aboutsummaryrefslogtreecommitdiff
path: root/gas/config/tc-wasm32.c
blob: 9e36fdb37e4af314204ab4e733ed5b0599aad78b (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
/* tc-wasm32.c -- Assembler code for the wasm32 target.

   Copyright (C) 2017-2022 Free Software Foundation, Inc.

   This file is part of GAS, the GNU Assembler.

   GAS 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 3, or (at your option)
   any later version.

   GAS 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 GAS; see the file COPYING.  If not, write to the Free
   Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
   02110-1301, USA.  */

#include "as.h"
#include "safe-ctype.h"
#include "subsegs.h"
#include "dwarf2dbg.h"
#include "dw2gencfi.h"
#include "elf/wasm32.h"
#include <float.h>

enum wasm_class
{
  wasm_typed,			/* a typed opcode: block, loop, or if */
  wasm_special,			/* a special opcode: unreachable, nop, else,
				   or end */
  wasm_break,			/* "br" */
  wasm_break_if,		/* "br_if" opcode */
  wasm_break_table,		/* "br_table" opcode */
  wasm_return,			/* "return" opcode */
  wasm_call,			/* "call" opcode */
  wasm_call_indirect,		/* "call_indirect" opcode */
  wasm_get_local,		/* "get_local" and "get_global" */
  wasm_set_local,		/* "set_local" and "set_global" */
  wasm_tee_local,		/* "tee_local" */
  wasm_drop,			/* "drop" */
  wasm_constant_i32,		/* "i32.const" */
  wasm_constant_i64,		/* "i64.const" */
  wasm_constant_f32,		/* "f32.const" */
  wasm_constant_f64,		/* "f64.const" */
  wasm_unary,			/* unary operators */
  wasm_binary,			/* binary operators */
  wasm_conv,			/* conversion operators */
  wasm_load,			/* load operators */
  wasm_store,			/* store operators */
  wasm_select,			/* "select" */
  wasm_relational,		/* comparison operators, except for "eqz" */
  wasm_eqz,			/* "eqz" */
  wasm_current_memory,		/* "current_memory" */
  wasm_grow_memory,		/* "grow_memory" */
  wasm_signature		/* "signature", which isn't an opcode */
};

#define WASM_OPCODE(opcode, name, intype, outtype, class, signedness)   \
  { name, wasm_ ## class, opcode },

struct wasm32_opcode_s
{
  const char *name;
  enum wasm_class clas;
  unsigned char opcode;
} wasm32_opcodes[] =
{
#include "opcode/wasm.h"
  {
  NULL, 0, 0}
};

const char comment_chars[] = ";#";
const char line_comment_chars[] = ";#";
const char line_separator_chars[] = "";

const char *md_shortopts = "m:";

const char EXP_CHARS[] = "eE";
const char FLT_CHARS[] = "dD";

/* The target specific pseudo-ops which we support.  */

const pseudo_typeS md_pseudo_table[] =
{
  {NULL, NULL, 0}
};

/* Opcode hash table.  */

static htab_t wasm32_hash;

struct option md_longopts[] =
{
  {NULL, no_argument, NULL, 0}
};

size_t md_longopts_size = sizeof (md_longopts);

/* No relaxation/no machine-dependent frags.  */

int
md_estimate_size_before_relax (fragS * fragp ATTRIBUTE_UNUSED,
			       asection * seg ATTRIBUTE_UNUSED)
{
  abort ();
  return 0;
}

void
md_show_usage (FILE * stream)
{
  fprintf (stream, _("wasm32 assembler options:\n"));
}

/* No machine-dependent options.  */

int
md_parse_option (int c ATTRIBUTE_UNUSED, const char *arg ATTRIBUTE_UNUSED)
{
  return 0;
}

/* No machine-dependent symbols.  */

symbolS *
md_undefined_symbol (char *name ATTRIBUTE_UNUSED)
{
  return NULL;
}

/* IEEE little-endian floats.  */

const char *
md_atof (int type, char *litP, int *sizeP)
{
  return ieee_md_atof (type, litP, sizeP, false);
}

/* No machine-dependent frags.  */

void
md_convert_frag (bfd * abfd ATTRIBUTE_UNUSED,
		 asection * sec ATTRIBUTE_UNUSED,
		 fragS * fragP ATTRIBUTE_UNUSED)
{
  abort ();
}

/* Build opcode hash table, set some flags.  */

void
md_begin (void)
{
  struct wasm32_opcode_s *opcode;

  wasm32_hash = str_htab_create ();

  /* Insert unique names into hash table.  This hash table then
     provides a quick index to the first opcode with a particular name
     in the opcode table.  */
  for (opcode = wasm32_opcodes; opcode->name; opcode++)
    str_hash_insert (wasm32_hash, opcode->name, opcode, 0);

  linkrelax = 0;
  flag_sectname_subst = 1;
  flag_no_comments = 0;
  flag_keep_locals = 1;
}

/* Do the normal thing for md_section_align.  */

valueT
md_section_align (asection * seg, valueT addr)
{
  int align = bfd_section_alignment (seg);
  return ((addr + (1 << align) - 1) & -(1 << align));
}

/* Apply a fixup, return TRUE if done (and no relocation is
   needed).  */

static bool
apply_full_field_fix (fixS * fixP, char *buf, bfd_vma val, int size)
{
  if (fixP->fx_addsy != NULL || fixP->fx_pcrel)
    {
      fixP->fx_addnumber = val;
      return false;
    }

  number_to_chars_littleendian (buf, val, size);
  return true;
}

/* Apply a fixup (potentially PC-relative), set the fx_done flag if
   done.  */

void
md_apply_fix (fixS * fixP, valueT * valP, segT seg ATTRIBUTE_UNUSED)
{
  char *buf = fixP->fx_where + fixP->fx_frag->fr_literal;
  long val = (long) *valP;

  if (fixP->fx_pcrel)
    {
      switch (fixP->fx_r_type)
	{
	default:
	  bfd_set_error (bfd_error_bad_value);
	  return;

	case BFD_RELOC_32:
	  fixP->fx_r_type = BFD_RELOC_32_PCREL;
	  return;
	}
    }

  if (apply_full_field_fix (fixP, buf, val, fixP->fx_size))
    fixP->fx_done = 1;
}

/* Skip whitespace.  */

static inline char *
skip_space (char *s)
{
  while (*s == ' ' || *s == '\t')
    ++s;
  return s;
}

/* Allow '/' in opcodes.  */

static inline bool
is_part_of_opcode (char c)
{
  return is_part_of_name (c) || (c == '/');
}

/* Extract an opcode.  */

static char *
extract_opcode (char *from, char *to, int limit)
{
  char *op_end;
  int size = 0;

  /* Drop leading whitespace.  */
  from = skip_space (from);
  *to = 0;

  /* Find the op code end.  */
  for (op_end = from; *op_end != 0 && is_part_of_opcode (*op_end);)
    {
      to[size++] = *op_end++;
      if (size + 1 >= limit)
	break;
    }

  to[size] = 0;
  return op_end;
}

/* Produce an unsigned LEB128 integer padded to the right number of
   bytes to store BITS bits, of value VALUE.  Uses FRAG_APPEND_1_CHAR
   to write.  */

static void
wasm32_put_long_uleb128 (int bits, unsigned long value)
{
  unsigned char c;
  int i = 0;

  do
    {
      c = value & 0x7f;
      value >>= 7;
      if (i < (bits - 1) / 7)
	c |= 0x80;
      FRAG_APPEND_1_CHAR (c);
    }
  while (++i < (bits + 6) / 7);
}

/* Produce a signed LEB128 integer, using FRAG_APPEND_1_CHAR to
   write.  */

static void
wasm32_put_sleb128 (long value)
{
  unsigned char c;
  int more;

  do
    {
      c = (value & 0x7f);
      value >>= 7;
      more = !((((value == 0) && ((c & 0x40) == 0))
		|| ((value == -1) && ((c & 0x40) != 0))));
      if (more)
	c |= 0x80;
      FRAG_APPEND_1_CHAR (c);
    }
  while (more);
}

/* Produce an unsigned LEB128 integer, using FRAG_APPEND_1_CHAR to
   write.  */

static void
wasm32_put_uleb128 (unsigned long value)
{
  unsigned char c;

  do
    {
      c = value & 0x7f;
      value >>= 7;
      if (value)
	c |= 0x80;
      FRAG_APPEND_1_CHAR (c);
    }
  while (value);
}

/* Read an integer expression.  Produce an LEB128-encoded integer if
   it's a constant, a padded LEB128 plus a relocation if it's a
   symbol, or a special relocation for <expr>@got, <expr>@gotcode, and
   <expr>@plt{__sigchar_<signature>}.  */

static bool
wasm32_leb128 (char **line, int bits, int sign)
{
  char *t = input_line_pointer;
  char *str = *line;
  char *str0 = str;
  struct reloc_list *reloc;
  expressionS ex;
  int gotrel = 0;
  int pltrel = 0;
  int code = 0;
  const char *relname;

  input_line_pointer = str;
  expression (&ex);

  if (ex.X_op == O_constant && *input_line_pointer != '@')
    {
      long value = ex.X_add_number;

      str = input_line_pointer;
      str = skip_space (str);
      *line = str;
      if (sign)
	wasm32_put_sleb128 (value);
      else
	{
	  if (value < 0)
	    as_bad (_("unexpected negative constant"));
	  wasm32_put_uleb128 (value);
	}
      input_line_pointer = t;
      return str != str0;
    }

  reloc = XNEW (struct reloc_list);
  reloc->u.a.offset_sym = expr_build_dot ();
  if (ex.X_op == O_symbol)
    {
      reloc->u.a.sym = ex.X_add_symbol;
      reloc->u.a.addend = ex.X_add_number;
    }
  else
    {
      reloc->u.a.sym = make_expr_symbol (&ex);
      reloc->u.a.addend = 0;
    }
  /* i32.const fpointer@gotcode */
  if (startswith (input_line_pointer, "@gotcode"))
    {
      gotrel = 1;
      code = 1;
      input_line_pointer += 8;
    }
  /* i32.const data@got */
  else if (startswith (input_line_pointer, "@got"))
    {
      gotrel = 1;
      input_line_pointer += 4;
    }
  /* call f@plt{__sigchar_FiiiiE} */
  else if (startswith (input_line_pointer, "@plt"))
    {
      char *end_of_sig;

      pltrel = 1;
      code = 1;
      input_line_pointer += 4;

      if (startswith (input_line_pointer, "{")
          && (end_of_sig = strchr (input_line_pointer, '}')))
	{
	  char *signature;
	  struct reloc_list *reloc2;
	  size_t siglength = end_of_sig - (input_line_pointer + 1);

	  signature = strndup (input_line_pointer + 1, siglength);

	  reloc2 = XNEW (struct reloc_list);
	  reloc2->u.a.offset_sym = expr_build_dot ();
	  reloc2->u.a.sym = symbol_find_or_make (signature);
	  reloc2->u.a.addend = 0;
	  reloc2->u.a.howto = bfd_reloc_name_lookup
	    (stdoutput, "R_WASM32_PLT_SIG");
	  reloc2->next = reloc_list;
	  reloc_list = reloc2;
	  input_line_pointer = end_of_sig + 1;
	}
      else
	{
	  as_bad (_("no function type on PLT reloc"));
	}
    }

  if (gotrel && code)
    relname = "R_WASM32_LEB128_GOT_CODE";
  else if (gotrel)
    relname = "R_WASM32_LEB128_GOT";
  else if (pltrel)
    relname = "R_WASM32_LEB128_PLT";
  else
    relname = "R_WASM32_LEB128";

  reloc->u.a.howto = bfd_reloc_name_lookup (stdoutput, relname);
  if (!reloc->u.a.howto)
    as_bad (_("couldn't find relocation to use"));
  reloc->file = as_where (&reloc->line);
  reloc->next = reloc_list;
  reloc_list = reloc;

  str = input_line_pointer;
  str = skip_space (str);
  *line = str;
  wasm32_put_long_uleb128 (bits, 0);
  input_line_pointer = t;

  return str != str0;
}

/* Read an integer expression and produce an unsigned LEB128 integer,
   or a relocation for it.  */

static bool
wasm32_uleb128 (char **line, int bits)
{
  return wasm32_leb128 (line, bits, 0);
}

/* Read an integer expression and produce a signed LEB128 integer, or
   a relocation for it.  */

static bool
wasm32_sleb128 (char **line, int bits)
{
  return wasm32_leb128 (line, bits, 1);
}

/* Read an f32.  (Like float_cons ('f')).  */

static void
wasm32_f32 (char **line)
{
  char *t = input_line_pointer;

  input_line_pointer = *line;
  float_cons ('f');
  *line = input_line_pointer;
  input_line_pointer = t;
}

/* Read an f64.  (Like float_cons ('d')).  */

static void
wasm32_f64 (char **line)
{
  char *t = input_line_pointer;

  input_line_pointer = *line;
  float_cons ('d');
  *line = input_line_pointer;
  input_line_pointer = t;
}

/* Assemble a signature from LINE, replacing it with the new input
   pointer.  Signatures are simple expressions matching the regexp
   F[ilfd]*v?E, and interpreted as though they were C++-mangled
   function types on a 64-bit machine. */

static void
wasm32_signature (char **line)
{
  unsigned long count = 0;
  char *str = *line;
  char *ostr;
  char *result;

  if (*str++ != 'F')
    as_bad (_("Not a function type"));
  result = str;
  ostr = str + 1;
  str++;

  while (*str != 'E')
    {
      switch (*str++)
	{
	case 'i':
	case 'l':
	case 'f':
	case 'd':
	  count++;
	  break;
	default:
	  as_bad (_("Unknown type %c\n"), str[-1]);
	}
    }
  wasm32_put_uleb128 (count);
  str = ostr;
  while (*str != 'E')
    {
      switch (*str++)
	{
	case 'i':
	  FRAG_APPEND_1_CHAR (BLOCK_TYPE_I32);
	  break;
	case 'l':
	  FRAG_APPEND_1_CHAR (BLOCK_TYPE_I64);
	  break;
	case 'f':
	  FRAG_APPEND_1_CHAR (BLOCK_TYPE_F32);
	  break;
	case 'd':
	  FRAG_APPEND_1_CHAR (BLOCK_TYPE_F64);
	  break;
	default:
	  as_bad (_("Unknown type"));
	}
    }
  str++;
  switch (*result)
    {
    case 'v':
      FRAG_APPEND_1_CHAR (0x00);	/* no return value */
      break;
    case 'i':
      FRAG_APPEND_1_CHAR (0x01);	/* one return value */
      FRAG_APPEND_1_CHAR (BLOCK_TYPE_I32);
      break;
    case 'l':
      FRAG_APPEND_1_CHAR (0x01);	/* one return value */
      FRAG_APPEND_1_CHAR (BLOCK_TYPE_I64);
      break;
    case 'f':
      FRAG_APPEND_1_CHAR (0x01);	/* one return value */
      FRAG_APPEND_1_CHAR (BLOCK_TYPE_F32);
      break;
    case 'd':
      FRAG_APPEND_1_CHAR (0x01);	/* one return value */
      FRAG_APPEND_1_CHAR (BLOCK_TYPE_F64);
      break;
    default:
      as_bad (_("Unknown type"));
    }
  *line = str;
}

/* Main operands function.  Read the operands for OPCODE from LINE,
   replacing it with the new input pointer.  */

static void
wasm32_operands (struct wasm32_opcode_s *opcode, char **line)
{
  char *str = *line;
  unsigned long block_type = 0;

  FRAG_APPEND_1_CHAR (opcode->opcode);
  str = skip_space (str);
  if (str[0] == '[')
    {
      if (opcode->clas == wasm_typed)
	{
	  str++;
	  block_type = BLOCK_TYPE_NONE;
	  if (str[0] != ']')
	    {
	      str = skip_space (str);
	      switch (str[0])
		{
		case 'i':
		  block_type = BLOCK_TYPE_I32;
		  str++;
		  break;
		case 'l':
		  block_type = BLOCK_TYPE_I64;
		  str++;
		  break;
		case 'f':
		  block_type = BLOCK_TYPE_F32;
		  str++;
		  break;
		case 'd':
		  block_type = BLOCK_TYPE_F64;
		  str++;
		  break;
		}
	      str = skip_space (str);
	      if (str[0] == ']')
		str++;
	      else
		as_bad (_("only single block types allowed"));
	      str = skip_space (str);
	    }
	  else
	    {
	      str++;
	      str = skip_space (str);
	    }
	}
      else
	as_bad (_("instruction does not take a block type"));
    }

  switch (opcode->clas)
    {
    case wasm_drop:
    case wasm_special:
    case wasm_binary:
    case wasm_unary:
    case wasm_relational:
    case wasm_select:
    case wasm_eqz:
    case wasm_conv:
    case wasm_return:
      break;
    case wasm_typed:
      if (block_type == 0)
	as_bad (_("missing block type"));
      FRAG_APPEND_1_CHAR (block_type);
      break;
    case wasm_store:
    case wasm_load:
      if (str[0] == 'a' && str[1] == '=')
	{
	  str += 2;
	  if (!wasm32_uleb128 (&str, 32))
	    as_bad (_("missing alignment hint"));
	}
      else
	{
	  as_bad (_("missing alignment hint"));
	}
      str = skip_space (str);
      if (!wasm32_uleb128 (&str, 32))
	as_bad (_("missing offset"));
      break;
    case wasm_set_local:
    case wasm_get_local:
    case wasm_tee_local:
      if (!wasm32_uleb128 (&str, 32))
	as_bad (_("missing local index"));
      break;
    case wasm_break:
    case wasm_break_if:
      if (!wasm32_uleb128 (&str, 32))
	as_bad (_("missing break count"));
      break;
    case wasm_current_memory:
    case wasm_grow_memory:
      if (!wasm32_uleb128 (&str, 32))
	as_bad (_("missing reserved current_memory/grow_memory argument"));
      break;
    case wasm_call:
      if (!wasm32_uleb128 (&str, 32))
	as_bad (_("missing call argument"));
      break;
    case wasm_call_indirect:
      if (!wasm32_uleb128 (&str, 32))
	as_bad (_("missing call signature"));
      if (!wasm32_uleb128 (&str, 32))
	as_bad (_("missing table index"));
      break;
    case wasm_constant_i32:
      wasm32_sleb128 (&str, 32);
      break;
    case wasm_constant_i64:
      wasm32_sleb128 (&str, 64);
      break;
    case wasm_constant_f32:
      wasm32_f32 (&str);
      return;
    case wasm_constant_f64:
      wasm32_f64 (&str);
      return;
    case wasm_break_table:
      {
	do
	  {
	    wasm32_uleb128 (&str, 32);
	    str = skip_space (str);
	  }
	while (str[0]);

	break;
      }
    case wasm_signature:
      wasm32_signature (&str);
    }
  str = skip_space (str);

  if (*str)
    as_bad (_("junk at end of line, first unrecognized character is `%c'"),
	    *str);

  *line = str;

  return;
}

/* Main assembly function.  Find the opcode and call
   wasm32_operands().  */

void
md_assemble (char *str)
{
  char op[32];
  char *t;
  struct wasm32_opcode_s *opcode;

  str = skip_space (extract_opcode (str, op, sizeof (op)));

  if (!op[0])
    as_bad (_("can't find opcode "));

  opcode = (struct wasm32_opcode_s *) str_hash_find (wasm32_hash, op);

  if (opcode == NULL)
    {
      as_bad (_("unknown opcode `%s'"), op);
      return;
    }

  dwarf2_emit_insn (0);

  t = input_line_pointer;
  wasm32_operands (opcode, &str);
  input_line_pointer = t;
}

/* Don't replace PLT/GOT relocations with section symbols, so they
   don't get an addend.  */

int
wasm32_force_relocation (fixS * f)
{
  if (f->fx_r_type == BFD_RELOC_WASM32_LEB128_PLT
      || f->fx_r_type == BFD_RELOC_WASM32_LEB128_GOT)
    return 1;

  return 0;
}

/* Don't replace PLT/GOT relocations with section symbols, so they
   don't get an addend.  */

bool
wasm32_fix_adjustable (fixS * fixP)
{
  if (fixP->fx_addsy == NULL)
    return true;

  if (fixP->fx_r_type == BFD_RELOC_WASM32_LEB128_PLT
      || fixP->fx_r_type == BFD_RELOC_WASM32_LEB128_GOT)
    return false;

  return true;
}

/* Generate a reloc for FIXP.  */

arelent *
tc_gen_reloc (asection * sec ATTRIBUTE_UNUSED, fixS * fixp)
{
  arelent *reloc;

  reloc = (arelent *) xmalloc (sizeof (*reloc));
  reloc->sym_ptr_ptr = (asymbol **) xmalloc (sizeof (asymbol *));
  *reloc->sym_ptr_ptr = symbol_get_bfdsym (fixp->fx_addsy);
  reloc->address = fixp->fx_frag->fr_address + fixp->fx_where;

  /* Make sure none of our internal relocations make it this far.
     They'd better have been fully resolved by this point.  */
  gas_assert ((int) fixp->fx_r_type > 0);

  reloc->howto = bfd_reloc_type_lookup (stdoutput, fixp->fx_r_type);
  if (reloc->howto == NULL)
    {
      as_bad_where (fixp->fx_file, fixp->fx_line,
		    _("cannot represent `%s' relocation in object file"),
		    bfd_get_reloc_code_name (fixp->fx_r_type));
      return NULL;
    }

  reloc->addend = fixp->fx_offset;

  return reloc;
}