summaryrefslogtreecommitdiff
path: root/libgcc/config/libbid/bid128_next.c
blob: 11688c1c1d67731afa1d12952b93461cd0c651f7 (plain)
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
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
/* Copyright (C) 2007, 2009  Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */

#define BID_128RES
#include "bid_internal.h"

/*****************************************************************************
 *  BID128 nextup
 ****************************************************************************/

#if DECIMAL_CALL_BY_REFERENCE
void
bid128_nextup (UINT128 * pres,
	       UINT128 *
	       px _EXC_FLAGS_PARAM _EXC_MASKS_PARAM _EXC_INFO_PARAM) {
  UINT128 x = *px;
#else
UINT128
bid128_nextup (UINT128 x _EXC_FLAGS_PARAM _EXC_MASKS_PARAM
	       _EXC_INFO_PARAM) {
#endif

  UINT128 res;
  UINT64 x_sign;
  UINT64 x_exp;
  int exp;
  BID_UI64DOUBLE tmp1;
  int x_nr_bits;
  int q1, ind;
  UINT128 C1;			// C1.w[1], C1.w[0] represent x_signif_hi, x_signif_lo (UINT64)

  BID_SWAP128 (x);
  // unpack the argument
  x_sign = x.w[1] & MASK_SIGN;	// 0 for positive, MASK_SIGN for negative
  C1.w[1] = x.w[1] & MASK_COEFF;
  C1.w[0] = x.w[0];

  // check for NaN or Infinity
  if ((x.w[1] & MASK_SPECIAL) == MASK_SPECIAL) {
    // x is special
    if ((x.w[1] & MASK_NAN) == MASK_NAN) {	// x is NAN
      // if x = NaN, then res = Q (x)
      // check first for non-canonical NaN payload
      if (((x.w[1] & 0x00003fffffffffffull) > 0x0000314dc6448d93ull) ||
	  (((x.w[1] & 0x00003fffffffffffull) == 0x0000314dc6448d93ull)
	   && (x.w[0] > 0x38c15b09ffffffffull))) {
	x.w[1] = x.w[1] & 0xffffc00000000000ull;
	x.w[0] = 0x0ull;
      }
      if ((x.w[1] & MASK_SNAN) == MASK_SNAN) {	// x is SNAN
	// set invalid flag
	*pfpsf |= INVALID_EXCEPTION;
	// return quiet (x)
	res.w[1] = x.w[1] & 0xfc003fffffffffffull;	// clear out also G[6]-G[16]
	res.w[0] = x.w[0];
      } else {	// x is QNaN
	// return x
	res.w[1] = x.w[1] & 0xfc003fffffffffffull;	// clear out G[6]-G[16]
	res.w[0] = x.w[0];
      }
    } else {	// x is not NaN, so it must be infinity
      if (!x_sign) {	// x is +inf
	res.w[1] = 0x7800000000000000ull;	// +inf
	res.w[0] = 0x0000000000000000ull;
      } else {	// x is -inf
	res.w[1] = 0xdfffed09bead87c0ull;	// -MAXFP = -999...99 * 10^emax
	res.w[0] = 0x378d8e63ffffffffull;
      }
    }
    BID_RETURN (res);
  }
  // check for non-canonical values (treated as zero)
  if ((x.w[1] & 0x6000000000000000ull) == 0x6000000000000000ull) {	// G0_G1=11
    // non-canonical
    x_exp = (x.w[1] << 2) & MASK_EXP;	// biased and shifted left 49 bits
    C1.w[1] = 0;	// significand high
    C1.w[0] = 0;	// significand low
  } else {	// G0_G1 != 11
    x_exp = x.w[1] & MASK_EXP;	// biased and shifted left 49 bits
    if (C1.w[1] > 0x0001ed09bead87c0ull ||
	(C1.w[1] == 0x0001ed09bead87c0ull
	 && C1.w[0] > 0x378d8e63ffffffffull)) {
      // x is non-canonical if coefficient is larger than 10^34 -1
      C1.w[1] = 0;
      C1.w[0] = 0;
    } else {	// canonical
      ;
    }
  }

  if ((C1.w[1] == 0x0ull) && (C1.w[0] == 0x0ull)) {
    // x is +/-0
    res.w[1] = 0x0000000000000000ull;	// +1 * 10^emin
    res.w[0] = 0x0000000000000001ull;
  } else {	// x is not special and is not zero
    if (x.w[1] == 0x5fffed09bead87c0ull
	&& x.w[0] == 0x378d8e63ffffffffull) {
      // x = +MAXFP = 999...99 * 10^emax
      res.w[1] = 0x7800000000000000ull;	// +inf
      res.w[0] = 0x0000000000000000ull;
    } else if (x.w[1] == 0x8000000000000000ull
	       && x.w[0] == 0x0000000000000001ull) {
      // x = -MINFP = 1...99 * 10^emin
      res.w[1] = 0x8000000000000000ull;	// -0
      res.w[0] = 0x0000000000000000ull;
    } else {	// -MAXFP <= x <= -MINFP - 1 ulp OR MINFP <= x <= MAXFP - 1 ulp
      // can add/subtract 1 ulp to the significand

      // Note: we could check here if x >= 10^34 to speed up the case q1 = 34
      // q1 = nr. of decimal digits in x
      // determine first the nr. of bits in x
      if (C1.w[1] == 0) {
	if (C1.w[0] >= 0x0020000000000000ull) {	// x >= 2^53
	  // split the 64-bit value in two 32-bit halves to avoid rnd errors
	  if (C1.w[0] >= 0x0000000100000000ull) {	// x >= 2^32
	    tmp1.d = (double) (C1.w[0] >> 32);	// exact conversion
	    x_nr_bits =
	      33 + ((((unsigned int) (tmp1.ui64 >> 52)) & 0x7ff) -
		    0x3ff);
	  } else {	// x < 2^32
	    tmp1.d = (double) (C1.w[0]);	// exact conversion
	    x_nr_bits =
	      1 + ((((unsigned int) (tmp1.ui64 >> 52)) & 0x7ff) -
		   0x3ff);
	  }
	} else {	// if x < 2^53
	  tmp1.d = (double) C1.w[0];	// exact conversion
	  x_nr_bits =
	    1 + ((((unsigned int) (tmp1.ui64 >> 52)) & 0x7ff) - 0x3ff);
	}
      } else {	// C1.w[1] != 0 => nr. bits = 64 + nr_bits (C1.w[1])
	tmp1.d = (double) C1.w[1];	// exact conversion
	x_nr_bits =
	  65 + ((((unsigned int) (tmp1.ui64 >> 52)) & 0x7ff) - 0x3ff);
      }
      q1 = nr_digits[x_nr_bits - 1].digits;
      if (q1 == 0) {
	q1 = nr_digits[x_nr_bits - 1].digits1;
	if (C1.w[1] > nr_digits[x_nr_bits - 1].threshold_hi
	    || (C1.w[1] == nr_digits[x_nr_bits - 1].threshold_hi
		&& C1.w[0] >= nr_digits[x_nr_bits - 1].threshold_lo))
	  q1++;
      }
      // if q1 < P34 then pad the significand with zeros
      if (q1 < P34) {
	exp = (x_exp >> 49) - 6176;
	if (exp + 6176 > P34 - q1) {
	  ind = P34 - q1;	// 1 <= ind <= P34 - 1
	  // pad with P34 - q1 zeros, until exponent = emin
	  // C1 = C1 * 10^ind
	  if (q1 <= 19) {	// 64-bit C1
	    if (ind <= 19) {	// 64-bit 10^ind and 64-bit C1
	      __mul_64x64_to_128MACH (C1, C1.w[0], ten2k64[ind]);
	    } else {	// 128-bit 10^ind and 64-bit C1
	      __mul_128x64_to_128 (C1, C1.w[0], ten2k128[ind - 20]);
	    }
	  } else {	// C1 is (most likely) 128-bit
	    if (ind <= 14) {	// 64-bit 10^ind and 128-bit C1 (most likely)
	      __mul_128x64_to_128 (C1, ten2k64[ind], C1);
	    } else if (ind <= 19) {	// 64-bit 10^ind and 64-bit C1 (q1 <= 19)
	      __mul_64x64_to_128MACH (C1, C1.w[0], ten2k64[ind]);
	    } else {	// 128-bit 10^ind and 64-bit C1 (C1 must be 64-bit)
	      __mul_128x64_to_128 (C1, C1.w[0], ten2k128[ind - 20]);
	    }
	  }
	  x_exp = x_exp - ((UINT64) ind << 49);
	} else {	// pad with zeros until the exponent reaches emin
	  ind = exp + 6176;
	  // C1 = C1 * 10^ind
	  if (ind <= 19) {	// 1 <= P34 - q1 <= 19 <=> 15 <= q1 <= 33
	    if (q1 <= 19) {	// 64-bit C1, 64-bit 10^ind 
	      __mul_64x64_to_128MACH (C1, C1.w[0], ten2k64[ind]);
	    } else {	// 20 <= q1 <= 33 => 128-bit C1, 64-bit 10^ind
	      __mul_128x64_to_128 (C1, ten2k64[ind], C1);
	    }
	  } else {	// if 20 <= P34 - q1 <= 33 <=> 1 <= q1 <= 14 =>
	    // 64-bit C1, 128-bit 10^ind
	    __mul_128x64_to_128 (C1, C1.w[0], ten2k128[ind - 20]);
	  }
	  x_exp = EXP_MIN;
	}
      }
      if (!x_sign) {	// x > 0
	// add 1 ulp (add 1 to the significand)
	C1.w[0]++;
	if (C1.w[0] == 0)
	  C1.w[1]++;
	if (C1.w[1] == 0x0001ed09bead87c0ull && C1.w[0] == 0x378d8e6400000000ull) {	// if  C1 = 10^34
	  C1.w[1] = 0x0000314dc6448d93ull;	// C1 = 10^33
	  C1.w[0] = 0x38c15b0a00000000ull;
	  x_exp = x_exp + EXP_P1;
	}
      } else {	// x < 0
	// subtract 1 ulp (subtract 1 from the significand)
	C1.w[0]--;
	if (C1.w[0] == 0xffffffffffffffffull)
	  C1.w[1]--;
	if (x_exp != 0 && C1.w[1] == 0x0000314dc6448d93ull && C1.w[0] == 0x38c15b09ffffffffull) {	// if  C1 = 10^33 - 1
	  C1.w[1] = 0x0001ed09bead87c0ull;	// C1 = 10^34 - 1
	  C1.w[0] = 0x378d8e63ffffffffull;
	  x_exp = x_exp - EXP_P1;
	}
      }
      // assemble the result
      res.w[1] = x_sign | x_exp | C1.w[1];
      res.w[0] = C1.w[0];
    }	// end -MAXFP <= x <= -MINFP - 1 ulp OR MINFP <= x <= MAXFP - 1 ulp
  }	// end x is not special and is not zero
  BID_RETURN (res);
}

/*****************************************************************************
 *  BID128 nextdown
 ****************************************************************************/

#if DECIMAL_CALL_BY_REFERENCE
void
bid128_nextdown (UINT128 * pres,
		 UINT128 *
		 px _EXC_FLAGS_PARAM _EXC_MASKS_PARAM _EXC_INFO_PARAM) {
  UINT128 x = *px;
#else
UINT128
bid128_nextdown (UINT128 x _EXC_FLAGS_PARAM _EXC_MASKS_PARAM
		 _EXC_INFO_PARAM) {
#endif

  UINT128 res;
  UINT64 x_sign;
  UINT64 x_exp;
  int exp;
  BID_UI64DOUBLE tmp1;
  int x_nr_bits;
  int q1, ind;
  UINT128 C1;			// C1.w[1], C1.w[0] represent x_signif_hi, x_signif_lo (UINT64)

  BID_SWAP128 (x);
  // unpack the argument
  x_sign = x.w[1] & MASK_SIGN;	// 0 for positive, MASK_SIGN for negative
  C1.w[1] = x.w[1] & MASK_COEFF;
  C1.w[0] = x.w[0];

  // check for NaN or Infinity
  if ((x.w[1] & MASK_SPECIAL) == MASK_SPECIAL) {
    // x is special
    if ((x.w[1] & MASK_NAN) == MASK_NAN) {	// x is NAN
      // if x = NaN, then res = Q (x)
      // check first for non-canonical NaN payload
      if (((x.w[1] & 0x00003fffffffffffull) > 0x0000314dc6448d93ull) ||
	  (((x.w[1] & 0x00003fffffffffffull) == 0x0000314dc6448d93ull)
	   && (x.w[0] > 0x38c15b09ffffffffull))) {
	x.w[1] = x.w[1] & 0xffffc00000000000ull;
	x.w[0] = 0x0ull;
      }
      if ((x.w[1] & MASK_SNAN) == MASK_SNAN) {	// x is SNAN
	// set invalid flag
	*pfpsf |= INVALID_EXCEPTION;
	// return quiet (x)
	res.w[1] = x.w[1] & 0xfc003fffffffffffull;	// clear out also G[6]-G[16]
	res.w[0] = x.w[0];
      } else {	// x is QNaN
	// return x
	res.w[1] = x.w[1] & 0xfc003fffffffffffull;	// clear out G[6]-G[16]
	res.w[0] = x.w[0];
      }
    } else {	// x is not NaN, so it must be infinity
      if (!x_sign) {	// x is +inf
	res.w[1] = 0x5fffed09bead87c0ull;	// +MAXFP = +999...99 * 10^emax
	res.w[0] = 0x378d8e63ffffffffull;
      } else {	// x is -inf
	res.w[1] = 0xf800000000000000ull;	// -inf
	res.w[0] = 0x0000000000000000ull;
      }
    }
    BID_RETURN (res);
  }
  // check for non-canonical values (treated as zero)
  if ((x.w[1] & 0x6000000000000000ull) == 0x6000000000000000ull) {	// G0_G1=11
    // non-canonical
    x_exp = (x.w[1] << 2) & MASK_EXP;	// biased and shifted left 49 bits
    C1.w[1] = 0;	// significand high
    C1.w[0] = 0;	// significand low
  } else {	// G0_G1 != 11
    x_exp = x.w[1] & MASK_EXP;	// biased and shifted left 49 bits
    if (C1.w[1] > 0x0001ed09bead87c0ull ||
	(C1.w[1] == 0x0001ed09bead87c0ull
	 && C1.w[0] > 0x378d8e63ffffffffull)) {
      // x is non-canonical if coefficient is larger than 10^34 -1
      C1.w[1] = 0;
      C1.w[0] = 0;
    } else {	// canonical
      ;
    }
  }

  if ((C1.w[1] == 0x0ull) && (C1.w[0] == 0x0ull)) {
    // x is +/-0
    res.w[1] = 0x8000000000000000ull;	// -1 * 10^emin
    res.w[0] = 0x0000000000000001ull;
  } else {	// x is not special and is not zero
    if (x.w[1] == 0xdfffed09bead87c0ull
	&& x.w[0] == 0x378d8e63ffffffffull) {
      // x = -MAXFP = -999...99 * 10^emax
      res.w[1] = 0xf800000000000000ull;	// -inf
      res.w[0] = 0x0000000000000000ull;
    } else if (x.w[1] == 0x0ull && x.w[0] == 0x0000000000000001ull) {	// +MINFP
      res.w[1] = 0x0000000000000000ull;	// +0
      res.w[0] = 0x0000000000000000ull;
    } else {	// -MAXFP <= x <= -MINFP - 1 ulp OR MINFP <= x <= MAXFP - 1 ulp
      // can add/subtract 1 ulp to the significand

      // Note: we could check here if x >= 10^34 to speed up the case q1 = 34
      // q1 = nr. of decimal digits in x
      // determine first the nr. of bits in x
      if (C1.w[1] == 0) {
	if (C1.w[0] >= 0x0020000000000000ull) {	// x >= 2^53
	  // split the 64-bit value in two 32-bit halves to avoid rnd errors
	  if (C1.w[0] >= 0x0000000100000000ull) {	// x >= 2^32
	    tmp1.d = (double) (C1.w[0] >> 32);	// exact conversion
	    x_nr_bits =
	      33 + ((((unsigned int) (tmp1.ui64 >> 52)) & 0x7ff) -
		    0x3ff);
	  } else {	// x < 2^32
	    tmp1.d = (double) (C1.w[0]);	// exact conversion
	    x_nr_bits =
	      1 + ((((unsigned int) (tmp1.ui64 >> 52)) & 0x7ff) -
		   0x3ff);
	  }
	} else {	// if x < 2^53
	  tmp1.d = (double) C1.w[0];	// exact conversion
	  x_nr_bits =
	    1 + ((((unsigned int) (tmp1.ui64 >> 52)) & 0x7ff) - 0x3ff);
	}
      } else {	// C1.w[1] != 0 => nr. bits = 64 + nr_bits (C1.w[1])
	tmp1.d = (double) C1.w[1];	// exact conversion
	x_nr_bits =
	  65 + ((((unsigned int) (tmp1.ui64 >> 52)) & 0x7ff) - 0x3ff);
      }
      q1 = nr_digits[x_nr_bits - 1].digits;
      if (q1 == 0) {
	q1 = nr_digits[x_nr_bits - 1].digits1;
	if (C1.w[1] > nr_digits[x_nr_bits - 1].threshold_hi
	    || (C1.w[1] == nr_digits[x_nr_bits - 1].threshold_hi
		&& C1.w[0] >= nr_digits[x_nr_bits - 1].threshold_lo))
	  q1++;
      }
      // if q1 < P then pad the significand with zeros
      if (q1 < P34) {
	exp = (x_exp >> 49) - 6176;
	if (exp + 6176 > P34 - q1) {
	  ind = P34 - q1;	// 1 <= ind <= P34 - 1
	  // pad with P34 - q1 zeros, until exponent = emin
	  // C1 = C1 * 10^ind
	  if (q1 <= 19) {	// 64-bit C1
	    if (ind <= 19) {	// 64-bit 10^ind and 64-bit C1
	      __mul_64x64_to_128MACH (C1, C1.w[0], ten2k64[ind]);
	    } else {	// 128-bit 10^ind and 64-bit C1
	      __mul_128x64_to_128 (C1, C1.w[0], ten2k128[ind - 20]);
	    }
	  } else {	// C1 is (most likely) 128-bit
	    if (ind <= 14) {	// 64-bit 10^ind and 128-bit C1 (most likely)
	      __mul_128x64_to_128 (C1, ten2k64[ind], C1);
	    } else if (ind <= 19) {	// 64-bit 10^ind and 64-bit C1 (q1 <= 19)
	      __mul_64x64_to_128MACH (C1, C1.w[0], ten2k64[ind]);
	    } else {	// 128-bit 10^ind and 64-bit C1 (C1 must be 64-bit)
	      __mul_128x64_to_128 (C1, C1.w[0], ten2k128[ind - 20]);
	    }
	  }
	  x_exp = x_exp - ((UINT64) ind << 49);
	} else {	// pad with zeros until the exponent reaches emin
	  ind = exp + 6176;
	  // C1 = C1 * 10^ind
	  if (ind <= 19) {	// 1 <= P34 - q1 <= 19 <=> 15 <= q1 <= 33
	    if (q1 <= 19) {	// 64-bit C1, 64-bit 10^ind 
	      __mul_64x64_to_128MACH (C1, C1.w[0], ten2k64[ind]);
	    } else {	// 20 <= q1 <= 33 => 128-bit C1, 64-bit 10^ind
	      __mul_128x64_to_128 (C1, ten2k64[ind], C1);
	    }
	  } else {	// if 20 <= P34 - q1 <= 33 <=> 1 <= q1 <= 14 =>
	    // 64-bit C1, 128-bit 10^ind
	    __mul_128x64_to_128 (C1, C1.w[0], ten2k128[ind - 20]);
	  }
	  x_exp = EXP_MIN;
	}
      }
      if (x_sign) {	// x < 0
	// add 1 ulp (add 1 to the significand)
	C1.w[0]++;
	if (C1.w[0] == 0)
	  C1.w[1]++;
	if (C1.w[1] == 0x0001ed09bead87c0ull && C1.w[0] == 0x378d8e6400000000ull) {	// if  C1 = 10^34
	  C1.w[1] = 0x0000314dc6448d93ull;	// C1 = 10^33
	  C1.w[0] = 0x38c15b0a00000000ull;
	  x_exp = x_exp + EXP_P1;
	}
      } else {	// x > 0
	// subtract 1 ulp (subtract 1 from the significand)
	C1.w[0]--;
	if (C1.w[0] == 0xffffffffffffffffull)
	  C1.w[1]--;
	if (x_exp != 0 && C1.w[1] == 0x0000314dc6448d93ull && C1.w[0] == 0x38c15b09ffffffffull) {	// if  C1 = 10^33 - 1
	  C1.w[1] = 0x0001ed09bead87c0ull;	// C1 = 10^34 - 1
	  C1.w[0] = 0x378d8e63ffffffffull;
	  x_exp = x_exp - EXP_P1;
	}
      }
      // assemble the result
      res.w[1] = x_sign | x_exp | C1.w[1];
      res.w[0] = C1.w[0];
    }	// end -MAXFP <= x <= -MINFP - 1 ulp OR MINFP <= x <= MAXFP - 1 ulp
  }	// end x is not special and is not zero
  BID_RETURN (res);
}

/*****************************************************************************
 *  BID128 nextafter
 ****************************************************************************/

#if DECIMAL_CALL_BY_REFERENCE
void
bid128_nextafter (UINT128 * pres, UINT128 * px,
		  UINT128 *
		  py _EXC_FLAGS_PARAM _EXC_MASKS_PARAM _EXC_INFO_PARAM) 
{
  UINT128 x = *px;
  UINT128 y = *py;
  UINT128 xnswp = *px;
  UINT128 ynswp = *py;
#else
UINT128
bid128_nextafter (UINT128 x,
		  UINT128 y _EXC_FLAGS_PARAM _EXC_MASKS_PARAM
		  _EXC_INFO_PARAM) {
  UINT128 xnswp = x;
  UINT128 ynswp = y;
#endif

  UINT128 res;
  UINT128 tmp1, tmp2, tmp3;
  FPSC tmp_fpsf = 0;		// dummy fpsf for calls to comparison functions
  int res1, res2;
  UINT64 x_exp;


  BID_SWAP128 (x);
  BID_SWAP128 (y);
  // check for NaNs
  if (((x.w[1] & MASK_SPECIAL) == MASK_SPECIAL)
      || ((y.w[1] & MASK_SPECIAL) == MASK_SPECIAL)) {
    // x is special or y is special
    if ((x.w[1] & MASK_NAN) == MASK_NAN) {	// x is NAN
      // if x = NaN, then res = Q (x)
      // check first for non-canonical NaN payload
      if (((x.w[1] & 0x00003fffffffffffull) > 0x0000314dc6448d93ull) ||
	  (((x.w[1] & 0x00003fffffffffffull) == 0x0000314dc6448d93ull)
	   && (x.w[0] > 0x38c15b09ffffffffull))) {
	x.w[1] = x.w[1] & 0xffffc00000000000ull;
	x.w[0] = 0x0ull;
      }
      if ((x.w[1] & MASK_SNAN) == MASK_SNAN) {	// x is SNAN
	// set invalid flag
	*pfpsf |= INVALID_EXCEPTION;
	// return quiet (x)
	res.w[1] = x.w[1] & 0xfc003fffffffffffull;	// clear out also G[6]-G[16]
	res.w[0] = x.w[0];
      } else {	// x is QNaN
	// return x
	res.w[1] = x.w[1] & 0xfc003fffffffffffull;	// clear out G[6]-G[16]
	res.w[0] = x.w[0];
	if ((y.w[1] & MASK_SNAN) == MASK_SNAN) {	// y is SNAN
	  // set invalid flag
	  *pfpsf |= INVALID_EXCEPTION;
	}
      }
      BID_RETURN (res)
    } else if ((y.w[1] & MASK_NAN) == MASK_NAN) {	// y is NAN
      // if x = NaN, then res = Q (x)
      // check first for non-canonical NaN payload
      if (((y.w[1] & 0x00003fffffffffffull) > 0x0000314dc6448d93ull) ||
	  (((y.w[1] & 0x00003fffffffffffull) == 0x0000314dc6448d93ull)
	   && (y.w[0] > 0x38c15b09ffffffffull))) {
	y.w[1] = y.w[1] & 0xffffc00000000000ull;
	y.w[0] = 0x0ull;
      }
      if ((y.w[1] & MASK_SNAN) == MASK_SNAN) {	// y is SNAN
	// set invalid flag
	*pfpsf |= INVALID_EXCEPTION;
	// return quiet (x)
	res.w[1] = y.w[1] & 0xfc003fffffffffffull;	// clear out also G[6]-G[16]
	res.w[0] = y.w[0];
      } else {	// x is QNaN
	// return x
	res.w[1] = y.w[1] & 0xfc003fffffffffffull;	// clear out G[6]-G[16]
	res.w[0] = y.w[0];
      }
      BID_RETURN (res)
    } else {	// at least one is infinity
      if ((x.w[1] & MASK_ANY_INF) == MASK_INF) {	// x = inf
	x.w[1] = x.w[1] & (MASK_SIGN | MASK_INF);
	x.w[0] = 0x0ull;
      }
      if ((y.w[1] & MASK_ANY_INF) == MASK_INF) {	// y = inf
	y.w[1] = y.w[1] & (MASK_SIGN | MASK_INF);
	y.w[0] = 0x0ull;
      }
    }
  }
  // neither x nor y is NaN

  // if not infinity, check for non-canonical values x (treated as zero)
  if ((x.w[1] & MASK_ANY_INF) != MASK_INF) {	// x != inf
    if ((x.w[1] & 0x6000000000000000ull) == 0x6000000000000000ull) {	// G0_G1=11
      // non-canonical
      x_exp = (x.w[1] << 2) & MASK_EXP;	// biased and shifted left 49 bits
      x.w[1] = (x.w[1] & MASK_SIGN) | x_exp;
      x.w[0] = 0x0ull;
    } else {	// G0_G1 != 11
      x_exp = x.w[1] & MASK_EXP;	// biased and shifted left 49 bits
      if ((x.w[1] & MASK_COEFF) > 0x0001ed09bead87c0ull ||
	  ((x.w[1] & MASK_COEFF) == 0x0001ed09bead87c0ull
	   && x.w[0] > 0x378d8e63ffffffffull)) {
	// x is non-canonical if coefficient is larger than 10^34 -1
	x.w[1] = (x.w[1] & MASK_SIGN) | x_exp;
	x.w[0] = 0x0ull;
      } else {	// canonical
	;
      }
    }
  }
  // no need to check for non-canonical y

  // neither x nor y is NaN
  tmp_fpsf = *pfpsf;	// save fpsf
#if DECIMAL_CALL_BY_REFERENCE
  bid128_quiet_equal (&res1, &xnswp,
		      &ynswp _EXC_FLAGS_ARG _EXC_MASKS_ARG
		      _EXC_INFO_ARG);
  bid128_quiet_greater (&res2, &xnswp,
			&ynswp _EXC_FLAGS_ARG _EXC_MASKS_ARG
			_EXC_INFO_ARG);
#else
  res1 =
    bid128_quiet_equal (xnswp,
			ynswp _EXC_FLAGS_ARG _EXC_MASKS_ARG
			_EXC_INFO_ARG);
  res2 =
    bid128_quiet_greater (xnswp,
			  ynswp _EXC_FLAGS_ARG _EXC_MASKS_ARG
			  _EXC_INFO_ARG);
#endif
  *pfpsf = tmp_fpsf;	// restore fpsf

  if (res1) {	// x = y
    // return x with the sign of y
    res.w[1] =
      (x.w[1] & 0x7fffffffffffffffull) | (y.
					  w[1] & 0x8000000000000000ull);
    res.w[0] = x.w[0];
  } else if (res2) {	// x > y
#if DECIMAL_CALL_BY_REFERENCE
    bid128_nextdown (&res,
		     &xnswp _EXC_FLAGS_ARG _EXC_MASKS_ARG
		     _EXC_INFO_ARG);
#else
    res =
      bid128_nextdown (xnswp _EXC_FLAGS_ARG _EXC_MASKS_ARG
		       _EXC_INFO_ARG);
#endif
    BID_SWAP128 (res);
  } else {	// x < y
#if DECIMAL_CALL_BY_REFERENCE
    bid128_nextup (&res,
		   &xnswp _EXC_FLAGS_ARG _EXC_MASKS_ARG _EXC_INFO_ARG);
#else
    res =
      bid128_nextup (xnswp _EXC_FLAGS_ARG _EXC_MASKS_ARG _EXC_INFO_ARG);
#endif
    BID_SWAP128 (res);
  }
  // if the operand x is finite but the result is infinite, signal 
  // overflow and inexact
  if (((x.w[1] & MASK_SPECIAL) != MASK_SPECIAL)
      && ((res.w[1] & MASK_SPECIAL) == MASK_SPECIAL)) {
    // set the inexact flag
    *pfpsf |= INEXACT_EXCEPTION;
    // set the overflow flag
    *pfpsf |= OVERFLOW_EXCEPTION;
  }
  // if the result is in (-10^emin, 10^emin), and is different from the
  // operand x, signal underflow and inexact
  tmp1.w[HIGH_128W] = 0x0000314dc6448d93ull;
  tmp1.w[LOW_128W] = 0x38c15b0a00000000ull;	// +100...0[34] * 10^emin
  tmp2.w[HIGH_128W] = res.w[1] & 0x7fffffffffffffffull;
  tmp2.w[LOW_128W] = res.w[0];
  tmp3.w[HIGH_128W] = res.w[1];
  tmp3.w[LOW_128W] = res.w[0];
  tmp_fpsf = *pfpsf;	// save fpsf
#if DECIMAL_CALL_BY_REFERENCE
  bid128_quiet_greater (&res1, &tmp1,
			&tmp2 _EXC_FLAGS_ARG _EXC_MASKS_ARG
			_EXC_INFO_ARG);
  bid128_quiet_not_equal (&res2, &xnswp,
			  &tmp3 _EXC_FLAGS_ARG _EXC_MASKS_ARG
			  _EXC_INFO_ARG);
#else
  res1 =
    bid128_quiet_greater (tmp1,
			  tmp2 _EXC_FLAGS_ARG _EXC_MASKS_ARG
			  _EXC_INFO_ARG);
  res2 =
    bid128_quiet_not_equal (xnswp,
			    tmp3 _EXC_FLAGS_ARG _EXC_MASKS_ARG
			    _EXC_INFO_ARG);
#endif
  *pfpsf = tmp_fpsf;	// restore fpsf
  if (res1 && res2) {
    // set the inexact flag 
    *pfpsf |= INEXACT_EXCEPTION;
    // set the underflow flag 
    *pfpsf |= UNDERFLOW_EXCEPTION;
  }
  BID_RETURN (res);
}