aboutsummaryrefslogtreecommitdiffstats
path: root/src/vhdl/vhdl-sem_scopes.adb
blob: fcc2707fa589b50e0babcffe120fb46ac0d9e91c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
--  Semantic analysis.
--  Copyright (C) 2002, 2003, 2004, 2005 Tristan Gingold
--
--  This program is free software: you can redistribute it and/or modify
--  it under the terms of the GNU General Public License as published by
--  the Free Software Foundation, either version 2 of the License, or
--  (at your option) any later version.
--
--  This program is distributed in the hope that it will be useful,
--  but WITHOUT ANY WARRANTY; without even the implied warranty of
--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
--  GNU General Public License for more details.
--
--  You should have received a copy of the GNU General Public License
--  along with this program.  If not, see <gnu.org/licenses>.
with Logging; use Logging;
with Tables;
with Flags; use Flags;
with Name_Table; -- use Name_Table;
with Files_Map; use Files_Map;
with Errorout; use Errorout;
with Vhdl.Errors; use Vhdl.Errors;
with Vhdl.Utils; use Vhdl.Utils;

package body Vhdl.Sem_Scopes is
   --  An interpretation cell is the element of the simply linked list
   --  of interpretation for an identifier.
   --  Interpretation cells are stored in table Interpretations.
   type Interpretation_Cell is record
      --  The declaration for this interpretation.
      Decl: Iir;

      --  If True, the declaration is potentially visible (ie visible via a
      --  use clause).
      Is_Potential : Boolean;

      --  If True, previous declarations in PREV chain are hidden and shouldn't
      --  be considered.
      Prev_Hidden : Boolean;

      --  Previous interpretation for this identifier.
      --  If No_Name_Interpretation, this (not PREV) interpretation is the last
      --  one. If Prev_Hidden is True, PREV must be ignored.  If Prev_Hidden is
      --  false, the identifier is overloaded.
      Prev: Name_Interpretation_Type;

      --  Previous added identifier in the declarative region.  This forms a
      --  linked list used to remove interpretations when a declarative
      --  region is closed.
      Prev_In_Region : Name_Id;
   end record;
   pragma Pack (Interpretation_Cell);

   package Interpretations is new Tables
     (Table_Component_Type => Interpretation_Cell,
      Table_Index_Type => Name_Interpretation_Type,
      Table_Low_Bound => First_Valid_Interpretation,
      Table_Initial => 1024);

   --  Cached value of Prev_In_Region of current region.
   Last_In_Region : Name_Id := Null_Identifier;

   --  First interpretation in the current declarative region.
   Current_Region_Start : Name_Interpretation_Type :=
     First_Valid_Interpretation;

   --  First valid interpretation.  All interpretations smaller than this
   --  value are part of a previous (and nested) analysis and must not be
   --  considered.
   First_Interpretation : Name_Interpretation_Type :=
     First_Valid_Interpretation;

   --  List of non-local hidden declarations.
   type Hide_Index is new Nat32;
   No_Hide_Index : constant Hide_Index := 0;

   package Hidden_Decls is new Tables
     (Table_Component_Type => Name_Interpretation_Type,
      Table_Index_Type => Hide_Index,
      Table_Low_Bound => No_Hide_Index + 1,
      Table_Initial => 32);

   --  First non-local hidden declarations.  In VHDL, it is possible to hide
   --  an overloaded declaration (by declaring a subprogram with the same
   --  profile).   If the overloaded declaration is local, the interpretation
   --  can simply be modified.  But if it is not local, the interpretation is
   --  removed from the chain and saved in the Hidden_Decls table.
   First_Hide_Index : Hide_Index := No_Hide_Index;

   -- To manage the list of interpretation and to add informations to this
   -- list, a stack is used.
   -- Elements of stack can be of kind:
   -- Save_Cell:
   --   the element contains the interpretation INTER for the indentifier ID
   --   for the outer declarative region.
   --   A save cell is always created each time a declaration is added to save
   --   the previous interpretation.
   -- Region_Start:
   --   A new declarative region start at interpretation INTER.  Here, INTER
   --   is used as an index in the interpretations stack (table).
   --   ID is used as an index into the unidim_array stack.
   -- Barrier_start, Barrier_end:
   --   All currents interpretations are saved between both INTER, and
   --   are cleared.  This is used to call semantic during another semantic.

   type Scope_Cell_Kind_Type is (Scope_Start, Scope_Region);

   type Scope_Cell is record
      Kind: Scope_Cell_Kind_Type;

      --  Values for the previous scope.
      Saved_Last_In_Region : Name_Id;
      Saved_Region_Start : Name_Interpretation_Type;
      Saved_First_Hide_Index : Hide_Index;
      Saved_First_Interpretation : Name_Interpretation_Type;
   end record;

   package Scopes is new Tables
     (Table_Component_Type => Scope_Cell,
      Table_Index_Type => Natural,
      Table_Low_Bound => 1,
      Table_Initial => 64);

   function Valid_Interpretation (Inter : Name_Interpretation_Type)
                                 return Boolean is
   begin
      return Inter >= First_Interpretation;
   end Valid_Interpretation;

   --  Return True iff NI means there is a conflict for the identifier: no
   --  valid interpretation due to potentially visible homoraph.
   function Is_Conflict_Declaration (Ni : Name_Interpretation_Type)
                                    return Boolean is
   begin
      pragma Assert (Valid_Interpretation (Ni));
      return Interpretations.Table (Ni).Decl = Null_Iir;
   end Is_Conflict_Declaration;

   --  Get the current interpretation for ID.  The result is raw: it may not
   --  be valid.
   function Get_Interpretation_Raw (Id : Name_Id)
                                   return Name_Interpretation_Type is
   begin
      return Name_Interpretation_Type (Name_Table.Get_Name_Info (Id));
   end Get_Interpretation_Raw;

   procedure Set_Interpretation
     (Id : Name_Id; Inter : Name_Interpretation_Type) is
   begin
      Name_Table.Set_Name_Info (Id, Int32 (Inter));
   end Set_Interpretation;

   function Get_Interpretation_From_Raw (Inter : Name_Interpretation_Type)
                                        return Name_Interpretation_Type is
   begin
      if Valid_Interpretation (Inter)
        and then not Is_Conflict_Declaration (Inter)
      then
         --  In the current scopes set and not a conflict.
         return Inter;
      else
         return No_Name_Interpretation;
      end if;
   end Get_Interpretation_From_Raw;

   function Get_Interpretation (Id : Name_Id)
                               return Name_Interpretation_Type is
   begin
      return Get_Interpretation_From_Raw (Get_Interpretation_Raw (Id));
   end Get_Interpretation;

   procedure Check_Interpretations;
   pragma Unreferenced (Check_Interpretations);

   procedure Check_Interpretations
   is
      Inter: Name_Interpretation_Type;
      Last : constant Name_Interpretation_Type := Interpretations.Last;
      Err : Boolean;
   begin
      Err := False;
      for I in 0 .. Name_Table.Last_Name_Id loop
         Inter := Get_Interpretation (I);
         if Inter > Last then
            Log_Line ("bad interpretation for " & Name_Table.Image (I));
            Err := True;
         end if;
      end loop;
      if Err then
         raise Internal_Error;
      end if;
   end Check_Interpretations;

   procedure Push_Interpretations is
   begin
      Scopes.Append ((Kind => Scope_Start,
                      Saved_Last_In_Region => Last_In_Region,
                      Saved_Region_Start => Current_Region_Start,
                      Saved_First_Hide_Index => First_Hide_Index,
                      Saved_First_Interpretation => First_Interpretation));
      Last_In_Region := Null_Identifier;
      Current_Region_Start := Interpretations.Last + 1;
      First_Hide_Index := Hidden_Decls.Last + 1;
      First_Interpretation := Interpretations.Last + 1;
   end Push_Interpretations;

   procedure Pop_Interpretations
   is
      Cell : Scope_Cell renames Scopes.Table (Scopes.Last);
   begin
      pragma Assert (Scopes.Table (Scopes.Last).Kind = Scope_Start);

      --  All the declarative regions must have been removed.
      pragma Assert (Last_In_Region = Null_Identifier);
      pragma Assert (Current_Region_Start = Interpretations.Last + 1);
      pragma Assert (First_Hide_Index = Hidden_Decls.Last + 1);
      pragma Assert (First_Interpretation = Interpretations.Last + 1);

      Last_In_Region := Cell.Saved_Last_In_Region;
      Current_Region_Start := Cell.Saved_Region_Start;
      First_Hide_Index := Cell.Saved_First_Hide_Index;
      First_Interpretation := Cell.Saved_First_Interpretation;

      Scopes.Decrement_Last;
   end Pop_Interpretations;

   --  Create a new declarative region.
   --  Simply push a region_start cell and update current_scope_start.
   procedure Open_Declarative_Region is
   begin
      Scopes.Append ((Kind => Scope_Region,
                      Saved_Last_In_Region => Last_In_Region,
                      Saved_Region_Start => Current_Region_Start,
                      Saved_First_Hide_Index => First_Hide_Index,
                      Saved_First_Interpretation => No_Name_Interpretation));
      Last_In_Region := Null_Identifier;
      Current_Region_Start := Interpretations.Last + 1;
      First_Hide_Index := Hidden_Decls.Last + 1;
   end Open_Declarative_Region;

   --  Close a declarative region.
   --  Update interpretation of identifiers.
   procedure Close_Declarative_Region
   is
      Cell : Scope_Cell renames Scopes.Table (Scopes.Last);
      Id : Name_Id;
   begin
      pragma Assert (Cell.Kind = Scope_Region);

      --  Restore hidden declarations.
      for I in reverse First_Hide_Index .. Hidden_Decls.Last loop
         declare
            Inter : constant Name_Interpretation_Type :=
              Hidden_Decls.Table (I);
            Prev_Inter, Next_Inter : Name_Interpretation_Type;
         begin
            Prev_Inter := Interpretations.Table (Inter).Prev;
            Next_Inter := Interpretations.Table (Prev_Inter).Prev;
            Interpretations.Table (Inter).Prev := Next_Inter;
            Interpretations.Table (Prev_Inter).Prev := Inter;
         end;
      end loop;
      Hidden_Decls.Set_Last (First_Hide_Index - 1);

      --  Remove interpretations of that region.
      Id := Last_In_Region;
      if Id /= Null_Identifier then
         declare
            Inter : Name_Interpretation_Type;
         begin
            loop
               Inter := Get_Interpretation_Raw (Id);
               pragma Assert (Inter >= Current_Region_Start);
               Set_Interpretation (Id, Interpretations.Table (Inter).Prev);
               Id := Interpretations.Table (Inter).Prev_In_Region;
               exit when Id = Null_Identifier;
            end loop;
            pragma Assert (Inter = Current_Region_Start);
         end;
         Interpretations.Set_Last (Current_Region_Start - 1);
      end if;

      Last_In_Region := Cell.Saved_Last_In_Region;
      Current_Region_Start := Cell.Saved_Region_Start;
      First_Hide_Index := Cell.Saved_First_Hide_Index;

      Scopes.Decrement_Last;
   end Close_Declarative_Region;

   procedure Open_Scope_Extension renames Open_Declarative_Region;
   procedure Close_Scope_Extension renames Close_Declarative_Region;

   function Get_Next_Interpretation (Ni : Name_Interpretation_Type)
                                    return Name_Interpretation_Type
   is
      pragma Assert (Valid_Interpretation (Ni));
      Cell : Interpretation_Cell renames Interpretations.Table (Ni);
   begin
      if Cell.Prev_Hidden
        or else not Valid_Interpretation (Cell.Prev)
      then
         return No_Name_Interpretation;
      else
         return Cell.Prev;
      end if;
   end Get_Next_Interpretation;

   function Get_Declaration (Ni : Name_Interpretation_Type) return Iir is
   begin
      pragma Assert (Valid_Interpretation (Ni));
      return Interpretations.Table (Ni).Decl;
   end Get_Declaration;

   function Get_Under_Interpretation (Id : Name_Id)
                                     return Name_Interpretation_Type
   is
      Inter : constant Name_Interpretation_Type := Get_Interpretation (Id);
   begin
      --  ID has no interpretation.
      --  So, there is no 'under' interpretation (FIXME: prove it).
      pragma Assert (Valid_Interpretation (Inter));

      declare
         Cell : Interpretation_Cell renames Interpretations.Table (Inter);
         Prev : constant Name_Interpretation_Type := Cell.Prev;
      begin
         --  Get_Under_Interpretation can be used only to get a hidden
         --  interpretation.
         pragma Assert (Cell.Prev_Hidden);

         if Valid_Interpretation (Prev)
           --  Not a conflict one (use clauses).
           and then Get_Declaration (Prev) /= Null_Iir
         then
            return Prev;
         else
            return No_Name_Interpretation;
         end if;
      end;
   end Get_Under_Interpretation;

   function Strip_Non_Object_Alias (Decl : Iir) return Iir
   is
      Res : Iir;
   begin
      Res := Decl;
      if Get_Kind (Res) = Iir_Kind_Non_Object_Alias_Declaration then
         Res := Get_Named_Entity (Get_Name (Res));
      end if;
      return Res;
   end Strip_Non_Object_Alias;

   function Get_Non_Alias_Declaration (Ni : Name_Interpretation_Type)
                                      return Iir is
   begin
      return Strip_Non_Object_Alias (Get_Declaration (Ni));
   end Get_Non_Alias_Declaration;

   --  Return TRUE if INTER was made directly visible via a use clause.
   function Is_Potentially_Visible (Inter : Name_Interpretation_Type)
                                   return Boolean is
   begin
      return Interpretations.Table (Inter).Is_Potential;
   end Is_Potentially_Visible;

   --  Return TRUE iif DECL can be overloaded.
   function Is_Overloadable (Decl : Iir) return Boolean is
   begin
      --  LRM93 10.3:
      --  The overloaded declarations considered in this chapter are those for
      --  subprograms and enumeration literals.
      case Get_Kind (Decl) is
         when Iir_Kind_Enumeration_Literal
           | Iir_Kind_Function_Declaration
           | Iir_Kind_Procedure_Declaration
           | Iir_Kind_Interface_Function_Declaration
           | Iir_Kind_Interface_Procedure_Declaration =>
            return True;
         when Iir_Kind_Non_Object_Alias_Declaration =>
            case Get_Kind (Get_Named_Entity (Get_Name (Decl))) is
               when Iir_Kind_Enumeration_Literal
                 | Iir_Kind_Function_Declaration
                 | Iir_Kind_Procedure_Declaration
                 | Iir_Kind_Interface_Function_Declaration
                 | Iir_Kind_Interface_Procedure_Declaration =>
                  return True;
               when Iir_Kind_Non_Object_Alias_Declaration =>
                  raise Internal_Error;
               when others =>
                  return False;
            end case;
         when others =>
            return False;
      end case;
   end Is_Overloadable;

   --  Return TRUE if INTER was made direclty visible in the current
   --  declarative region.
   function Is_In_Current_Declarative_Region (Inter : Name_Interpretation_Type)
                                             return Boolean is
   begin
      return Inter >= Current_Region_Start;
   end Is_In_Current_Declarative_Region;

   --  Emit a warning when DECL hides PREV_DECL.
   procedure Warning_Hide (Decl : Iir; Prev_Decl : Iir)
   is
   begin
      if Get_Kind (Decl) in Iir_Kinds_Interface_Declaration
        and then Get_Kind (Get_Parent (Decl)) = Iir_Kind_Component_Declaration
      then
         --  Do not warn when an interface in a component hides a declaration.
         --  This is a common case (eg: in testbenches), and there is no real
         --  hiding.
         return;
      end if;

      if Get_Kind (Decl) = Iir_Kind_Element_Declaration then
         --  Do not warn for record elements.  They are used by selection.
         return;
      end if;

      if Decl = Prev_Decl then
         --  Can happen in configuration.  No real hidding.
         return;
      end if;

      if Name_Table.Get_Name_Ptr (Get_Identifier (Decl))(1) = 'P' then
         --  Do not warn for labels starting with 'P'.  These are canonicalized
         --  process labels which are scoped.
         --  This can happen as an architecture is canonicalized during
         --  analysis and then its declarations are 'imported' by a
         --  configuration.
         return;
      end if;

      Warning_Msg_Sem (Warnid_Hide, +Decl,
                       "declaration of %i hides %n", (+Decl, +Prev_Decl));
   end Warning_Hide;

   --  Add interpretation DECL to the identifier of DECL.
   --  POTENTIALLY is true if the identifier comes from a use clause.
   procedure Add_Name (Decl : Iir; Ident : Name_Id; Potentially : Boolean)
   is
      -- Current interpretation of ID.  This is the one before DECL is
      -- added (if so).
      Raw_Inter : constant Name_Interpretation_Type :=
        Get_Interpretation_Raw (Ident);
      Current_Inter : constant Name_Interpretation_Type :=
        Get_Interpretation_From_Raw (Raw_Inter);
      Current_Decl : Iir;

      --  Add DECL in the chain of interpretation for the identifier.
      procedure Add_New_Interpretation (Hid_Prev : Boolean; D : Iir := Decl) is
      begin
         Interpretations.Append ((Decl => D,
                                  Prev => Raw_Inter,
                                  Is_Potential => Potentially,
                                  Prev_Hidden => Hid_Prev,
                                  Prev_In_Region => Last_In_Region));
         Set_Interpretation (Ident, Interpretations.Last);
         Last_In_Region := Ident;
      end Add_New_Interpretation;
   begin
      if Ident = Null_Identifier then
         --  Missing identifier can happen only in case of parse error.
         pragma Assert (Flags.Flag_Force_Analysis);
         return;
      end if;

      if not Valid_Interpretation (Raw_Inter) then
         --  Very simple: no hidding, no overloading.
         Add_New_Interpretation (True);
         return;
      end if;

      if Is_Conflict_Declaration (Raw_Inter) then
         --  The current declaration for RAW_INTER is a conflict: there are
         --  multiple *potentially* visible declarations for the identifier.
         if Potentially then
            --  Yet another conflicting interpretation.
            return;
         else
            --  Very simple: no hidding, no overloading.
            --  (current interpretation is Conflict_Interpretation if there is
            --   only potentially visible declarations that are not made
            --   directly visible).
            --  Note: in case of conflict interpretation, it may be unnecessary
            --  to keep the current interpretation (but it is simpler as is).
            Add_New_Interpretation (True);
            return;
         end if;
      end if;

      if Potentially then
         --  Do not re-add a potential decl.  This handles cases like:
         --  'use p.all; use p.all;'.
         --  FIXME: add a flag (or reuse Visible_Flag) to avoid walking all
         --  the interpretations.
         declare
            Inter : Name_Interpretation_Type := Current_Inter;
         begin
            while Valid_Interpretation (Inter) loop
               if Get_Declaration (Inter) = Decl then
                  return;
               end if;
               Inter := Get_Next_Interpretation (Inter);
            end loop;
         end;
      end if;

      --  LRM 10.3 Visibility
      --  Each of two declarations is said to be a homograph of the other if
      --  both declarations have the same identifier, operator symbol, or
      --  character literal, and overloading is allowed for at most one
      --  of the two.
      --
      --  GHDL: the condition 'overloading is allowed for at most one of the
      --  two' is false iff overloading is allowed for both; this is a nand.

      --  Note: at this stage, current_inter is valid.
      Current_Decl := Get_Declaration (Current_Inter);

      if Is_Overloadable (Current_Decl) and then Is_Overloadable (Decl) then
         --  Current_Inter and Decl overloads (well, they have the same
         --  designator).

         --  LRM 10.3 Visibility
         --  If overloading is allowed for both declarations, then each of the
         --  two is a homograph of the other if they have the same identifier,
         --  operator symbol or character literal, as well as the same
         --  parameter and result profile.

         declare
            Homograph : Name_Interpretation_Type;
            Prev_Homograph : Name_Interpretation_Type;

            --  Hide HOMOGRAPH (ie unlink it from the chain of interpretation).
            procedure Hide_Homograph
            is
               S : Name_Interpretation_Type;
            begin
               if Prev_Homograph = No_Name_Interpretation then
                  Prev_Homograph := Interpretations.Last;
               end if;

               --  PREV_HOMOGRAPH must be the interpretation just before
               --  HOMOGRAPH.
               pragma Assert
                 (Interpretations.Table (Prev_Homograph).Prev = Homograph);

               --  Hide previous interpretation.
               Hidden_Decls.Append (Homograph);

               S := Interpretations.Table (Homograph).Prev;
               Interpretations.Table (Homograph).Prev := Prev_Homograph;
               Interpretations.Table (Prev_Homograph).Prev := S;
            end Hide_Homograph;

            function Get_Hash_Non_Alias (D : Iir) return Iir_Int32 is
            begin
               return Get_Subprogram_Hash (Strip_Non_Object_Alias (D));
            end Get_Hash_Non_Alias;

            --  Return True iff D is an implicit declaration (either a
            --  subprogram or an implicit alias).
            function Is_Implicit_Declaration (D : Iir) return Boolean is
            begin
               case Get_Kind (D) is
                  when Iir_Kind_Non_Object_Alias_Declaration =>
                     return Get_Implicit_Alias_Flag (D);
                  when Iir_Kind_Enumeration_Literal =>
                     return False;
                  when Iir_Kind_Procedure_Declaration
                    | Iir_Kind_Function_Declaration =>
                     return Is_Implicit_Subprogram (D);
                  when others =>
                     Error_Kind ("is_implicit_declaration", D);
               end case;
            end Is_Implicit_Declaration;

            --  Return TRUE iff D is an implicit alias of an implicit
            --  subprogram.
            function Is_Implicit_Alias (D : Iir) return Boolean is
            begin
               --  FIXME: Is it possible to have an implicit alias of an
               --  explicit subprogram ? Yes for enumeration literal and
               --  physical units.
               return Get_Kind (D) = Iir_Kind_Non_Object_Alias_Declaration
                 and then Get_Implicit_Alias_Flag (D)
                 and then Is_Implicit_Subprogram (Get_Named_Entity
                                                    (Get_Name (D)));
            end Is_Implicit_Alias;

            --  Replace the homograph of DECL by DECL.
            procedure Replace_Homograph is
            begin
               Interpretations.Table (Homograph).Decl := Decl;
            end Replace_Homograph;

            Decl_Hash : Iir_Int32;
            Hash : Iir_Int32;
         begin
            Decl_Hash := Get_Hash_Non_Alias (Decl);
            --  The hash must have been computed.
            pragma Assert (Decl_Hash /= 0);

            --  LRM02 10.3 Visibility
            --  Each of two declarations is said to be a /homograph/ of the
            --  other if both declarations have the same identifier, operator
            --  symbol, or character literal, and if overloading is allowed for
            --  at most one of the two.
            --
            --  LRM08 12.3 Visibility
            --  Each of two declarations is said to be a /homograph/ of the
            --  other if and only if both declarations have the same
            --  designator, and they denote different named entities, and
            --  either overloading is allows for at most one of the two, or
            --  overloading is allowed for both declarations and they have the
            --  same parameter and result type profile.

            --  GHDL: here we are in the case when both declarations are
            --  overloadable.  Also, always follow the LRM08 rules as they fix
            --  issues.
            --  GHDL: Special case for a second declaration with the same
            --  designator and that denotes the same named entity than a
            --  previous one (that would be an alias): according to the LRM,
            --  they are both visible and there are no ambiguity as they
            --  denotes the same named entity.  In GHDL, the new one hides the
            --  previous one.  The behaviour should be the same.

            --  Find an homograph of this declaration (and also keep the
            --  interpretation just before it in the chain).
            Homograph := Current_Inter;
            Prev_Homograph := No_Name_Interpretation;
            while Homograph /= No_Name_Interpretation loop
               Current_Decl := Get_Declaration (Homograph);
               Hash := Get_Hash_Non_Alias (Current_Decl);
               exit when Decl_Hash = Hash
                 and then Is_Same_Profile (Decl, Current_Decl);
               Prev_Homograph := Homograph;
               Homograph := Get_Next_Interpretation (Homograph);
            end loop;

            if Homograph = No_Name_Interpretation then
               --  Simple case: no homograph.
               Add_New_Interpretation (False);
               return;
            end if;

            --  There is an homograph (or the named entity is the same).
            if Potentially then
               --  Added DECL would be made potentially visible.

               --  LRM93 10.4 1) / LRM08 12.4 a) Use Clauses
               --  1. A potentially visible declaration is not made
               --     directly visible if the place considered is within the
               --     immediate scope of a homograph of the declaration.
               if not Is_Potentially_Visible (Homograph) then
                  return;
               end if;

               --  LRM08 12.4 Use Clauses
               --  b) If two potentially visible declarations are homograph
               --     and one is explicitly declared and the other is
               --     implicitly declared, then the implicit declaration is
               --     not made directly visible.
               if (Flags.Flag_Explicit or else Flags.Vhdl_Std >= Vhdl_08)
                 and then Is_Potentially_Visible (Homograph)
               then
                  declare
                     Implicit_Current_Decl : constant Boolean :=
                       Is_Implicit_Declaration (Current_Decl);
                     Implicit_Decl : constant Boolean :=
                       Is_Implicit_Declaration (Decl);
                  begin
                     if Implicit_Current_Decl and then not Implicit_Decl then
                        if Is_In_Current_Declarative_Region (Homograph) then
                           Replace_Homograph;
                        else
                           --  Insert DECL and hide homograph.
                           Add_New_Interpretation (False);
                           Hide_Homograph;
                        end if;
                        return;
                     elsif not Implicit_Current_Decl and then Implicit_Decl
                     then
                        --  Discard decl.
                        return;
                     elsif Strip_Non_Object_Alias (Decl)
                       = Strip_Non_Object_Alias (Current_Decl)
                     then
                        --  This rule is not written clearly in the LRM, but
                        --  if two designators denote the same named entity,
                        --  no need to make both visible.
                        return;
                     end if;
                  end;
               end if;

               --  GHDL: if the homograph is in the same declarative
               --  region than DECL, it must be an implicit declaration
               --  to be hidden.
               --  FIXME: this rule is not in the LRM93, but it is necessary
               --  so that explicit declaration hides the implicit one.
               if Flags.Vhdl_Std < Vhdl_08
                 and then not Flags.Flag_Explicit
                 and then Get_Parent (Decl) = Get_Parent (Current_Decl)
               then
                  declare
                     Implicit_Current_Decl : constant Boolean :=
                       Is_Implicit_Subprogram (Current_Decl);
                     Implicit_Decl : constant Boolean :=
                       Is_Implicit_Subprogram (Decl);
                  begin
                     if Implicit_Current_Decl and not Implicit_Decl then
                        --  Note: no need to save previous interpretation, as
                        --  it is in the same declarative region.
                        --  Replace the previous homograph with DECL.
                        Replace_Homograph;
                        return;
                     elsif not Implicit_Current_Decl and Implicit_Decl then
                        --  As we have replaced the homograph, it is possible
                        --  than the implicit declaration is re-added (by
                        --  a new use clause).  Discard it.
                        return;
                     end if;
                  end;
               end if;

               --  The homograph was made visible in an outer declarative
               --  region.  Therefore, it must not be hidden.
               Add_New_Interpretation (False);

               return;
            else
               --  Added DECL would be made directly visible.

               if not Is_Potentially_Visible (Homograph) then
                  --  The homograph was also declared in that declarative
                  --  region or in an inner one.
                  if Is_In_Current_Declarative_Region (Homograph) then
                     --  ... and was declared in the same region

                     --  To sum up: at this point both DECL and CURRENT_DECL
                     --  are overloadable, have the same profile (but may be
                     --  aliases) and are declared in the same declarative
                     --  region.

                     --  LRM08 12.3 Visibility
                     --  LRM93 10.3 Visibility
                     --  Two declarations that occur immediately within
                     --  the same declarative regions [...] shall not be
                     --  homograph, unless exactely one of them is the
                     --  implicit declaration of a predefined operation,

                     --  LRM08 12.3 Visibility
                     --  or is an implicit alias of such implicit declaration.
                     --
                     --  GHDL: FIXME: 'implicit alias'

                     --  LRM08 12.3 Visibility
                     --  LRM93 10.3 Visibility
                     --  Each of two declarations is said to be a
                     --  homograph of the other if and only if both
                     --  declarations have the same designator, [...]
                     --
                     --  LRM08 12.3 Visibility
                     --  [...] and they denote different named entities,
                     --  and [...]
                     declare
                        Is_Decl_Implicit : Boolean;
                        Is_Current_Decl_Implicit : Boolean;
                     begin
                        if Flags.Vhdl_Std >= Vhdl_08 then
                           Is_Current_Decl_Implicit :=
                             Is_Implicit_Subprogram (Current_Decl)
                             or else Is_Implicit_Alias (Current_Decl);
                           Is_Decl_Implicit := Is_Implicit_Subprogram (Decl)
                             or else Is_Implicit_Alias (Decl);

                           --  If they denote the same entity, they aren't
                           --  homograph.
                           if Strip_Non_Object_Alias (Decl)
                             = Strip_Non_Object_Alias (Current_Decl)
                           then
                              if Is_Current_Decl_Implicit
                                and then not Is_Decl_Implicit
                              then
                                 --  They aren't homograph but DECL is stronger
                                 --  (at it is not an implicit declaration)
                                 --  than CURRENT_DECL
                                 Replace_Homograph;
                              end if;

                              return;
                           end if;

                           if Is_Decl_Implicit
                             and then not Is_Current_Decl_Implicit
                           then
                              --  Re-declaration of an implicit subprogram via
                              --  an implicit alias is simply discarded.
                              return;
                           end if;
                        else
                           --  Can an implicit subprogram declaration appears
                           --  after an explicit one in vhdl 93?  I don't
                           --  think so.
                           Is_Decl_Implicit := Is_Implicit_Subprogram (Decl);
                           Is_Current_Decl_Implicit :=
                             Is_Implicit_Subprogram (Current_Decl);
                        end if;

                        if not (Is_Decl_Implicit xor Is_Current_Decl_Implicit)
                        then
                           Error_Msg_Sem
                             (+Decl, "redeclaration of %n defined at %l",
                              (+Current_Decl, +Current_Decl));
                           return;
                        end if;

                        if not Is_Decl_Implicit and Is_Current_Decl_Implicit
                        then
                           --  DECL 'overrides' the predefined current
                           --  declaration.

                           --  LRM93 10.3 Visibility
                           --  In such cases, a predefined operation is always
                           --  hidden by the other homograph.  Where hidden in
                           --  this manner, an implicit declaration is hidden
                           --  within the entire scope of the other declaration
                           --  (regardless of which declaration occurs first);
                           --  the implicit declaration is visible neither by
                           --  selection nor directly.
                           Set_Visible_Flag (Current_Decl, False);
                           if Get_Kind (Decl)
                             in Iir_Kinds_Subprogram_Declaration
                           then
                              Set_Hide_Implicit_Flag (Decl, True);
                           end if;
                        end if;
                     end;
                  else
                     --  GHDL: hide directly visible declaration declared in
                     --  an outer region.
                     null;
                  end if;
               else
                  --  LRM 10.4 Use Clauses
                  --  1. A potentially visible declaration is not made
                  --  directly visible if the place considered is within the
                  --  immediate scope of a homograph of the declaration.

                  --  GHDL: hide the potentially visible declaration.
                  null;
               end if;
               Add_New_Interpretation (False);

               Hide_Homograph;
               return;
            end if;
         end;
      end if;

      --  The current interpretation and the new one aren't overloadable, ie
      --  they are homograph (well almost).

      if Is_Potentially_Visible (Current_Inter) then
         if Potentially then
            --  LRM93 10.4 2) / LRM08 12.4 c) Use clauses
            --  Potentially visible declarations that have the same
            --  designator are not made directly visible unless each of
            --  them is either an enumeration literal specification or
            --  the declaration of a subprogram.
            if Decl = Get_Declaration (Current_Inter) then
               -- The rule applies only for distinct declaration.
               -- This handles 'use p.all; use P.all;'.
               -- FIXME: this should have been handled at the start of
               -- this subprogram.
               raise Internal_Error;
               return;
            end if;

            --  LRM08 12.3 Visibility
            --  Each of two declarations is said to be a homograph of the
            --  other if and only if both declarations have the same
            --  designator; and they denote different named entities, [...]
            if Flags.Vhdl_Std >= Vhdl_08 then
               if Strip_Non_Object_Alias (Decl)
                 = Strip_Non_Object_Alias (Current_Decl)
               then
                  return;
               end if;
            end if;

            --  Conflict.
            Add_New_Interpretation (True, Null_Iir);
            return;
         else
            --  LRM93 10.4 item #1
            --  A potentially visible declaration is not made directly
            --  visible if the place considered is within the immediate
            --  scope of a homograph of the declaration.
            --  GHDL: Could directly replace the previous interpretation
            --  (added in same scope), but don't do that for entity
            --  declarations, since it is used to find default binding.
            Add_New_Interpretation (True);
            return;
         end if;
      else
         --  There is already a declaration in the current scope.
         if Potentially then
            -- LRM93 10.4 item #1
            -- Discard the new and potentially visible declaration.
            -- However, add the type.
            -- FIXME: Add_In_Visible_List (Ident, Decl);
            return;
         else
            if Is_In_Current_Declarative_Region (Current_Inter) then
               --  They are perhaps visible in the same declarative region.

               if Get_Kind (Current_Decl) = Iir_Kind_Library_Declaration then
                  --  LRM93 11.2
                  --  If two or more logical names having the same
                  --  identifier appear in library clauses in the same
                  --  context, the second and subsequent occurences of the
                  --  logical name have no effect.  The same is true of
                  --  logical names appearing both in the context clause
                  --  of a primary unit and in the context clause of a
                  --  corresponding secondary unit.
                  --  GHDL: we apply this rule with VHDL-87, because of
                  --  implicit library clauses STD and WORK.
                  if Get_Kind (Decl) = Iir_Kind_Library_Declaration then
                     return;
                  end if;

                  if Flag_Relaxed_Rules
                    and then Get_Kind (Decl) in Iir_Kinds_Library_Unit
                  then
                     Warning_Msg_Sem
                       (Warnid_Hide, +Decl,
                        "unit %i hides library %i", (+Decl, +Decl));
                     Interpretations.Table (Current_Inter).Decl := Decl;
                     return;
                  end if;
               end if;

               -- None of the two declarations are potentially visible, ie
               -- both are visible.
               -- LRM 10.3:
               --  Two declarations that occur immediately within the same
               --  declarative region must not be homographs,
               -- FIXME: unless one of them is the implicit declaration of a
               --  predefined operation.
               Report_Start_Group;
               Error_Msg_Sem
                 (+Decl, "identifier %i already used for a declaration",
                  +Ident);
               Error_Msg_Sem
                 (+Current_Decl, "previous declaration: %n", +Current_Decl);
               Report_End_Group;
               return;
            else
               --  Homograph, not in the same scope.
               --  LRM93 10.3:
               --  A declaration is said to be hidden within (part of) an inner
               --  declarative region if the inner region contains an homograph
               --  of this declaration; the outer declaration is the hidden
               --  within the immediate scope of the inner homograph.
               if Is_Warning_Enabled (Warnid_Hide)
                 and then not Is_Potentially_Visible (Current_Inter)
               then
                  Warning_Hide (Decl, Current_Decl);
               end if;

               Add_New_Interpretation (True);
               return;
            end if;
         end if;
      end if;
   end Add_Name;

   procedure Add_Name (Decl: Iir) is
   begin
      Add_Name (Decl, Get_Identifier (Decl), False);
   end Add_Name;

   procedure Replace_Name (Id: Name_Id; Old : Iir; Decl: Iir)
   is
      Inter : Name_Interpretation_Type;
   begin
      Inter := Get_Interpretation (Id);
      loop
         exit when Get_Declaration (Inter) = Old;
         Inter := Get_Next_Interpretation (Inter);
         pragma Assert (Valid_Interpretation (Inter));
      end loop;
      Interpretations.Table (Inter).Decl := Decl;
      pragma Assert (Get_Next_Interpretation (Inter) = No_Name_Interpretation);
   end Replace_Name;

   procedure Name_Visible (Decl : Iir) is
   begin
      --  A name can be made visible only once.
      pragma Assert (not Get_Visible_Flag (Decl));
      Set_Visible_Flag (Decl, True);
   end Name_Visible;

   procedure Iterator_Decl (Decl : Iir; Arg : Arg_Type) is
   begin
      case Get_Kind (Decl) is
         when Iir_Kind_Subtype_Declaration
           | Iir_Kind_Enumeration_Literal --  By use clause
           | Iir_Kind_Constant_Declaration
           | Iir_Kind_Signal_Declaration
           | Iir_Kind_Variable_Declaration
           | Iir_Kind_File_Declaration
           | Iir_Kind_Object_Alias_Declaration
           | Iir_Kind_Non_Object_Alias_Declaration
           | Iir_Kinds_Interface_Object_Declaration
           | Iir_Kind_Interface_Package_Declaration
           | Iir_Kinds_Interface_Subprogram_Declaration
           | Iir_Kind_Component_Declaration
           | Iir_Kind_Attribute_Declaration
           | Iir_Kind_Group_Template_Declaration
           | Iir_Kind_Group_Declaration
           | Iir_Kind_Nature_Declaration
           | Iir_Kind_Subnature_Declaration
           | Iir_Kinds_Quantity_Declaration
           | Iir_Kind_Terminal_Declaration
           | Iir_Kind_Entity_Declaration
           | Iir_Kind_Package_Declaration
           | Iir_Kind_Package_Instantiation_Declaration
           | Iir_Kind_Configuration_Declaration
           | Iir_Kind_Context_Declaration
           | Iir_Kinds_Concurrent_Statement
           | Iir_Kinds_Sequential_Statement =>
            Handle_Decl (Decl, Arg);
         when Iir_Kind_Procedure_Declaration
           | Iir_Kind_Function_Declaration =>
            if not Is_Second_Subprogram_Specification (Decl) then
               Handle_Decl (Decl, Arg);
            end if;
         when Iir_Kind_Type_Declaration =>
            declare
               Def : constant Iir := Get_Type_Definition (Decl);
               List : Iir_Flist;
               El : Iir;
            begin
               -- Handle incomplete type declaration.
               if Get_Kind (Def) = Iir_Kind_Incomplete_Type_Definition then
                  return;
               end if;

               Handle_Decl (Decl, Arg);

               if Get_Kind (Def) = Iir_Kind_Enumeration_Type_Definition then
                  List := Get_Enumeration_Literal_List (Def);
                  for I in Flist_First .. Flist_Last (List) loop
                     El := Get_Nth_Element (List, I);
                     Handle_Decl (El, Arg);
                  end loop;
               end if;
            end;
         when Iir_Kind_Anonymous_Type_Declaration =>
            Handle_Decl (Decl, Arg);

            declare
               Def : constant Iir := Get_Type_Definition (Decl);
               El : Iir;
            begin
               if Get_Kind (Def) = Iir_Kind_Physical_Type_Definition then
                  El := Get_Unit_Chain (Def);
                  while El /= Null_Iir loop
                     Handle_Decl (El, Arg);
                     El := Get_Chain (El);
                  end loop;
               end if;
            end;
         when Iir_Kind_Interface_Type_Declaration =>
            Handle_Decl (Decl, Arg);
            declare
               El : Iir;
            begin
               El := Get_Interface_Type_Subprograms (Decl);
               while El /= Null_Iir loop
                  Handle_Decl (El, Arg);
                  El := Get_Chain (El);
               end loop;
            end;
         when Iir_Kind_Use_Clause
           | Iir_Kind_Context_Reference =>
            Handle_Decl (Decl, Arg);
         when Iir_Kind_Library_Clause =>
            Handle_Decl (Decl, Arg);
--             El := Get_Library_Declaration (Decl);
--             if El /= Null_Iir then
--                --  May be empty.
--                Handle_Decl (El, Arg);
--             end if;

         when Iir_Kind_Procedure_Body
           | Iir_Kind_Function_Body =>
            null;

         when Iir_Kind_Package_Body =>
            null;

         when Iir_Kind_Attribute_Specification
           | Iir_Kind_Configuration_Specification
           | Iir_Kind_Disconnection_Specification =>
            null;
         when Iir_Kinds_Signal_Attribute
           | Iir_Kind_Attribute_Implicit_Declaration =>
            null;

         when Iir_Kind_Protected_Type_Body
           | Iir_Kind_Suspend_State_Declaration =>
            --  FIXME: allowed only in debugger (if the current scope is
            --  within a package body) ?
            null;

         when others =>
            Error_Kind ("iterator_decl", Decl);
      end case;
   end Iterator_Decl;

   --  Handle context_clause of context reference CTXT.
   procedure Add_One_Context_Reference (Ctxt : Iir)
   is
      Name : constant Iir := Get_Selected_Name (Ctxt);
      Ent : constant Iir := Get_Named_Entity (Name);
      Item : Iir;
   begin
      if Ent = Null_Iir or else Is_Error (Ent) then
         --  Stop now in case of error.
         return;
      end if;
      pragma Assert (Get_Kind (Ent) = Iir_Kind_Context_Declaration);

      Item := Get_Context_Items (Ent);
      while Item /= Null_Iir loop
         case Get_Kind (Item) is
            when Iir_Kind_Use_Clause =>
               Add_Use_Clause (Item);
            when Iir_Kind_Library_Clause =>
               Add_Name (Get_Library_Declaration (Item),
                         Get_Identifier (Item), False);
            when Iir_Kind_Context_Reference =>
               Add_Context_Reference (Item);
            when others =>
               Error_Kind ("add_context_reference", Item);
         end case;
         Item := Get_Chain (Item);
      end loop;
   end Add_One_Context_Reference;

   procedure Add_Context_Reference (Ref : Iir)
   is
      Ctxt : Iir;
   begin
      Ctxt := Ref;
      loop
         Add_One_Context_Reference (Ctxt);
         Ctxt := Get_Context_Reference_Chain (Ctxt);
         exit when Ctxt = Null_Iir;
      end loop;
   end Add_Context_Reference;

   --  Make POTENTIALLY (or not) visible DECL.
   procedure Add_Name_Decl (Decl : Iir; Potentially : Boolean) is
   begin
      case Get_Kind (Decl) is
         when Iir_Kind_Use_Clause =>
            if not Potentially then
               Add_Use_Clause (Decl);
            end if;
         when Iir_Kind_Context_Reference =>
            pragma Assert (not Potentially);
            Add_Context_Reference (Decl);
         when Iir_Kind_Library_Clause =>
            Add_Name (Get_Library_Declaration (Decl),
                      Get_Identifier (Decl), Potentially);
         when Iir_Kind_Anonymous_Type_Declaration =>
            null;
         when others =>
            Add_Name (Decl, Get_Identifier (Decl), Potentially);
      end case;
   end Add_Name_Decl;

   procedure Add_Declaration is
      new Iterator_Decl (Arg_Type => Boolean, Handle_Decl => Add_Name_Decl);

   procedure Iterator_Decl_List (Decl_List : Iir_List; Arg : Arg_Type)
   is
      Decl : Iir;
      It : List_Iterator;
   begin
      if Decl_List = Null_Iir_List then
         return;
      end if;
      It := List_Iterate (Decl_List);
      while Is_Valid (It) loop
         Decl := Get_Element (It);
         Handle_Decl (Decl, Arg);
         Next (It);
      end loop;
   end Iterator_Decl_List;

   procedure Iterator_Decl_Chain (Chain_First : Iir; Arg : Arg_Type)
   is
      Decl: Iir;
   begin
      Decl := Chain_First;
      while Decl /= Null_Iir loop
         Handle_Decl (Decl, Arg);
         Decl := Get_Chain (Decl);
      end loop;
   end Iterator_Decl_Chain;

   procedure Add_Declarations_1 is new Iterator_Decl_Chain
     (Arg_Type => Boolean, Handle_Decl => Add_Declaration);

   procedure Add_Declarations (Chain : Iir; Potentially : Boolean := False)
     renames Add_Declarations_1;

   procedure Add_Declarations_List is new Iterator_Decl_List
     (Arg_Type => Boolean, Handle_Decl => Add_Declaration);

   procedure Add_Declarations_From_Interface_Chain
     (Chain : Iir; Potentially : Boolean)
   is
      Inter : Iir;
      Assoc : Iir;
      Id : Name_Id;
   begin
      Inter := Chain;
      while Inter /= Null_Iir loop
         Id := Get_Identifier (Inter);

         --  The chain may be from an implicitely declared subprograms, with
         --  anonymous identifiers.  In that case, all interfaces are
         --  anonymous and there is no need to iterate.
         exit when Id = Null_Identifier;

         --  Not very different from Add_Declaration, except for interface
         --  subprograms.
         case Iir_Kinds_Interface_Declaration (Get_Kind (Inter)) is
            when Iir_Kinds_Interface_Object_Declaration
              | Iir_Kind_Interface_Package_Declaration
              | Iir_Kind_Interface_Terminal_Declaration =>
               Add_Name (Inter, Id, Potentially);
            when Iir_Kinds_Interface_Subprogram_Declaration =>
               if Potentially then
                  --  The normal case: an interface subprogram in a package
                  --  is visible through a use clause.  But in fact it refer
                  --  to the associated subprogram.
                  Assoc := Get_Associated_Subprogram (Inter);
                  pragma Assert (Assoc /= Null_Iir);
                  Add_Name (Assoc, Id, Potentially);
               else
                  --  Called only when resolving associations (the identifiers
                  --  of the interfaces are put in the name table).
                  --  TODO: add a flag or create a different procedure ?
                  Add_Name (Inter, Id, Potentially);
               end if;
            when Iir_Kind_Interface_Type_Declaration =>
               Add_Name (Inter, Id, Potentially);
               declare
                  El : Iir;
               begin
                  El := Get_Interface_Type_Subprograms (Inter);
                  while El /= Null_Iir loop
                     Add_Name (El, Get_Identifier (El), Potentially);
                     El := Get_Chain (El);
                  end loop;
               end;
         end case;

         Inter := Get_Chain (Inter);
      end loop;
   end Add_Declarations_From_Interface_Chain;

   procedure Add_Declarations_Of_Concurrent_Statement (Parent : Iir)
   is
      El: Iir;
      Label: Name_Id;
   begin
      El := Get_Concurrent_Statement_Chain (Parent);
      while El /= Null_Iir loop
         Label := Get_Label (El);
         if Label /= Null_Identifier then
            Add_Name (El, Get_Identifier (El), False);
         end if;
         El := Get_Chain (El);
      end loop;
   end Add_Declarations_Of_Concurrent_Statement;

   procedure Add_Context_Clauses (Unit : Iir_Design_Unit) is
   begin
      Add_Declarations (Get_Context_Items (Unit), False);
   end Add_Context_Clauses;

   -- Add declarations from an entity into the current declarative region.
   -- This is needed when an architecture is analysed.
   procedure Add_Entity_Declarations (Entity : Iir_Entity_Declaration)
   is
      Prev_Hide : constant Boolean := Is_Warning_Enabled (Warnid_Hide);
   begin
      --  Temporarly disable hide warning to avoid spurious messages.
      Enable_Warning (Warnid_Hide, False);

      Add_Declarations_From_Interface_Chain
        (Get_Generic_Chain (Entity), False);
      Add_Declarations_From_Interface_Chain
        (Get_Port_Chain (Entity), False);
      Add_Declarations (Get_Declaration_Chain (Entity), False);
      Add_Declarations_Of_Concurrent_Statement (Entity);

      --  Restore
      Enable_Warning (Warnid_Hide, Prev_Hide);
   end Add_Entity_Declarations;

   --  Add declarations from a package into the current declarative region.
   --  (for a use clause or when a package body is analyzed)
   procedure Add_Package_Declarations
     (Decl: Iir_Package_Declaration; Potentially : Boolean)
   is
      Header : constant Iir := Get_Package_Header (Decl);
   begin
      --  LRM08 12.1 Declarative region
      --  d) A package declaration together with the corresponding body
      --
      --  GHDL: the formal generic declarations are considered to be in the
      --  same declarative region as the package declarations (and therefore
      --  in the same scope), even if they don't occur immediately within a
      --  package declaration.
      if Header /= Null_Iir then
         Add_Declarations (Get_Generic_Chain (Header), Potentially);
      end if;

      Add_Declarations (Get_Declaration_Chain (Decl), Potentially);
   end Add_Package_Declarations;

   procedure Add_Package_Instantiation_Declarations
     (Decl: Iir; Potentially : Boolean) is
   begin
      --  LRM08 4.9 Package instantiation declarations
      --  The package instantiation declaration is equivalent to declaration of
      --  a generic-mapped package, consisting of a package declaration [...]
      Add_Declarations_From_Interface_Chain
        (Get_Generic_Chain (Decl), Potentially);
      Add_Declarations (Get_Declaration_Chain (Decl), Potentially);
   end Add_Package_Instantiation_Declarations;

   --  Add declarations from a package into the current declarative region.
   --  This is needed when a package body is analysed.
   procedure Add_Package_Declarations (Decl: Iir_Package_Declaration) is
   begin
      Add_Package_Declarations (Decl, False);
   end Add_Package_Declarations;

   procedure Add_Component_Declarations
     (Component: Iir_Component_Declaration) is
   begin
      Add_Declarations_From_Interface_Chain
        (Get_Generic_Chain (Component), False);
      Add_Declarations_From_Interface_Chain
        (Get_Port_Chain (Component), False);
   end Add_Component_Declarations;

   procedure Add_Protected_Type_Declarations
     (Decl : Iir_Protected_Type_Declaration) is
   begin
      Add_Declarations (Get_Declaration_Chain (Decl), False);
   end Add_Protected_Type_Declarations;

   procedure Extend_Scope_Of_Block_Declarations (Decl : Iir) is
   begin
      case Get_Kind (Decl) is
         when Iir_Kind_Architecture_Body =>
            Add_Context_Clauses (Get_Design_Unit (Decl));
         when Iir_Kind_Block_Statement
           | Iir_Kind_Generate_Statement_Body =>
            --  FIXME: formal, iterator ?
            null;
         when others =>
            Error_Kind ("extend_scope_of_block_declarations", Decl);
      end case;
      Add_Declarations (Get_Declaration_Chain (Decl), False);
      Add_Declarations_Of_Concurrent_Statement (Decl);
   end Extend_Scope_Of_Block_Declarations;

   procedure Use_Library_All (Library : Iir_Library_Declaration)
   is
      Design_File : Iir_Design_File;
      Design_Unit : Iir_Design_Unit;
      Library_Unit : Iir;
   begin
      Design_File := Get_Design_File_Chain (Library);
      while Design_File /= Null_Iir loop
         Design_Unit := Get_First_Design_Unit (Design_File);
         while Design_Unit /= Null_Iir loop
            Library_Unit := Get_Library_Unit (Design_Unit);
            if Get_Kind (Library_Unit) /= Iir_Kind_Package_Body then
               Add_Name (Design_Unit, Get_Identifier (Design_Unit), True);
            end if;
            Design_Unit := Get_Chain (Design_Unit);
         end loop;
         Design_File := Get_Chain (Design_File);
      end loop;
   end Use_Library_All;

   procedure Potentially_Add_Name (Name : Iir) is
   begin
      Add_Name (Name, Get_Identifier (Name), True);
   end Potentially_Add_Name;

   --  LRM08 12.4 Use clauses
   --  Moreover, the following declarations, if any, that occurs immediately
   --  within the package denoted by the prefix of the selected name, are also
   --  identifier:
   procedure Use_Selected_Type_Name (Name : Iir)
   is
      Type_Def : constant Iir := Get_Type (Name);
      Base_Type : constant Iir := Get_Base_Type (Type_Def);
   begin
      case Get_Kind (Base_Type) is
         when Iir_Kind_Enumeration_Type_Definition =>
            --  LRM08 12.4 Use clauses
            --  - If the type mark denotes an enumeration type of a subtype of
            --    an enumeration type, the enumeration literals of the base
            --    type
            declare
               List : constant Iir_Flist :=
                 Get_Enumeration_Literal_List (Base_Type);
               El : Iir;
            begin
               for I in Flist_First .. Flist_Last (List) loop
                  El := Get_Nth_Element (List, I);
                  Potentially_Add_Name (El);
               end loop;
            end;
         when Iir_Kind_Physical_Type_Definition =>
            --  LRM08 12.4 Use clauses
            --  - If the type mark denotes a subtype of a physical type, the
            --    units of the base type
            declare
               El : Iir;
            begin
               El := Get_Unit_Chain (Base_Type);
               while El /= Null_Iir loop
                  Potentially_Add_Name (El);
                  El := Get_Chain (El);
               end loop;
            end;
         when others =>
            null;
      end case;

      --  LRM08 12.4 Use clauses
      --  - The implicit declarations of predefined operations for the type
      --    that are not hidden by homographs explicitly declared immediately
      --    within the package denoted by the prefix of the selected name
      --  - The declarations of homographs, explicitly declared immediately
      --    within the package denotes by the prefix of the selected name,
      --    that hide implicit declarations of predefined operations for the
      --    type
      declare
         Type_Decl : constant Iir := Get_Type_Declarator (Base_Type);
         El : Iir;
         Has_Override : Boolean;
      begin
         Has_Override := False;
         El := Get_Chain (Type_Decl);
         while El /= Null_Iir loop
            if Is_Implicit_Subprogram (El)
              and then Is_Operation_For_Type (El, Base_Type)
            then
               if Get_Visible_Flag (El) then
                  --  Implicit declaration EL was overriden by a user
                  --  declaration.  Don't make it visible.
                  Potentially_Add_Name (El);
               else
                  Has_Override := True;
               end if;
               El := Get_Chain (El);
            else
               exit;
            end if;
         end loop;

         --  Explicitly declared homograph.
         if Has_Override then
            while El /= Null_Iir loop
               if Get_Kind (El) in Iir_Kinds_Subprogram_Declaration
                 and then Get_Hide_Implicit_Flag (El)
                 and then Is_Operation_For_Type (El, Base_Type)
               then
                  Potentially_Add_Name (El);
               end if;
               El := Get_Chain (El);
            end loop;
         end if;
      end;
   end Use_Selected_Type_Name;

   --  LRM02 10.4 Use clauses
   --  Each selected name in a use clause identifiers one or more declarations
   --  that will potentially become directly visible. If the suffix of the
   --  selected name is a simple name, a character literal, or operator
   --  symbol, then the selected name identifiers only the declarations(s) of
   --  that simple name, character literal, or operator symbol contained
   --  within the package or library denoted by the prefix of the selected
   --  name.
   procedure Use_Selected_Name (Name : Iir)
   is
      Nname : Iir;
   begin
      if Name = Null_Iir then
         return;
      end if;

      case Get_Kind (Name) is
         when Iir_Kind_Overload_List =>
            Add_Declarations_List (Get_Overload_List (Name), True);
         when Iir_Kind_Error =>
            null;
         when others =>
            Potentially_Add_Name (Name);

            --  LRM08 12.4 Use clauses
            --  If the suffix of the selected name is a type mark, then the
            --  declaration of the type or subtype denoted by the type mark
            --  is identified. Moreover [...]
            if (Vhdl_Std >= Vhdl_08 or else Flag_Relaxed_Rules) then
               Nname := Strip_Non_Object_Alias (Name);
               if Get_Kind (Nname) in Iir_Kinds_Type_Declaration then
                  Use_Selected_Type_Name (Nname);
               end if;
            end if;
      end case;
   end Use_Selected_Name;

   --  LRM93 10.4 Use clauses
   --  If the suffix is the reserved word ALL, then all the selected name
   --  identifies all declaration that are contained within the package or
   --  library denotes by te prefix of the selected name.
   procedure Use_All_Names (Name: Iir) is
   begin
      case Get_Kind (Name) is
         when Iir_Kind_Library_Declaration =>
            Use_Library_All (Name);
         when Iir_Kind_Package_Declaration =>
            Add_Package_Declarations (Name, True);
         when Iir_Kind_Package_Instantiation_Declaration =>
            Add_Package_Instantiation_Declarations (Name, True);
         when Iir_Kind_Interface_Package_Declaration =>
            --  LRM08 6.5.5 Interface package declarations
            --  Within an entity declaration, an architecture body, a
            --  component declaration, or an uninstantiated subprogram or
            --  package declaration that declares a given interface package,
            --  the name of the given interface package denotes an undefined
            --  instance of the uninstantiated package.
            Add_Package_Instantiation_Declarations (Name, True);
         when Iir_Kind_Error =>
            null;
         when others =>
            raise Internal_Error;
      end case;
   end Use_All_Names;

   procedure Add_Use_Clause (Clause : Iir_Use_Clause)
   is
      Name : Iir;
      Cl : Iir_Use_Clause;
   begin
      Cl := Clause;
      loop
         Name := Get_Selected_Name (Cl);
         if Name = Null_Iir then
            pragma Assert (Flags.Flag_Force_Analysis);
            null;
         else
            if Get_Kind (Name) = Iir_Kind_Selected_By_All_Name then
               Name := Get_Prefix (Name);
               if not Is_Error (Name) then
                  Use_All_Names (Get_Named_Entity (Name));
               end if;
            else
               if not Is_Error (Name) then
                  Use_Selected_Name (Get_Named_Entity (Name));
               end if;
            end if;
         end if;
         Cl := Get_Use_Clause_Chain (Cl);
         exit when Cl = Null_Iir;
      end loop;
   end Add_Use_Clause;

   procedure Add_Inherit_Spec (Spec : Iir)
   is
      Name : constant Iir := Get_Name (Spec);
      Unit : Iir;
      Item : Iir;
   begin
      if Name = Null_Iir then
         return;
      end if;
      Unit := Get_Named_Entity (Name);
      Item := Get_Vunit_Item_Chain (Unit);
      while Item /= Null_Iir loop
         case Get_Kind (Item) is
            when Iir_Kind_Psl_Declaration =>
               Potentially_Add_Name (Item);
            when others =>
               Error_Kind ("add_inherit_spec", Item);
         end case;
         Item := Get_Chain (Item);
      end loop;
   end Add_Inherit_Spec;

   --  Debugging subprograms.
   procedure Disp_All_Names;
   pragma Unreferenced (Disp_All_Names);

   procedure Disp_Scopes;
   pragma Unreferenced (Disp_Scopes);

   procedure Disp_Detailed_Interpretations (Ident : Name_Id);
   pragma Unreferenced (Disp_Detailed_Interpretations);

   procedure Dump_Current_Scope;
   pragma Unreferenced (Dump_Current_Scope);

   procedure Disp_Detailed_Interpretations (Ident : Name_Id)
   is
      Inter: Name_Interpretation_Type;
      Decl : Iir;
   begin
      Log (Name_Table.Image (Ident));
      Log_Line (":");

      Inter := Get_Interpretation (Ident);
      while Valid_Interpretation (Inter) loop
         Log (Name_Interpretation_Type'Image (Inter));
         if Is_Potentially_Visible (Inter) then
            Log (" (use)");
         end if;
         Log (":");
         Decl := Get_Declaration (Inter);
         Log (Iir'Image (Decl));
         Log (":");
         Log (Iir_Kind'Image (Get_Kind (Decl)));
         Log_Line (", loc: " & Image (Get_Location (Decl)));
         if Get_Kind (Decl) in Iir_Kinds_Subprogram_Declaration then
            Log_Line ("   " & Disp_Subprg (Decl));
         end if;
         Inter := Get_Next_Interpretation (Inter);
      end loop;
   end Disp_Detailed_Interpretations;

   procedure Disp_All_Interpretations
     (Interpretation : Name_Interpretation_Type)
   is
      Inter: Name_Interpretation_Type;
   begin
      Inter := Interpretation;
      while Valid_Interpretation (Inter) loop
         Log (Name_Interpretation_Type'Image (Inter));
         Log (".");
         Log (Iir_Kind'Image (Get_Kind (Get_Declaration (Inter))));
         Inter := Get_Next_Interpretation (Inter);
      end loop;
      Log_Line;
   end Disp_All_Interpretations;

   procedure Disp_All_Names
   is
      Inter: Name_Interpretation_Type;
   begin
      for I in 0 .. Name_Table.Last_Name_Id loop
         Inter := Get_Interpretation (I);
         if Valid_Interpretation (Inter) then
            Log (Name_Table.Image (I));
            Log (Name_Id'Image (I));
            Log (":");
            Disp_All_Interpretations (Inter);
         end if;
      end loop;
      Log_Line ("interprations.last = "
                & Name_Interpretation_Type'Image (Interpretations.Last));
      Log_Line ("current_region_start ="
                & Name_Interpretation_Type'Image (Current_Region_Start));
   end Disp_All_Names;

   procedure Dump_Interpretation (Inter : Name_Interpretation_Type)
   is
      Decl : Iir;
   begin
      Log (Name_Interpretation_Type'Image (Inter));
      if Is_Potentially_Visible (Inter) then
         Log (" (use)");
      end if;
      Log (": ");
      Decl := Get_Declaration (Inter);
      if Decl = Null_Iir then
         Log_Line ("null: conflict");
      else
         Log (Iir_Kind'Image (Get_Kind (Decl)));
         Log_Line (", loc: " & Image (Get_Location (Decl)));
         if Get_Kind (Decl) in Iir_Kinds_Subprogram_Declaration then
            Log_Line ("   " & Disp_Subprg (Decl));
         end if;
      end if;
   end Dump_Interpretation;

   procedure Dump_A_Scope (First, Last : Name_Interpretation_Type) is
   begin
      if First > Last then
         Log_Line ("scope is empty");
         return;
      end if;

      for Inter in reverse First .. Last loop
         declare
            Cell : Interpretation_Cell renames Interpretations.Table (Inter);
         begin
            Dump_Interpretation (Inter);
            if Cell.Prev_Hidden then
               Log ("  [prev:");
               Log (Name_Interpretation_Type'Image (Cell.Prev));
               if Cell.Prev_Hidden then
                  Log (" hidden");
               end if;
               Log_Line ("]");
            else
               if Cell.Prev < First then
                  Log_Line (" [last in scope]");
               end if;
            end if;
         end;
      end loop;
   end Dump_A_Scope;

   procedure Dump_Current_Scope is
   begin
      Dump_A_Scope (Current_Region_Start, Interpretations.Last);
   end Dump_Current_Scope;

   procedure Disp_Scopes is
   begin
      for I in reverse Scopes.First .. Scopes.Last loop
         declare
            S : Scope_Cell renames Scopes.Table (I);
         begin
            case S.Kind is
               when Scope_Start =>
                  Log ("scope_start at");
               when Scope_Region =>
                  Log ("scope_region at");
            end case;
            Log_Line (Name_Interpretation_Type'Image (S.Saved_Region_Start));
         end;
      end loop;
   end Disp_Scopes;
end Vhdl.Sem_Scopes;