gdb/i387-tdep.c

   1 /* Intel 387 floating point stuff.
   2
   3    Copyright 1988, 1989, 1991, 1992, 1993, 1994, 1998, 1999, 2000,
   4    2001, 2002, 2003, 2004 Free Software Foundation, Inc.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 59 Temple Place - Suite 330,
  21    Boston, MA 02111-1307, USA.  */
  22
  23 #include "defs.h"
  24 #include "doublest.h"
  25 #include "floatformat.h"
  26 #include "frame.h"
  27 #include "gdbcore.h"
  28 #include "inferior.h"
  29 #include "language.h"
  30 #include "regcache.h"
  31 #include "value.h"
  32
  33 #include "gdb_assert.h"
  34 #include "gdb_string.h"
  35
  36 #include "i386-tdep.h"
  37 #include "i387-tdep.h"
  38
  39 /* Implement the `info float' layout based on the register definitions
  40    in `tm-i386.h'.  */
  41
  42 /* Print the floating point number specified by RAW.  */
  43
  44 static void
  45 print_i387_value (char *raw, struct ui_file *file)
  46 {
  47   DOUBLEST value;
  48
  49   /* Using extract_typed_floating here might affect the representation
  50      of certain numbers such as NaNs, even if GDB is running natively.
  51      This is fine since our caller already detects such special
  52      numbers and we print the hexadecimal representation anyway.  */
  53   value = extract_typed_floating (raw, builtin_type_i387_ext);
  54
  55   /* We try to print 19 digits.  The last digit may or may not contain
  56      garbage, but we'd better print one too many.  We need enough room
  57      to print the value, 1 position for the sign, 1 for the decimal
  58      point, 19 for the digits and 6 for the exponent adds up to 27.  */
  59 #ifdef PRINTF_HAS_LONG_DOUBLE
  60   fprintf_filtered (file, " %-+27.19Lg", (long double) value);
  61 #else
  62   fprintf_filtered (file, " %-+27.19g", (double) value);
  63 #endif
  64 }
  65
  66 /* Print the classification for the register contents RAW.  */
  67
  68 static void
  69 print_i387_ext (unsigned char *raw, struct ui_file *file)
  70 {
  71   int sign;
  72   int integer;
  73   unsigned int exponent;
  74   unsigned long fraction[2];
  75
  76   sign = raw[9] & 0x80;
  77   integer = raw[7] & 0x80;
  78   exponent = (((raw[9] & 0x7f) << 8) | raw[8]);
  79   fraction[0] = ((raw[3] << 24) | (raw[2] << 16) | (raw[1] << 8) | raw[0]);
  80   fraction[1] = (((raw[7] & 0x7f) << 24) | (raw[6] << 16)
  81                  | (raw[5] << 8) | raw[4]);
  82
  83   if (exponent == 0x7fff && integer)
  84     {
  85       if (fraction[0] == 0x00000000 && fraction[1] == 0x00000000)
  86         /* Infinity.  */
  87         fprintf_filtered (file, " %cInf", (sign ? '-' : '+'));
  88       else if (sign && fraction[0] == 0x00000000 && fraction[1] == 0x40000000)
  89         /* Real Indefinite (QNaN).  */
  90         fputs_unfiltered (" Real Indefinite (QNaN)", file);
  91       else if (fraction[1] & 0x40000000)
  92         /* QNaN.  */
  93         fputs_filtered (" QNaN", file);
  94       else
  95         /* SNaN.  */
  96         fputs_filtered (" SNaN", file);
  97     }
  98   else if (exponent < 0x7fff && exponent > 0x0000 && integer)
  99     /* Normal.  */
 100     print_i387_value (raw, file);
 101   else if (exponent == 0x0000)
 102     {
 103       /* Denormal or zero.  */
 104       print_i387_value (raw, file);
 105
 106       if (integer)
 107         /* Pseudo-denormal.  */
 108         fputs_filtered (" Pseudo-denormal", file);
 109       else if (fraction[0] || fraction[1])
 110         /* Denormal.  */
 111         fputs_filtered (" Denormal", file);
 112     }
 113   else
 114     /* Unsupported.  */
 115     fputs_filtered (" Unsupported", file);
 116 }
 117
 118 /* Print the status word STATUS.  */
 119
 120 static void
 121 print_i387_status_word (unsigned int status, struct ui_file *file)
 122 {
 123   fprintf_filtered (file, "Status Word:         %s",
 124                    local_hex_string_custom (status, "04"));
 125   fputs_filtered ("  ", file);
 126   fprintf_filtered (file, " %s", (status & 0x0001) ? "IE" : "  ");
 127   fprintf_filtered (file, " %s", (status & 0x0002) ? "DE" : "  ");
 128   fprintf_filtered (file, " %s", (status & 0x0004) ? "ZE" : "  ");
 129   fprintf_filtered (file, " %s", (status & 0x0008) ? "OE" : "  ");
 130   fprintf_filtered (file, " %s", (status & 0x0010) ? "UE" : "  ");
 131   fprintf_filtered (file, " %s", (status & 0x0020) ? "PE" : "  ");
 132   fputs_filtered ("  ", file);
 133   fprintf_filtered (file, " %s", (status & 0x0080) ? "ES" : "  ");
 134   fputs_filtered ("  ", file);
 135   fprintf_filtered (file, " %s", (status & 0x0040) ? "SF" : "  ");
 136   fputs_filtered ("  ", file);
 137   fprintf_filtered (file, " %s", (status & 0x0100) ? "C0" : "  ");
 138   fprintf_filtered (file, " %s", (status & 0x0200) ? "C1" : "  ");
 139   fprintf_filtered (file, " %s", (status & 0x0400) ? "C2" : "  ");
 140   fprintf_filtered (file, " %s", (status & 0x4000) ? "C3" : "  ");
 141
 142   fputs_filtered ("\n", file);
 143
 144   fprintf_filtered (file,
 145                     "                       TOP: %d\n", ((status >> 11) & 7));
 146 }
 147
 148 /* Print the control word CONTROL.  */
 149
 150 static void
 151 print_i387_control_word (unsigned int control, struct ui_file *file)
 152 {
 153   fprintf_filtered (file, "Control Word:        %s",
 154                    local_hex_string_custom (control, "04"));
 155   fputs_filtered ("  ", file);
 156   fprintf_filtered (file, " %s", (control & 0x0001) ? "IM" : "  ");
 157   fprintf_filtered (file, " %s", (control & 0x0002) ? "DM" : "  ");
 158   fprintf_filtered (file, " %s", (control & 0x0004) ? "ZM" : "  ");
 159   fprintf_filtered (file, " %s", (control & 0x0008) ? "OM" : "  ");
 160   fprintf_filtered (file, " %s", (control & 0x0010) ? "UM" : "  ");
 161   fprintf_filtered (file, " %s", (control & 0x0020) ? "PM" : "  ");
 162
 163   fputs_filtered ("\n", file);
 164
 165   fputs_filtered ("                       PC: ", file);
 166   switch ((control >> 8) & 3)
 167     {
 168     case 0:
 169       fputs_filtered ("Single Precision (24-bits)\n", file);
 170       break;
 171     case 1:
 172       fputs_filtered ("Reserved\n", file);
 173       break;
 174     case 2:
 175       fputs_filtered ("Double Precision (53-bits)\n", file);
 176       break;
 177     case 3:
 178       fputs_filtered ("Extended Precision (64-bits)\n", file);
 179       break;
 180     }
 181
 182   fputs_filtered ("                       RC: ", file);
 183   switch ((control >> 10) & 3)
 184     {
 185     case 0:
 186       fputs_filtered ("Round to nearest\n", file);
 187       break;
 188     case 1:
 189       fputs_filtered ("Round down\n", file);
 190       break;
 191     case 2:
 192       fputs_filtered ("Round up\n", file);
 193       break;
 194     case 3:
 195       fputs_filtered ("Round toward zero\n", file);
 196       break;
 197     }
 198 }
 199
 200 /* Print out the i387 floating point state.  Note that we ignore FRAME
 201    in the code below.  That's OK since floating-point registers are
 202    never saved on the stack.  */
 203
 204 void
 205 i387_print_float_info (struct gdbarch *gdbarch, struct ui_file *file,
 206                        struct frame_info *frame, const char *args)
 207 {
 208   struct gdbarch_tdep *tdep = gdbarch_tdep (get_frame_arch (frame));
 209   char buf[4];
 210   ULONGEST fctrl;
 211   ULONGEST fstat;
 212   ULONGEST ftag;
 213   ULONGEST fiseg;
 214   ULONGEST fioff;
 215   ULONGEST foseg;
 216   ULONGEST fooff;
 217   ULONGEST fop;
 218   int fpreg;
 219   int top;
 220
 221   gdb_assert (gdbarch == get_frame_arch (frame));
 222
 223   /* Define I387_ST0_REGNUM such that we use the proper definitions
 224      for FRAME's architecture.  */
 225 #define I387_ST0_REGNUM tdep->st0_regnum
 226
 227   fctrl = get_frame_register_unsigned (frame, I387_FCTRL_REGNUM);
 228   fstat = get_frame_register_unsigned (frame, I387_FSTAT_REGNUM);
 229   ftag = get_frame_register_unsigned (frame, I387_FTAG_REGNUM);
 230   fiseg = get_frame_register_unsigned (frame, I387_FISEG_REGNUM);
 231   fioff = get_frame_register_unsigned (frame, I387_FIOFF_REGNUM);
 232   foseg = get_frame_register_unsigned (frame, I387_FOSEG_REGNUM);
 233   fooff = get_frame_register_unsigned (frame, I387_FOOFF_REGNUM);
 234   fop = get_frame_register_unsigned (frame, I387_FOP_REGNUM);
 235
 236   top = ((fstat >> 11) & 7);
 237
 238   for (fpreg = 7; fpreg >= 0; fpreg--)
 239     {
 240       unsigned char raw[I386_MAX_REGISTER_SIZE];
 241       int tag = (ftag >> (fpreg * 2)) & 3;
 242       int i;
 243
 244       fprintf_filtered (file, "%sR%d: ", fpreg == top ? "=>" : "  ", fpreg);
 245
 246       switch (tag)
 247         {
 248         case 0:
 249           fputs_filtered ("Valid   ", file);
 250           break;
 251         case 1:
 252           fputs_filtered ("Zero    ", file);
 253           break;
 254         case 2:
 255           fputs_filtered ("Special ", file);
 256           break;
 257         case 3:
 258           fputs_filtered ("Empty   ", file);
 259           break;
 260         }
 261
 262       get_frame_register (frame, (fpreg + 8 - top) % 8 + I387_ST0_REGNUM, raw);
 263
 264       fputs_filtered ("0x", file);
 265       for (i = 9; i >= 0; i--)
 266         fprintf_filtered (file, "%02x", raw[i]);
 267
 268       if (tag != 3)
 269         print_i387_ext (raw, file);
 270
 271       fputs_filtered ("\n", file);
 272     }
 273
 274   fputs_filtered ("\n", file);
 275
 276   print_i387_status_word (fstat, file);
 277   print_i387_control_word (fctrl, file);
 278   fprintf_filtered (file, "Tag Word:            %s\n",
 279                     local_hex_string_custom (ftag, "04"));
 280   fprintf_filtered (file, "Instruction Pointer: %s:",
 281                     local_hex_string_custom (fiseg, "02"));
 282   fprintf_filtered (file, "%s\n", local_hex_string_custom (fioff, "08"));
 283   fprintf_filtered (file, "Operand Pointer:     %s:",
 284                     local_hex_string_custom (foseg, "02"));
 285   fprintf_filtered (file, "%s\n", local_hex_string_custom (fooff, "08"));
 286   fprintf_filtered (file, "Opcode:              %s\n",
 287                     local_hex_string_custom (fop ? (fop | 0xd800) : 0, "04"));
 288
 289 #undef I387_ST0_REGNUM
 290 }
 291 \f
 292
 293 /* Read a value of type TYPE from register REGNUM in frame FRAME, and
 294    return its contents in TO.  */
 295
 296 void
 297 i387_register_to_value (struct frame_info *frame, int regnum,
 298                         struct type *type, void *to)
 299 {
 300   char from[I386_MAX_REGISTER_SIZE];
 301
 302   gdb_assert (i386_fp_regnum_p (regnum));
 303
 304   /* We only support floating-point values.  */
 305   if (TYPE_CODE (type) != TYPE_CODE_FLT)
 306     {
 307       warning ("Cannot convert floating-point register value "
 308                "to non-floating-point type.");
 309       return;
 310     }
 311
 312   /* Convert to TYPE.  This should be a no-op if TYPE is equivalent to
 313      the extended floating-point format used by the FPU.  */
 314   get_frame_register (frame, regnum, from);
 315   convert_typed_floating (from, builtin_type_i387_ext, to, type);
 316 }
 317
 318 /* Write the contents FROM of a value of type TYPE into register
 319    REGNUM in frame FRAME.  */
 320
 321 void
 322 i387_value_to_register (struct frame_info *frame, int regnum,
 323                         struct type *type, const void *from)
 324 {
 325   char to[I386_MAX_REGISTER_SIZE];
 326
 327   gdb_assert (i386_fp_regnum_p (regnum));
 328
 329   /* We only support floating-point values.  */
 330   if (TYPE_CODE (type) != TYPE_CODE_FLT)
 331     {
 332       warning ("Cannot convert non-floating-point type "
 333                "to floating-point register value.");
 334       return;
 335     }
 336
 337   /* Convert from TYPE.  This should be a no-op if TYPE is equivalent
 338      to the extended floating-point format used by the FPU.  */
 339   convert_typed_floating (from, type, to, builtin_type_i387_ext);
 340   put_frame_register (frame, regnum, to);
 341 }
 342 \f
 343
 344 /* Handle FSAVE and FXSAVE formats.  */
 345
 346 /* FIXME: kettenis/20030927: The functions below should accept a
 347    `regcache' argument, but I don't want to change the function
 348    signature just yet.  There's some band-aid in the functions below
 349    in the form of the `regcache' local variables.  This will ease the
 350    transition later on.  */
 351
 352 /* At fsave_offset[REGNUM] you'll find the offset to the location in
 353    the data structure used by the "fsave" instruction where GDB
 354    register REGNUM is stored.  */
 355
 356 static int fsave_offset[] =
 357 {
 358   28 + 0 * 10,                  /* %st(0) ...  */
 359   28 + 1 * 10,
 360   28 + 2 * 10,
 361   28 + 3 * 10,
 362   28 + 4 * 10,
 363   28 + 5 * 10,
 364   28 + 6 * 10,
 365   28 + 7 * 10,                  /* ... %st(7).  */
 366   0,                            /* `fctrl' (16 bits).  */
 367   4,                            /* `fstat' (16 bits).  */
 368   8,                            /* `ftag' (16 bits).  */
 369   16,                           /* `fiseg' (16 bits).  */
 370   12,                           /* `fioff'.  */
 371   24,                           /* `foseg' (16 bits).  */
 372   20,                           /* `fooff'.  */
 373   18                            /* `fop' (bottom 11 bits).  */
 374 };
 375
 376 #define FSAVE_ADDR(fsave, regnum) \
 377   (fsave + fsave_offset[regnum - I387_ST0_REGNUM])
 378 \f
 379
 380 /* Fill register REGNUM in REGCACHE with the appropriate value from
 381    *FSAVE.  This function masks off any of the reserved bits in
 382    *FSAVE.  */
 383
 384 void
 385 i387_supply_fsave (struct regcache *regcache, int regnum, const void *fsave)
 386 {
 387   struct gdbarch_tdep *tdep = gdbarch_tdep (get_regcache_arch (regcache));
 388   const char *regs = fsave;
 389   int i;
 390
 391   gdb_assert (tdep->st0_regnum >= I386_ST0_REGNUM);
 392
 393   /* Define I387_ST0_REGNUM and I387_NUM_XMM_REGS such that we use the
 394      proper definitions for REGCACHE's architecture.  */
 395
 396 #define I387_ST0_REGNUM tdep->st0_regnum
 397 #define I387_NUM_XMM_REGS tdep->num_xmm_regs
 398
 399   for (i = I387_ST0_REGNUM; i < I387_XMM0_REGNUM; i++)
 400     if (regnum == -1 || regnum == i)
 401       {
 402         if (fsave == NULL)
 403           {
 404             regcache_raw_supply (regcache, i, NULL);
 405             continue;
 406           }
 407
 408         /* Most of the FPU control registers occupy only 16 bits in the
 409            fsave area.  Give those a special treatment.  */
 410         if (i >= I387_FCTRL_REGNUM
 411             && i != I387_FIOFF_REGNUM && i != I387_FOOFF_REGNUM)
 412           {
 413             unsigned char val[4];
 414
 415             memcpy (val, FSAVE_ADDR (regs, i), 2);
 416             val[2] = val[3] = 0;
 417             if (i == I387_FOP_REGNUM)
 418               val[1] &= ((1 << 3) - 1);
 419             regcache_raw_supply (regcache, i, val);
 420           }
 421         else
 422           regcache_raw_supply (regcache, i, FSAVE_ADDR (regs, i));
 423       }
 424
 425   /* Provide dummy values for the SSE registers.  */
 426   for (i = I387_XMM0_REGNUM; i < I387_MXCSR_REGNUM; i++)
 427     if (regnum == -1 || regnum == i)
 428       regcache_raw_supply (regcache, i, NULL);
 429   if (regnum == -1 || regnum == I387_MXCSR_REGNUM)
 430     {
 431       char buf[4];
 432
 433       store_unsigned_integer (buf, 4, 0x1f80);
 434       regcache_raw_supply (regcache, I387_MXCSR_REGNUM, buf);
 435     }
 436
 437 #undef I387_ST0_REGNUM
 438 #undef I387_NUM_XMM_REGS
 439 }
 440
 441 /* Fill register REGNUM (if it is a floating-point register) in *FSAVE
 442    with the value from REGCACHE.  If REGNUM is -1, do this for all
 443    registers.  This function doesn't touch any of the reserved bits in
 444    *FSAVE.  */
 445
 446 void
 447 i387_collect_fsave (const struct regcache *regcache, int regnum, void *fsave)
 448 {
 449   struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
 450   char *regs = fsave;
 451   int i;
 452
 453   gdb_assert (tdep->st0_regnum >= I386_ST0_REGNUM);
 454
 455   /* Define I387_ST0_REGNUM such that we use the proper definitions
 456      for REGCACHE's architecture.  */
 457 #define I387_ST0_REGNUM tdep->st0_regnum
 458
 459   for (i = I387_ST0_REGNUM; i < I387_XMM0_REGNUM; i++)
 460     if (regnum == -1 || regnum == i)
 461       {
 462         /* Most of the FPU control registers occupy only 16 bits in
 463            the fsave area.  Give those a special treatment.  */
 464         if (i >= I387_FCTRL_REGNUM
 465             && i != I387_FIOFF_REGNUM && i != I387_FOOFF_REGNUM)
 466           {
 467             unsigned char buf[4];
 468
 469             regcache_raw_collect (regcache, i, buf);
 470
 471             if (i == I387_FOP_REGNUM)
 472               {
 473                 /* The opcode occupies only 11 bits.  Make sure we
 474                    don't touch the other bits.  */
 475                 buf[1] &= ((1 << 3) - 1);
 476                 buf[1] |= ((FSAVE_ADDR (regs, i))[1] & ~((1 << 3) - 1));
 477               }
 478             memcpy (FSAVE_ADDR (regs, i), buf, 2);
 479           }
 480         else
 481           regcache_raw_collect (regcache, i, FSAVE_ADDR (regs, i));
 482       }
 483 #undef I387_ST0_REGNUM
 484 }
 485
 486 /* Fill register REGNUM (if it is a floating-point register) in *FSAVE
 487    with the value in GDB's register cache.  If REGNUM is -1, do this
 488    for all registers.  This function doesn't touch any of the reserved
 489    bits in *FSAVE.  */
 490
 491 void
 492 i387_fill_fsave (void *fsave, int regnum)
 493 {
 494   i387_collect_fsave (current_regcache, regnum, fsave);
 495 }
 496 \f
 497
 498 /* At fxsave_offset[REGNUM] you'll find the offset to the location in
 499    the data structure used by the "fxsave" instruction where GDB
 500    register REGNUM is stored.  */
 501
 502 static int fxsave_offset[] =
 503 {
 504   32,                           /* %st(0) through ...  */
 505   48,
 506   64,
 507   80,
 508   96,
 509   112,
 510   128,
 511   144,                          /* ... %st(7) (80 bits each).  */
 512   0,                            /* `fctrl' (16 bits).  */
 513   2,                            /* `fstat' (16 bits).  */
 514   4,                            /* `ftag' (16 bits).  */
 515   12,                           /* `fiseg' (16 bits).  */
 516   8,                            /* `fioff'.  */
 517   20,                           /* `foseg' (16 bits).  */
 518   16,                           /* `fooff'.  */
 519   6,                            /* `fop' (bottom 11 bits).  */
 520   160 + 0 * 16,                 /* %xmm0 through ...  */
 521   160 + 1 * 16,
 522   160 + 2 * 16,
 523   160 + 3 * 16,
 524   160 + 4 * 16,
 525   160 + 5 * 16,
 526   160 + 6 * 16,
 527   160 + 7 * 16,
 528   160 + 8 * 16,
 529   160 + 9 * 16,
 530   160 + 10 * 16,
 531   160 + 11 * 16,
 532   160 + 12 * 16,
 533   160 + 13 * 16,
 534   160 + 14 * 16,
 535   160 + 15 * 16,                /* ... %xmm15 (128 bits each).  */
 536 };
 537
 538 #define FXSAVE_ADDR(fxsave, regnum) \
 539   (fxsave + fxsave_offset[regnum - I387_ST0_REGNUM])
 540
 541 /* We made an unfortunate choice in putting %mxcsr after the SSE
 542    registers %xmm0-%xmm7 instead of before, since it makes supporting
 543    the registers %xmm8-%xmm15 on AMD64 a bit involved.  Therefore we
 544    don't include the offset for %mxcsr here above.  */
 545
 546 #define FXSAVE_MXCSR_ADDR(fxsave) (fxsave + 24)
 547
 548 static int i387_tag (const unsigned char *raw);
 549 \f
 550
 551 /* Fill register REGNUM in REGCACHE with the appropriate
 552    floating-point or SSE register value from *FXSAVE.  This function
 553    masks off any of the reserved bits in *FXSAVE.  */
 554
 555 void
 556 i387_supply_fxsave (struct regcache *regcache, int regnum, const void *fxsave)
 557 {
 558   struct gdbarch_tdep *tdep = gdbarch_tdep (get_regcache_arch (regcache));
 559   const char *regs = fxsave;
 560   int i;
 561
 562   gdb_assert (tdep->st0_regnum >= I386_ST0_REGNUM);
 563   gdb_assert (tdep->num_xmm_regs > 0);
 564
 565   /* Define I387_ST0_REGNUM and I387_NUM_XMM_REGS such that we use the
 566      proper definitions for REGCACHE's architecture.  */
 567
 568 #define I387_ST0_REGNUM tdep->st0_regnum
 569 #define I387_NUM_XMM_REGS tdep->num_xmm_regs
 570
 571   for (i = I387_ST0_REGNUM; i < I387_MXCSR_REGNUM; i++)
 572     if (regnum == -1 || regnum == i)
 573       {
 574         if (regs == NULL)
 575           {
 576             regcache_raw_supply (regcache, i, NULL);
 577             continue;
 578           }
 579
 580         /* Most of the FPU control registers occupy only 16 bits in
 581            the fxsave area.  Give those a special treatment.  */
 582         if (i >= I387_FCTRL_REGNUM && i < I387_XMM0_REGNUM
 583             && i != I387_FIOFF_REGNUM && i != I387_FOOFF_REGNUM)
 584           {
 585             unsigned char val[4];
 586
 587             memcpy (val, FXSAVE_ADDR (regs, i), 2);
 588             val[2] = val[3] = 0;
 589             if (i == I387_FOP_REGNUM)
 590               val[1] &= ((1 << 3) - 1);
 591             else if (i== I387_FTAG_REGNUM)
 592               {
 593                 /* The fxsave area contains a simplified version of
 594                    the tag word.  We have to look at the actual 80-bit
 595                    FP data to recreate the traditional i387 tag word.  */
 596
 597                 unsigned long ftag = 0;
 598                 int fpreg;
 599                 int top;
 600
 601                 top = ((FXSAVE_ADDR (regs, I387_FSTAT_REGNUM))[1] >> 3);
 602                 top &= 0x7;
 603
 604                 for (fpreg = 7; fpreg >= 0; fpreg--)
 605                   {
 606                     int tag;
 607
 608                     if (val[0] & (1 << fpreg))
 609                       {
 610                         int regnum = (fpreg + 8 - top) % 8 + I387_ST0_REGNUM;
 611                         tag = i387_tag (FXSAVE_ADDR (regs, regnum));
 612                       }
 613                     else
 614                       tag = 3;          /* Empty */
 615
 616                     ftag |= tag << (2 * fpreg);
 617                   }
 618                 val[0] = ftag & 0xff;
 619                 val[1] = (ftag >> 8) & 0xff;
 620               }
 621             regcache_raw_supply (regcache, i, val);
 622           }
 623         else
 624           regcache_raw_supply (regcache, i, FXSAVE_ADDR (regs, i));
 625       }
 626
 627   if (regnum == I387_MXCSR_REGNUM || regnum == -1)
 628     {
 629       if (regs == NULL)
 630         regcache_raw_supply (regcache, I387_MXCSR_REGNUM, NULL);
 631       else
 632         regcache_raw_supply (regcache, I387_MXCSR_REGNUM,
 633                              FXSAVE_MXCSR_ADDR (regs));
 634     }
 635
 636 #undef I387_ST0_REGNUM
 637 #undef I387_NUM_XMM_REGS
 638 }
 639
 640 /* Fill register REGNUM (if it is a floating-point or SSE register) in
 641    *FXSAVE with the value from REGCACHE.  If REGNUM is -1, do this for
 642    all registers.  This function doesn't touch any of the reserved
 643    bits in *FXSAVE.  */
 644
 645 void
 646 i387_collect_fxsave (const struct regcache *regcache, int regnum, void *fxsave)
 647 {
 648   struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
 649   char *regs = fxsave;
 650   int i;
 651
 652   gdb_assert (tdep->st0_regnum >= I386_ST0_REGNUM);
 653   gdb_assert (tdep->num_xmm_regs > 0);
 654
 655   /* Define I387_ST0_REGNUM and I387_NUM_XMM_REGS such that we use the
 656      proper definitions for REGCACHE's architecture.  */
 657
 658 #define I387_ST0_REGNUM tdep->st0_regnum
 659 #define I387_NUM_XMM_REGS tdep->num_xmm_regs
 660
 661   for (i = I387_ST0_REGNUM; i < I387_MXCSR_REGNUM; i++)
 662     if (regnum == -1 || regnum == i)
 663       {
 664         /* Most of the FPU control registers occupy only 16 bits in
 665            the fxsave area.  Give those a special treatment.  */
 666         if (i >= I387_FCTRL_REGNUM && i < I387_XMM0_REGNUM
 667             && i != I387_FIOFF_REGNUM && i != I387_FOOFF_REGNUM)
 668           {
 669             unsigned char buf[4];
 670
 671             regcache_raw_collect (regcache, i, buf);
 672
 673             if (i == I387_FOP_REGNUM)
 674               {
 675                 /* The opcode occupies only 11 bits.  Make sure we
 676                    don't touch the other bits.  */
 677                 buf[1] &= ((1 << 3) - 1);
 678                 buf[1] |= ((FXSAVE_ADDR (regs, i))[1] & ~((1 << 3) - 1));
 679               }
 680             else if (i == I387_FTAG_REGNUM)
 681               {
 682                 /* Converting back is much easier.  */
 683
 684                 unsigned short ftag;
 685                 int fpreg;
 686
 687                 ftag = (buf[1] << 8) | buf[0];
 688                 buf[0] = 0;
 689                 buf[1] = 0;
 690
 691                 for (fpreg = 7; fpreg >= 0; fpreg--)
 692                   {
 693                     int tag = (ftag >> (fpreg * 2)) & 3;
 694
 695                     if (tag != 3)
 696                       buf[0] |= (1 << fpreg);
 697                   }
 698               }
 699             memcpy (FXSAVE_ADDR (regs, i), buf, 2);
 700           }
 701         else
 702           regcache_raw_collect (regcache, i, FXSAVE_ADDR (regs, i));
 703       }
 704
 705   if (regnum == I387_MXCSR_REGNUM || regnum == -1)
 706     regcache_raw_collect (regcache, I387_MXCSR_REGNUM,
 707                           FXSAVE_MXCSR_ADDR (regs));
 708
 709 #undef I387_ST0_REGNUM
 710 #undef I387_NUM_XMM_REGS
 711 }
 712
 713 /* Fill register REGNUM (if it is a floating-point or SSE register) in
 714    *FXSAVE with the value in GDB's register cache.  If REGNUM is -1, do
 715    this for all registers.  This function doesn't touch any of the
 716    reserved bits in *FXSAVE.  */
 717
 718 void
 719 i387_fill_fxsave (void *fxsave, int regnum)
 720 {
 721   i387_collect_fxsave (current_regcache, regnum, fxsave);
 722 }
 723
 724 /* Recreate the FTW (tag word) valid bits from the 80-bit FP data in
 725    *RAW.  */
 726
 727 static int
 728 i387_tag (const unsigned char *raw)
 729 {
 730   int integer;
 731   unsigned int exponent;
 732   unsigned long fraction[2];
 733
 734   integer = raw[7] & 0x80;
 735   exponent = (((raw[9] & 0x7f) << 8) | raw[8]);
 736   fraction[0] = ((raw[3] << 24) | (raw[2] << 16) | (raw[1] << 8) | raw[0]);
 737   fraction[1] = (((raw[7] & 0x7f) << 24) | (raw[6] << 16)
 738                  | (raw[5] << 8) | raw[4]);
 739
 740   if (exponent == 0x7fff)
 741     {
 742       /* Special.  */
 743       return (2);
 744     }
 745   else if (exponent == 0x0000)
 746     {
 747       if (fraction[0] == 0x0000 && fraction[1] == 0x0000 && !integer)
 748         {
 749           /* Zero.  */
 750           return (1);
 751         }
 752       else
 753         {
 754           /* Special.  */
 755           return (2);
 756         }
 757     }
 758   else
 759     {
 760       if (integer)
 761         {
 762           /* Valid.  */
 763           return (0);
 764         }
 765       else
 766         {
 767           /* Special.  */
 768           return (2);
 769         }
 770     }
 771 }
 772
 773 /* Prepare the FPU stack in REGCACHE for a function return.  */
 774
 775 void
 776 i387_return_value (struct gdbarch *gdbarch, struct regcache *regcache)
 777 {
 778   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 779   ULONGEST fstat;
 780
 781   /* Define I387_ST0_REGNUM such that we use the proper
 782      definitions for the architecture.  */
 783 #define I387_ST0_REGNUM tdep->st0_regnum
 784
 785   /* Set the top of the floating-point register stack to 7.  The
 786      actual value doesn't really matter, but 7 is what a normal
 787      function return would end up with if the program started out with
 788      a freshly initialized FPU.  */
 789   regcache_raw_read_unsigned (regcache, I387_FSTAT_REGNUM, &fstat);
 790   fstat |= (7 << 11);
 791   regcache_raw_write_unsigned (regcache, I387_FSTAT_REGNUM, fstat);
 792
 793   /* Mark %st(1) through %st(7) as empty.  Since we set the top of the
 794      floating-point register stack to 7, the appropriate value for the
 795      tag word is 0x3fff.  */
 796   regcache_raw_write_unsigned (regcache, I387_FTAG_REGNUM, 0x3fff);
 797
 798 #undef I387_ST0_REGNUM
 799 }