gdb/i387-tdep.c

   1 /* Intel 387 floating point stuff.
   2
   3    Copyright (C) 1988, 1989, 1991, 1992, 1993, 1994, 1998, 1999, 2000, 2001,
   4    2002, 2003, 2004, 2005, 2007 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 3 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, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include "defs.h"
  22 #include "doublest.h"
  23 #include "floatformat.h"
  24 #include "frame.h"
  25 #include "gdbcore.h"
  26 #include "inferior.h"
  27 #include "language.h"
  28 #include "regcache.h"
  29 #include "value.h"
  30
  31 #include "gdb_assert.h"
  32 #include "gdb_string.h"
  33
  34 #include "i386-tdep.h"
  35 #include "i387-tdep.h"
  36
  37 /* Print the floating point number specified by RAW.  */
  38
  39 static void
  40 print_i387_value (const gdb_byte *raw, struct ui_file *file)
  41 {
  42   DOUBLEST value;
  43
  44   /* Using extract_typed_floating here might affect the representation
  45      of certain numbers such as NaNs, even if GDB is running natively.
  46      This is fine since our caller already detects such special
  47      numbers and we print the hexadecimal representation anyway.  */
  48   value = extract_typed_floating (raw, builtin_type_i387_ext);
  49
  50   /* We try to print 19 digits.  The last digit may or may not contain
  51      garbage, but we'd better print one too many.  We need enough room
  52      to print the value, 1 position for the sign, 1 for the decimal
  53      point, 19 for the digits and 6 for the exponent adds up to 27.  */
  54 #ifdef PRINTF_HAS_LONG_DOUBLE
  55   fprintf_filtered (file, " %-+27.19Lg", (long double) value);
  56 #else
  57   fprintf_filtered (file, " %-+27.19g", (double) value);
  58 #endif
  59 }
  60
  61 /* Print the classification for the register contents RAW.  */
  62
  63 static void
  64 print_i387_ext (const gdb_byte *raw, struct ui_file *file)
  65 {
  66   int sign;
  67   int integer;
  68   unsigned int exponent;
  69   unsigned long fraction[2];
  70
  71   sign = raw[9] & 0x80;
  72   integer = raw[7] & 0x80;
  73   exponent = (((raw[9] & 0x7f) << 8) | raw[8]);
  74   fraction[0] = ((raw[3] << 24) | (raw[2] << 16) | (raw[1] << 8) | raw[0]);
  75   fraction[1] = (((raw[7] & 0x7f) << 24) | (raw[6] << 16)
  76                  | (raw[5] << 8) | raw[4]);
  77
  78   if (exponent == 0x7fff && integer)
  79     {
  80       if (fraction[0] == 0x00000000 && fraction[1] == 0x00000000)
  81         /* Infinity.  */
  82         fprintf_filtered (file, " %cInf", (sign ? '-' : '+'));
  83       else if (sign && fraction[0] == 0x00000000 && fraction[1] == 0x40000000)
  84         /* Real Indefinite (QNaN).  */
  85         fputs_unfiltered (" Real Indefinite (QNaN)", file);
  86       else if (fraction[1] & 0x40000000)
  87         /* QNaN.  */
  88         fputs_filtered (" QNaN", file);
  89       else
  90         /* SNaN.  */
  91         fputs_filtered (" SNaN", file);
  92     }
  93   else if (exponent < 0x7fff && exponent > 0x0000 && integer)
  94     /* Normal.  */
  95     print_i387_value (raw, file);
  96   else if (exponent == 0x0000)
  97     {
  98       /* Denormal or zero.  */
  99       print_i387_value (raw, file);
 100
 101       if (integer)
 102         /* Pseudo-denormal.  */
 103         fputs_filtered (" Pseudo-denormal", file);
 104       else if (fraction[0] || fraction[1])
 105         /* Denormal.  */
 106         fputs_filtered (" Denormal", file);
 107     }
 108   else
 109     /* Unsupported.  */
 110     fputs_filtered (" Unsupported", file);
 111 }
 112
 113 /* Print the status word STATUS.  */
 114
 115 static void
 116 print_i387_status_word (unsigned int status, struct ui_file *file)
 117 {
 118   fprintf_filtered (file, "Status Word:         %s",
 119                     hex_string_custom (status, 4));
 120   fputs_filtered ("  ", file);
 121   fprintf_filtered (file, " %s", (status & 0x0001) ? "IE" : "  ");
 122   fprintf_filtered (file, " %s", (status & 0x0002) ? "DE" : "  ");
 123   fprintf_filtered (file, " %s", (status & 0x0004) ? "ZE" : "  ");
 124   fprintf_filtered (file, " %s", (status & 0x0008) ? "OE" : "  ");
 125   fprintf_filtered (file, " %s", (status & 0x0010) ? "UE" : "  ");
 126   fprintf_filtered (file, " %s", (status & 0x0020) ? "PE" : "  ");
 127   fputs_filtered ("  ", file);
 128   fprintf_filtered (file, " %s", (status & 0x0080) ? "ES" : "  ");
 129   fputs_filtered ("  ", file);
 130   fprintf_filtered (file, " %s", (status & 0x0040) ? "SF" : "  ");
 131   fputs_filtered ("  ", file);
 132   fprintf_filtered (file, " %s", (status & 0x0100) ? "C0" : "  ");
 133   fprintf_filtered (file, " %s", (status & 0x0200) ? "C1" : "  ");
 134   fprintf_filtered (file, " %s", (status & 0x0400) ? "C2" : "  ");
 135   fprintf_filtered (file, " %s", (status & 0x4000) ? "C3" : "  ");
 136
 137   fputs_filtered ("\n", file);
 138
 139   fprintf_filtered (file,
 140                     "                       TOP: %d\n", ((status >> 11) & 7));
 141 }
 142
 143 /* Print the control word CONTROL.  */
 144
 145 static void
 146 print_i387_control_word (unsigned int control, struct ui_file *file)
 147 {
 148   fprintf_filtered (file, "Control Word:        %s",
 149                     hex_string_custom (control, 4));
 150   fputs_filtered ("  ", file);
 151   fprintf_filtered (file, " %s", (control & 0x0001) ? "IM" : "  ");
 152   fprintf_filtered (file, " %s", (control & 0x0002) ? "DM" : "  ");
 153   fprintf_filtered (file, " %s", (control & 0x0004) ? "ZM" : "  ");
 154   fprintf_filtered (file, " %s", (control & 0x0008) ? "OM" : "  ");
 155   fprintf_filtered (file, " %s", (control & 0x0010) ? "UM" : "  ");
 156   fprintf_filtered (file, " %s", (control & 0x0020) ? "PM" : "  ");
 157
 158   fputs_filtered ("\n", file);
 159
 160   fputs_filtered ("                       PC: ", file);
 161   switch ((control >> 8) & 3)
 162     {
 163     case 0:
 164       fputs_filtered ("Single Precision (24-bits)\n", file);
 165       break;
 166     case 1:
 167       fputs_filtered ("Reserved\n", file);
 168       break;
 169     case 2:
 170       fputs_filtered ("Double Precision (53-bits)\n", file);
 171       break;
 172     case 3:
 173       fputs_filtered ("Extended Precision (64-bits)\n", file);
 174       break;
 175     }
 176
 177   fputs_filtered ("                       RC: ", file);
 178   switch ((control >> 10) & 3)
 179     {
 180     case 0:
 181       fputs_filtered ("Round to nearest\n", file);
 182       break;
 183     case 1:
 184       fputs_filtered ("Round down\n", file);
 185       break;
 186     case 2:
 187       fputs_filtered ("Round up\n", file);
 188       break;
 189     case 3:
 190       fputs_filtered ("Round toward zero\n", file);
 191       break;
 192     }
 193 }
 194
 195 /* Print out the i387 floating point state.  Note that we ignore FRAME
 196    in the code below.  That's OK since floating-point registers are
 197    never saved on the stack.  */
 198
 199 void
 200 i387_print_float_info (struct gdbarch *gdbarch, struct ui_file *file,
 201                        struct frame_info *frame, const char *args)
 202 {
 203   struct gdbarch_tdep *tdep = gdbarch_tdep (get_frame_arch (frame));
 204   gdb_byte buf[4];
 205   ULONGEST fctrl;
 206   ULONGEST fstat;
 207   ULONGEST ftag;
 208   ULONGEST fiseg;
 209   ULONGEST fioff;
 210   ULONGEST foseg;
 211   ULONGEST fooff;
 212   ULONGEST fop;
 213   int fpreg;
 214   int top;
 215
 216   gdb_assert (gdbarch == get_frame_arch (frame));
 217
 218   /* Define I387_ST0_REGNUM such that we use the proper definitions
 219      for FRAME's architecture.  */
 220 #define I387_ST0_REGNUM tdep->st0_regnum
 221
 222   fctrl = get_frame_register_unsigned (frame, I387_FCTRL_REGNUM);
 223   fstat = get_frame_register_unsigned (frame, I387_FSTAT_REGNUM);
 224   ftag = get_frame_register_unsigned (frame, I387_FTAG_REGNUM);
 225   fiseg = get_frame_register_unsigned (frame, I387_FISEG_REGNUM);
 226   fioff = get_frame_register_unsigned (frame, I387_FIOFF_REGNUM);
 227   foseg = get_frame_register_unsigned (frame, I387_FOSEG_REGNUM);
 228   fooff = get_frame_register_unsigned (frame, I387_FOOFF_REGNUM);
 229   fop = get_frame_register_unsigned (frame, I387_FOP_REGNUM);
 230
 231   top = ((fstat >> 11) & 7);
 232
 233   for (fpreg = 7; fpreg >= 0; fpreg--)
 234     {
 235       gdb_byte raw[I386_MAX_REGISTER_SIZE];
 236       int tag = (ftag >> (fpreg * 2)) & 3;
 237       int i;
 238
 239       fprintf_filtered (file, "%sR%d: ", fpreg == top ? "=>" : "  ", fpreg);
 240
 241       switch (tag)
 242         {
 243         case 0:
 244           fputs_filtered ("Valid   ", file);
 245           break;
 246         case 1:
 247           fputs_filtered ("Zero    ", file);
 248           break;
 249         case 2:
 250           fputs_filtered ("Special ", file);
 251           break;
 252         case 3:
 253           fputs_filtered ("Empty   ", file);
 254           break;
 255         }
 256
 257       get_frame_register (frame, (fpreg + 8 - top) % 8 + I387_ST0_REGNUM, raw);
 258
 259       fputs_filtered ("0x", file);
 260       for (i = 9; i >= 0; i--)
 261         fprintf_filtered (file, "%02x", raw[i]);
 262
 263       if (tag != 3)
 264         print_i387_ext (raw, file);
 265
 266       fputs_filtered ("\n", file);
 267     }
 268
 269   fputs_filtered ("\n", file);
 270
 271   print_i387_status_word (fstat, file);
 272   print_i387_control_word (fctrl, file);
 273   fprintf_filtered (file, "Tag Word:            %s\n",
 274                     hex_string_custom (ftag, 4));
 275   fprintf_filtered (file, "Instruction Pointer: %s:",
 276                     hex_string_custom (fiseg, 2));
 277   fprintf_filtered (file, "%s\n", hex_string_custom (fioff, 8));
 278   fprintf_filtered (file, "Operand Pointer:     %s:",
 279                     hex_string_custom (foseg, 2));
 280   fprintf_filtered (file, "%s\n", hex_string_custom (fooff, 8));
 281   fprintf_filtered (file, "Opcode:              %s\n",
 282                     hex_string_custom (fop ? (fop | 0xd800) : 0, 4));
 283
 284 #undef I387_ST0_REGNUM
 285 }
 286 \f
 287
 288 /* Return nonzero if a value of type TYPE stored in register REGNUM
 289    needs any special handling.  */
 290
 291 int
 292 i387_convert_register_p (int regnum, struct type *type)
 293 {
 294   if (i386_fp_regnum_p (regnum))
 295     {
 296       /* Floating point registers must be converted unless we are
 297          accessing them in their hardware type.  */
 298       if (type == builtin_type_i387_ext)
 299         return 0;
 300       else
 301         return 1;
 302     }
 303
 304   return 0;
 305 }
 306
 307 /* Read a value of type TYPE from register REGNUM in frame FRAME, and
 308    return its contents in TO.  */
 309
 310 void
 311 i387_register_to_value (struct frame_info *frame, int regnum,
 312                         struct type *type, gdb_byte *to)
 313 {
 314   gdb_byte from[I386_MAX_REGISTER_SIZE];
 315
 316   gdb_assert (i386_fp_regnum_p (regnum));
 317
 318   /* We only support floating-point values.  */
 319   if (TYPE_CODE (type) != TYPE_CODE_FLT)
 320     {
 321       warning (_("Cannot convert floating-point register value "
 322                "to non-floating-point type."));
 323       return;
 324     }
 325
 326   /* Convert to TYPE.  */
 327   get_frame_register (frame, regnum, from);
 328   convert_typed_floating (from, builtin_type_i387_ext, to, type);
 329 }
 330
 331 /* Write the contents FROM of a value of type TYPE into register
 332    REGNUM in frame FRAME.  */
 333
 334 void
 335 i387_value_to_register (struct frame_info *frame, int regnum,
 336                         struct type *type, const gdb_byte *from)
 337 {
 338   gdb_byte to[I386_MAX_REGISTER_SIZE];
 339
 340   gdb_assert (i386_fp_regnum_p (regnum));
 341
 342   /* We only support floating-point values.  */
 343   if (TYPE_CODE (type) != TYPE_CODE_FLT)
 344     {
 345       warning (_("Cannot convert non-floating-point type "
 346                "to floating-point register value."));
 347       return;
 348     }
 349
 350   /* Convert from TYPE.  */
 351   convert_typed_floating (from, type, to, builtin_type_i387_ext);
 352   put_frame_register (frame, regnum, to);
 353 }
 354 \f
 355
 356 /* Handle FSAVE and FXSAVE formats.  */
 357
 358 /* At fsave_offset[REGNUM] you'll find the offset to the location in
 359    the data structure used by the "fsave" instruction where GDB
 360    register REGNUM is stored.  */
 361
 362 static int fsave_offset[] =
 363 {
 364   28 + 0 * 10,                  /* %st(0) ...  */
 365   28 + 1 * 10,
 366   28 + 2 * 10,
 367   28 + 3 * 10,
 368   28 + 4 * 10,
 369   28 + 5 * 10,
 370   28 + 6 * 10,
 371   28 + 7 * 10,                  /* ... %st(7).  */
 372   0,                            /* `fctrl' (16 bits).  */
 373   4,                            /* `fstat' (16 bits).  */
 374   8,                            /* `ftag' (16 bits).  */
 375   16,                           /* `fiseg' (16 bits).  */
 376   12,                           /* `fioff'.  */
 377   24,                           /* `foseg' (16 bits).  */
 378   20,                           /* `fooff'.  */
 379   18                            /* `fop' (bottom 11 bits).  */
 380 };
 381
 382 #define FSAVE_ADDR(fsave, regnum) \
 383   (fsave + fsave_offset[regnum - I387_ST0_REGNUM])
 384 \f
 385
 386 /* Fill register REGNUM in REGCACHE with the appropriate value from
 387    *FSAVE.  This function masks off any of the reserved bits in
 388    *FSAVE.  */
 389
 390 void
 391 i387_supply_fsave (struct regcache *regcache, int regnum, const void *fsave)
 392 {
 393   struct gdbarch_tdep *tdep = gdbarch_tdep (get_regcache_arch (regcache));
 394   const gdb_byte *regs = fsave;
 395   int i;
 396
 397   gdb_assert (tdep->st0_regnum >= I386_ST0_REGNUM);
 398
 399   /* Define I387_ST0_REGNUM and I387_NUM_XMM_REGS such that we use the
 400      proper definitions for REGCACHE's architecture.  */
 401
 402 #define I387_ST0_REGNUM tdep->st0_regnum
 403 #define I387_NUM_XMM_REGS tdep->num_xmm_regs
 404
 405   for (i = I387_ST0_REGNUM; i < I387_XMM0_REGNUM; i++)
 406     if (regnum == -1 || regnum == i)
 407       {
 408         if (fsave == NULL)
 409           {
 410             regcache_raw_supply (regcache, i, NULL);
 411             continue;
 412           }
 413
 414         /* Most of the FPU control registers occupy only 16 bits in the
 415            fsave area.  Give those a special treatment.  */
 416         if (i >= I387_FCTRL_REGNUM
 417             && i != I387_FIOFF_REGNUM && i != I387_FOOFF_REGNUM)
 418           {
 419             gdb_byte val[4];
 420
 421             memcpy (val, FSAVE_ADDR (regs, i), 2);
 422             val[2] = val[3] = 0;
 423             if (i == I387_FOP_REGNUM)
 424               val[1] &= ((1 << 3) - 1);
 425             regcache_raw_supply (regcache, i, val);
 426           }
 427         else
 428           regcache_raw_supply (regcache, i, FSAVE_ADDR (regs, i));
 429       }
 430
 431   /* Provide dummy values for the SSE registers.  */
 432   for (i = I387_XMM0_REGNUM; i < I387_MXCSR_REGNUM; i++)
 433     if (regnum == -1 || regnum == i)
 434       regcache_raw_supply (regcache, i, NULL);
 435   if (regnum == -1 || regnum == I387_MXCSR_REGNUM)
 436     {
 437       gdb_byte buf[4];
 438
 439       store_unsigned_integer (buf, 4, 0x1f80);
 440       regcache_raw_supply (regcache, I387_MXCSR_REGNUM, buf);
 441     }
 442
 443 #undef I387_ST0_REGNUM
 444 #undef I387_NUM_XMM_REGS
 445 }
 446
 447 /* Fill register REGNUM (if it is a floating-point register) in *FSAVE
 448    with the value from REGCACHE.  If REGNUM is -1, do this for all
 449    registers.  This function doesn't touch any of the reserved bits in
 450    *FSAVE.  */
 451
 452 void
 453 i387_collect_fsave (const struct regcache *regcache, int regnum, void *fsave)
 454 {
 455   struct gdbarch_tdep *tdep = gdbarch_tdep (get_regcache_arch (regcache));
 456   gdb_byte *regs = fsave;
 457   int i;
 458
 459   gdb_assert (tdep->st0_regnum >= I386_ST0_REGNUM);
 460
 461   /* Define I387_ST0_REGNUM such that we use the proper definitions
 462      for REGCACHE's architecture.  */
 463 #define I387_ST0_REGNUM tdep->st0_regnum
 464
 465   for (i = I387_ST0_REGNUM; i < I387_XMM0_REGNUM; i++)
 466     if (regnum == -1 || regnum == i)
 467       {
 468         /* Most of the FPU control registers occupy only 16 bits in
 469            the fsave area.  Give those a special treatment.  */
 470         if (i >= I387_FCTRL_REGNUM
 471             && i != I387_FIOFF_REGNUM && i != I387_FOOFF_REGNUM)
 472           {
 473             gdb_byte buf[4];
 474
 475             regcache_raw_collect (regcache, i, buf);
 476
 477             if (i == I387_FOP_REGNUM)
 478               {
 479                 /* The opcode occupies only 11 bits.  Make sure we
 480                    don't touch the other bits.  */
 481                 buf[1] &= ((1 << 3) - 1);
 482                 buf[1] |= ((FSAVE_ADDR (regs, i))[1] & ~((1 << 3) - 1));
 483               }
 484             memcpy (FSAVE_ADDR (regs, i), buf, 2);
 485           }
 486         else
 487           regcache_raw_collect (regcache, i, FSAVE_ADDR (regs, i));
 488       }
 489 #undef I387_ST0_REGNUM
 490 }
 491 \f
 492
 493 /* At fxsave_offset[REGNUM] you'll find the offset to the location in
 494    the data structure used by the "fxsave" instruction where GDB
 495    register REGNUM is stored.  */
 496
 497 static int fxsave_offset[] =
 498 {
 499   32,                           /* %st(0) through ...  */
 500   48,
 501   64,
 502   80,
 503   96,
 504   112,
 505   128,
 506   144,                          /* ... %st(7) (80 bits each).  */
 507   0,                            /* `fctrl' (16 bits).  */
 508   2,                            /* `fstat' (16 bits).  */
 509   4,                            /* `ftag' (16 bits).  */
 510   12,                           /* `fiseg' (16 bits).  */
 511   8,                            /* `fioff'.  */
 512   20,                           /* `foseg' (16 bits).  */
 513   16,                           /* `fooff'.  */
 514   6,                            /* `fop' (bottom 11 bits).  */
 515   160 + 0 * 16,                 /* %xmm0 through ...  */
 516   160 + 1 * 16,
 517   160 + 2 * 16,
 518   160 + 3 * 16,
 519   160 + 4 * 16,
 520   160 + 5 * 16,
 521   160 + 6 * 16,
 522   160 + 7 * 16,
 523   160 + 8 * 16,
 524   160 + 9 * 16,
 525   160 + 10 * 16,
 526   160 + 11 * 16,
 527   160 + 12 * 16,
 528   160 + 13 * 16,
 529   160 + 14 * 16,
 530   160 + 15 * 16,                /* ... %xmm15 (128 bits each).  */
 531 };
 532
 533 #define FXSAVE_ADDR(fxsave, regnum) \
 534   (fxsave + fxsave_offset[regnum - I387_ST0_REGNUM])
 535
 536 /* We made an unfortunate choice in putting %mxcsr after the SSE
 537    registers %xmm0-%xmm7 instead of before, since it makes supporting
 538    the registers %xmm8-%xmm15 on AMD64 a bit involved.  Therefore we
 539    don't include the offset for %mxcsr here above.  */
 540
 541 #define FXSAVE_MXCSR_ADDR(fxsave) (fxsave + 24)
 542
 543 static int i387_tag (const gdb_byte *raw);
 544 \f
 545
 546 /* Fill register REGNUM in REGCACHE with the appropriate
 547    floating-point or SSE register value from *FXSAVE.  This function
 548    masks off any of the reserved bits in *FXSAVE.  */
 549
 550 void
 551 i387_supply_fxsave (struct regcache *regcache, int regnum, const void *fxsave)
 552 {
 553   struct gdbarch_tdep *tdep = gdbarch_tdep (get_regcache_arch (regcache));
 554   const gdb_byte *regs = fxsave;
 555   int i;
 556
 557   gdb_assert (tdep->st0_regnum >= I386_ST0_REGNUM);
 558   gdb_assert (tdep->num_xmm_regs > 0);
 559
 560   /* Define I387_ST0_REGNUM and I387_NUM_XMM_REGS such that we use the
 561      proper definitions for REGCACHE's architecture.  */
 562
 563 #define I387_ST0_REGNUM tdep->st0_regnum
 564 #define I387_NUM_XMM_REGS tdep->num_xmm_regs
 565
 566   for (i = I387_ST0_REGNUM; i < I387_MXCSR_REGNUM; i++)
 567     if (regnum == -1 || regnum == i)
 568       {
 569         if (regs == NULL)
 570           {
 571             regcache_raw_supply (regcache, i, NULL);
 572             continue;
 573           }
 574
 575         /* Most of the FPU control registers occupy only 16 bits in
 576            the fxsave area.  Give those a special treatment.  */
 577         if (i >= I387_FCTRL_REGNUM && i < I387_XMM0_REGNUM
 578             && i != I387_FIOFF_REGNUM && i != I387_FOOFF_REGNUM)
 579           {
 580             gdb_byte val[4];
 581
 582             memcpy (val, FXSAVE_ADDR (regs, i), 2);
 583             val[2] = val[3] = 0;
 584             if (i == I387_FOP_REGNUM)
 585               val[1] &= ((1 << 3) - 1);
 586             else if (i== I387_FTAG_REGNUM)
 587               {
 588                 /* The fxsave area contains a simplified version of
 589                    the tag word.  We have to look at the actual 80-bit
 590                    FP data to recreate the traditional i387 tag word.  */
 591
 592                 unsigned long ftag = 0;
 593                 int fpreg;
 594                 int top;
 595
 596                 top = ((FXSAVE_ADDR (regs, I387_FSTAT_REGNUM))[1] >> 3);
 597                 top &= 0x7;
 598
 599                 for (fpreg = 7; fpreg >= 0; fpreg--)
 600                   {
 601                     int tag;
 602
 603                     if (val[0] & (1 << fpreg))
 604                       {
 605                         int regnum = (fpreg + 8 - top) % 8 + I387_ST0_REGNUM;
 606                         tag = i387_tag (FXSAVE_ADDR (regs, regnum));
 607                       }
 608                     else
 609                       tag = 3;          /* Empty */
 610
 611                     ftag |= tag << (2 * fpreg);
 612                   }
 613                 val[0] = ftag & 0xff;
 614                 val[1] = (ftag >> 8) & 0xff;
 615               }
 616             regcache_raw_supply (regcache, i, val);
 617           }
 618         else
 619           regcache_raw_supply (regcache, i, FXSAVE_ADDR (regs, i));
 620       }
 621
 622   if (regnum == I387_MXCSR_REGNUM || regnum == -1)
 623     {
 624       if (regs == NULL)
 625         regcache_raw_supply (regcache, I387_MXCSR_REGNUM, NULL);
 626       else
 627         regcache_raw_supply (regcache, I387_MXCSR_REGNUM,
 628                              FXSAVE_MXCSR_ADDR (regs));
 629     }
 630
 631 #undef I387_ST0_REGNUM
 632 #undef I387_NUM_XMM_REGS
 633 }
 634
 635 /* Fill register REGNUM (if it is a floating-point or SSE register) in
 636    *FXSAVE with the value from REGCACHE.  If REGNUM is -1, do this for
 637    all registers.  This function doesn't touch any of the reserved
 638    bits in *FXSAVE.  */
 639
 640 void
 641 i387_collect_fxsave (const struct regcache *regcache, int regnum, void *fxsave)
 642 {
 643   struct gdbarch_tdep *tdep = gdbarch_tdep (get_regcache_arch (regcache));
 644   gdb_byte *regs = fxsave;
 645   int i;
 646
 647   gdb_assert (tdep->st0_regnum >= I386_ST0_REGNUM);
 648   gdb_assert (tdep->num_xmm_regs > 0);
 649
 650   /* Define I387_ST0_REGNUM and I387_NUM_XMM_REGS such that we use the
 651      proper definitions for REGCACHE's architecture.  */
 652
 653 #define I387_ST0_REGNUM tdep->st0_regnum
 654 #define I387_NUM_XMM_REGS tdep->num_xmm_regs
 655
 656   for (i = I387_ST0_REGNUM; i < I387_MXCSR_REGNUM; i++)
 657     if (regnum == -1 || regnum == i)
 658       {
 659         /* Most of the FPU control registers occupy only 16 bits in
 660            the fxsave area.  Give those a special treatment.  */
 661         if (i >= I387_FCTRL_REGNUM && i < I387_XMM0_REGNUM
 662             && i != I387_FIOFF_REGNUM && i != I387_FOOFF_REGNUM)
 663           {
 664             gdb_byte buf[4];
 665
 666             regcache_raw_collect (regcache, i, buf);
 667
 668             if (i == I387_FOP_REGNUM)
 669               {
 670                 /* The opcode occupies only 11 bits.  Make sure we
 671                    don't touch the other bits.  */
 672                 buf[1] &= ((1 << 3) - 1);
 673                 buf[1] |= ((FXSAVE_ADDR (regs, i))[1] & ~((1 << 3) - 1));
 674               }
 675             else if (i == I387_FTAG_REGNUM)
 676               {
 677                 /* Converting back is much easier.  */
 678
 679                 unsigned short ftag;
 680                 int fpreg;
 681
 682                 ftag = (buf[1] << 8) | buf[0];
 683                 buf[0] = 0;
 684                 buf[1] = 0;
 685
 686                 for (fpreg = 7; fpreg >= 0; fpreg--)
 687                   {
 688                     int tag = (ftag >> (fpreg * 2)) & 3;
 689
 690                     if (tag != 3)
 691                       buf[0] |= (1 << fpreg);
 692                   }
 693               }
 694             memcpy (FXSAVE_ADDR (regs, i), buf, 2);
 695           }
 696         else
 697           regcache_raw_collect (regcache, i, FXSAVE_ADDR (regs, i));
 698       }
 699
 700   if (regnum == I387_MXCSR_REGNUM || regnum == -1)
 701     regcache_raw_collect (regcache, I387_MXCSR_REGNUM,
 702                           FXSAVE_MXCSR_ADDR (regs));
 703
 704 #undef I387_ST0_REGNUM
 705 #undef I387_NUM_XMM_REGS
 706 }
 707
 708 /* Recreate the FTW (tag word) valid bits from the 80-bit FP data in
 709    *RAW.  */
 710
 711 static int
 712 i387_tag (const gdb_byte *raw)
 713 {
 714   int integer;
 715   unsigned int exponent;
 716   unsigned long fraction[2];
 717
 718   integer = raw[7] & 0x80;
 719   exponent = (((raw[9] & 0x7f) << 8) | raw[8]);
 720   fraction[0] = ((raw[3] << 24) | (raw[2] << 16) | (raw[1] << 8) | raw[0]);
 721   fraction[1] = (((raw[7] & 0x7f) << 24) | (raw[6] << 16)
 722                  | (raw[5] << 8) | raw[4]);
 723
 724   if (exponent == 0x7fff)
 725     {
 726       /* Special.  */
 727       return (2);
 728     }
 729   else if (exponent == 0x0000)
 730     {
 731       if (fraction[0] == 0x0000 && fraction[1] == 0x0000 && !integer)
 732         {
 733           /* Zero.  */
 734           return (1);
 735         }
 736       else
 737         {
 738           /* Special.  */
 739           return (2);
 740         }
 741     }
 742   else
 743     {
 744       if (integer)
 745         {
 746           /* Valid.  */
 747           return (0);
 748         }
 749       else
 750         {
 751           /* Special.  */
 752           return (2);
 753         }
 754     }
 755 }
 756
 757 /* Prepare the FPU stack in REGCACHE for a function return.  */
 758
 759 void
 760 i387_return_value (struct gdbarch *gdbarch, struct regcache *regcache)
 761 {
 762   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 763   ULONGEST fstat;
 764
 765   /* Define I387_ST0_REGNUM such that we use the proper
 766      definitions for the architecture.  */
 767 #define I387_ST0_REGNUM tdep->st0_regnum
 768
 769   /* Set the top of the floating-point register stack to 7.  The
 770      actual value doesn't really matter, but 7 is what a normal
 771      function return would end up with if the program started out with
 772      a freshly initialized FPU.  */
 773   regcache_raw_read_unsigned (regcache, I387_FSTAT_REGNUM, &fstat);
 774   fstat |= (7 << 11);
 775   regcache_raw_write_unsigned (regcache, I387_FSTAT_REGNUM, fstat);
 776
 777   /* Mark %st(1) through %st(7) as empty.  Since we set the top of the
 778      floating-point register stack to 7, the appropriate value for the
 779      tag word is 0x3fff.  */
 780   regcache_raw_write_unsigned (regcache, I387_FTAG_REGNUM, 0x3fff);
 781
 782 #undef I387_ST0_REGNUM
 783 }