Address),
1685 Make_Attribute_Reference (Loc,
1686 Prefix => Pref,
1687 Attribute_Name => Name_Address)),
1688
1689 Right_Opnd =>
1690 Make_Op_Divide (Loc,
1691 Left_Opnd => Expr,
1692 Right_Opnd =>
1693 Make_Integer_Literal (Loc, System_Storage_Unit)))));
1694
1695 Analyze_And_Resolve (N, RTE (RE_Address));
1696 end Expand_Packed_Address_Reference;
1697
1698 ------------------------------------
1699 -- Expand_Packed_Boolean_Operator --
1700 ------------------------------------
1701
1702 -- This routine expands "a op b" for the packed cases
1703
1704 procedure Expand_Packed_Boolean_Operator (N : Node_Id) is
1705 Loc : constant Source_Ptr := Sloc (N);
1706 Typ : constant Entity_Id := Etype (N);
1707 L : constant Node_Id := Relocate_Node (Left_Opnd (N));
1708 R : constant Node_Id := Relocate_Node (Right_Opnd (N));
1709
1710 Ltyp : Entity_Id;
1711 Rtyp : Entity_Id;
1712 PAT : Entity_Id;
1713
1714 begin
1715 Convert_To_Actual_Subtype (L);
1716 Convert_To_Actual_Subtype (R);
1717
1718 Ensure_Defined (Etype (L), N);
1719 Ensure_Defined (Etype (R), N);
1720
1721 Apply_Length_Check (R, Etype (L));
1722
1723 Ltyp := Etype (L);
1724 Rtyp := Etype (R);
1725
1726 -- First an odd and silly test. We explicitly check for the XOR
1727 -- case where the component type is True .. True, since this will
1728 -- raise constraint error. A special check is required since CE
1729 -- will not be required other wise (cf Expand_Packed_Not).
1730
1731 -- No such check is required for AND and OR, since for both these
1732 -- cases False op False = False, and True op True = True.
1733
1734 if Nkind (N) = N_Op_Xor then
1735 declare
1736 CT : constant Entity_Id := Component_Type (Rtyp);
1737 BT : constant Entity_Id := Base_Type (CT);
1738
1739 begin
1740 Insert_Action (N,
1741 Make_Raise_Constraint_Error (Loc,
1742 Condition =>
1743 Make_Op_And (Loc,
1744 Left_Opnd =>
1745 Make_Op_Eq (Loc,
1746 Left_Opnd =>
1747 Make_Attribute_Reference (Loc,
1748 Prefix => New_Occurrence_Of (CT, Loc),
1749 Attribute_Name => Name_First),
1750
1751 Right_Opnd =>
1752 Convert_To (BT,
1753 New_Occurrence_Of (Standard_True, Loc))),
1754
1755 Right_Opnd =>
1756 Make_Op_Eq (Loc,
1757 Left_Opnd =>
1758 Make_Attribute_Reference (Loc,
1759 Prefix => New_Occurrence_Of (CT, Loc),
1760 Attribute_Name => Name_Last),
1761
1762 Right_Opnd =>
1763 Convert_To (BT,
1764 New_Occurrence_Of (Standard_True, Loc)))),
1765 Reason => CE_Range_Check_Failed));
1766 end;
1767 end if;
1768
1769 -- Now that that silliness is taken care of, get packed array type
1770
1771 Convert_To_PAT_Type (L);
1772 Convert_To_PAT_Type (R);
1773
1774 PAT := Etype (L);
1775
1776 -- For the modular case, we expand a op b into
1777
1778 -- rtyp!(pat!(a) op pat!(b))
1779
1780 -- where rtyp is the Etype of the left operand. Note that we do not
1781 -- convert to the base type, since this would be unconstrained, and
1782 -- hence not have a corresponding packed array type set.
1783
1784 -- Note that both operands must be modular for this code to be used
1785
1786 if Is_Modular_Integer_Type (PAT)
1787 and then
1788 Is_Modular_Integer_Type (Etype (R))
1789 then
1790 declare
1791 P : Node_Id;
1792
1793 begin
1794 if Nkind (N) = N_Op_And then
1795 P := Make_Op_And (Loc, L, R);
1796
1797 elsif Nkind (N) = N_Op_Or then
1798 P := Make_Op_Or (Loc, L, R);
1799
1800 else -- Nkind (N) = N_Op_Xor
1801 P := Make_Op_Xor (Loc, L, R);
1802 end if;
1803
1804 Rewrite (N, Unchecked_Convert_To (Rtyp, P));
1805 end;
1806
1807 -- For the array case, we insert the actions
1808
1809 -- Result : Ltype;
1810
1811 -- System.Bitops.Bit_And/Or/Xor
1812 -- (Left'Address,
1813 -- Ltype'Length * Ltype'Component_Size;
1814 -- Right'Address,
1815 -- Rtype'Length * Rtype'Component_Size
1816 -- Result'Address);
1817
1818 -- where Left and Right are the Packed_Bytes{1,2,4} operands and
1819 -- the second argument and fourth arguments are the lengths of the
1820 -- operands in bits. Then we replace the expression by a reference
1821 -- to Result.
1822
1823 -- Note that if we are mixing a modular and array operand, everything
1824 -- works fine, since we ensure that the modular representation has the
1825 -- same physical layout as the array representation (that's what the
1826 -- left justified modular stuff in the big-endian case is about).
1827
1828 else
1829 declare
1830 Result_Ent : constant Entity_Id :=
1831 Make_Defining_Identifier (Loc,
1832 Chars => New_Internal_Name ('T'));
1833
1834 E_Id : RE_Id;
1835
1836 begin
1837 if Nkind (N) = N_Op_And then
1838 E_Id := RE_Bit_And;
1839
1840 elsif Nkind (N) = N_Op_Or then
1841 E_Id := RE_Bit_Or;
1842
1843 else -- Nkind (N) = N_Op_Xor
1844 E_Id := RE_Bit_Xor;
1845 end if;
1846
1847 Insert_Actions (N, New_List (
1848
1849 Make_Object_Declaration (Loc,
1850 Defining_Identifier => Result_Ent,
1851 Object_Definition => New_Occurrence_Of (Ltyp, Loc)),
1852
1853 Make_Procedure_Call_Statement (Loc,
1854 Name => New_Occurrence_Of (RTE (E_Id), Loc),
1855 Parameter_Associations => New_List (
1856
1857 Make_Byte_Aligned_Attribute_Reference (Loc,
1858 Attribute_Name => Name_Address,
1859 Prefix => L),
1860
1861 Make_Op_Multiply (Loc,
1862 Left_Opnd =>
1863 Make_Attribute_Reference (Loc,
1864 Prefix =>
1865 New_Occurrence_Of
1866 (Etype (First_Index (Ltyp)), Loc),
1867 Attribute_Name => Name_Range_Length),
1868 Right_Opnd =>
1869 Make_Integer_Literal (Loc, Component_Size (Ltyp))),
1870
1871 Make_Byte_Aligned_Attribute_Reference (Loc,
1872 Attribute_Name => Name_Address,
1873 Prefix => R),
1874
1875 Make_Op_Multiply (Loc,
1876 Left_Opnd =>
1877 Make_Attribute_Reference (Loc,
1878 Prefix =>
1879 New_Occurrence_Of
1880 (Etype (First_Index (Rtyp)), Loc),
1881 Attribute_Name => Name_Range_Length),
1882 Right_Opnd =>
1883 Make_Integer_Literal (Loc, Component_Size (Rtyp))),
1884
1885 Make_Byte_Aligned_Attribute_Reference (Loc,
1886 Attribute_Name => Name_Address,
1887 Prefix => New_Occurrence_Of (Result_Ent, Loc))))));
1888
1889 Rewrite (N,
1890 New_Occurrence_Of (Result_Ent, Loc));
1891 end;
1892 end if;
1893
1894 Analyze_And_Resolve (N, Typ, Suppress => All_Checks);
1895 end Expand_Packed_Boolean_Operator;
1896
1897 -------------------------------------
1898 -- Expand_Packed_Element_Reference --
1899 -------------------------------------
1900
1901 procedure Expand_Packed_Element_Reference (N : Node_Id) is
1902 Loc : constant Source_Ptr := Sloc (N);
1903 Obj : Node_Id;
1904 Atyp : Entity_Id;
1905 PAT : Entity_Id;
1906 Ctyp : Entity_Id;
1907 Csiz : Int;
1908 Shift : Node_Id;
1909 Cmask : Uint;
1910 Lit : Node_Id;
1911 Arg : Node_Id;
1912
1913 begin
1914 -- If not bit packed, we have the enumeration case, which is easily
1915 -- dealt with (just adjust the subscripts of the indexed component)
1916
1917 -- Note: this leaves the result as an indexed component, which is
1918 -- still a variable, so can be used in the assignment case, as is
1919 -- required in the enumeration case.
1920
1921 if not Is_Bit_Packed_Array (Etype (Prefix (N))) then
1922 Setup_Enumeration_Packed_Array_Reference (N);
1923 return;
1924 end if;
1925
1926 -- Remaining processing is for the bit-packed case
1927
1928 Obj := Relocate_Node (Prefix (N));
1929 Convert_To_Actual_Subtype (Obj);
1930 Atyp := Etype (Obj);
1931 PAT := Packed_Array_Type (Atyp);
1932 Ctyp := Component_Type (Atyp);
1933 Csiz := UI_To_Int (Component_Size (Atyp));
1934
1935 -- Case of component size 1,2,4 or any component size for the modular
1936 -- case. These are the cases for which we can inline the code.
1937
1938 if Csiz = 1 or else Csiz = 2 or else Csiz = 4
1939 or else (Present (PAT) and then Is_Modular_Integer_Type (PAT))
1940 then
1941 Setup_Inline_Packed_Array_Reference (N, Atyp, Obj, Cmask, Shift);
1942 Lit := Make_Integer_Literal (Loc, Cmask);
1943 Set_Print_In_Hex (Lit);
1944
1945 -- We generate a shift right to position the field, followed by a
1946 -- masking operation to extract the bit field, and we finally do an
1947 -- unchecked conversion to convert the result to the required target.
1948
1949 -- Note that the unchecked conversion automatically deals with the
1950 -- bias if we are dealing with a biased representation. What will
1951 -- happen is that we temporarily generate the biased representation,
1952 -- but almost immediately that will be converted to the original
1953 -- unbiased component type, and the bias will disappear.
1954
1955 Arg :=
1956 Make_Op_And (Loc,
1957 Left_Opnd => Make_Shift_Right (Obj, Shift),
1958 Right_Opnd => Lit);
1959
1960 -- We neded to analyze this before we do the unchecked convert
1961 -- below, but we need it temporarily attached to the tree for
1962 -- this analysis (hence the temporary Set_Parent call).
1963
1964 Set_Parent (Arg, Parent (N));
1965 Analyze_And_Resolve (Arg);
1966
1967 Rewrite (N,
1968 RJ_Unchecked_Convert_To (Ctyp, Arg));
1969
1970 -- All other component sizes for non-modular case
1971
1972 else
1973 -- We generate
1974
1975 -- Component_Type!(Get_nn (Arr'address, Subscr))
1976
1977 -- where Subscr is the computed linear subscript
1978
1979 declare
1980 Get_nn : Entity_Id;
1981 Subscr : Node_Id;
1982
1983 begin
1984 -- Acquire proper Get entity. We use the aligned or unaligned
1985 -- case as appropriate.
1986
1987 if Known_Aligned_Enough (Obj, Csiz) then
1988 Get_nn := RTE (Get_Id (Csiz));
1989 else
1990 Get_nn := RTE (GetU_Id (Csiz));
1991 end if;
1992
1993 -- Now generate the get reference
1994
1995 Compute_Linear_Subscript (Atyp, N, Subscr);
1996
1997 -- Below we make the assumption that Obj is at least byte
1998 -- aligned, since otherwise its address cannot be taken.
1999 -- The assumption holds since the only arrays that can be
2000 -- misaligned are small packed arrays which are implemented
2001 -- as a modular type, and that is not the case here.
2002
2003 Rewrite (N,
2004 Unchecked_Convert_To (Ctyp,
2005 Make_Function_Call (Loc,
2006 Name => New_Occurrence_Of (Get_nn, Loc),
2007 Parameter_Associations => New_List (
2008 Make_Attribute_Reference (Loc,
2009 Attribute_Name => Name_Address,
2010 Prefix => Obj),
2011 Subscr))));
2012 end;
2013 end if;
2014
2015 Analyze_And_Resolve (N, Ctyp, Suppress => All_Checks);
2016
2017 end Expand_Packed_Element_Reference;
2018
2019 ----------------------
2020 -- Expand_Packed_Eq --
2021 ----------------------
2022
2023 -- Handles expansion of "=" on packed array types
2024
2025 procedure Expand_Packed_Eq (N : Node_Id) is
2026 Loc : constant Source_Ptr := Sloc (N);
2027 L : constant Node_Id := Relocate_Node (Left_Opnd (N));
2028 R : constant Node_Id := Relocate_Node (Right_Opnd (N));
2029
2030 LLexpr : Node_Id;
2031 RLexpr : Node_Id;
2032
2033 Ltyp : Entity_Id;
2034 Rtyp : Entity_Id;
2035 PAT : Entity_Id;
2036
2037 begin
2038 Convert_To_Actual_Subtype (L);
2039 Convert_To_Actual_Subtype (R);
2040 Ltyp := Underlying_Type (Etype (L));
2041 Rtyp := Underlying_Type (Etype (R));
2042
2043 Convert_To_PAT_Type (L);
2044 Convert_To_PAT_Type (R);
2045 PAT := Etype (L);
2046
2047 LLexpr :=
2048 Make_Op_Multiply (Loc,
2049 Left_Opnd =>
2050 Make_Attribute_Reference (Loc,
2051 Attribute_Name => Name_Length,
2052 Prefix => New_Occurrence_Of (Ltyp, Loc)),
2053 Right_Opnd =>
2054 Make_Integer_Literal (Loc, Component_Size (Ltyp)));
2055
2056 RLexpr :=
2057 Make_Op_Multiply (Loc,
2058 Left_Opnd =>
2059 Make_Attribute_Reference (Loc,
2060 Attribute_Name => Name_Length,
2061 Prefix => New_Occurrence_Of (Rtyp, Loc)),
2062 Right_Opnd =>
2063 Make_Integer_Literal (Loc, Component_Size (Rtyp)));
2064
2065 -- For the modular case, we transform the comparison to:
2066
2067 -- Ltyp'Length = Rtyp'Length and then PAT!(L) = PAT!(R)
2068
2069 -- where PAT is the packed array type. This works fine, since in the
2070 -- modular case we guarantee that the unused bits are always zeroes.
2071 -- We do have to compare the lengths because we could be comparing
2072 -- two different subtypes of the same base type.
2073
2074 if Is_Modular_Integer_Type (PAT) then
2075 Rewrite (N,
2076 Make_And_Then (Loc,
2077 Left_Opnd =>
2078 Make_Op_Eq (Loc,
2079 Left_Opnd => LLexpr,
2080 Right_Opnd => RLexpr),
2081
2082 Right_Opnd =>
2083 Make_Op_Eq (Loc,
2084 Left_Opnd => L,
2085 Right_Opnd => R)));
2086
2087 -- For the non-modular case, we call a runtime routine
2088
2089 -- System.Bit_Ops.Bit_Eq
2090 -- (L'Address, L_Length, R'Address, R_Length)
2091
2092 -- where PAT is the packed array type, and the lengths are the lengths
2093 -- in bits of the original packed arrays. This routine takes care of
2094 -- not comparing the unused bits in the last byte.
2095
2096 else
2097 Rewrite (N,
2098 Make_Function_Call (Loc,
2099 Name => New_Occurrence_Of (RTE (RE_Bit_Eq), Loc),
2100 Parameter_Associations => New_List (
2101 Make_Byte_Aligned_Attribute_Reference (Loc,
2102 Attribute_Name => Name_Address,
2103 Prefix => L),
2104
2105 LLexpr,
2106
2107 Make_Byte_Aligned_Attribute_Reference (Loc,
2108 Attribute_Name => Name_Address,
2109 Prefix => R),
2110
2111 RLexpr)));
2112 end if;
2113
2114 Analyze_And_Resolve (N, Standard_Boolean, Suppress => All_Checks);
2115 end Expand_Packed_Eq;
2116
2117 -----------------------
2118 -- Expand_Packed_Not --
2119 -----------------------
2120
2121 -- Handles expansion of "not" on packed array types
2122
2123 procedure Expand_Packed_Not (N : Node_Id) is
2124 Loc : constant Source_Ptr := Sloc (N);
2125 Typ : constant Entity_Id := Etype (N);
2126 Opnd : constant Node_Id := Relocate_Node (Right_Opnd (N));
2127
2128 Rtyp : Entity_Id;
2129 PAT : Entity_Id;
2130 Lit : Node_Id;
2131
2132 begin
2133 Convert_To_Actual_Subtype (Opnd);
2134 Rtyp := Etype (Opnd);
2135
2136 -- First an odd and silly test. We explicitly check for the case
2137 -- where the 'First of the component type is equal to the 'Last of
2138 -- this component type, and if this is the case, we make sure that
2139 -- constraint error is raised. The reason is that the NOT is bound
2140 -- to cause CE in this case, and we will not otherwise catch it.
2141
2142 -- Believe it or not, this was reported as a bug. Note that nearly
2143 -- always, the test will evaluate statically to False, so the code
2144 -- will be statically removed, and no extra overhead caused.
2145
2146 declare
2147 CT : constant Entity_Id := Component_Type (Rtyp);
2148
2149 begin
2150 Insert_Action (N,
2151 Make_Raise_Constraint_Error (Loc,
2152 Condition =>
2153 Make_Op_Eq (Loc,
2154 Left_Opnd =>
2155 Make_Attribute_Reference (Loc,
2156 Prefix => New_Occurrence_Of (CT, Loc),
2157 Attribute_Name => Name_First),
2158
2159 Right_Opnd =>
2160 Make_Attribute_Reference (Loc,
2161 Prefix => New_Occurrence_Of (CT, Loc),
2162 Attribute_Name => Name_Last)),
2163 Reason => CE_Range_Check_Failed));
2164 end;
2165
2166 -- Now that that silliness is taken care of, get packed array type
2167
2168 Convert_To_PAT_Type (Opnd);
2169 PAT := Etype (Opnd);
2170
2171 -- For the case where the packed array type is a modular type,
2172 -- not A expands simply into:
2173
2174 -- rtyp!(PAT!(A) xor mask)
2175
2176 -- where PAT is the packed array type, and mask is a mask of all
2177 -- one bits of length equal to the size of this packed type and
2178 -- rtyp is the actual subtype of the operand
2179
2180 Lit := Make_Integer_Literal (Loc, 2 ** Esize (PAT) - 1);
2181 Set_Print_In_Hex (Lit);
2182
2183 if not Is_Array_Type (PAT) then
2184 Rewrite (N,
2185 Unchecked_Convert_To (Rtyp,
2186 Make_Op_Xor (Loc,
2187 Left_Opnd => Opnd,
2188 Right_Opnd => Lit)));
2189
2190 -- For the array case, we insert the actions
2191
2192 -- Result : Typ;
2193
2194 -- System.Bitops.Bit_Not
2195 -- (Opnd'Address,
2196 -- Typ'Length * Typ'Component_Size;
2197 -- Result'Address);
2198
2199 -- where Opnd is the Packed_Bytes{1,2,4} operand and the second
2200 -- argument is the length of the operand in bits. Then we replace
2201 -- the expression by a reference to Result.
2202
2203 else
2204 declare
2205 Result_Ent : constant Entity_Id :=
2206 Make_Defining_Identifier (Loc,
2207 Chars => New_Internal_Name ('T'));
2208
2209 begin
2210 Insert_Actions (N, New_List (
2211
2212 Make_Object_Declaration (Loc,
2213 Defining_Identifier => Result_Ent,
2214 Object_Definition => New_Occurrence_Of (Rtyp, Loc)),
2215
2216 Make_Procedure_Call_Statement (Loc,
2217 Name => New_Occurrence_Of (RTE (RE_Bit_Not), Loc),
2218 Parameter_Associations => New_List (
2219
2220 Make_Byte_Aligned_Attribute_Reference (Loc,
2221 Attribute_Name => Name_Address,
2222 Prefix => Opnd),
2223
2224 Make_Op_Multiply (Loc,
2225 Left_Opnd =>
2226 Make_Attribute_Reference (Loc,
2227 Prefix =>
2228 New_Occurrence_Of
2229 (Etype (First_Index (Rtyp)), Loc),
2230 Attribute_Name => Name_Range_Length),
2231 Right_Opnd =>
2232 Make_Integer_Literal (Loc, Component_Size (Rtyp))),
2233
2234 Make_Byte_Aligned_Attribute_Reference (Loc,
2235 Attribute_Name => Name_Address,
2236 Prefix => New_Occurrence_Of (Result_Ent, Loc))))));
2237
2238 Rewrite (N,
2239 New_Occurrence_Of (Result_Ent, Loc));
2240 end;
2241 end if;
2242
2243 Analyze_And_Resolve (N, Typ, Suppress => All_Checks);
2244
2245 end Expand_Packed_Not;
2246
2247 -------------------------------------
2248 -- Involves_Packed_Array_Reference --
2249 -------------------------------------
2250
2251 function Involves_Packed_Array_Reference (N : Node_Id) return Boolean is
2252 begin
2253 if Nkind (N) = N_Indexed_Component
2254 and then Is_Bit_Packed_Array (Etype (Prefix (N)))
2255 then
2256 return True;
2257
2258 elsif Nkind (N) = N_Selected_Component then
2259 return Involves_Packed_Array_Reference (Prefix (N));
2260
2261 else
2262 return False;
2263 end if;
2264 end Involves_Packed_Array_Reference;
2265
2266 --------------------------
2267 -- Known_Aligned_Enough --
2268 --------------------------
2269
2270 function Known_Aligned_Enough (Obj : Node_Id; Csiz : Nat) return Boolean is
2271 Typ : constant Entity_Id := Etype (Obj);
2272
2273 function In_Partially_Packed_Record (Comp : Entity_Id) return Boolean;
2274 -- If the component is in a record that contains previous packed
2275 -- components, consider it unaligned because the back-end might
2276 -- choose to pack the rest of the record. Lead to less efficient code,
2277 -- but safer vis-a-vis of back-end choices.
2278
2279 --------------------------------
2280 -- In_Partially_Packed_Record --
2281 --------------------------------
2282
2283 function In_Partially_Packed_Record (Comp : Entity_Id) return Boolean is
2284 Rec_Type : constant Entity_Id := Scope (Comp);
2285 Prev_Comp : Entity_Id;
2286
2287 begin
2288 Prev_Comp := First_Entity (Rec_Type);
2289 while Present (Prev_Comp) loop
2290 if Is_Packed (Etype (Prev_Comp)) then
2291 return True;
2292
2293 elsif Prev_Comp = Comp then
2294 return False;
2295 end if;
2296
2297 Next_Entity (Prev_Comp);
2298 end loop;
2299
2300 return False;
2301 end In_Partially_Packed_Record;
2302
2303 -- Start of processing for Known_Aligned_Enough
2304
2305 begin
2306 -- Odd bit sizes don't need alignment anyway
2307
2308 if Csiz mod 2 = 1 then
2309 return True;
2310
2311 -- If we have a specified alignment, see if it is sufficient, if not
2312 -- then we can't possibly be aligned enough in any case.
2313
2314 elsif Known_Alignment (Etype (Obj)) then
2315 -- Alignment required is 4 if size is a multiple of 4, and
2316 -- 2 otherwise (e.g. 12 bits requires 4, 10 bits requires 2)
2317
2318 if Alignment (Etype (Obj)) < 4 - (Csiz mod 4) then
2319 return False;
2320 end if;
2321 end if;
2322
2323 -- OK, alignment should be sufficient, if object is aligned
2324
2325 -- If object is strictly aligned, then it is definitely aligned
2326
2327 if Strict_Alignment (Typ) then
2328 return True;
2329
2330 -- Case of subscripted array reference
2331
2332 elsif Nkind (Obj) = N_Indexed_Component then
2333
2334 -- If we have a pointer to an array, then this is definitely
2335 -- aligned, because pointers always point to aligned versions.
2336
2337 if Is_Access_Type (Etype (Prefix (Obj))) then
2338 return True;
2339
2340 -- Otherwise, go look at the prefix
2341
2342 else
2343 return Known_Aligned_Enough (Prefix (Obj), Csiz);
2344 end if;
2345
2346 -- Case of record field
2347
2348 elsif Nkind (Obj) = N_Selected_Component then
2349
2350 -- What is significant here is whether the record type is packed
2351
2352 if Is_Record_Type (Etype (Prefix (Obj)))
2353 and then Is_Packed (Etype (Prefix (Obj)))
2354 then
2355 return False;
2356
2357 -- Or the component has a component clause which might cause
2358 -- the component to become unaligned (we can't tell if the
2359 -- backend is doing alignment computations).
2360
2361 elsif Present (Component_Clause (Entity (Selector_Name (Obj)))) then
2362 return False;
2363
2364 elsif In_Partially_Packed_Record (Entity (Selector_Name (Obj))) then
2365 return False;
2366
2367 -- In all other cases, go look at prefix
2368
2369 else
2370 return Known_Aligned_Enough (Prefix (Obj), Csiz);
2371 end if;
2372
2373 elsif Nkind (Obj) = N_Type_Conversion then
2374 return Known_Aligned_Enough (Expression (Obj), Csiz);
2375
2376 -- For a formal parameter, it is safer to assume that it is not
2377 -- aligned, because the formal may be unconstrained while the actual
2378 -- is constrained. In this situation, a small constrained packed
2379 -- array, represented in modular form, may be unaligned.
2380
2381 elsif Is_Entity_Name (Obj) then
2382 return not Is_Formal (Entity (Obj));
2383 else
2384
2385 -- If none of the above, must be aligned
2386 return True;
2387 end if;
2388 end Known_Aligned_Enough;
2389
2390 ---------------------
2391 -- Make_Shift_Left --
2392 ---------------------
2393
2394 function Make_Shift_Left (N : Node_Id; S : Node_Id) return Node_Id is
2395 Nod : Node_Id;
2396
2397 begin
2398 if Compile_Time_Known_Value (S) and then Expr_Value (S) = 0 then
2399 return N;
2400 else
2401 Nod :=
2402 Make_Op_Shift_Left (Sloc (N),
2403 Left_Opnd => N,
2404 Right_Opnd => S);
2405 Set_Shift_Count_OK (Nod, True);
2406 return Nod;
2407 end if;
2408 end Make_Shift_Left;
2409
2410 ----------------------
2411 -- Make_Shift_Right --
2412 ----------------------
2413
2414 function Make_Shift_Right (N : Node_Id; S : Node_Id) return Node_Id is
2415 Nod : Node_Id;
2416
2417 begin
2418 if Compile_Time_Known_Value (S) and then Expr_Value (S) = 0 then
2419 return N;
2420 else
2421 Nod :=
2422 Make_Op_Shift_Right (Sloc (N),
2423 Left_Opnd => N,
2424 Right_Opnd => S);
2425 Set_Shift_Count_OK (Nod, True);
2426 return Nod;
2427 end if;
2428 end Make_Shift_Right;
2429
2430 -----------------------------
2431 -- RJ_Unchecked_Convert_To --
2432 -----------------------------
2433
2434 function RJ_Unchecked_Convert_To
2435 (Typ : Entity_Id;
2436 Expr : Node_Id) return Node_Id
2437 is
2438 Source_Typ : constant Entity_Id := Etype (Expr);
2439 Target_Typ : constant Entity_Id := Typ;
2440
2441 Src : Node_Id := Expr;
2442
2443 Source_Siz : Nat;
2444 Target_Siz : Nat;
2445
2446 begin
2447 Source_Siz := UI_To_Int (RM_Size (Source_Typ));
2448 Target_Siz := UI_To_Int (RM_Size (Target_Typ));
2449
2450 -- First step, if the source type is not a discrete type, then we
2451 -- first convert to a modular type of the source length, since
2452 -- otherwise, on a big-endian machine, we get left-justification.
2453 -- We do it for little-endian machines as well, because there might
2454 -- be junk bits that are not cleared if the type is not numeric.
2455
2456 if Source_Siz /= Target_Siz
2457 and then not Is_Discrete_Type (Source_Typ)
2458 then
2459 Src := Unchecked_Convert_To (RTE (Bits_Id (Source_Siz)), Src);
2460 end if;
2461
2462 -- In the big endian case, if the lengths of the two types differ,
2463 -- then we must worry about possible left justification in the
2464 -- conversion, and avoiding that is what this is all about.
2465
2466 if Bytes_Big_Endian and then Source_Siz /= Target_Siz then
2467
2468 -- Next step. If the target is not a discrete type, then we first
2469 -- convert to a modular type of the target length, since
2470 -- otherwise, on a big-endian machine, we get left-justification.
2471
2472 if not Is_Discrete_Type (Target_Typ) then
2473 Src := Unchecked_Convert_To (RTE (Bits_Id (Target_Siz)), Src);
2474 end if;
2475 end if;
2476
2477 -- And now we can do the final conversion to the target type
2478
2479 return Unchecked_Convert_To (Target_Typ, Src);
2480 end RJ_Unchecked_Convert_To;
2481
2482 ----------------------------------------------
2483 -- Setup_Enumeration_Packed_Array_Reference --
2484 ----------------------------------------------
2485
2486 -- All we have to do here is to find the subscripts that correspond
2487 -- to the index positions that have non-standard enumeration types
2488 -- and insert a Pos attribute to get the proper subscript value.
2489
2490 -- Finally the prefix must be uncheck converted to the corresponding
2491 -- packed array type.
2492
2493 -- Note that the component type is unchanged, so we do not need to
2494 -- fiddle with the types (Gigi always automatically takes the packed
2495 -- array type if it is set, as it will be in this case).
2496
2497 procedure Setup_Enumeration_Packed_Array_Reference (N : Node_Id) is
2498 Pfx : constant Node_Id := Prefix (N);
2499 Typ : constant Entity_Id := Etype (N);
2500 Exprs : constant List_Id := Expressions (N);
2501 Expr : Node_Id;
2502
2503 begin
2504 -- If the array is unconstrained, then we replace the array
2505 -- reference with its actual subtype. This actual subtype will
2506 -- have a packed array type with appropriate bounds.
2507
2508 if not Is_Constrained (Packed_Array_Type (Etype (Pfx))) then
2509 Convert_To_Actual_Subtype (Pfx);
2510 end if;
2511
2512 Expr := First (Exprs);
2513 while Present (Expr) loop
2514 declare
2515 Loc : constant Source_Ptr := Sloc (Expr);
2516 Expr_Typ : constant Entity_Id := Etype (Expr);
2517
2518 begin
2519 if Is_Enumeration_Type (Expr_Typ)
2520 and then Has_Non_Standard_Rep (Expr_Typ)
2521 then
2522 Rewrite (Expr,
2523 Make_Attribute_Reference (Loc,
2524 Prefix => New_Occurrence_Of (Expr_Typ, Loc),
2525 Attribute_Name => Name_Pos,
2526 Expressions => New_List (Relocate_Node (Expr))));
2527 Analyze_And_Resolve (Expr, Standard_Natural);
2528 end if;
2529 end;
2530
2531 Next (Expr);
2532 end loop;
2533
2534 Rewrite (N,
2535 Make_Indexed_Component (Sloc (N),
2536 Prefix =>
2537 Unchecked_Convert_To (Packed_Array_Type (Etype (Pfx)), Pfx),
2538 Expressions => Exprs));
2539
2540 Analyze_And_Resolve (N, Typ);
2541
2542 end Setup_Enumeration_Packed_Array_Reference;
2543
2544 -----------------------------------------
2545 -- Setup_Inline_Packed_Array_Reference --
2546 -----------------------------------------
2547
2548 procedure Setup_Inline_Packed_Array_Reference
2549 (N : Node_Id;
2550 Atyp : Entity_Id;
2551 Obj : in out Node_Id;
2552 Cmask : out Uint;
2553 Shift : out Node_Id)
2554 is
2555 Loc : constant Source_Ptr := Sloc (N);
2556 PAT : Entity_Id;
2557 Otyp : Entity_Id;
2558 Csiz : Uint;
2559 Osiz : Uint;
2560
2561 begin
2562 Csiz := Component_Size (Atyp);
2563
2564 Convert_To_PAT_Type (Obj);
2565 PAT := Etype (Obj);
2566
2567 Cmask := 2 ** Csiz - 1;
2568
2569 if Is_Array_Type (PAT) then
2570 Otyp := Component_Type (PAT);
2571 Osiz := Component_Size (PAT);
2572
2573 else
2574 Otyp := PAT;
2575
2576 -- In the case where the PAT is a modular type, we want the actual
2577 -- size in bits of the modular value we use. This is neither the
2578 -- Object_Size nor the Value_Size, either of which may have been
2579 -- reset to strange values, but rather the minimum size. Note that
2580 -- since this is a modular type with full range, the issue of
2581 -- biased representation does not arise.
2582
2583 Osiz := UI_From_Int (Minimum_Size (Otyp));
2584 end if;
2585
2586 Compute_Linear_Subscript (Atyp, N, Shift);
2587
2588 -- If the component size is not 1, then the subscript must be
2589 -- multiplied by the component size to get the shift count.
2590
2591 if Csiz /= 1 then
2592 Shift :=
2593 Make_Op_Multiply (Loc,
2594 Left_Opnd => Make_Integer_Literal (Loc, Csiz),
2595 Right_Opnd => Shift);
2596 end if;
2597
2598 -- If we have the array case, then this shift count must be broken
2599 -- down into a byte subscript, and a shift within the byte.
2600
2601 if Is_Array_Type (PAT) then
2602
2603 declare
2604 New_Shift : Node_Id;
2605
2606 begin
2607 -- We must analyze shift, since we will duplicate it
2608
2609 Set_Parent (Shift, N);
2610 Analyze_And_Resolve
2611 (Shift, Standard_Integer, Suppress => All_Checks);
2612
2613 -- The shift count within the word is
2614 -- shift mod Osiz
2615
2616 New_Shift :=
2617 Make_Op_Mod (Loc,
2618 Left_Opnd => Duplicate_Subexpr (Shift),
2619 Right_Opnd => Make_Integer_Literal (Loc, Osiz));
2620
2621 -- The subscript to be used on the PAT array is
2622 -- shift / Osiz
2623
2624 Obj :=
2625 Make_Indexed_Component (Loc,
2626 Prefix => Obj,
2627 Expressions => New_List (
2628 Make_Op_Divide (Loc,
2629 Left_Opnd => Duplicate_Subexpr (Shift),
2630 Right_Opnd => Make_Integer_Literal (Loc, Osiz))));
2631
2632 Shift := New_Shift;
2633 end;
2634
2635 -- For the modular integer case, the object to be manipulated is
2636 -- the entire array, so Obj is unchanged. Note that we will reset
2637 -- its type to PAT before returning to the caller.
2638
2639 else
2640 null;
2641 end if;
2642
2643 -- The one remaining step is to modify the shift count for the
2644 -- big-endian case. Consider the following example in a byte:
2645
2646 -- xxxxxxxx bits of byte
2647 -- vvvvvvvv bits of value
2648 -- 33221100 little-endian numbering
2649 -- 00112233 big-endian numbering
2650
2651 -- Here we have the case of 2-bit fields
2652
2653 -- For the little-endian case, we already have the proper shift
2654 -- count set, e.g. for element 2, the shift count is 2*2 = 4.
2655
2656 -- For the big endian case, we have to adjust the shift count,
2657 -- computing it as (N - F) - shift, where N is the number of bits
2658 -- in an element of the array used to implement the packed array,
2659 -- F is the number of bits in a source level array element, and
2660 -- shift is the count so far computed.
2661
2662 if Bytes_Big_Endian then
2663 Shift :=
2664 Make_Op_Subtract (Loc,
2665 Left_Opnd => Make_Integer_Literal (Loc, Osiz - Csiz),
2666 Right_Opnd => Shift);
2667 end if;
2668
2669 Set_Parent (Shift, N);
2670 Set_Parent (Obj, N);
2671 Analyze_And_Resolve (Obj, Otyp, Suppress => All_Checks);
2672 Analyze_And_Resolve (Shift, Standard_Integer, Suppress => All_Checks);
2673
2674 -- Make sure final type of object is the appropriate packed type
2675
2676 Set_Etype (Obj, Otyp);
2677
2678 end Setup_Inline_Packed_Array_Reference;
2679
2680 end Exp_Pakd;
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