z80-dis.c

   1 /* Print Z80 and R800 instructions
   2    Copyright 2005 Free Software Foundation, Inc.
   3    Contributed by Arnold Metselaar <arnold_m@operamail.com>
   4
   5    Taken from GDB
   6
   7    This file is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  20    MA 02110-1301, USA.  */
  21
  22 #include "dis-asm.h"
  23 #include <stdio.h>
  24
  25 struct buffer
  26 {
  27   bfd_vma base;
  28   int n_fetch;
  29   int n_used;
  30   signed char data[4];
  31 } ;
  32
  33 typedef int (*func)(struct buffer *, disassemble_info *, const char *);
  34
  35 struct tab_elt
  36 {
  37   unsigned char val;
  38   unsigned char mask;
  39   func          fp;
  40   const char *  text;
  41 } ;
  42
  43 #define TXTSIZ 24
  44 /* Names of 16-bit registers.  */
  45 static const char * rr_str[] = { "bc", "de", "hl", "sp" };
  46 /* Names of 8-bit registers.  */
  47 static const char * r_str[]  = { "b", "c", "d", "e", "h", "l", "(hl)", "a" };
  48 /* Texts for condition codes.  */
  49 static const char * cc_str[] = { "nz", "z", "nc", "c", "po", "pe", "p", "m" };
  50 /* Instruction names for 8-bit arithmetic, operand "a" is often implicit */
  51 static const char * arit_str[] =
  52 {
  53   "add a,", "adc a,", "sub ", "sbc a,", "and ", "xor ", "or ", "cp "
  54 } ;
  55 \f
  56 static int
  57 fetch_data (struct buffer *buf, disassemble_info * info, int n)
  58 {
  59   int r;
  60
  61   if (buf->n_fetch + n > 4)
  62     abort ();
  63
  64   r = info->read_memory_func (buf->base + buf->n_fetch,
  65                               (unsigned char*) buf->data + buf->n_fetch,
  66                               n, info);
  67   if (r == 0)
  68     buf->n_fetch += n;
  69   return !r;
  70 }
  71
  72 static int
  73 prt (struct buffer *buf, disassemble_info * info, const char *txt)
  74 {
  75   info->fprintf_func (info->stream, "%s", txt);
  76   buf->n_used = buf->n_fetch;
  77   return 1;
  78 }
  79
  80 static int
  81 prt_e (struct buffer *buf, disassemble_info * info, const char *txt)
  82 {
  83   char e;
  84   int target_addr;
  85
  86   if (fetch_data (buf, info, 1))
  87     {
  88       e = buf->data[1];
  89       target_addr = (buf->base + 2 + e) & 0xffff;
  90       buf->n_used = buf->n_fetch;
  91       info->fprintf_func (info->stream, "%s0x%04x", txt, target_addr);
  92     }
  93   else
  94     buf->n_used = -1;
  95
  96   return buf->n_used;
  97 }
  98
  99 static int
 100 jr_cc (struct buffer *buf, disassemble_info * info, const char *txt)
 101 {
 102   char mytxt[TXTSIZ];
 103
 104   snprintf (mytxt, TXTSIZ, txt, cc_str[(buf->data[0] >> 3) & 3]);
 105   return prt_e (buf, info, mytxt);
 106 }
 107
 108 static int
 109 prt_nn (struct buffer *buf, disassemble_info * info, const char *txt)
 110 {
 111   int nn;
 112   unsigned char *p;
 113
 114   p = (unsigned char*) buf->data + buf->n_fetch;
 115   if (fetch_data (buf, info, 2))
 116     {
 117       nn = p[0] + (p[1] << 8);
 118       info->fprintf_func (info->stream, txt, nn);
 119       buf->n_used = buf->n_fetch;
 120     }
 121   else
 122     buf->n_used = -1;
 123   return buf->n_used;
 124 }
 125
 126 static int
 127 prt_rr_nn (struct buffer *buf, disassemble_info * info, const char *txt)
 128 {
 129   char mytxt[TXTSIZ];
 130
 131   snprintf (mytxt, TXTSIZ, txt, rr_str[(buf->data[0] >> 4) & 3]);
 132   return prt_nn (buf, info, mytxt);
 133 }
 134
 135 static int
 136 prt_rr (struct buffer *buf, disassemble_info * info, const char *txt)
 137 {
 138   info->fprintf_func (info->stream, "%s%s", txt,
 139                       rr_str[(buf->data[buf->n_fetch - 1] >> 4) & 3]);
 140   buf->n_used = buf->n_fetch;
 141   return buf->n_used;
 142 }
 143
 144 static int
 145 prt_n (struct buffer *buf, disassemble_info * info, const char *txt)
 146 {
 147   int n;
 148   unsigned char *p;
 149
 150   p = (unsigned char*) buf->data + buf->n_fetch;
 151
 152   if (fetch_data (buf, info, 1))
 153     {
 154       n = p[0];
 155       info->fprintf_func (info->stream, txt, n);
 156       buf->n_used = buf->n_fetch;
 157     }
 158   else
 159     buf->n_used = -1;
 160
 161   return buf->n_used;
 162 }
 163
 164 static int
 165 ld_r_n (struct buffer *buf, disassemble_info * info, const char *txt)
 166 {
 167   char mytxt[TXTSIZ];
 168
 169   snprintf (mytxt, TXTSIZ, txt, r_str[(buf->data[0] >> 3) & 7]);
 170   return prt_n (buf, info, mytxt);
 171 }
 172
 173 static int
 174 prt_r (struct buffer *buf, disassemble_info * info, const char *txt)
 175 {
 176   info->fprintf_func (info->stream, txt,
 177                       r_str[(buf->data[buf->n_fetch - 1] >> 3) & 7]);
 178   buf->n_used = buf->n_fetch;
 179   return buf->n_used;
 180 }
 181
 182 static int
 183 ld_r_r (struct buffer *buf, disassemble_info * info, const char *txt)
 184 {
 185   info->fprintf_func (info->stream, txt,
 186                       r_str[(buf->data[buf->n_fetch - 1] >> 3) & 7],
 187                       r_str[buf->data[buf->n_fetch - 1] & 7]);
 188   buf->n_used = buf->n_fetch;
 189   return buf->n_used;
 190 }
 191
 192 static int
 193 arit_r (struct buffer *buf, disassemble_info * info, const char *txt)
 194 {
 195   info->fprintf_func (info->stream, txt,
 196                       arit_str[(buf->data[buf->n_fetch - 1] >> 3) & 7],
 197                       r_str[buf->data[buf->n_fetch - 1] & 7]);
 198   buf->n_used = buf->n_fetch;
 199   return buf->n_used;
 200 }
 201
 202 static int
 203 prt_cc (struct buffer *buf, disassemble_info * info, const char *txt)
 204 {
 205   info->fprintf_func (info->stream, "%s%s", txt,
 206                       cc_str[(buf->data[0] >> 3) & 7]);
 207   buf->n_used = buf->n_fetch;
 208   return buf->n_used;
 209 }
 210
 211 static int
 212 pop_rr (struct buffer *buf, disassemble_info * info, const char *txt)
 213 {
 214   static const char *rr_stack[] = { "bc","de","hl","af"};
 215
 216   info->fprintf_func (info->stream, "%s %s", txt,
 217                       rr_stack[(buf->data[0] >> 4) & 3]);
 218   buf->n_used = buf->n_fetch;
 219   return buf->n_used;
 220 }
 221
 222
 223 static int
 224 jp_cc_nn (struct buffer *buf, disassemble_info * info, const char *txt)
 225 {
 226   char mytxt[TXTSIZ];
 227
 228   snprintf (mytxt,TXTSIZ,
 229             "%s%s,0x%%04x", txt, cc_str[(buf->data[0] >> 3) & 7]);
 230   return prt_nn (buf, info, mytxt);
 231 }
 232
 233 static int
 234 arit_n (struct buffer *buf, disassemble_info * info, const char *txt)
 235 {
 236   char mytxt[TXTSIZ];
 237
 238   snprintf (mytxt,TXTSIZ, txt, arit_str[(buf->data[0] >> 3) & 7]);
 239   return prt_n (buf, info, mytxt);
 240 }
 241
 242 static int
 243 rst (struct buffer *buf, disassemble_info * info, const char *txt)
 244 {
 245   info->fprintf_func (info->stream, txt, buf->data[0] & 0x38);
 246   buf->n_used = buf->n_fetch;
 247   return buf->n_used;
 248 }
 249
 250 \f
 251 static int
 252 cis (struct buffer *buf, disassemble_info * info, const char *txt ATTRIBUTE_UNUSED)
 253 {
 254   static const char * opar[] = { "ld", "cp", "in", "out" };
 255   const char * op;
 256   char c;
 257
 258   c = buf->data[1];
 259   op = ((0x13 & c) == 0x13) ? "ot" : (opar[c & 3]);
 260   info->fprintf_func (info->stream,
 261                       "%s%c%s", op,
 262                       (c & 0x08) ? 'd' : 'i',
 263                       (c & 0x10) ? "r" : "");
 264   buf->n_used = 2;
 265   return buf->n_used;
 266 }
 267
 268 static int
 269 dump (struct buffer *buf, disassemble_info * info, const char *txt)
 270 {
 271   int i;
 272
 273   info->fprintf_func (info->stream, "defb ");
 274   for (i = 0; txt[i]; ++i)
 275     info->fprintf_func (info->stream, i ? ", 0x%02x" : "0x%02x",
 276                         (unsigned char) buf->data[i]);
 277   buf->n_used = i;
 278   return buf->n_used;
 279 }
 280 \f
 281 /* Table to disassemble machine codes with prefix 0xED.  */
 282 struct tab_elt opc_ed[] =
 283 {
 284   { 0x70, 0xFF, prt, "in f,(c)" },
 285   { 0x70, 0xFF, dump, "xx" },
 286   { 0x40, 0xC7, prt_r, "in %s,(c)" },
 287   { 0x71, 0xFF, prt, "out (c),0" },
 288   { 0x70, 0xFF, dump, "xx" },
 289   { 0x41, 0xC7, prt_r, "out (c),%s" },
 290   { 0x42, 0xCF, prt_rr, "sbc hl," },
 291   { 0x43, 0xCF, prt_rr_nn, "ld (0x%%04x),%s" },
 292   { 0x44, 0xFF, prt, "neg" },
 293   { 0x45, 0xFF, prt, "retn" },
 294   { 0x46, 0xFF, prt, "im 0" },
 295   { 0x47, 0xFF, prt, "ld i,a" },
 296   { 0x4A, 0xCF, prt_rr, "adc hl," },
 297   { 0x4B, 0xCF, prt_rr_nn, "ld %s,(0x%%04x)" },
 298   { 0x4D, 0xFF, prt, "reti" },
 299   { 0x56, 0xFF, prt, "im 1" },
 300   { 0x57, 0xFF, prt, "ld a,i" },
 301   { 0x5E, 0xFF, prt, "im 2" },
 302   { 0x67, 0xFF, prt, "rrd" },
 303   { 0x6F, 0xFF, prt, "rld" },
 304   { 0xA0, 0xE4, cis, "" },
 305   { 0xC3, 0xFF, prt, "muluw hl,bc" },
 306   { 0xC5, 0xE7, prt_r, "mulub a,%s" },
 307   { 0xF3, 0xFF, prt, "muluw hl,sp" },
 308   { 0x00, 0x00, dump, "xx" }
 309 };
 310
 311 static int
 312 pref_ed (struct buffer * buf, disassemble_info * info,
 313          const char* txt ATTRIBUTE_UNUSED)
 314 {
 315   struct tab_elt *p;
 316
 317   if (fetch_data(buf, info, 1))
 318     {
 319       for (p = opc_ed; p->val != (buf->data[1] & p->mask); ++p)
 320         ;
 321       p->fp (buf, info, p->text);
 322     }
 323   else
 324     buf->n_used = -1;
 325
 326   return buf->n_used;
 327 }
 328 \f
 329 /* Instruction names for the instructions addressing single bits.  */
 330 static const char *cb1_str[] = { "", "bit", "res", "set"};
 331 /* Instruction names for shifts and rotates.  */
 332 static const char *cb2_str[] =
 333 {
 334   "rlc", "rrc", "rl", "rr", "sla", "sra", "sli", "srl"
 335 };
 336
 337 static int
 338 pref_cb (struct buffer * buf, disassemble_info * info,
 339          const char* txt ATTRIBUTE_UNUSED)
 340 {
 341   if (fetch_data (buf, info, 1))
 342     {
 343       buf->n_used = 2;
 344       if ((buf->data[1] & 0xc0) == 0)
 345         info->fprintf_func (info->stream, "%s %s",
 346                             cb2_str[(buf->data[1] >> 3) & 7],
 347                             r_str[buf->data[1] & 7]);
 348       else
 349         info->fprintf_func (info->stream, "%s %d,%s",
 350                             cb1_str[(buf->data[1] >> 6) & 3],
 351                             (buf->data[1] >> 3) & 7,
 352                             r_str[buf->data[1] & 7]);
 353     }
 354   else
 355     buf->n_used = -1;
 356
 357   return buf->n_used;
 358 }
 359 \f
 360 static int
 361 addvv (struct buffer * buf, disassemble_info * info, const char* txt)
 362 {
 363   info->fprintf_func (info->stream, "add %s,%s", txt, txt);
 364
 365   return buf->n_used = buf->n_fetch;
 366 }
 367
 368 static int
 369 ld_v_v (struct buffer * buf, disassemble_info * info, const char* txt)
 370 {
 371   char mytxt[TXTSIZ];
 372
 373   snprintf (mytxt, TXTSIZ, "ld %s%%s,%s%%s", txt, txt);
 374   return ld_r_r (buf, info, mytxt);
 375 }
 376
 377 static int
 378 prt_d (struct buffer *buf, disassemble_info * info, const char *txt)
 379 {
 380   int d;
 381   signed char *p;
 382
 383   p = buf->data + buf->n_fetch;
 384
 385   if (fetch_data (buf, info, 1))
 386     {
 387       d = p[0];
 388       info->fprintf_func (info->stream, txt, d);
 389       buf->n_used = buf->n_fetch;
 390     }
 391   else
 392     buf->n_used = -1;
 393
 394   return buf->n_used;
 395 }
 396
 397 static int
 398 prt_d_n (struct buffer *buf, disassemble_info * info, const char *txt)
 399 {
 400   char mytxt[TXTSIZ];
 401   int d;
 402   signed char *p;
 403
 404   p = buf->data + buf->n_fetch;
 405
 406   if (fetch_data (buf, info, 1))
 407     {
 408       d = p[0];
 409       snprintf (mytxt, TXTSIZ, txt, d);
 410       return prt_n (buf, info, mytxt);
 411     }
 412   else
 413     buf->n_used = -1;
 414
 415   return buf->n_used;
 416 }
 417
 418 static int
 419 arit_d (struct buffer *buf, disassemble_info * info, const char *txt)
 420 {
 421   char mytxt[TXTSIZ];
 422   signed char c;
 423
 424   c = buf->data[buf->n_fetch - 1];
 425   snprintf (mytxt, TXTSIZ, txt, arit_str[(c >> 3) & 7]);
 426   return prt_d (buf, info, mytxt);
 427 }
 428
 429 static int
 430 ld_r_d (struct buffer *buf, disassemble_info * info, const char *txt)
 431 {
 432   char mytxt[TXTSIZ];
 433   signed char c;
 434
 435   c = buf->data[buf->n_fetch - 1];
 436   snprintf (mytxt, TXTSIZ, txt, r_str[(c >> 3) & 7]);
 437   return prt_d (buf, info, mytxt);
 438 }
 439
 440 static int
 441 ld_d_r(struct buffer *buf, disassemble_info * info, const char *txt)
 442 {
 443   char mytxt[TXTSIZ];
 444   signed char c;
 445
 446   c = buf->data[buf->n_fetch - 1];
 447   snprintf (mytxt, TXTSIZ, txt, r_str[c & 7]);
 448   return prt_d (buf, info, mytxt);
 449 }
 450
 451 static int
 452 pref_xd_cb (struct buffer * buf, disassemble_info * info, const char* txt)
 453 {
 454   if (fetch_data (buf, info, 2))
 455     {
 456       int d;
 457       char arg[TXTSIZ];
 458       signed char *p;
 459
 460       buf->n_used = 4;
 461       p = buf->data;
 462       d = p[2];
 463
 464       if (((p[3] & 0xC0) == 0x40) || ((p[3] & 7) == 0x06))
 465         snprintf (arg, TXTSIZ, "(%s%+d)", txt, d);
 466       else
 467         snprintf (arg, TXTSIZ, "(%s%+d),%s", txt, d, r_str[p[3] & 7]);
 468
 469       if ((p[3] & 0xc0) == 0)
 470         info->fprintf_func (info->stream, "%s %s",
 471                             cb2_str[(buf->data[3] >> 3) & 7],
 472                             arg);
 473       else
 474         info->fprintf_func (info->stream, "%s %d,%s",
 475                             cb1_str[(buf->data[3] >> 6) & 3],
 476                             (buf->data[3] >> 3) & 7,
 477                             arg);
 478     }
 479   else
 480     buf->n_used = -1;
 481
 482   return buf->n_used;
 483 }
 484 \f
 485 /* Table to disassemble machine codes with prefix 0xDD or 0xFD.  */
 486 static struct tab_elt opc_ind[] =
 487 {
 488   { 0x24, 0xF7, prt_r, "inc %s%%s" },
 489   { 0x25, 0xF7, prt_r, "dec %s%%s" },
 490   { 0x26, 0xF7, ld_r_n, "ld %s%%s,0x%%%%02x" },
 491   { 0x21, 0xFF, prt_nn, "ld %s,0x%%04x" },
 492   { 0x22, 0xFF, prt_nn, "ld (0x%%04x),%s" },
 493   { 0x2A, 0xFF, prt_nn, "ld %s,(0x%%04x)" },
 494   { 0x23, 0xFF, prt, "inc %s" },
 495   { 0x2B, 0xFF, prt, "dec %s" },
 496   { 0x29, 0xFF, addvv, "%s" },
 497   { 0x09, 0xCF, prt_rr, "add %s," },
 498   { 0x34, 0xFF, prt_d, "inc (%s%%+d)" },
 499   { 0x35, 0xFF, prt_d, "dec (%s%%+d)" },
 500   { 0x36, 0xFF, prt_d_n, "ld (%s%%+d),0x%%%%02x" },
 501
 502   { 0x76, 0xFF, dump, "h" },
 503   { 0x46, 0xC7, ld_r_d, "ld %%s,(%s%%%%+d)" },
 504   { 0x70, 0xF8, ld_d_r, "ld (%s%%%%+d),%%s" },
 505   { 0x64, 0xF6, ld_v_v, "%s" },
 506   { 0x60, 0xF0, ld_r_r, "ld %s%%s,%%s" },
 507   { 0x44, 0xC6, ld_r_r, "ld %%s,%s%%s" },
 508
 509   { 0x86, 0xC7, arit_d, "%%s(%s%%%%+d)" },
 510   { 0x84, 0xC6, arit_r, "%%s%s%%s" },
 511
 512   { 0xE1, 0xFF, prt, "pop %s" },
 513   { 0xE5, 0xFF, prt, "push %s" },
 514   { 0xCB, 0xFF, pref_xd_cb, "%s" },
 515   { 0xE3, 0xFF, prt, "ex (sp),%s" },
 516   { 0xE9, 0xFF, prt, "jp (%s)" },
 517   { 0xF9, 0xFF, prt, "ld sp,%s" },
 518   { 0x00, 0x00, dump, "?" },
 519 } ;
 520
 521 static int
 522 pref_ind (struct buffer * buf, disassemble_info * info, const char* txt)
 523 {
 524   if (fetch_data (buf, info, 1))
 525     {
 526       char mytxt[TXTSIZ];
 527       struct tab_elt *p;
 528
 529       for (p = opc_ind; p->val != (buf->data[1] & p->mask); ++p)
 530         ;
 531       snprintf (mytxt, TXTSIZ, p->text, txt);
 532       p->fp (buf, info, mytxt);
 533     }
 534   else
 535     buf->n_used = -1;
 536
 537   return buf->n_used;
 538 }
 539
 540 /* Table to disassemble machine codes without prefix.  */
 541 static struct tab_elt opc_main[] =
 542 {
 543   { 0x00, 0xFF, prt, "nop" },
 544   { 0x01, 0xCF, prt_rr_nn, "ld %s,0x%%04x" },
 545   { 0x02, 0xFF, prt, "ld (bc),a" },
 546   { 0x03, 0xCF, prt_rr, "inc " },
 547   { 0x04, 0xC7, prt_r, "inc %s" },
 548   { 0x05, 0xC7, prt_r, "dec %s" },
 549   { 0x06, 0xC7, ld_r_n, "ld %s,0x%%02x" },
 550   { 0x07, 0xFF, prt, "rlca" },
 551   { 0x08, 0xFF, prt, "ex af,af'" },
 552   { 0x09, 0xCF, prt_rr, "add hl," },
 553   { 0x0A, 0xFF, prt, "ld a,(bc)" },
 554   { 0x0B, 0xCF, prt_rr, "dec " },
 555   { 0x0F, 0xFF, prt, "rrca" },
 556   { 0x10, 0xFF, prt_e, "djnz " },
 557   { 0x12, 0xFF, prt, "ld (de),a" },
 558   { 0x17, 0xFF, prt, "rla" },
 559   { 0x18, 0xFF, prt_e, "jr "},
 560   { 0x1A, 0xFF, prt, "ld a,(de)" },
 561   { 0x1F, 0xFF, prt, "rra" },
 562   { 0x20, 0xE7, jr_cc, "jr %s,"},
 563   { 0x22, 0xFF, prt_nn, "ld (0x%04x),hl" },
 564   { 0x27, 0xFF, prt, "daa"},
 565   { 0x2A, 0xFF, prt_nn, "ld hl,(0x%04x)" },
 566   { 0x2F, 0xFF, prt, "cpl" },
 567   { 0x32, 0xFF, prt_nn, "ld (0x%04x),a" },
 568   { 0x37, 0xFF, prt, "scf" },
 569   { 0x3A, 0xFF, prt_nn, "ld a,(0x%04x)" },
 570   { 0x3F, 0xFF, prt, "ccf" },
 571
 572   { 0x76, 0xFF, prt, "halt" },
 573   { 0x40, 0xC0, ld_r_r, "ld %s,%s"},
 574
 575   { 0x80, 0xC0, arit_r, "%s%s" },
 576
 577   { 0xC0, 0xC7, prt_cc, "ret " },
 578   { 0xC1, 0xCF, pop_rr, "pop" },
 579   { 0xC2, 0xC7, jp_cc_nn, "jp " },
 580   { 0xC3, 0xFF, prt_nn, "jp 0x%04x" },
 581   { 0xC4, 0xC7, jp_cc_nn, "call " },
 582   { 0xC5, 0xCF, pop_rr, "push" },
 583   { 0xC6, 0xC7, arit_n, "%s0x%%02x" },
 584   { 0xC7, 0xC7, rst, "rst 0x%02x" },
 585   { 0xC9, 0xFF, prt, "ret" },
 586   { 0xCB, 0xFF, pref_cb, "" },
 587   { 0xCD, 0xFF, prt_nn, "call 0x%04x" },
 588   { 0xD3, 0xFF, prt_n, "out (0x%02x),a" },
 589   { 0xD9, 0xFF, prt, "exx" },
 590   { 0xDB, 0xFF, prt_n, "in a,(0x%02x)" },
 591   { 0xDD, 0xFF, pref_ind, "ix" },
 592   { 0xE3, 0xFF, prt, "ex (sp),hl" },
 593   { 0xE9, 0xFF, prt, "jp (hl)" },
 594   { 0xEB, 0xFF, prt, "ex de,hl" },
 595   { 0xED, 0xFF, pref_ed, ""},
 596   { 0xF3, 0xFF, prt, "di" },
 597   { 0xF9, 0xFF, prt, "ld sp,hl" },
 598   { 0xFB, 0xFF, prt, "ei" },
 599   { 0xFD, 0xFF, pref_ind, "iy" },
 600   { 0x00, 0x00, prt, "????" },
 601 } ;
 602
 603 int
 604 print_insn_z80 (bfd_vma addr, disassemble_info * info)
 605 {
 606   struct buffer buf;
 607   struct tab_elt *p;
 608
 609   buf.base = addr;
 610   buf.n_fetch = 0;
 611   buf.n_used = 0;
 612
 613   if (! fetch_data (& buf, info, 1))
 614     return -1;
 615
 616   for (p = opc_main; p->val != (buf.data[0] & p->mask); ++p)
 617     ;
 618   p->fp (& buf, info, p->text);
 619
 620   return buf.n_used;
 621 }