1 // SPDX-License-Identifier: GPL-2.0
2 /*---------------------------------------------------------------------------+
3  |  errors.c                                                                 |
4  |                                                                           |
5  |  The error handling functions for wm-FPU-emu                              |
6  |                                                                           |
7  | Copyright (C) 1992,1993,1994,1996                                         |
8  |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
9  |                  E-mail   billm@jacobi.maths.monash.edu.au                |
10  |                                                                           |
11  |                                                                           |
12  +---------------------------------------------------------------------------*/
13 
14 /*---------------------------------------------------------------------------+
15  | Note:                                                                     |
16  |    The file contains code which accesses user memory.                     |
17  |    Emulator static data may change when user memory is accessed, due to   |
18  |    other processes using the emulator while swapping is in progress.      |
19  +---------------------------------------------------------------------------*/
20 
21 #include <linux/signal.h>
22 
23 #include <linux/uaccess.h>
24 
25 #include "fpu_emu.h"
26 #include "fpu_system.h"
27 #include "exception.h"
28 #include "status_w.h"
29 #include "control_w.h"
30 #include "reg_constant.h"
31 #include "version.h"
32 
33 /* */
34 #undef PRINT_MESSAGES
35 /* */
36 
37 #if 0
38 void Un_impl(void)
39 {
40 	u_char byte1, FPU_modrm;
41 	unsigned long address = FPU_ORIG_EIP;
42 
43 	RE_ENTRANT_CHECK_OFF;
44 	/* No need to check access_ok(), we have previously fetched these bytes. */
45 	printk("Unimplemented FPU Opcode at eip=%p : ", (void __user *)address);
46 	if (FPU_CS == __USER_CS) {
47 		while (1) {
48 			FPU_get_user(byte1, (u_char __user *) address);
49 			if ((byte1 & 0xf8) == 0xd8)
50 				break;
51 			printk("[%02x]", byte1);
52 			address++;
53 		}
54 		printk("%02x ", byte1);
55 		FPU_get_user(FPU_modrm, 1 + (u_char __user *) address);
56 
57 		if (FPU_modrm >= 0300)
58 			printk("%02x (%02x+%d)\n", FPU_modrm, FPU_modrm & 0xf8,
59 			       FPU_modrm & 7);
60 		else
61 			printk("/%d\n", (FPU_modrm >> 3) & 7);
62 	} else {
63 		printk("cs selector = %04x\n", FPU_CS);
64 	}
65 
66 	RE_ENTRANT_CHECK_ON;
67 
68 	EXCEPTION(EX_Invalid);
69 
70 }
71 #endif /*  0  */
72 
73 /*
74    Called for opcodes which are illegal and which are known to result in a
75    SIGILL with a real 80486.
76    */
FPU_illegal(void)77 void FPU_illegal(void)
78 {
79 	math_abort(FPU_info, SIGILL);
80 }
81 
FPU_printall(void)82 void FPU_printall(void)
83 {
84 	int i;
85 	static const char *tag_desc[] = { "Valid", "Zero", "ERROR", "Empty",
86 		"DeNorm", "Inf", "NaN"
87 	};
88 	u_char byte1, FPU_modrm;
89 	unsigned long address = FPU_ORIG_EIP;
90 
91 	RE_ENTRANT_CHECK_OFF;
92 	/* No need to check access_ok(), we have previously fetched these bytes. */
93 	printk("At %p:", (void *)address);
94 	if (FPU_CS == __USER_CS) {
95 #define MAX_PRINTED_BYTES 20
96 		for (i = 0; i < MAX_PRINTED_BYTES; i++) {
97 			FPU_get_user(byte1, (u_char __user *) address);
98 			if ((byte1 & 0xf8) == 0xd8) {
99 				printk(" %02x", byte1);
100 				break;
101 			}
102 			printk(" [%02x]", byte1);
103 			address++;
104 		}
105 		if (i == MAX_PRINTED_BYTES)
106 			printk(" [more..]\n");
107 		else {
108 			FPU_get_user(FPU_modrm, 1 + (u_char __user *) address);
109 
110 			if (FPU_modrm >= 0300)
111 				printk(" %02x (%02x+%d)\n", FPU_modrm,
112 				       FPU_modrm & 0xf8, FPU_modrm & 7);
113 			else
114 				printk(" /%d, mod=%d rm=%d\n",
115 				       (FPU_modrm >> 3) & 7,
116 				       (FPU_modrm >> 6) & 3, FPU_modrm & 7);
117 		}
118 	} else {
119 		printk("%04x\n", FPU_CS);
120 	}
121 
122 	partial_status = status_word();
123 
124 #ifdef DEBUGGING
125 	if (partial_status & SW_Backward)
126 		printk("SW: backward compatibility\n");
127 	if (partial_status & SW_C3)
128 		printk("SW: condition bit 3\n");
129 	if (partial_status & SW_C2)
130 		printk("SW: condition bit 2\n");
131 	if (partial_status & SW_C1)
132 		printk("SW: condition bit 1\n");
133 	if (partial_status & SW_C0)
134 		printk("SW: condition bit 0\n");
135 	if (partial_status & SW_Summary)
136 		printk("SW: exception summary\n");
137 	if (partial_status & SW_Stack_Fault)
138 		printk("SW: stack fault\n");
139 	if (partial_status & SW_Precision)
140 		printk("SW: loss of precision\n");
141 	if (partial_status & SW_Underflow)
142 		printk("SW: underflow\n");
143 	if (partial_status & SW_Overflow)
144 		printk("SW: overflow\n");
145 	if (partial_status & SW_Zero_Div)
146 		printk("SW: divide by zero\n");
147 	if (partial_status & SW_Denorm_Op)
148 		printk("SW: denormalized operand\n");
149 	if (partial_status & SW_Invalid)
150 		printk("SW: invalid operation\n");
151 #endif /* DEBUGGING */
152 
153 	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 */
154 	       (partial_status & 0x3800) >> 11,	/* stack top pointer */
155 	       partial_status & 0x80 ? 1 : 0,	/* Error summary status */
156 	       partial_status & 0x40 ? 1 : 0,	/* Stack flag */
157 	       partial_status & SW_C3 ? 1 : 0, partial_status & SW_C2 ? 1 : 0,	/* cc */
158 	       partial_status & SW_C1 ? 1 : 0, partial_status & SW_C0 ? 1 : 0,	/* cc */
159 	       partial_status & SW_Precision ? 1 : 0,
160 	       partial_status & SW_Underflow ? 1 : 0,
161 	       partial_status & SW_Overflow ? 1 : 0,
162 	       partial_status & SW_Zero_Div ? 1 : 0,
163 	       partial_status & SW_Denorm_Op ? 1 : 0,
164 	       partial_status & SW_Invalid ? 1 : 0);
165 
166 	printk(" CW: ic=%d rc=%d%d pc=%d%d iem=%d     ef=%d%d%d%d%d%d\n",
167 	       control_word & 0x1000 ? 1 : 0,
168 	       (control_word & 0x800) >> 11, (control_word & 0x400) >> 10,
169 	       (control_word & 0x200) >> 9, (control_word & 0x100) >> 8,
170 	       control_word & 0x80 ? 1 : 0,
171 	       control_word & SW_Precision ? 1 : 0,
172 	       control_word & SW_Underflow ? 1 : 0,
173 	       control_word & SW_Overflow ? 1 : 0,
174 	       control_word & SW_Zero_Div ? 1 : 0,
175 	       control_word & SW_Denorm_Op ? 1 : 0,
176 	       control_word & SW_Invalid ? 1 : 0);
177 
178 	for (i = 0; i < 8; i++) {
179 		FPU_REG *r = &st(i);
180 		u_char tagi = FPU_gettagi(i);
181 
182 		switch (tagi) {
183 		case TAG_Empty:
184 			continue;
185 		case TAG_Zero:
186 		case TAG_Special:
187 			/* Update tagi for the printk below */
188 			tagi = FPU_Special(r);
189 			fallthrough;
190 		case TAG_Valid:
191 			printk("st(%d)  %c .%04lx %04lx %04lx %04lx e%+-6d ", i,
192 			       getsign(r) ? '-' : '+',
193 			       (long)(r->sigh >> 16),
194 			       (long)(r->sigh & 0xFFFF),
195 			       (long)(r->sigl >> 16),
196 			       (long)(r->sigl & 0xFFFF),
197 			       exponent(r) - EXP_BIAS + 1);
198 			break;
199 		default:
200 			printk("Whoops! Error in errors.c: tag%d is %d ", i,
201 			       tagi);
202 			continue;
203 		}
204 		printk("%s\n", tag_desc[(int)(unsigned)tagi]);
205 	}
206 
207 	RE_ENTRANT_CHECK_ON;
208 
209 }
210 
211 static struct {
212 	int type;
213 	const char *name;
214 } exception_names[] = {
215 	{
216 	EX_StackOver, "stack overflow"}, {
217 	EX_StackUnder, "stack underflow"}, {
218 	EX_Precision, "loss of precision"}, {
219 	EX_Underflow, "underflow"}, {
220 	EX_Overflow, "overflow"}, {
221 	EX_ZeroDiv, "divide by zero"}, {
222 	EX_Denormal, "denormalized operand"}, {
223 	EX_Invalid, "invalid operation"}, {
224 	EX_INTERNAL, "INTERNAL BUG in " FPU_VERSION}, {
225 	0, NULL}
226 };
227 
228 /*
229  EX_INTERNAL is always given with a code which indicates where the
230  error was detected.
231 
232  Internal error types:
233        0x14   in fpu_etc.c
234        0x1nn  in a *.c file:
235               0x101  in reg_add_sub.c
236               0x102  in reg_mul.c
237               0x104  in poly_atan.c
238               0x105  in reg_mul.c
239               0x107  in fpu_trig.c
240 	      0x108  in reg_compare.c
241 	      0x109  in reg_compare.c
242 	      0x110  in reg_add_sub.c
243 	      0x111  in fpe_entry.c
244 	      0x112  in fpu_trig.c
245 	      0x113  in errors.c
246 	      0x115  in fpu_trig.c
247 	      0x116  in fpu_trig.c
248 	      0x117  in fpu_trig.c
249 	      0x118  in fpu_trig.c
250 	      0x119  in fpu_trig.c
251 	      0x120  in poly_atan.c
252 	      0x121  in reg_compare.c
253 	      0x122  in reg_compare.c
254 	      0x123  in reg_compare.c
255 	      0x125  in fpu_trig.c
256 	      0x126  in fpu_entry.c
257 	      0x127  in poly_2xm1.c
258 	      0x128  in fpu_entry.c
259 	      0x129  in fpu_entry.c
260 	      0x130  in get_address.c
261 	      0x131  in get_address.c
262 	      0x132  in get_address.c
263 	      0x133  in get_address.c
264 	      0x140  in load_store.c
265 	      0x141  in load_store.c
266               0x150  in poly_sin.c
267               0x151  in poly_sin.c
268 	      0x160  in reg_ld_str.c
269 	      0x161  in reg_ld_str.c
270 	      0x162  in reg_ld_str.c
271 	      0x163  in reg_ld_str.c
272 	      0x164  in reg_ld_str.c
273 	      0x170  in fpu_tags.c
274 	      0x171  in fpu_tags.c
275 	      0x172  in fpu_tags.c
276 	      0x180  in reg_convert.c
277        0x2nn  in an *.S file:
278               0x201  in reg_u_add.S
279               0x202  in reg_u_div.S
280               0x203  in reg_u_div.S
281               0x204  in reg_u_div.S
282               0x205  in reg_u_mul.S
283               0x206  in reg_u_sub.S
284               0x207  in wm_sqrt.S
285 	      0x208  in reg_div.S
286               0x209  in reg_u_sub.S
287               0x210  in reg_u_sub.S
288               0x211  in reg_u_sub.S
289               0x212  in reg_u_sub.S
290 	      0x213  in wm_sqrt.S
291 	      0x214  in wm_sqrt.S
292 	      0x215  in wm_sqrt.S
293 	      0x220  in reg_norm.S
294 	      0x221  in reg_norm.S
295 	      0x230  in reg_round.S
296 	      0x231  in reg_round.S
297 	      0x232  in reg_round.S
298 	      0x233  in reg_round.S
299 	      0x234  in reg_round.S
300 	      0x235  in reg_round.S
301 	      0x236  in reg_round.S
302 	      0x240  in div_Xsig.S
303 	      0x241  in div_Xsig.S
304 	      0x242  in div_Xsig.S
305  */
306 
FPU_exception(int n)307 asmlinkage __visible void FPU_exception(int n)
308 {
309 	int i, int_type;
310 
311 	int_type = 0;		/* Needed only to stop compiler warnings */
312 	if (n & EX_INTERNAL) {
313 		int_type = n - EX_INTERNAL;
314 		n = EX_INTERNAL;
315 		/* Set lots of exception bits! */
316 		partial_status |= (SW_Exc_Mask | SW_Summary | SW_Backward);
317 	} else {
318 		/* Extract only the bits which we use to set the status word */
319 		n &= (SW_Exc_Mask);
320 		/* Set the corresponding exception bit */
321 		partial_status |= n;
322 		/* Set summary bits iff exception isn't masked */
323 		if (partial_status & ~control_word & CW_Exceptions)
324 			partial_status |= (SW_Summary | SW_Backward);
325 		if (n & (SW_Stack_Fault | EX_Precision)) {
326 			if (!(n & SW_C1))
327 				/* This bit distinguishes over- from underflow for a stack fault,
328 				   and roundup from round-down for precision loss. */
329 				partial_status &= ~SW_C1;
330 		}
331 	}
332 
333 	RE_ENTRANT_CHECK_OFF;
334 	if ((~control_word & n & CW_Exceptions) || (n == EX_INTERNAL)) {
335 		/* Get a name string for error reporting */
336 		for (i = 0; exception_names[i].type; i++)
337 			if ((exception_names[i].type & n) ==
338 			    exception_names[i].type)
339 				break;
340 
341 		if (exception_names[i].type) {
342 #ifdef PRINT_MESSAGES
343 			printk("FP Exception: %s!\n", exception_names[i].name);
344 #endif /* PRINT_MESSAGES */
345 		} else
346 			printk("FPU emulator: Unknown Exception: 0x%04x!\n", n);
347 
348 		if (n == EX_INTERNAL) {
349 			printk("FPU emulator: Internal error type 0x%04x\n",
350 			       int_type);
351 			FPU_printall();
352 		}
353 #ifdef PRINT_MESSAGES
354 		else
355 			FPU_printall();
356 #endif /* PRINT_MESSAGES */
357 
358 		/*
359 		 * The 80486 generates an interrupt on the next non-control FPU
360 		 * instruction. So we need some means of flagging it.
361 		 * We use the ES (Error Summary) bit for this.
362 		 */
363 	}
364 	RE_ENTRANT_CHECK_ON;
365 
366 #ifdef __DEBUG__
367 	math_abort(FPU_info, SIGFPE);
368 #endif /* __DEBUG__ */
369 
370 }
371 
372 /* Real operation attempted on a NaN. */
373 /* Returns < 0 if the exception is unmasked */
real_1op_NaN(FPU_REG * a)374 int real_1op_NaN(FPU_REG *a)
375 {
376 	int signalling, isNaN;
377 
378 	isNaN = (exponent(a) == EXP_OVER) && (a->sigh & 0x80000000);
379 
380 	/* The default result for the case of two "equal" NaNs (signs may
381 	   differ) is chosen to reproduce 80486 behaviour */
382 	signalling = isNaN && !(a->sigh & 0x40000000);
383 
384 	if (!signalling) {
385 		if (!isNaN) {	/* pseudo-NaN, or other unsupported? */
386 			if (control_word & CW_Invalid) {
387 				/* Masked response */
388 				reg_copy(&CONST_QNaN, a);
389 			}
390 			EXCEPTION(EX_Invalid);
391 			return (!(control_word & CW_Invalid) ? FPU_Exception :
392 				0) | TAG_Special;
393 		}
394 		return TAG_Special;
395 	}
396 
397 	if (control_word & CW_Invalid) {
398 		/* The masked response */
399 		if (!(a->sigh & 0x80000000)) {	/* pseudo-NaN ? */
400 			reg_copy(&CONST_QNaN, a);
401 		}
402 		/* ensure a Quiet NaN */
403 		a->sigh |= 0x40000000;
404 	}
405 
406 	EXCEPTION(EX_Invalid);
407 
408 	return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Special;
409 }
410 
411 /* Real operation attempted on two operands, one a NaN. */
412 /* Returns < 0 if the exception is unmasked */
real_2op_NaN(FPU_REG const * b,u_char tagb,int deststnr,FPU_REG const * defaultNaN)413 int real_2op_NaN(FPU_REG const *b, u_char tagb,
414 		 int deststnr, FPU_REG const *defaultNaN)
415 {
416 	FPU_REG *dest = &st(deststnr);
417 	FPU_REG const *a = dest;
418 	u_char taga = FPU_gettagi(deststnr);
419 	FPU_REG const *x;
420 	int signalling, unsupported;
421 
422 	if (taga == TAG_Special)
423 		taga = FPU_Special(a);
424 	if (tagb == TAG_Special)
425 		tagb = FPU_Special(b);
426 
427 	/* TW_NaN is also used for unsupported data types. */
428 	unsupported = ((taga == TW_NaN)
429 		       && !((exponent(a) == EXP_OVER)
430 			    && (a->sigh & 0x80000000)))
431 	    || ((tagb == TW_NaN)
432 		&& !((exponent(b) == EXP_OVER) && (b->sigh & 0x80000000)));
433 	if (unsupported) {
434 		if (control_word & CW_Invalid) {
435 			/* Masked response */
436 			FPU_copy_to_regi(&CONST_QNaN, TAG_Special, deststnr);
437 		}
438 		EXCEPTION(EX_Invalid);
439 		return (!(control_word & CW_Invalid) ? FPU_Exception : 0) |
440 		    TAG_Special;
441 	}
442 
443 	if (taga == TW_NaN) {
444 		x = a;
445 		if (tagb == TW_NaN) {
446 			signalling = !(a->sigh & b->sigh & 0x40000000);
447 			if (significand(b) > significand(a))
448 				x = b;
449 			else if (significand(b) == significand(a)) {
450 				/* The default result for the case of two "equal" NaNs (signs may
451 				   differ) is chosen to reproduce 80486 behaviour */
452 				x = defaultNaN;
453 			}
454 		} else {
455 			/* return the quiet version of the NaN in a */
456 			signalling = !(a->sigh & 0x40000000);
457 		}
458 	} else
459 #ifdef PARANOID
460 	if (tagb == TW_NaN)
461 #endif /* PARANOID */
462 	{
463 		signalling = !(b->sigh & 0x40000000);
464 		x = b;
465 	}
466 #ifdef PARANOID
467 	else {
468 		signalling = 0;
469 		EXCEPTION(EX_INTERNAL | 0x113);
470 		x = &CONST_QNaN;
471 	}
472 #endif /* PARANOID */
473 
474 	if ((!signalling) || (control_word & CW_Invalid)) {
475 		if (!x)
476 			x = b;
477 
478 		if (!(x->sigh & 0x80000000))	/* pseudo-NaN ? */
479 			x = &CONST_QNaN;
480 
481 		FPU_copy_to_regi(x, TAG_Special, deststnr);
482 
483 		if (!signalling)
484 			return TAG_Special;
485 
486 		/* ensure a Quiet NaN */
487 		dest->sigh |= 0x40000000;
488 	}
489 
490 	EXCEPTION(EX_Invalid);
491 
492 	return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Special;
493 }
494 
495 /* Invalid arith operation on Valid registers */
496 /* Returns < 0 if the exception is unmasked */
arith_invalid(int deststnr)497 asmlinkage __visible int arith_invalid(int deststnr)
498 {
499 
500 	EXCEPTION(EX_Invalid);
501 
502 	if (control_word & CW_Invalid) {
503 		/* The masked response */
504 		FPU_copy_to_regi(&CONST_QNaN, TAG_Special, deststnr);
505 	}
506 
507 	return (!(control_word & CW_Invalid) ? FPU_Exception : 0) | TAG_Valid;
508 
509 }
510 
511 /* Divide a finite number by zero */
FPU_divide_by_zero(int deststnr,u_char sign)512 asmlinkage __visible int FPU_divide_by_zero(int deststnr, u_char sign)
513 {
514 	FPU_REG *dest = &st(deststnr);
515 	int tag = TAG_Valid;
516 
517 	if (control_word & CW_ZeroDiv) {
518 		/* The masked response */
519 		FPU_copy_to_regi(&CONST_INF, TAG_Special, deststnr);
520 		setsign(dest, sign);
521 		tag = TAG_Special;
522 	}
523 
524 	EXCEPTION(EX_ZeroDiv);
525 
526 	return (!(control_word & CW_ZeroDiv) ? FPU_Exception : 0) | tag;
527 
528 }
529 
530 /* This may be called often, so keep it lean */
set_precision_flag(int flags)531 int set_precision_flag(int flags)
532 {
533 	if (control_word & CW_Precision) {
534 		partial_status &= ~(SW_C1 & flags);
535 		partial_status |= flags;	/* The masked response */
536 		return 0;
537 	} else {
538 		EXCEPTION(flags);
539 		return 1;
540 	}
541 }
542 
543 /* This may be called often, so keep it lean */
set_precision_flag_up(void)544 asmlinkage __visible void set_precision_flag_up(void)
545 {
546 	if (control_word & CW_Precision)
547 		partial_status |= (SW_Precision | SW_C1);	/* The masked response */
548 	else
549 		EXCEPTION(EX_Precision | SW_C1);
550 }
551 
552 /* This may be called often, so keep it lean */
set_precision_flag_down(void)553 asmlinkage __visible void set_precision_flag_down(void)
554 {
555 	if (control_word & CW_Precision) {	/* The masked response */
556 		partial_status &= ~SW_C1;
557 		partial_status |= SW_Precision;
558 	} else
559 		EXCEPTION(EX_Precision);
560 }
561 
denormal_operand(void)562 asmlinkage __visible int denormal_operand(void)
563 {
564 	if (control_word & CW_Denormal) {	/* The masked response */
565 		partial_status |= SW_Denorm_Op;
566 		return TAG_Special;
567 	} else {
568 		EXCEPTION(EX_Denormal);
569 		return TAG_Special | FPU_Exception;
570 	}
571 }
572 
arith_overflow(FPU_REG * dest)573 asmlinkage __visible int arith_overflow(FPU_REG *dest)
574 {
575 	int tag = TAG_Valid;
576 
577 	if (control_word & CW_Overflow) {
578 		/* The masked response */
579 /* ###### The response here depends upon the rounding mode */
580 		reg_copy(&CONST_INF, dest);
581 		tag = TAG_Special;
582 	} else {
583 		/* Subtract the magic number from the exponent */
584 		addexponent(dest, (-3 * (1 << 13)));
585 	}
586 
587 	EXCEPTION(EX_Overflow);
588 	if (control_word & CW_Overflow) {
589 		/* The overflow exception is masked. */
590 		/* By definition, precision is lost.
591 		   The roundup bit (C1) is also set because we have
592 		   "rounded" upwards to Infinity. */
593 		EXCEPTION(EX_Precision | SW_C1);
594 		return tag;
595 	}
596 
597 	return tag;
598 
599 }
600 
arith_underflow(FPU_REG * dest)601 asmlinkage __visible int arith_underflow(FPU_REG *dest)
602 {
603 	int tag = TAG_Valid;
604 
605 	if (control_word & CW_Underflow) {
606 		/* The masked response */
607 		if (exponent16(dest) <= EXP_UNDER - 63) {
608 			reg_copy(&CONST_Z, dest);
609 			partial_status &= ~SW_C1;	/* Round down. */
610 			tag = TAG_Zero;
611 		} else {
612 			stdexp(dest);
613 		}
614 	} else {
615 		/* Add the magic number to the exponent. */
616 		addexponent(dest, (3 * (1 << 13)) + EXTENDED_Ebias);
617 	}
618 
619 	EXCEPTION(EX_Underflow);
620 	if (control_word & CW_Underflow) {
621 		/* The underflow exception is masked. */
622 		EXCEPTION(EX_Precision);
623 		return tag;
624 	}
625 
626 	return tag;
627 
628 }
629 
FPU_stack_overflow(void)630 void FPU_stack_overflow(void)
631 {
632 
633 	if (control_word & CW_Invalid) {
634 		/* The masked response */
635 		top--;
636 		FPU_copy_to_reg0(&CONST_QNaN, TAG_Special);
637 	}
638 
639 	EXCEPTION(EX_StackOver);
640 
641 	return;
642 
643 }
644 
FPU_stack_underflow(void)645 void FPU_stack_underflow(void)
646 {
647 
648 	if (control_word & CW_Invalid) {
649 		/* The masked response */
650 		FPU_copy_to_reg0(&CONST_QNaN, TAG_Special);
651 	}
652 
653 	EXCEPTION(EX_StackUnder);
654 
655 	return;
656 
657 }
658 
FPU_stack_underflow_i(int i)659 void FPU_stack_underflow_i(int i)
660 {
661 
662 	if (control_word & CW_Invalid) {
663 		/* The masked response */
664 		FPU_copy_to_regi(&CONST_QNaN, TAG_Special, i);
665 	}
666 
667 	EXCEPTION(EX_StackUnder);
668 
669 	return;
670 
671 }
672 
FPU_stack_underflow_pop(int i)673 void FPU_stack_underflow_pop(int i)
674 {
675 
676 	if (control_word & CW_Invalid) {
677 		/* The masked response */
678 		FPU_copy_to_regi(&CONST_QNaN, TAG_Special, i);
679 		FPU_pop();
680 	}
681 
682 	EXCEPTION(EX_StackUnder);
683 
684 	return;
685 
686 }
687