aboutsummaryrefslogtreecommitdiff
path: root/gdb/alpha-tdep.c
blob: a50000ede8c26c2e9a03f7fb800d0e203c3d73a2 (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
/* Target-dependent code for the ALPHA architecture, for GDB, the GNU Debugger.
   Copyright 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002
   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 "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 "doublest.h"

/* FIXME: Some of this code should perhaps be merged with mips-tdep.c.  */

/* Prototypes for local functions. */

static alpha_extra_func_info_t push_sigtramp_desc (CORE_ADDR low_addr);

static CORE_ADDR read_next_frame_reg (struct frame_info *, int);

static CORE_ADDR heuristic_proc_start (CORE_ADDR);

static alpha_extra_func_info_t heuristic_proc_desc (CORE_ADDR,
						    CORE_ADDR,
						    struct frame_info *);

static alpha_extra_func_info_t find_proc_desc (CORE_ADDR,
					       struct frame_info *);

#if 0
static int alpha_in_lenient_prologue (CORE_ADDR, CORE_ADDR);
#endif

static void reinit_frame_cache_sfunc (char *, int, struct cmd_list_element *);

static CORE_ADDR after_prologue (CORE_ADDR pc,
				 alpha_extra_func_info_t proc_desc);

static int alpha_in_prologue (CORE_ADDR pc,
			      alpha_extra_func_info_t proc_desc);

static int alpha_about_to_return (CORE_ADDR pc);

void _initialize_alpha_tdep (void);

/* 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;
/* *INDENT-OFF* */
/* Layout of a stack frame on the alpha:

                |				|
 pdr members:	|  7th ... nth arg,		|
                |  `pushed' by caller.		|
                |				|
----------------|-------------------------------|<--  old_sp == vfp
   ^  ^  ^  ^	|				|
   |  |  |  |	|				|
   |  |localoff	|  Copies of 1st .. 6th		|
   |  |  |  |	|  argument if necessary.	|
   |  |  |  v	|				|
   |  |  |  ---	|-------------------------------|<-- FRAME_LOCALS_ADDRESS
   |  |  |      |				|
   |  |  |      |  Locals and temporaries.	|
   |  |  |      |				|
   |  |  |      |-------------------------------|
   |  |  |      |				|
   |-fregoffset	|  Saved float registers.	|
   |  |  |      |  F9				|
   |  |  |      |   .				|
   |  |  |      |   .				|
   |  |  |      |  F2				|
   |  |  v      |				|
   |  |  -------|-------------------------------|
   |  |         |				|
   |  |         |  Saved registers.		|
   |  |         |  S6				|
   |-regoffset	|   .				|
   |  |         |   .				|
   |  |         |  S0				|
   |  |         |  pdr.pcreg			|
   |  v         |				|
   |  ----------|-------------------------------|
   |            |				|
 frameoffset    |  Argument build area, gets	|
   |            |  7th ... nth arg for any	|
   |            |  called procedure.		|
   v            |  				|
   -------------|-------------------------------|<-- sp
                |				|
*/
/* *INDENT-ON* */



#define PROC_LOW_ADDR(proc) ((proc)->pdr.adr)	/* least address */
/* These next two fields are kind of being hijacked.  I wonder if
   iline is too small for the values it needs to hold, if GDB is
   running on a 32-bit host.  */
#define PROC_HIGH_ADDR(proc) ((proc)->pdr.iline)	/* upper address bound */
#define PROC_DUMMY_FRAME(proc) ((proc)->pdr.cbLineOffset)	/*CALL_DUMMY frame */
#define PROC_FRAME_OFFSET(proc) ((proc)->pdr.frameoffset)
#define PROC_FRAME_REG(proc) ((proc)->pdr.framereg)
#define PROC_REG_MASK(proc) ((proc)->pdr.regmask)
#define PROC_FREG_MASK(proc) ((proc)->pdr.fregmask)
#define PROC_REG_OFFSET(proc) ((proc)->pdr.regoffset)
#define PROC_FREG_OFFSET(proc) ((proc)->pdr.fregoffset)
#define PROC_PC_REG(proc) ((proc)->pdr.pcreg)
#define PROC_LOCALOFF(proc) ((proc)->pdr.localoff)
#define PROC_SYMBOL(proc) (*(struct symbol**)&(proc)->pdr.isym)
#define _PROC_MAGIC_ 0x0F0F0F0F
#define PROC_DESC_IS_DUMMY(proc) ((proc)->pdr.isym == _PROC_MAGIC_)
#define SET_PROC_DESC_IS_DUMMY(proc) ((proc)->pdr.isym = _PROC_MAGIC_)

struct linked_proc_info
  {
    struct alpha_extra_func_info info;
    struct linked_proc_info *next;
  }
 *linked_proc_desc_table = NULL;

int
alpha_osf_in_sigtramp (CORE_ADDR pc, char *func_name)
{
  return (func_name != NULL && STREQ ("__sigtramp", func_name));
}

/* Under GNU/Linux, signal handler invocations can be identified by the
   designated code sequence that is used to return from a signal
   handler.  In particular, the return address of a signal handler
   points to the following sequence (the first instruction is quadword
   aligned):

   bis $30,$30,$16
   addq $31,0x67,$0
   call_pal callsys

   Each instruction has a unique encoding, so we simply attempt to
   match the instruction the pc is pointing to with any of the above
   instructions.  If there is a hit, we know the offset to the start
   of the designated sequence and can then check whether we really are
   executing in a designated sequence.  If not, -1 is returned,
   otherwise the offset from the start of the desingated sequence is
   returned.

   There is a slight chance of false hits: code could jump into the
   middle of the designated sequence, in which case there is no
   guarantee that we are in the middle of a sigreturn syscall.  Don't
   think this will be a problem in praxis, though.
 */

#ifndef TM_LINUXALPHA_H
/* HACK: Provide a prototype when compiling this file for non
   linuxalpha targets. */
long alpha_linux_sigtramp_offset (CORE_ADDR pc);
#endif
long
alpha_linux_sigtramp_offset (CORE_ADDR pc)
{
  unsigned int i[3], w;
  long off;

  if (read_memory_nobpt (pc, (char *) &w, 4) != 0)
    return -1;

  off = -1;
  switch (w)
    {
    case 0x47de0410:
      off = 0;
      break;			/* bis $30,$30,$16 */
    case 0x43ecf400:
      off = 4;
      break;			/* addq $31,0x67,$0 */
    case 0x00000083:
      off = 8;
      break;			/* call_pal callsys */
    default:
      return -1;
    }
  pc -= off;
  if (pc & 0x7)
    {
      /* designated sequence is not quadword aligned */
      return -1;
    }

  if (read_memory_nobpt (pc, (char *) i, sizeof (i)) != 0)
    return -1;

  if (i[0] == 0x47de0410 && i[1] == 0x43ecf400 && i[2] == 0x00000083)
    return off;

  return -1;
}


/* Under OSF/1, the __sigtramp routine is frameless and has a frame
   size of zero, but we are able to backtrace through it.  */
CORE_ADDR
alpha_osf_skip_sigtramp_frame (struct frame_info *frame, CORE_ADDR pc)
{
  char *name;
  find_pc_partial_function (pc, &name, (CORE_ADDR *) NULL, (CORE_ADDR *) NULL);
  if (IN_SIGTRAMP (pc, name))
    return frame->frame;
  else
    return 0;
}


/* Dynamically create a signal-handler caller procedure descriptor for
   the signal-handler return code starting at address LOW_ADDR.  The
   descriptor is added to the linked_proc_desc_table.  */

static alpha_extra_func_info_t
push_sigtramp_desc (CORE_ADDR low_addr)
{
  struct linked_proc_info *link;
  alpha_extra_func_info_t proc_desc;

  link = (struct linked_proc_info *)
    xmalloc (sizeof (struct linked_proc_info));
  link->next = linked_proc_desc_table;
  linked_proc_desc_table = link;

  proc_desc = &link->info;

  proc_desc->numargs = 0;
  PROC_LOW_ADDR (proc_desc) = low_addr;
  PROC_HIGH_ADDR (proc_desc) = low_addr + 3 * 4;
  PROC_DUMMY_FRAME (proc_desc) = 0;
  PROC_FRAME_OFFSET (proc_desc) = 0x298;	/* sizeof(struct sigcontext_struct) */
  PROC_FRAME_REG (proc_desc) = SP_REGNUM;
  PROC_REG_MASK (proc_desc) = 0xffff;
  PROC_FREG_MASK (proc_desc) = 0xffff;
  PROC_PC_REG (proc_desc) = 26;
  PROC_LOCALOFF (proc_desc) = 0;
  SET_PROC_DESC_IS_DYN_SIGTRAMP (proc_desc);
  return (proc_desc);
}


char *
alpha_register_name (int regno)
{
  static char *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",   "vfp",
  };

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

int
alpha_cannot_fetch_register (int regno)
{
  return (regno == FP_REGNUM || regno == ZERO_REGNUM);
}

int
alpha_cannot_store_register (int regno)
{
  return (regno == FP_REGNUM || regno == ZERO_REGNUM);
}

int
alpha_register_convertible (int regno)
{
  return (regno >= FP0_REGNUM && regno <= FP0_REGNUM + 31);
}


/* Guaranteed to set frame->saved_regs to some values (it never leaves it
   NULL).  */

void
alpha_find_saved_regs (struct frame_info *frame)
{
  int ireg;
  CORE_ADDR reg_position;
  unsigned long mask;
  alpha_extra_func_info_t proc_desc;
  int returnreg;

  frame_saved_regs_zalloc (frame);

  /* If it is the frame for __sigtramp, the saved registers are located
     in a sigcontext structure somewhere on the stack. __sigtramp
     passes a pointer to the sigcontext structure on the stack.
     If the stack layout for __sigtramp changes, or if sigcontext offsets
     change, we might have to update this code.  */
#ifndef SIGFRAME_PC_OFF
#define SIGFRAME_PC_OFF		(2 * 8)
#define SIGFRAME_REGSAVE_OFF	(4 * 8)
#define SIGFRAME_FPREGSAVE_OFF	(SIGFRAME_REGSAVE_OFF + 32 * 8 + 8)
#endif
  if (frame->signal_handler_caller)
    {
      CORE_ADDR sigcontext_addr;

      sigcontext_addr = SIGCONTEXT_ADDR (frame);
      for (ireg = 0; ireg < 32; ireg++)
	{
	  reg_position = sigcontext_addr + SIGFRAME_REGSAVE_OFF + ireg * 8;
	  frame->saved_regs[ireg] = reg_position;
	}
      for (ireg = 0; ireg < 32; ireg++)
	{
	  reg_position = sigcontext_addr + SIGFRAME_FPREGSAVE_OFF + ireg * 8;
	  frame->saved_regs[FP0_REGNUM + ireg] = reg_position;
	}
      frame->saved_regs[PC_REGNUM] = sigcontext_addr + SIGFRAME_PC_OFF;
      return;
    }

  proc_desc = frame->proc_desc;
  if (proc_desc == NULL)
    /* I'm not sure how/whether this can happen.  Normally when we can't
       find a proc_desc, we "synthesize" one using heuristic_proc_desc
       and set the saved_regs right away.  */
    return;

  /* Fill in the offsets for the registers which gen_mask says
     were saved.  */

  reg_position = frame->frame + PROC_REG_OFFSET (proc_desc);
  mask = PROC_REG_MASK (proc_desc);

  returnreg = PROC_PC_REG (proc_desc);

  /* Note that RA is always saved first, regardless of its actual
     register number.  */
  if (mask & (1 << returnreg))
    {
      frame->saved_regs[returnreg] = reg_position;
      reg_position += 8;
      mask &= ~(1 << returnreg);	/* Clear bit for RA so we
					   don't save again later. */
    }

  for (ireg = 0; ireg <= 31; ++ireg)
    if (mask & (1 << ireg))
      {
	frame->saved_regs[ireg] = reg_position;
	reg_position += 8;
      }

  /* Fill in the offsets for the registers which float_mask says
     were saved.  */

  reg_position = frame->frame + PROC_FREG_OFFSET (proc_desc);
  mask = PROC_FREG_MASK (proc_desc);

  for (ireg = 0; ireg <= 31; ++ireg)
    if (mask & (1 << ireg))
      {
	frame->saved_regs[FP0_REGNUM + ireg] = reg_position;
	reg_position += 8;
      }

  frame->saved_regs[PC_REGNUM] = frame->saved_regs[returnreg];
}

static CORE_ADDR
read_next_frame_reg (struct frame_info *fi, int regno)
{
  for (; fi; fi = fi->next)
    {
      /* We have to get the saved sp from the sigcontext
         if it is a signal handler frame.  */
      if (regno == SP_REGNUM && !fi->signal_handler_caller)
	return fi->frame;
      else
	{
	  if (fi->saved_regs == NULL)
	    alpha_find_saved_regs (fi);
	  if (fi->saved_regs[regno])
	    return read_memory_integer (fi->saved_regs[regno], 8);
	}
    }
  return read_register (regno);
}

CORE_ADDR
alpha_frame_saved_pc (struct frame_info *frame)
{
  alpha_extra_func_info_t proc_desc = frame->proc_desc;
  /* We have to get the saved pc from the sigcontext
     if it is a signal handler frame.  */
  int pcreg = frame->signal_handler_caller ? PC_REGNUM : frame->pc_reg;

  if (proc_desc && PROC_DESC_IS_DUMMY (proc_desc))
    return read_memory_integer (frame->frame - 8, 8);

  return read_next_frame_reg (frame, pcreg);
}

CORE_ADDR
alpha_saved_pc_after_call (struct frame_info *frame)
{
  CORE_ADDR pc = frame->pc;
  CORE_ADDR tmp;
  alpha_extra_func_info_t proc_desc;
  int pcreg;

  /* Skip over shared library trampoline if necessary.  */
  tmp = SKIP_TRAMPOLINE_CODE (pc);
  if (tmp != 0)
    pc = tmp;

  proc_desc = find_proc_desc (pc, frame->next);
  pcreg = proc_desc ? PROC_PC_REG (proc_desc) : RA_REGNUM;

  if (frame->signal_handler_caller)
    return alpha_frame_saved_pc (frame);
  else
    return read_register (pcreg);
}


static struct alpha_extra_func_info temp_proc_desc;
static struct frame_saved_regs temp_saved_regs;

/* Nonzero if instruction at PC is a return instruction.  "ret
   $zero,($ra),1" on alpha. */

static int
alpha_about_to_return (CORE_ADDR pc)
{
  return read_memory_integer (pc, 4) == 0x6bfa8001;
}



/* This fencepost looks highly suspicious to me.  Removing it also
   seems suspicious as it could affect remote debugging across serial
   lines.  */

static CORE_ADDR
heuristic_proc_start (CORE_ADDR pc)
{
  CORE_ADDR start_pc = pc;
  CORE_ADDR fence = start_pc - heuristic_fence_post;

  if (start_pc == 0)
    return 0;

  if (heuristic_fence_post == UINT_MAX
      || fence < VM_MIN_ADDRESS)
    fence = VM_MIN_ADDRESS;

  /* search back for previous return */
  for (start_pc -= 4;; start_pc -= 4)
    if (start_pc < fence)
      {
	/* It's not clear to me why we reach this point when
	   stop_soon_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_quietly)
	  {
	    static int blurb_printed = 0;

	    if (fence == VM_MIN_ADDRESS)
	      warning ("Hit beginning of text section without finding");
	    else
	      warning ("Hit heuristic-fence-post without finding");

	    warning ("enclosing function for address 0x%s", paddr_nz (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;
      }
    else if (alpha_about_to_return (start_pc))
      break;

  start_pc += 4;		/* skip return */
  return start_pc;
}

static alpha_extra_func_info_t
heuristic_proc_desc (CORE_ADDR start_pc, CORE_ADDR limit_pc,
		     struct frame_info *next_frame)
{
  CORE_ADDR sp = read_next_frame_reg (next_frame, SP_REGNUM);
  CORE_ADDR cur_pc;
  int frame_size;
  int has_frame_reg = 0;
  unsigned long reg_mask = 0;
  int pcreg = -1;

  if (start_pc == 0)
    return NULL;
  memset (&temp_proc_desc, '\0', sizeof (temp_proc_desc));
  memset (&temp_saved_regs, '\0', sizeof (struct frame_saved_regs));
  PROC_LOW_ADDR (&temp_proc_desc) = start_pc;

  if (start_pc + 200 < limit_pc)
    limit_pc = start_pc + 200;
  frame_size = 0;
  for (cur_pc = start_pc; cur_pc < limit_pc; cur_pc += 4)
    {
      char buf[4];
      unsigned long word;
      int status;

      status = read_memory_nobpt (cur_pc, buf, 4);
      if (status)
	memory_error (status, cur_pc);
      word = extract_unsigned_integer (buf, 4);

      if ((word & 0xffff0000) == 0x23de0000)	/* lda $sp,n($sp) */
	{
	  if (word & 0x8000)
	    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) */
	       && (word & 0xffff0000) != 0xb7fe0000)	/* reg != $zero */
	{
	  int reg = (word & 0x03e00000) >> 21;
	  reg_mask |= 1 << reg;
	  temp_saved_regs.regs[reg] = sp + (short) word;

	  /* 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 (pcreg == -1
	      && cur_pc < (start_pc + 80)
	      && (reg == T7_REGNUM || reg == T9_REGNUM || reg == RA_REGNUM))
	    pcreg = reg;
	}
      else if ((word & 0xffe0ffff) == 0x6be08001)	/* ret zero,reg,1 */
	pcreg = (word >> 16) & 0x1f;
      else if (word == 0x47de040f)	/* bis sp,sp fp */
	has_frame_reg = 1;
    }
  if (pcreg == -1)
    {
      /* If we haven't found a valid return address register yet,
         keep searching in the procedure prologue.  */
      while (cur_pc < (limit_pc + 80) && cur_pc < (start_pc + 80))
	{
	  char buf[4];
	  unsigned long word;

	  if (read_memory_nobpt (cur_pc, buf, 4))
	    break;
	  cur_pc += 4;
	  word = extract_unsigned_integer (buf, 4);

	  if ((word & 0xfc1f0000) == 0xb41e0000		/* stq reg,n($sp) */
	      && (word & 0xffff0000) != 0xb7fe0000)	/* reg != $zero */
	    {
	      int reg = (word & 0x03e00000) >> 21;
	      if (reg == T7_REGNUM || reg == T9_REGNUM || reg == RA_REGNUM)
		{
		  pcreg = reg;
		  break;
		}
	    }
	  else if ((word & 0xffe0ffff) == 0x6be08001)	/* ret zero,reg,1 */
	    {
	      pcreg = (word >> 16) & 0x1f;
	      break;
	    }
	}
    }

  if (has_frame_reg)
    PROC_FRAME_REG (&temp_proc_desc) = GCC_FP_REGNUM;
  else
    PROC_FRAME_REG (&temp_proc_desc) = SP_REGNUM;
  PROC_FRAME_OFFSET (&temp_proc_desc) = frame_size;
  PROC_REG_MASK (&temp_proc_desc) = reg_mask;
  PROC_PC_REG (&temp_proc_desc) = (pcreg == -1) ? RA_REGNUM : pcreg;
  PROC_LOCALOFF (&temp_proc_desc) = 0;	/* XXX - bogus */
  return &temp_proc_desc;
}

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

static CORE_ADDR
after_prologue (CORE_ADDR pc, alpha_extra_func_info_t proc_desc)
{
  struct symtab_and_line sal;
  CORE_ADDR func_addr, func_end;

  if (!proc_desc)
    proc_desc = find_proc_desc (pc, NULL);

  if (proc_desc)
    {
      if (PROC_DESC_IS_DYN_SIGTRAMP (proc_desc))
	return PROC_LOW_ADDR (proc_desc);	/* "prologue" is in kernel */

      /* If function is frameless, then we need to do it the hard way.  I
         strongly suspect that frameless always means prologueless... */
      if (PROC_FRAME_REG (proc_desc) == SP_REGNUM
	  && PROC_FRAME_OFFSET (proc_desc) == 0)
	return 0;
    }

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

  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;
}

/* Return non-zero if we *might* be in a function prologue.  Return zero if we
   are definitively *not* in a function prologue.  */

static int
alpha_in_prologue (CORE_ADDR pc, alpha_extra_func_info_t proc_desc)
{
  CORE_ADDR after_prologue_pc;

  after_prologue_pc = after_prologue (pc, proc_desc);

  if (after_prologue_pc == 0
      || pc < after_prologue_pc)
    return 1;
  else
    return 0;
}

static alpha_extra_func_info_t
find_proc_desc (CORE_ADDR pc, struct frame_info *next_frame)
{
  alpha_extra_func_info_t proc_desc;
  struct block *b;
  struct symbol *sym;
  CORE_ADDR startaddr;

  /* Try to get the proc_desc from the linked call dummy proc_descs
     if the pc is in the call dummy.
     This is hairy. In the case of nested dummy calls we have to find the
     right proc_desc, but we might not yet know the frame for the dummy
     as it will be contained in the proc_desc we are searching for.
     So we have to find the proc_desc whose frame is closest to the current
     stack pointer.  */

  if (PC_IN_CALL_DUMMY (pc, 0, 0))
    {
      struct linked_proc_info *link;
      CORE_ADDR sp = read_next_frame_reg (next_frame, SP_REGNUM);
      alpha_extra_func_info_t found_proc_desc = NULL;
      long min_distance = LONG_MAX;

      for (link = linked_proc_desc_table; link; link = link->next)
	{
	  long distance = (CORE_ADDR) PROC_DUMMY_FRAME (&link->info) - sp;
	  if (distance > 0 && distance < min_distance)
	    {
	      min_distance = distance;
	      found_proc_desc = &link->info;
	    }
	}
      if (found_proc_desc != NULL)
	return found_proc_desc;
    }

  b = block_for_pc (pc);

  find_pc_partial_function (pc, NULL, &startaddr, NULL);
  if (b == NULL)
    sym = NULL;
  else
    {
      if (startaddr > BLOCK_START (b))
	/* This is the "pathological" case referred to in a comment in
	   print_frame_info.  It might be better to move this check into
	   symbol reading.  */
	sym = NULL;
      else
	sym = lookup_symbol (MIPS_EFI_SYMBOL_NAME, b, LABEL_NAMESPACE,
			     0, NULL);
    }

  /* If we never found a PDR for this function in symbol reading, then
     examine prologues to find the information.  */
  if (sym && ((mips_extra_func_info_t) SYMBOL_VALUE (sym))->pdr.framereg == -1)
    sym = NULL;

  if (sym)
    {
      /* IF this is the topmost frame AND
       * (this proc does not have debugging information OR
       * the PC is in the procedure prologue)
       * THEN create a "heuristic" proc_desc (by analyzing
       * the actual code) to replace the "official" proc_desc.
       */
      proc_desc = (alpha_extra_func_info_t) SYMBOL_VALUE (sym);
      if (next_frame == NULL)
	{
	  if (PROC_DESC_IS_DUMMY (proc_desc) || alpha_in_prologue (pc, proc_desc))
	    {
	      alpha_extra_func_info_t found_heuristic =
	      heuristic_proc_desc (PROC_LOW_ADDR (proc_desc),
				   pc, next_frame);
	      if (found_heuristic)
		{
		  PROC_LOCALOFF (found_heuristic) =
		    PROC_LOCALOFF (proc_desc);
		  PROC_PC_REG (found_heuristic) = PROC_PC_REG (proc_desc);
		  proc_desc = found_heuristic;
		}
	    }
	}
    }
  else
    {
      long offset;

      /* Is linked_proc_desc_table really necessary?  It only seems to be used
         by procedure call dummys.  However, the procedures being called ought
         to have their own proc_descs, and even if they don't,
         heuristic_proc_desc knows how to create them! */

      register struct linked_proc_info *link;
      for (link = linked_proc_desc_table; link; link = link->next)
	if (PROC_LOW_ADDR (&link->info) <= pc
	    && PROC_HIGH_ADDR (&link->info) > pc)
	  return &link->info;

      /* If PC is inside a dynamically generated sigtramp handler,
         create and push a procedure descriptor for that code: */
      offset = DYNAMIC_SIGTRAMP_OFFSET (pc);
      if (offset >= 0)
	return push_sigtramp_desc (pc - offset);

      /* If heuristic_fence_post is non-zero, determine the procedure
         start address by examining the instructions.
         This allows us to find the start address of static functions which
         have no symbolic information, as startaddr would have been set to
         the preceding global function start address by the
         find_pc_partial_function call above.  */
      if (startaddr == 0 || heuristic_fence_post != 0)
	startaddr = heuristic_proc_start (pc);

      proc_desc =
	heuristic_proc_desc (startaddr, pc, next_frame);
    }
  return proc_desc;
}

alpha_extra_func_info_t cached_proc_desc;

CORE_ADDR
alpha_frame_chain (struct frame_info *frame)
{
  alpha_extra_func_info_t proc_desc;
  CORE_ADDR saved_pc = FRAME_SAVED_PC (frame);

  if (saved_pc == 0 || inside_entry_file (saved_pc))
    return 0;

  proc_desc = find_proc_desc (saved_pc, frame);
  if (!proc_desc)
    return 0;

  cached_proc_desc = proc_desc;

  /* Fetch the frame pointer for a dummy frame from the procedure
     descriptor.  */
  if (PROC_DESC_IS_DUMMY (proc_desc))
    return (CORE_ADDR) PROC_DUMMY_FRAME (proc_desc);

  /* If no frame pointer and frame size is zero, we must be at end
     of stack (or otherwise hosed).  If we don't check frame size,
     we loop forever if we see a zero size frame.  */
  if (PROC_FRAME_REG (proc_desc) == SP_REGNUM
      && PROC_FRAME_OFFSET (proc_desc) == 0
  /* The previous frame from a sigtramp frame might be frameless
     and have frame size zero.  */
      && !frame->signal_handler_caller)
    return FRAME_PAST_SIGTRAMP_FRAME (frame, saved_pc);
  else
    return read_next_frame_reg (frame, PROC_FRAME_REG (proc_desc))
      + PROC_FRAME_OFFSET (proc_desc);
}

void
init_extra_frame_info (struct frame_info *frame)
{
  /* Use proc_desc calculated in frame_chain */
  alpha_extra_func_info_t proc_desc =
  frame->next ? cached_proc_desc : find_proc_desc (frame->pc, frame->next);

  frame->saved_regs = NULL;
  frame->localoff = 0;
  frame->pc_reg = RA_REGNUM;
  frame->proc_desc = proc_desc == &temp_proc_desc ? 0 : proc_desc;
  if (proc_desc)
    {
      /* Get the locals offset and the saved pc register from the
         procedure descriptor, they are valid even if we are in the
         middle of the prologue.  */
      frame->localoff = PROC_LOCALOFF (proc_desc);
      frame->pc_reg = PROC_PC_REG (proc_desc);

      /* Fixup frame-pointer - only needed for top frame */

      /* Fetch the frame pointer for a dummy frame from the procedure
         descriptor.  */
      if (PROC_DESC_IS_DUMMY (proc_desc))
	frame->frame = (CORE_ADDR) PROC_DUMMY_FRAME (proc_desc);

      /* This may not be quite right, if proc has a real frame register.
         Get the value of the frame relative sp, procedure might have been
         interrupted by a signal at it's very start.  */
      else if (frame->pc == PROC_LOW_ADDR (proc_desc)
	       && !PROC_DESC_IS_DYN_SIGTRAMP (proc_desc))
	frame->frame = read_next_frame_reg (frame->next, SP_REGNUM);
      else
	frame->frame = read_next_frame_reg (frame->next, PROC_FRAME_REG (proc_desc))
	  + PROC_FRAME_OFFSET (proc_desc);

      if (proc_desc == &temp_proc_desc)
	{
	  char *name;

	  /* Do not set the saved registers for a sigtramp frame,
	     alpha_find_saved_registers will do that for us.
	     We can't use frame->signal_handler_caller, it is not yet set.  */
	  find_pc_partial_function (frame->pc, &name,
				    (CORE_ADDR *) NULL, (CORE_ADDR *) NULL);
	  if (!IN_SIGTRAMP (frame->pc, name))
	    {
	      frame->saved_regs = (CORE_ADDR *)
		frame_obstack_alloc (SIZEOF_FRAME_SAVED_REGS);
	      memcpy (frame->saved_regs, temp_saved_regs.regs, SIZEOF_FRAME_SAVED_REGS);
	      frame->saved_regs[PC_REGNUM]
		= frame->saved_regs[RA_REGNUM];
	    }
	}
    }
}

/* ALPHA stack frames are almost impenetrable.  When execution stops,
   we basically have to look at symbol information for the function
   that we stopped in, which tells us *which* register (if any) is
   the base of the frame pointer, and what offset from that register
   the frame itself is at.  

   This presents a problem when trying to examine a stack in memory
   (that isn't executing at the moment), using the "frame" command.  We
   don't have a PC, nor do we have any registers except SP.

   This routine takes two arguments, SP and PC, and tries to make the
   cached frames look as if these two arguments defined a frame on the
   cache.  This allows the rest of info frame to extract the important
   arguments without difficulty.  */

struct frame_info *
setup_arbitrary_frame (int argc, CORE_ADDR *argv)
{
  if (argc != 2)
    error ("ALPHA frame specifications require two arguments: sp and pc");

  return create_new_frame (argv[0], argv[1]);
}

/* The alpha passes the first six arguments in the registers, the rest on
   the stack. The register arguments are eventually transferred to the
   argument transfer area immediately below the stack by the called function
   anyway. So we `push' at least six arguments on the stack, `reload' the
   argument registers and then adjust the stack pointer to point past the
   sixth argument. This algorithm simplifies the passing of a large struct
   which extends from the registers to the stack.
   If the called function is returning a structure, the address of the
   structure to be returned is passed as a hidden first argument.  */

CORE_ADDR
alpha_push_arguments (int nargs, struct value **args, CORE_ADDR sp,
		      int struct_return, CORE_ADDR struct_addr)
{
  int i;
  int accumulate_size = struct_return ? 8 : 0;
  int arg_regs_size = ALPHA_NUM_ARG_REGS * 8;
  struct alpha_arg
    {
      char *contents;
      int len;
      int offset;
    };
  struct alpha_arg *alpha_args =
  (struct alpha_arg *) alloca (nargs * sizeof (struct alpha_arg));
  register struct alpha_arg *m_arg;
  char raw_buffer[sizeof (CORE_ADDR)];
  int required_arg_regs;

  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) < TYPE_LENGTH (builtin_type_long))
	    {
	      arg_type = builtin_type_long;
	      arg = value_cast (arg_type, arg);
	    }
	  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 (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 < arg_regs_size)
    accumulate_size = arg_regs_size;
  sp -= accumulate_size;

  /* Keep sp aligned to a multiple of 16 as the compiler does it too.  */
  sp &= ~15;

  /* `Push' arguments on the stack.  */
  for (i = nargs; m_arg--, --i >= 0;)
    write_memory (sp + m_arg->offset, m_arg->contents, m_arg->len);
  if (struct_return)
    {
      store_address (raw_buffer, sizeof (CORE_ADDR), struct_addr);
      write_memory (sp, raw_buffer, sizeof (CORE_ADDR));
    }

  /* Load the argument registers.  */
  for (i = 0; i < required_arg_regs; i++)
    {
      LONGEST val;

      val = read_memory_integer (sp + i * 8, 8);
      write_register (A0_REGNUM + i, val);
      write_register (FPA0_REGNUM + i, val);
    }

  return sp + arg_regs_size;
}

void
alpha_push_dummy_frame (void)
{
  int ireg;
  struct linked_proc_info *link;
  alpha_extra_func_info_t proc_desc;
  CORE_ADDR sp = read_register (SP_REGNUM);
  CORE_ADDR save_address;
  char raw_buffer[MAX_REGISTER_RAW_SIZE];
  unsigned long mask;

  link = (struct linked_proc_info *) xmalloc (sizeof (struct linked_proc_info));
  link->next = linked_proc_desc_table;
  linked_proc_desc_table = link;

  proc_desc = &link->info;

  /*
   * The registers we must save are all those not preserved across
   * procedure calls.
   * In addition, we must save the PC and RA.
   *
   * Dummy frame layout:
   *  (high memory)
   *    Saved PC
   *    Saved F30
   *    ...
   *    Saved F0
   *    Saved R29
   *    ...
   *    Saved R0
   *    Saved R26 (RA)
   *    Parameter build area
   *  (low memory)
   */

/* MASK(i,j) == (1<<i) + (1<<(i+1)) + ... + (1<<j)). Assume i<=j<31. */
#define MASK(i,j) ((((LONGEST)1 << ((j)+1)) - 1) ^ (((LONGEST)1 << (i)) - 1))
#define GEN_REG_SAVE_MASK (MASK(0,8) | MASK(16,29))
#define GEN_REG_SAVE_COUNT 24
#define FLOAT_REG_SAVE_MASK (MASK(0,1) | MASK(10,30))
#define FLOAT_REG_SAVE_COUNT 23
  /* The special register is the PC as we have no bit for it in the save masks.
     alpha_frame_saved_pc knows where the pc is saved in a dummy frame.  */
#define SPECIAL_REG_SAVE_COUNT 1

  PROC_REG_MASK (proc_desc) = GEN_REG_SAVE_MASK;
  PROC_FREG_MASK (proc_desc) = FLOAT_REG_SAVE_MASK;
  /* PROC_REG_OFFSET is the offset from the dummy frame to the saved RA,
     but keep SP aligned to a multiple of 16.  */
  PROC_REG_OFFSET (proc_desc) =
    -((8 * (SPECIAL_REG_SAVE_COUNT
	    + GEN_REG_SAVE_COUNT
	    + FLOAT_REG_SAVE_COUNT)
       + 15) & ~15);
  PROC_FREG_OFFSET (proc_desc) =
    PROC_REG_OFFSET (proc_desc) + 8 * GEN_REG_SAVE_COUNT;

  /* Save general registers.
     The return address register is the first saved register, all other
     registers follow in ascending order.
     The PC is saved immediately below the SP.  */
  save_address = sp + PROC_REG_OFFSET (proc_desc);
  store_address (raw_buffer, 8, read_register (RA_REGNUM));
  write_memory (save_address, raw_buffer, 8);
  save_address += 8;
  mask = PROC_REG_MASK (proc_desc) & 0xffffffffL;
  for (ireg = 0; mask; ireg++, mask >>= 1)
    if (mask & 1)
      {
	if (ireg == RA_REGNUM)
	  continue;
	store_address (raw_buffer, 8, read_register (ireg));
	write_memory (save_address, raw_buffer, 8);
	save_address += 8;
      }

  store_address (raw_buffer, 8, read_register (PC_REGNUM));
  write_memory (sp - 8, raw_buffer, 8);

  /* Save floating point registers.  */
  save_address = sp + PROC_FREG_OFFSET (proc_desc);
  mask = PROC_FREG_MASK (proc_desc) & 0xffffffffL;
  for (ireg = 0; mask; ireg++, mask >>= 1)
    if (mask & 1)
      {
	store_address (raw_buffer, 8, read_register (ireg + FP0_REGNUM));
	write_memory (save_address, raw_buffer, 8);
	save_address += 8;
      }

  /* Set and save the frame address for the dummy.  
     This is tricky. The only registers that are suitable for a frame save
     are those that are preserved across procedure calls (s0-s6). But if
     a read system call is interrupted and then a dummy call is made
     (see testsuite/gdb.t17/interrupt.exp) the dummy call hangs till the read
     is satisfied. Then it returns with the s0-s6 registers set to the values
     on entry to the read system call and our dummy frame pointer would be
     destroyed. So we save the dummy frame in the proc_desc and handle the
     retrieval of the frame pointer of a dummy specifically. The frame register
     is set to the virtual frame (pseudo) register, it's value will always
     be read as zero and will help us to catch any errors in the dummy frame
     retrieval code.  */
  PROC_DUMMY_FRAME (proc_desc) = sp;
  PROC_FRAME_REG (proc_desc) = FP_REGNUM;
  PROC_FRAME_OFFSET (proc_desc) = 0;
  sp += PROC_REG_OFFSET (proc_desc);
  write_register (SP_REGNUM, sp);

  PROC_LOW_ADDR (proc_desc) = CALL_DUMMY_ADDRESS ();
  PROC_HIGH_ADDR (proc_desc) = PROC_LOW_ADDR (proc_desc) + 4;

  SET_PROC_DESC_IS_DUMMY (proc_desc);
  PROC_PC_REG (proc_desc) = RA_REGNUM;
}

void
alpha_pop_frame (void)
{
  register int regnum;
  struct frame_info *frame = get_current_frame ();
  CORE_ADDR new_sp = frame->frame;

  alpha_extra_func_info_t proc_desc = frame->proc_desc;

  /* we need proc_desc to know how to restore the registers;
     if it is NULL, construct (a temporary) one */
  if (proc_desc == NULL)
    proc_desc = find_proc_desc (frame->pc, frame->next);

  /* Question: should we copy this proc_desc and save it in
     frame->proc_desc?  If we do, who will free it?
     For now, we don't save a copy... */

  write_register (PC_REGNUM, FRAME_SAVED_PC (frame));
  if (frame->saved_regs == NULL)
    alpha_find_saved_regs (frame);
  if (proc_desc)
    {
      for (regnum = 32; --regnum >= 0;)
	if (PROC_REG_MASK (proc_desc) & (1 << regnum))
	  write_register (regnum,
			  read_memory_integer (frame->saved_regs[regnum],
					       8));
      for (regnum = 32; --regnum >= 0;)
	if (PROC_FREG_MASK (proc_desc) & (1 << regnum))
	  write_register (regnum + FP0_REGNUM,
	   read_memory_integer (frame->saved_regs[regnum + FP0_REGNUM], 8));
    }
  write_register (SP_REGNUM, new_sp);
  flush_cached_frames ();

  if (proc_desc && (PROC_DESC_IS_DUMMY (proc_desc)
		    || PROC_DESC_IS_DYN_SIGTRAMP (proc_desc)))
    {
      struct linked_proc_info *pi_ptr, *prev_ptr;

      for (pi_ptr = linked_proc_desc_table, prev_ptr = NULL;
	   pi_ptr != NULL;
	   prev_ptr = pi_ptr, pi_ptr = pi_ptr->next)
	{
	  if (&pi_ptr->info == proc_desc)
	    break;
	}

      if (pi_ptr == NULL)
	error ("Can't locate dummy extra frame info\n");

      if (prev_ptr != NULL)
	prev_ptr->next = pi_ptr->next;
      else
	linked_proc_desc_table = pi_ptr->next;

      xfree (pi_ptr);
    }
}

/* 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.
   Currently we must not skip more on the alpha, but we might need the
   lenient stuff some day.  */

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

#ifdef GDB_TARGET_HAS_SHARED_LIBS
  /* 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.  */
  if (target_read_memory (pc, buf, 4))
    return pc;
#endif

  /* 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 = after_prologue (pc, NULL);

  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)
    {
      int status;

      status = read_memory_nobpt (pc + offset, buf, 4);
      if (status)
	memory_error (status, pc + offset);
      inst = extract_unsigned_integer (buf, 4);

      /* The alpha has no delay slots. But let's keep the lenient stuff,
         we might need it for something else in the future.  */
      if (lenient && 0)
	continue;

      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
	  && (inst & 0xffff0000) != 0xb7fe0000)
	continue;		/* stq reg,n($sp) */
      /* reg != $zero */
      if ((inst & 0xfc1f0000) == 0x9c1e0000
	  && (inst & 0xffff0000) != 0x9ffe0000)
	continue;		/* stt reg,n($sp) */
      /* reg != $zero */
      if (inst == 0x47de040f)	/* bis sp,sp,fp */
	continue;

      break;
    }
  return pc + offset;
}

#if 0
/* Is address PC in the prologue (loosely defined) for function at
   STARTADDR?  */

static int
alpha_in_lenient_prologue (CORE_ADDR startaddr, CORE_ADDR pc)
{
  CORE_ADDR end_prologue = alpha_skip_prologue (startaddr, 1);
  return pc >= startaddr && pc < end_prologue;
}
#endif

/* 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. */
void
alpha_register_convert_to_virtual (int regnum, struct type *valtype,
				   char *raw_buffer, char *virtual_buffer)
{
  if (TYPE_LENGTH (valtype) >= REGISTER_RAW_SIZE (regnum))
    {
      memcpy (virtual_buffer, raw_buffer, REGISTER_VIRTUAL_SIZE (regnum));
      return;
    }

  if (TYPE_CODE (valtype) == TYPE_CODE_FLT)
    {
      double d = extract_floating (raw_buffer, REGISTER_RAW_SIZE (regnum));
      store_floating (virtual_buffer, TYPE_LENGTH (valtype), d);
    }
  else if (TYPE_CODE (valtype) == TYPE_CODE_INT && TYPE_LENGTH (valtype) <= 4)
    {
      ULONGEST l;
      l = extract_unsigned_integer (raw_buffer, REGISTER_RAW_SIZE (regnum));
      l = ((l >> 32) & 0xc0000000) | ((l >> 29) & 0x3fffffff);
      store_unsigned_integer (virtual_buffer, TYPE_LENGTH (valtype), l);
    }
  else
    error ("Cannot retrieve value from floating point register");
}

void
alpha_register_convert_to_raw (struct type *valtype, int regnum,
			       char *virtual_buffer, char *raw_buffer)
{
  if (TYPE_LENGTH (valtype) >= REGISTER_RAW_SIZE (regnum))
    {
      memcpy (raw_buffer, virtual_buffer, REGISTER_RAW_SIZE (regnum));
      return;
    }

  if (TYPE_CODE (valtype) == TYPE_CODE_FLT)
    {
      double d = extract_floating (virtual_buffer, TYPE_LENGTH (valtype));
      store_floating (raw_buffer, REGISTER_RAW_SIZE (regnum), d);
    }
  else if (TYPE_CODE (valtype) == TYPE_CODE_INT && TYPE_LENGTH (valtype) <= 4)
    {
      ULONGEST l;
      if (TYPE_UNSIGNED (valtype))
	l = extract_unsigned_integer (virtual_buffer, TYPE_LENGTH (valtype));
      else
	l = extract_signed_integer (virtual_buffer, TYPE_LENGTH (valtype));
      l = ((l & 0xc0000000) << 32) | ((l & 0x3fffffff) << 29);
      store_unsigned_integer (raw_buffer, REGISTER_RAW_SIZE (regnum), l);
    }
  else
    error ("Cannot store value in floating point register");
}

/* Given a return value in `regbuf' with a type `valtype', 
   extract and copy its value into `valbuf'.  */

void
alpha_extract_return_value (struct type *valtype,
			    char regbuf[REGISTER_BYTES], char *valbuf)
{
  if (TYPE_CODE (valtype) == TYPE_CODE_FLT)
    alpha_register_convert_to_virtual (FP0_REGNUM, valtype,
				       regbuf + REGISTER_BYTE (FP0_REGNUM),
				       valbuf);
  else
    memcpy (valbuf, regbuf + REGISTER_BYTE (V0_REGNUM), TYPE_LENGTH (valtype));
}

/* Given a return value in `regbuf' with a type `valtype', 
   write its value into the appropriate register.  */

void
alpha_store_return_value (struct type *valtype, char *valbuf)
{
  char raw_buffer[MAX_REGISTER_RAW_SIZE];
  int regnum = V0_REGNUM;
  int length = TYPE_LENGTH (valtype);

  if (TYPE_CODE (valtype) == TYPE_CODE_FLT)
    {
      regnum = FP0_REGNUM;
      length = REGISTER_RAW_SIZE (regnum);
      alpha_register_convert_to_raw (valtype, regnum, valbuf, raw_buffer);
    }
  else
    memcpy (raw_buffer, valbuf, length);

  write_register_bytes (REGISTER_BYTE (regnum), raw_buffer, length);
}

/* Just like reinit_frame_cache, but with the right arguments to be
   callable as an sfunc.  */

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

/* This is the definition of CALL_DUMMY_ADDRESS.  It's a heuristic that is used
   to find a convenient place in the text segment to stick a breakpoint to
   detect the completion of a target function call (ala call_function_by_hand).
 */

CORE_ADDR
alpha_call_dummy_address (void)
{
  CORE_ADDR entry;
  struct minimal_symbol *sym;

  entry = entry_point_address ();

  if (entry != 0)
    return entry;

  sym = lookup_minimal_symbol ("_Prelude", NULL, symfile_objfile);

  if (!sym || MSYMBOL_TYPE (sym) != mst_text)
    return 0;
  else
    return SYMBOL_VALUE_ADDRESS (sym) + 4;
}

int
alpha_use_struct_convention (int gcc_p, struct type *type)
{
  /* Structures are returned by ref in extra arg0.  */
  return 1;
}

/* 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 offset;
  LONGEST rav;

  insn = read_memory_unsigned_integer (pc, sizeof (insn));

  /* 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.  */
      rav = (LONGEST) read_register ((insn >> 21) & 0x1f);
      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;
	}
    }

  /* 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);
    }
}

void
_initialize_alpha_tdep (void)
{
  struct cmd_list_element *c;

  tm_print_insn = print_insn_alpha;

  /* 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.  */
  c = add_set_cmd ("heuristic-fence-post", class_support, var_zinteger,
		   (char *) &heuristic_fence_post,
		   "\
Set the distance searched for the start of a function.\n\
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.",
		   &setlist);
  /* We need to throw away the frame cache when we set this, since it
     might change our ability to get backtraces.  */
  c->function.sfunc = reinit_frame_cache_sfunc;
  add_show_from_set (c, &showlist);
}