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1 706 jeremybenn
------------------------------------------------------------------------------
2
--                                                                          --
3
--                         GNAT COMPILER COMPONENTS                         --
4
--                                                                          --
5
--                             E X P _ P A K D                              --
6
--                                                                          --
7
--                                 B o d y                                  --
8
--                                                                          --
9
--          Copyright (C) 1992-2011, 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
   ------------------------------
547
   -- Compute_Linear_Subscript --
548
   ------------------------------
549
 
550
   procedure Compute_Linear_Subscript
551
     (Atyp   : Entity_Id;
552
      N      : Node_Id;
553
      Subscr : out Node_Id)
554
   is
555
      Loc    : constant Source_Ptr := Sloc (N);
556
      Oldsub : Node_Id;
557
      Newsub : Node_Id;
558
      Indx   : Node_Id;
559
      Styp   : Entity_Id;
560
 
561
   begin
562
      Subscr := Empty;
563
 
564
      --  Loop through dimensions
565
 
566
      Indx   := First_Index (Atyp);
567
      Oldsub := First (Expressions (N));
568
 
569
      while Present (Indx) loop
570
         Styp := Etype (Indx);
571
         Newsub := Relocate_Node (Oldsub);
572
 
573
         --  Get expression for the subscript value. First, if Do_Range_Check
574
         --  is set on a subscript, then we must do a range check against the
575
         --  original bounds (not the bounds of the packed array type). We do
576
         --  this by introducing a subtype conversion.
577
 
578
         if Do_Range_Check (Newsub)
579
           and then Etype (Newsub) /= Styp
580
         then
581
            Newsub := Convert_To (Styp, Newsub);
582
         end if;
583
 
584
         --  Now evolve the expression for the subscript. First convert
585
         --  the subscript to be zero based and of an integer type.
586
 
587
         --  Case of integer type, where we just subtract to get lower bound
588
 
589
         if Is_Integer_Type (Styp) then
590
 
591
            --  If length of integer type is smaller than standard integer,
592
            --  then we convert to integer first, then do the subtract
593
 
594
            --  Integer (subscript) - Integer (Styp'First)
595
 
596
            if Esize (Styp) < Esize (Standard_Integer) then
597
               Newsub :=
598
                 Make_Op_Subtract (Loc,
599
                   Left_Opnd => Convert_To (Standard_Integer, Newsub),
600
                 Right_Opnd =>
601
                   Convert_To (Standard_Integer,
602
                     Make_Attribute_Reference (Loc,
603
                       Prefix         => New_Occurrence_Of (Styp, Loc),
604
                       Attribute_Name => Name_First)));
605
 
606
            --  For larger integer types, subtract first, then convert to
607
            --  integer, this deals with strange long long integer bounds.
608
 
609
            --    Integer (subscript - Styp'First)
610
 
611
            else
612
               Newsub :=
613
                 Convert_To (Standard_Integer,
614
                   Make_Op_Subtract (Loc,
615
                     Left_Opnd => Newsub,
616
                   Right_Opnd =>
617
                     Make_Attribute_Reference (Loc,
618
                       Prefix         => New_Occurrence_Of (Styp, Loc),
619
                       Attribute_Name => Name_First)));
620
            end if;
621
 
622
         --  For the enumeration case, we have to use 'Pos to get the value
623
         --  to work with before subtracting the lower bound.
624
 
625
         --    Integer (Styp'Pos (subscr)) - Integer (Styp'Pos (Styp'First));
626
 
627
         --  This is not quite right for bizarre cases where the size of the
628
         --  enumeration type is > Integer'Size bits due to rep clause ???
629
 
630
         else
631
            pragma Assert (Is_Enumeration_Type (Styp));
632
 
633
            Newsub :=
634
              Make_Op_Subtract (Loc,
635
                Left_Opnd => Convert_To (Standard_Integer,
636
                  Make_Attribute_Reference (Loc,
637
                    Prefix         => New_Occurrence_Of (Styp, Loc),
638
                    Attribute_Name => Name_Pos,
639
                    Expressions    => New_List (Newsub))),
640
 
641
                Right_Opnd =>
642
                  Convert_To (Standard_Integer,
643
                    Make_Attribute_Reference (Loc,
644
                      Prefix         => New_Occurrence_Of (Styp, Loc),
645
                      Attribute_Name => Name_Pos,
646
                      Expressions    => New_List (
647
                        Make_Attribute_Reference (Loc,
648
                          Prefix         => New_Occurrence_Of (Styp, Loc),
649
                          Attribute_Name => Name_First)))));
650
         end if;
651
 
652
         Set_Paren_Count (Newsub, 1);
653
 
654
         --  For the first subscript, we just copy that subscript value
655
 
656
         if No (Subscr) then
657
            Subscr := Newsub;
658
 
659
         --  Otherwise, we must multiply what we already have by the current
660
         --  stride and then add in the new value to the evolving subscript.
661
 
662
         else
663
            Subscr :=
664
              Make_Op_Add (Loc,
665
                Left_Opnd =>
666
                  Make_Op_Multiply (Loc,
667
                    Left_Opnd  => Subscr,
668
                    Right_Opnd =>
669
                      Make_Attribute_Reference (Loc,
670
                        Attribute_Name => Name_Range_Length,
671
                        Prefix         => New_Occurrence_Of (Styp, Loc))),
672
                Right_Opnd => Newsub);
673
         end if;
674
 
675
         --  Move to next subscript
676
 
677
         Next_Index (Indx);
678
         Next (Oldsub);
679
      end loop;
680
   end Compute_Linear_Subscript;
681
 
682
   -------------------------
683
   -- Convert_To_PAT_Type --
684
   -------------------------
685
 
686
   --  The PAT is always obtained from the actual subtype
687
 
688
   procedure Convert_To_PAT_Type (Aexp : Node_Id) is
689
      Act_ST : Entity_Id;
690
 
691
   begin
692
      Convert_To_Actual_Subtype (Aexp);
693
      Act_ST := Underlying_Type (Etype (Aexp));
694
      Create_Packed_Array_Type (Act_ST);
695
 
696
      --  Just replace the etype with the packed array type. This works because
697
      --  the expression will not be further analyzed, and Gigi considers the
698
      --  two types equivalent in any case.
699
 
700
      --  This is not strictly the case ??? If the reference is an actual in
701
      --  call, the expansion of the prefix is delayed, and must be reanalyzed,
702
      --  see Reset_Packed_Prefix. On the other hand, if the prefix is a simple
703
      --  array reference, reanalysis can produce spurious type errors when the
704
      --  PAT type is replaced again with the original type of the array. Same
705
      --  for the case of a dereference. Ditto for function calls: expansion
706
      --  may introduce additional actuals which will trigger errors if call is
707
      --  reanalyzed. The following is correct and minimal, but the handling of
708
      --  more complex packed expressions in actuals is confused. Probably the
709
      --  problem only remains for actuals in calls.
710
 
711
      Set_Etype (Aexp, Packed_Array_Type (Act_ST));
712
 
713
      if Is_Entity_Name (Aexp)
714
        or else
715
           (Nkind (Aexp) = N_Indexed_Component
716
             and then Is_Entity_Name (Prefix (Aexp)))
717
        or else Nkind_In (Aexp, N_Explicit_Dereference, N_Function_Call)
718
      then
719
         Set_Analyzed (Aexp);
720
      end if;
721
   end Convert_To_PAT_Type;
722
 
723
   ------------------------------
724
   -- Create_Packed_Array_Type --
725
   ------------------------------
726
 
727
   procedure Create_Packed_Array_Type (Typ : Entity_Id) is
728
      Loc      : constant Source_Ptr := Sloc (Typ);
729
      Ctyp     : constant Entity_Id  := Component_Type (Typ);
730
      Csize    : constant Uint       := Component_Size (Typ);
731
 
732
      Ancest   : Entity_Id;
733
      PB_Type  : Entity_Id;
734
      PASize   : Uint;
735
      Decl     : Node_Id;
736
      PAT      : Entity_Id;
737
      Len_Dim  : Node_Id;
738
      Len_Expr : Node_Id;
739
      Len_Bits : Uint;
740
      Bits_U1  : Node_Id;
741
      PAT_High : Node_Id;
742
      Btyp     : Entity_Id;
743
      Lit      : Node_Id;
744
 
745
      procedure Install_PAT;
746
      --  This procedure is called with Decl set to the declaration for the
747
      --  packed array type. It creates the type and installs it as required.
748
 
749
      procedure Set_PB_Type;
750
      --  Sets PB_Type to Packed_Bytes{1,2,4} as required by the alignment
751
      --  requirements (see documentation in the spec of this package).
752
 
753
      -----------------
754
      -- Install_PAT --
755
      -----------------
756
 
757
      procedure Install_PAT is
758
         Pushed_Scope : Boolean := False;
759
 
760
      begin
761
         --  We do not want to put the declaration we have created in the tree
762
         --  since it is often hard, and sometimes impossible to find a proper
763
         --  place for it (the impossible case arises for a packed array type
764
         --  with bounds depending on the discriminant, a declaration cannot
765
         --  be put inside the record, and the reference to the discriminant
766
         --  cannot be outside the record).
767
 
768
         --  The solution is to analyze the declaration while temporarily
769
         --  attached to the tree at an appropriate point, and then we install
770
         --  the resulting type as an Itype in the packed array type field of
771
         --  the original type, so that no explicit declaration is required.
772
 
773
         --  Note: the packed type is created in the scope of its parent
774
         --  type. There are at least some cases where the current scope
775
         --  is deeper, and so when this is the case, we temporarily reset
776
         --  the scope for the definition. This is clearly safe, since the
777
         --  first use of the packed array type will be the implicit
778
         --  reference from the corresponding unpacked type when it is
779
         --  elaborated.
780
 
781
         if Is_Itype (Typ) then
782
            Set_Parent (Decl, Associated_Node_For_Itype (Typ));
783
         else
784
            Set_Parent (Decl, Declaration_Node (Typ));
785
         end if;
786
 
787
         if Scope (Typ) /= Current_Scope then
788
            Push_Scope (Scope (Typ));
789
            Pushed_Scope := True;
790
         end if;
791
 
792
         Set_Is_Itype (PAT, True);
793
         Set_Packed_Array_Type (Typ, PAT);
794
         Analyze (Decl, Suppress => All_Checks);
795
 
796
         if Pushed_Scope then
797
            Pop_Scope;
798
         end if;
799
 
800
         --  Set Esize and RM_Size to the actual size of the packed object
801
         --  Do not reset RM_Size if already set, as happens in the case of
802
         --  a modular type.
803
 
804
         if Unknown_Esize (PAT) then
805
            Set_Esize (PAT, PASize);
806
         end if;
807
 
808
         if Unknown_RM_Size (PAT) then
809
            Set_RM_Size (PAT, PASize);
810
         end if;
811
 
812
         Adjust_Esize_Alignment (PAT);
813
 
814
         --  Set remaining fields of packed array type
815
 
816
         Init_Alignment                (PAT);
817
         Set_Parent                    (PAT, Empty);
818
         Set_Associated_Node_For_Itype (PAT, Typ);
819
         Set_Is_Packed_Array_Type      (PAT, True);
820
         Set_Original_Array_Type       (PAT, Typ);
821
 
822
         --  We definitely do not want to delay freezing for packed array
823
         --  types. This is of particular importance for the itypes that
824
         --  are generated for record components depending on discriminants
825
         --  where there is no place to put the freeze node.
826
 
827
         Set_Has_Delayed_Freeze (PAT, False);
828
         Set_Has_Delayed_Freeze (Etype (PAT), False);
829
 
830
         --  If we did allocate a freeze node, then clear out the reference
831
         --  since it is obsolete (should we delete the freeze node???)
832
 
833
         Set_Freeze_Node (PAT, Empty);
834
         Set_Freeze_Node (Etype (PAT), Empty);
835
      end Install_PAT;
836
 
837
      -----------------
838
      -- Set_PB_Type --
839
      -----------------
840
 
841
      procedure Set_PB_Type is
842
      begin
843
         --  If the user has specified an explicit alignment for the
844
         --  type or component, take it into account.
845
 
846
         if Csize <= 2 or else Csize = 4 or else Csize mod 2 /= 0
847
           or else Alignment (Typ) = 1
848
           or else Component_Alignment (Typ) = Calign_Storage_Unit
849
         then
850
            PB_Type := RTE (RE_Packed_Bytes1);
851
 
852
         elsif Csize mod 4 /= 0
853
           or else Alignment (Typ) = 2
854
         then
855
            PB_Type := RTE (RE_Packed_Bytes2);
856
 
857
         else
858
            PB_Type := RTE (RE_Packed_Bytes4);
859
         end if;
860
      end Set_PB_Type;
861
 
862
   --  Start of processing for Create_Packed_Array_Type
863
 
864
   begin
865
      --  If we already have a packed array type, nothing to do
866
 
867
      if Present (Packed_Array_Type (Typ)) then
868
         return;
869
      end if;
870
 
871
      --  If our immediate ancestor subtype is constrained, and it already
872
      --  has a packed array type, then just share the same type, since the
873
      --  bounds must be the same. If the ancestor is not an array type but
874
      --  a private type, as can happen with multiple instantiations, create
875
      --  a new packed type, to avoid privacy issues.
876
 
877
      if Ekind (Typ) = E_Array_Subtype then
878
         Ancest := Ancestor_Subtype (Typ);
879
 
880
         if Present (Ancest)
881
           and then Is_Array_Type (Ancest)
882
           and then Is_Constrained (Ancest)
883
           and then Present (Packed_Array_Type (Ancest))
884
         then
885
            Set_Packed_Array_Type (Typ, Packed_Array_Type (Ancest));
886
            return;
887
         end if;
888
      end if;
889
 
890
      --  We preset the result type size from the size of the original array
891
      --  type, since this size clearly belongs to the packed array type. The
892
      --  size of the conceptual unpacked type is always set to unknown.
893
 
894
      PASize := RM_Size (Typ);
895
 
896
      --  Case of an array where at least one index is of an enumeration
897
      --  type with a non-standard representation, but the component size
898
      --  is not appropriate for bit packing. This is the case where we
899
      --  have Is_Packed set (we would never be in this unit otherwise),
900
      --  but Is_Bit_Packed_Array is false.
901
 
902
      --  Note that if the component size is appropriate for bit packing,
903
      --  then the circuit for the computation of the subscript properly
904
      --  deals with the non-standard enumeration type case by taking the
905
      --  Pos anyway.
906
 
907
      if not Is_Bit_Packed_Array (Typ) then
908
 
909
         --  Here we build a declaration:
910
 
911
         --    type tttP is array (index1, index2, ...) of component_type
912
 
913
         --  where index1, index2, are the index types. These are the same
914
         --  as the index types of the original array, except for the non-
915
         --  standard representation enumeration type case, where we have
916
         --  two subcases.
917
 
918
         --  For the unconstrained array case, we use
919
 
920
         --    Natural range <>
921
 
922
         --  For the constrained case, we use
923
 
924
         --    Natural range Enum_Type'Pos (Enum_Type'First) ..
925
         --                  Enum_Type'Pos (Enum_Type'Last);
926
 
927
         PAT :=
928
           Make_Defining_Identifier (Loc,
929
             Chars => New_External_Name (Chars (Typ), 'P'));
930
 
931
         Set_Packed_Array_Type (Typ, PAT);
932
 
933
         declare
934
            Indexes   : constant List_Id := New_List;
935
            Indx      : Node_Id;
936
            Indx_Typ  : Entity_Id;
937
            Enum_Case : Boolean;
938
            Typedef   : Node_Id;
939
 
940
         begin
941
            Indx := First_Index (Typ);
942
 
943
            while Present (Indx) loop
944
               Indx_Typ := Etype (Indx);
945
 
946
               Enum_Case := Is_Enumeration_Type (Indx_Typ)
947
                              and then Has_Non_Standard_Rep (Indx_Typ);
948
 
949
               --  Unconstrained case
950
 
951
               if not Is_Constrained (Typ) then
952
                  if Enum_Case then
953
                     Indx_Typ := Standard_Natural;
954
                  end if;
955
 
956
                  Append_To (Indexes, New_Occurrence_Of (Indx_Typ, Loc));
957
 
958
               --  Constrained case
959
 
960
               else
961
                  if not Enum_Case then
962
                     Append_To (Indexes, New_Occurrence_Of (Indx_Typ, Loc));
963
 
964
                  else
965
                     Append_To (Indexes,
966
                       Make_Subtype_Indication (Loc,
967
                         Subtype_Mark =>
968
                           New_Occurrence_Of (Standard_Natural, Loc),
969
                         Constraint =>
970
                           Make_Range_Constraint (Loc,
971
                             Range_Expression =>
972
                               Make_Range (Loc,
973
                                 Low_Bound =>
974
                                   Make_Attribute_Reference (Loc,
975
                                     Prefix         =>
976
                                       New_Occurrence_Of (Indx_Typ, Loc),
977
                                     Attribute_Name => Name_Pos,
978
                                     Expressions    => New_List (
979
                                       Make_Attribute_Reference (Loc,
980
                                         Prefix         =>
981
                                           New_Occurrence_Of (Indx_Typ, Loc),
982
                                         Attribute_Name => Name_First))),
983
 
984
                                 High_Bound =>
985
                                   Make_Attribute_Reference (Loc,
986
                                     Prefix         =>
987
                                       New_Occurrence_Of (Indx_Typ, Loc),
988
                                     Attribute_Name => Name_Pos,
989
                                     Expressions    => New_List (
990
                                       Make_Attribute_Reference (Loc,
991
                                         Prefix         =>
992
                                           New_Occurrence_Of (Indx_Typ, Loc),
993
                                         Attribute_Name => Name_Last)))))));
994
 
995
                  end if;
996
               end if;
997
 
998
               Next_Index (Indx);
999
            end loop;
1000
 
1001
            if not Is_Constrained (Typ) then
1002
               Typedef :=
1003
                 Make_Unconstrained_Array_Definition (Loc,
1004
                   Subtype_Marks => Indexes,
1005
                   Component_Definition =>
1006
                     Make_Component_Definition (Loc,
1007
                       Aliased_Present    => False,
1008
                       Subtype_Indication =>
1009
                          New_Occurrence_Of (Ctyp, Loc)));
1010
 
1011
            else
1012
               Typedef :=
1013
                  Make_Constrained_Array_Definition (Loc,
1014
                    Discrete_Subtype_Definitions => Indexes,
1015
                    Component_Definition =>
1016
                      Make_Component_Definition (Loc,
1017
                        Aliased_Present    => False,
1018
                        Subtype_Indication =>
1019
                          New_Occurrence_Of (Ctyp, Loc)));
1020
            end if;
1021
 
1022
            Decl :=
1023
              Make_Full_Type_Declaration (Loc,
1024
                Defining_Identifier => PAT,
1025
                Type_Definition => Typedef);
1026
         end;
1027
 
1028
         --  Set type as packed array type and install it
1029
 
1030
         Set_Is_Packed_Array_Type (PAT);
1031
         Install_PAT;
1032
         return;
1033
 
1034
      --  Case of bit-packing required for unconstrained array. We create
1035
      --  a subtype that is equivalent to use Packed_Bytes{1,2,4} as needed.
1036
 
1037
      elsif not Is_Constrained (Typ) then
1038
         PAT :=
1039
           Make_Defining_Identifier (Loc,
1040
             Chars => Make_Packed_Array_Type_Name (Typ, Csize));
1041
 
1042
         Set_Packed_Array_Type (Typ, PAT);
1043
         Set_PB_Type;
1044
 
1045
         Decl :=
1046
           Make_Subtype_Declaration (Loc,
1047
             Defining_Identifier => PAT,
1048
               Subtype_Indication => New_Occurrence_Of (PB_Type, Loc));
1049
         Install_PAT;
1050
         return;
1051
 
1052
      --  Remaining code is for the case of bit-packing for constrained array
1053
 
1054
      --  The name of the packed array subtype is
1055
 
1056
      --    ttt___Xsss
1057
 
1058
      --  where sss is the component size in bits and ttt is the name of
1059
      --  the parent packed type.
1060
 
1061
      else
1062
         PAT :=
1063
           Make_Defining_Identifier (Loc,
1064
             Chars => Make_Packed_Array_Type_Name (Typ, Csize));
1065
 
1066
         Set_Packed_Array_Type (Typ, PAT);
1067
 
1068
         --  Build an expression for the length of the array in bits.
1069
         --  This is the product of the length of each of the dimensions
1070
 
1071
         declare
1072
            J : Nat := 1;
1073
 
1074
         begin
1075
            Len_Expr := Empty; -- suppress junk warning
1076
 
1077
            loop
1078
               Len_Dim :=
1079
                 Make_Attribute_Reference (Loc,
1080
                   Attribute_Name => Name_Length,
1081
                   Prefix         => New_Occurrence_Of (Typ, Loc),
1082
                   Expressions    => New_List (
1083
                     Make_Integer_Literal (Loc, J)));
1084
 
1085
               if J = 1 then
1086
                  Len_Expr := Len_Dim;
1087
 
1088
               else
1089
                  Len_Expr :=
1090
                    Make_Op_Multiply (Loc,
1091
                      Left_Opnd  => Len_Expr,
1092
                      Right_Opnd => Len_Dim);
1093
               end if;
1094
 
1095
               J := J + 1;
1096
               exit when J > Number_Dimensions (Typ);
1097
            end loop;
1098
         end;
1099
 
1100
         --  Temporarily attach the length expression to the tree and analyze
1101
         --  and resolve it, so that we can test its value. We assume that the
1102
         --  total length fits in type Integer. This expression may involve
1103
         --  discriminants, so we treat it as a default/per-object expression.
1104
 
1105
         Set_Parent (Len_Expr, Typ);
1106
         Preanalyze_Spec_Expression (Len_Expr, Standard_Long_Long_Integer);
1107
 
1108
         --  Use a modular type if possible. We can do this if we have
1109
         --  static bounds, and the length is small enough, and the length
1110
         --  is not zero. We exclude the zero length case because the size
1111
         --  of things is always at least one, and the zero length object
1112
         --  would have an anomalous size.
1113
 
1114
         if Compile_Time_Known_Value (Len_Expr) then
1115
            Len_Bits := Expr_Value (Len_Expr) * Csize;
1116
 
1117
            --  Check for size known to be too large
1118
 
1119
            if Len_Bits >
1120
              Uint_2 ** (Standard_Integer_Size - 1) * System_Storage_Unit
1121
            then
1122
               if System_Storage_Unit = 8 then
1123
                  Error_Msg_N
1124
                    ("packed array size cannot exceed " &
1125
                     "Integer''Last bytes", Typ);
1126
               else
1127
                  Error_Msg_N
1128
                    ("packed array size cannot exceed " &
1129
                     "Integer''Last storage units", Typ);
1130
               end if;
1131
 
1132
               --  Reset length to arbitrary not too high value to continue
1133
 
1134
               Len_Expr := Make_Integer_Literal (Loc, 65535);
1135
               Analyze_And_Resolve (Len_Expr, Standard_Long_Long_Integer);
1136
            end if;
1137
 
1138
            --  We normally consider small enough to mean no larger than the
1139
            --  value of System_Max_Binary_Modulus_Power, checking that in the
1140
            --  case of values longer than word size, we have long shifts.
1141
 
1142
            if Len_Bits > 0
1143
              and then
1144
                (Len_Bits <= System_Word_Size
1145
                   or else (Len_Bits <= System_Max_Binary_Modulus_Power
1146
                              and then Support_Long_Shifts_On_Target))
1147
            then
1148
               --  We can use the modular type, it has the form:
1149
 
1150
               --    subtype tttPn is btyp
1151
               --      range 0 .. 2 ** ((Typ'Length (1)
1152
               --                * ... * Typ'Length (n)) * Csize) - 1;
1153
 
1154
               --  The bounds are statically known, and btyp is one of the
1155
               --  unsigned types, depending on the length.
1156
 
1157
               if Len_Bits <= Standard_Short_Short_Integer_Size then
1158
                  Btyp := RTE (RE_Short_Short_Unsigned);
1159
 
1160
               elsif Len_Bits <= Standard_Short_Integer_Size then
1161
                  Btyp := RTE (RE_Short_Unsigned);
1162
 
1163
               elsif Len_Bits <= Standard_Integer_Size then
1164
                  Btyp := RTE (RE_Unsigned);
1165
 
1166
               elsif Len_Bits <= Standard_Long_Integer_Size then
1167
                  Btyp := RTE (RE_Long_Unsigned);
1168
 
1169
               else
1170
                  Btyp := RTE (RE_Long_Long_Unsigned);
1171
               end if;
1172
 
1173
               Lit := Make_Integer_Literal (Loc, 2 ** Len_Bits - 1);
1174
               Set_Print_In_Hex (Lit);
1175
 
1176
               Decl :=
1177
                 Make_Subtype_Declaration (Loc,
1178
                   Defining_Identifier => PAT,
1179
                     Subtype_Indication =>
1180
                       Make_Subtype_Indication (Loc,
1181
                         Subtype_Mark => New_Occurrence_Of (Btyp, Loc),
1182
 
1183
                         Constraint =>
1184
                           Make_Range_Constraint (Loc,
1185
                             Range_Expression =>
1186
                               Make_Range (Loc,
1187
                                 Low_Bound =>
1188
                                   Make_Integer_Literal (Loc, 0),
1189
                                 High_Bound => Lit))));
1190
 
1191
               if PASize = Uint_0 then
1192
                  PASize := Len_Bits;
1193
               end if;
1194
 
1195
               Install_PAT;
1196
 
1197
               --  Propagate a given alignment to the modular type. This can
1198
               --  cause it to be under-aligned, but that's OK.
1199
 
1200
               if Present (Alignment_Clause (Typ)) then
1201
                  Set_Alignment (PAT, Alignment (Typ));
1202
               end if;
1203
 
1204
               return;
1205
            end if;
1206
         end if;
1207
 
1208
         --  Could not use a modular type, for all other cases, we build
1209
         --  a packed array subtype:
1210
 
1211
         --    subtype tttPn is
1212
         --      System.Packed_Bytes{1,2,4} (0 .. (Bits + 7) / 8 - 1);
1213
 
1214
         --  Bits is the length of the array in bits
1215
 
1216
         Set_PB_Type;
1217
 
1218
         Bits_U1 :=
1219
           Make_Op_Add (Loc,
1220
             Left_Opnd =>
1221
               Make_Op_Multiply (Loc,
1222
                 Left_Opnd  =>
1223
                   Make_Integer_Literal (Loc, Csize),
1224
                 Right_Opnd => Len_Expr),
1225
 
1226
             Right_Opnd =>
1227
               Make_Integer_Literal (Loc, 7));
1228
 
1229
         Set_Paren_Count (Bits_U1, 1);
1230
 
1231
         PAT_High :=
1232
           Make_Op_Subtract (Loc,
1233
             Left_Opnd =>
1234
               Make_Op_Divide (Loc,
1235
                 Left_Opnd => Bits_U1,
1236
                 Right_Opnd => Make_Integer_Literal (Loc, 8)),
1237
             Right_Opnd => Make_Integer_Literal (Loc, 1));
1238
 
1239
         Decl :=
1240
           Make_Subtype_Declaration (Loc,
1241
             Defining_Identifier => PAT,
1242
               Subtype_Indication =>
1243
                 Make_Subtype_Indication (Loc,
1244
                   Subtype_Mark => New_Occurrence_Of (PB_Type, Loc),
1245
                   Constraint =>
1246
                     Make_Index_Or_Discriminant_Constraint (Loc,
1247
                       Constraints => New_List (
1248
                         Make_Range (Loc,
1249
                           Low_Bound =>
1250
                             Make_Integer_Literal (Loc, 0),
1251
                           High_Bound =>
1252
                             Convert_To (Standard_Integer, PAT_High))))));
1253
 
1254
         Install_PAT;
1255
 
1256
         --  Currently the code in this unit requires that packed arrays
1257
         --  represented by non-modular arrays of bytes be on a byte
1258
         --  boundary for bit sizes handled by System.Pack_nn units.
1259
         --  That's because these units assume the array being accessed
1260
         --  starts on a byte boundary.
1261
 
1262
         if Get_Id (UI_To_Int (Csize)) /= RE_Null then
1263
            Set_Must_Be_On_Byte_Boundary (Typ);
1264
         end if;
1265
      end if;
1266
   end Create_Packed_Array_Type;
1267
 
1268
   -----------------------------------
1269
   -- Expand_Bit_Packed_Element_Set --
1270
   -----------------------------------
1271
 
1272
   procedure Expand_Bit_Packed_Element_Set (N : Node_Id) is
1273
      Loc : constant Source_Ptr := Sloc (N);
1274
      Lhs : constant Node_Id    := Name (N);
1275
 
1276
      Ass_OK : constant Boolean := Assignment_OK (Lhs);
1277
      --  Used to preserve assignment OK status when assignment is rewritten
1278
 
1279
      Rhs : Node_Id := Expression (N);
1280
      --  Initially Rhs is the right hand side value, it will be replaced
1281
      --  later by an appropriate unchecked conversion for the assignment.
1282
 
1283
      Obj    : Node_Id;
1284
      Atyp   : Entity_Id;
1285
      PAT    : Entity_Id;
1286
      Ctyp   : Entity_Id;
1287
      Csiz   : Int;
1288
      Cmask  : Uint;
1289
 
1290
      Shift : Node_Id;
1291
      --  The expression for the shift value that is required
1292
 
1293
      Shift_Used : Boolean := False;
1294
      --  Set True if Shift has been used in the generated code at least
1295
      --  once, so that it must be duplicated if used again
1296
 
1297
      New_Lhs : Node_Id;
1298
      New_Rhs : Node_Id;
1299
 
1300
      Rhs_Val_Known : Boolean;
1301
      Rhs_Val       : Uint;
1302
      --  If the value of the right hand side as an integer constant is
1303
      --  known at compile time, Rhs_Val_Known is set True, and Rhs_Val
1304
      --  contains the value. Otherwise Rhs_Val_Known is set False, and
1305
      --  the Rhs_Val is undefined.
1306
 
1307
      function Get_Shift return Node_Id;
1308
      --  Function used to get the value of Shift, making sure that it
1309
      --  gets duplicated if the function is called more than once.
1310
 
1311
      ---------------
1312
      -- Get_Shift --
1313
      ---------------
1314
 
1315
      function Get_Shift return Node_Id is
1316
      begin
1317
         --  If we used the shift value already, then duplicate it. We
1318
         --  set a temporary parent in case actions have to be inserted.
1319
 
1320
         if Shift_Used then
1321
            Set_Parent (Shift, N);
1322
            return Duplicate_Subexpr_No_Checks (Shift);
1323
 
1324
         --  If first time, use Shift unchanged, and set flag for first use
1325
 
1326
         else
1327
            Shift_Used := True;
1328
            return Shift;
1329
         end if;
1330
      end Get_Shift;
1331
 
1332
   --  Start of processing for Expand_Bit_Packed_Element_Set
1333
 
1334
   begin
1335
      pragma Assert (Is_Bit_Packed_Array (Etype (Prefix (Lhs))));
1336
 
1337
      Obj := Relocate_Node (Prefix (Lhs));
1338
      Convert_To_Actual_Subtype (Obj);
1339
      Atyp := Etype (Obj);
1340
      PAT  := Packed_Array_Type (Atyp);
1341
      Ctyp := Component_Type (Atyp);
1342
      Csiz := UI_To_Int (Component_Size (Atyp));
1343
 
1344
      --  We remove side effects, in case the rhs modifies the lhs, because we
1345
      --  are about to transform the rhs into an expression that first READS
1346
      --  the lhs, so we can do the necessary shifting and masking. Example:
1347
      --  "X(2) := F(...);" where F modifies X(3). Otherwise, the side effect
1348
      --  will be lost.
1349
 
1350
      Remove_Side_Effects (Rhs);
1351
 
1352
      --  We convert the right hand side to the proper subtype to ensure
1353
      --  that an appropriate range check is made (since the normal range
1354
      --  check from assignment will be lost in the transformations). This
1355
      --  conversion is analyzed immediately so that subsequent processing
1356
      --  can work with an analyzed Rhs (and e.g. look at its Etype)
1357
 
1358
      --  If the right-hand side is a string literal, create a temporary for
1359
      --  it, constant-folding is not ready to wrap the bit representation
1360
      --  of a string literal.
1361
 
1362
      if Nkind (Rhs) = N_String_Literal then
1363
         declare
1364
            Decl : Node_Id;
1365
         begin
1366
            Decl :=
1367
              Make_Object_Declaration (Loc,
1368
                Defining_Identifier => Make_Temporary (Loc, 'T', Rhs),
1369
                Object_Definition   => New_Occurrence_Of (Ctyp, Loc),
1370
                Expression          => New_Copy_Tree (Rhs));
1371
 
1372
            Insert_Actions (N, New_List (Decl));
1373
            Rhs := New_Occurrence_Of (Defining_Identifier (Decl), Loc);
1374
         end;
1375
      end if;
1376
 
1377
      Rhs := Convert_To (Ctyp, Rhs);
1378
      Set_Parent (Rhs, N);
1379
 
1380
      --  If we are building the initialization procedure for a packed array,
1381
      --  and Initialize_Scalars is enabled, each component assignment is an
1382
      --  out-of-range value by design.  Compile this value without checks,
1383
      --  because a call to the array init_proc must not raise an exception.
1384
 
1385
      if Within_Init_Proc
1386
        and then Initialize_Scalars
1387
      then
1388
         Analyze_And_Resolve (Rhs, Ctyp, Suppress => All_Checks);
1389
      else
1390
         Analyze_And_Resolve (Rhs, Ctyp);
1391
      end if;
1392
 
1393
      --  For the AAMP target, indexing of certain packed array is passed
1394
      --  through to the back end without expansion, because the expansion
1395
      --  results in very inefficient code on that target. This allows the
1396
      --  GNAAMP back end to generate specialized macros that support more
1397
      --  efficient indexing of packed arrays with components having sizes
1398
      --  that are small powers of two.
1399
 
1400
      if AAMP_On_Target
1401
        and then (Csiz = 1 or else Csiz = 2 or else Csiz = 4)
1402
      then
1403
         return;
1404
      end if;
1405
 
1406
      --  Case of component size 1,2,4 or any component size for the modular
1407
      --  case. These are the cases for which we can inline the code.
1408
 
1409
      if Csiz = 1 or else Csiz = 2 or else Csiz = 4
1410
        or else (Present (PAT) and then Is_Modular_Integer_Type (PAT))
1411
      then
1412
         Setup_Inline_Packed_Array_Reference (Lhs, Atyp, Obj, Cmask, Shift);
1413
 
1414
         --  The statement to be generated is:
1415
 
1416
         --    Obj := atyp!((Obj and Mask1) or (shift_left (rhs, Shift)))
1417
 
1418
         --      where Mask1 is obtained by shifting Cmask left Shift bits
1419
         --      and then complementing the result.
1420
 
1421
         --      the "and Mask1" is omitted if rhs is constant and all 1 bits
1422
 
1423
         --      the "or ..." is omitted if rhs is constant and all 0 bits
1424
 
1425
         --      rhs is converted to the appropriate type
1426
 
1427
         --      The result is converted back to the array type, since
1428
         --      otherwise we lose knowledge of the packed nature.
1429
 
1430
         --  Determine if right side is all 0 bits or all 1 bits
1431
 
1432
         if Compile_Time_Known_Value (Rhs) then
1433
            Rhs_Val       := Expr_Rep_Value (Rhs);
1434
            Rhs_Val_Known := True;
1435
 
1436
         --  The following test catches the case of an unchecked conversion
1437
         --  of an integer literal. This results from optimizing aggregates
1438
         --  of packed types.
1439
 
1440
         elsif Nkind (Rhs) = N_Unchecked_Type_Conversion
1441
           and then Compile_Time_Known_Value (Expression (Rhs))
1442
         then
1443
            Rhs_Val       := Expr_Rep_Value (Expression (Rhs));
1444
            Rhs_Val_Known := True;
1445
 
1446
         else
1447
            Rhs_Val       := No_Uint;
1448
            Rhs_Val_Known := False;
1449
         end if;
1450
 
1451
         --  Some special checks for the case where the right hand value is
1452
         --  known at compile time. Basically we have to take care of the
1453
         --  implicit conversion to the subtype of the component object.
1454
 
1455
         if Rhs_Val_Known then
1456
 
1457
            --  If we have a biased component type then we must manually do the
1458
            --  biasing, since we are taking responsibility in this case for
1459
            --  constructing the exact bit pattern to be used.
1460
 
1461
            if Has_Biased_Representation (Ctyp) then
1462
               Rhs_Val := Rhs_Val - Expr_Rep_Value (Type_Low_Bound (Ctyp));
1463
            end if;
1464
 
1465
            --  For a negative value, we manually convert the two's complement
1466
            --  value to a corresponding unsigned value, so that the proper
1467
            --  field width is maintained. If we did not do this, we would
1468
            --  get too many leading sign bits later on.
1469
 
1470
            if Rhs_Val < 0 then
1471
               Rhs_Val := 2 ** UI_From_Int (Csiz) + Rhs_Val;
1472
            end if;
1473
         end if;
1474
 
1475
         --  Now create copies removing side effects. Note that in some
1476
         --  complex cases, this may cause the fact that we have already
1477
         --  set a packed array type on Obj to get lost. So we save the
1478
         --  type of Obj, and make sure it is reset properly.
1479
 
1480
         declare
1481
            T : constant Entity_Id := Etype (Obj);
1482
         begin
1483
            New_Lhs := Duplicate_Subexpr (Obj, True);
1484
            New_Rhs := Duplicate_Subexpr_No_Checks (Obj);
1485
            Set_Etype (Obj, T);
1486
            Set_Etype (New_Lhs, T);
1487
            Set_Etype (New_Rhs, T);
1488
         end;
1489
 
1490
         --  First we deal with the "and"
1491
 
1492
         if not Rhs_Val_Known or else Rhs_Val /= Cmask then
1493
            declare
1494
               Mask1 : Node_Id;
1495
               Lit   : Node_Id;
1496
 
1497
            begin
1498
               if Compile_Time_Known_Value (Shift) then
1499
                  Mask1 :=
1500
                    Make_Integer_Literal (Loc,
1501
                      Modulus (Etype (Obj)) - 1 -
1502
                                 (Cmask * (2 ** Expr_Value (Get_Shift))));
1503
                  Set_Print_In_Hex (Mask1);
1504
 
1505
               else
1506
                  Lit := Make_Integer_Literal (Loc, Cmask);
1507
                  Set_Print_In_Hex (Lit);
1508
                  Mask1 :=
1509
                    Make_Op_Not (Loc,
1510
                      Right_Opnd => Make_Shift_Left (Lit, Get_Shift));
1511
               end if;
1512
 
1513
               New_Rhs :=
1514
                 Make_Op_And (Loc,
1515
                   Left_Opnd  => New_Rhs,
1516
                   Right_Opnd => Mask1);
1517
            end;
1518
         end if;
1519
 
1520
         --  Then deal with the "or"
1521
 
1522
         if not Rhs_Val_Known or else Rhs_Val /= 0 then
1523
            declare
1524
               Or_Rhs : Node_Id;
1525
 
1526
               procedure Fixup_Rhs;
1527
               --  Adjust Rhs by bias if biased representation for components
1528
               --  or remove extraneous high order sign bits if signed.
1529
 
1530
               procedure Fixup_Rhs is
1531
                  Etyp : constant Entity_Id := Etype (Rhs);
1532
 
1533
               begin
1534
                  --  For biased case, do the required biasing by simply
1535
                  --  converting to the biased subtype (the conversion
1536
                  --  will generate the required bias).
1537
 
1538
                  if Has_Biased_Representation (Ctyp) then
1539
                     Rhs := Convert_To (Ctyp, Rhs);
1540
 
1541
                  --  For a signed integer type that is not biased, generate
1542
                  --  a conversion to unsigned to strip high order sign bits.
1543
 
1544
                  elsif Is_Signed_Integer_Type (Ctyp) then
1545
                     Rhs := Unchecked_Convert_To (RTE (Bits_Id (Csiz)), Rhs);
1546
                  end if;
1547
 
1548
                  --  Set Etype, since it can be referenced before the node is
1549
                  --  completely analyzed.
1550
 
1551
                  Set_Etype (Rhs, Etyp);
1552
 
1553
                  --  We now need to do an unchecked conversion of the
1554
                  --  result to the target type, but it is important that
1555
                  --  this conversion be a right justified conversion and
1556
                  --  not a left justified conversion.
1557
 
1558
                  Rhs := RJ_Unchecked_Convert_To (Etype (Obj), Rhs);
1559
 
1560
               end Fixup_Rhs;
1561
 
1562
            begin
1563
               if Rhs_Val_Known
1564
                 and then Compile_Time_Known_Value (Get_Shift)
1565
               then
1566
                  Or_Rhs :=
1567
                    Make_Integer_Literal (Loc,
1568
                      Rhs_Val * (2 ** Expr_Value (Get_Shift)));
1569
                  Set_Print_In_Hex (Or_Rhs);
1570
 
1571
               else
1572
                  --  We have to convert the right hand side to Etype (Obj).
1573
                  --  A special case arises if what we have now is a Val
1574
                  --  attribute reference whose expression type is Etype (Obj).
1575
                  --  This happens for assignments of fields from the same
1576
                  --  array. In this case we get the required right hand side
1577
                  --  by simply removing the inner attribute reference.
1578
 
1579
                  if Nkind (Rhs) = N_Attribute_Reference
1580
                    and then Attribute_Name (Rhs) = Name_Val
1581
                    and then Etype (First (Expressions (Rhs))) = Etype (Obj)
1582
                  then
1583
                     Rhs := Relocate_Node (First (Expressions (Rhs)));
1584
                     Fixup_Rhs;
1585
 
1586
                  --  If the value of the right hand side is a known integer
1587
                  --  value, then just replace it by an untyped constant,
1588
                  --  which will be properly retyped when we analyze and
1589
                  --  resolve the expression.
1590
 
1591
                  elsif Rhs_Val_Known then
1592
 
1593
                     --  Note that Rhs_Val has already been normalized to
1594
                     --  be an unsigned value with the proper number of bits.
1595
 
1596
                     Rhs :=
1597
                       Make_Integer_Literal (Loc, Rhs_Val);
1598
 
1599
                  --  Otherwise we need an unchecked conversion
1600
 
1601
                  else
1602
                     Fixup_Rhs;
1603
                  end if;
1604
 
1605
                  Or_Rhs := Make_Shift_Left (Rhs, Get_Shift);
1606
               end if;
1607
 
1608
               if Nkind (New_Rhs) = N_Op_And then
1609
                  Set_Paren_Count (New_Rhs, 1);
1610
               end if;
1611
 
1612
               New_Rhs :=
1613
                 Make_Op_Or (Loc,
1614
                   Left_Opnd  => New_Rhs,
1615
                   Right_Opnd => Or_Rhs);
1616
            end;
1617
         end if;
1618
 
1619
         --  Now do the rewrite
1620
 
1621
         Rewrite (N,
1622
           Make_Assignment_Statement (Loc,
1623
             Name       => New_Lhs,
1624
             Expression =>
1625
               Unchecked_Convert_To (Etype (New_Lhs), New_Rhs)));
1626
         Set_Assignment_OK (Name (N), Ass_OK);
1627
 
1628
      --  All other component sizes for non-modular case
1629
 
1630
      else
1631
         --  We generate
1632
 
1633
         --    Set_nn (Arr'address, Subscr, Bits_nn!(Rhs))
1634
 
1635
         --  where Subscr is the computed linear subscript
1636
 
1637
         declare
1638
            Bits_nn : constant Entity_Id := RTE (Bits_Id (Csiz));
1639
            Set_nn  : Entity_Id;
1640
            Subscr  : Node_Id;
1641
            Atyp    : Entity_Id;
1642
 
1643
         begin
1644
            if No (Bits_nn) then
1645
 
1646
               --  Error, most likely High_Integrity_Mode restriction
1647
 
1648
               return;
1649
            end if;
1650
 
1651
            --  Acquire proper Set entity. We use the aligned or unaligned
1652
            --  case as appropriate.
1653
 
1654
            if Known_Aligned_Enough (Obj, Csiz) then
1655
               Set_nn := RTE (Set_Id (Csiz));
1656
            else
1657
               Set_nn := RTE (SetU_Id (Csiz));
1658
            end if;
1659
 
1660
            --  Now generate the set reference
1661
 
1662
            Obj := Relocate_Node (Prefix (Lhs));
1663
            Convert_To_Actual_Subtype (Obj);
1664
            Atyp := Etype (Obj);
1665
            Compute_Linear_Subscript (Atyp, Lhs, Subscr);
1666
 
1667
            --  Below we must make the assumption that Obj is
1668
            --  at least byte aligned, since otherwise its address
1669
            --  cannot be taken. The assumption holds since the
1670
            --  only arrays that can be misaligned are small packed
1671
            --  arrays which are implemented as a modular type, and
1672
            --  that is not the case here.
1673
 
1674
            Rewrite (N,
1675
              Make_Procedure_Call_Statement (Loc,
1676
                  Name => New_Occurrence_Of (Set_nn, Loc),
1677
                  Parameter_Associations => New_List (
1678
                    Make_Attribute_Reference (Loc,
1679
                      Prefix         => Obj,
1680
                      Attribute_Name => Name_Address),
1681
                    Subscr,
1682
                    Unchecked_Convert_To (Bits_nn,
1683
                      Convert_To (Ctyp, Rhs)))));
1684
 
1685
         end;
1686
      end if;
1687
 
1688
      Analyze (N, Suppress => All_Checks);
1689
   end Expand_Bit_Packed_Element_Set;
1690
 
1691
   -------------------------------------
1692
   -- Expand_Packed_Address_Reference --
1693
   -------------------------------------
1694
 
1695
   procedure Expand_Packed_Address_Reference (N : Node_Id) is
1696
      Loc    : constant Source_Ptr := Sloc (N);
1697
      Base   : Node_Id;
1698
      Offset : Node_Id;
1699
 
1700
   begin
1701
      --  We build an expression that has the form
1702
 
1703
      --    outer_object'Address
1704
      --      + (linear-subscript * component_size  for each array reference
1705
      --      +  field'Bit_Position                 for each record field
1706
      --      +  ...
1707
      --      +  ...) / Storage_Unit;
1708
 
1709
      Get_Base_And_Bit_Offset (Prefix (N), Base, Offset);
1710
 
1711
      Rewrite (N,
1712
        Unchecked_Convert_To (RTE (RE_Address),
1713
          Make_Op_Add (Loc,
1714
            Left_Opnd =>
1715
              Unchecked_Convert_To (RTE (RE_Integer_Address),
1716
                Make_Attribute_Reference (Loc,
1717
                  Prefix         => Base,
1718
                  Attribute_Name => Name_Address)),
1719
 
1720
            Right_Opnd =>
1721
              Unchecked_Convert_To (RTE (RE_Integer_Address),
1722
                Make_Op_Divide (Loc,
1723
                  Left_Opnd => Offset,
1724
                  Right_Opnd =>
1725
                    Make_Integer_Literal (Loc, System_Storage_Unit))))));
1726
 
1727
      Analyze_And_Resolve (N, RTE (RE_Address));
1728
   end Expand_Packed_Address_Reference;
1729
 
1730
   ---------------------------------
1731
   -- Expand_Packed_Bit_Reference --
1732
   ---------------------------------
1733
 
1734
   procedure Expand_Packed_Bit_Reference (N : Node_Id) is
1735
      Loc    : constant Source_Ptr := Sloc (N);
1736
      Base   : Node_Id;
1737
      Offset : Node_Id;
1738
 
1739
   begin
1740
      --  We build an expression that has the form
1741
 
1742
      --    (linear-subscript * component_size      for each array reference
1743
      --      +  field'Bit_Position                 for each record field
1744
      --      +  ...
1745
      --      +  ...) mod Storage_Unit;
1746
 
1747
      Get_Base_And_Bit_Offset (Prefix (N), Base, Offset);
1748
 
1749
      Rewrite (N,
1750
        Unchecked_Convert_To (Universal_Integer,
1751
          Make_Op_Mod (Loc,
1752
            Left_Opnd => Offset,
1753
            Right_Opnd => Make_Integer_Literal (Loc, System_Storage_Unit))));
1754
 
1755
      Analyze_And_Resolve (N, Universal_Integer);
1756
   end Expand_Packed_Bit_Reference;
1757
 
1758
   ------------------------------------
1759
   -- Expand_Packed_Boolean_Operator --
1760
   ------------------------------------
1761
 
1762
   --  This routine expands "a op b" for the packed cases
1763
 
1764
   procedure Expand_Packed_Boolean_Operator (N : Node_Id) is
1765
      Loc : constant Source_Ptr := Sloc (N);
1766
      Typ : constant Entity_Id  := Etype (N);
1767
      L   : constant Node_Id    := Relocate_Node (Left_Opnd  (N));
1768
      R   : constant Node_Id    := Relocate_Node (Right_Opnd (N));
1769
 
1770
      Ltyp : Entity_Id;
1771
      Rtyp : Entity_Id;
1772
      PAT  : Entity_Id;
1773
 
1774
   begin
1775
      Convert_To_Actual_Subtype (L);
1776
      Convert_To_Actual_Subtype (R);
1777
 
1778
      Ensure_Defined (Etype (L), N);
1779
      Ensure_Defined (Etype (R), N);
1780
 
1781
      Apply_Length_Check (R, Etype (L));
1782
 
1783
      Ltyp := Etype (L);
1784
      Rtyp := Etype (R);
1785
 
1786
      --  Deal with silly case of XOR where the subcomponent has a range
1787
      --  True .. True where an exception must be raised.
1788
 
1789
      if Nkind (N) = N_Op_Xor then
1790
         Silly_Boolean_Array_Xor_Test (N, Rtyp);
1791
      end if;
1792
 
1793
      --  Now that that silliness is taken care of, get packed array type
1794
 
1795
      Convert_To_PAT_Type (L);
1796
      Convert_To_PAT_Type (R);
1797
 
1798
      PAT := Etype (L);
1799
 
1800
      --  For the modular case, we expand a op b into
1801
 
1802
      --    rtyp!(pat!(a) op pat!(b))
1803
 
1804
      --  where rtyp is the Etype of the left operand. Note that we do not
1805
      --  convert to the base type, since this would be unconstrained, and
1806
      --  hence not have a corresponding packed array type set.
1807
 
1808
      --  Note that both operands must be modular for this code to be used
1809
 
1810
      if Is_Modular_Integer_Type (PAT)
1811
           and then
1812
         Is_Modular_Integer_Type (Etype (R))
1813
      then
1814
         declare
1815
            P : Node_Id;
1816
 
1817
         begin
1818
            if Nkind (N) = N_Op_And then
1819
               P := Make_Op_And (Loc, L, R);
1820
 
1821
            elsif Nkind (N) = N_Op_Or then
1822
               P := Make_Op_Or  (Loc, L, R);
1823
 
1824
            else -- Nkind (N) = N_Op_Xor
1825
               P := Make_Op_Xor (Loc, L, R);
1826
            end if;
1827
 
1828
            Rewrite (N, Unchecked_Convert_To (Ltyp, P));
1829
         end;
1830
 
1831
      --  For the array case, we insert the actions
1832
 
1833
      --    Result : Ltype;
1834
 
1835
      --    System.Bit_Ops.Bit_And/Or/Xor
1836
      --     (Left'Address,
1837
      --      Ltype'Length * Ltype'Component_Size;
1838
      --      Right'Address,
1839
      --      Rtype'Length * Rtype'Component_Size
1840
      --      Result'Address);
1841
 
1842
      --  where Left and Right are the Packed_Bytes{1,2,4} operands and
1843
      --  the second argument and fourth arguments are the lengths of the
1844
      --  operands in bits. Then we replace the expression by a reference
1845
      --  to Result.
1846
 
1847
      --  Note that if we are mixing a modular and array operand, everything
1848
      --  works fine, since we ensure that the modular representation has the
1849
      --  same physical layout as the array representation (that's what the
1850
      --  left justified modular stuff in the big-endian case is about).
1851
 
1852
      else
1853
         declare
1854
            Result_Ent : constant Entity_Id := Make_Temporary (Loc, 'T');
1855
            E_Id       : RE_Id;
1856
 
1857
         begin
1858
            if Nkind (N) = N_Op_And then
1859
               E_Id := RE_Bit_And;
1860
 
1861
            elsif Nkind (N) = N_Op_Or then
1862
               E_Id := RE_Bit_Or;
1863
 
1864
            else -- Nkind (N) = N_Op_Xor
1865
               E_Id := RE_Bit_Xor;
1866
            end if;
1867
 
1868
            Insert_Actions (N, New_List (
1869
 
1870
              Make_Object_Declaration (Loc,
1871
                Defining_Identifier => Result_Ent,
1872
                Object_Definition => New_Occurrence_Of (Ltyp, Loc)),
1873
 
1874
              Make_Procedure_Call_Statement (Loc,
1875
                Name => New_Occurrence_Of (RTE (E_Id), Loc),
1876
                  Parameter_Associations => New_List (
1877
 
1878
                    Make_Byte_Aligned_Attribute_Reference (Loc,
1879
                      Prefix         => L,
1880
                      Attribute_Name => Name_Address),
1881
 
1882
                    Make_Op_Multiply (Loc,
1883
                      Left_Opnd =>
1884
                        Make_Attribute_Reference (Loc,
1885
                          Prefix         =>
1886
                            New_Occurrence_Of
1887
                              (Etype (First_Index (Ltyp)), Loc),
1888
                          Attribute_Name => Name_Range_Length),
1889
 
1890
                      Right_Opnd =>
1891
                        Make_Integer_Literal (Loc, Component_Size (Ltyp))),
1892
 
1893
                    Make_Byte_Aligned_Attribute_Reference (Loc,
1894
                      Prefix         => R,
1895
                      Attribute_Name => Name_Address),
1896
 
1897
                    Make_Op_Multiply (Loc,
1898
                      Left_Opnd =>
1899
                        Make_Attribute_Reference (Loc,
1900
                          Prefix         =>
1901
                            New_Occurrence_Of
1902
                              (Etype (First_Index (Rtyp)), Loc),
1903
                          Attribute_Name => Name_Range_Length),
1904
 
1905
                      Right_Opnd =>
1906
                        Make_Integer_Literal (Loc, Component_Size (Rtyp))),
1907
 
1908
                    Make_Byte_Aligned_Attribute_Reference (Loc,
1909
                      Prefix => New_Occurrence_Of (Result_Ent, Loc),
1910
                      Attribute_Name => Name_Address)))));
1911
 
1912
            Rewrite (N,
1913
              New_Occurrence_Of (Result_Ent, Loc));
1914
         end;
1915
      end if;
1916
 
1917
      Analyze_And_Resolve (N, Typ, Suppress => All_Checks);
1918
   end Expand_Packed_Boolean_Operator;
1919
 
1920
   -------------------------------------
1921
   -- Expand_Packed_Element_Reference --
1922
   -------------------------------------
1923
 
1924
   procedure Expand_Packed_Element_Reference (N : Node_Id) is
1925
      Loc   : constant Source_Ptr := Sloc (N);
1926
      Obj   : Node_Id;
1927
      Atyp  : Entity_Id;
1928
      PAT   : Entity_Id;
1929
      Ctyp  : Entity_Id;
1930
      Csiz  : Int;
1931
      Shift : Node_Id;
1932
      Cmask : Uint;
1933
      Lit   : Node_Id;
1934
      Arg   : Node_Id;
1935
 
1936
   begin
1937
      --  If not bit packed, we have the enumeration case, which is easily
1938
      --  dealt with (just adjust the subscripts of the indexed component)
1939
 
1940
      --  Note: this leaves the result as an indexed component, which is
1941
      --  still a variable, so can be used in the assignment case, as is
1942
      --  required in the enumeration case.
1943
 
1944
      if not Is_Bit_Packed_Array (Etype (Prefix (N))) then
1945
         Setup_Enumeration_Packed_Array_Reference (N);
1946
         return;
1947
      end if;
1948
 
1949
      --  Remaining processing is for the bit-packed case
1950
 
1951
      Obj := Relocate_Node (Prefix (N));
1952
      Convert_To_Actual_Subtype (Obj);
1953
      Atyp := Etype (Obj);
1954
      PAT  := Packed_Array_Type (Atyp);
1955
      Ctyp := Component_Type (Atyp);
1956
      Csiz := UI_To_Int (Component_Size (Atyp));
1957
 
1958
      --  For the AAMP target, indexing of certain packed array is passed
1959
      --  through to the back end without expansion, because the expansion
1960
      --  results in very inefficient code on that target. This allows the
1961
      --  GNAAMP back end to generate specialized macros that support more
1962
      --  efficient indexing of packed arrays with components having sizes
1963
      --  that are small powers of two.
1964
 
1965
      if AAMP_On_Target
1966
        and then (Csiz = 1 or else Csiz = 2 or else Csiz = 4)
1967
      then
1968
         return;
1969
      end if;
1970
 
1971
      --  Case of component size 1,2,4 or any component size for the modular
1972
      --  case. These are the cases for which we can inline the code.
1973
 
1974
      if Csiz = 1 or else Csiz = 2 or else Csiz = 4
1975
        or else (Present (PAT) and then Is_Modular_Integer_Type (PAT))
1976
      then
1977
         Setup_Inline_Packed_Array_Reference (N, Atyp, Obj, Cmask, Shift);
1978
         Lit := Make_Integer_Literal (Loc, Cmask);
1979
         Set_Print_In_Hex (Lit);
1980
 
1981
         --  We generate a shift right to position the field, followed by a
1982
         --  masking operation to extract the bit field, and we finally do an
1983
         --  unchecked conversion to convert the result to the required target.
1984
 
1985
         --  Note that the unchecked conversion automatically deals with the
1986
         --  bias if we are dealing with a biased representation. What will
1987
         --  happen is that we temporarily generate the biased representation,
1988
         --  but almost immediately that will be converted to the original
1989
         --  unbiased component type, and the bias will disappear.
1990
 
1991
         Arg :=
1992
           Make_Op_And (Loc,
1993
             Left_Opnd  => Make_Shift_Right (Obj, Shift),
1994
             Right_Opnd => Lit);
1995
 
1996
         --  We needed to analyze this before we do the unchecked convert
1997
         --  below, but we need it temporarily attached to the tree for
1998
         --  this analysis (hence the temporary Set_Parent call).
1999
 
2000
         Set_Parent (Arg, Parent (N));
2001
         Analyze_And_Resolve (Arg);
2002
 
2003
         Rewrite (N, RJ_Unchecked_Convert_To (Ctyp, Arg));
2004
 
2005
      --  All other component sizes for non-modular case
2006
 
2007
      else
2008
         --  We generate
2009
 
2010
         --    Component_Type!(Get_nn (Arr'address, Subscr))
2011
 
2012
         --  where Subscr is the computed linear subscript
2013
 
2014
         declare
2015
            Get_nn : Entity_Id;
2016
            Subscr : Node_Id;
2017
 
2018
         begin
2019
            --  Acquire proper Get entity. We use the aligned or unaligned
2020
            --  case as appropriate.
2021
 
2022
            if Known_Aligned_Enough (Obj, Csiz) then
2023
               Get_nn := RTE (Get_Id (Csiz));
2024
            else
2025
               Get_nn := RTE (GetU_Id (Csiz));
2026
            end if;
2027
 
2028
            --  Now generate the get reference
2029
 
2030
            Compute_Linear_Subscript (Atyp, N, Subscr);
2031
 
2032
            --  Below we make the assumption that Obj is at least byte
2033
            --  aligned, since otherwise its address cannot be taken.
2034
            --  The assumption holds since the only arrays that can be
2035
            --  misaligned are small packed arrays which are implemented
2036
            --  as a modular type, and that is not the case here.
2037
 
2038
            Rewrite (N,
2039
              Unchecked_Convert_To (Ctyp,
2040
                Make_Function_Call (Loc,
2041
                  Name => New_Occurrence_Of (Get_nn, Loc),
2042
                  Parameter_Associations => New_List (
2043
                    Make_Attribute_Reference (Loc,
2044
                      Prefix         => Obj,
2045
                      Attribute_Name => Name_Address),
2046
                    Subscr))));
2047
         end;
2048
      end if;
2049
 
2050
      Analyze_And_Resolve (N, Ctyp, Suppress => All_Checks);
2051
 
2052
   end Expand_Packed_Element_Reference;
2053
 
2054
   ----------------------
2055
   -- Expand_Packed_Eq --
2056
   ----------------------
2057
 
2058
   --  Handles expansion of "=" on packed array types
2059
 
2060
   procedure Expand_Packed_Eq (N : Node_Id) is
2061
      Loc : constant Source_Ptr := Sloc (N);
2062
      L   : constant Node_Id    := Relocate_Node (Left_Opnd  (N));
2063
      R   : constant Node_Id    := Relocate_Node (Right_Opnd (N));
2064
 
2065
      LLexpr : Node_Id;
2066
      RLexpr : Node_Id;
2067
 
2068
      Ltyp : Entity_Id;
2069
      Rtyp : Entity_Id;
2070
      PAT  : Entity_Id;
2071
 
2072
   begin
2073
      Convert_To_Actual_Subtype (L);
2074
      Convert_To_Actual_Subtype (R);
2075
      Ltyp := Underlying_Type (Etype (L));
2076
      Rtyp := Underlying_Type (Etype (R));
2077
 
2078
      Convert_To_PAT_Type (L);
2079
      Convert_To_PAT_Type (R);
2080
      PAT := Etype (L);
2081
 
2082
      LLexpr :=
2083
        Make_Op_Multiply (Loc,
2084
          Left_Opnd =>
2085
            Make_Attribute_Reference (Loc,
2086
              Prefix         => New_Occurrence_Of (Ltyp, Loc),
2087
              Attribute_Name => Name_Length),
2088
          Right_Opnd =>
2089
            Make_Integer_Literal (Loc, Component_Size (Ltyp)));
2090
 
2091
      RLexpr :=
2092
        Make_Op_Multiply (Loc,
2093
          Left_Opnd =>
2094
            Make_Attribute_Reference (Loc,
2095
              Prefix         => New_Occurrence_Of (Rtyp, Loc),
2096
              Attribute_Name => Name_Length),
2097
          Right_Opnd =>
2098
            Make_Integer_Literal (Loc, Component_Size (Rtyp)));
2099
 
2100
      --  For the modular case, we transform the comparison to:
2101
 
2102
      --    Ltyp'Length = Rtyp'Length and then PAT!(L) = PAT!(R)
2103
 
2104
      --  where PAT is the packed array type. This works fine, since in the
2105
      --  modular case we guarantee that the unused bits are always zeroes.
2106
      --  We do have to compare the lengths because we could be comparing
2107
      --  two different subtypes of the same base type.
2108
 
2109
      if Is_Modular_Integer_Type (PAT) then
2110
         Rewrite (N,
2111
           Make_And_Then (Loc,
2112
             Left_Opnd =>
2113
               Make_Op_Eq (Loc,
2114
                 Left_Opnd  => LLexpr,
2115
                 Right_Opnd => RLexpr),
2116
 
2117
             Right_Opnd =>
2118
               Make_Op_Eq (Loc,
2119
                 Left_Opnd => L,
2120
                 Right_Opnd => R)));
2121
 
2122
      --  For the non-modular case, we call a runtime routine
2123
 
2124
      --    System.Bit_Ops.Bit_Eq
2125
      --      (L'Address, L_Length, R'Address, R_Length)
2126
 
2127
      --  where PAT is the packed array type, and the lengths are the lengths
2128
      --  in bits of the original packed arrays. This routine takes care of
2129
      --  not comparing the unused bits in the last byte.
2130
 
2131
      else
2132
         Rewrite (N,
2133
           Make_Function_Call (Loc,
2134
             Name => New_Occurrence_Of (RTE (RE_Bit_Eq), Loc),
2135
             Parameter_Associations => New_List (
2136
               Make_Byte_Aligned_Attribute_Reference (Loc,
2137
                 Prefix         => L,
2138
                 Attribute_Name => Name_Address),
2139
 
2140
               LLexpr,
2141
 
2142
               Make_Byte_Aligned_Attribute_Reference (Loc,
2143
                 Prefix         => R,
2144
                 Attribute_Name => Name_Address),
2145
 
2146
               RLexpr)));
2147
      end if;
2148
 
2149
      Analyze_And_Resolve (N, Standard_Boolean, Suppress => All_Checks);
2150
   end Expand_Packed_Eq;
2151
 
2152
   -----------------------
2153
   -- Expand_Packed_Not --
2154
   -----------------------
2155
 
2156
   --  Handles expansion of "not" on packed array types
2157
 
2158
   procedure Expand_Packed_Not (N : Node_Id) is
2159
      Loc  : constant Source_Ptr := Sloc (N);
2160
      Typ  : constant Entity_Id  := Etype (N);
2161
      Opnd : constant Node_Id    := Relocate_Node (Right_Opnd (N));
2162
 
2163
      Rtyp : Entity_Id;
2164
      PAT  : Entity_Id;
2165
      Lit  : Node_Id;
2166
 
2167
   begin
2168
      Convert_To_Actual_Subtype (Opnd);
2169
      Rtyp := Etype (Opnd);
2170
 
2171
      --  Deal with silly False..False and True..True subtype case
2172
 
2173
      Silly_Boolean_Array_Not_Test (N, Rtyp);
2174
 
2175
      --  Now that the silliness is taken care of, get packed array type
2176
 
2177
      Convert_To_PAT_Type (Opnd);
2178
      PAT := Etype (Opnd);
2179
 
2180
      --  For the case where the packed array type is a modular type, "not A"
2181
      --  expands simply into:
2182
 
2183
      --     Rtyp!(PAT!(A) xor Mask)
2184
 
2185
      --  where PAT is the packed array type, Mask is a mask of all 1 bits of
2186
      --  length equal to the size of this packed type, and Rtyp is the actual
2187
      --  actual subtype of the operand.
2188
 
2189
      Lit := Make_Integer_Literal (Loc, 2 ** RM_Size (PAT) - 1);
2190
      Set_Print_In_Hex (Lit);
2191
 
2192
      if not Is_Array_Type (PAT) then
2193
         Rewrite (N,
2194
           Unchecked_Convert_To (Rtyp,
2195
             Make_Op_Xor (Loc,
2196
               Left_Opnd  => Opnd,
2197
               Right_Opnd => Lit)));
2198
 
2199
      --  For the array case, we insert the actions
2200
 
2201
      --    Result : Typ;
2202
 
2203
      --    System.Bit_Ops.Bit_Not
2204
      --     (Opnd'Address,
2205
      --      Typ'Length * Typ'Component_Size,
2206
      --      Result'Address);
2207
 
2208
      --  where Opnd is the Packed_Bytes{1,2,4} operand and the second argument
2209
      --  is the length of the operand in bits. We then replace the expression
2210
      --  with a reference to Result.
2211
 
2212
      else
2213
         declare
2214
            Result_Ent : constant Entity_Id := Make_Temporary (Loc, 'T');
2215
 
2216
         begin
2217
            Insert_Actions (N, New_List (
2218
              Make_Object_Declaration (Loc,
2219
                Defining_Identifier => Result_Ent,
2220
                Object_Definition   => New_Occurrence_Of (Rtyp, Loc)),
2221
 
2222
              Make_Procedure_Call_Statement (Loc,
2223
                Name => New_Occurrence_Of (RTE (RE_Bit_Not), Loc),
2224
                  Parameter_Associations => New_List (
2225
                    Make_Byte_Aligned_Attribute_Reference (Loc,
2226
                      Prefix         => Opnd,
2227
                      Attribute_Name => Name_Address),
2228
 
2229
                    Make_Op_Multiply (Loc,
2230
                      Left_Opnd =>
2231
                        Make_Attribute_Reference (Loc,
2232
                          Prefix         =>
2233
                            New_Occurrence_Of
2234
                              (Etype (First_Index (Rtyp)), Loc),
2235
                          Attribute_Name => Name_Range_Length),
2236
 
2237
                      Right_Opnd =>
2238
                        Make_Integer_Literal (Loc, Component_Size (Rtyp))),
2239
 
2240
                    Make_Byte_Aligned_Attribute_Reference (Loc,
2241
                      Prefix         => New_Occurrence_Of (Result_Ent, Loc),
2242
                      Attribute_Name => Name_Address)))));
2243
 
2244
            Rewrite (N, New_Occurrence_Of (Result_Ent, Loc));
2245
         end;
2246
      end if;
2247
 
2248
      Analyze_And_Resolve (N, Typ, Suppress => All_Checks);
2249
   end Expand_Packed_Not;
2250
 
2251
   -----------------------------
2252
   -- Get_Base_And_Bit_Offset --
2253
   -----------------------------
2254
 
2255
   procedure Get_Base_And_Bit_Offset
2256
     (N      : Node_Id;
2257
      Base   : out Node_Id;
2258
      Offset : out Node_Id)
2259
   is
2260
      Loc    : Source_Ptr;
2261
      Term   : Node_Id;
2262
      Atyp   : Entity_Id;
2263
      Subscr : Node_Id;
2264
 
2265
   begin
2266
      Base   := N;
2267
      Offset := Empty;
2268
 
2269
      --  We build up an expression serially that has the form
2270
 
2271
      --    linear-subscript * component_size       for each array reference
2272
      --      +  field'Bit_Position                 for each record field
2273
      --      +  ...
2274
 
2275
      loop
2276
         Loc := Sloc (Base);
2277
 
2278
         if Nkind (Base) = N_Indexed_Component then
2279
            Convert_To_Actual_Subtype (Prefix (Base));
2280
            Atyp := Etype (Prefix (Base));
2281
            Compute_Linear_Subscript (Atyp, Base, Subscr);
2282
 
2283
            Term :=
2284
              Make_Op_Multiply (Loc,
2285
                Left_Opnd => Subscr,
2286
                Right_Opnd =>
2287
                 Make_Attribute_Reference (Loc,
2288
                   Prefix         => New_Occurrence_Of (Atyp, Loc),
2289
                   Attribute_Name => Name_Component_Size));
2290
 
2291
         elsif Nkind (Base) = N_Selected_Component then
2292
            Term :=
2293
              Make_Attribute_Reference (Loc,
2294
                Prefix         => Selector_Name (Base),
2295
                Attribute_Name => Name_Bit_Position);
2296
 
2297
         else
2298
            return;
2299
         end if;
2300
 
2301
         if No (Offset) then
2302
            Offset := Term;
2303
 
2304
         else
2305
            Offset :=
2306
              Make_Op_Add (Loc,
2307
                Left_Opnd  => Offset,
2308
                Right_Opnd => Term);
2309
         end if;
2310
 
2311
         Base := Prefix (Base);
2312
      end loop;
2313
   end Get_Base_And_Bit_Offset;
2314
 
2315
   -------------------------------------
2316
   -- Involves_Packed_Array_Reference --
2317
   -------------------------------------
2318
 
2319
   function Involves_Packed_Array_Reference (N : Node_Id) return Boolean is
2320
   begin
2321
      if Nkind (N) = N_Indexed_Component
2322
        and then Is_Bit_Packed_Array (Etype (Prefix (N)))
2323
      then
2324
         return True;
2325
 
2326
      elsif Nkind (N) = N_Selected_Component then
2327
         return Involves_Packed_Array_Reference (Prefix (N));
2328
 
2329
      else
2330
         return False;
2331
      end if;
2332
   end Involves_Packed_Array_Reference;
2333
 
2334
   --------------------------
2335
   -- Known_Aligned_Enough --
2336
   --------------------------
2337
 
2338
   function Known_Aligned_Enough (Obj : Node_Id; Csiz : Nat) return Boolean is
2339
      Typ : constant Entity_Id := Etype (Obj);
2340
 
2341
      function In_Partially_Packed_Record (Comp : Entity_Id) return Boolean;
2342
      --  If the component is in a record that contains previous packed
2343
      --  components, consider it unaligned because the back-end might
2344
      --  choose to pack the rest of the record. Lead to less efficient code,
2345
      --  but safer vis-a-vis of back-end choices.
2346
 
2347
      --------------------------------
2348
      -- In_Partially_Packed_Record --
2349
      --------------------------------
2350
 
2351
      function In_Partially_Packed_Record (Comp : Entity_Id) return Boolean is
2352
         Rec_Type  : constant Entity_Id := Scope (Comp);
2353
         Prev_Comp : Entity_Id;
2354
 
2355
      begin
2356
         Prev_Comp := First_Entity (Rec_Type);
2357
         while Present (Prev_Comp) loop
2358
            if Is_Packed (Etype (Prev_Comp)) then
2359
               return True;
2360
 
2361
            elsif Prev_Comp = Comp then
2362
               return False;
2363
            end if;
2364
 
2365
            Next_Entity (Prev_Comp);
2366
         end loop;
2367
 
2368
         return False;
2369
      end  In_Partially_Packed_Record;
2370
 
2371
   --  Start of processing for Known_Aligned_Enough
2372
 
2373
   begin
2374
      --  Odd bit sizes don't need alignment anyway
2375
 
2376
      if Csiz mod 2 = 1 then
2377
         return True;
2378
 
2379
      --  If we have a specified alignment, see if it is sufficient, if not
2380
      --  then we can't possibly be aligned enough in any case.
2381
 
2382
      elsif Known_Alignment (Etype (Obj)) then
2383
         --  Alignment required is 4 if size is a multiple of 4, and
2384
         --  2 otherwise (e.g. 12 bits requires 4, 10 bits requires 2)
2385
 
2386
         if Alignment (Etype (Obj)) < 4 - (Csiz mod 4) then
2387
            return False;
2388
         end if;
2389
      end if;
2390
 
2391
      --  OK, alignment should be sufficient, if object is aligned
2392
 
2393
      --  If object is strictly aligned, then it is definitely aligned
2394
 
2395
      if Strict_Alignment (Typ) then
2396
         return True;
2397
 
2398
      --  Case of subscripted array reference
2399
 
2400
      elsif Nkind (Obj) = N_Indexed_Component then
2401
 
2402
         --  If we have a pointer to an array, then this is definitely
2403
         --  aligned, because pointers always point to aligned versions.
2404
 
2405
         if Is_Access_Type (Etype (Prefix (Obj))) then
2406
            return True;
2407
 
2408
         --  Otherwise, go look at the prefix
2409
 
2410
         else
2411
            return Known_Aligned_Enough (Prefix (Obj), Csiz);
2412
         end if;
2413
 
2414
      --  Case of record field
2415
 
2416
      elsif Nkind (Obj) = N_Selected_Component then
2417
 
2418
         --  What is significant here is whether the record type is packed
2419
 
2420
         if Is_Record_Type (Etype (Prefix (Obj)))
2421
           and then Is_Packed (Etype (Prefix (Obj)))
2422
         then
2423
            return False;
2424
 
2425
         --  Or the component has a component clause which might cause
2426
         --  the component to become unaligned (we can't tell if the
2427
         --  backend is doing alignment computations).
2428
 
2429
         elsif Present (Component_Clause (Entity (Selector_Name (Obj)))) then
2430
            return False;
2431
 
2432
         elsif In_Partially_Packed_Record (Entity (Selector_Name (Obj))) then
2433
            return False;
2434
 
2435
         --  In all other cases, go look at prefix
2436
 
2437
         else
2438
            return Known_Aligned_Enough (Prefix (Obj), Csiz);
2439
         end if;
2440
 
2441
      elsif Nkind (Obj) = N_Type_Conversion then
2442
         return Known_Aligned_Enough (Expression (Obj), Csiz);
2443
 
2444
      --  For a formal parameter, it is safer to assume that it is not
2445
      --  aligned, because the formal may be unconstrained while the actual
2446
      --  is constrained. In this situation, a small constrained packed
2447
      --  array, represented in modular form, may be unaligned.
2448
 
2449
      elsif Is_Entity_Name (Obj) then
2450
         return not Is_Formal (Entity (Obj));
2451
      else
2452
 
2453
      --  If none of the above, must be aligned
2454
         return True;
2455
      end if;
2456
   end Known_Aligned_Enough;
2457
 
2458
   ---------------------
2459
   -- Make_Shift_Left --
2460
   ---------------------
2461
 
2462
   function Make_Shift_Left (N : Node_Id; S : Node_Id) return Node_Id is
2463
      Nod : Node_Id;
2464
 
2465
   begin
2466
      if Compile_Time_Known_Value (S) and then Expr_Value (S) = 0 then
2467
         return N;
2468
      else
2469
         Nod :=
2470
           Make_Op_Shift_Left (Sloc (N),
2471
             Left_Opnd  => N,
2472
             Right_Opnd => S);
2473
         Set_Shift_Count_OK (Nod, True);
2474
         return Nod;
2475
      end if;
2476
   end Make_Shift_Left;
2477
 
2478
   ----------------------
2479
   -- Make_Shift_Right --
2480
   ----------------------
2481
 
2482
   function Make_Shift_Right (N : Node_Id; S : Node_Id) return Node_Id is
2483
      Nod : Node_Id;
2484
 
2485
   begin
2486
      if Compile_Time_Known_Value (S) and then Expr_Value (S) = 0 then
2487
         return N;
2488
      else
2489
         Nod :=
2490
           Make_Op_Shift_Right (Sloc (N),
2491
             Left_Opnd  => N,
2492
             Right_Opnd => S);
2493
         Set_Shift_Count_OK (Nod, True);
2494
         return Nod;
2495
      end if;
2496
   end Make_Shift_Right;
2497
 
2498
   -----------------------------
2499
   -- RJ_Unchecked_Convert_To --
2500
   -----------------------------
2501
 
2502
   function RJ_Unchecked_Convert_To
2503
     (Typ  : Entity_Id;
2504
      Expr : Node_Id) return Node_Id
2505
   is
2506
      Source_Typ : constant Entity_Id := Etype (Expr);
2507
      Target_Typ : constant Entity_Id := Typ;
2508
 
2509
      Src : Node_Id := Expr;
2510
 
2511
      Source_Siz : Nat;
2512
      Target_Siz : Nat;
2513
 
2514
   begin
2515
      Source_Siz := UI_To_Int (RM_Size (Source_Typ));
2516
      Target_Siz := UI_To_Int (RM_Size (Target_Typ));
2517
 
2518
      --  First step, if the source type is not a discrete type, then we first
2519
      --  convert to a modular type of the source length, since otherwise, on
2520
      --  a big-endian machine, we get left-justification. We do it for little-
2521
      --  endian machines as well, because there might be junk bits that are
2522
      --  not cleared if the type is not numeric.
2523
 
2524
      if Source_Siz /= Target_Siz
2525
        and then not Is_Discrete_Type (Source_Typ)
2526
      then
2527
         Src := Unchecked_Convert_To (RTE (Bits_Id (Source_Siz)), Src);
2528
      end if;
2529
 
2530
      --  In the big endian case, if the lengths of the two types differ, then
2531
      --  we must worry about possible left justification in the conversion,
2532
      --  and avoiding that is what this is all about.
2533
 
2534
      if Bytes_Big_Endian and then Source_Siz /= Target_Siz then
2535
 
2536
         --  Next step. If the target is not a discrete type, then we first
2537
         --  convert to a modular type of the target length, since otherwise,
2538
         --  on a big-endian machine, we get left-justification.
2539
 
2540
         if not Is_Discrete_Type (Target_Typ) then
2541
            Src := Unchecked_Convert_To (RTE (Bits_Id (Target_Siz)), Src);
2542
         end if;
2543
      end if;
2544
 
2545
      --  And now we can do the final conversion to the target type
2546
 
2547
      return Unchecked_Convert_To (Target_Typ, Src);
2548
   end RJ_Unchecked_Convert_To;
2549
 
2550
   ----------------------------------------------
2551
   -- Setup_Enumeration_Packed_Array_Reference --
2552
   ----------------------------------------------
2553
 
2554
   --  All we have to do here is to find the subscripts that correspond to the
2555
   --  index positions that have non-standard enumeration types and insert a
2556
   --  Pos attribute to get the proper subscript value.
2557
 
2558
   --  Finally the prefix must be uncheck-converted to the corresponding packed
2559
   --  array type.
2560
 
2561
   --  Note that the component type is unchanged, so we do not need to fiddle
2562
   --  with the types (Gigi always automatically takes the packed array type if
2563
   --  it is set, as it will be in this case).
2564
 
2565
   procedure Setup_Enumeration_Packed_Array_Reference (N : Node_Id) is
2566
      Pfx   : constant Node_Id   := Prefix (N);
2567
      Typ   : constant Entity_Id := Etype (N);
2568
      Exprs : constant List_Id   := Expressions (N);
2569
      Expr  : Node_Id;
2570
 
2571
   begin
2572
      --  If the array is unconstrained, then we replace the array reference
2573
      --  with its actual subtype. This actual subtype will have a packed array
2574
      --  type with appropriate bounds.
2575
 
2576
      if not Is_Constrained (Packed_Array_Type (Etype (Pfx))) then
2577
         Convert_To_Actual_Subtype (Pfx);
2578
      end if;
2579
 
2580
      Expr := First (Exprs);
2581
      while Present (Expr) loop
2582
         declare
2583
            Loc      : constant Source_Ptr := Sloc (Expr);
2584
            Expr_Typ : constant Entity_Id := Etype (Expr);
2585
 
2586
         begin
2587
            if Is_Enumeration_Type (Expr_Typ)
2588
              and then Has_Non_Standard_Rep (Expr_Typ)
2589
            then
2590
               Rewrite (Expr,
2591
                 Make_Attribute_Reference (Loc,
2592
                   Prefix         => New_Occurrence_Of (Expr_Typ, Loc),
2593
                   Attribute_Name => Name_Pos,
2594
                   Expressions    => New_List (Relocate_Node (Expr))));
2595
               Analyze_And_Resolve (Expr, Standard_Natural);
2596
            end if;
2597
         end;
2598
 
2599
         Next (Expr);
2600
      end loop;
2601
 
2602
      Rewrite (N,
2603
        Make_Indexed_Component (Sloc (N),
2604
          Prefix      =>
2605
            Unchecked_Convert_To (Packed_Array_Type (Etype (Pfx)), Pfx),
2606
          Expressions => Exprs));
2607
 
2608
      Analyze_And_Resolve (N, Typ);
2609
   end Setup_Enumeration_Packed_Array_Reference;
2610
 
2611
   -----------------------------------------
2612
   -- Setup_Inline_Packed_Array_Reference --
2613
   -----------------------------------------
2614
 
2615
   procedure Setup_Inline_Packed_Array_Reference
2616
     (N      : Node_Id;
2617
      Atyp   : Entity_Id;
2618
      Obj    : in out Node_Id;
2619
      Cmask  : out Uint;
2620
      Shift  : out Node_Id)
2621
   is
2622
      Loc    : constant Source_Ptr := Sloc (N);
2623
      PAT    : Entity_Id;
2624
      Otyp   : Entity_Id;
2625
      Csiz   : Uint;
2626
      Osiz   : Uint;
2627
 
2628
   begin
2629
      Csiz := Component_Size (Atyp);
2630
 
2631
      Convert_To_PAT_Type (Obj);
2632
      PAT := Etype (Obj);
2633
 
2634
      Cmask := 2 ** Csiz - 1;
2635
 
2636
      if Is_Array_Type (PAT) then
2637
         Otyp := Component_Type (PAT);
2638
         Osiz := Component_Size (PAT);
2639
 
2640
      else
2641
         Otyp := PAT;
2642
 
2643
         --  In the case where the PAT is a modular type, we want the actual
2644
         --  size in bits of the modular value we use. This is neither the
2645
         --  Object_Size nor the Value_Size, either of which may have been
2646
         --  reset to strange values, but rather the minimum size. Note that
2647
         --  since this is a modular type with full range, the issue of
2648
         --  biased representation does not arise.
2649
 
2650
         Osiz := UI_From_Int (Minimum_Size (Otyp));
2651
      end if;
2652
 
2653
      Compute_Linear_Subscript (Atyp, N, Shift);
2654
 
2655
      --  If the component size is not 1, then the subscript must be multiplied
2656
      --  by the component size to get the shift count.
2657
 
2658
      if Csiz /= 1 then
2659
         Shift :=
2660
           Make_Op_Multiply (Loc,
2661
             Left_Opnd => Make_Integer_Literal (Loc, Csiz),
2662
             Right_Opnd => Shift);
2663
      end if;
2664
 
2665
      --  If we have the array case, then this shift count must be broken down
2666
      --  into a byte subscript, and a shift within the byte.
2667
 
2668
      if Is_Array_Type (PAT) then
2669
 
2670
         declare
2671
            New_Shift : Node_Id;
2672
 
2673
         begin
2674
            --  We must analyze shift, since we will duplicate it
2675
 
2676
            Set_Parent (Shift, N);
2677
            Analyze_And_Resolve
2678
              (Shift, Standard_Integer, Suppress => All_Checks);
2679
 
2680
            --  The shift count within the word is
2681
            --    shift mod Osiz
2682
 
2683
            New_Shift :=
2684
              Make_Op_Mod (Loc,
2685
                Left_Opnd  => Duplicate_Subexpr (Shift),
2686
                Right_Opnd => Make_Integer_Literal (Loc, Osiz));
2687
 
2688
            --  The subscript to be used on the PAT array is
2689
            --    shift / Osiz
2690
 
2691
            Obj :=
2692
              Make_Indexed_Component (Loc,
2693
                Prefix => Obj,
2694
                Expressions => New_List (
2695
                  Make_Op_Divide (Loc,
2696
                    Left_Opnd => Duplicate_Subexpr (Shift),
2697
                    Right_Opnd => Make_Integer_Literal (Loc, Osiz))));
2698
 
2699
            Shift := New_Shift;
2700
         end;
2701
 
2702
      --  For the modular integer case, the object to be manipulated is the
2703
      --  entire array, so Obj is unchanged. Note that we will reset its type
2704
      --  to PAT before returning to the caller.
2705
 
2706
      else
2707
         null;
2708
      end if;
2709
 
2710
      --  The one remaining step is to modify the shift count for the
2711
      --  big-endian case. Consider the following example in a byte:
2712
 
2713
      --     xxxxxxxx  bits of byte
2714
      --     vvvvvvvv  bits of value
2715
      --     33221100  little-endian numbering
2716
      --     00112233  big-endian numbering
2717
 
2718
      --  Here we have the case of 2-bit fields
2719
 
2720
      --  For the little-endian case, we already have the proper shift count
2721
      --  set, e.g. for element 2, the shift count is 2*2 = 4.
2722
 
2723
      --  For the big endian case, we have to adjust the shift count, computing
2724
      --  it as (N - F) - Shift, where N is the number of bits in an element of
2725
      --  the array used to implement the packed array, F is the number of bits
2726
      --  in a source array element, and Shift is the count so far computed.
2727
 
2728
      if Bytes_Big_Endian then
2729
         Shift :=
2730
           Make_Op_Subtract (Loc,
2731
             Left_Opnd  => Make_Integer_Literal (Loc, Osiz - Csiz),
2732
             Right_Opnd => Shift);
2733
      end if;
2734
 
2735
      Set_Parent (Shift, N);
2736
      Set_Parent (Obj, N);
2737
      Analyze_And_Resolve (Obj,   Otyp,             Suppress => All_Checks);
2738
      Analyze_And_Resolve (Shift, Standard_Integer, Suppress => All_Checks);
2739
 
2740
      --  Make sure final type of object is the appropriate packed type
2741
 
2742
      Set_Etype (Obj, Otyp);
2743
 
2744
   end Setup_Inline_Packed_Array_Reference;
2745
 
2746
end Exp_Pakd;

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