xref: /netbsd-src/external/gpl3/gcc.old/dist/libiberty/floatformat.c (revision aef5eb5f59cdfe8314f1b5f78ac04eb144e44010)
1 /* IEEE floating point support routines, for GDB, the GNU Debugger.
2    Copyright (C) 1991-2019 Free Software Foundation, Inc.
3 
4 This file is part of GDB.
5 
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2 of the License, or
9 (at your option) any later version.
10 
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 GNU General Public License for more details.
15 
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, write to the Free Software
18 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.  */
19 
20 /* This is needed to pick up the NAN macro on some systems.  */
21 #ifndef _GNU_SOURCE
22 #define _GNU_SOURCE
23 #endif
24 
25 #ifdef HAVE_CONFIG_H
26 #include "config.h"
27 #endif
28 
29 #include <math.h>
30 
31 #ifdef HAVE_STRING_H
32 #include <string.h>
33 #endif
34 
35 /* On some platforms, <float.h> provides DBL_QNAN.  */
36 #ifdef STDC_HEADERS
37 #include <float.h>
38 #endif
39 
40 #include "ansidecl.h"
41 #include "libiberty.h"
42 #include "floatformat.h"
43 
44 #ifndef INFINITY
45 #ifdef HUGE_VAL
46 #define INFINITY HUGE_VAL
47 #else
48 #define INFINITY (1.0 / 0.0)
49 #endif
50 #endif
51 
52 #ifndef NAN
53 #ifdef DBL_QNAN
54 #define NAN DBL_QNAN
55 #else
56 #define NAN (0.0 / 0.0)
57 #endif
58 #endif
59 
60 static int mant_bits_set (const struct floatformat *, const unsigned char *);
61 static unsigned long get_field (const unsigned char *,
62                                 enum floatformat_byteorders,
63                                 unsigned int,
64                                 unsigned int,
65                                 unsigned int);
66 static int floatformat_always_valid (const struct floatformat *fmt,
67                                      const void *from);
68 
69 static int
70 floatformat_always_valid (const struct floatformat *fmt ATTRIBUTE_UNUSED,
71                           const void *from ATTRIBUTE_UNUSED)
72 {
73   return 1;
74 }
75 
76 /* The odds that CHAR_BIT will be anything but 8 are low enough that I'm not
77    going to bother with trying to muck around with whether it is defined in
78    a system header, what we do if not, etc.  */
79 #define FLOATFORMAT_CHAR_BIT 8
80 
81 /* floatformats for IEEE half, single and double, big and little endian.  */
82 const struct floatformat floatformat_ieee_half_big =
83 {
84   floatformat_big, 16, 0, 1, 5, 15, 31, 6, 10,
85   floatformat_intbit_no,
86   "floatformat_ieee_half_big",
87   floatformat_always_valid,
88   NULL
89 };
90 const struct floatformat floatformat_ieee_half_little =
91 {
92   floatformat_little, 16, 0, 1, 5, 15, 31, 6, 10,
93   floatformat_intbit_no,
94   "floatformat_ieee_half_little",
95   floatformat_always_valid,
96   NULL
97 };
98 const struct floatformat floatformat_ieee_single_big =
99 {
100   floatformat_big, 32, 0, 1, 8, 127, 255, 9, 23,
101   floatformat_intbit_no,
102   "floatformat_ieee_single_big",
103   floatformat_always_valid,
104   NULL
105 };
106 const struct floatformat floatformat_ieee_single_little =
107 {
108   floatformat_little, 32, 0, 1, 8, 127, 255, 9, 23,
109   floatformat_intbit_no,
110   "floatformat_ieee_single_little",
111   floatformat_always_valid,
112   NULL
113 };
114 const struct floatformat floatformat_ieee_double_big =
115 {
116   floatformat_big, 64, 0, 1, 11, 1023, 2047, 12, 52,
117   floatformat_intbit_no,
118   "floatformat_ieee_double_big",
119   floatformat_always_valid,
120   NULL
121 };
122 const struct floatformat floatformat_ieee_double_little =
123 {
124   floatformat_little, 64, 0, 1, 11, 1023, 2047, 12, 52,
125   floatformat_intbit_no,
126   "floatformat_ieee_double_little",
127   floatformat_always_valid,
128   NULL
129 };
130 
131 /* floatformat for IEEE double, little endian byte order, with big endian word
132    ordering, as on the ARM.  */
133 
134 const struct floatformat floatformat_ieee_double_littlebyte_bigword =
135 {
136   floatformat_littlebyte_bigword, 64, 0, 1, 11, 1023, 2047, 12, 52,
137   floatformat_intbit_no,
138   "floatformat_ieee_double_littlebyte_bigword",
139   floatformat_always_valid,
140   NULL
141 };
142 
143 /* floatformat for VAX.  Not quite IEEE, but close enough.  */
144 
145 const struct floatformat floatformat_vax_f =
146 {
147   floatformat_vax, 32, 0, 1, 8, 129, 0, 9, 23,
148   floatformat_intbit_no,
149   "floatformat_vax_f",
150   floatformat_always_valid,
151   NULL
152 };
153 const struct floatformat floatformat_vax_d =
154 {
155   floatformat_vax, 64, 0, 1, 8, 129, 0, 9, 55,
156   floatformat_intbit_no,
157   "floatformat_vax_d",
158   floatformat_always_valid,
159   NULL
160 };
161 const struct floatformat floatformat_vax_g =
162 {
163   floatformat_vax, 64, 0, 1, 11, 1025, 0, 12, 52,
164   floatformat_intbit_no,
165   "floatformat_vax_g",
166   floatformat_always_valid,
167   NULL
168 };
169 
170 static int floatformat_i387_ext_is_valid (const struct floatformat *fmt,
171 					  const void *from);
172 
173 static int
174 floatformat_i387_ext_is_valid (const struct floatformat *fmt, const void *from)
175 {
176   /* In the i387 double-extended format, if the exponent is all ones,
177      then the integer bit must be set.  If the exponent is neither 0
178      nor ~0, the intbit must also be set.  Only if the exponent is
179      zero can it be zero, and then it must be zero.  */
180   unsigned long exponent, int_bit;
181   const unsigned char *ufrom = (const unsigned char *) from;
182 
183   exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize,
184 			fmt->exp_start, fmt->exp_len);
185   int_bit = get_field (ufrom, fmt->byteorder, fmt->totalsize,
186 		       fmt->man_start, 1);
187 
188   if ((exponent == 0) != (int_bit == 0))
189     return 0;
190   else
191     return 1;
192 }
193 
194 const struct floatformat floatformat_i387_ext =
195 {
196   floatformat_little, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,
197   floatformat_intbit_yes,
198   "floatformat_i387_ext",
199   floatformat_i387_ext_is_valid,
200   NULL
201 };
202 const struct floatformat floatformat_m68881_ext =
203 {
204   /* Note that the bits from 16 to 31 are unused.  */
205   floatformat_big, 96, 0, 1, 15, 0x3fff, 0x7fff, 32, 64,
206   floatformat_intbit_yes,
207   "floatformat_m68881_ext",
208   floatformat_always_valid,
209   NULL
210 };
211 const struct floatformat floatformat_i960_ext =
212 {
213   /* Note that the bits from 0 to 15 are unused.  */
214   floatformat_little, 96, 16, 17, 15, 0x3fff, 0x7fff, 32, 64,
215   floatformat_intbit_yes,
216   "floatformat_i960_ext",
217   floatformat_always_valid,
218   NULL
219 };
220 const struct floatformat floatformat_m88110_ext =
221 {
222   floatformat_big, 80, 0, 1, 15, 0x3fff, 0x7fff, 16, 64,
223   floatformat_intbit_yes,
224   "floatformat_m88110_ext",
225   floatformat_always_valid,
226   NULL
227 };
228 const struct floatformat floatformat_m88110_harris_ext =
229 {
230   /* Harris uses raw format 128 bytes long, but the number is just an ieee
231      double, and the last 64 bits are wasted. */
232   floatformat_big,128, 0, 1, 11,  0x3ff,  0x7ff, 12, 52,
233   floatformat_intbit_no,
234   "floatformat_m88110_ext_harris",
235   floatformat_always_valid,
236   NULL
237 };
238 const struct floatformat floatformat_arm_ext_big =
239 {
240   /* Bits 1 to 16 are unused.  */
241   floatformat_big, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64,
242   floatformat_intbit_yes,
243   "floatformat_arm_ext_big",
244   floatformat_always_valid,
245   NULL
246 };
247 const struct floatformat floatformat_arm_ext_littlebyte_bigword =
248 {
249   /* Bits 1 to 16 are unused.  */
250   floatformat_littlebyte_bigword, 96, 0, 17, 15, 0x3fff, 0x7fff, 32, 64,
251   floatformat_intbit_yes,
252   "floatformat_arm_ext_littlebyte_bigword",
253   floatformat_always_valid,
254   NULL
255 };
256 const struct floatformat floatformat_ia64_spill_big =
257 {
258   floatformat_big, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64,
259   floatformat_intbit_yes,
260   "floatformat_ia64_spill_big",
261   floatformat_always_valid,
262   NULL
263 };
264 const struct floatformat floatformat_ia64_spill_little =
265 {
266   floatformat_little, 128, 0, 1, 17, 65535, 0x1ffff, 18, 64,
267   floatformat_intbit_yes,
268   "floatformat_ia64_spill_little",
269   floatformat_always_valid,
270   NULL
271 };
272 const struct floatformat floatformat_ia64_quad_big =
273 {
274   floatformat_big, 128, 0, 1, 15, 16383, 0x7fff, 16, 112,
275   floatformat_intbit_no,
276   "floatformat_ia64_quad_big",
277   floatformat_always_valid,
278   NULL
279 };
280 const struct floatformat floatformat_ia64_quad_little =
281 {
282   floatformat_little, 128, 0, 1, 15, 16383, 0x7fff, 16, 112,
283   floatformat_intbit_no,
284   "floatformat_ia64_quad_little",
285   floatformat_always_valid,
286   NULL
287 };
288 
289 static int
290 floatformat_ibm_long_double_is_valid (const struct floatformat *fmt,
291 				      const void *from)
292 {
293   const unsigned char *ufrom = (const unsigned char *) from;
294   const struct floatformat *hfmt = fmt->split_half;
295   long top_exp, bot_exp;
296   int top_nan = 0;
297 
298   top_exp = get_field (ufrom, hfmt->byteorder, hfmt->totalsize,
299 		       hfmt->exp_start, hfmt->exp_len);
300   bot_exp = get_field (ufrom + 8, hfmt->byteorder, hfmt->totalsize,
301 		       hfmt->exp_start, hfmt->exp_len);
302 
303   if ((unsigned long) top_exp == hfmt->exp_nan)
304     top_nan = mant_bits_set (hfmt, ufrom);
305 
306   /* A NaN is valid with any low part.  */
307   if (top_nan)
308     return 1;
309 
310   /* An infinity, zero or denormal requires low part 0 (positive or
311      negative).  */
312   if ((unsigned long) top_exp == hfmt->exp_nan || top_exp == 0)
313     {
314       if (bot_exp != 0)
315 	return 0;
316 
317       return !mant_bits_set (hfmt, ufrom + 8);
318     }
319 
320   /* The top part is now a finite normal value.  The long double value
321      is the sum of the two parts, and the top part must equal the
322      result of rounding the long double value to nearest double.  Thus
323      the bottom part must be <= 0.5ulp of the top part in absolute
324      value, and if it is < 0.5ulp then the long double is definitely
325      valid.  */
326   if (bot_exp < top_exp - 53)
327     return 1;
328   if (bot_exp > top_exp - 53 && bot_exp != 0)
329     return 0;
330   if (bot_exp == 0)
331     {
332       /* The bottom part is 0 or denormal.  Determine which, and if
333 	 denormal the first two set bits.  */
334       int first_bit = -1, second_bit = -1, cur_bit;
335       for (cur_bit = 0; (unsigned int) cur_bit < hfmt->man_len; cur_bit++)
336 	if (get_field (ufrom + 8, hfmt->byteorder, hfmt->totalsize,
337 		       hfmt->man_start + cur_bit, 1))
338 	  {
339 	    if (first_bit == -1)
340 	      first_bit = cur_bit;
341 	    else
342 	      {
343 		second_bit = cur_bit;
344 		break;
345 	      }
346 	  }
347       /* Bottom part 0 is OK.  */
348       if (first_bit == -1)
349 	return 1;
350       /* The real exponent of the bottom part is -first_bit.  */
351       if (-first_bit < top_exp - 53)
352 	return 1;
353       if (-first_bit > top_exp - 53)
354 	return 0;
355       /* The bottom part is at least 0.5ulp of the top part.  For this
356 	 to be OK, the bottom part must be exactly 0.5ulp (i.e. no
357 	 more bits set) and the top part must have last bit 0.  */
358       if (second_bit != -1)
359 	return 0;
360       return !get_field (ufrom, hfmt->byteorder, hfmt->totalsize,
361 			 hfmt->man_start + hfmt->man_len - 1, 1);
362     }
363   else
364     {
365       /* The bottom part is at least 0.5ulp of the top part.  For this
366 	 to be OK, it must be exactly 0.5ulp (i.e. no explicit bits
367 	 set) and the top part must have last bit 0.  */
368       if (get_field (ufrom, hfmt->byteorder, hfmt->totalsize,
369 		     hfmt->man_start + hfmt->man_len - 1, 1))
370 	return 0;
371       return !mant_bits_set (hfmt, ufrom + 8);
372     }
373 }
374 
375 const struct floatformat floatformat_ibm_long_double_big =
376 {
377   floatformat_big, 128, 0, 1, 11, 1023, 2047, 12, 52,
378   floatformat_intbit_no,
379   "floatformat_ibm_long_double_big",
380   floatformat_ibm_long_double_is_valid,
381   &floatformat_ieee_double_big
382 };
383 
384 const struct floatformat floatformat_ibm_long_double_little =
385 {
386   floatformat_little, 128, 0, 1, 11, 1023, 2047, 12, 52,
387   floatformat_intbit_no,
388   "floatformat_ibm_long_double_little",
389   floatformat_ibm_long_double_is_valid,
390   &floatformat_ieee_double_little
391 };
392 
393 
394 #ifndef min
395 #define min(a, b) ((a) < (b) ? (a) : (b))
396 #endif
397 
398 /* Return 1 if any bits are explicitly set in the mantissa of UFROM,
399    format FMT, 0 otherwise.  */
400 static int
401 mant_bits_set (const struct floatformat *fmt, const unsigned char *ufrom)
402 {
403   unsigned int mant_bits, mant_off;
404   int mant_bits_left;
405 
406   mant_off = fmt->man_start;
407   mant_bits_left = fmt->man_len;
408   while (mant_bits_left > 0)
409     {
410       mant_bits = min (mant_bits_left, 32);
411 
412       if (get_field (ufrom, fmt->byteorder, fmt->totalsize,
413 		     mant_off, mant_bits) != 0)
414 	return 1;
415 
416       mant_off += mant_bits;
417       mant_bits_left -= mant_bits;
418     }
419   return 0;
420 }
421 
422 /* Extract a field which starts at START and is LEN bits long.  DATA and
423    TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER.  */
424 static unsigned long
425 get_field (const unsigned char *data, enum floatformat_byteorders order,
426            unsigned int total_len, unsigned int start, unsigned int len)
427 {
428   unsigned long result = 0;
429   unsigned int cur_byte;
430   int lo_bit, hi_bit, cur_bitshift = 0;
431   int nextbyte = (order == floatformat_little) ? 1 : -1;
432 
433   /* Start is in big-endian bit order!  Fix that first.  */
434   start = total_len - (start + len);
435 
436   /* Start at the least significant part of the field.  */
437   if (order == floatformat_little)
438     cur_byte = start / FLOATFORMAT_CHAR_BIT;
439   else
440     cur_byte = (total_len - start - 1) / FLOATFORMAT_CHAR_BIT;
441 
442   lo_bit = start % FLOATFORMAT_CHAR_BIT;
443   hi_bit = min (lo_bit + len, FLOATFORMAT_CHAR_BIT);
444 
445   do
446     {
447       unsigned int shifted = *(data + cur_byte) >> lo_bit;
448       unsigned int bits = hi_bit - lo_bit;
449       unsigned int mask = (1 << bits) - 1;
450       result |= (shifted & mask) << cur_bitshift;
451       len -= bits;
452       cur_bitshift += bits;
453       cur_byte += nextbyte;
454       lo_bit = 0;
455       hi_bit = min (len, FLOATFORMAT_CHAR_BIT);
456     }
457   while (len != 0);
458 
459   return result;
460 }
461 
462 /* Convert from FMT to a double.
463    FROM is the address of the extended float.
464    Store the double in *TO.  */
465 
466 void
467 floatformat_to_double (const struct floatformat *fmt,
468                        const void *from, double *to)
469 {
470   const unsigned char *ufrom = (const unsigned char *) from;
471   double dto;
472   long exponent;
473   unsigned long mant;
474   unsigned int mant_bits, mant_off;
475   int mant_bits_left;
476 
477   /* Split values are not handled specially, since the top half has
478      the correctly rounded double value (in the only supported case of
479      split values).  */
480 
481   exponent = get_field (ufrom, fmt->byteorder, fmt->totalsize,
482 			fmt->exp_start, fmt->exp_len);
483 
484   /* If the exponent indicates a NaN, we don't have information to
485      decide what to do.  So we handle it like IEEE, except that we
486      don't try to preserve the type of NaN.  FIXME.  */
487   if ((unsigned long) exponent == fmt->exp_nan)
488     {
489       int nan = mant_bits_set (fmt, ufrom);
490 
491       /* On certain systems (such as GNU/Linux), the use of the
492 	 INFINITY macro below may generate a warning that cannot be
493 	 silenced due to a bug in GCC (PR preprocessor/11931).  The
494 	 preprocessor fails to recognise the __extension__ keyword in
495 	 conjunction with the GNU/C99 extension for hexadecimal
496 	 floating point constants and will issue a warning when
497 	 compiling with -pedantic.  */
498       if (nan)
499 	dto = NAN;
500       else
501 #ifdef __vax__
502 	dto = HUGE_VAL;
503 #else
504 	dto = INFINITY;
505 #endif
506 
507       if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1))
508 	dto = -dto;
509 
510       *to = dto;
511 
512       return;
513     }
514 
515   mant_bits_left = fmt->man_len;
516   mant_off = fmt->man_start;
517   dto = 0.0;
518 
519   /* Build the result algebraically.  Might go infinite, underflow, etc;
520      who cares. */
521 
522   /* For denorms use minimum exponent.  */
523   if (exponent == 0)
524     exponent = 1 - fmt->exp_bias;
525   else
526     {
527       exponent -= fmt->exp_bias;
528 
529       /* If this format uses a hidden bit, explicitly add it in now.
530 	 Otherwise, increment the exponent by one to account for the
531 	 integer bit.  */
532 
533       if (fmt->intbit == floatformat_intbit_no)
534 	dto = ldexp (1.0, exponent);
535       else
536 	exponent++;
537     }
538 
539   while (mant_bits_left > 0)
540     {
541       mant_bits = min (mant_bits_left, 32);
542 
543       mant = get_field (ufrom, fmt->byteorder, fmt->totalsize,
544 			 mant_off, mant_bits);
545 
546       dto += ldexp ((double) mant, exponent - mant_bits);
547       exponent -= mant_bits;
548       mant_off += mant_bits;
549       mant_bits_left -= mant_bits;
550     }
551 
552   /* Negate it if negative.  */
553   if (get_field (ufrom, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1))
554     dto = -dto;
555   *to = dto;
556 }
557 
558 static void put_field (unsigned char *, enum floatformat_byteorders,
559                        unsigned int,
560                        unsigned int,
561                        unsigned int,
562                        unsigned long);
563 
564 /* Set a field which starts at START and is LEN bits long.  DATA and
565    TOTAL_LEN are the thing we are extracting it from, in byteorder ORDER.  */
566 static void
567 put_field (unsigned char *data, enum floatformat_byteorders order,
568            unsigned int total_len, unsigned int start, unsigned int len,
569            unsigned long stuff_to_put)
570 {
571   unsigned int cur_byte;
572   int lo_bit, hi_bit;
573   int nextbyte = (order == floatformat_little) ? 1 : -1;
574 
575   /* Start is in big-endian bit order!  Fix that first.  */
576   start = total_len - (start + len);
577 
578   /* Start at the least significant part of the field.  */
579   if (order == floatformat_little)
580     cur_byte = start / FLOATFORMAT_CHAR_BIT;
581   else
582     cur_byte = (total_len - start - 1) / FLOATFORMAT_CHAR_BIT;
583 
584   lo_bit = start % FLOATFORMAT_CHAR_BIT;
585   hi_bit = min (lo_bit + len, FLOATFORMAT_CHAR_BIT);
586 
587   do
588     {
589       unsigned char *byte_ptr = data + cur_byte;
590       unsigned int bits = hi_bit - lo_bit;
591       unsigned int mask = ((1 << bits) - 1) << lo_bit;
592       *byte_ptr = (*byte_ptr & ~mask) | ((stuff_to_put << lo_bit) & mask);
593       stuff_to_put >>= bits;
594       len -= bits;
595       cur_byte += nextbyte;
596       lo_bit = 0;
597       hi_bit = min (len, FLOATFORMAT_CHAR_BIT);
598     }
599   while (len != 0);
600 }
601 
602 /* The converse: convert the double *FROM to an extended float
603    and store where TO points.  Neither FROM nor TO have any alignment
604    restrictions.  */
605 
606 void
607 floatformat_from_double (const struct floatformat *fmt,
608                          const double *from, void *to)
609 {
610   double dfrom;
611   int exponent;
612   double mant;
613   unsigned int mant_bits, mant_off;
614   int mant_bits_left;
615   unsigned char *uto = (unsigned char *) to;
616 
617   dfrom = *from;
618   memset (uto, 0, fmt->totalsize / FLOATFORMAT_CHAR_BIT);
619 
620   /* Split values are not handled specially, since a bottom half of
621      zero is correct for any value representable as double (in the
622      only supported case of split values).  */
623 
624   /* If negative, set the sign bit.  */
625   if (dfrom < 0)
626     {
627       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->sign_start, 1, 1);
628       dfrom = -dfrom;
629     }
630 
631   if (dfrom == 0)
632     {
633       /* 0.0.  */
634       return;
635     }
636 
637   if (dfrom != dfrom)
638     {
639       /* NaN.  */
640       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
641 		 fmt->exp_len, fmt->exp_nan);
642       /* Be sure it's not infinity, but NaN value is irrelevant.  */
643       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->man_start,
644 		 32, 1);
645       return;
646     }
647 
648   if (dfrom + dfrom == dfrom)
649     {
650       /* This can only happen for an infinite value (or zero, which we
651 	 already handled above).  */
652       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
653 		 fmt->exp_len, fmt->exp_nan);
654       return;
655     }
656 
657   mant = frexp (dfrom, &exponent);
658   if (exponent + fmt->exp_bias - 1 > 0)
659     put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
660 	       fmt->exp_len, exponent + fmt->exp_bias - 1);
661   else
662     {
663       /* Handle a denormalized number.  FIXME: What should we do for
664 	 non-IEEE formats?  */
665       put_field (uto, fmt->byteorder, fmt->totalsize, fmt->exp_start,
666 		 fmt->exp_len, 0);
667       mant = ldexp (mant, exponent + fmt->exp_bias - 1);
668     }
669 
670   mant_bits_left = fmt->man_len;
671   mant_off = fmt->man_start;
672   while (mant_bits_left > 0)
673     {
674       unsigned long mant_long;
675       mant_bits = mant_bits_left < 32 ? mant_bits_left : 32;
676 
677       mant *= 4294967296.0;
678       mant_long = (unsigned long)mant;
679       mant -= mant_long;
680 
681       /* If the integer bit is implicit, and we are not creating a
682 	 denormalized number, then we need to discard it.  */
683       if ((unsigned int) mant_bits_left == fmt->man_len
684 	  && fmt->intbit == floatformat_intbit_no
685 	  && exponent + fmt->exp_bias - 1 > 0)
686 	{
687 	  mant_long &= 0x7fffffff;
688 	  mant_bits -= 1;
689 	}
690       else if (mant_bits < 32)
691 	{
692 	  /* The bits we want are in the most significant MANT_BITS bits of
693 	     mant_long.  Move them to the least significant.  */
694 	  mant_long >>= 32 - mant_bits;
695 	}
696 
697       put_field (uto, fmt->byteorder, fmt->totalsize,
698 		 mant_off, mant_bits, mant_long);
699       mant_off += mant_bits;
700       mant_bits_left -= mant_bits;
701     }
702 }
703 
704 /* Return non-zero iff the data at FROM is a valid number in format FMT.  */
705 
706 int
707 floatformat_is_valid (const struct floatformat *fmt, const void *from)
708 {
709   return fmt->is_valid (fmt, from);
710 }
711 
712 
713 #ifdef IEEE_DEBUG
714 
715 #include <stdio.h>
716 
717 /* This is to be run on a host which uses IEEE floating point.  */
718 
719 void
720 ieee_test (double n)
721 {
722   double result;
723 
724   floatformat_to_double (&floatformat_ieee_double_little, &n, &result);
725   if ((n != result && (! isnan (n) || ! isnan (result)))
726       || (n < 0 && result >= 0)
727       || (n >= 0 && result < 0))
728     printf ("Differ(to): %.20g -> %.20g\n", n, result);
729 
730   floatformat_from_double (&floatformat_ieee_double_little, &n, &result);
731   if ((n != result && (! isnan (n) || ! isnan (result)))
732       || (n < 0 && result >= 0)
733       || (n >= 0 && result < 0))
734     printf ("Differ(from): %.20g -> %.20g\n", n, result);
735 
736 #if 0
737   {
738     char exten[16];
739 
740     floatformat_from_double (&floatformat_m68881_ext, &n, exten);
741     floatformat_to_double (&floatformat_m68881_ext, exten, &result);
742     if (n != result)
743       printf ("Differ(to+from): %.20g -> %.20g\n", n, result);
744   }
745 #endif
746 
747 #if IEEE_DEBUG > 1
748   /* This is to be run on a host which uses 68881 format.  */
749   {
750     long double ex = *(long double *)exten;
751     if (ex != n)
752       printf ("Differ(from vs. extended): %.20g\n", n);
753   }
754 #endif
755 }
756 
757 int
758 main (void)
759 {
760   ieee_test (0.0);
761   ieee_test (0.5);
762   ieee_test (1.1);
763   ieee_test (256.0);
764   ieee_test (0.12345);
765   ieee_test (234235.78907234);
766   ieee_test (-512.0);
767   ieee_test (-0.004321);
768   ieee_test (1.2E-70);
769   ieee_test (1.2E-316);
770   ieee_test (4.9406564584124654E-324);
771   ieee_test (- 4.9406564584124654E-324);
772   ieee_test (- 0.0);
773   ieee_test (- INFINITY);
774   ieee_test (- NAN);
775   ieee_test (INFINITY);
776   ieee_test (NAN);
777   return 0;
778 }
779 #endif
780