summaryrefslogtreecommitdiff
path: root/gdb/alpha-tdep.c
blob: 141f57651a1f98320ef653ca4644698780117e96 (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
/* Target-dependent code for the ALPHA architecture, for GDB, the GNU Debugger.

   Copyright 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
   2002, 2003, 2005 Free Software Foundation, Inc.

   This file is part of GDB.

   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, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include "defs.h"
#include "doublest.h"
#include "frame.h"
#include "frame-unwind.h"
#include "frame-base.h"
#include "dwarf2-frame.h"
#include "inferior.h"
#include "symtab.h"
#include "value.h"
#include "gdbcmd.h"
#include "gdbcore.h"
#include "dis-asm.h"
#include "symfile.h"
#include "objfiles.h"
#include "gdb_string.h"
#include "linespec.h"
#include "regcache.h"
#include "reggroups.h"
#include "arch-utils.h"
#include "osabi.h"
#include "block.h"
#include "infcall.h"

#include "elf-bfd.h"

#include "alpha-tdep.h"


/* Return the name of the REGNO register.

   An empty name corresponds to a register number that used to
   be used for a virtual register. That virtual register has
   been removed, but the index is still reserved to maintain
   compatibility with existing remote alpha targets.  */

static const char *
alpha_register_name (int regno)
{
  static const char * const register_names[] =
  {
    "v0",   "t0",   "t1",   "t2",   "t3",   "t4",   "t5",   "t6",
    "t7",   "s0",   "s1",   "s2",   "s3",   "s4",   "s5",   "fp",
    "a0",   "a1",   "a2",   "a3",   "a4",   "a5",   "t8",   "t9",
    "t10",  "t11",  "ra",   "t12",  "at",   "gp",   "sp",   "zero",
    "f0",   "f1",   "f2",   "f3",   "f4",   "f5",   "f6",   "f7",
    "f8",   "f9",   "f10",  "f11",  "f12",  "f13",  "f14",  "f15",
    "f16",  "f17",  "f18",  "f19",  "f20",  "f21",  "f22",  "f23",
    "f24",  "f25",  "f26",  "f27",  "f28",  "f29",  "f30",  "fpcr",
    "pc",   "",     "unique"
  };

  if (regno < 0)
    return NULL;
  if (regno >= (sizeof(register_names) / sizeof(*register_names)))
    return NULL;
  return register_names[regno];
}

static int
alpha_cannot_fetch_register (int regno)
{
  return (regno == ALPHA_ZERO_REGNUM
          || strlen (alpha_register_name (regno)) == 0);
}

static int
alpha_cannot_store_register (int regno)
{
  return (regno == ALPHA_ZERO_REGNUM
          || strlen (alpha_register_name (regno)) == 0);
}

static struct type *
alpha_register_type (struct gdbarch *gdbarch, int regno)
{
  if (regno == ALPHA_SP_REGNUM || regno == ALPHA_GP_REGNUM)
    return builtin_type_void_data_ptr;
  if (regno == ALPHA_PC_REGNUM)
    return builtin_type_void_func_ptr;

  /* Don't need to worry about little vs big endian until 
     some jerk tries to port to alpha-unicosmk.  */
  if (regno >= ALPHA_FP0_REGNUM && regno < ALPHA_FP0_REGNUM + 31)
    return builtin_type_ieee_double_little;

  return builtin_type_int64;
}

/* Is REGNUM a member of REGGROUP?  */

static int
alpha_register_reggroup_p (struct gdbarch *gdbarch, int regnum,
			   struct reggroup *group)
{
  /* Filter out any registers eliminated, but whose regnum is 
     reserved for backward compatibility, e.g. the vfp.  */
  if (REGISTER_NAME (regnum) == NULL || *REGISTER_NAME (regnum) == '\0')
    return 0;

  if (group == all_reggroup)
    return 1;

  /* Zero should not be saved or restored.  Technically it is a general
     register (just as $f31 would be a float if we represented it), but
     there's no point displaying it during "info regs", so leave it out
     of all groups except for "all".  */
  if (regnum == ALPHA_ZERO_REGNUM)
    return 0;

  /* All other registers are saved and restored.  */
  if (group == save_reggroup || group == restore_reggroup)
    return 1;

  /* All other groups are non-overlapping.  */

  /* Since this is really a PALcode memory slot...  */
  if (regnum == ALPHA_UNIQUE_REGNUM)
    return group == system_reggroup;

  /* Force the FPCR to be considered part of the floating point state.  */
  if (regnum == ALPHA_FPCR_REGNUM)
    return group == float_reggroup;

  if (regnum >= ALPHA_FP0_REGNUM && regnum < ALPHA_FP0_REGNUM + 31)
    return group == float_reggroup;
  else
    return group == general_reggroup;
}

static int
alpha_register_byte (int regno)
{
  return (regno * 8);
}

/* The following represents exactly the conversion performed by
   the LDS instruction.  This applies to both single-precision
   floating point and 32-bit integers.  */

static void
alpha_lds (void *out, const void *in)
{
  ULONGEST mem     = extract_unsigned_integer (in, 4);
  ULONGEST frac    = (mem >>  0) & 0x7fffff;
  ULONGEST sign    = (mem >> 31) & 1;
  ULONGEST exp_msb = (mem >> 30) & 1;
  ULONGEST exp_low = (mem >> 23) & 0x7f;
  ULONGEST exp, reg;

  exp = (exp_msb << 10) | exp_low;
  if (exp_msb)
    {
      if (exp_low == 0x7f)
	exp = 0x7ff;
    }
  else
    {
      if (exp_low != 0x00)
	exp |= 0x380;
    }

  reg = (sign << 63) | (exp << 52) | (frac << 29);
  store_unsigned_integer (out, 8, reg);
}

/* Similarly, this represents exactly the conversion performed by
   the STS instruction.  */

static void
alpha_sts (void *out, const void *in)
{
  ULONGEST reg, mem;

  reg = extract_unsigned_integer (in, 8);
  mem = ((reg >> 32) & 0xc0000000) | ((reg >> 29) & 0x3fffffff);
  store_unsigned_integer (out, 4, mem);
}

/* The alpha needs a conversion between register and memory format if the
   register is a floating point register and memory format is float, as the
   register format must be double or memory format is an integer with 4
   bytes or less, as the representation of integers in floating point
   registers is different. */

static int
alpha_convert_register_p (int regno, struct type *type)
{
  return (regno >= ALPHA_FP0_REGNUM && regno < ALPHA_FP0_REGNUM + 31);
}

static void
alpha_register_to_value (struct frame_info *frame, int regnum,
			 struct type *valtype, gdb_byte *out)
{
  char in[MAX_REGISTER_SIZE];
  frame_register_read (frame, regnum, in);
  switch (TYPE_LENGTH (valtype))
    {
    case 4:
      alpha_sts (out, in);
      break;
    case 8:
      memcpy (out, in, 8);
      break;
    default:
      error (_("Cannot retrieve value from floating point register"));
    }
}

static void
alpha_value_to_register (struct frame_info *frame, int regnum,
			 struct type *valtype, const gdb_byte *in)
{
  char out[MAX_REGISTER_SIZE];
  switch (TYPE_LENGTH (valtype))
    {
    case 4:
      alpha_lds (out, in);
      break;
    case 8:
      memcpy (out, in, 8);
      break;
    default:
      error (_("Cannot store value in floating point register"));
    }
  put_frame_register (frame, regnum, out);
}


/* The alpha passes the first six arguments in the registers, the rest on
   the stack.  The register arguments are stored in ARG_REG_BUFFER, and
   then moved into the register file; this simplifies the passing of a
   large struct which extends from the registers to the stack, plus avoids
   three ptrace invocations per word.

   We don't bother tracking which register values should go in integer
   regs or fp regs; we load the same values into both.

   If the called function is returning a structure, the address of the
   structure to be returned is passed as a hidden first argument.  */

static CORE_ADDR
alpha_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
		       struct regcache *regcache, CORE_ADDR bp_addr,
		       int nargs, struct value **args, CORE_ADDR sp,
		       int struct_return, CORE_ADDR struct_addr)
{
  int i;
  int accumulate_size = struct_return ? 8 : 0;
  struct alpha_arg
    {
      char *contents;
      int len;
      int offset;
    };
  struct alpha_arg *alpha_args
    = (struct alpha_arg *) alloca (nargs * sizeof (struct alpha_arg));
  struct alpha_arg *m_arg;
  char arg_reg_buffer[ALPHA_REGISTER_SIZE * ALPHA_NUM_ARG_REGS];
  int required_arg_regs;
  CORE_ADDR func_addr = find_function_addr (function, NULL);

  /* The ABI places the address of the called function in T12.  */
  regcache_cooked_write_signed (regcache, ALPHA_T12_REGNUM, func_addr);

  /* Set the return address register to point to the entry point
     of the program, where a breakpoint lies in wait.  */
  regcache_cooked_write_signed (regcache, ALPHA_RA_REGNUM, bp_addr);

  /* Lay out the arguments in memory.  */
  for (i = 0, m_arg = alpha_args; i < nargs; i++, m_arg++)
    {
      struct value *arg = args[i];
      struct type *arg_type = check_typedef (value_type (arg));

      /* Cast argument to long if necessary as the compiler does it too.  */
      switch (TYPE_CODE (arg_type))
	{
	case TYPE_CODE_INT:
	case TYPE_CODE_BOOL:
	case TYPE_CODE_CHAR:
	case TYPE_CODE_RANGE:
	case TYPE_CODE_ENUM:
	  if (TYPE_LENGTH (arg_type) == 4)
	    {
	      /* 32-bit values must be sign-extended to 64 bits
		 even if the base data type is unsigned.  */
	      arg_type = builtin_type_int32;
	      arg = value_cast (arg_type, arg);
	    }
	  if (TYPE_LENGTH (arg_type) < ALPHA_REGISTER_SIZE)
	    {
	      arg_type = builtin_type_int64;
	      arg = value_cast (arg_type, arg);
	    }
	  break;

	case TYPE_CODE_FLT:
	  /* "float" arguments loaded in registers must be passed in
	     register format, aka "double".  */
	  if (accumulate_size < sizeof (arg_reg_buffer)
	      && TYPE_LENGTH (arg_type) == 4)
	    {
	      arg_type = builtin_type_ieee_double_little;
	      arg = value_cast (arg_type, arg);
	    }
	  /* Tru64 5.1 has a 128-bit long double, and passes this by
	     invisible reference.  No one else uses this data type.  */
	  else if (TYPE_LENGTH (arg_type) == 16)
	    {
	      /* Allocate aligned storage.  */
	      sp = (sp & -16) - 16;

	      /* Write the real data into the stack.  */
	      write_memory (sp, value_contents (arg), 16);

	      /* Construct the indirection.  */
	      arg_type = lookup_pointer_type (arg_type);
	      arg = value_from_pointer (arg_type, sp);
	    }
	  break;

	case TYPE_CODE_COMPLEX:
	  /* ??? The ABI says that complex values are passed as two
	     separate scalar values.  This distinction only matters
	     for complex float.  However, GCC does not implement this.  */

	  /* Tru64 5.1 has a 128-bit long double, and passes this by
	     invisible reference.  */
	  if (TYPE_LENGTH (arg_type) == 32)
	    {
	      /* Allocate aligned storage.  */
	      sp = (sp & -16) - 16;

	      /* Write the real data into the stack.  */
	      write_memory (sp, value_contents (arg), 32);

	      /* Construct the indirection.  */
	      arg_type = lookup_pointer_type (arg_type);
	      arg = value_from_pointer (arg_type, sp);
	    }
	  break;

	default:
	  break;
	}
      m_arg->len = TYPE_LENGTH (arg_type);
      m_arg->offset = accumulate_size;
      accumulate_size = (accumulate_size + m_arg->len + 7) & ~7;
      m_arg->contents = value_contents_writeable (arg);
    }

  /* Determine required argument register loads, loading an argument register
     is expensive as it uses three ptrace calls.  */
  required_arg_regs = accumulate_size / 8;
  if (required_arg_regs > ALPHA_NUM_ARG_REGS)
    required_arg_regs = ALPHA_NUM_ARG_REGS;

  /* Make room for the arguments on the stack.  */
  if (accumulate_size < sizeof(arg_reg_buffer))
    accumulate_size = 0;
  else
    accumulate_size -= sizeof(arg_reg_buffer);
  sp -= accumulate_size;

  /* Keep sp aligned to a multiple of 16 as the ABI requires.  */
  sp &= ~15;

  /* `Push' arguments on the stack.  */
  for (i = nargs; m_arg--, --i >= 0;)
    {
      char *contents = m_arg->contents;
      int offset = m_arg->offset;
      int len = m_arg->len;

      /* Copy the bytes destined for registers into arg_reg_buffer.  */
      if (offset < sizeof(arg_reg_buffer))
	{
	  if (offset + len <= sizeof(arg_reg_buffer))
	    {
	      memcpy (arg_reg_buffer + offset, contents, len);
	      continue;
	    }
	  else
	    {
	      int tlen = sizeof(arg_reg_buffer) - offset;
	      memcpy (arg_reg_buffer + offset, contents, tlen);
	      offset += tlen;
	      contents += tlen;
	      len -= tlen;
	    }
	}

      /* Everything else goes to the stack.  */
      write_memory (sp + offset - sizeof(arg_reg_buffer), contents, len);
    }
  if (struct_return)
    store_unsigned_integer (arg_reg_buffer, ALPHA_REGISTER_SIZE, struct_addr);

  /* Load the argument registers.  */
  for (i = 0; i < required_arg_regs; i++)
    {
      regcache_cooked_write (regcache, ALPHA_A0_REGNUM + i,
			     arg_reg_buffer + i*ALPHA_REGISTER_SIZE);
      regcache_cooked_write (regcache, ALPHA_FPA0_REGNUM + i,
			     arg_reg_buffer + i*ALPHA_REGISTER_SIZE);
    }

  /* Finally, update the stack pointer.  */
  regcache_cooked_write_signed (regcache, ALPHA_SP_REGNUM, sp);

  return sp;
}

/* Extract from REGCACHE the value about to be returned from a function
   and copy it into VALBUF.  */

static void
alpha_extract_return_value (struct type *valtype, struct regcache *regcache,
			    gdb_byte *valbuf)
{
  int length = TYPE_LENGTH (valtype);
  char raw_buffer[ALPHA_REGISTER_SIZE];
  ULONGEST l;

  switch (TYPE_CODE (valtype))
    {
    case TYPE_CODE_FLT:
      switch (length)
	{
	case 4:
	  regcache_cooked_read (regcache, ALPHA_FP0_REGNUM, raw_buffer);
	  alpha_sts (valbuf, raw_buffer);
	  break;

	case 8:
	  regcache_cooked_read (regcache, ALPHA_FP0_REGNUM, valbuf);
	  break;

	case 16:
	  regcache_cooked_read_unsigned (regcache, ALPHA_V0_REGNUM, &l);
	  read_memory (l, valbuf, 16);
	  break;

	default:
	  internal_error (__FILE__, __LINE__, _("unknown floating point width"));
	}
      break;

    case TYPE_CODE_COMPLEX:
      switch (length)
	{
	case 8:
	  /* ??? This isn't correct wrt the ABI, but it's what GCC does.  */
	  regcache_cooked_read (regcache, ALPHA_FP0_REGNUM, valbuf);
	  break;

	case 16:
	  regcache_cooked_read (regcache, ALPHA_FP0_REGNUM, valbuf);
	  regcache_cooked_read (regcache, ALPHA_FP0_REGNUM+1,
				(char *)valbuf + 8);
	  break;

	case 32:
	  regcache_cooked_read_signed (regcache, ALPHA_V0_REGNUM, &l);
	  read_memory (l, valbuf, 32);
	  break;

	default:
	  internal_error (__FILE__, __LINE__, _("unknown floating point width"));
	}
      break;

    default:
      /* Assume everything else degenerates to an integer.  */
      regcache_cooked_read_unsigned (regcache, ALPHA_V0_REGNUM, &l);
      store_unsigned_integer (valbuf, length, l);
      break;
    }
}

/* Extract from REGCACHE the address of a structure about to be returned
   from a function.  */

static CORE_ADDR
alpha_extract_struct_value_address (struct regcache *regcache)
{
  ULONGEST addr;
  regcache_cooked_read_unsigned (regcache, ALPHA_V0_REGNUM, &addr);
  return addr;
}

/* Insert the given value into REGCACHE as if it was being 
   returned by a function.  */

static void
alpha_store_return_value (struct type *valtype, struct regcache *regcache,
			  const gdb_byte *valbuf)
{
  int length = TYPE_LENGTH (valtype);
  char raw_buffer[ALPHA_REGISTER_SIZE];
  ULONGEST l;

  switch (TYPE_CODE (valtype))
    {
    case TYPE_CODE_FLT:
      switch (length)
	{
	case 4:
	  alpha_lds (raw_buffer, valbuf);
	  regcache_cooked_write (regcache, ALPHA_FP0_REGNUM, raw_buffer);
	  break;

	case 8:
	  regcache_cooked_write (regcache, ALPHA_FP0_REGNUM, valbuf);
	  break;

	case 16:
	  /* FIXME: 128-bit long doubles are returned like structures:
	     by writing into indirect storage provided by the caller
	     as the first argument.  */
	  error (_("Cannot set a 128-bit long double return value."));

	default:
	  internal_error (__FILE__, __LINE__, _("unknown floating point width"));
	}
      break;

    case TYPE_CODE_COMPLEX:
      switch (length)
	{
	case 8:
	  /* ??? This isn't correct wrt the ABI, but it's what GCC does.  */
	  regcache_cooked_write (regcache, ALPHA_FP0_REGNUM, valbuf);
	  break;

	case 16:
	  regcache_cooked_write (regcache, ALPHA_FP0_REGNUM, valbuf);
	  regcache_cooked_write (regcache, ALPHA_FP0_REGNUM+1,
				 (const char *)valbuf + 8);
	  break;

	case 32:
	  /* FIXME: 128-bit long doubles are returned like structures:
	     by writing into indirect storage provided by the caller
	     as the first argument.  */
	  error (_("Cannot set a 128-bit long double return value."));

	default:
	  internal_error (__FILE__, __LINE__, _("unknown floating point width"));
	}
      break;

    default:
      /* Assume everything else degenerates to an integer.  */
      /* 32-bit values must be sign-extended to 64 bits
	 even if the base data type is unsigned.  */
      if (length == 4)
	valtype = builtin_type_int32;
      l = unpack_long (valtype, valbuf);
      regcache_cooked_write_unsigned (regcache, ALPHA_V0_REGNUM, l);
      break;
    }
}


static const unsigned char *
alpha_breakpoint_from_pc (CORE_ADDR *pcptr, int *lenptr)
{
  static const unsigned char alpha_breakpoint[] =
    { 0x80, 0, 0, 0 };	/* call_pal bpt */

  *lenptr = sizeof(alpha_breakpoint);
  return (alpha_breakpoint);
}


/* This returns the PC of the first insn after the prologue.
   If we can't find the prologue, then return 0.  */

CORE_ADDR
alpha_after_prologue (CORE_ADDR pc)
{
  struct symtab_and_line sal;
  CORE_ADDR func_addr, func_end;

  if (!find_pc_partial_function (pc, NULL, &func_addr, &func_end))
    return 0;

  sal = find_pc_line (func_addr, 0);
  if (sal.end < func_end)
    return sal.end;

  /* The line after the prologue is after the end of the function.  In this
     case, tell the caller to find the prologue the hard way.  */
  return 0;
}

/* Read an instruction from memory at PC, looking through breakpoints.  */

unsigned int
alpha_read_insn (CORE_ADDR pc)
{
  char buf[4];
  int status;

  status = deprecated_read_memory_nobpt (pc, buf, 4);
  if (status)
    memory_error (status, pc);
  return extract_unsigned_integer (buf, 4);
}

/* To skip prologues, I use this predicate.  Returns either PC itself
   if the code at PC does not look like a function prologue; otherwise
   returns an address that (if we're lucky) follows the prologue.  If
   LENIENT, then we must skip everything which is involved in setting
   up the frame (it's OK to skip more, just so long as we don't skip
   anything which might clobber the registers which are being saved.  */

static CORE_ADDR
alpha_skip_prologue (CORE_ADDR pc)
{
  unsigned long inst;
  int offset;
  CORE_ADDR post_prologue_pc;
  char buf[4];

  /* Silently return the unaltered pc upon memory errors.
     This could happen on OSF/1 if decode_line_1 tries to skip the
     prologue for quickstarted shared library functions when the
     shared library is not yet mapped in.
     Reading target memory is slow over serial lines, so we perform
     this check only if the target has shared libraries (which all
     Alpha targets do).  */
  if (target_read_memory (pc, buf, 4))
    return pc;

  /* See if we can determine the end of the prologue via the symbol table.
     If so, then return either PC, or the PC after the prologue, whichever
     is greater.  */

  post_prologue_pc = alpha_after_prologue (pc);
  if (post_prologue_pc != 0)
    return max (pc, post_prologue_pc);

  /* Can't determine prologue from the symbol table, need to examine
     instructions.  */

  /* Skip the typical prologue instructions. These are the stack adjustment
     instruction and the instructions that save registers on the stack
     or in the gcc frame.  */
  for (offset = 0; offset < 100; offset += 4)
    {
      inst = alpha_read_insn (pc + offset);

      if ((inst & 0xffff0000) == 0x27bb0000)	/* ldah $gp,n($t12) */
	continue;
      if ((inst & 0xffff0000) == 0x23bd0000)	/* lda $gp,n($gp) */
	continue;
      if ((inst & 0xffff0000) == 0x23de0000)	/* lda $sp,n($sp) */
	continue;
      if ((inst & 0xffe01fff) == 0x43c0153e)	/* subq $sp,n,$sp */
	continue;

      if (((inst & 0xfc1f0000) == 0xb41e0000		/* stq reg,n($sp) */
	   || (inst & 0xfc1f0000) == 0x9c1e0000)	/* stt reg,n($sp) */
	  && (inst & 0x03e00000) != 0x03e00000)		/* reg != $zero */
	continue;

      if (inst == 0x47de040f)			/* bis sp,sp,fp */
	continue;
      if (inst == 0x47fe040f)			/* bis zero,sp,fp */
	continue;

      break;
    }
  return pc + offset;
}


/* Figure out where the longjmp will land.
   We expect the first arg to be a pointer to the jmp_buf structure from
   which we extract the PC (JB_PC) that we will land at.  The PC is copied
   into the "pc".  This routine returns true on success.  */

static int
alpha_get_longjmp_target (CORE_ADDR *pc)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  CORE_ADDR jb_addr;
  char raw_buffer[ALPHA_REGISTER_SIZE];

  jb_addr = read_register (ALPHA_A0_REGNUM);

  if (target_read_memory (jb_addr + (tdep->jb_pc * tdep->jb_elt_size),
			  raw_buffer, tdep->jb_elt_size))
    return 0;

  *pc = extract_unsigned_integer (raw_buffer, tdep->jb_elt_size);
  return 1;
}


/* Frame unwinder for signal trampolines.  We use alpha tdep bits that
   describe the location and shape of the sigcontext structure.  After
   that, all registers are in memory, so it's easy.  */
/* ??? Shouldn't we be able to do this generically, rather than with
   OSABI data specific to Alpha?  */

struct alpha_sigtramp_unwind_cache
{
  CORE_ADDR sigcontext_addr;
};

static struct alpha_sigtramp_unwind_cache *
alpha_sigtramp_frame_unwind_cache (struct frame_info *next_frame,
				   void **this_prologue_cache)
{
  struct alpha_sigtramp_unwind_cache *info;
  struct gdbarch_tdep *tdep;

  if (*this_prologue_cache)
    return *this_prologue_cache;

  info = FRAME_OBSTACK_ZALLOC (struct alpha_sigtramp_unwind_cache);
  *this_prologue_cache = info;

  tdep = gdbarch_tdep (current_gdbarch);
  info->sigcontext_addr = tdep->sigcontext_addr (next_frame);

  return info;
}

/* Return the address of REGNUM in a sigtramp frame.  Since this is
   all arithmetic, it doesn't seem worthwhile to cache it.  */

static CORE_ADDR
alpha_sigtramp_register_address (CORE_ADDR sigcontext_addr, int regnum)
{ 
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);

  if (regnum >= 0 && regnum < 32)
    return sigcontext_addr + tdep->sc_regs_offset + regnum * 8;
  else if (regnum >= ALPHA_FP0_REGNUM && regnum < ALPHA_FP0_REGNUM + 32)
    return sigcontext_addr + tdep->sc_fpregs_offset + regnum * 8;
  else if (regnum == ALPHA_PC_REGNUM)
    return sigcontext_addr + tdep->sc_pc_offset; 

  return 0;
}

/* Given a GDB frame, determine the address of the calling function's
   frame.  This will be used to create a new GDB frame struct.  */

static void
alpha_sigtramp_frame_this_id (struct frame_info *next_frame,
			      void **this_prologue_cache,
			      struct frame_id *this_id)
{
  struct alpha_sigtramp_unwind_cache *info
    = alpha_sigtramp_frame_unwind_cache (next_frame, this_prologue_cache);
  struct gdbarch_tdep *tdep;
  CORE_ADDR stack_addr, code_addr;

  /* If the OSABI couldn't locate the sigcontext, give up.  */
  if (info->sigcontext_addr == 0)
    return;

  /* If we have dynamic signal trampolines, find their start.
     If we do not, then we must assume there is a symbol record
     that can provide the start address.  */
  tdep = gdbarch_tdep (current_gdbarch);
  if (tdep->dynamic_sigtramp_offset)
    {
      int offset;
      code_addr = frame_pc_unwind (next_frame);
      offset = tdep->dynamic_sigtramp_offset (code_addr);
      if (offset >= 0)
	code_addr -= offset;
      else
	code_addr = 0;
    }
  else
    code_addr = frame_func_unwind (next_frame);

  /* The stack address is trivially read from the sigcontext.  */
  stack_addr = alpha_sigtramp_register_address (info->sigcontext_addr,
						ALPHA_SP_REGNUM);
  stack_addr = get_frame_memory_unsigned (next_frame, stack_addr,
					  ALPHA_REGISTER_SIZE);

  *this_id = frame_id_build (stack_addr, code_addr);
}

/* Retrieve the value of REGNUM in FRAME.  Don't give up!  */

static void
alpha_sigtramp_frame_prev_register (struct frame_info *next_frame,
				    void **this_prologue_cache,
				    int regnum, int *optimizedp,
				    enum lval_type *lvalp, CORE_ADDR *addrp,
				    int *realnump, gdb_byte *bufferp)
{
  struct alpha_sigtramp_unwind_cache *info
    = alpha_sigtramp_frame_unwind_cache (next_frame, this_prologue_cache);
  CORE_ADDR addr;

  if (info->sigcontext_addr != 0)
    {
      /* All integer and fp registers are stored in memory.  */
      addr = alpha_sigtramp_register_address (info->sigcontext_addr, regnum);
      if (addr != 0)
	{
	  *optimizedp = 0;
	  *lvalp = lval_memory;
	  *addrp = addr;
	  *realnump = -1;
	  if (bufferp != NULL)
	    get_frame_memory (next_frame, addr, bufferp, ALPHA_REGISTER_SIZE);
	  return;
	}
    }

  /* This extra register may actually be in the sigcontext, but our
     current description of it in alpha_sigtramp_frame_unwind_cache
     doesn't include it.  Too bad.  Fall back on whatever's in the
     outer frame.  */
  frame_register (next_frame, regnum, optimizedp, lvalp, addrp,
		  realnump, bufferp);
}

static const struct frame_unwind alpha_sigtramp_frame_unwind = {
  SIGTRAMP_FRAME,
  alpha_sigtramp_frame_this_id,
  alpha_sigtramp_frame_prev_register
};

static const struct frame_unwind *
alpha_sigtramp_frame_sniffer (struct frame_info *next_frame)
{
  CORE_ADDR pc = frame_pc_unwind (next_frame);
  char *name;

  /* NOTE: cagney/2004-04-30: Do not copy/clone this code.  Instead
     look at tramp-frame.h and other simplier per-architecture
     sigtramp unwinders.  */

  /* We shouldn't even bother to try if the OSABI didn't register a
     sigcontext_addr handler or pc_in_sigtramp hander.  */
  if (gdbarch_tdep (current_gdbarch)->sigcontext_addr == NULL)
    return NULL;
  if (gdbarch_tdep (current_gdbarch)->pc_in_sigtramp == NULL)
    return NULL;

  /* Otherwise we should be in a signal frame.  */
  find_pc_partial_function (pc, &name, NULL, NULL);
  if (gdbarch_tdep (current_gdbarch)->pc_in_sigtramp (pc, name))
    return &alpha_sigtramp_frame_unwind;

  return NULL;
}

/* Fallback alpha frame unwinder.  Uses instruction scanning and knows
   something about the traditional layout of alpha stack frames.  */

struct alpha_heuristic_unwind_cache
{
  CORE_ADDR *saved_regs;
  CORE_ADDR vfp;
  CORE_ADDR start_pc;
  int return_reg;
};

/* Heuristic_proc_start may hunt through the text section for a long
   time across a 2400 baud serial line.  Allows the user to limit this
   search.  */
static unsigned int heuristic_fence_post = 0;

/* Attempt to locate the start of the function containing PC.  We assume that
   the previous function ends with an about_to_return insn.  Not foolproof by
   any means, since gcc is happy to put the epilogue in the middle of a
   function.  But we're guessing anyway...  */

static CORE_ADDR
alpha_heuristic_proc_start (CORE_ADDR pc)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  CORE_ADDR last_non_nop = pc;
  CORE_ADDR fence = pc - heuristic_fence_post;
  CORE_ADDR orig_pc = pc;
  CORE_ADDR func;

  if (pc == 0)
    return 0;

  /* First see if we can find the start of the function from minimal
     symbol information.  This can succeed with a binary that doesn't
     have debug info, but hasn't been stripped.  */
  func = get_pc_function_start (pc);
  if (func)
    return func;

  if (heuristic_fence_post == UINT_MAX
      || fence < tdep->vm_min_address)
    fence = tdep->vm_min_address;

  /* Search back for previous return; also stop at a 0, which might be
     seen for instance before the start of a code section.  Don't include
     nops, since this usually indicates padding between functions.  */
  for (pc -= 4; pc >= fence; pc -= 4)
    {
      unsigned int insn = alpha_read_insn (pc);
      switch (insn)
	{
	case 0:			/* invalid insn */
	case 0x6bfa8001:	/* ret $31,($26),1 */
	  return last_non_nop;

	case 0x2ffe0000:	/* unop: ldq_u $31,0($30) */
	case 0x47ff041f:	/* nop: bis $31,$31,$31 */
	  break;

	default:
	  last_non_nop = pc;
	  break;
	}
    }

  /* It's not clear to me why we reach this point when stopping quietly,
     but with this test, at least we don't print out warnings for every
     child forked (eg, on decstation).  22apr93 rich@cygnus.com.  */
  if (stop_soon == NO_STOP_QUIETLY)
    {
      static int blurb_printed = 0;

      if (fence == tdep->vm_min_address)
	warning (_("Hit beginning of text section without finding \
enclosing function for address 0x%s"), paddr_nz (orig_pc));
      else
	warning (_("Hit heuristic-fence-post without finding \
enclosing function for address 0x%s"), paddr_nz (orig_pc));

      if (!blurb_printed)
	{
	  printf_filtered (_("\
This warning occurs if you are debugging a function without any symbols\n\
(for example, in a stripped executable).  In that case, you may wish to\n\
increase the size of the search with the `set heuristic-fence-post' command.\n\
\n\
Otherwise, you told GDB there was a function where there isn't one, or\n\
(more likely) you have encountered a bug in GDB.\n"));
	  blurb_printed = 1;
	}
    }

  return 0;
}

static struct alpha_heuristic_unwind_cache *
alpha_heuristic_frame_unwind_cache (struct frame_info *next_frame,
				    void **this_prologue_cache,
				    CORE_ADDR start_pc)
{
  struct alpha_heuristic_unwind_cache *info;
  ULONGEST val;
  CORE_ADDR limit_pc, cur_pc;
  int frame_reg, frame_size, return_reg, reg;

  if (*this_prologue_cache)
    return *this_prologue_cache;

  info = FRAME_OBSTACK_ZALLOC (struct alpha_heuristic_unwind_cache);
  *this_prologue_cache = info;
  info->saved_regs = frame_obstack_zalloc (SIZEOF_FRAME_SAVED_REGS);

  limit_pc = frame_pc_unwind (next_frame);
  if (start_pc == 0)
    start_pc = alpha_heuristic_proc_start (limit_pc);
  info->start_pc = start_pc;

  frame_reg = ALPHA_SP_REGNUM;
  frame_size = 0;
  return_reg = -1;

  /* If we've identified a likely place to start, do code scanning.  */
  if (start_pc != 0)
    {
      /* Limit the forward search to 50 instructions.  */
      if (start_pc + 200 < limit_pc)
	limit_pc = start_pc + 200;

      for (cur_pc = start_pc; cur_pc < limit_pc; cur_pc += 4)
	{
	  unsigned int word = alpha_read_insn (cur_pc);

	  if ((word & 0xffff0000) == 0x23de0000)	/* lda $sp,n($sp) */
	    {
	      if (word & 0x8000)
		{
		  /* Consider only the first stack allocation instruction
		     to contain the static size of the frame. */
		  if (frame_size == 0)
		    frame_size = (-word) & 0xffff;
		}
	      else
		{
		  /* Exit loop if a positive stack adjustment is found, which
		     usually means that the stack cleanup code in the function
		     epilogue is reached.  */
		  break;
		}
	    }
	  else if ((word & 0xfc1f0000) == 0xb41e0000)	/* stq reg,n($sp) */
	    {
	      reg = (word & 0x03e00000) >> 21;

              /* Ignore this instruction if we have already encountered
                 an instruction saving the same register earlier in the
                 function code.  The current instruction does not tell
                 us where the original value upon function entry is saved.
                 All it says is that the function we are scanning reused
                 that register for some computation of its own, and is now
                 saving its result.  */
              if (info->saved_regs[reg])
                continue;

	      if (reg == 31)
		continue;

	      /* Do not compute the address where the register was saved yet,
		 because we don't know yet if the offset will need to be
		 relative to $sp or $fp (we can not compute the address
		 relative to $sp if $sp is updated during the execution of
		 the current subroutine, for instance when doing some alloca).
		 So just store the offset for the moment, and compute the
		 address later when we know whether this frame has a frame
		 pointer or not.  */
	      /* Hack: temporarily add one, so that the offset is non-zero
		 and we can tell which registers have save offsets below.  */
	      info->saved_regs[reg] = (word & 0xffff) + 1;

	      /* Starting with OSF/1-3.2C, the system libraries are shipped
		 without local symbols, but they still contain procedure
		 descriptors without a symbol reference. GDB is currently
		 unable to find these procedure descriptors and uses
		 heuristic_proc_desc instead.
		 As some low level compiler support routines (__div*, __add*)
		 use a non-standard return address register, we have to
		 add some heuristics to determine the return address register,
		 or stepping over these routines will fail.
		 Usually the return address register is the first register
		 saved on the stack, but assembler optimization might
		 rearrange the register saves.
		 So we recognize only a few registers (t7, t9, ra) within
		 the procedure prologue as valid return address registers.
		 If we encounter a return instruction, we extract the
		 the return address register from it.

		 FIXME: Rewriting GDB to access the procedure descriptors,
		 e.g. via the minimal symbol table, might obviate this hack.  */
	      if (return_reg == -1
		  && cur_pc < (start_pc + 80)
		  && (reg == ALPHA_T7_REGNUM
		      || reg == ALPHA_T9_REGNUM
		      || reg == ALPHA_RA_REGNUM))
		return_reg = reg;
	    }
	  else if ((word & 0xffe0ffff) == 0x6be08001)	/* ret zero,reg,1 */
	    return_reg = (word >> 16) & 0x1f;
	  else if (word == 0x47de040f)			/* bis sp,sp,fp */
	    frame_reg = ALPHA_GCC_FP_REGNUM;
	  else if (word == 0x47fe040f)			/* bis zero,sp,fp */
	    frame_reg = ALPHA_GCC_FP_REGNUM;
	}

      /* If we haven't found a valid return address register yet, keep
	 searching in the procedure prologue.  */
      if (return_reg == -1)
	{
	  while (cur_pc < (limit_pc + 80) && cur_pc < (start_pc + 80))
	    {
	      unsigned int word = alpha_read_insn (cur_pc);

	      if ((word & 0xfc1f0000) == 0xb41e0000)	/* stq reg,n($sp) */
		{
		  reg = (word & 0x03e00000) >> 21;
		  if (reg == ALPHA_T7_REGNUM
		      || reg == ALPHA_T9_REGNUM
		      || reg == ALPHA_RA_REGNUM)
		    {
		      return_reg = reg;
		      break;
		    }
		}
	      else if ((word & 0xffe0ffff) == 0x6be08001) /* ret zero,reg,1 */
		{
		  return_reg = (word >> 16) & 0x1f;
		  break;
		}

	      cur_pc += 4;
	    }
	}
    }

  /* Failing that, do default to the customary RA.  */
  if (return_reg == -1)
    return_reg = ALPHA_RA_REGNUM;
  info->return_reg = return_reg;

  frame_unwind_unsigned_register (next_frame, frame_reg, &val);
  info->vfp = val + frame_size;

  /* Convert offsets to absolute addresses.  See above about adding
     one to the offsets to make all detected offsets non-zero.  */
  for (reg = 0; reg < ALPHA_NUM_REGS; ++reg)
    if (info->saved_regs[reg])
      info->saved_regs[reg] += val - 1;

  return info;
}

/* Given a GDB frame, determine the address of the calling function's
   frame.  This will be used to create a new GDB frame struct.  */

static void
alpha_heuristic_frame_this_id (struct frame_info *next_frame,
				 void **this_prologue_cache,
				 struct frame_id *this_id)
{
  struct alpha_heuristic_unwind_cache *info
    = alpha_heuristic_frame_unwind_cache (next_frame, this_prologue_cache, 0);

  *this_id = frame_id_build (info->vfp, info->start_pc);
}

/* Retrieve the value of REGNUM in FRAME.  Don't give up!  */

static void
alpha_heuristic_frame_prev_register (struct frame_info *next_frame,
				     void **this_prologue_cache,
				     int regnum, int *optimizedp,
				     enum lval_type *lvalp, CORE_ADDR *addrp,
				     int *realnump, gdb_byte *bufferp)
{
  struct alpha_heuristic_unwind_cache *info
    = alpha_heuristic_frame_unwind_cache (next_frame, this_prologue_cache, 0);

  /* The PC of the previous frame is stored in the link register of
     the current frame.  Frob regnum so that we pull the value from
     the correct place.  */
  if (regnum == ALPHA_PC_REGNUM)
    regnum = info->return_reg;
  
  /* For all registers known to be saved in the current frame, 
     do the obvious and pull the value out.  */
  if (info->saved_regs[regnum])
    {
      *optimizedp = 0;
      *lvalp = lval_memory;
      *addrp = info->saved_regs[regnum];
      *realnump = -1;
      if (bufferp != NULL)
	get_frame_memory (next_frame, *addrp, bufferp, ALPHA_REGISTER_SIZE);
      return;
    }

  /* The stack pointer of the previous frame is computed by popping
     the current stack frame.  */
  if (regnum == ALPHA_SP_REGNUM)
    {
      *optimizedp = 0;
      *lvalp = not_lval;
      *addrp = 0;
      *realnump = -1;
      if (bufferp != NULL)
	store_unsigned_integer (bufferp, ALPHA_REGISTER_SIZE, info->vfp);
      return;
    }

  /* Otherwise assume the next frame has the same register value.  */
  frame_register_unwind (next_frame, regnum, optimizedp, lvalp, addrp,
                         realnump, bufferp);
}

static const struct frame_unwind alpha_heuristic_frame_unwind = {
  NORMAL_FRAME,
  alpha_heuristic_frame_this_id,
  alpha_heuristic_frame_prev_register
};

static const struct frame_unwind *
alpha_heuristic_frame_sniffer (struct frame_info *next_frame)
{
  return &alpha_heuristic_frame_unwind;
}

static CORE_ADDR
alpha_heuristic_frame_base_address (struct frame_info *next_frame,
				    void **this_prologue_cache)
{
  struct alpha_heuristic_unwind_cache *info
    = alpha_heuristic_frame_unwind_cache (next_frame, this_prologue_cache, 0);

  return info->vfp;
}

static const struct frame_base alpha_heuristic_frame_base = {
  &alpha_heuristic_frame_unwind,
  alpha_heuristic_frame_base_address,
  alpha_heuristic_frame_base_address,
  alpha_heuristic_frame_base_address
};

/* Just like reinit_frame_cache, but with the right arguments to be
   callable as an sfunc.  Used by the "set heuristic-fence-post" command.  */

static void
reinit_frame_cache_sfunc (char *args, int from_tty, struct cmd_list_element *c)
{
  reinit_frame_cache ();
}


/* Assuming NEXT_FRAME->prev is a dummy, return the frame ID of that
   dummy frame.  The frame ID's base needs to match the TOS value
   saved by save_dummy_frame_tos(), and the PC match the dummy frame's
   breakpoint.  */

static struct frame_id
alpha_unwind_dummy_id (struct gdbarch *gdbarch, struct frame_info *next_frame)
{
  ULONGEST base;
  frame_unwind_unsigned_register (next_frame, ALPHA_SP_REGNUM, &base);
  return frame_id_build (base, frame_pc_unwind (next_frame));
}

static CORE_ADDR
alpha_unwind_pc (struct gdbarch *gdbarch, struct frame_info *next_frame)
{
  ULONGEST pc;
  frame_unwind_unsigned_register (next_frame, ALPHA_PC_REGNUM, &pc);
  return pc;
}


/* Helper routines for alpha*-nat.c files to move register sets to and
   from core files.  The UNIQUE pointer is allowed to be NULL, as most
   targets don't supply this value in their core files.  */

void
alpha_supply_int_regs (int regno, const void *r0_r30,
		       const void *pc, const void *unique)
{
  int i;

  for (i = 0; i < 31; ++i)
    if (regno == i || regno == -1)
      regcache_raw_supply (current_regcache, i, (const char *)r0_r30 + i*8);

  if (regno == ALPHA_ZERO_REGNUM || regno == -1)
    regcache_raw_supply (current_regcache, ALPHA_ZERO_REGNUM, NULL);

  if (regno == ALPHA_PC_REGNUM || regno == -1)
    regcache_raw_supply (current_regcache, ALPHA_PC_REGNUM, pc);

  if (regno == ALPHA_UNIQUE_REGNUM || regno == -1)
    regcache_raw_supply (current_regcache, ALPHA_UNIQUE_REGNUM, unique);
}

void
alpha_fill_int_regs (int regno, void *r0_r30, void *pc, void *unique)
{
  int i;

  for (i = 0; i < 31; ++i)
    if (regno == i || regno == -1)
      regcache_raw_collect (current_regcache, i, (char *)r0_r30 + i*8);

  if (regno == ALPHA_PC_REGNUM || regno == -1)
    regcache_raw_collect (current_regcache, ALPHA_PC_REGNUM, pc);

  if (unique && (regno == ALPHA_UNIQUE_REGNUM || regno == -1))
    regcache_raw_collect (current_regcache, ALPHA_UNIQUE_REGNUM, unique);
}

void
alpha_supply_fp_regs (int regno, const void *f0_f30, const void *fpcr)
{
  int i;

  for (i = ALPHA_FP0_REGNUM; i < ALPHA_FP0_REGNUM + 31; ++i)
    if (regno == i || regno == -1)
      regcache_raw_supply (current_regcache, i,
			   (const char *)f0_f30 + (i - ALPHA_FP0_REGNUM) * 8);

  if (regno == ALPHA_FPCR_REGNUM || regno == -1)
    regcache_raw_supply (current_regcache, ALPHA_FPCR_REGNUM, fpcr);
}

void
alpha_fill_fp_regs (int regno, void *f0_f30, void *fpcr)
{
  int i;

  for (i = ALPHA_FP0_REGNUM; i < ALPHA_FP0_REGNUM + 31; ++i)
    if (regno == i || regno == -1)
      regcache_raw_collect (current_regcache, i,
			    (char *)f0_f30 + (i - ALPHA_FP0_REGNUM) * 8);

  if (regno == ALPHA_FPCR_REGNUM || regno == -1)
    regcache_raw_collect (current_regcache, ALPHA_FPCR_REGNUM, fpcr);
}



/* Return nonzero if the G_floating register value in REG is equal to
   zero for FP control instructions.  */
   
static int
fp_register_zero_p (LONGEST reg)
{
  /* Check that all bits except the sign bit are zero.  */
  const LONGEST zero_mask = ((LONGEST) 1 << 63) ^ -1;

  return ((reg & zero_mask) == 0);
}

/* Return the value of the sign bit for the G_floating register
   value held in REG.  */

static int
fp_register_sign_bit (LONGEST reg)
{
  const LONGEST sign_mask = (LONGEST) 1 << 63;

  return ((reg & sign_mask) != 0);
}

/* alpha_software_single_step() is called just before we want to resume
   the inferior, if we want to single-step it but there is no hardware
   or kernel single-step support (NetBSD on Alpha, for example).  We find
   the target of the coming instruction and breakpoint it.

   single_step is also called just after the inferior stops.  If we had
   set up a simulated single-step, we undo our damage.  */

static CORE_ADDR
alpha_next_pc (CORE_ADDR pc)
{
  unsigned int insn;
  unsigned int op;
  int regno;
  int offset;
  LONGEST rav;
  char reg[8];

  insn = alpha_read_insn (pc);

  /* Opcode is top 6 bits. */
  op = (insn >> 26) & 0x3f;

  if (op == 0x1a)
    {
      /* Jump format: target PC is:
	 RB & ~3  */
      return (read_register ((insn >> 16) & 0x1f) & ~3);
    }

  if ((op & 0x30) == 0x30)
    {
      /* Branch format: target PC is:
	 (new PC) + (4 * sext(displacement))  */
      if (op == 0x30 ||		/* BR */
	  op == 0x34)		/* BSR */
	{
 branch_taken:
          offset = (insn & 0x001fffff);
	  if (offset & 0x00100000)
	    offset  |= 0xffe00000;
	  offset *= 4;
	  return (pc + 4 + offset);
	}

      /* Need to determine if branch is taken; read RA.  */
      regno = (insn >> 21) & 0x1f;
      switch (op)
        {
          case 0x31:              /* FBEQ */
          case 0x36:              /* FBGE */
          case 0x37:              /* FBGT */
          case 0x33:              /* FBLE */
          case 0x32:              /* FBLT */
          case 0x35:              /* FBNE */
            regno += FP0_REGNUM;
	}
      
      regcache_cooked_read (current_regcache, regno, reg);
      rav = extract_signed_integer (reg, 8);

      switch (op)
	{
	case 0x38:		/* BLBC */
	  if ((rav & 1) == 0)
	    goto branch_taken;
	  break;
	case 0x3c:		/* BLBS */
	  if (rav & 1)
	    goto branch_taken;
	  break;
	case 0x39:		/* BEQ */
	  if (rav == 0)
	    goto branch_taken;
	  break;
	case 0x3d:		/* BNE */
	  if (rav != 0)
	    goto branch_taken;
	  break;
	case 0x3a:		/* BLT */
	  if (rav < 0)
	    goto branch_taken;
	  break;
	case 0x3b:		/* BLE */
	  if (rav <= 0)
	    goto branch_taken;
	  break;
	case 0x3f:		/* BGT */
	  if (rav > 0)
	    goto branch_taken;
	  break;
	case 0x3e:		/* BGE */
	  if (rav >= 0)
	    goto branch_taken;
	  break;

        /* Floating point branches.  */
        
        case 0x31:              /* FBEQ */
          if (fp_register_zero_p (rav))
            goto branch_taken;
          break;
        case 0x36:              /* FBGE */
          if (fp_register_sign_bit (rav) == 0 || fp_register_zero_p (rav))
            goto branch_taken;
          break;
        case 0x37:              /* FBGT */
          if (fp_register_sign_bit (rav) == 0 && ! fp_register_zero_p (rav))
            goto branch_taken;
          break;
        case 0x33:              /* FBLE */
          if (fp_register_sign_bit (rav) == 1 || fp_register_zero_p (rav))
            goto branch_taken;
          break;
        case 0x32:              /* FBLT */
          if (fp_register_sign_bit (rav) == 1 && ! fp_register_zero_p (rav))
            goto branch_taken;
          break;
        case 0x35:              /* FBNE */
          if (! fp_register_zero_p (rav))
            goto branch_taken;
          break;
	}
    }

  /* Not a branch or branch not taken; target PC is:
     pc + 4  */
  return (pc + 4);
}

void
alpha_software_single_step (enum target_signal sig, int insert_breakpoints_p)
{
  static CORE_ADDR next_pc;
  typedef char binsn_quantum[BREAKPOINT_MAX];
  static binsn_quantum break_mem;
  CORE_ADDR pc;

  if (insert_breakpoints_p)
    {
      pc = read_pc ();
      next_pc = alpha_next_pc (pc);

      target_insert_breakpoint (next_pc, break_mem);
    }
  else
    {
      target_remove_breakpoint (next_pc, break_mem);
      write_pc (next_pc);
    }
}


/* Initialize the current architecture based on INFO.  If possible, re-use an
   architecture from ARCHES, which is a list of architectures already created
   during this debugging session.

   Called e.g. at program startup, when reading a core file, and when reading
   a binary file.  */

static struct gdbarch *
alpha_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
{
  struct gdbarch_tdep *tdep;
  struct gdbarch *gdbarch;

  /* Try to determine the ABI of the object we are loading.  */
  if (info.abfd != NULL && info.osabi == GDB_OSABI_UNKNOWN)
    {
      /* If it's an ECOFF file, assume it's OSF/1.  */
      if (bfd_get_flavour (info.abfd) == bfd_target_ecoff_flavour)
	info.osabi = GDB_OSABI_OSF1;
    }

  /* Find a candidate among extant architectures.  */
  arches = gdbarch_list_lookup_by_info (arches, &info);
  if (arches != NULL)
    return arches->gdbarch;

  tdep = xmalloc (sizeof (struct gdbarch_tdep));
  gdbarch = gdbarch_alloc (&info, tdep);

  /* Lowest text address.  This is used by heuristic_proc_start()
     to decide when to stop looking.  */
  tdep->vm_min_address = (CORE_ADDR) 0x120000000LL;

  tdep->dynamic_sigtramp_offset = NULL;
  tdep->sigcontext_addr = NULL;
  tdep->sc_pc_offset = 2 * 8;
  tdep->sc_regs_offset = 4 * 8;
  tdep->sc_fpregs_offset = tdep->sc_regs_offset + 32 * 8 + 8;

  tdep->jb_pc = -1;	/* longjmp support not enabled by default  */

  /* Type sizes */
  set_gdbarch_short_bit (gdbarch, 16);
  set_gdbarch_int_bit (gdbarch, 32);
  set_gdbarch_long_bit (gdbarch, 64);
  set_gdbarch_long_long_bit (gdbarch, 64);
  set_gdbarch_float_bit (gdbarch, 32);
  set_gdbarch_double_bit (gdbarch, 64);
  set_gdbarch_long_double_bit (gdbarch, 64);
  set_gdbarch_ptr_bit (gdbarch, 64);

  /* Register info */
  set_gdbarch_num_regs (gdbarch, ALPHA_NUM_REGS);
  set_gdbarch_sp_regnum (gdbarch, ALPHA_SP_REGNUM);
  set_gdbarch_pc_regnum (gdbarch, ALPHA_PC_REGNUM);
  set_gdbarch_fp0_regnum (gdbarch, ALPHA_FP0_REGNUM);

  set_gdbarch_register_name (gdbarch, alpha_register_name);
  set_gdbarch_deprecated_register_byte (gdbarch, alpha_register_byte);
  set_gdbarch_register_type (gdbarch, alpha_register_type);

  set_gdbarch_cannot_fetch_register (gdbarch, alpha_cannot_fetch_register);
  set_gdbarch_cannot_store_register (gdbarch, alpha_cannot_store_register);

  set_gdbarch_convert_register_p (gdbarch, alpha_convert_register_p);
  set_gdbarch_register_to_value (gdbarch, alpha_register_to_value);
  set_gdbarch_value_to_register (gdbarch, alpha_value_to_register);

  set_gdbarch_register_reggroup_p (gdbarch, alpha_register_reggroup_p);

  /* Prologue heuristics.  */
  set_gdbarch_skip_prologue (gdbarch, alpha_skip_prologue);

  /* Disassembler.  */
  set_gdbarch_print_insn (gdbarch, print_insn_alpha);

  /* Call info.  */

  set_gdbarch_deprecated_use_struct_convention (gdbarch, always_use_struct_convention);
  set_gdbarch_extract_return_value (gdbarch, alpha_extract_return_value);
  set_gdbarch_store_return_value (gdbarch, alpha_store_return_value);
  set_gdbarch_deprecated_extract_struct_value_address (gdbarch, alpha_extract_struct_value_address);

  /* Settings for calling functions in the inferior.  */
  set_gdbarch_push_dummy_call (gdbarch, alpha_push_dummy_call);

  /* Methods for saving / extracting a dummy frame's ID.  */
  set_gdbarch_unwind_dummy_id (gdbarch, alpha_unwind_dummy_id);

  /* Return the unwound PC value.  */
  set_gdbarch_unwind_pc (gdbarch, alpha_unwind_pc);

  set_gdbarch_inner_than (gdbarch, core_addr_lessthan);
  set_gdbarch_skip_trampoline_code (gdbarch, find_solib_trampoline_target);

  set_gdbarch_breakpoint_from_pc (gdbarch, alpha_breakpoint_from_pc);
  set_gdbarch_decr_pc_after_break (gdbarch, 4);

  /* Hook in ABI-specific overrides, if they have been registered.  */
  gdbarch_init_osabi (info, gdbarch);

  /* Now that we have tuned the configuration, set a few final things
     based on what the OS ABI has told us.  */

  if (tdep->jb_pc >= 0)
    set_gdbarch_get_longjmp_target (gdbarch, alpha_get_longjmp_target);

  frame_unwind_append_sniffer (gdbarch, alpha_sigtramp_frame_sniffer);
  frame_unwind_append_sniffer (gdbarch, alpha_heuristic_frame_sniffer);

  frame_base_set_default (gdbarch, &alpha_heuristic_frame_base);

  return gdbarch;
}

void
alpha_dwarf2_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
{
  frame_unwind_append_sniffer (gdbarch, dwarf2_frame_sniffer);
  frame_base_append_sniffer (gdbarch, dwarf2_frame_base_sniffer);
}

extern initialize_file_ftype _initialize_alpha_tdep; /* -Wmissing-prototypes */

void
_initialize_alpha_tdep (void)
{
  struct cmd_list_element *c;

  gdbarch_register (bfd_arch_alpha, alpha_gdbarch_init, NULL);

  /* Let the user set the fence post for heuristic_proc_start.  */

  /* We really would like to have both "0" and "unlimited" work, but
     command.c doesn't deal with that.  So make it a var_zinteger
     because the user can always use "999999" or some such for unlimited.  */
  /* We need to throw away the frame cache when we set this, since it
     might change our ability to get backtraces.  */
  add_setshow_zinteger_cmd ("heuristic-fence-post", class_support,
			    &heuristic_fence_post, _("\
Set the distance searched for the start of a function."), _("\
Show the distance searched for the start of a function."), _("\
If you are debugging a stripped executable, GDB needs to search through the\n\
program for the start of a function.  This command sets the distance of the\n\
search.  The only need to set it is when debugging a stripped executable."),
			    reinit_frame_cache_sfunc,
			    NULL, /* FIXME: i18n: The distance searched for the start of a function is \"%d\".  */
			    &setlist, &showlist);
}