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[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) 1992-2012, 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 3, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING3. If not, go to --
19 -- http://www.gnu.org/licenses for a complete copy of the license. --
20 -- --
21 -- GNAT was originally developed by the GNAT team at New York University. --
22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
23 -- --
24 ------------------------------------------------------------------------------
25
26 with Atree; use Atree;
27 with Checks; use Checks;
28 with Einfo; use Einfo;
29 with Errout; use Errout;
30 with Exp_Dbug; use Exp_Dbug;
31 with Exp_Util; use Exp_Util;
32 with Layout; use Layout;
33 with Namet; use Namet;
34 with Nlists; use Nlists;
35 with Nmake; use Nmake;
36 with Opt; use Opt;
37 with Rtsfind; use Rtsfind;
38 with Sem; use Sem;
39 with Sem_Aux; use Sem_Aux;
40 with Sem_Ch3; use Sem_Ch3;
41 with Sem_Ch8; use Sem_Ch8;
42 with Sem_Ch13; use Sem_Ch13;
43 with Sem_Eval; use Sem_Eval;
44 with Sem_Res; use Sem_Res;
45 with Sem_Util; use Sem_Util;
46 with Sinfo; use Sinfo;
47 with Snames; use Snames;
48 with Stand; use Stand;
49 with Targparm; use Targparm;
50 with Tbuild; use Tbuild;
51 with Ttypes; use Ttypes;
52 with Uintp; use Uintp;
53
54 package body Exp_Pakd is
55
56 ---------------------------
57 -- Endian Considerations --
58 ---------------------------
59
60 -- As described in the specification, bit numbering in a packed array
61 -- is consistent with bit numbering in a record representation clause,
62 -- and hence dependent on the endianness of the machine:
63
64 -- For little-endian machines, element zero is at the right hand end
65 -- (low order end) of a bit field.
66
67 -- For big-endian machines, element zero is at the left hand end
68 -- (high order end) of a bit field.
69
70 -- The shifts that are used to right justify a field therefore differ in
71 -- the two cases. For the little-endian case, we can simply use the bit
72 -- number (i.e. the element number * element size) as the count for a right
73 -- shift. For the big-endian case, we have to subtract the shift count from
74 -- an appropriate constant to use in the right shift. We use rotates
75 -- instead of shifts (which is necessary in the store case to preserve
76 -- other fields), and we expect that the backend will be able to change the
77 -- right rotate into a left rotate, avoiding the subtract, if the machine
78 -- architecture provides such an instruction.
79
80 ----------------------------------------------
81 -- Entity Tables for Packed Access Routines --
82 ----------------------------------------------
83
84 -- For the cases of component size = 3,5-7,9-15,17-31,33-63 we call library
85 -- routines. This table provides the entity for the proper routine.
86
87 type E_Array is array (Int range 01 .. 63) of RE_Id;
88
89 -- Array of Bits_nn entities. Note that we do not use library routines
90 -- for the 8-bit and 16-bit cases, but we still fill in the table, using
91 -- entries from System.Unsigned, because we also use this table for
92 -- certain special unchecked conversions in the big-endian case.
93
94 Bits_Id : constant E_Array :=
95 (01 => RE_Bits_1,
96 02 => RE_Bits_2,
97 03 => RE_Bits_03,
98 04 => RE_Bits_4,
99 05 => RE_Bits_05,
100 06 => RE_Bits_06,
101 07 => RE_Bits_07,
102 08 => RE_Unsigned_8,
103 09 => RE_Bits_09,
104 10 => RE_Bits_10,
105 11 => RE_Bits_11,
106 12 => RE_Bits_12,
107 13 => RE_Bits_13,
108 14 => RE_Bits_14,
109 15 => RE_Bits_15,
110 16 => RE_Unsigned_16,
111 17 => RE_Bits_17,
112 18 => RE_Bits_18,
113 19 => RE_Bits_19,
114 20 => RE_Bits_20,
115 21 => RE_Bits_21,
116 22 => RE_Bits_22,
117 23 => RE_Bits_23,
118 24 => RE_Bits_24,
119 25 => RE_Bits_25,
120 26 => RE_Bits_26,
121 27 => RE_Bits_27,
122 28 => RE_Bits_28,
123 29 => RE_Bits_29,
124 30 => RE_Bits_30,
125 31 => RE_Bits_31,
126 32 => RE_Unsigned_32,
127 33 => RE_Bits_33,
128 34 => RE_Bits_34,
129 35 => RE_Bits_35,
130 36 => RE_Bits_36,
131 37 => RE_Bits_37,
132 38 => RE_Bits_38,
133 39 => RE_Bits_39,
134 40 => RE_Bits_40,
135 41 => RE_Bits_41,
136 42 => RE_Bits_42,
137 43 => RE_Bits_43,
138 44 => RE_Bits_44,
139 45 => RE_Bits_45,
140 46 => RE_Bits_46,
141 47 => RE_Bits_47,
142 48 => RE_Bits_48,
143 49 => RE_Bits_49,
144 50 => RE_Bits_50,
145 51 => RE_Bits_51,
146 52 => RE_Bits_52,
147 53 => RE_Bits_53,
148 54 => RE_Bits_54,
149 55 => RE_Bits_55,
150 56 => RE_Bits_56,
151 57 => RE_Bits_57,
152 58 => RE_Bits_58,
153 59 => RE_Bits_59,
154 60 => RE_Bits_60,
155 61 => RE_Bits_61,
156 62 => RE_Bits_62,
157 63 => RE_Bits_63);
158
159 -- Array of Get routine entities. These are used to obtain an element from
160 -- a packed array. The N'th entry is used to obtain elements from a packed
161 -- array whose component size is N. RE_Null is used as a null entry, for
162 -- the cases where a library routine is not used.
163
164 Get_Id : constant E_Array :=
165 (01 => RE_Null,
166 02 => RE_Null,
167 03 => RE_Get_03,
168 04 => RE_Null,
169 05 => RE_Get_05,
170 06 => RE_Get_06,
171 07 => RE_Get_07,
172 08 => RE_Null,
173 09 => RE_Get_09,
174 10 => RE_Get_10,
175 11 => RE_Get_11,
176 12 => RE_Get_12,
177 13 => RE_Get_13,
178 14 => RE_Get_14,
179 15 => RE_Get_15,
180 16 => RE_Null,
181 17 => RE_Get_17,
182 18 => RE_Get_18,
183 19 => RE_Get_19,
184 20 => RE_Get_20,
185 21 => RE_Get_21,
186 22 => RE_Get_22,
187 23 => RE_Get_23,
188 24 => RE_Get_24,
189 25 => RE_Get_25,
190 26 => RE_Get_26,
191 27 => RE_Get_27,
192 28 => RE_Get_28,
193 29 => RE_Get_29,
194 30 => RE_Get_30,
195 31 => RE_Get_31,
196 32 => RE_Null,
197 33 => RE_Get_33,
198 34 => RE_Get_34,
199 35 => RE_Get_35,
200 36 => RE_Get_36,
201 37 => RE_Get_37,
202 38 => RE_Get_38,
203 39 => RE_Get_39,
204 40 => RE_Get_40,
205 41 => RE_Get_41,
206 42 => RE_Get_42,
207 43 => RE_Get_43,
208 44 => RE_Get_44,
209 45 => RE_Get_45,
210 46 => RE_Get_46,
211 47 => RE_Get_47,
212 48 => RE_Get_48,
213 49 => RE_Get_49,
214 50 => RE_Get_50,
215 51 => RE_Get_51,
216 52 => RE_Get_52,
217 53 => RE_Get_53,
218 54 => RE_Get_54,
219 55 => RE_Get_55,
220 56 => RE_Get_56,
221 57 => RE_Get_57,
222 58 => RE_Get_58,
223 59 => RE_Get_59,
224 60 => RE_Get_60,
225 61 => RE_Get_61,
226 62 => RE_Get_62,
227 63 => RE_Get_63);
228
229 -- Array of Get routine entities to be used in the case where the packed
230 -- array is itself a component of a packed structure, and therefore may not
231 -- be fully aligned. This only affects the even sizes, since for the odd
232 -- sizes, we do not get any fixed alignment in any case.
233
234 GetU_Id : constant E_Array :=
235 (01 => RE_Null,
236 02 => RE_Null,
237 03 => RE_Get_03,
238 04 => RE_Null,
239 05 => RE_Get_05,
240 06 => RE_GetU_06,
241 07 => RE_Get_07,
242 08 => RE_Null,
243 09 => RE_Get_09,
244 10 => RE_GetU_10,
245 11 => RE_Get_11,
246 12 => RE_GetU_12,
247 13 => RE_Get_13,
248 14 => RE_GetU_14,
249 15 => RE_Get_15,
250 16 => RE_Null,
251 17 => RE_Get_17,
252 18 => RE_GetU_18,
253 19 => RE_Get_19,
254 20 => RE_GetU_20,
255 21 => RE_Get_21,
256 22 => RE_GetU_22,
257 23 => RE_Get_23,
258 24 => RE_GetU_24,
259 25 => RE_Get_25,
260 26 => RE_GetU_26,
261 27 => RE_Get_27,
262 28 => RE_GetU_28,
263 29 => RE_Get_29,
264 30 => RE_GetU_30,
265 31 => RE_Get_31,
266 32 => RE_Null,
267 33 => RE_Get_33,
268 34 => RE_GetU_34,
269 35 => RE_Get_35,
270 36 => RE_GetU_36,
271 37 => RE_Get_37,
272 38 => RE_GetU_38,
273 39 => RE_Get_39,
274 40 => RE_GetU_40,
275 41 => RE_Get_41,
276 42 => RE_GetU_42,
277 43 => RE_Get_43,
278 44 => RE_GetU_44,
279 45 => RE_Get_45,
280 46 => RE_GetU_46,
281 47 => RE_Get_47,
282 48 => RE_GetU_48,
283 49 => RE_Get_49,
284 50 => RE_GetU_50,
285 51 => RE_Get_51,
286 52 => RE_GetU_52,
287 53 => RE_Get_53,
288 54 => RE_GetU_54,
289 55 => RE_Get_55,
290 56 => RE_GetU_56,
291 57 => RE_Get_57,
292 58 => RE_GetU_58,
293 59 => RE_Get_59,
294 60 => RE_GetU_60,
295 61 => RE_Get_61,
296 62 => RE_GetU_62,
297 63 => RE_Get_63);
298
299 -- Array of Set routine entities. These are used to assign an element of a
300 -- packed array. The N'th entry is used to assign elements for a packed
301 -- array whose component size is N. RE_Null is used as a null entry, for
302 -- the cases where a library routine is not used.
303
304 Set_Id : constant E_Array :=
305 (01 => RE_Null,
306 02 => RE_Null,
307 03 => RE_Set_03,
308 04 => RE_Null,
309 05 => RE_Set_05,
310 06 => RE_Set_06,
311 07 => RE_Set_07,
312 08 => RE_Null,
313 09 => RE_Set_09,
314 10 => RE_Set_10,
315 11 => RE_Set_11,
316 12 => RE_Set_12,
317 13 => RE_Set_13,
318 14 => RE_Set_14,
319 15 => RE_Set_15,
320 16 => RE_Null,
321 17 => RE_Set_17,
322 18 => RE_Set_18,
323 19 => RE_Set_19,
324 20 => RE_Set_20,
325 21 => RE_Set_21,
326 22 => RE_Set_22,
327 23 => RE_Set_23,
328 24 => RE_Set_24,
329 25 => RE_Set_25,
330 26 => RE_Set_26,
331 27 => RE_Set_27,
332 28 => RE_Set_28,
333 29 => RE_Set_29,
334 30 => RE_Set_30,
335 31 => RE_Set_31,
336 32 => RE_Null,
337 33 => RE_Set_33,
338 34 => RE_Set_34,
339 35 => RE_Set_35,
340 36 => RE_Set_36,
341 37 => RE_Set_37,
342 38 => RE_Set_38,
343 39 => RE_Set_39,
344 40 => RE_Set_40,
345 41 => RE_Set_41,
346 42 => RE_Set_42,
347 43 => RE_Set_43,
348 44 => RE_Set_44,
349 45 => RE_Set_45,
350 46 => RE_Set_46,
351 47 => RE_Set_47,
352 48 => RE_Set_48,
353 49 => RE_Set_49,
354 50 => RE_Set_50,
355 51 => RE_Set_51,
356 52 => RE_Set_52,
357 53 => RE_Set_53,
358 54 => RE_Set_54,
359 55 => RE_Set_55,
360 56 => RE_Set_56,
361 57 => RE_Set_57,
362 58 => RE_Set_58,
363 59 => RE_Set_59,
364 60 => RE_Set_60,
365 61 => RE_Set_61,
366 62 => RE_Set_62,
367 63 => RE_Set_63);
368
369 -- Array of Set routine entities to be used in the case where the packed
370 -- array is itself a component of a packed structure, and therefore may not
371 -- be fully aligned. This only affects the even sizes, since for the odd
372 -- sizes, we do not get any fixed alignment in any case.
373
374 SetU_Id : constant E_Array :=
375 (01 => RE_Null,
376 02 => RE_Null,
377 03 => RE_Set_03,
378 04 => RE_Null,
379 05 => RE_Set_05,
380 06 => RE_SetU_06,
381 07 => RE_Set_07,
382 08 => RE_Null,
383 09 => RE_Set_09,
384 10 => RE_SetU_10,
385 11 => RE_Set_11,
386 12 => RE_SetU_12,
387 13 => RE_Set_13,
388 14 => RE_SetU_14,
389 15 => RE_Set_15,
390 16 => RE_Null,
391 17 => RE_Set_17,
392 18 => RE_SetU_18,
393 19 => RE_Set_19,
394 20 => RE_SetU_20,
395 21 => RE_Set_21,
396 22 => RE_SetU_22,
397 23 => RE_Set_23,
398 24 => RE_SetU_24,
399 25 => RE_Set_25,
400 26 => RE_SetU_26,
401 27 => RE_Set_27,
402 28 => RE_SetU_28,
403 29 => RE_Set_29,
404 30 => RE_SetU_30,
405 31 => RE_Set_31,
406 32 => RE_Null,
407 33 => RE_Set_33,
408 34 => RE_SetU_34,
409 35 => RE_Set_35,
410 36 => RE_SetU_36,
411 37 => RE_Set_37,
412 38 => RE_SetU_38,
413 39 => RE_Set_39,
414 40 => RE_SetU_40,
415 41 => RE_Set_41,
416 42 => RE_SetU_42,
417 43 => RE_Set_43,
418 44 => RE_SetU_44,
419 45 => RE_Set_45,
420 46 => RE_SetU_46,
421 47 => RE_Set_47,
422 48 => RE_SetU_48,
423 49 => RE_Set_49,
424 50 => RE_SetU_50,
425 51 => RE_Set_51,
426 52 => RE_SetU_52,
427 53 => RE_Set_53,
428 54 => RE_SetU_54,
429 55 => RE_Set_55,
430 56 => RE_SetU_56,
431 57 => RE_Set_57,
432 58 => RE_SetU_58,
433 59 => RE_Set_59,
434 60 => RE_SetU_60,
435 61 => RE_Set_61,
436 62 => RE_SetU_62,
437 63 => RE_Set_63);
438
439 -----------------------
440 -- Local Subprograms --
441 -----------------------
442
443 procedure Compute_Linear_Subscript
444 (Atyp : Entity_Id;
445 N : Node_Id;
446 Subscr : out Node_Id);
447 -- Given a constrained array type Atyp, and an indexed component node N
448 -- referencing an array object of this type, build an expression of type
449 -- Standard.Integer representing the zero-based linear subscript value.
450 -- This expression includes any required range checks.
451
452 procedure Convert_To_PAT_Type (Aexp : Node_Id);
453 -- Given an expression of a packed array type, builds a corresponding
454 -- expression whose type is the implementation type used to represent
455 -- the packed array. Aexp is analyzed and resolved on entry and on exit.
456
457 procedure Get_Base_And_Bit_Offset
458 (N : Node_Id;
459 Base : out Node_Id;
460 Offset : out Node_Id);
461 -- Given a node N for a name which involves a packed array reference,
462 -- return the base object of the reference and build an expression of
463 -- type Standard.Integer representing the zero-based offset in bits
464 -- from Base'Address to the first bit of the reference.
465
466 function Known_Aligned_Enough (Obj : Node_Id; Csiz : Nat) return Boolean;
467 -- There are two versions of the Set routines, the ones used when the
468 -- object is known to be sufficiently well aligned given the number of
469 -- bits, and the ones used when the object is not known to be aligned.
470 -- This routine is used to determine which set to use. Obj is a reference
471 -- to the object, and Csiz is the component size of the packed array.
472 -- True is returned if the alignment of object is known to be sufficient,
473 -- defined as 1 for odd bit sizes, 4 for bit sizes divisible by 4, and
474 -- 2 otherwise.
475
476 function Make_Shift_Left (N : Node_Id; S : Node_Id) return Node_Id;
477 -- Build a left shift node, checking for the case of a shift count of zero
478
479 function Make_Shift_Right (N : Node_Id; S : Node_Id) return Node_Id;
480 -- Build a right shift node, checking for the case of a shift count of zero
481
482 function RJ_Unchecked_Convert_To
483 (Typ : Entity_Id;
484 Expr : Node_Id) return Node_Id;
485 -- The packed array code does unchecked conversions which in some cases
486 -- may involve non-discrete types with differing sizes. The semantics of
487 -- such conversions is potentially endian dependent, and the effect we
488 -- want here for such a conversion is to do the conversion in size as
489 -- though numeric items are involved, and we extend or truncate on the
490 -- left side. This happens naturally in the little-endian case, but in
491 -- the big endian case we can get left justification, when what we want
492 -- is right justification. This routine does the unchecked conversion in
493 -- a stepwise manner to ensure that it gives the expected result. Hence
494 -- the name (RJ = Right justified). The parameters Typ and Expr are as
495 -- for the case of a normal Unchecked_Convert_To call.
496
497 procedure Setup_Enumeration_Packed_Array_Reference (N : Node_Id);
498 -- This routine is called in the Get and Set case for arrays that are
499 -- packed but not bit-packed, meaning that they have at least one
500 -- subscript that is of an enumeration type with a non-standard
501 -- representation. This routine modifies the given node to properly
502 -- reference the corresponding packed array type.
503
504 procedure Setup_Inline_Packed_Array_Reference
505 (N : Node_Id;
506 Atyp : Entity_Id;
507 Obj : in out Node_Id;
508 Cmask : out Uint;
509 Shift : out Node_Id);
510 -- This procedure performs common processing on the N_Indexed_Component
511 -- parameter given as N, whose prefix is a reference to a packed array.
512 -- This is used for the get and set when the component size is 1, 2, 4,
513 -- or for other component sizes when the packed array type is a modular
514 -- type (i.e. the cases that are handled with inline code).
515 --
516 -- On entry:
517 --
518 -- N is the N_Indexed_Component node for the packed array reference
519 --
520 -- Atyp is the constrained array type (the actual subtype has been
521 -- computed if necessary to obtain the constraints, but this is still
522 -- the original array type, not the Packed_Array_Type value).
523 --
524 -- Obj is the object which is to be indexed. It is always of type Atyp.
525 --
526 -- On return:
527 --
528 -- Obj is the object containing the desired bit field. It is of type
529 -- Unsigned, Long_Unsigned, or Long_Long_Unsigned, and is either the
530 -- entire value, for the small static case, or the proper selected byte
531 -- from the array in the large or dynamic case. This node is analyzed
532 -- and resolved on return.
533 --
534 -- Shift is a node representing the shift count to be used in the
535 -- rotate right instruction that positions the field for access.
536 -- This node is analyzed and resolved on return.
537 --
538 -- Cmask is a mask corresponding to the width of the component field.
539 -- Its value is 2 ** Csize - 1 (e.g. 2#1111# for component size of 4).
540 --
541 -- Note: in some cases the call to this routine may generate actions
542 -- (for handling multi-use references and the generation of the packed
543 -- array type on the fly). Such actions are inserted into the tree
544 -- directly using Insert_Action.
545
546 function Byte_Swap (N : Node_Id) return Node_Id;
547 -- Wrap N in a call to a byte swapping function, with appropriate type
548 -- conversions.
549
550 ---------------
551 -- Byte_Swap --
552 ---------------
553
554 function Byte_Swap (N : Node_Id) return Node_Id is
555 Loc : constant Source_Ptr := Sloc (N);
556 T : constant Entity_Id := Etype (N);
557 Swap_RE : RE_Id;
558 Swap_F : Entity_Id;
559
560 begin
561 pragma Assert (Esize (T) > 8);
562
563 if Esize (T) <= 16 then
564 Swap_RE := RE_Bswap_16;
565 elsif Esize (T) <= 32 then
566 Swap_RE := RE_Bswap_32;
567 else pragma Assert (Esize (T) <= 64);
568 Swap_RE := RE_Bswap_64;
569 end if;
570
571 Swap_F := RTE (Swap_RE);
572
573 return
574 Unchecked_Convert_To (T,
575 Make_Function_Call (Loc,
576 Name => New_Occurrence_Of (Swap_F, Loc),
577 Parameter_Associations =>
578 New_List (Unchecked_Convert_To (Etype (Swap_F), N))));
579 end Byte_Swap;
580
581 ------------------------------
582 -- Compute_Linear_Subscript --
583 ------------------------------
584
585 procedure Compute_Linear_Subscript
586 (Atyp : Entity_Id;
587 N : Node_Id;
588 Subscr : out Node_Id)
589 is
590 Loc : constant Source_Ptr := Sloc (N);
591 Oldsub : Node_Id;
592 Newsub : Node_Id;
593 Indx : Node_Id;
594 Styp : Entity_Id;
595
596 begin
597 Subscr := Empty;
598
599 -- Loop through dimensions
600
601 Indx := First_Index (Atyp);
602 Oldsub := First (Expressions (N));
603
604 while Present (Indx) loop
605 Styp := Etype (Indx);
606 Newsub := Relocate_Node (Oldsub);
607
608 -- Get expression for the subscript value. First, if Do_Range_Check
609 -- is set on a subscript, then we must do a range check against the
610 -- original bounds (not the bounds of the packed array type). We do
611 -- this by introducing a subtype conversion.
612
613 if Do_Range_Check (Newsub)
614 and then Etype (Newsub) /= Styp
615 then
616 Newsub := Convert_To (Styp, Newsub);
617 end if;
618
619 -- Now evolve the expression for the subscript. First convert
620 -- the subscript to be zero based and of an integer type.
621
622 -- Case of integer type, where we just subtract to get lower bound
623
624 if Is_Integer_Type (Styp) then
625
626 -- If length of integer type is smaller than standard integer,
627 -- then we convert to integer first, then do the subtract
628
629 -- Integer (subscript) - Integer (Styp'First)
630
631 if Esize (Styp) < Esize (Standard_Integer) then
632 Newsub :=
633 Make_Op_Subtract (Loc,
634 Left_Opnd => Convert_To (Standard_Integer, Newsub),
635 Right_Opnd =>
636 Convert_To (Standard_Integer,
637 Make_Attribute_Reference (Loc,
638 Prefix => New_Occurrence_Of (Styp, Loc),
639 Attribute_Name => Name_First)));
640
641 -- For larger integer types, subtract first, then convert to
642 -- integer, this deals with strange long long integer bounds.
643
644 -- Integer (subscript - Styp'First)
645
646 else
647 Newsub :=
648 Convert_To (Standard_Integer,
649 Make_Op_Subtract (Loc,
650 Left_Opnd => Newsub,
651 Right_Opnd =>
652 Make_Attribute_Reference (Loc,
653 Prefix => New_Occurrence_Of (Styp, Loc),
654 Attribute_Name => Name_First)));
655 end if;
656
657 -- For the enumeration case, we have to use 'Pos to get the value
658 -- to work with before subtracting the lower bound.
659
660 -- Integer (Styp'Pos (subscr)) - Integer (Styp'Pos (Styp'First));
661
662 -- This is not quite right for bizarre cases where the size of the
663 -- enumeration type is > Integer'Size bits due to rep clause ???
664
665 else
666 pragma Assert (Is_Enumeration_Type (Styp));
667
668 Newsub :=
669 Make_Op_Subtract (Loc,
670 Left_Opnd => Convert_To (Standard_Integer,
671 Make_Attribute_Reference (Loc,
672 Prefix => New_Occurrence_Of (Styp, Loc),
673 Attribute_Name => Name_Pos,
674 Expressions => New_List (Newsub))),
675
676 Right_Opnd =>
677 Convert_To (Standard_Integer,
678 Make_Attribute_Reference (Loc,
679 Prefix => New_Occurrence_Of (Styp, Loc),
680 Attribute_Name => Name_Pos,
681 Expressions => New_List (
682 Make_Attribute_Reference (Loc,
683 Prefix => New_Occurrence_Of (Styp, Loc),
684 Attribute_Name => Name_First)))));
685 end if;
686
687 Set_Paren_Count (Newsub, 1);
688
689 -- For the first subscript, we just copy that subscript value
690
691 if No (Subscr) then
692 Subscr := Newsub;
693
694 -- Otherwise, we must multiply what we already have by the current
695 -- stride and then add in the new value to the evolving subscript.
696
697 else
698 Subscr :=
699 Make_Op_Add (Loc,
700 Left_Opnd =>
701 Make_Op_Multiply (Loc,
702 Left_Opnd => Subscr,
703 Right_Opnd =>
704 Make_Attribute_Reference (Loc,
705 Attribute_Name => Name_Range_Length,
706 Prefix => New_Occurrence_Of (Styp, Loc))),
707 Right_Opnd => Newsub);
708 end if;
709
710 -- Move to next subscript
711
712 Next_Index (Indx);
713 Next (Oldsub);
714 end loop;
715 end Compute_Linear_Subscript;
716
717 -------------------------
718 -- Convert_To_PAT_Type --
719 -------------------------
720
721 -- The PAT is always obtained from the actual subtype
722
723 procedure Convert_To_PAT_Type (Aexp : Node_Id) is
724 Act_ST : Entity_Id;
725
726 begin
727 Convert_To_Actual_Subtype (Aexp);
728 Act_ST := Underlying_Type (Etype (Aexp));
729 Create_Packed_Array_Type (Act_ST);
730
731 -- Just replace the etype with the packed array type. This works because
732 -- the expression will not be further analyzed, and Gigi considers the
733 -- two types equivalent in any case.
734
735 -- This is not strictly the case ??? If the reference is an actual in
736 -- call, the expansion of the prefix is delayed, and must be reanalyzed,
737 -- see Reset_Packed_Prefix. On the other hand, if the prefix is a simple
738 -- array reference, reanalysis can produce spurious type errors when the
739 -- PAT type is replaced again with the original type of the array. Same
740 -- for the case of a dereference. Ditto for function calls: expansion
741 -- may introduce additional actuals which will trigger errors if call is
742 -- reanalyzed. The following is correct and minimal, but the handling of
743 -- more complex packed expressions in actuals is confused. Probably the
744 -- problem only remains for actuals in calls.
745
746 Set_Etype (Aexp, Packed_Array_Type (Act_ST));
747
748 if Is_Entity_Name (Aexp)
749 or else
750 (Nkind (Aexp) = N_Indexed_Component
751 and then Is_Entity_Name (Prefix (Aexp)))
752 or else Nkind_In (Aexp, N_Explicit_Dereference, N_Function_Call)
753 then
754 Set_Analyzed (Aexp);
755 end if;
756 end Convert_To_PAT_Type;
757
758 ------------------------------
759 -- Create_Packed_Array_Type --
760 ------------------------------
761
762 procedure Create_Packed_Array_Type (Typ : Entity_Id) is
763 Loc : constant Source_Ptr := Sloc (Typ);
764 Ctyp : constant Entity_Id := Component_Type (Typ);
765 Csize : constant Uint := Component_Size (Typ);
766
767 Ancest : Entity_Id;
768 PB_Type : Entity_Id;
769 PASize : Uint;
770 Decl : Node_Id;
771 PAT : Entity_Id;
772 Len_Dim : Node_Id;
773 Len_Expr : Node_Id;
774 Len_Bits : Uint;
775 Bits_U1 : Node_Id;
776 PAT_High : Node_Id;
777 Btyp : Entity_Id;
778 Lit : Node_Id;
779
780 procedure Install_PAT;
781 -- This procedure is called with Decl set to the declaration for the
782 -- packed array type. It creates the type and installs it as required.
783
784 procedure Set_PB_Type;
785 -- Sets PB_Type to Packed_Bytes{1,2,4} as required by the alignment
786 -- requirements (see documentation in the spec of this package).
787
788 -----------------
789 -- Install_PAT --
790 -----------------
791
792 procedure Install_PAT is
793 Pushed_Scope : Boolean := False;
794
795 begin
796 -- We do not want to put the declaration we have created in the tree
797 -- since it is often hard, and sometimes impossible to find a proper
798 -- place for it (the impossible case arises for a packed array type
799 -- with bounds depending on the discriminant, a declaration cannot
800 -- be put inside the record, and the reference to the discriminant
801 -- cannot be outside the record).
802
803 -- The solution is to analyze the declaration while temporarily
804 -- attached to the tree at an appropriate point, and then we install
805 -- the resulting type as an Itype in the packed array type field of
806 -- the original type, so that no explicit declaration is required.
807
808 -- Note: the packed type is created in the scope of its parent
809 -- type. There are at least some cases where the current scope
810 -- is deeper, and so when this is the case, we temporarily reset
811 -- the scope for the definition. This is clearly safe, since the
812 -- first use of the packed array type will be the implicit
813 -- reference from the corresponding unpacked type when it is
814 -- elaborated.
815
816 if Is_Itype (Typ) then
817 Set_Parent (Decl, Associated_Node_For_Itype (Typ));
818 else
819 Set_Parent (Decl, Declaration_Node (Typ));
820 end if;
821
822 if Scope (Typ) /= Current_Scope then
823 Push_Scope (Scope (Typ));
824 Pushed_Scope := True;
825 end if;
826
827 Set_Is_Itype (PAT, True);
828 Set_Packed_Array_Type (Typ, PAT);
829 Analyze (Decl, Suppress => All_Checks);
830
831 if Pushed_Scope then
832 Pop_Scope;
833 end if;
834
835 -- Set Esize and RM_Size to the actual size of the packed object
836 -- Do not reset RM_Size if already set, as happens in the case of
837 -- a modular type.
838
839 if Unknown_Esize (PAT) then
840 Set_Esize (PAT, PASize);
841 end if;
842
843 if Unknown_RM_Size (PAT) then
844 Set_RM_Size (PAT, PASize);
845 end if;
846
847 Adjust_Esize_Alignment (PAT);
848
849 -- Set remaining fields of packed array type
850
851 Init_Alignment (PAT);
852 Set_Parent (PAT, Empty);
853 Set_Associated_Node_For_Itype (PAT, Typ);
854 Set_Is_Packed_Array_Type (PAT, True);
855 Set_Original_Array_Type (PAT, Typ);
856
857 -- We definitely do not want to delay freezing for packed array
858 -- types. This is of particular importance for the itypes that
859 -- are generated for record components depending on discriminants
860 -- where there is no place to put the freeze node.
861
862 Set_Has_Delayed_Freeze (PAT, False);
863 Set_Has_Delayed_Freeze (Etype (PAT), False);
864
865 -- If we did allocate a freeze node, then clear out the reference
866 -- since it is obsolete (should we delete the freeze node???)
867
868 Set_Freeze_Node (PAT, Empty);
869 Set_Freeze_Node (Etype (PAT), Empty);
870 end Install_PAT;
871
872 -----------------
873 -- Set_PB_Type --
874 -----------------
875
876 procedure Set_PB_Type is
877 begin
878 -- If the user has specified an explicit alignment for the
879 -- type or component, take it into account.
880
881 if Csize <= 2 or else Csize = 4 or else Csize mod 2 /= 0
882 or else Alignment (Typ) = 1
883 or else Component_Alignment (Typ) = Calign_Storage_Unit
884 then
885 PB_Type := RTE (RE_Packed_Bytes1);
886
887 elsif Csize mod 4 /= 0
888 or else Alignment (Typ) = 2
889 then
890 PB_Type := RTE (RE_Packed_Bytes2);
891
892 else
893 PB_Type := RTE (RE_Packed_Bytes4);
894 end if;
895 end Set_PB_Type;
896
897 -- Start of processing for Create_Packed_Array_Type
898
899 begin
900 -- If we already have a packed array type, nothing to do
901
902 if Present (Packed_Array_Type (Typ)) then
903 return;
904 end if;
905
906 -- If our immediate ancestor subtype is constrained, and it already
907 -- has a packed array type, then just share the same type, since the
908 -- bounds must be the same. If the ancestor is not an array type but
909 -- a private type, as can happen with multiple instantiations, create
910 -- a new packed type, to avoid privacy issues.
911
912 if Ekind (Typ) = E_Array_Subtype then
913 Ancest := Ancestor_Subtype (Typ);
914
915 if Present (Ancest)
916 and then Is_Array_Type (Ancest)
917 and then Is_Constrained (Ancest)
918 and then Present (Packed_Array_Type (Ancest))
919 then
920 Set_Packed_Array_Type (Typ, Packed_Array_Type (Ancest));
921 return;
922 end if;
923 end if;
924
925 -- We preset the result type size from the size of the original array
926 -- type, since this size clearly belongs to the packed array type. The
927 -- size of the conceptual unpacked type is always set to unknown.
928
929 PASize := RM_Size (Typ);
930
931 -- Case of an array where at least one index is of an enumeration
932 -- type with a non-standard representation, but the component size
933 -- is not appropriate for bit packing. This is the case where we
934 -- have Is_Packed set (we would never be in this unit otherwise),
935 -- but Is_Bit_Packed_Array is false.
936
937 -- Note that if the component size is appropriate for bit packing,
938 -- then the circuit for the computation of the subscript properly
939 -- deals with the non-standard enumeration type case by taking the
940 -- Pos anyway.
941
942 if not Is_Bit_Packed_Array (Typ) then
943
944 -- Here we build a declaration:
945
946 -- type tttP is array (index1, index2, ...) of component_type
947
948 -- where index1, index2, are the index types. These are the same
949 -- as the index types of the original array, except for the non-
950 -- standard representation enumeration type case, where we have
951 -- two subcases.
952
953 -- For the unconstrained array case, we use
954
955 -- Natural range <>
956
957 -- For the constrained case, we use
958
959 -- Natural range Enum_Type'Pos (Enum_Type'First) ..
960 -- Enum_Type'Pos (Enum_Type'Last);
961
962 PAT :=
963 Make_Defining_Identifier (Loc,
964 Chars => New_External_Name (Chars (Typ), 'P'));
965
966 Set_Packed_Array_Type (Typ, PAT);
967
968 declare
969 Indexes : constant List_Id := New_List;
970 Indx : Node_Id;
971 Indx_Typ : Entity_Id;
972 Enum_Case : Boolean;
973 Typedef : Node_Id;
974
975 begin
976 Indx := First_Index (Typ);
977
978 while Present (Indx) loop
979 Indx_Typ := Etype (Indx);
980
981 Enum_Case := Is_Enumeration_Type (Indx_Typ)
982 and then Has_Non_Standard_Rep (Indx_Typ);
983
984 -- Unconstrained case
985
986 if not Is_Constrained (Typ) then
987 if Enum_Case then
988 Indx_Typ := Standard_Natural;
989 end if;
990
991 Append_To (Indexes, New_Occurrence_Of (Indx_Typ, Loc));
992
993 -- Constrained case
994
995 else
996 if not Enum_Case then
997 Append_To (Indexes, New_Occurrence_Of (Indx_Typ, Loc));
998
999 else
1000 Append_To (Indexes,
1001 Make_Subtype_Indication (Loc,
1002 Subtype_Mark =>
1003 New_Occurrence_Of (Standard_Natural, Loc),
1004 Constraint =>
1005 Make_Range_Constraint (Loc,
1006 Range_Expression =>
1007 Make_Range (Loc,
1008 Low_Bound =>
1009 Make_Attribute_Reference (Loc,
1010 Prefix =>
1011 New_Occurrence_Of (Indx_Typ, Loc),
1012 Attribute_Name => Name_Pos,
1013 Expressions => New_List (
1014 Make_Attribute_Reference (Loc,
1015 Prefix =>
1016 New_Occurrence_Of (Indx_Typ, Loc),
1017 Attribute_Name => Name_First))),
1018
1019 High_Bound =>
1020 Make_Attribute_Reference (Loc,
1021 Prefix =>
1022 New_Occurrence_Of (Indx_Typ, Loc),
1023 Attribute_Name => Name_Pos,
1024 Expressions => New_List (
1025 Make_Attribute_Reference (Loc,
1026 Prefix =>
1027 New_Occurrence_Of (Indx_Typ, Loc),
1028 Attribute_Name => Name_Last)))))));
1029
1030 end if;
1031 end if;
1032
1033 Next_Index (Indx);
1034 end loop;
1035
1036 if not Is_Constrained (Typ) then
1037 Typedef :=
1038 Make_Unconstrained_Array_Definition (Loc,
1039 Subtype_Marks => Indexes,
1040 Component_Definition =>
1041 Make_Component_Definition (Loc,
1042 Aliased_Present => False,
1043 Subtype_Indication =>
1044 New_Occurrence_Of (Ctyp, Loc)));
1045
1046 else
1047 Typedef :=
1048 Make_Constrained_Array_Definition (Loc,
1049 Discrete_Subtype_Definitions => Indexes,
1050 Component_Definition =>
1051 Make_Component_Definition (Loc,
1052 Aliased_Present => False,
1053 Subtype_Indication =>
1054 New_Occurrence_Of (Ctyp, Loc)));
1055 end if;
1056
1057 Decl :=
1058 Make_Full_Type_Declaration (Loc,
1059 Defining_Identifier => PAT,
1060 Type_Definition => Typedef);
1061 end;
1062
1063 -- Set type as packed array type and install it
1064
1065 Set_Is_Packed_Array_Type (PAT);
1066 Install_PAT;
1067 return;
1068
1069 -- Case of bit-packing required for unconstrained array. We create
1070 -- a subtype that is equivalent to use Packed_Bytes{1,2,4} as needed.
1071
1072 elsif not Is_Constrained (Typ) then
1073 PAT :=
1074 Make_Defining_Identifier (Loc,
1075 Chars => Make_Packed_Array_Type_Name (Typ, Csize));
1076
1077 Set_Packed_Array_Type (Typ, PAT);
1078 Set_PB_Type;
1079
1080 Decl :=
1081 Make_Subtype_Declaration (Loc,
1082 Defining_Identifier => PAT,
1083 Subtype_Indication => New_Occurrence_Of (PB_Type, Loc));
1084 Install_PAT;
1085 return;
1086
1087 -- Remaining code is for the case of bit-packing for constrained array
1088
1089 -- The name of the packed array subtype is
1090
1091 -- ttt___Xsss
1092
1093 -- where sss is the component size in bits and ttt is the name of
1094 -- the parent packed type.
1095
1096 else
1097 PAT :=
1098 Make_Defining_Identifier (Loc,
1099 Chars => Make_Packed_Array_Type_Name (Typ, Csize));
1100
1101 Set_Packed_Array_Type (Typ, PAT);
1102
1103 -- Build an expression for the length of the array in bits.
1104 -- This is the product of the length of each of the dimensions
1105
1106 declare
1107 J : Nat := 1;
1108
1109 begin
1110 Len_Expr := Empty; -- suppress junk warning
1111
1112 loop
1113 Len_Dim :=
1114 Make_Attribute_Reference (Loc,
1115 Attribute_Name => Name_Length,
1116 Prefix => New_Occurrence_Of (Typ, Loc),
1117 Expressions => New_List (
1118 Make_Integer_Literal (Loc, J)));
1119
1120 if J = 1 then
1121 Len_Expr := Len_Dim;
1122
1123 else
1124 Len_Expr :=
1125 Make_Op_Multiply (Loc,
1126 Left_Opnd => Len_Expr,
1127 Right_Opnd => Len_Dim);
1128 end if;
1129
1130 J := J + 1;
1131 exit when J > Number_Dimensions (Typ);
1132 end loop;
1133 end;
1134
1135 -- Temporarily attach the length expression to the tree and analyze
1136 -- and resolve it, so that we can test its value. We assume that the
1137 -- total length fits in type Integer. This expression may involve
1138 -- discriminants, so we treat it as a default/per-object expression.
1139
1140 Set_Parent (Len_Expr, Typ);
1141 Preanalyze_Spec_Expression (Len_Expr, Standard_Long_Long_Integer);
1142
1143 -- Use a modular type if possible. We can do this if we have
1144 -- static bounds, and the length is small enough, and the length
1145 -- is not zero. We exclude the zero length case because the size
1146 -- of things is always at least one, and the zero length object
1147 -- would have an anomalous size.
1148
1149 if Compile_Time_Known_Value (Len_Expr) then
1150 Len_Bits := Expr_Value (Len_Expr) * Csize;
1151
1152 -- Check for size known to be too large
1153
1154 if Len_Bits >
1155 Uint_2 ** (Standard_Integer_Size - 1) * System_Storage_Unit
1156 then
1157 if System_Storage_Unit = 8 then
1158 Error_Msg_N
1159 ("packed array size cannot exceed " &
1160 "Integer''Last bytes", Typ);
1161 else
1162 Error_Msg_N
1163 ("packed array size cannot exceed " &
1164 "Integer''Last storage units", Typ);
1165 end if;
1166
1167 -- Reset length to arbitrary not too high value to continue
1168
1169 Len_Expr := Make_Integer_Literal (Loc, 65535);
1170 Analyze_And_Resolve (Len_Expr, Standard_Long_Long_Integer);
1171 end if;
1172
1173 -- We normally consider small enough to mean no larger than the
1174 -- value of System_Max_Binary_Modulus_Power, checking that in the
1175 -- case of values longer than word size, we have long shifts.
1176
1177 if Len_Bits > 0
1178 and then
1179 (Len_Bits <= System_Word_Size
1180 or else (Len_Bits <= System_Max_Binary_Modulus_Power
1181 and then Support_Long_Shifts_On_Target))
1182 then
1183 -- We can use the modular type, it has the form:
1184
1185 -- subtype tttPn is btyp
1186 -- range 0 .. 2 ** ((Typ'Length (1)
1187 -- * ... * Typ'Length (n)) * Csize) - 1;
1188
1189 -- The bounds are statically known, and btyp is one of the
1190 -- unsigned types, depending on the length.
1191
1192 if Len_Bits <= Standard_Short_Short_Integer_Size then
1193 Btyp := RTE (RE_Short_Short_Unsigned);
1194
1195 elsif Len_Bits <= Standard_Short_Integer_Size then
1196 Btyp := RTE (RE_Short_Unsigned);
1197
1198 elsif Len_Bits <= Standard_Integer_Size then
1199 Btyp := RTE (RE_Unsigned);
1200
1201 elsif Len_Bits <= Standard_Long_Integer_Size then
1202 Btyp := RTE (RE_Long_Unsigned);
1203
1204 else
1205 Btyp := RTE (RE_Long_Long_Unsigned);
1206 end if;
1207
1208 Lit := Make_Integer_Literal (Loc, 2 ** Len_Bits - 1);
1209 Set_Print_In_Hex (Lit);
1210
1211 Decl :=
1212 Make_Subtype_Declaration (Loc,
1213 Defining_Identifier => PAT,
1214 Subtype_Indication =>
1215 Make_Subtype_Indication (Loc,
1216 Subtype_Mark => New_Occurrence_Of (Btyp, Loc),
1217
1218 Constraint =>
1219 Make_Range_Constraint (Loc,
1220 Range_Expression =>
1221 Make_Range (Loc,
1222 Low_Bound =>
1223 Make_Integer_Literal (Loc, 0),
1224 High_Bound => Lit))));
1225
1226 if PASize = Uint_0 then
1227 PASize := Len_Bits;
1228 end if;
1229
1230 Install_PAT;
1231
1232 -- Propagate a given alignment to the modular type. This can
1233 -- cause it to be under-aligned, but that's OK.
1234
1235 if Present (Alignment_Clause (Typ)) then
1236 Set_Alignment (PAT, Alignment (Typ));
1237 end if;
1238
1239 return;
1240 end if;
1241 end if;
1242
1243 -- Could not use a modular type, for all other cases, we build
1244 -- a packed array subtype:
1245
1246 -- subtype tttPn is
1247 -- System.Packed_Bytes{1,2,4} (0 .. (Bits + 7) / 8 - 1);
1248
1249 -- Bits is the length of the array in bits
1250
1251 Set_PB_Type;
1252
1253 Bits_U1 :=
1254 Make_Op_Add (Loc,
1255 Left_Opnd =>
1256 Make_Op_Multiply (Loc,
1257 Left_Opnd =>
1258 Make_Integer_Literal (Loc, Csize),
1259 Right_Opnd => Len_Expr),
1260
1261 Right_Opnd =>
1262 Make_Integer_Literal (Loc, 7));
1263
1264 Set_Paren_Count (Bits_U1, 1);
1265
1266 PAT_High :=
1267 Make_Op_Subtract (Loc,
1268 Left_Opnd =>
1269 Make_Op_Divide (Loc,
1270 Left_Opnd => Bits_U1,
1271 Right_Opnd => Make_Integer_Literal (Loc, 8)),
1272 Right_Opnd => Make_Integer_Literal (Loc, 1));
1273
1274 Decl :=
1275 Make_Subtype_Declaration (Loc,
1276 Defining_Identifier => PAT,
1277 Subtype_Indication =>
1278 Make_Subtype_Indication (Loc,
1279 Subtype_Mark => New_Occurrence_Of (PB_Type, Loc),
1280 Constraint =>
1281 Make_Index_Or_Discriminant_Constraint (Loc,
1282 Constraints => New_List (
1283 Make_Range (Loc,
1284 Low_Bound =>
1285 Make_Integer_Literal (Loc, 0),
1286 High_Bound =>
1287 Convert_To (Standard_Integer, PAT_High))))));
1288
1289 Install_PAT;
1290
1291 -- Currently the code in this unit requires that packed arrays
1292 -- represented by non-modular arrays of bytes be on a byte
1293 -- boundary for bit sizes handled by System.Pack_nn units.
1294 -- That's because these units assume the array being accessed
1295 -- starts on a byte boundary.
1296
1297 if Get_Id (UI_To_Int (Csize)) /= RE_Null then
1298 Set_Must_Be_On_Byte_Boundary (Typ);
1299 end if;
1300 end if;
1301 end Create_Packed_Array_Type;
1302
1303 -----------------------------------
1304 -- Expand_Bit_Packed_Element_Set --
1305 -----------------------------------
1306
1307 procedure Expand_Bit_Packed_Element_Set (N : Node_Id) is
1308 Loc : constant Source_Ptr := Sloc (N);
1309 Lhs : constant Node_Id := Name (N);
1310
1311 Ass_OK : constant Boolean := Assignment_OK (Lhs);
1312 -- Used to preserve assignment OK status when assignment is rewritten
1313
1314 Rhs : Node_Id := Expression (N);
1315 -- Initially Rhs is the right hand side value, it will be replaced
1316 -- later by an appropriate unchecked conversion for the assignment.
1317
1318 Obj : Node_Id;
1319 Atyp : Entity_Id;
1320 PAT : Entity_Id;
1321 Ctyp : Entity_Id;
1322 Csiz : Int;
1323 Cmask : Uint;
1324
1325 Shift : Node_Id;
1326 -- The expression for the shift value that is required
1327
1328 Shift_Used : Boolean := False;
1329 -- Set True if Shift has been used in the generated code at least
1330 -- once, so that it must be duplicated if used again
1331
1332 New_Lhs : Node_Id;
1333 New_Rhs : Node_Id;
1334
1335 Rhs_Val_Known : Boolean;
1336 Rhs_Val : Uint;
1337 -- If the value of the right hand side as an integer constant is
1338 -- known at compile time, Rhs_Val_Known is set True, and Rhs_Val
1339 -- contains the value. Otherwise Rhs_Val_Known is set False, and
1340 -- the Rhs_Val is undefined.
1341
1342 Require_Byte_Swapping : Boolean := False;
1343 -- True if byte swapping required, for the Reverse_Storage_Order case
1344 -- when the packed array is a free-standing object. (If it is part
1345 -- of a composite type, and therefore potentially not aligned on a byte
1346 -- boundary, the swapping is done by the back-end).
1347
1348 function Get_Shift return Node_Id;
1349 -- Function used to get the value of Shift, making sure that it
1350 -- gets duplicated if the function is called more than once.
1351
1352 ---------------
1353 -- Get_Shift --
1354 ---------------
1355
1356 function Get_Shift return Node_Id is
1357 begin
1358 -- If we used the shift value already, then duplicate it. We
1359 -- set a temporary parent in case actions have to be inserted.
1360
1361 if Shift_Used then
1362 Set_Parent (Shift, N);
1363 return Duplicate_Subexpr_No_Checks (Shift);
1364
1365 -- If first time, use Shift unchanged, and set flag for first use
1366
1367 else
1368 Shift_Used := True;
1369 return Shift;
1370 end if;
1371 end Get_Shift;
1372
1373 -- Start of processing for Expand_Bit_Packed_Element_Set
1374
1375 begin
1376 pragma Assert (Is_Bit_Packed_Array (Etype (Prefix (Lhs))));
1377
1378 Obj := Relocate_Node (Prefix (Lhs));
1379 Convert_To_Actual_Subtype (Obj);
1380 Atyp := Etype (Obj);
1381 PAT := Packed_Array_Type (Atyp);
1382 Ctyp := Component_Type (Atyp);
1383 Csiz := UI_To_Int (Component_Size (Atyp));
1384
1385 -- We remove side effects, in case the rhs modifies the lhs, because we
1386 -- are about to transform the rhs into an expression that first READS
1387 -- the lhs, so we can do the necessary shifting and masking. Example:
1388 -- "X(2) := F(...);" where F modifies X(3). Otherwise, the side effect
1389 -- will be lost.
1390
1391 Remove_Side_Effects (Rhs);
1392
1393 -- We convert the right hand side to the proper subtype to ensure
1394 -- that an appropriate range check is made (since the normal range
1395 -- check from assignment will be lost in the transformations). This
1396 -- conversion is analyzed immediately so that subsequent processing
1397 -- can work with an analyzed Rhs (and e.g. look at its Etype)
1398
1399 -- If the right-hand side is a string literal, create a temporary for
1400 -- it, constant-folding is not ready to wrap the bit representation
1401 -- of a string literal.
1402
1403 if Nkind (Rhs) = N_String_Literal then
1404 declare
1405 Decl : Node_Id;
1406 begin
1407 Decl :=
1408 Make_Object_Declaration (Loc,
1409 Defining_Identifier => Make_Temporary (Loc, 'T', Rhs),
1410 Object_Definition => New_Occurrence_Of (Ctyp, Loc),
1411 Expression => New_Copy_Tree (Rhs));
1412
1413 Insert_Actions (N, New_List (Decl));
1414 Rhs := New_Occurrence_Of (Defining_Identifier (Decl), Loc);
1415 end;
1416 end if;
1417
1418 Rhs := Convert_To (Ctyp, Rhs);
1419 Set_Parent (Rhs, N);
1420
1421 -- If we are building the initialization procedure for a packed array,
1422 -- and Initialize_Scalars is enabled, each component assignment is an
1423 -- out-of-range value by design. Compile this value without checks,
1424 -- because a call to the array init_proc must not raise an exception.
1425
1426 if Within_Init_Proc
1427 and then Initialize_Scalars
1428 then
1429 Analyze_And_Resolve (Rhs, Ctyp, Suppress => All_Checks);
1430 else
1431 Analyze_And_Resolve (Rhs, Ctyp);
1432 end if;
1433
1434 -- For the AAMP target, indexing of certain packed array is passed
1435 -- through to the back end without expansion, because the expansion
1436 -- results in very inefficient code on that target. This allows the
1437 -- GNAAMP back end to generate specialized macros that support more
1438 -- efficient indexing of packed arrays with components having sizes
1439 -- that are small powers of two.
1440
1441 if AAMP_On_Target
1442 and then (Csiz = 1 or else Csiz = 2 or else Csiz = 4)
1443 then
1444 return;
1445 end if;
1446
1447 -- Case of component size 1,2,4 or any component size for the modular
1448 -- case. These are the cases for which we can inline the code.
1449
1450 if Csiz = 1 or else Csiz = 2 or else Csiz = 4
1451 or else (Present (PAT) and then Is_Modular_Integer_Type (PAT))
1452 then
1453 Setup_Inline_Packed_Array_Reference (Lhs, Atyp, Obj, Cmask, Shift);
1454
1455 -- The statement to be generated is:
1456
1457 -- Obj := atyp!((Obj and Mask1) or (shift_left (rhs, Shift)))
1458
1459 -- or in the case of a freestanding Reverse_Storage_Order object,
1460
1461 -- Obj := Swap (atyp!((Swap (Obj) and Mask1)
1462 -- or (shift_left (rhs, Shift))))
1463
1464 -- where Mask1 is obtained by shifting Cmask left Shift bits
1465 -- and then complementing the result.
1466
1467 -- the "and Mask1" is omitted if rhs is constant and all 1 bits
1468
1469 -- the "or ..." is omitted if rhs is constant and all 0 bits
1470
1471 -- rhs is converted to the appropriate type
1472
1473 -- The result is converted back to the array type, since
1474 -- otherwise we lose knowledge of the packed nature.
1475
1476 -- Determine if right side is all 0 bits or all 1 bits
1477
1478 if Compile_Time_Known_Value (Rhs) then
1479 Rhs_Val := Expr_Rep_Value (Rhs);
1480 Rhs_Val_Known := True;
1481
1482 -- The following test catches the case of an unchecked conversion of
1483 -- an integer literal. This results from optimizing aggregates of
1484 -- packed types.
1485
1486 elsif Nkind (Rhs) = N_Unchecked_Type_Conversion
1487 and then Compile_Time_Known_Value (Expression (Rhs))
1488 then
1489 Rhs_Val := Expr_Rep_Value (Expression (Rhs));
1490 Rhs_Val_Known := True;
1491
1492 else
1493 Rhs_Val := No_Uint;
1494 Rhs_Val_Known := False;
1495 end if;
1496
1497 -- Some special checks for the case where the right hand value is
1498 -- known at compile time. Basically we have to take care of the
1499 -- implicit conversion to the subtype of the component object.
1500
1501 if Rhs_Val_Known then
1502
1503 -- If we have a biased component type then we must manually do the
1504 -- biasing, since we are taking responsibility in this case for
1505 -- constructing the exact bit pattern to be used.
1506
1507 if Has_Biased_Representation (Ctyp) then
1508 Rhs_Val := Rhs_Val - Expr_Rep_Value (Type_Low_Bound (Ctyp));
1509 end if;
1510
1511 -- For a negative value, we manually convert the two's complement
1512 -- value to a corresponding unsigned value, so that the proper
1513 -- field width is maintained. If we did not do this, we would
1514 -- get too many leading sign bits later on.
1515
1516 if Rhs_Val < 0 then
1517 Rhs_Val := 2 ** UI_From_Int (Csiz) + Rhs_Val;
1518 end if;
1519 end if;
1520
1521 -- Now create copies removing side effects. Note that in some complex
1522 -- cases, this may cause the fact that we have already set a packed
1523 -- array type on Obj to get lost. So we save the type of Obj, and
1524 -- make sure it is reset properly.
1525
1526 declare
1527 T : constant Entity_Id := Etype (Obj);
1528 begin
1529 New_Lhs := Duplicate_Subexpr (Obj, True);
1530 New_Rhs := Duplicate_Subexpr_No_Checks (Obj);
1531 Set_Etype (Obj, T);
1532 Set_Etype (New_Lhs, T);
1533 Set_Etype (New_Rhs, T);
1534
1535 if Reverse_Storage_Order (Base_Type (Atyp))
1536 and then Esize (T) > 8
1537 and then not In_Reverse_Storage_Order_Object (Obj)
1538 then
1539 Require_Byte_Swapping := True;
1540 New_Rhs := Byte_Swap (New_Rhs);
1541 end if;
1542 end;
1543
1544 -- First we deal with the "and"
1545
1546 if not Rhs_Val_Known or else Rhs_Val /= Cmask then
1547 declare
1548 Mask1 : Node_Id;
1549 Lit : Node_Id;
1550
1551 begin
1552 if Compile_Time_Known_Value (Shift) then
1553 Mask1 :=
1554 Make_Integer_Literal (Loc,
1555 Modulus (Etype (Obj)) - 1 -
1556 (Cmask * (2 ** Expr_Value (Get_Shift))));
1557 Set_Print_In_Hex (Mask1);
1558
1559 else
1560 Lit := Make_Integer_Literal (Loc, Cmask);
1561 Set_Print_In_Hex (Lit);
1562 Mask1 :=
1563 Make_Op_Not (Loc,
1564 Right_Opnd => Make_Shift_Left (Lit, Get_Shift));
1565 end if;
1566
1567 New_Rhs :=
1568 Make_Op_And (Loc,
1569 Left_Opnd => New_Rhs,
1570 Right_Opnd => Mask1);
1571 end;
1572 end if;
1573
1574 -- Then deal with the "or"
1575
1576 if not Rhs_Val_Known or else Rhs_Val /= 0 then
1577 declare
1578 Or_Rhs : Node_Id;
1579
1580 procedure Fixup_Rhs;
1581 -- Adjust Rhs by bias if biased representation for components
1582 -- or remove extraneous high order sign bits if signed.
1583
1584 procedure Fixup_Rhs is
1585 Etyp : constant Entity_Id := Etype (Rhs);
1586
1587 begin
1588 -- For biased case, do the required biasing by simply
1589 -- converting to the biased subtype (the conversion
1590 -- will generate the required bias).
1591
1592 if Has_Biased_Representation (Ctyp) then
1593 Rhs := Convert_To (Ctyp, Rhs);
1594
1595 -- For a signed integer type that is not biased, generate
1596 -- a conversion to unsigned to strip high order sign bits.
1597
1598 elsif Is_Signed_Integer_Type (Ctyp) then
1599 Rhs := Unchecked_Convert_To (RTE (Bits_Id (Csiz)), Rhs);
1600 end if;
1601
1602 -- Set Etype, since it can be referenced before the node is
1603 -- completely analyzed.
1604
1605 Set_Etype (Rhs, Etyp);
1606
1607 -- We now need to do an unchecked conversion of the
1608 -- result to the target type, but it is important that
1609 -- this conversion be a right justified conversion and
1610 -- not a left justified conversion.
1611
1612 Rhs := RJ_Unchecked_Convert_To (Etype (Obj), Rhs);
1613
1614 end Fixup_Rhs;
1615
1616 begin
1617 if Rhs_Val_Known
1618 and then Compile_Time_Known_Value (Get_Shift)
1619 then
1620 Or_Rhs :=
1621 Make_Integer_Literal (Loc,
1622 Rhs_Val * (2 ** Expr_Value (Get_Shift)));
1623 Set_Print_In_Hex (Or_Rhs);
1624
1625 else
1626 -- We have to convert the right hand side to Etype (Obj).
1627 -- A special case arises if what we have now is a Val
1628 -- attribute reference whose expression type is Etype (Obj).
1629 -- This happens for assignments of fields from the same
1630 -- array. In this case we get the required right hand side
1631 -- by simply removing the inner attribute reference.
1632
1633 if Nkind (Rhs) = N_Attribute_Reference
1634 and then Attribute_Name (Rhs) = Name_Val
1635 and then Etype (First (Expressions (Rhs))) = Etype (Obj)
1636 then
1637 Rhs := Relocate_Node (First (Expressions (Rhs)));
1638 Fixup_Rhs;
1639
1640 -- If the value of the right hand side is a known integer
1641 -- value, then just replace it by an untyped constant,
1642 -- which will be properly retyped when we analyze and
1643 -- resolve the expression.
1644
1645 elsif Rhs_Val_Known then
1646
1647 -- Note that Rhs_Val has already been normalized to
1648 -- be an unsigned value with the proper number of bits.
1649
1650 Rhs := Make_Integer_Literal (Loc, Rhs_Val);
1651
1652 -- Otherwise we need an unchecked conversion
1653
1654 else
1655 Fixup_Rhs;
1656 end if;
1657
1658 Or_Rhs := Make_Shift_Left (Rhs, Get_Shift);
1659 end if;
1660
1661 if Nkind (New_Rhs) = N_Op_And then
1662 Set_Paren_Count (New_Rhs, 1);
1663 end if;
1664
1665 New_Rhs :=
1666 Make_Op_Or (Loc,
1667 Left_Opnd => New_Rhs,
1668 Right_Opnd => Or_Rhs);
1669 end;
1670 end if;
1671
1672 if Require_Byte_Swapping then
1673 Set_Etype (New_Rhs, Etype (Obj));
1674 New_Rhs := Byte_Swap (New_Rhs);
1675 end if;
1676
1677 -- Now do the rewrite
1678
1679 Rewrite (N,
1680 Make_Assignment_Statement (Loc,
1681 Name => New_Lhs,
1682 Expression =>
1683 Unchecked_Convert_To (Etype (New_Lhs), New_Rhs)));
1684 Set_Assignment_OK (Name (N), Ass_OK);
1685
1686 -- All other component sizes for non-modular case
1687
1688 else
1689 -- We generate
1690
1691 -- Set_nn (Arr'address, Subscr, Bits_nn!(Rhs))
1692
1693 -- where Subscr is the computed linear subscript
1694
1695 declare
1696 Bits_nn : constant Entity_Id := RTE (Bits_Id (Csiz));
1697 Set_nn : Entity_Id;
1698 Subscr : Node_Id;
1699 Atyp : Entity_Id;
1700
1701 begin
1702 if No (Bits_nn) then
1703
1704 -- Error, most likely High_Integrity_Mode restriction
1705
1706 return;
1707 end if;
1708
1709 -- Acquire proper Set entity. We use the aligned or unaligned
1710 -- case as appropriate.
1711
1712 if Known_Aligned_Enough (Obj, Csiz) then
1713 Set_nn := RTE (Set_Id (Csiz));
1714 else
1715 Set_nn := RTE (SetU_Id (Csiz));
1716 end if;
1717
1718 -- Now generate the set reference
1719
1720 Obj := Relocate_Node (Prefix (Lhs));
1721 Convert_To_Actual_Subtype (Obj);
1722 Atyp := Etype (Obj);
1723 Compute_Linear_Subscript (Atyp, Lhs, Subscr);
1724
1725 -- Below we must make the assumption that Obj is
1726 -- at least byte aligned, since otherwise its address
1727 -- cannot be taken. The assumption holds since the
1728 -- only arrays that can be misaligned are small packed
1729 -- arrays which are implemented as a modular type, and
1730 -- that is not the case here.
1731
1732 Rewrite (N,
1733 Make_Procedure_Call_Statement (Loc,
1734 Name => New_Occurrence_Of (Set_nn, Loc),
1735 Parameter_Associations => New_List (
1736 Make_Attribute_Reference (Loc,
1737 Prefix => Obj,
1738 Attribute_Name => Name_Address),
1739 Subscr,
1740 Unchecked_Convert_To (Bits_nn,
1741 Convert_To (Ctyp, Rhs)))));
1742
1743 end;
1744 end if;
1745
1746 Analyze (N, Suppress => All_Checks);
1747 end Expand_Bit_Packed_Element_Set;
1748
1749 -------------------------------------
1750 -- Expand_Packed_Address_Reference --
1751 -------------------------------------
1752
1753 procedure Expand_Packed_Address_Reference (N : Node_Id) is
1754 Loc : constant Source_Ptr := Sloc (N);
1755 Base : Node_Id;
1756 Offset : Node_Id;
1757
1758 begin
1759 -- We build an expression that has the form
1760
1761 -- outer_object'Address
1762 -- + (linear-subscript * component_size for each array reference
1763 -- + field'Bit_Position for each record field
1764 -- + ...
1765 -- + ...) / Storage_Unit;
1766
1767 Get_Base_And_Bit_Offset (Prefix (N), Base, Offset);
1768
1769 Rewrite (N,
1770 Unchecked_Convert_To (RTE (RE_Address),
1771 Make_Op_Add (Loc,
1772 Left_Opnd =>
1773 Unchecked_Convert_To (RTE (RE_Integer_Address),
1774 Make_Attribute_Reference (Loc,
1775 Prefix => Base,
1776 Attribute_Name => Name_Address)),
1777
1778 Right_Opnd =>
1779 Unchecked_Convert_To (RTE (RE_Integer_Address),
1780 Make_Op_Divide (Loc,
1781 Left_Opnd => Offset,
1782 Right_Opnd =>
1783 Make_Integer_Literal (Loc, System_Storage_Unit))))));
1784
1785 Analyze_And_Resolve (N, RTE (RE_Address));
1786 end Expand_Packed_Address_Reference;
1787
1788 ---------------------------------
1789 -- Expand_Packed_Bit_Reference --
1790 ---------------------------------
1791
1792 procedure Expand_Packed_Bit_Reference (N : Node_Id) is
1793 Loc : constant Source_Ptr := Sloc (N);
1794 Base : Node_Id;
1795 Offset : Node_Id;
1796
1797 begin
1798 -- We build an expression that has the form
1799
1800 -- (linear-subscript * component_size for each array reference
1801 -- + field'Bit_Position for each record field
1802 -- + ...
1803 -- + ...) mod Storage_Unit;
1804
1805 Get_Base_And_Bit_Offset (Prefix (N), Base, Offset);
1806
1807 Rewrite (N,
1808 Unchecked_Convert_To (Universal_Integer,
1809 Make_Op_Mod (Loc,
1810 Left_Opnd => Offset,
1811 Right_Opnd => Make_Integer_Literal (Loc, System_Storage_Unit))));
1812
1813 Analyze_And_Resolve (N, Universal_Integer);
1814 end Expand_Packed_Bit_Reference;
1815
1816 ------------------------------------
1817 -- Expand_Packed_Boolean_Operator --
1818 ------------------------------------
1819
1820 -- This routine expands "a op b" for the packed cases
1821
1822 procedure Expand_Packed_Boolean_Operator (N : Node_Id) is
1823 Loc : constant Source_Ptr := Sloc (N);
1824 Typ : constant Entity_Id := Etype (N);
1825 L : constant Node_Id := Relocate_Node (Left_Opnd (N));
1826 R : constant Node_Id := Relocate_Node (Right_Opnd (N));
1827
1828 Ltyp : Entity_Id;
1829 Rtyp : Entity_Id;
1830 PAT : Entity_Id;
1831
1832 begin
1833 Convert_To_Actual_Subtype (L);
1834 Convert_To_Actual_Subtype (R);
1835
1836 Ensure_Defined (Etype (L), N);
1837 Ensure_Defined (Etype (R), N);
1838
1839 Apply_Length_Check (R, Etype (L));
1840
1841 Ltyp := Etype (L);
1842 Rtyp := Etype (R);
1843
1844 -- Deal with silly case of XOR where the subcomponent has a range
1845 -- True .. True where an exception must be raised.
1846
1847 if Nkind (N) = N_Op_Xor then
1848 Silly_Boolean_Array_Xor_Test (N, Rtyp);
1849 end if;
1850
1851 -- Now that that silliness is taken care of, get packed array type
1852
1853 Convert_To_PAT_Type (L);
1854 Convert_To_PAT_Type (R);
1855
1856 PAT := Etype (L);
1857
1858 -- For the modular case, we expand a op b into
1859
1860 -- rtyp!(pat!(a) op pat!(b))
1861
1862 -- where rtyp is the Etype of the left operand. Note that we do not
1863 -- convert to the base type, since this would be unconstrained, and
1864 -- hence not have a corresponding packed array type set.
1865
1866 -- Note that both operands must be modular for this code to be used
1867
1868 if Is_Modular_Integer_Type (PAT)
1869 and then
1870 Is_Modular_Integer_Type (Etype (R))
1871 then
1872 declare
1873 P : Node_Id;
1874
1875 begin
1876 if Nkind (N) = N_Op_And then
1877 P := Make_Op_And (Loc, L, R);
1878
1879 elsif Nkind (N) = N_Op_Or then
1880 P := Make_Op_Or (Loc, L, R);
1881
1882 else -- Nkind (N) = N_Op_Xor
1883 P := Make_Op_Xor (Loc, L, R);
1884 end if;
1885
1886 Rewrite (N, Unchecked_Convert_To (Ltyp, P));
1887 end;
1888
1889 -- For the array case, we insert the actions
1890
1891 -- Result : Ltype;
1892
1893 -- System.Bit_Ops.Bit_And/Or/Xor
1894 -- (Left'Address,
1895 -- Ltype'Length * Ltype'Component_Size;
1896 -- Right'Address,
1897 -- Rtype'Length * Rtype'Component_Size
1898 -- Result'Address);
1899
1900 -- where Left and Right are the Packed_Bytes{1,2,4} operands and
1901 -- the second argument and fourth arguments are the lengths of the
1902 -- operands in bits. Then we replace the expression by a reference
1903 -- to Result.
1904
1905 -- Note that if we are mixing a modular and array operand, everything
1906 -- works fine, since we ensure that the modular representation has the
1907 -- same physical layout as the array representation (that's what the
1908 -- left justified modular stuff in the big-endian case is about).
1909
1910 else
1911 declare
1912 Result_Ent : constant Entity_Id := Make_Temporary (Loc, 'T');
1913 E_Id : RE_Id;
1914
1915 begin
1916 if Nkind (N) = N_Op_And then
1917 E_Id := RE_Bit_And;
1918
1919 elsif Nkind (N) = N_Op_Or then
1920 E_Id := RE_Bit_Or;
1921
1922 else -- Nkind (N) = N_Op_Xor
1923 E_Id := RE_Bit_Xor;
1924 end if;
1925
1926 Insert_Actions (N, New_List (
1927
1928 Make_Object_Declaration (Loc,
1929 Defining_Identifier => Result_Ent,
1930 Object_Definition => New_Occurrence_Of (Ltyp, Loc)),
1931
1932 Make_Procedure_Call_Statement (Loc,
1933 Name => New_Occurrence_Of (RTE (E_Id), Loc),
1934 Parameter_Associations => New_List (
1935
1936 Make_Byte_Aligned_Attribute_Reference (Loc,
1937 Prefix => L,
1938 Attribute_Name => Name_Address),
1939
1940 Make_Op_Multiply (Loc,
1941 Left_Opnd =>
1942 Make_Attribute_Reference (Loc,
1943 Prefix =>
1944 New_Occurrence_Of
1945 (Etype (First_Index (Ltyp)), Loc),
1946 Attribute_Name => Name_Range_Length),
1947
1948 Right_Opnd =>
1949 Make_Integer_Literal (Loc, Component_Size (Ltyp))),
1950
1951 Make_Byte_Aligned_Attribute_Reference (Loc,
1952 Prefix => R,
1953 Attribute_Name => Name_Address),
1954
1955 Make_Op_Multiply (Loc,
1956 Left_Opnd =>
1957 Make_Attribute_Reference (Loc,
1958 Prefix =>
1959 New_Occurrence_Of
1960 (Etype (First_Index (Rtyp)), Loc),
1961 Attribute_Name => Name_Range_Length),
1962
1963 Right_Opnd =>
1964 Make_Integer_Literal (Loc, Component_Size (Rtyp))),
1965
1966 Make_Byte_Aligned_Attribute_Reference (Loc,
1967 Prefix => New_Occurrence_Of (Result_Ent, Loc),
1968 Attribute_Name => Name_Address)))));
1969
1970 Rewrite (N,
1971 New_Occurrence_Of (Result_Ent, Loc));
1972 end;
1973 end if;
1974
1975 Analyze_And_Resolve (N, Typ, Suppress => All_Checks);
1976 end Expand_Packed_Boolean_Operator;
1977
1978 -------------------------------------
1979 -- Expand_Packed_Element_Reference --
1980 -------------------------------------
1981
1982 procedure Expand_Packed_Element_Reference (N : Node_Id) is
1983 Loc : constant Source_Ptr := Sloc (N);
1984 Obj : Node_Id;
1985 Atyp : Entity_Id;
1986 PAT : Entity_Id;
1987 Ctyp : Entity_Id;
1988 Csiz : Int;
1989 Shift : Node_Id;
1990 Cmask : Uint;
1991 Lit : Node_Id;
1992 Arg : Node_Id;
1993
1994 begin
1995 -- If not bit packed, we have the enumeration case, which is easily
1996 -- dealt with (just adjust the subscripts of the indexed component)
1997
1998 -- Note: this leaves the result as an indexed component, which is
1999 -- still a variable, so can be used in the assignment case, as is
2000 -- required in the enumeration case.
2001
2002 if not Is_Bit_Packed_Array (Etype (Prefix (N))) then
2003 Setup_Enumeration_Packed_Array_Reference (N);
2004 return;
2005 end if;
2006
2007 -- Remaining processing is for the bit-packed case
2008
2009 Obj := Relocate_Node (Prefix (N));
2010 Convert_To_Actual_Subtype (Obj);
2011 Atyp := Etype (Obj);
2012 PAT := Packed_Array_Type (Atyp);
2013 Ctyp := Component_Type (Atyp);
2014 Csiz := UI_To_Int (Component_Size (Atyp));
2015
2016 -- For the AAMP target, indexing of certain packed array is passed
2017 -- through to the back end without expansion, because the expansion
2018 -- results in very inefficient code on that target. This allows the
2019 -- GNAAMP back end to generate specialized macros that support more
2020 -- efficient indexing of packed arrays with components having sizes
2021 -- that are small powers of two.
2022
2023 if AAMP_On_Target
2024 and then (Csiz = 1 or else Csiz = 2 or else Csiz = 4)
2025 then
2026 return;
2027 end if;
2028
2029 -- Case of component size 1,2,4 or any component size for the modular
2030 -- case. These are the cases for which we can inline the code.
2031
2032 if Csiz = 1 or else Csiz = 2 or else Csiz = 4
2033 or else (Present (PAT) and then Is_Modular_Integer_Type (PAT))
2034 then
2035 Setup_Inline_Packed_Array_Reference (N, Atyp, Obj, Cmask, Shift);
2036 Lit := Make_Integer_Literal (Loc, Cmask);
2037 Set_Print_In_Hex (Lit);
2038
2039 -- Byte swapping required for the Reverse_Storage_Order case, but
2040 -- only for a free-standing object (see note on Require_Byte_Swapping
2041 -- in Expand_Bit_Packed_Element_Set).
2042
2043 if Reverse_Storage_Order (Atyp)
2044 and then Esize (Atyp) > 8
2045 and then not In_Reverse_Storage_Order_Object (Obj)
2046 then
2047 Obj := Byte_Swap (Obj);
2048 end if;
2049
2050 -- We generate a shift right to position the field, followed by a
2051 -- masking operation to extract the bit field, and we finally do an
2052 -- unchecked conversion to convert the result to the required target.
2053
2054 -- Note that the unchecked conversion automatically deals with the
2055 -- bias if we are dealing with a biased representation. What will
2056 -- happen is that we temporarily generate the biased representation,
2057 -- but almost immediately that will be converted to the original
2058 -- unbiased component type, and the bias will disappear.
2059
2060 Arg :=
2061 Make_Op_And (Loc,
2062 Left_Opnd => Make_Shift_Right (Obj, Shift),
2063 Right_Opnd => Lit);
2064
2065 -- We needed to analyze this before we do the unchecked convert
2066 -- below, but we need it temporarily attached to the tree for
2067 -- this analysis (hence the temporary Set_Parent call).
2068
2069 Set_Parent (Arg, Parent (N));
2070 Analyze_And_Resolve (Arg);
2071
2072 Rewrite (N, RJ_Unchecked_Convert_To (Ctyp, Arg));
2073
2074 -- All other component sizes for non-modular case
2075
2076 else
2077 -- We generate
2078
2079 -- Component_Type!(Get_nn (Arr'address, Subscr))
2080
2081 -- where Subscr is the computed linear subscript
2082
2083 declare
2084 Get_nn : Entity_Id;
2085 Subscr : Node_Id;
2086
2087 begin
2088 -- Acquire proper Get entity. We use the aligned or unaligned
2089 -- case as appropriate.
2090
2091 if Known_Aligned_Enough (Obj, Csiz) then
2092 Get_nn := RTE (Get_Id (Csiz));
2093 else
2094 Get_nn := RTE (GetU_Id (Csiz));
2095 end if;
2096
2097 -- Now generate the get reference
2098
2099 Compute_Linear_Subscript (Atyp, N, Subscr);
2100
2101 -- Below we make the assumption that Obj is at least byte
2102 -- aligned, since otherwise its address cannot be taken.
2103 -- The assumption holds since the only arrays that can be
2104 -- misaligned are small packed arrays which are implemented
2105 -- as a modular type, and that is not the case here.
2106
2107 Rewrite (N,
2108 Unchecked_Convert_To (Ctyp,
2109 Make_Function_Call (Loc,
2110 Name => New_Occurrence_Of (Get_nn, Loc),
2111 Parameter_Associations => New_List (
2112 Make_Attribute_Reference (Loc,
2113 Prefix => Obj,
2114 Attribute_Name => Name_Address),
2115 Subscr))));
2116 end;
2117 end if;
2118
2119 Analyze_And_Resolve (N, Ctyp, Suppress => All_Checks);
2120
2121 end Expand_Packed_Element_Reference;
2122
2123 ----------------------
2124 -- Expand_Packed_Eq --
2125 ----------------------
2126
2127 -- Handles expansion of "=" on packed array types
2128
2129 procedure Expand_Packed_Eq (N : Node_Id) is
2130 Loc : constant Source_Ptr := Sloc (N);
2131 L : constant Node_Id := Relocate_Node (Left_Opnd (N));
2132 R : constant Node_Id := Relocate_Node (Right_Opnd (N));
2133
2134 LLexpr : Node_Id;
2135 RLexpr : Node_Id;
2136
2137 Ltyp : Entity_Id;
2138 Rtyp : Entity_Id;
2139 PAT : Entity_Id;
2140
2141 begin
2142 Convert_To_Actual_Subtype (L);
2143 Convert_To_Actual_Subtype (R);
2144 Ltyp := Underlying_Type (Etype (L));
2145 Rtyp := Underlying_Type (Etype (R));
2146
2147 Convert_To_PAT_Type (L);
2148 Convert_To_PAT_Type (R);
2149 PAT := Etype (L);
2150
2151 LLexpr :=
2152 Make_Op_Multiply (Loc,
2153 Left_Opnd =>
2154 Make_Attribute_Reference (Loc,
2155 Prefix => New_Occurrence_Of (Ltyp, Loc),
2156 Attribute_Name => Name_Length),
2157 Right_Opnd =>
2158 Make_Integer_Literal (Loc, Component_Size (Ltyp)));
2159
2160 RLexpr :=
2161 Make_Op_Multiply (Loc,
2162 Left_Opnd =>
2163 Make_Attribute_Reference (Loc,
2164 Prefix => New_Occurrence_Of (Rtyp, Loc),
2165 Attribute_Name => Name_Length),
2166 Right_Opnd =>
2167 Make_Integer_Literal (Loc, Component_Size (Rtyp)));
2168
2169 -- For the modular case, we transform the comparison to:
2170
2171 -- Ltyp'Length = Rtyp'Length and then PAT!(L) = PAT!(R)
2172
2173 -- where PAT is the packed array type. This works fine, since in the
2174 -- modular case we guarantee that the unused bits are always zeroes.
2175 -- We do have to compare the lengths because we could be comparing
2176 -- two different subtypes of the same base type.
2177
2178 if Is_Modular_Integer_Type (PAT) then
2179 Rewrite (N,
2180 Make_And_Then (Loc,
2181 Left_Opnd =>
2182 Make_Op_Eq (Loc,
2183 Left_Opnd => LLexpr,
2184 Right_Opnd => RLexpr),
2185
2186 Right_Opnd =>
2187 Make_Op_Eq (Loc,
2188 Left_Opnd => L,
2189 Right_Opnd => R)));
2190
2191 -- For the non-modular case, we call a runtime routine
2192
2193 -- System.Bit_Ops.Bit_Eq
2194 -- (L'Address, L_Length, R'Address, R_Length)
2195
2196 -- where PAT is the packed array type, and the lengths are the lengths
2197 -- in bits of the original packed arrays. This routine takes care of
2198 -- not comparing the unused bits in the last byte.
2199
2200 else
2201 Rewrite (N,
2202 Make_Function_Call (Loc,
2203 Name => New_Occurrence_Of (RTE (RE_Bit_Eq), Loc),
2204 Parameter_Associations => New_List (
2205 Make_Byte_Aligned_Attribute_Reference (Loc,
2206 Prefix => L,
2207 Attribute_Name => Name_Address),
2208
2209 LLexpr,
2210
2211 Make_Byte_Aligned_Attribute_Reference (Loc,
2212 Prefix => R,
2213 Attribute_Name => Name_Address),
2214
2215 RLexpr)));
2216 end if;
2217
2218 Analyze_And_Resolve (N, Standard_Boolean, Suppress => All_Checks);
2219 end Expand_Packed_Eq;
2220
2221 -----------------------
2222 -- Expand_Packed_Not --
2223 -----------------------
2224
2225 -- Handles expansion of "not" on packed array types
2226
2227 procedure Expand_Packed_Not (N : Node_Id) is
2228 Loc : constant Source_Ptr := Sloc (N);
2229 Typ : constant Entity_Id := Etype (N);
2230 Opnd : constant Node_Id := Relocate_Node (Right_Opnd (N));
2231
2232 Rtyp : Entity_Id;
2233 PAT : Entity_Id;
2234 Lit : Node_Id;
2235
2236 begin
2237 Convert_To_Actual_Subtype (Opnd);
2238 Rtyp := Etype (Opnd);
2239
2240 -- Deal with silly False..False and True..True subtype case
2241
2242 Silly_Boolean_Array_Not_Test (N, Rtyp);
2243
2244 -- Now that the silliness is taken care of, get packed array type
2245
2246 Convert_To_PAT_Type (Opnd);
2247 PAT := Etype (Opnd);
2248
2249 -- For the case where the packed array type is a modular type, "not A"
2250 -- expands simply into:
2251
2252 -- Rtyp!(PAT!(A) xor Mask)
2253
2254 -- where PAT is the packed array type, Mask is a mask of all 1 bits of
2255 -- length equal to the size of this packed type, and Rtyp is the actual
2256 -- actual subtype of the operand.
2257
2258 Lit := Make_Integer_Literal (Loc, 2 ** RM_Size (PAT) - 1);
2259 Set_Print_In_Hex (Lit);
2260
2261 if not Is_Array_Type (PAT) then
2262 Rewrite (N,
2263 Unchecked_Convert_To (Rtyp,
2264 Make_Op_Xor (Loc,
2265 Left_Opnd => Opnd,
2266 Right_Opnd => Lit)));
2267
2268 -- For the array case, we insert the actions
2269
2270 -- Result : Typ;
2271
2272 -- System.Bit_Ops.Bit_Not
2273 -- (Opnd'Address,
2274 -- Typ'Length * Typ'Component_Size,
2275 -- Result'Address);
2276
2277 -- where Opnd is the Packed_Bytes{1,2,4} operand and the second argument
2278 -- is the length of the operand in bits. We then replace the expression
2279 -- with a reference to Result.
2280
2281 else
2282 declare
2283 Result_Ent : constant Entity_Id := Make_Temporary (Loc, 'T');
2284
2285 begin
2286 Insert_Actions (N, New_List (
2287 Make_Object_Declaration (Loc,
2288 Defining_Identifier => Result_Ent,
2289 Object_Definition => New_Occurrence_Of (Rtyp, Loc)),
2290
2291 Make_Procedure_Call_Statement (Loc,
2292 Name => New_Occurrence_Of (RTE (RE_Bit_Not), Loc),
2293 Parameter_Associations => New_List (
2294 Make_Byte_Aligned_Attribute_Reference (Loc,
2295 Prefix => Opnd,
2296 Attribute_Name => Name_Address),
2297
2298 Make_Op_Multiply (Loc,
2299 Left_Opnd =>
2300 Make_Attribute_Reference (Loc,
2301 Prefix =>
2302 New_Occurrence_Of
2303 (Etype (First_Index (Rtyp)), Loc),
2304 Attribute_Name => Name_Range_Length),
2305
2306 Right_Opnd =>
2307 Make_Integer_Literal (Loc, Component_Size (Rtyp))),
2308
2309 Make_Byte_Aligned_Attribute_Reference (Loc,
2310 Prefix => New_Occurrence_Of (Result_Ent, Loc),
2311 Attribute_Name => Name_Address)))));
2312
2313 Rewrite (N, New_Occurrence_Of (Result_Ent, Loc));
2314 end;
2315 end if;
2316
2317 Analyze_And_Resolve (N, Typ, Suppress => All_Checks);
2318 end Expand_Packed_Not;
2319
2320 -----------------------------
2321 -- Get_Base_And_Bit_Offset --
2322 -----------------------------
2323
2324 procedure Get_Base_And_Bit_Offset
2325 (N : Node_Id;
2326 Base : out Node_Id;
2327 Offset : out Node_Id)
2328 is
2329 Loc : Source_Ptr;
2330 Term : Node_Id;
2331 Atyp : Entity_Id;
2332 Subscr : Node_Id;
2333
2334 begin
2335 Base := N;
2336 Offset := Empty;
2337
2338 -- We build up an expression serially that has the form
2339
2340 -- linear-subscript * component_size for each array reference
2341 -- + field'Bit_Position for each record field
2342 -- + ...
2343
2344 loop
2345 Loc := Sloc (Base);
2346
2347 if Nkind (Base) = N_Indexed_Component then
2348 Convert_To_Actual_Subtype (Prefix (Base));
2349 Atyp := Etype (Prefix (Base));
2350 Compute_Linear_Subscript (Atyp, Base, Subscr);
2351
2352 Term :=
2353 Make_Op_Multiply (Loc,
2354 Left_Opnd => Subscr,
2355 Right_Opnd =>
2356 Make_Attribute_Reference (Loc,
2357 Prefix => New_Occurrence_Of (Atyp, Loc),
2358 Attribute_Name => Name_Component_Size));
2359
2360 elsif Nkind (Base) = N_Selected_Component then
2361 Term :=
2362 Make_Attribute_Reference (Loc,
2363 Prefix => Selector_Name (Base),
2364 Attribute_Name => Name_Bit_Position);
2365
2366 else
2367 return;
2368 end if;
2369
2370 if No (Offset) then
2371 Offset := Term;
2372
2373 else
2374 Offset :=
2375 Make_Op_Add (Loc,
2376 Left_Opnd => Offset,
2377 Right_Opnd => Term);
2378 end if;
2379
2380 Base := Prefix (Base);
2381 end loop;
2382 end Get_Base_And_Bit_Offset;
2383
2384 -------------------------------------
2385 -- Involves_Packed_Array_Reference --
2386 -------------------------------------
2387
2388 function Involves_Packed_Array_Reference (N : Node_Id) return Boolean is
2389 begin
2390 if Nkind (N) = N_Indexed_Component
2391 and then Is_Bit_Packed_Array (Etype (Prefix (N)))
2392 then
2393 return True;
2394
2395 elsif Nkind (N) = N_Selected_Component then
2396 return Involves_Packed_Array_Reference (Prefix (N));
2397
2398 else
2399 return False;
2400 end if;
2401 end Involves_Packed_Array_Reference;
2402
2403 --------------------------
2404 -- Known_Aligned_Enough --
2405 --------------------------
2406
2407 function Known_Aligned_Enough (Obj : Node_Id; Csiz : Nat) return Boolean is
2408 Typ : constant Entity_Id := Etype (Obj);
2409
2410 function In_Partially_Packed_Record (Comp : Entity_Id) return Boolean;
2411 -- If the component is in a record that contains previous packed
2412 -- components, consider it unaligned because the back-end might
2413 -- choose to pack the rest of the record. Lead to less efficient code,
2414 -- but safer vis-a-vis of back-end choices.
2415
2416 --------------------------------
2417 -- In_Partially_Packed_Record --
2418 --------------------------------
2419
2420 function In_Partially_Packed_Record (Comp : Entity_Id) return Boolean is
2421 Rec_Type : constant Entity_Id := Scope (Comp);
2422 Prev_Comp : Entity_Id;
2423
2424 begin
2425 Prev_Comp := First_Entity (Rec_Type);
2426 while Present (Prev_Comp) loop
2427 if Is_Packed (Etype (Prev_Comp)) then
2428 return True;
2429
2430 elsif Prev_Comp = Comp then
2431 return False;
2432 end if;
2433
2434 Next_Entity (Prev_Comp);
2435 end loop;
2436
2437 return False;
2438 end In_Partially_Packed_Record;
2439
2440 -- Start of processing for Known_Aligned_Enough
2441
2442 begin
2443 -- Odd bit sizes don't need alignment anyway
2444
2445 if Csiz mod 2 = 1 then
2446 return True;
2447
2448 -- If we have a specified alignment, see if it is sufficient, if not
2449 -- then we can't possibly be aligned enough in any case.
2450
2451 elsif Known_Alignment (Etype (Obj)) then
2452 -- Alignment required is 4 if size is a multiple of 4, and
2453 -- 2 otherwise (e.g. 12 bits requires 4, 10 bits requires 2)
2454
2455 if Alignment (Etype (Obj)) < 4 - (Csiz mod 4) then
2456 return False;
2457 end if;
2458 end if;
2459
2460 -- OK, alignment should be sufficient, if object is aligned
2461
2462 -- If object is strictly aligned, then it is definitely aligned
2463
2464 if Strict_Alignment (Typ) then
2465 return True;
2466
2467 -- Case of subscripted array reference
2468
2469 elsif Nkind (Obj) = N_Indexed_Component then
2470
2471 -- If we have a pointer to an array, then this is definitely
2472 -- aligned, because pointers always point to aligned versions.
2473
2474 if Is_Access_Type (Etype (Prefix (Obj))) then
2475 return True;
2476
2477 -- Otherwise, go look at the prefix
2478
2479 else
2480 return Known_Aligned_Enough (Prefix (Obj), Csiz);
2481 end if;
2482
2483 -- Case of record field
2484
2485 elsif Nkind (Obj) = N_Selected_Component then
2486
2487 -- What is significant here is whether the record type is packed
2488
2489 if Is_Record_Type (Etype (Prefix (Obj)))
2490 and then Is_Packed (Etype (Prefix (Obj)))
2491 then
2492 return False;
2493
2494 -- Or the component has a component clause which might cause
2495 -- the component to become unaligned (we can't tell if the
2496 -- backend is doing alignment computations).
2497
2498 elsif Present (Component_Clause (Entity (Selector_Name (Obj)))) then
2499 return False;
2500
2501 elsif In_Partially_Packed_Record (Entity (Selector_Name (Obj))) then
2502 return False;
2503
2504 -- In all other cases, go look at prefix
2505
2506 else
2507 return Known_Aligned_Enough (Prefix (Obj), Csiz);
2508 end if;
2509
2510 elsif Nkind (Obj) = N_Type_Conversion then
2511 return Known_Aligned_Enough (Expression (Obj), Csiz);
2512
2513 -- For a formal parameter, it is safer to assume that it is not
2514 -- aligned, because the formal may be unconstrained while the actual
2515 -- is constrained. In this situation, a small constrained packed
2516 -- array, represented in modular form, may be unaligned.
2517
2518 elsif Is_Entity_Name (Obj) then
2519 return not Is_Formal (Entity (Obj));
2520 else
2521
2522 -- If none of the above, must be aligned
2523 return True;
2524 end if;
2525 end Known_Aligned_Enough;
2526
2527 ---------------------
2528 -- Make_Shift_Left --
2529 ---------------------
2530
2531 function Make_Shift_Left (N : Node_Id; S : Node_Id) return Node_Id is
2532 Nod : Node_Id;
2533
2534 begin
2535 if Compile_Time_Known_Value (S) and then Expr_Value (S) = 0 then
2536 return N;
2537 else
2538 Nod :=
2539 Make_Op_Shift_Left (Sloc (N),
2540 Left_Opnd => N,
2541 Right_Opnd => S);
2542 Set_Shift_Count_OK (Nod, True);
2543 return Nod;
2544 end if;
2545 end Make_Shift_Left;
2546
2547 ----------------------
2548 -- Make_Shift_Right --
2549 ----------------------
2550
2551 function Make_Shift_Right (N : Node_Id; S : Node_Id) return Node_Id is
2552 Nod : Node_Id;
2553
2554 begin
2555 if Compile_Time_Known_Value (S) and then Expr_Value (S) = 0 then
2556 return N;
2557 else
2558 Nod :=
2559 Make_Op_Shift_Right (Sloc (N),
2560 Left_Opnd => N,
2561 Right_Opnd => S);
2562 Set_Shift_Count_OK (Nod, True);
2563 return Nod;
2564 end if;
2565 end Make_Shift_Right;
2566
2567 -----------------------------
2568 -- RJ_Unchecked_Convert_To --
2569 -----------------------------
2570
2571 function RJ_Unchecked_Convert_To
2572 (Typ : Entity_Id;
2573 Expr : Node_Id) return Node_Id
2574 is
2575 Source_Typ : constant Entity_Id := Etype (Expr);
2576 Target_Typ : constant Entity_Id := Typ;
2577
2578 Src : Node_Id := Expr;
2579
2580 Source_Siz : Nat;
2581 Target_Siz : Nat;
2582
2583 begin
2584 Source_Siz := UI_To_Int (RM_Size (Source_Typ));
2585 Target_Siz := UI_To_Int (RM_Size (Target_Typ));
2586
2587 -- First step, if the source type is not a discrete type, then we first
2588 -- convert to a modular type of the source length, since otherwise, on
2589 -- a big-endian machine, we get left-justification. We do it for little-
2590 -- endian machines as well, because there might be junk bits that are
2591 -- not cleared if the type is not numeric.
2592
2593 if Source_Siz /= Target_Siz
2594 and then not Is_Discrete_Type (Source_Typ)
2595 then
2596 Src := Unchecked_Convert_To (RTE (Bits_Id (Source_Siz)), Src);
2597 end if;
2598
2599 -- In the big endian case, if the lengths of the two types differ, then
2600 -- we must worry about possible left justification in the conversion,
2601 -- and avoiding that is what this is all about.
2602
2603 if Bytes_Big_Endian and then Source_Siz /= Target_Siz then
2604
2605 -- Next step. If the target is not a discrete type, then we first
2606 -- convert to a modular type of the target length, since otherwise,
2607 -- on a big-endian machine, we get left-justification.
2608
2609 if not Is_Discrete_Type (Target_Typ) then
2610 Src := Unchecked_Convert_To (RTE (Bits_Id (Target_Siz)), Src);
2611 end if;
2612 end if;
2613
2614 -- And now we can do the final conversion to the target type
2615
2616 return Unchecked_Convert_To (Target_Typ, Src);
2617 end RJ_Unchecked_Convert_To;
2618
2619 ----------------------------------------------
2620 -- Setup_Enumeration_Packed_Array_Reference --
2621 ----------------------------------------------
2622
2623 -- All we have to do here is to find the subscripts that correspond to the
2624 -- index positions that have non-standard enumeration types and insert a
2625 -- Pos attribute to get the proper subscript value.
2626
2627 -- Finally the prefix must be uncheck-converted to the corresponding packed
2628 -- array type.
2629
2630 -- Note that the component type is unchanged, so we do not need to fiddle
2631 -- with the types (Gigi always automatically takes the packed array type if
2632 -- it is set, as it will be in this case).
2633
2634 procedure Setup_Enumeration_Packed_Array_Reference (N : Node_Id) is
2635 Pfx : constant Node_Id := Prefix (N);
2636 Typ : constant Entity_Id := Etype (N);
2637 Exprs : constant List_Id := Expressions (N);
2638 Expr : Node_Id;
2639
2640 begin
2641 -- If the array is unconstrained, then we replace the array reference
2642 -- with its actual subtype. This actual subtype will have a packed array
2643 -- type with appropriate bounds.
2644
2645 if not Is_Constrained (Packed_Array_Type (Etype (Pfx))) then
2646 Convert_To_Actual_Subtype (Pfx);
2647 end if;
2648
2649 Expr := First (Exprs);
2650 while Present (Expr) loop
2651 declare
2652 Loc : constant Source_Ptr := Sloc (Expr);
2653 Expr_Typ : constant Entity_Id := Etype (Expr);
2654
2655 begin
2656 if Is_Enumeration_Type (Expr_Typ)
2657 and then Has_Non_Standard_Rep (Expr_Typ)
2658 then
2659 Rewrite (Expr,
2660 Make_Attribute_Reference (Loc,
2661 Prefix => New_Occurrence_Of (Expr_Typ, Loc),
2662 Attribute_Name => Name_Pos,
2663 Expressions => New_List (Relocate_Node (Expr))));
2664 Analyze_And_Resolve (Expr, Standard_Natural);
2665 end if;
2666 end;
2667
2668 Next (Expr);
2669 end loop;
2670
2671 Rewrite (N,
2672 Make_Indexed_Component (Sloc (N),
2673 Prefix =>
2674 Unchecked_Convert_To (Packed_Array_Type (Etype (Pfx)), Pfx),
2675 Expressions => Exprs));
2676
2677 Analyze_And_Resolve (N, Typ);
2678 end Setup_Enumeration_Packed_Array_Reference;
2679
2680 -----------------------------------------
2681 -- Setup_Inline_Packed_Array_Reference --
2682 -----------------------------------------
2683
2684 procedure Setup_Inline_Packed_Array_Reference
2685 (N : Node_Id;
2686 Atyp : Entity_Id;
2687 Obj : in out Node_Id;
2688 Cmask : out Uint;
2689 Shift : out Node_Id)
2690 is
2691 Loc : constant Source_Ptr := Sloc (N);
2692 PAT : Entity_Id;
2693 Otyp : Entity_Id;
2694 Csiz : Uint;
2695 Osiz : Uint;
2696
2697 begin
2698 Csiz := Component_Size (Atyp);
2699
2700 Convert_To_PAT_Type (Obj);
2701 PAT := Etype (Obj);
2702
2703 Cmask := 2 ** Csiz - 1;
2704
2705 if Is_Array_Type (PAT) then
2706 Otyp := Component_Type (PAT);
2707 Osiz := Component_Size (PAT);
2708
2709 else
2710 Otyp := PAT;
2711
2712 -- In the case where the PAT is a modular type, we want the actual
2713 -- size in bits of the modular value we use. This is neither the
2714 -- Object_Size nor the Value_Size, either of which may have been
2715 -- reset to strange values, but rather the minimum size. Note that
2716 -- since this is a modular type with full range, the issue of
2717 -- biased representation does not arise.
2718
2719 Osiz := UI_From_Int (Minimum_Size (Otyp));
2720 end if;
2721
2722 Compute_Linear_Subscript (Atyp, N, Shift);
2723
2724 -- If the component size is not 1, then the subscript must be multiplied
2725 -- by the component size to get the shift count.
2726
2727 if Csiz /= 1 then
2728 Shift :=
2729 Make_Op_Multiply (Loc,
2730 Left_Opnd => Make_Integer_Literal (Loc, Csiz),
2731 Right_Opnd => Shift);
2732 end if;
2733
2734 -- If we have the array case, then this shift count must be broken down
2735 -- into a byte subscript, and a shift within the byte.
2736
2737 if Is_Array_Type (PAT) then
2738
2739 declare
2740 New_Shift : Node_Id;
2741
2742 begin
2743 -- We must analyze shift, since we will duplicate it
2744
2745 Set_Parent (Shift, N);
2746 Analyze_And_Resolve
2747 (Shift, Standard_Integer, Suppress => All_Checks);
2748
2749 -- The shift count within the word is
2750 -- shift mod Osiz
2751
2752 New_Shift :=
2753 Make_Op_Mod (Loc,
2754 Left_Opnd => Duplicate_Subexpr (Shift),
2755 Right_Opnd => Make_Integer_Literal (Loc, Osiz));
2756
2757 -- The subscript to be used on the PAT array is
2758 -- shift / Osiz
2759
2760 Obj :=
2761 Make_Indexed_Component (Loc,
2762 Prefix => Obj,
2763 Expressions => New_List (
2764 Make_Op_Divide (Loc,
2765 Left_Opnd => Duplicate_Subexpr (Shift),
2766 Right_Opnd => Make_Integer_Literal (Loc, Osiz))));
2767
2768 Shift := New_Shift;
2769 end;
2770
2771 -- For the modular integer case, the object to be manipulated is the
2772 -- entire array, so Obj is unchanged. Note that we will reset its type
2773 -- to PAT before returning to the caller.
2774
2775 else
2776 null;
2777 end if;
2778
2779 -- The one remaining step is to modify the shift count for the
2780 -- big-endian case. Consider the following example in a byte:
2781
2782 -- xxxxxxxx bits of byte
2783 -- vvvvvvvv bits of value
2784 -- 33221100 little-endian numbering
2785 -- 00112233 big-endian numbering
2786
2787 -- Here we have the case of 2-bit fields
2788
2789 -- For the little-endian case, we already have the proper shift count
2790 -- set, e.g. for element 2, the shift count is 2*2 = 4.
2791
2792 -- For the big endian case, we have to adjust the shift count, computing
2793 -- it as (N - F) - Shift, where N is the number of bits in an element of
2794 -- the array used to implement the packed array, F is the number of bits
2795 -- in a source array element, and Shift is the count so far computed.
2796
2797 -- We also have to adjust if the storage order is reversed
2798
2799 if Bytes_Big_Endian xor Reverse_Storage_Order (Base_Type (Atyp)) then
2800 Shift :=
2801 Make_Op_Subtract (Loc,
2802 Left_Opnd => Make_Integer_Literal (Loc, Osiz - Csiz),
2803 Right_Opnd => Shift);
2804 end if;
2805
2806 Set_Parent (Shift, N);
2807 Set_Parent (Obj, N);
2808 Analyze_And_Resolve (Obj, Otyp, Suppress => All_Checks);
2809 Analyze_And_Resolve (Shift, Standard_Integer, Suppress => All_Checks);
2810
2811 -- Make sure final type of object is the appropriate packed type
2812
2813 Set_Etype (Obj, Otyp);
2814
2815 end Setup_Inline_Packed_Array_Reference;
2816
2817 end Exp_Pakd;
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