summaryrefslogtreecommitdiff
path: root/fpu/softfloat-specialize.h
blob: a4cbdad4521444ceaad2ef4c1e067f3df4eafad8 (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
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
/*
 * QEMU float support
 *
 * The code in this source file is derived from release 2a of the SoftFloat
 * IEC/IEEE Floating-point Arithmetic Package. Those parts of the code (and
 * some later contributions) are provided under that license, as detailed below.
 * It has subsequently been modified by contributors to the QEMU Project,
 * so some portions are provided under:
 *  the SoftFloat-2a license
 *  the BSD license
 *  GPL-v2-or-later
 *
 * Any future contributions to this file after December 1st 2014 will be
 * taken to be licensed under the Softfloat-2a license unless specifically
 * indicated otherwise.
 */

/*
===============================================================================
This C source fragment is part of the SoftFloat IEC/IEEE Floating-point
Arithmetic Package, Release 2a.

Written by John R. Hauser.  This work was made possible in part by the
International Computer Science Institute, located at Suite 600, 1947 Center
Street, Berkeley, California 94704.  Funding was partially provided by the
National Science Foundation under grant MIP-9311980.  The original version
of this code was written as part of a project to build a fixed-point vector
processor in collaboration with the University of California at Berkeley,
overseen by Profs. Nelson Morgan and John Wawrzynek.  More information
is available through the Web page `http://HTTP.CS.Berkeley.EDU/~jhauser/
arithmetic/SoftFloat.html'.

THIS SOFTWARE IS DISTRIBUTED AS IS, FOR FREE.  Although reasonable effort
has been made to avoid it, THIS SOFTWARE MAY CONTAIN FAULTS THAT WILL AT
TIMES RESULT IN INCORRECT BEHAVIOR.  USE OF THIS SOFTWARE IS RESTRICTED TO
PERSONS AND ORGANIZATIONS WHO CAN AND WILL TAKE FULL RESPONSIBILITY FOR ANY
AND ALL LOSSES, COSTS, OR OTHER PROBLEMS ARISING FROM ITS USE.

Derivative works are acceptable, even for commercial purposes, so long as
(1) they include prominent notice that the work is derivative, and (2) they
include prominent notice akin to these four paragraphs for those parts of
this code that are retained.

===============================================================================
*/

/* BSD licensing:
 * Copyright (c) 2006, Fabrice Bellard
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the copyright holder nor the names of its contributors
 * may be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

/* Portions of this work are licensed under the terms of the GNU GPL,
 * version 2 or later. See the COPYING file in the top-level directory.
 */

/* Does the target distinguish signaling NaNs from non-signaling NaNs
 * by setting the most significant bit of the mantissa for a signaling NaN?
 * (The more common choice is to have it be zero for SNaN and one for QNaN.)
 */
#if defined(TARGET_MIPS) || defined(TARGET_SH4) || defined(TARGET_UNICORE32)
#define SNAN_BIT_IS_ONE 1
#else
#define SNAN_BIT_IS_ONE 0
#endif

#if defined(TARGET_XTENSA)
/* Define for architectures which deviate from IEEE in not supporting
 * signaling NaNs (so all NaNs are treated as quiet).
 */
#define NO_SIGNALING_NANS 1
#endif

/*----------------------------------------------------------------------------
| The pattern for a default generated half-precision NaN.
*----------------------------------------------------------------------------*/
#if defined(TARGET_ARM)
const float16 float16_default_nan = const_float16(0x7E00);
#elif SNAN_BIT_IS_ONE
const float16 float16_default_nan = const_float16(0x7DFF);
#else
const float16 float16_default_nan = const_float16(0xFE00);
#endif

/*----------------------------------------------------------------------------
| The pattern for a default generated single-precision NaN.
*----------------------------------------------------------------------------*/
#if defined(TARGET_SPARC)
const float32 float32_default_nan = const_float32(0x7FFFFFFF);
#elif defined(TARGET_PPC) || defined(TARGET_ARM) || defined(TARGET_ALPHA) || \
      defined(TARGET_XTENSA) || defined(TARGET_S390X) || defined(TARGET_TRICORE)
const float32 float32_default_nan = const_float32(0x7FC00000);
#elif SNAN_BIT_IS_ONE
const float32 float32_default_nan = const_float32(0x7FBFFFFF);
#else
const float32 float32_default_nan = const_float32(0xFFC00000);
#endif

/*----------------------------------------------------------------------------
| The pattern for a default generated double-precision NaN.
*----------------------------------------------------------------------------*/
#if defined(TARGET_SPARC)
const float64 float64_default_nan = const_float64(LIT64( 0x7FFFFFFFFFFFFFFF ));
#elif defined(TARGET_PPC) || defined(TARGET_ARM) || defined(TARGET_ALPHA) || \
      defined(TARGET_S390X)
const float64 float64_default_nan = const_float64(LIT64( 0x7FF8000000000000 ));
#elif SNAN_BIT_IS_ONE
const float64 float64_default_nan = const_float64(LIT64(0x7FF7FFFFFFFFFFFF));
#else
const float64 float64_default_nan = const_float64(LIT64( 0xFFF8000000000000 ));
#endif

/*----------------------------------------------------------------------------
| The pattern for a default generated extended double-precision NaN.
*----------------------------------------------------------------------------*/
#if SNAN_BIT_IS_ONE
#define floatx80_default_nan_high 0x7FFF
#define floatx80_default_nan_low  LIT64(0xBFFFFFFFFFFFFFFF)
#else
#define floatx80_default_nan_high 0xFFFF
#define floatx80_default_nan_low  LIT64( 0xC000000000000000 )
#endif

const floatx80 floatx80_default_nan
    = make_floatx80_init(floatx80_default_nan_high, floatx80_default_nan_low);

/*----------------------------------------------------------------------------
| The pattern for a default generated quadruple-precision NaN.  The `high' and
| `low' values hold the most- and least-significant bits, respectively.
*----------------------------------------------------------------------------*/
#if SNAN_BIT_IS_ONE
#define float128_default_nan_high LIT64(0x7FFF7FFFFFFFFFFF)
#define float128_default_nan_low  LIT64(0xFFFFFFFFFFFFFFFF)
#elif defined(TARGET_S390X)
#define float128_default_nan_high LIT64( 0x7FFF800000000000 )
#define float128_default_nan_low  LIT64( 0x0000000000000000 )
#else
#define float128_default_nan_high LIT64( 0xFFFF800000000000 )
#define float128_default_nan_low  LIT64( 0x0000000000000000 )
#endif

const float128 float128_default_nan
    = make_float128_init(float128_default_nan_high, float128_default_nan_low);

/*----------------------------------------------------------------------------
| Raises the exceptions specified by `flags'.  Floating-point traps can be
| defined here if desired.  It is currently not possible for such a trap
| to substitute a result value.  If traps are not implemented, this routine
| should be simply `float_exception_flags |= flags;'.
*----------------------------------------------------------------------------*/

void float_raise(int8_t flags, float_status *status)
{
    status->float_exception_flags |= flags;
}

/*----------------------------------------------------------------------------
| Internal canonical NaN format.
*----------------------------------------------------------------------------*/
typedef struct {
    flag sign;
    uint64_t high, low;
} commonNaNT;

#ifdef NO_SIGNALING_NANS
int float16_is_quiet_nan(float16 a_)
{
    return float16_is_any_nan(a_);
}

int float16_is_signaling_nan(float16 a_)
{
    return 0;
}
#else
/*----------------------------------------------------------------------------
| Returns 1 if the half-precision floating-point value `a' is a quiet
| NaN; otherwise returns 0.
*----------------------------------------------------------------------------*/

int float16_is_quiet_nan(float16 a_)
{
    uint16_t a = float16_val(a_);
#if SNAN_BIT_IS_ONE
    return (((a >> 9) & 0x3F) == 0x3E) && (a & 0x1FF);
#else
    return ((a & ~0x8000) >= 0x7c80);
#endif
}

/*----------------------------------------------------------------------------
| Returns 1 if the half-precision floating-point value `a' is a signaling
| NaN; otherwise returns 0.
*----------------------------------------------------------------------------*/

int float16_is_signaling_nan(float16 a_)
{
    uint16_t a = float16_val(a_);
#if SNAN_BIT_IS_ONE
    return ((a & ~0x8000) >= 0x7c80);
#else
    return (((a >> 9) & 0x3F) == 0x3E) && (a & 0x1FF);
#endif
}
#endif

/*----------------------------------------------------------------------------
| Returns a quiet NaN if the half-precision floating point value `a' is a
| signaling NaN; otherwise returns `a'.
*----------------------------------------------------------------------------*/
float16 float16_maybe_silence_nan(float16 a_)
{
    if (float16_is_signaling_nan(a_)) {
#if SNAN_BIT_IS_ONE
#  if defined(TARGET_MIPS) || defined(TARGET_SH4) || defined(TARGET_UNICORE32)
        return float16_default_nan;
#  else
#    error Rules for silencing a signaling NaN are target-specific
#  endif
#else
        uint16_t a = float16_val(a_);
        a |= (1 << 9);
        return make_float16(a);
#endif
    }
    return a_;
}

/*----------------------------------------------------------------------------
| Returns the result of converting the half-precision floating-point NaN
| `a' to the canonical NaN format.  If `a' is a signaling NaN, the invalid
| exception is raised.
*----------------------------------------------------------------------------*/

static commonNaNT float16ToCommonNaN(float16 a, float_status *status)
{
    commonNaNT z;

    if (float16_is_signaling_nan(a)) {
        float_raise(float_flag_invalid, status);
    }
    z.sign = float16_val(a) >> 15;
    z.low = 0;
    z.high = ((uint64_t) float16_val(a))<<54;
    return z;
}

/*----------------------------------------------------------------------------
| Returns the result of converting the canonical NaN `a' to the half-
| precision floating-point format.
*----------------------------------------------------------------------------*/

static float16 commonNaNToFloat16(commonNaNT a, float_status *status)
{
    uint16_t mantissa = a.high>>54;

    if (status->default_nan_mode) {
        return float16_default_nan;
    }

    if (mantissa) {
        return make_float16(((((uint16_t) a.sign) << 15)
                             | (0x1F << 10) | mantissa));
    } else {
        return float16_default_nan;
    }
}

#ifdef NO_SIGNALING_NANS
int float32_is_quiet_nan(float32 a_)
{
    return float32_is_any_nan(a_);
}

int float32_is_signaling_nan(float32 a_)
{
    return 0;
}
#else
/*----------------------------------------------------------------------------
| Returns 1 if the single-precision floating-point value `a' is a quiet
| NaN; otherwise returns 0.
*----------------------------------------------------------------------------*/

int float32_is_quiet_nan( float32 a_ )
{
    uint32_t a = float32_val(a_);
#if SNAN_BIT_IS_ONE
    return (((a >> 22) & 0x1ff) == 0x1fe) && (a & 0x003fffff);
#else
    return ((uint32_t)(a << 1) >= 0xff800000);
#endif
}

/*----------------------------------------------------------------------------
| Returns 1 if the single-precision floating-point value `a' is a signaling
| NaN; otherwise returns 0.
*----------------------------------------------------------------------------*/

int float32_is_signaling_nan( float32 a_ )
{
    uint32_t a = float32_val(a_);
#if SNAN_BIT_IS_ONE
    return ((uint32_t)(a << 1) >= 0xff800000);
#else
    return ( ( ( a>>22 ) & 0x1FF ) == 0x1FE ) && ( a & 0x003FFFFF );
#endif
}
#endif

/*----------------------------------------------------------------------------
| Returns a quiet NaN if the single-precision floating point value `a' is a
| signaling NaN; otherwise returns `a'.
*----------------------------------------------------------------------------*/

float32 float32_maybe_silence_nan( float32 a_ )
{
    if (float32_is_signaling_nan(a_)) {
#if SNAN_BIT_IS_ONE
#  if defined(TARGET_MIPS) || defined(TARGET_SH4) || defined(TARGET_UNICORE32)
        return float32_default_nan;
#  else
#    error Rules for silencing a signaling NaN are target-specific
#  endif
#else
        uint32_t a = float32_val(a_);
        a |= (1 << 22);
        return make_float32(a);
#endif
    }
    return a_;
}

/*----------------------------------------------------------------------------
| Returns the result of converting the single-precision floating-point NaN
| `a' to the canonical NaN format.  If `a' is a signaling NaN, the invalid
| exception is raised.
*----------------------------------------------------------------------------*/

static commonNaNT float32ToCommonNaN(float32 a, float_status *status)
{
    commonNaNT z;

    if (float32_is_signaling_nan(a)) {
        float_raise(float_flag_invalid, status);
    }
    z.sign = float32_val(a)>>31;
    z.low = 0;
    z.high = ( (uint64_t) float32_val(a) )<<41;
    return z;
}

/*----------------------------------------------------------------------------
| Returns the result of converting the canonical NaN `a' to the single-
| precision floating-point format.
*----------------------------------------------------------------------------*/

static float32 commonNaNToFloat32(commonNaNT a, float_status *status)
{
    uint32_t mantissa = a.high>>41;

    if (status->default_nan_mode) {
        return float32_default_nan;
    }

    if ( mantissa )
        return make_float32(
            ( ( (uint32_t) a.sign )<<31 ) | 0x7F800000 | ( a.high>>41 ) );
    else
        return float32_default_nan;
}

/*----------------------------------------------------------------------------
| Select which NaN to propagate for a two-input operation.
| IEEE754 doesn't specify all the details of this, so the
| algorithm is target-specific.
| The routine is passed various bits of information about the
| two NaNs and should return 0 to select NaN a and 1 for NaN b.
| Note that signalling NaNs are always squashed to quiet NaNs
| by the caller, by calling floatXX_maybe_silence_nan() before
| returning them.
|
| aIsLargerSignificand is only valid if both a and b are NaNs
| of some kind, and is true if a has the larger significand,
| or if both a and b have the same significand but a is
| positive but b is negative. It is only needed for the x87
| tie-break rule.
*----------------------------------------------------------------------------*/

#if defined(TARGET_ARM)
static int pickNaN(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag bIsSNaN,
                    flag aIsLargerSignificand)
{
    /* ARM mandated NaN propagation rules: take the first of:
     *  1. A if it is signaling
     *  2. B if it is signaling
     *  3. A (quiet)
     *  4. B (quiet)
     * A signaling NaN is always quietened before returning it.
     */
    if (aIsSNaN) {
        return 0;
    } else if (bIsSNaN) {
        return 1;
    } else if (aIsQNaN) {
        return 0;
    } else {
        return 1;
    }
}
#elif defined(TARGET_MIPS)
static int pickNaN(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag bIsSNaN,
                    flag aIsLargerSignificand)
{
    /* According to MIPS specifications, if one of the two operands is
     * a sNaN, a new qNaN has to be generated. This is done in
     * floatXX_maybe_silence_nan(). For qNaN inputs the specifications
     * says: "When possible, this QNaN result is one of the operand QNaN
     * values." In practice it seems that most implementations choose
     * the first operand if both operands are qNaN. In short this gives
     * the following rules:
     *  1. A if it is signaling
     *  2. B if it is signaling
     *  3. A (quiet)
     *  4. B (quiet)
     * A signaling NaN is always silenced before returning it.
     */
    if (aIsSNaN) {
        return 0;
    } else if (bIsSNaN) {
        return 1;
    } else if (aIsQNaN) {
        return 0;
    } else {
        return 1;
    }
}
#elif defined(TARGET_PPC) || defined(TARGET_XTENSA)
static int pickNaN(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag bIsSNaN,
                   flag aIsLargerSignificand)
{
    /* PowerPC propagation rules:
     *  1. A if it sNaN or qNaN
     *  2. B if it sNaN or qNaN
     * A signaling NaN is always silenced before returning it.
     */
    if (aIsSNaN || aIsQNaN) {
        return 0;
    } else {
        return 1;
    }
}
#else
static int pickNaN(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag bIsSNaN,
                    flag aIsLargerSignificand)
{
    /* This implements x87 NaN propagation rules:
     * SNaN + QNaN => return the QNaN
     * two SNaNs => return the one with the larger significand, silenced
     * two QNaNs => return the one with the larger significand
     * SNaN and a non-NaN => return the SNaN, silenced
     * QNaN and a non-NaN => return the QNaN
     *
     * If we get down to comparing significands and they are the same,
     * return the NaN with the positive sign bit (if any).
     */
    if (aIsSNaN) {
        if (bIsSNaN) {
            return aIsLargerSignificand ? 0 : 1;
        }
        return bIsQNaN ? 1 : 0;
    }
    else if (aIsQNaN) {
        if (bIsSNaN || !bIsQNaN)
            return 0;
        else {
            return aIsLargerSignificand ? 0 : 1;
        }
    } else {
        return 1;
    }
}
#endif

/*----------------------------------------------------------------------------
| Select which NaN to propagate for a three-input operation.
| For the moment we assume that no CPU needs the 'larger significand'
| information.
| Return values : 0 : a; 1 : b; 2 : c; 3 : default-NaN
*----------------------------------------------------------------------------*/
#if defined(TARGET_ARM)
static int pickNaNMulAdd(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag bIsSNaN,
                         flag cIsQNaN, flag cIsSNaN, flag infzero,
                         float_status *status)
{
    /* For ARM, the (inf,zero,qnan) case sets InvalidOp and returns
     * the default NaN
     */
    if (infzero && cIsQNaN) {
        float_raise(float_flag_invalid, status);
        return 3;
    }

    /* This looks different from the ARM ARM pseudocode, because the ARM ARM
     * puts the operands to a fused mac operation (a*b)+c in the order c,a,b.
     */
    if (cIsSNaN) {
        return 2;
    } else if (aIsSNaN) {
        return 0;
    } else if (bIsSNaN) {
        return 1;
    } else if (cIsQNaN) {
        return 2;
    } else if (aIsQNaN) {
        return 0;
    } else {
        return 1;
    }
}
#elif defined(TARGET_MIPS)
static int pickNaNMulAdd(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag bIsSNaN,
                         flag cIsQNaN, flag cIsSNaN, flag infzero,
                         float_status *status)
{
    /* For MIPS, the (inf,zero,qnan) case sets InvalidOp and returns
     * the default NaN
     */
    if (infzero) {
        float_raise(float_flag_invalid, status);
        return 3;
    }

    /* Prefer sNaN over qNaN, in the a, b, c order. */
    if (aIsSNaN) {
        return 0;
    } else if (bIsSNaN) {
        return 1;
    } else if (cIsSNaN) {
        return 2;
    } else if (aIsQNaN) {
        return 0;
    } else if (bIsQNaN) {
        return 1;
    } else {
        return 2;
    }
}
#elif defined(TARGET_PPC)
static int pickNaNMulAdd(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag bIsSNaN,
                         flag cIsQNaN, flag cIsSNaN, flag infzero,
                         float_status *status)
{
    /* For PPC, the (inf,zero,qnan) case sets InvalidOp, but we prefer
     * to return an input NaN if we have one (ie c) rather than generating
     * a default NaN
     */
    if (infzero) {
        float_raise(float_flag_invalid, status);
        return 2;
    }

    /* If fRA is a NaN return it; otherwise if fRB is a NaN return it;
     * otherwise return fRC. Note that muladd on PPC is (fRA * fRC) + frB
     */
    if (aIsSNaN || aIsQNaN) {
        return 0;
    } else if (cIsSNaN || cIsQNaN) {
        return 2;
    } else {
        return 1;
    }
}
#else
/* A default implementation: prefer a to b to c.
 * This is unlikely to actually match any real implementation.
 */
static int pickNaNMulAdd(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag bIsSNaN,
                         flag cIsQNaN, flag cIsSNaN, flag infzero,
                         float_status *status)
{
    if (aIsSNaN || aIsQNaN) {
        return 0;
    } else if (bIsSNaN || bIsQNaN) {
        return 1;
    } else {
        return 2;
    }
}
#endif

/*----------------------------------------------------------------------------
| Takes two single-precision floating-point values `a' and `b', one of which
| is a NaN, and returns the appropriate NaN result.  If either `a' or `b' is a
| signaling NaN, the invalid exception is raised.
*----------------------------------------------------------------------------*/

static float32 propagateFloat32NaN(float32 a, float32 b, float_status *status)
{
    flag aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN;
    flag aIsLargerSignificand;
    uint32_t av, bv;

    aIsQuietNaN = float32_is_quiet_nan( a );
    aIsSignalingNaN = float32_is_signaling_nan( a );
    bIsQuietNaN = float32_is_quiet_nan( b );
    bIsSignalingNaN = float32_is_signaling_nan( b );
    av = float32_val(a);
    bv = float32_val(b);

    if (aIsSignalingNaN | bIsSignalingNaN) {
        float_raise(float_flag_invalid, status);
    }

    if (status->default_nan_mode)
        return float32_default_nan;

    if ((uint32_t)(av<<1) < (uint32_t)(bv<<1)) {
        aIsLargerSignificand = 0;
    } else if ((uint32_t)(bv<<1) < (uint32_t)(av<<1)) {
        aIsLargerSignificand = 1;
    } else {
        aIsLargerSignificand = (av < bv) ? 1 : 0;
    }

    if (pickNaN(aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN,
                aIsLargerSignificand)) {
        return float32_maybe_silence_nan(b);
    } else {
        return float32_maybe_silence_nan(a);
    }
}

/*----------------------------------------------------------------------------
| Takes three single-precision floating-point values `a', `b' and `c', one of
| which is a NaN, and returns the appropriate NaN result.  If any of  `a',
| `b' or `c' is a signaling NaN, the invalid exception is raised.
| The input infzero indicates whether a*b was 0*inf or inf*0 (in which case
| obviously c is a NaN, and whether to propagate c or some other NaN is
| implementation defined).
*----------------------------------------------------------------------------*/

static float32 propagateFloat32MulAddNaN(float32 a, float32 b,
                                         float32 c, flag infzero,
                                         float_status *status)
{
    flag aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN,
        cIsQuietNaN, cIsSignalingNaN;
    int which;

    aIsQuietNaN = float32_is_quiet_nan(a);
    aIsSignalingNaN = float32_is_signaling_nan(a);
    bIsQuietNaN = float32_is_quiet_nan(b);
    bIsSignalingNaN = float32_is_signaling_nan(b);
    cIsQuietNaN = float32_is_quiet_nan(c);
    cIsSignalingNaN = float32_is_signaling_nan(c);

    if (aIsSignalingNaN | bIsSignalingNaN | cIsSignalingNaN) {
        float_raise(float_flag_invalid, status);
    }

    which = pickNaNMulAdd(aIsQuietNaN, aIsSignalingNaN,
                          bIsQuietNaN, bIsSignalingNaN,
                          cIsQuietNaN, cIsSignalingNaN, infzero, status);

    if (status->default_nan_mode) {
        /* Note that this check is after pickNaNMulAdd so that function
         * has an opportunity to set the Invalid flag.
         */
        return float32_default_nan;
    }

    switch (which) {
    case 0:
        return float32_maybe_silence_nan(a);
    case 1:
        return float32_maybe_silence_nan(b);
    case 2:
        return float32_maybe_silence_nan(c);
    case 3:
    default:
        return float32_default_nan;
    }
}

#ifdef NO_SIGNALING_NANS
int float64_is_quiet_nan(float64 a_)
{
    return float64_is_any_nan(a_);
}

int float64_is_signaling_nan(float64 a_)
{
    return 0;
}
#else
/*----------------------------------------------------------------------------
| Returns 1 if the double-precision floating-point value `a' is a quiet
| NaN; otherwise returns 0.
*----------------------------------------------------------------------------*/

int float64_is_quiet_nan( float64 a_ )
{
    uint64_t a = float64_val(a_);
#if SNAN_BIT_IS_ONE
    return (((a >> 51) & 0xfff) == 0xffe)
           && (a & 0x0007ffffffffffffULL);
#else
    return ((a << 1) >= 0xfff0000000000000ULL);
#endif
}

/*----------------------------------------------------------------------------
| Returns 1 if the double-precision floating-point value `a' is a signaling
| NaN; otherwise returns 0.
*----------------------------------------------------------------------------*/

int float64_is_signaling_nan( float64 a_ )
{
    uint64_t a = float64_val(a_);
#if SNAN_BIT_IS_ONE
    return ((a << 1) >= 0xfff0000000000000ULL);
#else
    return
           ( ( ( a>>51 ) & 0xFFF ) == 0xFFE )
        && ( a & LIT64( 0x0007FFFFFFFFFFFF ) );
#endif
}
#endif

/*----------------------------------------------------------------------------
| Returns a quiet NaN if the double-precision floating point value `a' is a
| signaling NaN; otherwise returns `a'.
*----------------------------------------------------------------------------*/

float64 float64_maybe_silence_nan( float64 a_ )
{
    if (float64_is_signaling_nan(a_)) {
#if SNAN_BIT_IS_ONE
#  if defined(TARGET_MIPS) || defined(TARGET_SH4) || defined(TARGET_UNICORE32)
        return float64_default_nan;
#  else
#    error Rules for silencing a signaling NaN are target-specific
#  endif
#else
        uint64_t a = float64_val(a_);
        a |= LIT64( 0x0008000000000000 );
        return make_float64(a);
#endif
    }
    return a_;
}

/*----------------------------------------------------------------------------
| Returns the result of converting the double-precision floating-point NaN
| `a' to the canonical NaN format.  If `a' is a signaling NaN, the invalid
| exception is raised.
*----------------------------------------------------------------------------*/

static commonNaNT float64ToCommonNaN(float64 a, float_status *status)
{
    commonNaNT z;

    if (float64_is_signaling_nan(a)) {
        float_raise(float_flag_invalid, status);
    }
    z.sign = float64_val(a)>>63;
    z.low = 0;
    z.high = float64_val(a)<<12;
    return z;
}

/*----------------------------------------------------------------------------
| Returns the result of converting the canonical NaN `a' to the double-
| precision floating-point format.
*----------------------------------------------------------------------------*/

static float64 commonNaNToFloat64(commonNaNT a, float_status *status)
{
    uint64_t mantissa = a.high>>12;

    if (status->default_nan_mode) {
        return float64_default_nan;
    }

    if ( mantissa )
        return make_float64(
              ( ( (uint64_t) a.sign )<<63 )
            | LIT64( 0x7FF0000000000000 )
            | ( a.high>>12 ));
    else
        return float64_default_nan;
}

/*----------------------------------------------------------------------------
| Takes two double-precision floating-point values `a' and `b', one of which
| is a NaN, and returns the appropriate NaN result.  If either `a' or `b' is a
| signaling NaN, the invalid exception is raised.
*----------------------------------------------------------------------------*/

static float64 propagateFloat64NaN(float64 a, float64 b, float_status *status)
{
    flag aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN;
    flag aIsLargerSignificand;
    uint64_t av, bv;

    aIsQuietNaN = float64_is_quiet_nan( a );
    aIsSignalingNaN = float64_is_signaling_nan( a );
    bIsQuietNaN = float64_is_quiet_nan( b );
    bIsSignalingNaN = float64_is_signaling_nan( b );
    av = float64_val(a);
    bv = float64_val(b);

    if (aIsSignalingNaN | bIsSignalingNaN) {
        float_raise(float_flag_invalid, status);
    }

    if (status->default_nan_mode)
        return float64_default_nan;

    if ((uint64_t)(av<<1) < (uint64_t)(bv<<1)) {
        aIsLargerSignificand = 0;
    } else if ((uint64_t)(bv<<1) < (uint64_t)(av<<1)) {
        aIsLargerSignificand = 1;
    } else {
        aIsLargerSignificand = (av < bv) ? 1 : 0;
    }

    if (pickNaN(aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN,
                aIsLargerSignificand)) {
        return float64_maybe_silence_nan(b);
    } else {
        return float64_maybe_silence_nan(a);
    }
}

/*----------------------------------------------------------------------------
| Takes three double-precision floating-point values `a', `b' and `c', one of
| which is a NaN, and returns the appropriate NaN result.  If any of  `a',
| `b' or `c' is a signaling NaN, the invalid exception is raised.
| The input infzero indicates whether a*b was 0*inf or inf*0 (in which case
| obviously c is a NaN, and whether to propagate c or some other NaN is
| implementation defined).
*----------------------------------------------------------------------------*/

static float64 propagateFloat64MulAddNaN(float64 a, float64 b,
                                         float64 c, flag infzero,
                                         float_status *status)
{
    flag aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN,
        cIsQuietNaN, cIsSignalingNaN;
    int which;

    aIsQuietNaN = float64_is_quiet_nan(a);
    aIsSignalingNaN = float64_is_signaling_nan(a);
    bIsQuietNaN = float64_is_quiet_nan(b);
    bIsSignalingNaN = float64_is_signaling_nan(b);
    cIsQuietNaN = float64_is_quiet_nan(c);
    cIsSignalingNaN = float64_is_signaling_nan(c);

    if (aIsSignalingNaN | bIsSignalingNaN | cIsSignalingNaN) {
        float_raise(float_flag_invalid, status);
    }

    which = pickNaNMulAdd(aIsQuietNaN, aIsSignalingNaN,
                          bIsQuietNaN, bIsSignalingNaN,
                          cIsQuietNaN, cIsSignalingNaN, infzero, status);

    if (status->default_nan_mode) {
        /* Note that this check is after pickNaNMulAdd so that function
         * has an opportunity to set the Invalid flag.
         */
        return float64_default_nan;
    }

    switch (which) {
    case 0:
        return float64_maybe_silence_nan(a);
    case 1:
        return float64_maybe_silence_nan(b);
    case 2:
        return float64_maybe_silence_nan(c);
    case 3:
    default:
        return float64_default_nan;
    }
}

#ifdef NO_SIGNALING_NANS
int floatx80_is_quiet_nan(floatx80 a_)
{
    return floatx80_is_any_nan(a_);
}

int floatx80_is_signaling_nan(floatx80 a_)
{
    return 0;
}
#else
/*----------------------------------------------------------------------------
| Returns 1 if the extended double-precision floating-point value `a' is a
| quiet NaN; otherwise returns 0. This slightly differs from the same
| function for other types as floatx80 has an explicit bit.
*----------------------------------------------------------------------------*/

int floatx80_is_quiet_nan( floatx80 a )
{
#if SNAN_BIT_IS_ONE
    uint64_t aLow;

    aLow = a.low & ~0x4000000000000000ULL;
    return ((a.high & 0x7fff) == 0x7fff)
        && (aLow << 1)
        && (a.low == aLow);
#else
    return ( ( a.high & 0x7FFF ) == 0x7FFF )
        && (LIT64( 0x8000000000000000 ) <= ((uint64_t) ( a.low<<1 )));
#endif
}

/*----------------------------------------------------------------------------
| Returns 1 if the extended double-precision floating-point value `a' is a
| signaling NaN; otherwise returns 0. This slightly differs from the same
| function for other types as floatx80 has an explicit bit.
*----------------------------------------------------------------------------*/

int floatx80_is_signaling_nan( floatx80 a )
{
#if SNAN_BIT_IS_ONE
    return ((a.high & 0x7fff) == 0x7fff)
        && ((a.low << 1) >= 0x8000000000000000ULL);
#else
    uint64_t aLow;

    aLow = a.low & ~ LIT64( 0x4000000000000000 );
    return
           ( ( a.high & 0x7FFF ) == 0x7FFF )
        && (uint64_t) ( aLow<<1 )
        && ( a.low == aLow );
#endif
}
#endif

/*----------------------------------------------------------------------------
| Returns a quiet NaN if the extended double-precision floating point value
| `a' is a signaling NaN; otherwise returns `a'.
*----------------------------------------------------------------------------*/

floatx80 floatx80_maybe_silence_nan( floatx80 a )
{
    if (floatx80_is_signaling_nan(a)) {
#if SNAN_BIT_IS_ONE
#  if defined(TARGET_MIPS) || defined(TARGET_SH4) || defined(TARGET_UNICORE32)
        a.low = floatx80_default_nan_low;
        a.high = floatx80_default_nan_high;
#  else
#    error Rules for silencing a signaling NaN are target-specific
#  endif
#else
        a.low |= LIT64( 0xC000000000000000 );
        return a;
#endif
    }
    return a;
}

/*----------------------------------------------------------------------------
| Returns the result of converting the extended double-precision floating-
| point NaN `a' to the canonical NaN format.  If `a' is a signaling NaN, the
| invalid exception is raised.
*----------------------------------------------------------------------------*/

static commonNaNT floatx80ToCommonNaN(floatx80 a, float_status *status)
{
    commonNaNT z;

    if (floatx80_is_signaling_nan(a)) {
        float_raise(float_flag_invalid, status);
    }
    if ( a.low >> 63 ) {
        z.sign = a.high >> 15;
        z.low = 0;
        z.high = a.low << 1;
    } else {
        z.sign = floatx80_default_nan_high >> 15;
        z.low = 0;
        z.high = floatx80_default_nan_low << 1;
    }
    return z;
}

/*----------------------------------------------------------------------------
| Returns the result of converting the canonical NaN `a' to the extended
| double-precision floating-point format.
*----------------------------------------------------------------------------*/

static floatx80 commonNaNToFloatx80(commonNaNT a, float_status *status)
{
    floatx80 z;

    if (status->default_nan_mode) {
        z.low = floatx80_default_nan_low;
        z.high = floatx80_default_nan_high;
        return z;
    }

    if (a.high >> 1) {
        z.low = LIT64( 0x8000000000000000 ) | a.high >> 1;
        z.high = ( ( (uint16_t) a.sign )<<15 ) | 0x7FFF;
    } else {
        z.low = floatx80_default_nan_low;
        z.high = floatx80_default_nan_high;
    }

    return z;
}

/*----------------------------------------------------------------------------
| Takes two extended double-precision floating-point values `a' and `b', one
| of which is a NaN, and returns the appropriate NaN result.  If either `a' or
| `b' is a signaling NaN, the invalid exception is raised.
*----------------------------------------------------------------------------*/

static floatx80 propagateFloatx80NaN(floatx80 a, floatx80 b,
                                     float_status *status)
{
    flag aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN;
    flag aIsLargerSignificand;

    aIsQuietNaN = floatx80_is_quiet_nan( a );
    aIsSignalingNaN = floatx80_is_signaling_nan( a );
    bIsQuietNaN = floatx80_is_quiet_nan( b );
    bIsSignalingNaN = floatx80_is_signaling_nan( b );

    if (aIsSignalingNaN | bIsSignalingNaN) {
        float_raise(float_flag_invalid, status);
    }

    if (status->default_nan_mode) {
        a.low = floatx80_default_nan_low;
        a.high = floatx80_default_nan_high;
        return a;
    }

    if (a.low < b.low) {
        aIsLargerSignificand = 0;
    } else if (b.low < a.low) {
        aIsLargerSignificand = 1;
    } else {
        aIsLargerSignificand = (a.high < b.high) ? 1 : 0;
    }

    if (pickNaN(aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN,
                aIsLargerSignificand)) {
        return floatx80_maybe_silence_nan(b);
    } else {
        return floatx80_maybe_silence_nan(a);
    }
}

#ifdef NO_SIGNALING_NANS
int float128_is_quiet_nan(float128 a_)
{
    return float128_is_any_nan(a_);
}

int float128_is_signaling_nan(float128 a_)
{
    return 0;
}
#else
/*----------------------------------------------------------------------------
| Returns 1 if the quadruple-precision floating-point value `a' is a quiet
| NaN; otherwise returns 0.
*----------------------------------------------------------------------------*/

int float128_is_quiet_nan( float128 a )
{
#if SNAN_BIT_IS_ONE
    return (((a.high >> 47) & 0xffff) == 0xfffe)
        && (a.low || (a.high & 0x00007fffffffffffULL));
#else
    return
        ((a.high << 1) >= 0xffff000000000000ULL)
        && (a.low || (a.high & 0x0000ffffffffffffULL));
#endif
}

/*----------------------------------------------------------------------------
| Returns 1 if the quadruple-precision floating-point value `a' is a
| signaling NaN; otherwise returns 0.
*----------------------------------------------------------------------------*/

int float128_is_signaling_nan( float128 a )
{
#if SNAN_BIT_IS_ONE
    return
        ((a.high << 1) >= 0xffff000000000000ULL)
        && (a.low || (a.high & 0x0000ffffffffffffULL));
#else
    return
           ( ( ( a.high>>47 ) & 0xFFFF ) == 0xFFFE )
        && ( a.low || ( a.high & LIT64( 0x00007FFFFFFFFFFF ) ) );
#endif
}
#endif

/*----------------------------------------------------------------------------
| Returns a quiet NaN if the quadruple-precision floating point value `a' is
| a signaling NaN; otherwise returns `a'.
*----------------------------------------------------------------------------*/

float128 float128_maybe_silence_nan( float128 a )
{
    if (float128_is_signaling_nan(a)) {
#if SNAN_BIT_IS_ONE
#  if defined(TARGET_MIPS) || defined(TARGET_SH4) || defined(TARGET_UNICORE32)
        a.low = float128_default_nan_low;
        a.high = float128_default_nan_high;
#  else
#    error Rules for silencing a signaling NaN are target-specific
#  endif
#else
        a.high |= LIT64( 0x0000800000000000 );
        return a;
#endif
    }
    return a;
}

/*----------------------------------------------------------------------------
| Returns the result of converting the quadruple-precision floating-point NaN
| `a' to the canonical NaN format.  If `a' is a signaling NaN, the invalid
| exception is raised.
*----------------------------------------------------------------------------*/

static commonNaNT float128ToCommonNaN(float128 a, float_status *status)
{
    commonNaNT z;

    if (float128_is_signaling_nan(a)) {
        float_raise(float_flag_invalid, status);
    }
    z.sign = a.high>>63;
    shortShift128Left( a.high, a.low, 16, &z.high, &z.low );
    return z;
}

/*----------------------------------------------------------------------------
| Returns the result of converting the canonical NaN `a' to the quadruple-
| precision floating-point format.
*----------------------------------------------------------------------------*/

static float128 commonNaNToFloat128(commonNaNT a, float_status *status)
{
    float128 z;

    if (status->default_nan_mode) {
        z.low = float128_default_nan_low;
        z.high = float128_default_nan_high;
        return z;
    }

    shift128Right( a.high, a.low, 16, &z.high, &z.low );
    z.high |= ( ( (uint64_t) a.sign )<<63 ) | LIT64( 0x7FFF000000000000 );
    return z;
}

/*----------------------------------------------------------------------------
| Takes two quadruple-precision floating-point values `a' and `b', one of
| which is a NaN, and returns the appropriate NaN result.  If either `a' or
| `b' is a signaling NaN, the invalid exception is raised.
*----------------------------------------------------------------------------*/

static float128 propagateFloat128NaN(float128 a, float128 b,
                                     float_status *status)
{
    flag aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN;
    flag aIsLargerSignificand;

    aIsQuietNaN = float128_is_quiet_nan( a );
    aIsSignalingNaN = float128_is_signaling_nan( a );
    bIsQuietNaN = float128_is_quiet_nan( b );
    bIsSignalingNaN = float128_is_signaling_nan( b );

    if (aIsSignalingNaN | bIsSignalingNaN) {
        float_raise(float_flag_invalid, status);
    }

    if (status->default_nan_mode) {
        a.low = float128_default_nan_low;
        a.high = float128_default_nan_high;
        return a;
    }

    if (lt128(a.high<<1, a.low, b.high<<1, b.low)) {
        aIsLargerSignificand = 0;
    } else if (lt128(b.high<<1, b.low, a.high<<1, a.low)) {
        aIsLargerSignificand = 1;
    } else {
        aIsLargerSignificand = (a.high < b.high) ? 1 : 0;
    }

    if (pickNaN(aIsQuietNaN, aIsSignalingNaN, bIsQuietNaN, bIsSignalingNaN,
                aIsLargerSignificand)) {
        return float128_maybe_silence_nan(b);
    } else {
        return float128_maybe_silence_nan(a);
    }
}