aboutsummaryrefslogtreecommitdiff
path: root/gdb/i387-tdep.c
blob: 04b43df0b26f190e3dbf50eaf32330a545776121 (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
/* Intel 387 floating point stuff.

   Copyright 1988, 1989, 1991, 1992, 1993, 1994, 1998, 1999, 2000,
   2001, 2002, 2003, 2004 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 "floatformat.h"
#include "frame.h"
#include "gdbcore.h"
#include "inferior.h"
#include "language.h"
#include "regcache.h"
#include "value.h"

#include "gdb_assert.h"
#include "gdb_string.h"

#include "i386-tdep.h"
#include "i387-tdep.h"

/* Implement the `info float' layout based on the register definitions
   in `tm-i386.h'.  */

/* Print the floating point number specified by RAW.  */

static void
print_i387_value (char *raw, struct ui_file *file)
{
  DOUBLEST value;

  /* Using extract_typed_floating here might affect the representation
     of certain numbers such as NaNs, even if GDB is running natively.
     This is fine since our caller already detects such special
     numbers and we print the hexadecimal representation anyway.  */
  value = extract_typed_floating (raw, builtin_type_i387_ext);

  /* We try to print 19 digits.  The last digit may or may not contain
     garbage, but we'd better print one too many.  We need enough room
     to print the value, 1 position for the sign, 1 for the decimal
     point, 19 for the digits and 6 for the exponent adds up to 27.  */
#ifdef PRINTF_HAS_LONG_DOUBLE
  fprintf_filtered (file, " %-+27.19Lg", (long double) value);
#else
  fprintf_filtered (file, " %-+27.19g", (double) value);
#endif
}

/* Print the classification for the register contents RAW.  */

static void
print_i387_ext (unsigned char *raw, struct ui_file *file)
{
  int sign;
  int integer;
  unsigned int exponent;
  unsigned long fraction[2];

  sign = raw[9] & 0x80;
  integer = raw[7] & 0x80;
  exponent = (((raw[9] & 0x7f) << 8) | raw[8]);
  fraction[0] = ((raw[3] << 24) | (raw[2] << 16) | (raw[1] << 8) | raw[0]);
  fraction[1] = (((raw[7] & 0x7f) << 24) | (raw[6] << 16)
		 | (raw[5] << 8) | raw[4]);

  if (exponent == 0x7fff && integer)
    {
      if (fraction[0] == 0x00000000 && fraction[1] == 0x00000000)
	/* Infinity.  */
	fprintf_filtered (file, " %cInf", (sign ? '-' : '+'));
      else if (sign && fraction[0] == 0x00000000 && fraction[1] == 0x40000000)
	/* Real Indefinite (QNaN).  */
	fputs_unfiltered (" Real Indefinite (QNaN)", file);
      else if (fraction[1] & 0x40000000)
	/* QNaN.  */
	fputs_filtered (" QNaN", file);
      else
	/* SNaN.  */
	fputs_filtered (" SNaN", file);
    }
  else if (exponent < 0x7fff && exponent > 0x0000 && integer)
    /* Normal.  */
    print_i387_value (raw, file);
  else if (exponent == 0x0000)
    {
      /* Denormal or zero.  */
      print_i387_value (raw, file);
      
      if (integer)
	/* Pseudo-denormal.  */
	fputs_filtered (" Pseudo-denormal", file);
      else if (fraction[0] || fraction[1])
	/* Denormal.  */
	fputs_filtered (" Denormal", file);
    }
  else
    /* Unsupported.  */
    fputs_filtered (" Unsupported", file);
}

/* Print the status word STATUS.  */

static void
print_i387_status_word (unsigned int status, struct ui_file *file)
{
  fprintf_filtered (file, "Status Word:         %s",
		    hex_string_custom (status, 4));
  fputs_filtered ("  ", file);
  fprintf_filtered (file, " %s", (status & 0x0001) ? "IE" : "  ");
  fprintf_filtered (file, " %s", (status & 0x0002) ? "DE" : "  ");
  fprintf_filtered (file, " %s", (status & 0x0004) ? "ZE" : "  ");
  fprintf_filtered (file, " %s", (status & 0x0008) ? "OE" : "  ");
  fprintf_filtered (file, " %s", (status & 0x0010) ? "UE" : "  ");
  fprintf_filtered (file, " %s", (status & 0x0020) ? "PE" : "  ");
  fputs_filtered ("  ", file);
  fprintf_filtered (file, " %s", (status & 0x0080) ? "ES" : "  ");
  fputs_filtered ("  ", file);
  fprintf_filtered (file, " %s", (status & 0x0040) ? "SF" : "  ");
  fputs_filtered ("  ", file);
  fprintf_filtered (file, " %s", (status & 0x0100) ? "C0" : "  ");
  fprintf_filtered (file, " %s", (status & 0x0200) ? "C1" : "  ");
  fprintf_filtered (file, " %s", (status & 0x0400) ? "C2" : "  ");
  fprintf_filtered (file, " %s", (status & 0x4000) ? "C3" : "  ");

  fputs_filtered ("\n", file);

  fprintf_filtered (file,
		    "                       TOP: %d\n", ((status >> 11) & 7));
}

/* Print the control word CONTROL.  */

static void
print_i387_control_word (unsigned int control, struct ui_file *file)
{
  fprintf_filtered (file, "Control Word:        %s",
		    hex_string_custom (control, 4));
  fputs_filtered ("  ", file);
  fprintf_filtered (file, " %s", (control & 0x0001) ? "IM" : "  ");
  fprintf_filtered (file, " %s", (control & 0x0002) ? "DM" : "  ");
  fprintf_filtered (file, " %s", (control & 0x0004) ? "ZM" : "  ");
  fprintf_filtered (file, " %s", (control & 0x0008) ? "OM" : "  ");
  fprintf_filtered (file, " %s", (control & 0x0010) ? "UM" : "  ");
  fprintf_filtered (file, " %s", (control & 0x0020) ? "PM" : "  ");

  fputs_filtered ("\n", file);

  fputs_filtered ("                       PC: ", file);
  switch ((control >> 8) & 3)
    {
    case 0:
      fputs_filtered ("Single Precision (24-bits)\n", file);
      break;
    case 1:
      fputs_filtered ("Reserved\n", file);
      break;
    case 2:
      fputs_filtered ("Double Precision (53-bits)\n", file);
      break;
    case 3:
      fputs_filtered ("Extended Precision (64-bits)\n", file);
      break;
    }
      
  fputs_filtered ("                       RC: ", file);
  switch ((control >> 10) & 3)
    {
    case 0:
      fputs_filtered ("Round to nearest\n", file);
      break;
    case 1:
      fputs_filtered ("Round down\n", file);
      break;
    case 2:
      fputs_filtered ("Round up\n", file);
      break;
    case 3:
      fputs_filtered ("Round toward zero\n", file);
      break;
    }
}

/* Print out the i387 floating point state.  Note that we ignore FRAME
   in the code below.  That's OK since floating-point registers are
   never saved on the stack.  */

void
i387_print_float_info (struct gdbarch *gdbarch, struct ui_file *file,
		       struct frame_info *frame, const char *args)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (get_frame_arch (frame));
  char buf[4];
  ULONGEST fctrl;
  ULONGEST fstat;
  ULONGEST ftag;
  ULONGEST fiseg;
  ULONGEST fioff;
  ULONGEST foseg;
  ULONGEST fooff;
  ULONGEST fop;
  int fpreg;
  int top;

  gdb_assert (gdbarch == get_frame_arch (frame));

  /* Define I387_ST0_REGNUM such that we use the proper definitions
     for FRAME's architecture.  */
#define I387_ST0_REGNUM tdep->st0_regnum

  fctrl = get_frame_register_unsigned (frame, I387_FCTRL_REGNUM);
  fstat = get_frame_register_unsigned (frame, I387_FSTAT_REGNUM);
  ftag = get_frame_register_unsigned (frame, I387_FTAG_REGNUM);
  fiseg = get_frame_register_unsigned (frame, I387_FISEG_REGNUM);
  fioff = get_frame_register_unsigned (frame, I387_FIOFF_REGNUM);
  foseg = get_frame_register_unsigned (frame, I387_FOSEG_REGNUM);
  fooff = get_frame_register_unsigned (frame, I387_FOOFF_REGNUM);
  fop = get_frame_register_unsigned (frame, I387_FOP_REGNUM);

  top = ((fstat >> 11) & 7);

  for (fpreg = 7; fpreg >= 0; fpreg--)
    {
      unsigned char raw[I386_MAX_REGISTER_SIZE];
      int tag = (ftag >> (fpreg * 2)) & 3;
      int i;

      fprintf_filtered (file, "%sR%d: ", fpreg == top ? "=>" : "  ", fpreg);

      switch (tag)
	{
	case 0:
	  fputs_filtered ("Valid   ", file);
	  break;
	case 1:
	  fputs_filtered ("Zero    ", file);
	  break;
	case 2:
	  fputs_filtered ("Special ", file);
	  break;
	case 3:
	  fputs_filtered ("Empty   ", file);
	  break;
	}

      get_frame_register (frame, (fpreg + 8 - top) % 8 + I387_ST0_REGNUM, raw);

      fputs_filtered ("0x", file);
      for (i = 9; i >= 0; i--)
	fprintf_filtered (file, "%02x", raw[i]);

      if (tag != 3)
	print_i387_ext (raw, file);

      fputs_filtered ("\n", file);
    }

  fputs_filtered ("\n", file);

  print_i387_status_word (fstat, file);
  print_i387_control_word (fctrl, file);
  fprintf_filtered (file, "Tag Word:            %s\n",
		    hex_string_custom (ftag, 4));
  fprintf_filtered (file, "Instruction Pointer: %s:",
		    hex_string_custom (fiseg, 2));
  fprintf_filtered (file, "%s\n", hex_string_custom (fioff, 8));
  fprintf_filtered (file, "Operand Pointer:     %s:",
		    hex_string_custom (foseg, 2));
  fprintf_filtered (file, "%s\n", hex_string_custom (fooff, 8));
  fprintf_filtered (file, "Opcode:              %s\n",
		    hex_string_custom (fop ? (fop | 0xd800) : 0, 4));

#undef I387_ST0_REGNUM
}


/* Read a value of type TYPE from register REGNUM in frame FRAME, and
   return its contents in TO.  */

void
i387_register_to_value (struct frame_info *frame, int regnum,
			struct type *type, void *to)
{
  char from[I386_MAX_REGISTER_SIZE];

  gdb_assert (i386_fp_regnum_p (regnum));

  /* We only support floating-point values.  */
  if (TYPE_CODE (type) != TYPE_CODE_FLT)
    {
      warning ("Cannot convert floating-point register value "
	       "to non-floating-point type.");
      return;
    }

  /* Convert to TYPE.  This should be a no-op if TYPE is equivalent to
     the extended floating-point format used by the FPU.  */
  get_frame_register (frame, regnum, from);
  convert_typed_floating (from, builtin_type_i387_ext, to, type);
}

/* Write the contents FROM of a value of type TYPE into register
   REGNUM in frame FRAME.  */

void
i387_value_to_register (struct frame_info *frame, int regnum,
			struct type *type, const void *from)
{
  char to[I386_MAX_REGISTER_SIZE];

  gdb_assert (i386_fp_regnum_p (regnum));

  /* We only support floating-point values.  */
  if (TYPE_CODE (type) != TYPE_CODE_FLT)
    {
      warning ("Cannot convert non-floating-point type "
	       "to floating-point register value.");
      return;
    }

  /* Convert from TYPE.  This should be a no-op if TYPE is equivalent
     to the extended floating-point format used by the FPU.  */
  convert_typed_floating (from, type, to, builtin_type_i387_ext);
  put_frame_register (frame, regnum, to);
}


/* Handle FSAVE and FXSAVE formats.  */

/* FIXME: kettenis/20030927: The functions below should accept a
   `regcache' argument, but I don't want to change the function
   signature just yet.  There's some band-aid in the functions below
   in the form of the `regcache' local variables.  This will ease the
   transition later on.  */

/* At fsave_offset[REGNUM] you'll find the offset to the location in
   the data structure used by the "fsave" instruction where GDB
   register REGNUM is stored.  */

static int fsave_offset[] =
{
  28 + 0 * 10,			/* %st(0) ...  */
  28 + 1 * 10,
  28 + 2 * 10,
  28 + 3 * 10,
  28 + 4 * 10,
  28 + 5 * 10,
  28 + 6 * 10,
  28 + 7 * 10,			/* ... %st(7).  */
  0,				/* `fctrl' (16 bits).  */
  4,				/* `fstat' (16 bits).  */
  8,				/* `ftag' (16 bits).  */
  16,				/* `fiseg' (16 bits).  */
  12,				/* `fioff'.  */
  24,				/* `foseg' (16 bits).  */
  20,				/* `fooff'.  */
  18				/* `fop' (bottom 11 bits).  */
};

#define FSAVE_ADDR(fsave, regnum) \
  (fsave + fsave_offset[regnum - I387_ST0_REGNUM])


/* Fill register REGNUM in REGCACHE with the appropriate value from
   *FSAVE.  This function masks off any of the reserved bits in
   *FSAVE.  */

void
i387_supply_fsave (struct regcache *regcache, int regnum, const void *fsave)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (get_regcache_arch (regcache));
  const char *regs = fsave;
  int i;

  gdb_assert (tdep->st0_regnum >= I386_ST0_REGNUM);

  /* Define I387_ST0_REGNUM and I387_NUM_XMM_REGS such that we use the
     proper definitions for REGCACHE's architecture.  */

#define I387_ST0_REGNUM tdep->st0_regnum
#define I387_NUM_XMM_REGS tdep->num_xmm_regs

  for (i = I387_ST0_REGNUM; i < I387_XMM0_REGNUM; i++)
    if (regnum == -1 || regnum == i)
      {
	if (fsave == NULL)
	  {
	    regcache_raw_supply (regcache, i, NULL);
	    continue;
	  }

	/* Most of the FPU control registers occupy only 16 bits in the
	   fsave area.  Give those a special treatment.  */
	if (i >= I387_FCTRL_REGNUM
	    && i != I387_FIOFF_REGNUM && i != I387_FOOFF_REGNUM)
	  {
	    unsigned char val[4];

	    memcpy (val, FSAVE_ADDR (regs, i), 2);
	    val[2] = val[3] = 0;
	    if (i == I387_FOP_REGNUM)
	      val[1] &= ((1 << 3) - 1);
	    regcache_raw_supply (regcache, i, val);
	  }
	else
	  regcache_raw_supply (regcache, i, FSAVE_ADDR (regs, i));
      }

  /* Provide dummy values for the SSE registers.  */
  for (i = I387_XMM0_REGNUM; i < I387_MXCSR_REGNUM; i++)
    if (regnum == -1 || regnum == i)
      regcache_raw_supply (regcache, i, NULL);
  if (regnum == -1 || regnum == I387_MXCSR_REGNUM)
    {
      char buf[4];

      store_unsigned_integer (buf, 4, 0x1f80);
      regcache_raw_supply (regcache, I387_MXCSR_REGNUM, buf);
    }

#undef I387_ST0_REGNUM
#undef I387_NUM_XMM_REGS
}

/* Fill register REGNUM (if it is a floating-point register) in *FSAVE
   with the value from REGCACHE.  If REGNUM is -1, do this for all
   registers.  This function doesn't touch any of the reserved bits in
   *FSAVE.  */

void
i387_collect_fsave (const struct regcache *regcache, int regnum, void *fsave)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  char *regs = fsave;
  int i;

  gdb_assert (tdep->st0_regnum >= I386_ST0_REGNUM);

  /* Define I387_ST0_REGNUM such that we use the proper definitions
     for REGCACHE's architecture.  */
#define I387_ST0_REGNUM tdep->st0_regnum

  for (i = I387_ST0_REGNUM; i < I387_XMM0_REGNUM; i++)
    if (regnum == -1 || regnum == i)
      {
	/* Most of the FPU control registers occupy only 16 bits in
           the fsave area.  Give those a special treatment.  */
	if (i >= I387_FCTRL_REGNUM
	    && i != I387_FIOFF_REGNUM && i != I387_FOOFF_REGNUM)
	  {
	    unsigned char buf[4];

	    regcache_raw_collect (regcache, i, buf);

	    if (i == I387_FOP_REGNUM)
	      {
		/* The opcode occupies only 11 bits.  Make sure we
                   don't touch the other bits.  */
		buf[1] &= ((1 << 3) - 1);
		buf[1] |= ((FSAVE_ADDR (regs, i))[1] & ~((1 << 3) - 1));
	      }
	    memcpy (FSAVE_ADDR (regs, i), buf, 2);
	  }
	else
	  regcache_raw_collect (regcache, i, FSAVE_ADDR (regs, i));
      }
#undef I387_ST0_REGNUM
}

/* Fill register REGNUM (if it is a floating-point register) in *FSAVE
   with the value in GDB's register cache.  If REGNUM is -1, do this
   for all registers.  This function doesn't touch any of the reserved
   bits in *FSAVE.  */

void
i387_fill_fsave (void *fsave, int regnum)
{
  i387_collect_fsave (current_regcache, regnum, fsave);
}


/* At fxsave_offset[REGNUM] you'll find the offset to the location in
   the data structure used by the "fxsave" instruction where GDB
   register REGNUM is stored.  */

static int fxsave_offset[] =
{
  32,				/* %st(0) through ...  */
  48,
  64,
  80,
  96,
  112,
  128,
  144,				/* ... %st(7) (80 bits each).  */
  0,				/* `fctrl' (16 bits).  */
  2,				/* `fstat' (16 bits).  */
  4,				/* `ftag' (16 bits).  */
  12,				/* `fiseg' (16 bits).  */
  8,				/* `fioff'.  */
  20,				/* `foseg' (16 bits).  */
  16,				/* `fooff'.  */
  6,				/* `fop' (bottom 11 bits).  */
  160 + 0 * 16,			/* %xmm0 through ...  */
  160 + 1 * 16,
  160 + 2 * 16,
  160 + 3 * 16,
  160 + 4 * 16,
  160 + 5 * 16,
  160 + 6 * 16,
  160 + 7 * 16,
  160 + 8 * 16,
  160 + 9 * 16,
  160 + 10 * 16,
  160 + 11 * 16,
  160 + 12 * 16,
  160 + 13 * 16,
  160 + 14 * 16,
  160 + 15 * 16,		/* ... %xmm15 (128 bits each).  */
};

#define FXSAVE_ADDR(fxsave, regnum) \
  (fxsave + fxsave_offset[regnum - I387_ST0_REGNUM])

/* We made an unfortunate choice in putting %mxcsr after the SSE
   registers %xmm0-%xmm7 instead of before, since it makes supporting
   the registers %xmm8-%xmm15 on AMD64 a bit involved.  Therefore we
   don't include the offset for %mxcsr here above.  */

#define FXSAVE_MXCSR_ADDR(fxsave) (fxsave + 24)

static int i387_tag (const unsigned char *raw);


/* Fill register REGNUM in REGCACHE with the appropriate
   floating-point or SSE register value from *FXSAVE.  This function
   masks off any of the reserved bits in *FXSAVE.  */

void
i387_supply_fxsave (struct regcache *regcache, int regnum, const void *fxsave)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (get_regcache_arch (regcache));
  const char *regs = fxsave;
  int i;

  gdb_assert (tdep->st0_regnum >= I386_ST0_REGNUM);
  gdb_assert (tdep->num_xmm_regs > 0);

  /* Define I387_ST0_REGNUM and I387_NUM_XMM_REGS such that we use the
     proper definitions for REGCACHE's architecture.  */

#define I387_ST0_REGNUM	tdep->st0_regnum
#define I387_NUM_XMM_REGS tdep->num_xmm_regs

  for (i = I387_ST0_REGNUM; i < I387_MXCSR_REGNUM; i++)
    if (regnum == -1 || regnum == i)
      {
	if (regs == NULL)
	  {
	    regcache_raw_supply (regcache, i, NULL);
	    continue;
	  }

	/* Most of the FPU control registers occupy only 16 bits in
	   the fxsave area.  Give those a special treatment.  */
	if (i >= I387_FCTRL_REGNUM && i < I387_XMM0_REGNUM
	    && i != I387_FIOFF_REGNUM && i != I387_FOOFF_REGNUM)
	  {
	    unsigned char val[4];

	    memcpy (val, FXSAVE_ADDR (regs, i), 2);
	    val[2] = val[3] = 0;
	    if (i == I387_FOP_REGNUM)
	      val[1] &= ((1 << 3) - 1);
	    else if (i== I387_FTAG_REGNUM)
	      {
		/* The fxsave area contains a simplified version of
		   the tag word.  We have to look at the actual 80-bit
		   FP data to recreate the traditional i387 tag word.  */

		unsigned long ftag = 0;
		int fpreg;
		int top;

		top = ((FXSAVE_ADDR (regs, I387_FSTAT_REGNUM))[1] >> 3);
		top &= 0x7;

		for (fpreg = 7; fpreg >= 0; fpreg--)
		  {
		    int tag;

		    if (val[0] & (1 << fpreg))
		      {
			int regnum = (fpreg + 8 - top) % 8 + I387_ST0_REGNUM;
			tag = i387_tag (FXSAVE_ADDR (regs, regnum));
		      }
		    else
		      tag = 3;		/* Empty */

		    ftag |= tag << (2 * fpreg);
		  }
		val[0] = ftag & 0xff;
		val[1] = (ftag >> 8) & 0xff;
	      }
	    regcache_raw_supply (regcache, i, val);
	  }
	else
	  regcache_raw_supply (regcache, i, FXSAVE_ADDR (regs, i));
      }

  if (regnum == I387_MXCSR_REGNUM || regnum == -1)
    {
      if (regs == NULL)
	regcache_raw_supply (regcache, I387_MXCSR_REGNUM, NULL);
      else
	regcache_raw_supply (regcache, I387_MXCSR_REGNUM,
			     FXSAVE_MXCSR_ADDR (regs));
    }

#undef I387_ST0_REGNUM
#undef I387_NUM_XMM_REGS
}

/* Fill register REGNUM (if it is a floating-point or SSE register) in
   *FXSAVE with the value from REGCACHE.  If REGNUM is -1, do this for
   all registers.  This function doesn't touch any of the reserved
   bits in *FXSAVE.  */

void
i387_collect_fxsave (const struct regcache *regcache, int regnum, void *fxsave)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  char *regs = fxsave;
  int i;

  gdb_assert (tdep->st0_regnum >= I386_ST0_REGNUM);
  gdb_assert (tdep->num_xmm_regs > 0);

  /* Define I387_ST0_REGNUM and I387_NUM_XMM_REGS such that we use the
     proper definitions for REGCACHE's architecture.  */

#define I387_ST0_REGNUM	tdep->st0_regnum
#define I387_NUM_XMM_REGS tdep->num_xmm_regs

  for (i = I387_ST0_REGNUM; i < I387_MXCSR_REGNUM; i++)
    if (regnum == -1 || regnum == i)
      {
	/* Most of the FPU control registers occupy only 16 bits in
           the fxsave area.  Give those a special treatment.  */
	if (i >= I387_FCTRL_REGNUM && i < I387_XMM0_REGNUM
	    && i != I387_FIOFF_REGNUM && i != I387_FOOFF_REGNUM)
	  {
	    unsigned char buf[4];

	    regcache_raw_collect (regcache, i, buf);

	    if (i == I387_FOP_REGNUM)
	      {
		/* The opcode occupies only 11 bits.  Make sure we
                   don't touch the other bits.  */
		buf[1] &= ((1 << 3) - 1);
		buf[1] |= ((FXSAVE_ADDR (regs, i))[1] & ~((1 << 3) - 1));
	      }
	    else if (i == I387_FTAG_REGNUM)
	      {
		/* Converting back is much easier.  */

		unsigned short ftag;
		int fpreg;

		ftag = (buf[1] << 8) | buf[0];
		buf[0] = 0;
		buf[1] = 0;

		for (fpreg = 7; fpreg >= 0; fpreg--)
		  {
		    int tag = (ftag >> (fpreg * 2)) & 3;

		    if (tag != 3)
		      buf[0] |= (1 << fpreg);
		  }
	      }
	    memcpy (FXSAVE_ADDR (regs, i), buf, 2);
	  }
	else
	  regcache_raw_collect (regcache, i, FXSAVE_ADDR (regs, i));
      }

  if (regnum == I387_MXCSR_REGNUM || regnum == -1)
    regcache_raw_collect (regcache, I387_MXCSR_REGNUM,
			  FXSAVE_MXCSR_ADDR (regs));

#undef I387_ST0_REGNUM
#undef I387_NUM_XMM_REGS
}

/* Fill register REGNUM (if it is a floating-point or SSE register) in
   *FXSAVE with the value in GDB's register cache.  If REGNUM is -1, do
   this for all registers.  This function doesn't touch any of the
   reserved bits in *FXSAVE.  */

void
i387_fill_fxsave (void *fxsave, int regnum)
{
  i387_collect_fxsave (current_regcache, regnum, fxsave);
}

/* Recreate the FTW (tag word) valid bits from the 80-bit FP data in
   *RAW.  */

static int
i387_tag (const unsigned char *raw)
{
  int integer;
  unsigned int exponent;
  unsigned long fraction[2];

  integer = raw[7] & 0x80;
  exponent = (((raw[9] & 0x7f) << 8) | raw[8]);
  fraction[0] = ((raw[3] << 24) | (raw[2] << 16) | (raw[1] << 8) | raw[0]);
  fraction[1] = (((raw[7] & 0x7f) << 24) | (raw[6] << 16)
		 | (raw[5] << 8) | raw[4]);

  if (exponent == 0x7fff)
    {
      /* Special.  */
      return (2);
    }
  else if (exponent == 0x0000)
    {
      if (fraction[0] == 0x0000 && fraction[1] == 0x0000 && !integer)
	{
	  /* Zero.  */
	  return (1);
	}
      else
	{
	  /* Special.  */
	  return (2);
	}
    }
  else
    {
      if (integer)
	{
	  /* Valid.  */
	  return (0);
	}
      else
	{
	  /* Special.  */
	  return (2);
	}
    }
}

/* Prepare the FPU stack in REGCACHE for a function return.  */

void
i387_return_value (struct gdbarch *gdbarch, struct regcache *regcache)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
  ULONGEST fstat;

  /* Define I387_ST0_REGNUM such that we use the proper
     definitions for the architecture.  */
#define I387_ST0_REGNUM tdep->st0_regnum

  /* Set the top of the floating-point register stack to 7.  The
     actual value doesn't really matter, but 7 is what a normal
     function return would end up with if the program started out with
     a freshly initialized FPU.  */
  regcache_raw_read_unsigned (regcache, I387_FSTAT_REGNUM, &fstat);
  fstat |= (7 << 11);
  regcache_raw_write_unsigned (regcache, I387_FSTAT_REGNUM, fstat);

  /* Mark %st(1) through %st(7) as empty.  Since we set the top of the
     floating-point register stack to 7, the appropriate value for the
     tag word is 0x3fff.  */
  regcache_raw_write_unsigned (regcache, I387_FTAG_REGNUM, 0x3fff);

#undef I387_ST0_REGNUM
}