5113f6f70
 김현기
kernel add
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
|
.file "reg_u_div.S"
/*---------------------------------------------------------------------------+
| reg_u_div.S |
| |
| Divide one FPU_REG by another and put the result in a destination FPU_REG.|
| |
| Copyright (C) 1992,1993,1995,1997 |
| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
| E-mail billm@suburbia.net |
| |
| |
+---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------+
| Call from C as: |
| int FPU_u_div(FPU_REG *a, FPU_REG *b, FPU_REG *dest, |
| unsigned int control_word, char *sign) |
| |
| Does not compute the destination exponent, but does adjust it. |
| |
| Return value is the tag of the answer, or-ed with FPU_Exception if |
| one was raised, or -1 on internal error. |
+---------------------------------------------------------------------------*/
#include "exception.h"
#include "fpu_emu.h"
#include "control_w.h"
/* #define dSIGL(x) (x) */
/* #define dSIGH(x) 4(x) */
#ifndef NON_REENTRANT_FPU
/*
Local storage on the stack:
Result: FPU_accum_3:FPU_accum_2:FPU_accum_1:FPU_accum_0
Overflow flag: ovfl_flag
*/
#define FPU_accum_3 -4(%ebp)
#define FPU_accum_2 -8(%ebp)
#define FPU_accum_1 -12(%ebp)
#define FPU_accum_0 -16(%ebp)
#define FPU_result_1 -20(%ebp)
#define FPU_result_2 -24(%ebp)
#define FPU_ovfl_flag -28(%ebp)
#else
.data
/*
Local storage in a static area:
Result: FPU_accum_3:FPU_accum_2:FPU_accum_1:FPU_accum_0
Overflow flag: ovfl_flag
*/
.align 4,0
FPU_accum_3:
.long 0
FPU_accum_2:
.long 0
FPU_accum_1:
.long 0
FPU_accum_0:
.long 0
FPU_result_1:
.long 0
FPU_result_2:
.long 0
FPU_ovfl_flag:
.byte 0
#endif /* NON_REENTRANT_FPU */
#define REGA PARAM1
#define REGB PARAM2
#define DEST PARAM3
.text
ENTRY(FPU_u_div)
pushl %ebp
movl %esp,%ebp
#ifndef NON_REENTRANT_FPU
subl $28,%esp
#endif /* NON_REENTRANT_FPU */
pushl %esi
pushl %edi
pushl %ebx
movl REGA,%esi
movl REGB,%ebx
movl DEST,%edi
movswl EXP(%esi),%edx
movswl EXP(%ebx),%eax
subl %eax,%edx
addl EXP_BIAS,%edx
/* A denormal and a large number can cause an exponent underflow */
cmpl EXP_WAY_UNDER,%edx
jg xExp_not_underflow
/* Set to a really low value allow correct handling */
movl EXP_WAY_UNDER,%edx
xExp_not_underflow:
movw %dx,EXP(%edi)
#ifdef PARANOID
/* testl $0x80000000, SIGH(%esi) // Dividend */
/* je L_bugged */
testl $0x80000000, SIGH(%ebx) /* Divisor */
je L_bugged
#endif /* PARANOID */
/* Check if the divisor can be treated as having just 32 bits */
cmpl $0,SIGL(%ebx)
jnz L_Full_Division /* Can't do a quick divide */
/* We should be able to zip through the division here */
movl SIGH(%ebx),%ecx /* The divisor */
movl SIGH(%esi),%edx /* Dividend */
movl SIGL(%esi),%eax /* Dividend */
cmpl %ecx,%edx
setaeb FPU_ovfl_flag /* Keep a record */
jb L_no_adjust
subl %ecx,%edx /* Prevent the overflow */
L_no_adjust:
/* Divide the 64 bit number by the 32 bit denominator */
divl %ecx
movl %eax,FPU_result_2
/* Work on the remainder of the first division */
xorl %eax,%eax
divl %ecx
movl %eax,FPU_result_1
/* Work on the remainder of the 64 bit division */
xorl %eax,%eax
divl %ecx
testb $255,FPU_ovfl_flag /* was the num > denom ? */
je L_no_overflow
/* Do the shifting here */
/* increase the exponent */
incw EXP(%edi)
/* shift the mantissa right one bit */
stc /* To set the ms bit */
rcrl FPU_result_2
rcrl FPU_result_1
rcrl %eax
L_no_overflow:
jmp LRound_precision /* Do the rounding as required */
/*---------------------------------------------------------------------------+
| Divide: Return arg1/arg2 to arg3. |
| |
| This routine does not use the exponents of arg1 and arg2, but does |
| adjust the exponent of arg3. |
| |
| The maximum returned value is (ignoring exponents) |
| .ffffffff ffffffff |
| ------------------ = 1.ffffffff fffffffe |
| .80000000 00000000 |
| and the minimum is |
| .80000000 00000000 |
| ------------------ = .80000000 00000001 (rounded) |
| .ffffffff ffffffff |
| |
+---------------------------------------------------------------------------*/
L_Full_Division:
/* Save extended dividend in local register */
movl SIGL(%esi),%eax
movl %eax,FPU_accum_2
movl SIGH(%esi),%eax
movl %eax,FPU_accum_3
xorl %eax,%eax
movl %eax,FPU_accum_1 /* zero the extension */
movl %eax,FPU_accum_0 /* zero the extension */
movl SIGL(%esi),%eax /* Get the current num */
movl SIGH(%esi),%edx
/*----------------------------------------------------------------------*/
/* Initialization done.
Do the first 32 bits. */
movb $0,FPU_ovfl_flag
cmpl SIGH(%ebx),%edx /* Test for imminent overflow */
jb LLess_than_1
ja LGreater_than_1
cmpl SIGL(%ebx),%eax
jb LLess_than_1
LGreater_than_1:
/* The dividend is greater or equal, would cause overflow */
setaeb FPU_ovfl_flag /* Keep a record */
subl SIGL(%ebx),%eax
sbbl SIGH(%ebx),%edx /* Prevent the overflow */
movl %eax,FPU_accum_2
movl %edx,FPU_accum_3
LLess_than_1:
/* At this point, we have a dividend < divisor, with a record of
adjustment in FPU_ovfl_flag */
/* We will divide by a number which is too large */
movl SIGH(%ebx),%ecx
addl $1,%ecx
jnc LFirst_div_not_1
/* here we need to divide by 100000000h,
i.e., no division at all.. */
mov %edx,%eax
jmp LFirst_div_done
LFirst_div_not_1:
divl %ecx /* Divide the numerator by the augmented
denom ms dw */
LFirst_div_done:
movl %eax,FPU_result_2 /* Put the result in the answer */
mull SIGH(%ebx) /* mul by the ms dw of the denom */
subl %eax,FPU_accum_2 /* Subtract from the num local reg */
sbbl %edx,FPU_accum_3
movl FPU_result_2,%eax /* Get the result back */
mull SIGL(%ebx) /* now mul the ls dw of the denom */
subl %eax,FPU_accum_1 /* Subtract from the num local reg */
sbbl %edx,FPU_accum_2
sbbl $0,FPU_accum_3
je LDo_2nd_32_bits /* Must check for non-zero result here */
#ifdef PARANOID
jb L_bugged_1
#endif /* PARANOID */
/* need to subtract another once of the denom */
incl FPU_result_2 /* Correct the answer */
movl SIGL(%ebx),%eax
movl SIGH(%ebx),%edx
subl %eax,FPU_accum_1 /* Subtract from the num local reg */
sbbl %edx,FPU_accum_2
#ifdef PARANOID
sbbl $0,FPU_accum_3
jne L_bugged_1 /* Must check for non-zero result here */
#endif /* PARANOID */
/*----------------------------------------------------------------------*/
/* Half of the main problem is done, there is just a reduced numerator
to handle now.
Work with the second 32 bits, FPU_accum_0 not used from now on */
LDo_2nd_32_bits:
movl FPU_accum_2,%edx /* get the reduced num */
movl FPU_accum_1,%eax
/* need to check for possible subsequent overflow */
cmpl SIGH(%ebx),%edx
jb LDo_2nd_div
ja LPrevent_2nd_overflow
cmpl SIGL(%ebx),%eax
jb LDo_2nd_div
LPrevent_2nd_overflow:
/* The numerator is greater or equal, would cause overflow */
/* prevent overflow */
subl SIGL(%ebx),%eax
sbbl SIGH(%ebx),%edx
movl %edx,FPU_accum_2
movl %eax,FPU_accum_1
incl FPU_result_2 /* Reflect the subtraction in the answer */
#ifdef PARANOID
je L_bugged_2 /* Can't bump the result to 1.0 */
#endif /* PARANOID */
LDo_2nd_div:
cmpl $0,%ecx /* augmented denom msw */
jnz LSecond_div_not_1
/* %ecx == 0, we are dividing by 1.0 */
mov %edx,%eax
jmp LSecond_div_done
LSecond_div_not_1:
divl %ecx /* Divide the numerator by the denom ms dw */
LSecond_div_done:
movl %eax,FPU_result_1 /* Put the result in the answer */
mull SIGH(%ebx) /* mul by the ms dw of the denom */
subl %eax,FPU_accum_1 /* Subtract from the num local reg */
sbbl %edx,FPU_accum_2
#ifdef PARANOID
jc L_bugged_2
#endif /* PARANOID */
movl FPU_result_1,%eax /* Get the result back */
mull SIGL(%ebx) /* now mul the ls dw of the denom */
subl %eax,FPU_accum_0 /* Subtract from the num local reg */
sbbl %edx,FPU_accum_1 /* Subtract from the num local reg */
sbbl $0,FPU_accum_2
#ifdef PARANOID
jc L_bugged_2
#endif /* PARANOID */
jz LDo_3rd_32_bits
#ifdef PARANOID
cmpl $1,FPU_accum_2
jne L_bugged_2
#endif /* PARANOID */
/* need to subtract another once of the denom */
movl SIGL(%ebx),%eax
movl SIGH(%ebx),%edx
subl %eax,FPU_accum_0 /* Subtract from the num local reg */
sbbl %edx,FPU_accum_1
sbbl $0,FPU_accum_2
#ifdef PARANOID
jc L_bugged_2
jne L_bugged_2
#endif /* PARANOID */
addl $1,FPU_result_1 /* Correct the answer */
adcl $0,FPU_result_2
#ifdef PARANOID
jc L_bugged_2 /* Must check for non-zero result here */
#endif /* PARANOID */
/*----------------------------------------------------------------------*/
/* The division is essentially finished here, we just need to perform
tidying operations.
Deal with the 3rd 32 bits */
LDo_3rd_32_bits:
movl FPU_accum_1,%edx /* get the reduced num */
movl FPU_accum_0,%eax
/* need to check for possible subsequent overflow */
cmpl SIGH(%ebx),%edx /* denom */
jb LRound_prep
ja LPrevent_3rd_overflow
cmpl SIGL(%ebx),%eax /* denom */
jb LRound_prep
LPrevent_3rd_overflow:
/* prevent overflow */
subl SIGL(%ebx),%eax
sbbl SIGH(%ebx),%edx
movl %edx,FPU_accum_1
movl %eax,FPU_accum_0
addl $1,FPU_result_1 /* Reflect the subtraction in the answer */
adcl $0,FPU_result_2
jne LRound_prep
jnc LRound_prep
/* This is a tricky spot, there is an overflow of the answer */
movb $255,FPU_ovfl_flag /* Overflow -> 1.000 */
LRound_prep:
/*
* Prepare for rounding.
* To test for rounding, we just need to compare 2*accum with the
* denom.
*/
movl FPU_accum_0,%ecx
movl FPU_accum_1,%edx
movl %ecx,%eax
orl %edx,%eax
jz LRound_ovfl /* The accumulator contains zero. */
/* Multiply by 2 */
clc
rcll $1,%ecx
rcll $1,%edx
jc LRound_large /* No need to compare, denom smaller */
subl SIGL(%ebx),%ecx
sbbl SIGH(%ebx),%edx
jnc LRound_not_small
movl $0x70000000,%eax /* Denom was larger */
jmp LRound_ovfl
LRound_not_small:
jnz LRound_large
movl $0x80000000,%eax /* Remainder was exactly 1/2 denom */
jmp LRound_ovfl
LRound_large:
movl $0xff000000,%eax /* Denom was smaller */
LRound_ovfl:
/* We are now ready to deal with rounding, but first we must get
the bits properly aligned */
testb $255,FPU_ovfl_flag /* was the num > denom ? */
je LRound_precision
incw EXP(%edi)
/* shift the mantissa right one bit */
stc /* Will set the ms bit */
rcrl FPU_result_2
rcrl FPU_result_1
rcrl %eax
/* Round the result as required */
LRound_precision:
decw EXP(%edi) /* binary point between 1st & 2nd bits */
movl %eax,%edx
movl FPU_result_1,%ebx
movl FPU_result_2,%eax
jmp fpu_reg_round
#ifdef PARANOID
/* The logic is wrong if we got here */
L_bugged:
pushl EX_INTERNAL|0x202
call EXCEPTION
pop %ebx
jmp L_exit
L_bugged_1:
pushl EX_INTERNAL|0x203
call EXCEPTION
pop %ebx
jmp L_exit
L_bugged_2:
pushl EX_INTERNAL|0x204
call EXCEPTION
pop %ebx
jmp L_exit
L_exit:
movl $-1,%eax
popl %ebx
popl %edi
popl %esi
leave
ret
#endif /* PARANOID */
|