arch/i386/math-emu/errors.c

   1 /*---------------------------------------------------------------------------+
   2  |  errors.c                                                                 |
   3  |                                                                           |
   4  |  The error handling functions for wm-FPU-emu                              |
   5  |                                                                           |
   6  | Copyright (C) 1992,1993,1994,1996                                         |
   7  |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
   8  |                  E-mail   billm@jacobi.maths.monash.edu.au                |
   9  |                                                                           |
  10  |                                                                           |
  11  +---------------------------------------------------------------------------*/
  12
  13 /*---------------------------------------------------------------------------+
  14  | Note:                                                                     |
  15  |    The file contains code which accesses user memory.                     |
  16  |    Emulator static data may change when user memory is accessed, due to   |
  17  |    other processes using the emulator while swapping is in progress.      |
  18  +---------------------------------------------------------------------------*/
  19
  20 #include <linux/signal.h>
  21
  22 #include <asm/uaccess.h>
  23
  24 #include "fpu_emu.h"
  25 #include "fpu_system.h"
  26 #include "exception.h"
  27 #include "status_w.h"
  28 #include "control_w.h"
  29 #include "reg_constant.h"
  30 #include "version.h"
  31
  32 /* */
  33 #undef PRINT_MESSAGES
  34 /* */
  35
  36
  37 void Un_impl(void)
  38 {
  39   u_char byte1, FPU_modrm;
  40   unsigned long address = FPU_ORIG_EIP;
  41
  42   RE_ENTRANT_CHECK_OFF;
  43   /* No need to verify_area(), we have previously fetched these bytes. */
  44   printk("Unimplemented FPU Opcode at eip=%p : ", (void *) address);
  45   if ( FPU_CS == __USER_CS )
  46     {
  47       while ( 1 )
  48         {
  49           FPU_get_user(byte1, (u_char *) address);
  50           if ( (byte1 & 0xf8) == 0xd8 ) break;
  51           printk("[%02x]", byte1);
  52           address++;
  53         }
  54       printk("%02x ", byte1);
  55       FPU_get_user(FPU_modrm, 1 + (u_char *) address);
  56
  57       if (FPU_modrm >= 0300)
  58         printk("%02x (%02x+%d)\n", FPU_modrm, FPU_modrm & 0xf8, FPU_modrm & 7);
  59       else
  60         printk("/%d\n", (FPU_modrm >> 3) & 7);
  61     }
  62   else
  63     {
  64       printk("cs selector = %04x\n", FPU_CS);
  65     }
  66
  67   RE_ENTRANT_CHECK_ON;
  68
  69   EXCEPTION(EX_Invalid);
  70
  71 }
  72
  73
  74 /*
  75    Called for opcodes which are illegal and which are known to result in a
  76    SIGILL with a real 80486.
  77    */
  78 void FPU_illegal(void)
  79 {
  80   math_abort(FPU_info,SIGILL);
  81 }
  82
  83
  84
  85 void FPU_printall(void)
  86 {
  87   int i;
  88   static const char *tag_desc[] = { "Valid", "Zero", "ERROR", "Empty",
  89                               "DeNorm", "Inf", "NaN" };
  90   u_char byte1, FPU_modrm;
  91   unsigned long address = FPU_ORIG_EIP;
  92
  93   RE_ENTRANT_CHECK_OFF;
  94   /* No need to verify_area(), we have previously fetched these bytes. */
  95   printk("At %p:", (void *) address);
  96   if ( FPU_CS == __USER_CS )
  97     {
  98 #define MAX_PRINTED_BYTES 20
  99       for ( i = 0; i < MAX_PRINTED_BYTES; i++ )
 100         {
 101           FPU_get_user(byte1, (u_char *) address);
 102           if ( (byte1 & 0xf8) == 0xd8 )
 103             {
 104               printk(" %02x", byte1);
 105               break;
 106             }
 107           printk(" [%02x]", byte1);
 108           address++;
 109         }
 110       if ( i == MAX_PRINTED_BYTES )
 111         printk(" [more..]\n");
 112       else
 113         {
 114           FPU_get_user(FPU_modrm, 1 + (u_char *) address);
 115
 116           if (FPU_modrm >= 0300)
 117             printk(" %02x (%02x+%d)\n", FPU_modrm, FPU_modrm & 0xf8, FPU_modrm & 7);
 118           else
 119             printk(" /%d, mod=%d rm=%d\n",
 120                    (FPU_modrm >> 3) & 7, (FPU_modrm >> 6) & 3, FPU_modrm & 7);
 121         }
 122     }
 123   else
 124     {
 125       printk("%04x\n", FPU_CS);
 126     }
 127
 128   partial_status = status_word();
 129
 130 #ifdef DEBUGGING
 131 if ( partial_status & SW_Backward )    printk("SW: backward compatibility\n");
 132 if ( partial_status & SW_C3 )          printk("SW: condition bit 3\n");
 133 if ( partial_status & SW_C2 )          printk("SW: condition bit 2\n");
 134 if ( partial_status & SW_C1 )          printk("SW: condition bit 1\n");
 135 if ( partial_status & SW_C0 )          printk("SW: condition bit 0\n");
 136 if ( partial_status & SW_Summary )     printk("SW: exception summary\n");
 137 if ( partial_status & SW_Stack_Fault ) printk("SW: stack fault\n");
 138 if ( partial_status & SW_Precision )   printk("SW: loss of precision\n");
 139 if ( partial_status & SW_Underflow )   printk("SW: underflow\n");
 140 if ( partial_status & SW_Overflow )    printk("SW: overflow\n");
 141 if ( partial_status & SW_Zero_Div )    printk("SW: divide by zero\n");
 142 if ( partial_status & SW_Denorm_Op )   printk("SW: denormalized operand\n");
 143 if ( partial_status & SW_Invalid )     printk("SW: invalid operation\n");
 144 #endif DEBUGGING
 145
 146   printk(" SW: b=%d st=%ld es=%d sf=%d cc=%d%d%d%d ef=%d%d%d%d%d%d\n",
 147          partial_status & 0x8000 ? 1 : 0,   /* busy */
 148          (partial_status & 0x3800) >> 11,   /* stack top pointer */
 149          partial_status & 0x80 ? 1 : 0,     /* Error summary status */
 150          partial_status & 0x40 ? 1 : 0,     /* Stack flag */
 151          partial_status & SW_C3?1:0, partial_status & SW_C2?1:0, /* cc */
 152          partial_status & SW_C1?1:0, partial_status & SW_C0?1:0, /* cc */
 153          partial_status & SW_Precision?1:0, partial_status & SW_Underflow?1:0,
 154          partial_status & SW_Overflow?1:0, partial_status & SW_Zero_Div?1:0,
 155          partial_status & SW_Denorm_Op?1:0, partial_status & SW_Invalid?1:0);
 156
 157 printk(" CW: ic=%d rc=%ld%ld pc=%ld%ld iem=%d     ef=%d%d%d%d%d%d\n",
 158          control_word & 0x1000 ? 1 : 0,
 159          (control_word & 0x800) >> 11, (control_word & 0x400) >> 10,
 160          (control_word & 0x200) >> 9, (control_word & 0x100) >> 8,
 161          control_word & 0x80 ? 1 : 0,
 162          control_word & SW_Precision?1:0, control_word & SW_Underflow?1:0,
 163          control_word & SW_Overflow?1:0, control_word & SW_Zero_Div?1:0,
 164          control_word & SW_Denorm_Op?1:0, control_word & SW_Invalid?1:0);
 165
 166   for ( i = 0; i < 8; i++ )
 167     {
 168       FPU_REG *r = &st(i);
 169       u_char tagi = FPU_gettagi(i);
 170       switch (tagi)
 171         {
 172         case TAG_Empty:
 173           continue;
 174           break;
 175         case TAG_Zero:
 176         case TAG_Special:
 177           tagi = FPU_Special(r);
 178         case TAG_Valid:
 179           printk("st(%d)  %c .%04lx %04lx %04lx %04lx e%+-6d ", i,
 180                  getsign(r) ? '-' : '+',
 181                  (long)(r->sigh >> 16),
 182                  (long)(r->sigh & 0xFFFF),
 183                  (long)(r->sigl >> 16),
 184                  (long)(r->sigl & 0xFFFF),
 185                  exponent(r) - EXP_BIAS + 1);
 186           break;
 187         default:
 188           printk("Whoops! Error in errors.c: tag%d is %d ", i, tagi);
 189           continue;
 190           break;
 191         }
 192       printk("%s\n", tag_desc[(int) (unsigned) tagi]);
 193     }
 194
 195   RE_ENTRANT_CHECK_ON;
 196
 197 }
 198
 199 static struct {
 200   int type;
 201   const char *name;
 202 } exception_names[] = {
 203   { EX_StackOver, "stack overflow" },
 204   { EX_StackUnder, "stack underflow" },
 205   { EX_Precision, "loss of precision" },
 206   { EX_Underflow, "underflow" },
 207   { EX_Overflow, "overflow" },
 208   { EX_ZeroDiv, "divide by zero" },
 209   { EX_Denormal, "denormalized operand" },
 210   { EX_Invalid, "invalid operation" },
 211   { EX_INTERNAL, "INTERNAL BUG in "FPU_VERSION },
 212   { 0, NULL }
 213 };
 214
 215 /*
 216  EX_INTERNAL is always given with a code which indicates where the
 217  error was detected.
 218
 219  Internal error types:
 220        0x14   in fpu_etc.c
 221        0x1nn  in a *.c file:
 222               0x101  in reg_add_sub.c
 223               0x102  in reg_mul.c
 224               0x104  in poly_atan.c
 225               0x105  in reg_mul.c
 226               0x107  in fpu_trig.c
 227               0x108  in reg_compare.c
 228               0x109  in reg_compare.c
 229               0x110  in reg_add_sub.c
 230               0x111  in fpe_entry.c
 231               0x112  in fpu_trig.c
 232               0x113  in errors.c
 233               0x115  in fpu_trig.c
 234               0x116  in fpu_trig.c
 235               0x117  in fpu_trig.c
 236               0x118  in fpu_trig.c
 237               0x119  in fpu_trig.c
 238               0x120  in poly_atan.c
 239               0x121  in reg_compare.c
 240               0x122  in reg_compare.c
 241               0x123  in reg_compare.c
 242               0x125  in fpu_trig.c
 243               0x126  in fpu_entry.c
 244               0x127  in poly_2xm1.c
 245               0x128  in fpu_entry.c
 246               0x129  in fpu_entry.c
 247               0x130  in get_address.c
 248               0x131  in get_address.c
 249               0x132  in get_address.c
 250               0x133  in get_address.c
 251               0x140  in load_store.c
 252               0x141  in load_store.c
 253               0x150  in poly_sin.c
 254               0x151  in poly_sin.c
 255               0x160  in reg_ld_str.c
 256               0x161  in reg_ld_str.c
 257               0x162  in reg_ld_str.c
 258               0x163  in reg_ld_str.c
 259               0x164  in reg_ld_str.c
 260               0x170  in fpu_tags.c
 261               0x171  in fpu_tags.c
 262               0x172  in fpu_tags.c
 263               0x180  in reg_convert.c
 264        0x2nn  in an *.S file:
 265               0x201  in reg_u_add.S
 266               0x202  in reg_u_div.S
 267               0x203  in reg_u_div.S
 268               0x204  in reg_u_div.S
 269               0x205  in reg_u_mul.S
 270               0x206  in reg_u_sub.S
 271               0x207  in wm_sqrt.S
 272               0x208  in reg_div.S
 273               0x209  in reg_u_sub.S
 274               0x210  in reg_u_sub.S
 275               0x211  in reg_u_sub.S
 276               0x212  in reg_u_sub.S
 277               0x213  in wm_sqrt.S
 278               0x214  in wm_sqrt.S
 279               0x215  in wm_sqrt.S
 280               0x220  in reg_norm.S
 281               0x221  in reg_norm.S
 282               0x230  in reg_round.S
 283               0x231  in reg_round.S
 284               0x232  in reg_round.S
 285               0x233  in reg_round.S
 286               0x234  in reg_round.S
 287               0x235  in reg_round.S
 288               0x236  in reg_round.S
 289               0x240  in div_Xsig.S
 290               0x241  in div_Xsig.S
 291               0x242  in div_Xsig.S
 292  */
 293
 294 void FPU_exception(int n)
 295 {
 296   int i, int_type;
 297
 298   int_type = 0;         /* Needed only to stop compiler warnings */
 299   if ( n & EX_INTERNAL )
 300     {
 301       int_type = n - EX_INTERNAL;
 302       n = EX_INTERNAL;
 303       /* Set lots of exception bits! */
 304       partial_status |= (SW_Exc_Mask | SW_Summary | SW_Backward);
 305     }
 306   else
 307     {
 308       /* Extract only the bits which we use to set the status word */
 309       n &= (SW_Exc_Mask);
 310       /* Set the corresponding exception bit */
 311       partial_status |= n;
 312       /* Set summary bits iff exception isn't masked */
 313       if ( partial_status & ~control_word & CW_Exceptions )
 314         partial_status |= (SW_Summary | SW_Backward);
 315       if ( n & (SW_Stack_Fault | EX_Precision) )
 316         {
 317           if ( !(n & SW_C1) )
 318             /* This bit distinguishes over- from underflow for a stack fault,
 319                and roundup from round-down for precision loss. */
 320             partial_status &= ~SW_C1;
 321         }
 322     }
 323
 324   RE_ENTRANT_CHECK_OFF;
 325   if ( (~control_word & n & CW_Exceptions) || (n == EX_INTERNAL) )
 326     {
 327 #ifdef PRINT_MESSAGES
 328       /* My message from the sponsor */
 329       printk(FPU_VERSION" "__DATE__" (C) W. Metzenthen.\n");
 330 #endif PRINT_MESSAGES
 331
 332       /* Get a name string for error reporting */
 333       for (i=0; exception_names[i].type; i++)
 334         if ( (exception_names[i].type & n) == exception_names[i].type )
 335           break;
 336
 337       if (exception_names[i].type)
 338         {
 339 #ifdef PRINT_MESSAGES
 340           printk("FP Exception: %s!\n", exception_names[i].name);
 341 #endif PRINT_MESSAGES
 342         }
 343       else
 344         printk("FPU emulator: Unknown Exception: 0x%04x!\n", n);
 345
 346       if ( n == EX_INTERNAL )
 347         {
 348           printk("FPU emulator: Internal error type 0x%04x\n", int_type);
 349           FPU_printall();
 350         }
 351 #ifdef PRINT_MESSAGES
 352       else
 353         FPU_printall();
 354 #endif PRINT_MESSAGES
 355
 356       /*
 357        * The 80486 generates an interrupt on the next non-control FPU
 358        * instruction. So we need some means of flagging it.
 359        * We use the ES (Error Summary) bit for this.
 360        */
 361     }
 362   RE_ENTRANT_CHECK_ON;
 363
 364 #ifdef __DEBUG__
 365   math_abort(FPU_info,SIGFPE);
 366 #endif __DEBUG__
 367
 368 }
 369
 370
 371 /* Real operation attempted on a NaN. */
 372 /* Returns < 0 if the exception is unmasked */
 373 int real_1op_NaN(FPU_REG *a)
 374 {
 375   int signalling, isNaN;
 376
 377   isNaN = (exponent(a) == EXP_OVER) && (a->sigh & 0x80000000);
 378
 379   /* The default result for the case of two "equal" NaNs (signs may
 380      differ) is chosen to reproduce 80486 behaviour */
 381   signalling = isNaN && !(a->sigh & 0x40000000);
 382
 383   if ( !signalling )
 384     {
 385       if ( !isNaN )  /* pseudo-NaN, or other unsupported? */
 386         {
 387           if ( control_word & CW_Invalid )
 388             {
 389               /* Masked response */
 390               reg_copy(&CONST_QNaN, a);
 391             }
 392           EXCEPTION(EX_Invalid);
 393           return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Special;
 394         }
 395       return TAG_Special;
 396     }
 397
 398   if ( control_word & CW_Invalid )
 399     {
 400       /* The masked response */
 401       if ( !(a->sigh & 0x80000000) )  /* pseudo-NaN ? */
 402         {
 403           reg_copy(&CONST_QNaN, a);
 404         }
 405       /* ensure a Quiet NaN */
 406       a->sigh |= 0x40000000;
 407     }
 408
 409   EXCEPTION(EX_Invalid);
 410
 411   return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Special;
 412 }
 413
 414
 415 /* Real operation attempted on two operands, one a NaN. */
 416 /* Returns < 0 if the exception is unmasked */
 417 int real_2op_NaN(FPU_REG const *b, u_char tagb,
 418                  int deststnr,
 419                  FPU_REG const *defaultNaN)
 420 {
 421   FPU_REG *dest = &st(deststnr);
 422   FPU_REG const *a = dest;
 423   u_char taga = FPU_gettagi(deststnr);
 424   FPU_REG const *x;
 425   int signalling, unsupported;
 426
 427   if ( taga == TAG_Special )
 428     taga = FPU_Special(a);
 429   if ( tagb == TAG_Special )
 430     tagb = FPU_Special(b);
 431
 432   /* TW_NaN is also used for unsupported data types. */
 433   unsupported = ((taga == TW_NaN)
 434                  && !((exponent(a) == EXP_OVER) && (a->sigh & 0x80000000)))
 435     || ((tagb == TW_NaN)
 436         && !((exponent(b) == EXP_OVER) && (b->sigh & 0x80000000)));
 437   if ( unsupported )
 438     {
 439       if ( control_word & CW_Invalid )
 440         {
 441           /* Masked response */
 442           FPU_copy_to_regi(&CONST_QNaN, TAG_Special, deststnr);
 443         }
 444       EXCEPTION(EX_Invalid);
 445       return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Special;
 446     }
 447
 448   if (taga == TW_NaN)
 449     {
 450       x = a;
 451       if (tagb == TW_NaN)
 452         {
 453           signalling = !(a->sigh & b->sigh & 0x40000000);
 454           if ( significand(b) > significand(a) )
 455             x = b;
 456           else if ( significand(b) == significand(a) )
 457             {
 458               /* The default result for the case of two "equal" NaNs (signs may
 459                  differ) is chosen to reproduce 80486 behaviour */
 460               x = defaultNaN;
 461             }
 462         }
 463       else
 464         {
 465           /* return the quiet version of the NaN in a */
 466           signalling = !(a->sigh & 0x40000000);
 467         }
 468     }
 469   else
 470 #ifdef PARANOID
 471     if (tagb == TW_NaN)
 472 #endif PARANOID
 473     {
 474       signalling = !(b->sigh & 0x40000000);
 475       x = b;
 476     }
 477 #ifdef PARANOID
 478   else
 479     {
 480       signalling = 0;
 481       EXCEPTION(EX_INTERNAL|0x113);
 482       x = &CONST_QNaN;
 483     }
 484 #endif PARANOID
 485
 486   if ( (!signalling) || (control_word & CW_Invalid) )
 487     {
 488       if ( ! x )
 489         x = b;
 490
 491       if ( !(x->sigh & 0x80000000) )  /* pseudo-NaN ? */
 492         x = &CONST_QNaN;
 493
 494       FPU_copy_to_regi(x, TAG_Special, deststnr);
 495
 496       if ( !signalling )
 497         return TAG_Special;
 498
 499       /* ensure a Quiet NaN */
 500       dest->sigh |= 0x40000000;
 501     }
 502
 503   EXCEPTION(EX_Invalid);
 504
 505   return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Special;
 506 }
 507
 508
 509 /* Invalid arith operation on Valid registers */
 510 /* Returns < 0 if the exception is unmasked */
 511 asmlinkage int arith_invalid(int deststnr)
 512 {
 513
 514   EXCEPTION(EX_Invalid);
 515
 516   if ( control_word & CW_Invalid )
 517     {
 518       /* The masked response */
 519       FPU_copy_to_regi(&CONST_QNaN, TAG_Special, deststnr);
 520     }
 521
 522   return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Valid;
 523
 524 }
 525
 526
 527 /* Divide a finite number by zero */
 528 asmlinkage int FPU_divide_by_zero(int deststnr, u_char sign)
 529 {
 530   FPU_REG *dest = &st(deststnr);
 531   int tag = TAG_Valid;
 532
 533   if ( control_word & CW_ZeroDiv )
 534     {
 535       /* The masked response */
 536       FPU_copy_to_regi(&CONST_INF, TAG_Special, deststnr);
 537       setsign(dest, sign);
 538       tag = TAG_Special;
 539     }
 540
 541   EXCEPTION(EX_ZeroDiv);
 542
 543   return (!(control_word & CW_ZeroDiv) ? FPU_Exception : 0) | tag;
 544
 545 }
 546
 547
 548 /* This may be called often, so keep it lean */
 549 int set_precision_flag(int flags)
 550 {
 551   if ( control_word & CW_Precision )
 552     {
 553       partial_status &= ~(SW_C1 & flags);
 554       partial_status |= flags;   /* The masked response */
 555       return 0;
 556     }
 557   else
 558     {
 559       EXCEPTION(flags);
 560       return 1;
 561     }
 562 }
 563
 564
 565 /* This may be called often, so keep it lean */
 566 asmlinkage void set_precision_flag_up(void)
 567 {
 568   if ( control_word & CW_Precision )
 569     partial_status |= (SW_Precision | SW_C1);   /* The masked response */
 570   else
 571     EXCEPTION(EX_Precision | SW_C1);
 572 }
 573
 574
 575 /* This may be called often, so keep it lean */
 576 asmlinkage void set_precision_flag_down(void)
 577 {
 578   if ( control_word & CW_Precision )
 579     {   /* The masked response */
 580       partial_status &= ~SW_C1;
 581       partial_status |= SW_Precision;
 582     }
 583   else
 584     EXCEPTION(EX_Precision);
 585 }
 586
 587
 588 asmlinkage int denormal_operand(void)
 589 {
 590   if ( control_word & CW_Denormal )
 591     {   /* The masked response */
 592       partial_status |= SW_Denorm_Op;
 593       return TAG_Special;
 594     }
 595   else
 596     {
 597       EXCEPTION(EX_Denormal);
 598       return TAG_Special | FPU_Exception;
 599     }
 600 }
 601
 602
 603 asmlinkage int arith_overflow(FPU_REG *dest)
 604 {
 605   int tag = TAG_Valid;
 606
 607   if ( control_word & CW_Overflow )
 608     {
 609       /* The masked response */
 610 /* ###### The response here depends upon the rounding mode */
 611       reg_copy(&CONST_INF, dest);
 612       tag = TAG_Special;
 613     }
 614   else
 615     {
 616       /* Subtract the magic number from the exponent */
 617       addexponent(dest, (-3 * (1 << 13)));
 618     }
 619
 620   EXCEPTION(EX_Overflow);
 621   if ( control_word & CW_Overflow )
 622     {
 623       /* The overflow exception is masked. */
 624       /* By definition, precision is lost.
 625          The roundup bit (C1) is also set because we have
 626          "rounded" upwards to Infinity. */
 627       EXCEPTION(EX_Precision | SW_C1);
 628       return tag;
 629     }
 630
 631   return tag;
 632
 633 }
 634
 635
 636 asmlinkage int arith_underflow(FPU_REG *dest)
 637 {
 638   int tag = TAG_Valid;
 639
 640   if ( control_word & CW_Underflow )
 641     {
 642       /* The masked response */
 643       if ( exponent16(dest) <= EXP_UNDER - 63 )
 644         {
 645           reg_copy(&CONST_Z, dest);
 646           partial_status &= ~SW_C1;       /* Round down. */
 647           tag = TAG_Zero;
 648         }
 649       else
 650         {
 651           stdexp(dest);
 652         }
 653     }
 654   else
 655     {
 656       /* Add the magic number to the exponent. */
 657       addexponent(dest, (3 * (1 << 13)) + EXTENDED_Ebias);
 658     }
 659
 660   EXCEPTION(EX_Underflow);
 661   if ( control_word & CW_Underflow )
 662     {
 663       /* The underflow exception is masked. */
 664       EXCEPTION(EX_Precision);
 665       return tag;
 666     }
 667
 668   return tag;
 669
 670 }
 671
 672
 673 void FPU_stack_overflow(void)
 674 {
 675
 676  if ( control_word & CW_Invalid )
 677     {
 678       /* The masked response */
 679       top--;
 680       FPU_copy_to_reg0(&CONST_QNaN, TAG_Special);
 681     }
 682
 683   EXCEPTION(EX_StackOver);
 684
 685   return;
 686
 687 }
 688
 689
 690 void FPU_stack_underflow(void)
 691 {
 692
 693  if ( control_word & CW_Invalid )
 694     {
 695       /* The masked response */
 696       FPU_copy_to_reg0(&CONST_QNaN, TAG_Special);
 697     }
 698
 699   EXCEPTION(EX_StackUnder);
 700
 701   return;
 702
 703 }
 704
 705
 706 void FPU_stack_underflow_i(int i)
 707 {
 708
 709  if ( control_word & CW_Invalid )
 710     {
 711       /* The masked response */
 712       FPU_copy_to_regi(&CONST_QNaN, TAG_Special, i);
 713     }
 714
 715   EXCEPTION(EX_StackUnder);
 716
 717   return;
 718
 719 }
 720
 721
 722 void FPU_stack_underflow_pop(int i)
 723 {
 724
 725  if ( control_word & CW_Invalid )
 726     {
 727       /* The masked response */
 728       FPU_copy_to_regi(&CONST_QNaN, TAG_Special, i);
 729       FPU_pop();
 730     }
 731
 732   EXCEPTION(EX_StackUnder);
 733
 734   return;
 735
 736 }
 737