arch/x86/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 #if 0
  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 check access_ok(), we have previously fetched these bytes. */
  44         printk("Unimplemented FPU Opcode at eip=%p : ", (void __user *)address);
  45         if (FPU_CS == __USER_CS) {
  46                 while (1) {
  47                         FPU_get_user(byte1, (u_char __user *) address);
  48                         if ((byte1 & 0xf8) == 0xd8)
  49                                 break;
  50                         printk("[%02x]", byte1);
  51                         address++;
  52                 }
  53                 printk("%02x ", byte1);
  54                 FPU_get_user(FPU_modrm, 1 + (u_char __user *) address);
  55
  56                 if (FPU_modrm >= 0300)
  57                         printk("%02x (%02x+%d)\n", FPU_modrm, FPU_modrm & 0xf8,
  58                                FPU_modrm & 7);
  59                 else
  60                         printk("/%d\n", (FPU_modrm >> 3) & 7);
  61         } else {
  62                 printk("cs selector = %04x\n", FPU_CS);
  63         }
  64
  65         RE_ENTRANT_CHECK_ON;
  66
  67         EXCEPTION(EX_Invalid);
  68
  69 }
  70 #endif /*  0  */
  71
  72 /*
  73    Called for opcodes which are illegal and which are known to result in a
  74    SIGILL with a real 80486.
  75    */
  76 void FPU_illegal(void)
  77 {
  78         math_abort(FPU_info, SIGILL);
  79 }
  80
  81 void FPU_printall(void)
  82 {
  83         int i;
  84         static const char *tag_desc[] = { "Valid", "Zero", "ERROR", "Empty",
  85                 "DeNorm", "Inf", "NaN"
  86         };
  87         u_char byte1, FPU_modrm;
  88         unsigned long address = FPU_ORIG_EIP;
  89
  90         RE_ENTRANT_CHECK_OFF;
  91         /* No need to check access_ok(), we have previously fetched these bytes. */
  92         printk("At %p:", (void *)address);
  93         if (FPU_CS == __USER_CS) {
  94 #define MAX_PRINTED_BYTES 20
  95                 for (i = 0; i < MAX_PRINTED_BYTES; i++) {
  96                         FPU_get_user(byte1, (u_char __user *) address);
  97                         if ((byte1 & 0xf8) == 0xd8) {
  98                                 printk(" %02x", byte1);
  99                                 break;
 100                         }
 101                         printk(" [%02x]", byte1);
 102                         address++;
 103                 }
 104                 if (i == MAX_PRINTED_BYTES)
 105                         printk(" [more..]\n");
 106                 else {
 107                         FPU_get_user(FPU_modrm, 1 + (u_char __user *) address);
 108
 109                         if (FPU_modrm >= 0300)
 110                                 printk(" %02x (%02x+%d)\n", FPU_modrm,
 111                                        FPU_modrm & 0xf8, FPU_modrm & 7);
 112                         else
 113                                 printk(" /%d, mod=%d rm=%d\n",
 114                                        (FPU_modrm >> 3) & 7,
 115                                        (FPU_modrm >> 6) & 3, FPU_modrm & 7);
 116                 }
 117         } else {
 118                 printk("%04x\n", FPU_CS);
 119         }
 120
 121         partial_status = status_word();
 122
 123 #ifdef DEBUGGING
 124         if (partial_status & SW_Backward)
 125                 printk("SW: backward compatibility\n");
 126         if (partial_status & SW_C3)
 127                 printk("SW: condition bit 3\n");
 128         if (partial_status & SW_C2)
 129                 printk("SW: condition bit 2\n");
 130         if (partial_status & SW_C1)
 131                 printk("SW: condition bit 1\n");
 132         if (partial_status & SW_C0)
 133                 printk("SW: condition bit 0\n");
 134         if (partial_status & SW_Summary)
 135                 printk("SW: exception summary\n");
 136         if (partial_status & SW_Stack_Fault)
 137                 printk("SW: stack fault\n");
 138         if (partial_status & SW_Precision)
 139                 printk("SW: loss of precision\n");
 140         if (partial_status & SW_Underflow)
 141                 printk("SW: underflow\n");
 142         if (partial_status & SW_Overflow)
 143                 printk("SW: overflow\n");
 144         if (partial_status & SW_Zero_Div)
 145                 printk("SW: divide by zero\n");
 146         if (partial_status & SW_Denorm_Op)
 147                 printk("SW: denormalized operand\n");
 148         if (partial_status & SW_Invalid)
 149                 printk("SW: invalid operation\n");
 150 #endif /* DEBUGGING */
 151
 152         printk(" SW: b=%d st=%d es=%d sf=%d cc=%d%d%d%d ef=%d%d%d%d%d%d\n", partial_status & 0x8000 ? 1 : 0,    /* busy */
 153                (partial_status & 0x3800) >> 11, /* stack top pointer */
 154                partial_status & 0x80 ? 1 : 0,   /* Error summary status */
 155                partial_status & 0x40 ? 1 : 0,   /* Stack flag */
 156                partial_status & SW_C3 ? 1 : 0, partial_status & SW_C2 ? 1 : 0,  /* cc */
 157                partial_status & SW_C1 ? 1 : 0, partial_status & SW_C0 ? 1 : 0,  /* cc */
 158                partial_status & SW_Precision ? 1 : 0,
 159                partial_status & SW_Underflow ? 1 : 0,
 160                partial_status & SW_Overflow ? 1 : 0,
 161                partial_status & SW_Zero_Div ? 1 : 0,
 162                partial_status & SW_Denorm_Op ? 1 : 0,
 163                partial_status & SW_Invalid ? 1 : 0);
 164
 165         printk(" CW: ic=%d rc=%d%d pc=%d%d iem=%d     ef=%d%d%d%d%d%d\n",
 166                control_word & 0x1000 ? 1 : 0,
 167                (control_word & 0x800) >> 11, (control_word & 0x400) >> 10,
 168                (control_word & 0x200) >> 9, (control_word & 0x100) >> 8,
 169                control_word & 0x80 ? 1 : 0,
 170                control_word & SW_Precision ? 1 : 0,
 171                control_word & SW_Underflow ? 1 : 0,
 172                control_word & SW_Overflow ? 1 : 0,
 173                control_word & SW_Zero_Div ? 1 : 0,
 174                control_word & SW_Denorm_Op ? 1 : 0,
 175                control_word & SW_Invalid ? 1 : 0);
 176
 177         for (i = 0; i < 8; i++) {
 178                 FPU_REG *r = &st(i);
 179                 u_char tagi = FPU_gettagi(i);
 180                 switch (tagi) {
 181                 case TAG_Empty:
 182                         continue;
 183                         break;
 184                 case TAG_Zero:
 185                 case TAG_Special:
 186                         tagi = FPU_Special(r);
 187                 case TAG_Valid:
 188                         printk("st(%d)  %c .%04lx %04lx %04lx %04lx e%+-6d ", i,
 189                                getsign(r) ? '-' : '+',
 190                                (long)(r->sigh >> 16),
 191                                (long)(r->sigh & 0xFFFF),
 192                                (long)(r->sigl >> 16),
 193                                (long)(r->sigl & 0xFFFF),
 194                                exponent(r) - EXP_BIAS + 1);
 195                         break;
 196                 default:
 197                         printk("Whoops! Error in errors.c: tag%d is %d ", i,
 198                                tagi);
 199                         continue;
 200                         break;
 201                 }
 202                 printk("%s\n", tag_desc[(int)(unsigned)tagi]);
 203         }
 204
 205         RE_ENTRANT_CHECK_ON;
 206
 207 }
 208
 209 static struct {
 210         int type;
 211         const char *name;
 212 } exception_names[] = {
 213         {
 214         EX_StackOver, "stack overflow"}, {
 215         EX_StackUnder, "stack underflow"}, {
 216         EX_Precision, "loss of precision"}, {
 217         EX_Underflow, "underflow"}, {
 218         EX_Overflow, "overflow"}, {
 219         EX_ZeroDiv, "divide by zero"}, {
 220         EX_Denormal, "denormalized operand"}, {
 221         EX_Invalid, "invalid operation"}, {
 222         EX_INTERNAL, "INTERNAL BUG in " FPU_VERSION}, {
 223         0, NULL}
 224 };
 225
 226 /*
 227  EX_INTERNAL is always given with a code which indicates where the
 228  error was detected.
 229
 230  Internal error types:
 231        0x14   in fpu_etc.c
 232        0x1nn  in a *.c file:
 233               0x101  in reg_add_sub.c
 234               0x102  in reg_mul.c
 235               0x104  in poly_atan.c
 236               0x105  in reg_mul.c
 237               0x107  in fpu_trig.c
 238               0x108  in reg_compare.c
 239               0x109  in reg_compare.c
 240               0x110  in reg_add_sub.c
 241               0x111  in fpe_entry.c
 242               0x112  in fpu_trig.c
 243               0x113  in errors.c
 244               0x115  in fpu_trig.c
 245               0x116  in fpu_trig.c
 246               0x117  in fpu_trig.c
 247               0x118  in fpu_trig.c
 248               0x119  in fpu_trig.c
 249               0x120  in poly_atan.c
 250               0x121  in reg_compare.c
 251               0x122  in reg_compare.c
 252               0x123  in reg_compare.c
 253               0x125  in fpu_trig.c
 254               0x126  in fpu_entry.c
 255               0x127  in poly_2xm1.c
 256               0x128  in fpu_entry.c
 257               0x129  in fpu_entry.c
 258               0x130  in get_address.c
 259               0x131  in get_address.c
 260               0x132  in get_address.c
 261               0x133  in get_address.c
 262               0x140  in load_store.c
 263               0x141  in load_store.c
 264               0x150  in poly_sin.c
 265               0x151  in poly_sin.c
 266               0x160  in reg_ld_str.c
 267               0x161  in reg_ld_str.c
 268               0x162  in reg_ld_str.c
 269               0x163  in reg_ld_str.c
 270               0x164  in reg_ld_str.c
 271               0x170  in fpu_tags.c
 272               0x171  in fpu_tags.c
 273               0x172  in fpu_tags.c
 274               0x180  in reg_convert.c
 275        0x2nn  in an *.S file:
 276               0x201  in reg_u_add.S
 277               0x202  in reg_u_div.S
 278               0x203  in reg_u_div.S
 279               0x204  in reg_u_div.S
 280               0x205  in reg_u_mul.S
 281               0x206  in reg_u_sub.S
 282               0x207  in wm_sqrt.S
 283               0x208  in reg_div.S
 284               0x209  in reg_u_sub.S
 285               0x210  in reg_u_sub.S
 286               0x211  in reg_u_sub.S
 287               0x212  in reg_u_sub.S
 288               0x213  in wm_sqrt.S
 289               0x214  in wm_sqrt.S
 290               0x215  in wm_sqrt.S
 291               0x220  in reg_norm.S
 292               0x221  in reg_norm.S
 293               0x230  in reg_round.S
 294               0x231  in reg_round.S
 295               0x232  in reg_round.S
 296               0x233  in reg_round.S
 297               0x234  in reg_round.S
 298               0x235  in reg_round.S
 299               0x236  in reg_round.S
 300               0x240  in div_Xsig.S
 301               0x241  in div_Xsig.S
 302               0x242  in div_Xsig.S
 303  */
 304
 305 asmlinkage void FPU_exception(int n)
 306 {
 307         int i, int_type;
 308
 309         int_type = 0;           /* Needed only to stop compiler warnings */
 310         if (n & EX_INTERNAL) {
 311                 int_type = n - EX_INTERNAL;
 312                 n = EX_INTERNAL;
 313                 /* Set lots of exception bits! */
 314                 partial_status |= (SW_Exc_Mask | SW_Summary | SW_Backward);
 315         } else {
 316                 /* Extract only the bits which we use to set the status word */
 317                 n &= (SW_Exc_Mask);
 318                 /* Set the corresponding exception bit */
 319                 partial_status |= n;
 320                 /* Set summary bits iff exception isn't masked */
 321                 if (partial_status & ~control_word & CW_Exceptions)
 322                         partial_status |= (SW_Summary | SW_Backward);
 323                 if (n & (SW_Stack_Fault | EX_Precision)) {
 324                         if (!(n & SW_C1))
 325                                 /* This bit distinguishes over- from underflow for a stack fault,
 326                                    and roundup from round-down for precision loss. */
 327                                 partial_status &= ~SW_C1;
 328                 }
 329         }
 330
 331         RE_ENTRANT_CHECK_OFF;
 332         if ((~control_word & n & CW_Exceptions) || (n == EX_INTERNAL)) {
 333 #ifdef PRINT_MESSAGES
 334                 /* My message from the sponsor */
 335                 printk(FPU_VERSION " " __DATE__ " (C) W. Metzenthen.\n");
 336 #endif /* PRINT_MESSAGES */
 337
 338                 /* Get a name string for error reporting */
 339                 for (i = 0; exception_names[i].type; i++)
 340                         if ((exception_names[i].type & n) ==
 341                             exception_names[i].type)
 342                                 break;
 343
 344                 if (exception_names[i].type) {
 345 #ifdef PRINT_MESSAGES
 346                         printk("FP Exception: %s!\n", exception_names[i].name);
 347 #endif /* PRINT_MESSAGES */
 348                 } else
 349                         printk("FPU emulator: Unknown Exception: 0x%04x!\n", n);
 350
 351                 if (n == EX_INTERNAL) {
 352                         printk("FPU emulator: Internal error type 0x%04x\n",
 353                                int_type);
 354                         FPU_printall();
 355                 }
 356 #ifdef PRINT_MESSAGES
 357                 else
 358                         FPU_printall();
 359 #endif /* PRINT_MESSAGES */
 360
 361                 /*
 362                  * The 80486 generates an interrupt on the next non-control FPU
 363                  * instruction. So we need some means of flagging it.
 364                  * We use the ES (Error Summary) bit for this.
 365                  */
 366         }
 367         RE_ENTRANT_CHECK_ON;
 368
 369 #ifdef __DEBUG__
 370         math_abort(FPU_info, SIGFPE);
 371 #endif /* __DEBUG__ */
 372
 373 }
 374
 375 /* Real operation attempted on a NaN. */
 376 /* Returns < 0 if the exception is unmasked */
 377 int real_1op_NaN(FPU_REG *a)
 378 {
 379         int signalling, isNaN;
 380
 381         isNaN = (exponent(a) == EXP_OVER) && (a->sigh & 0x80000000);
 382
 383         /* The default result for the case of two "equal" NaNs (signs may
 384            differ) is chosen to reproduce 80486 behaviour */
 385         signalling = isNaN && !(a->sigh & 0x40000000);
 386
 387         if (!signalling) {
 388                 if (!isNaN) {   /* pseudo-NaN, or other unsupported? */
 389                         if (control_word & CW_Invalid) {
 390                                 /* Masked response */
 391                                 reg_copy(&CONST_QNaN, a);
 392                         }
 393                         EXCEPTION(EX_Invalid);
 394                         return (!(control_word & CW_Invalid) ? FPU_Exception :
 395                                 0) | TAG_Special;
 396                 }
 397                 return TAG_Special;
 398         }
 399
 400         if (control_word & CW_Invalid) {
 401                 /* The masked response */
 402                 if (!(a->sigh & 0x80000000)) {  /* pseudo-NaN ? */
 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 /* Real operation attempted on two operands, one a NaN. */
 415 /* Returns < 0 if the exception is unmasked */
 416 int real_2op_NaN(FPU_REG const *b, u_char tagb,
 417                  int deststnr, FPU_REG const *defaultNaN)
 418 {
 419         FPU_REG *dest = &st(deststnr);
 420         FPU_REG const *a = dest;
 421         u_char taga = FPU_gettagi(deststnr);
 422         FPU_REG const *x;
 423         int signalling, unsupported;
 424
 425         if (taga == TAG_Special)
 426                 taga = FPU_Special(a);
 427         if (tagb == TAG_Special)
 428                 tagb = FPU_Special(b);
 429
 430         /* TW_NaN is also used for unsupported data types. */
 431         unsupported = ((taga == TW_NaN)
 432                        && !((exponent(a) == EXP_OVER)
 433                             && (a->sigh & 0x80000000)))
 434             || ((tagb == TW_NaN)
 435                 && !((exponent(b) == EXP_OVER) && (b->sigh & 0x80000000)));
 436         if (unsupported) {
 437                 if (control_word & CW_Invalid) {
 438                         /* Masked response */
 439                         FPU_copy_to_regi(&CONST_QNaN, TAG_Special, deststnr);
 440                 }
 441                 EXCEPTION(EX_Invalid);
 442                 return (!(control_word & CW_Invalid) ? FPU_Exception : 0) |
 443                     TAG_Special;
 444         }
 445
 446         if (taga == TW_NaN) {
 447                 x = a;
 448                 if (tagb == TW_NaN) {
 449                         signalling = !(a->sigh & b->sigh & 0x40000000);
 450                         if (significand(b) > significand(a))
 451                                 x = b;
 452                         else if (significand(b) == significand(a)) {
 453                                 /* The default result for the case of two "equal" NaNs (signs may
 454                                    differ) is chosen to reproduce 80486 behaviour */
 455                                 x = defaultNaN;
 456                         }
 457                 } else {
 458                         /* return the quiet version of the NaN in a */
 459                         signalling = !(a->sigh & 0x40000000);
 460                 }
 461         } else
 462 #ifdef PARANOID
 463         if (tagb == TW_NaN)
 464 #endif /* PARANOID */
 465         {
 466                 signalling = !(b->sigh & 0x40000000);
 467                 x = b;
 468         }
 469 #ifdef PARANOID
 470         else {
 471                 signalling = 0;
 472                 EXCEPTION(EX_INTERNAL | 0x113);
 473                 x = &CONST_QNaN;
 474         }
 475 #endif /* PARANOID */
 476
 477         if ((!signalling) || (control_word & CW_Invalid)) {
 478                 if (!x)
 479                         x = b;
 480
 481                 if (!(x->sigh & 0x80000000))    /* pseudo-NaN ? */
 482                         x = &CONST_QNaN;
 483
 484                 FPU_copy_to_regi(x, TAG_Special, deststnr);
 485
 486                 if (!signalling)
 487                         return TAG_Special;
 488
 489                 /* ensure a Quiet NaN */
 490                 dest->sigh |= 0x40000000;
 491         }
 492
 493         EXCEPTION(EX_Invalid);
 494
 495         return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Special;
 496 }
 497
 498 /* Invalid arith operation on Valid registers */
 499 /* Returns < 0 if the exception is unmasked */
 500 asmlinkage int arith_invalid(int deststnr)
 501 {
 502
 503         EXCEPTION(EX_Invalid);
 504
 505         if (control_word & CW_Invalid) {
 506                 /* The masked response */
 507                 FPU_copy_to_regi(&CONST_QNaN, TAG_Special, deststnr);
 508         }
 509
 510         return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Valid;
 511
 512 }
 513
 514 /* Divide a finite number by zero */
 515 asmlinkage int FPU_divide_by_zero(int deststnr, u_char sign)
 516 {
 517         FPU_REG *dest = &st(deststnr);
 518         int tag = TAG_Valid;
 519
 520         if (control_word & CW_ZeroDiv) {
 521                 /* The masked response */
 522                 FPU_copy_to_regi(&CONST_INF, TAG_Special, deststnr);
 523                 setsign(dest, sign);
 524                 tag = TAG_Special;
 525         }
 526
 527         EXCEPTION(EX_ZeroDiv);
 528
 529         return (!(control_word & CW_ZeroDiv) ? FPU_Exception : 0) | tag;
 530
 531 }
 532
 533 /* This may be called often, so keep it lean */
 534 int set_precision_flag(int flags)
 535 {
 536         if (control_word & CW_Precision) {
 537                 partial_status &= ~(SW_C1 & flags);
 538                 partial_status |= flags;        /* The masked response */
 539                 return 0;
 540         } else {
 541                 EXCEPTION(flags);
 542                 return 1;
 543         }
 544 }
 545
 546 /* This may be called often, so keep it lean */
 547 asmlinkage void set_precision_flag_up(void)
 548 {
 549         if (control_word & CW_Precision)
 550                 partial_status |= (SW_Precision | SW_C1);       /* The masked response */
 551         else
 552                 EXCEPTION(EX_Precision | SW_C1);
 553 }
 554
 555 /* This may be called often, so keep it lean */
 556 asmlinkage void set_precision_flag_down(void)
 557 {
 558         if (control_word & CW_Precision) {      /* The masked response */
 559                 partial_status &= ~SW_C1;
 560                 partial_status |= SW_Precision;
 561         } else
 562                 EXCEPTION(EX_Precision);
 563 }
 564
 565 asmlinkage int denormal_operand(void)
 566 {
 567         if (control_word & CW_Denormal) {       /* The masked response */
 568                 partial_status |= SW_Denorm_Op;
 569                 return TAG_Special;
 570         } else {
 571                 EXCEPTION(EX_Denormal);
 572                 return TAG_Special | FPU_Exception;
 573         }
 574 }
 575
 576 asmlinkage int arith_overflow(FPU_REG *dest)
 577 {
 578         int tag = TAG_Valid;
 579
 580         if (control_word & CW_Overflow) {
 581                 /* The masked response */
 582 /* ###### The response here depends upon the rounding mode */
 583                 reg_copy(&CONST_INF, dest);
 584                 tag = TAG_Special;
 585         } else {
 586                 /* Subtract the magic number from the exponent */
 587                 addexponent(dest, (-3 * (1 << 13)));
 588         }
 589
 590         EXCEPTION(EX_Overflow);
 591         if (control_word & CW_Overflow) {
 592                 /* The overflow exception is masked. */
 593                 /* By definition, precision is lost.
 594                    The roundup bit (C1) is also set because we have
 595                    "rounded" upwards to Infinity. */
 596                 EXCEPTION(EX_Precision | SW_C1);
 597                 return tag;
 598         }
 599
 600         return tag;
 601
 602 }
 603
 604 asmlinkage int arith_underflow(FPU_REG *dest)
 605 {
 606         int tag = TAG_Valid;
 607
 608         if (control_word & CW_Underflow) {
 609                 /* The masked response */
 610                 if (exponent16(dest) <= EXP_UNDER - 63) {
 611                         reg_copy(&CONST_Z, dest);
 612                         partial_status &= ~SW_C1;       /* Round down. */
 613                         tag = TAG_Zero;
 614                 } else {
 615                         stdexp(dest);
 616                 }
 617         } else {
 618                 /* Add the magic number to the exponent. */
 619                 addexponent(dest, (3 * (1 << 13)) + EXTENDED_Ebias);
 620         }
 621
 622         EXCEPTION(EX_Underflow);
 623         if (control_word & CW_Underflow) {
 624                 /* The underflow exception is masked. */
 625                 EXCEPTION(EX_Precision);
 626                 return tag;
 627         }
 628
 629         return tag;
 630
 631 }
 632
 633 void FPU_stack_overflow(void)
 634 {
 635
 636         if (control_word & CW_Invalid) {
 637                 /* The masked response */
 638                 top--;
 639                 FPU_copy_to_reg0(&CONST_QNaN, TAG_Special);
 640         }
 641
 642         EXCEPTION(EX_StackOver);
 643
 644         return;
 645
 646 }
 647
 648 void FPU_stack_underflow(void)
 649 {
 650
 651         if (control_word & CW_Invalid) {
 652                 /* The masked response */
 653                 FPU_copy_to_reg0(&CONST_QNaN, TAG_Special);
 654         }
 655
 656         EXCEPTION(EX_StackUnder);
 657
 658         return;
 659
 660 }
 661
 662 void FPU_stack_underflow_i(int i)
 663 {
 664
 665         if (control_word & CW_Invalid) {
 666                 /* The masked response */
 667                 FPU_copy_to_regi(&CONST_QNaN, TAG_Special, i);
 668         }
 669
 670         EXCEPTION(EX_StackUnder);
 671
 672         return;
 673
 674 }
 675
 676 void FPU_stack_underflow_pop(int i)
 677 {
 678
 679         if (control_word & CW_Invalid) {
 680                 /* The masked response */
 681                 FPU_copy_to_regi(&CONST_QNaN, TAG_Special, i);
 682                 FPU_pop();
 683         }
 684
 685         EXCEPTION(EX_StackUnder);
 686
 687         return;
 688
 689 }