1 /* Copyright (C) 2007-2022 Free Software Foundation, Inc.
2 
3 This file is part of GCC.
4 
5 GCC is free software; you can redistribute it and/or modify it under
6 the terms of the GNU General Public License as published by the Free
7 Software Foundation; either version 3, or (at your option) any later
8 version.
9 
10 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
11 WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
13 for more details.
14 
15 Under Section 7 of GPL version 3, you are granted additional
16 permissions described in the GCC Runtime Library Exception, version
17 3.1, as published by the Free Software Foundation.
18 
19 You should have received a copy of the GNU General Public License and
20 a copy of the GCC Runtime Library Exception along with this program;
21 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
22 <http://www.gnu.org/licenses/>.  */
23 
24 /*****************************************************************************
25  *
26  *    Helper add functions (for fma)
27  *
28  *    __BID_INLINE__ UINT64 get_add64(
29  *        UINT64 sign_x, int exponent_x, UINT64 coefficient_x,
30  *        UINT64 sign_y, int exponent_y, UINT64 coefficient_y,
31  *                                                 int rounding_mode)
32  *
33  *   __BID_INLINE__ UINT64 get_add128(
34  *                       UINT64 sign_x, int exponent_x, UINT64 coefficient_x,
35  *                       UINT64 sign_y, int final_exponent_y, UINT128 CY,
36  *                       int extra_digits, int rounding_mode)
37  *
38  *****************************************************************************
39  *
40  *  Algorithm description:
41  *
42  *  get_add64:  same as BID64 add, but arguments are unpacked and there
43  *                                 are no special case checks
44  *
45  *  get_add128: add 64-bit coefficient to 128-bit product (which contains
46  *                                        16+extra_digits decimal digits),
47  *                         return BID64 result
48  *              - the exponents are compared and the two coefficients are
49  *                properly aligned for addition/subtraction
50  *              - multiple paths are needed
51  *              - final result exponent is calculated and the lower term is
52  *                      rounded first if necessary, to avoid manipulating
53  *                      coefficients longer than 128 bits
54  *
55  ****************************************************************************/
56 
57 #ifndef _INLINE_BID_ADD_H_
58 #define _INLINE_BID_ADD_H_
59 
60 #include "bid_internal.h"
61 
62 #define MAX_FORMAT_DIGITS     16
63 #define DECIMAL_EXPONENT_BIAS 398
64 #define MASK_BINARY_EXPONENT  0x7ff0000000000000ull
65 #define BINARY_EXPONENT_BIAS  0x3ff
66 #define UPPER_EXPON_LIMIT     51
67 
68 ///////////////////////////////////////////////////////////////////////
69 //
70 // get_add64() is essentially the same as bid_add(), except that
71 //             the arguments are unpacked
72 //
73 //////////////////////////////////////////////////////////////////////
74 __BID_INLINE__ UINT64
get_add64(UINT64 sign_x,int exponent_x,UINT64 coefficient_x,UINT64 sign_y,int exponent_y,UINT64 coefficient_y,int rounding_mode,unsigned * fpsc)75 get_add64 (UINT64 sign_x, int exponent_x, UINT64 coefficient_x,
76              UINT64 sign_y, int exponent_y, UINT64 coefficient_y,
77              int rounding_mode, unsigned *fpsc) {
78   UINT128 CA, CT, CT_new;
79   UINT64 sign_a, sign_b, coefficient_a, coefficient_b, sign_s, sign_ab,
80     rem_a;
81   UINT64 saved_ca, saved_cb, C0_64, C64, remainder_h, T1, carry, tmp,
82     C64_new;
83   int_double tempx;
84   int exponent_a, exponent_b, diff_dec_expon;
85   int bin_expon_ca, extra_digits, amount, scale_k, scale_ca;
86   unsigned rmode, status;
87 
88   // sort arguments by exponent
89   if (exponent_x <= exponent_y) {
90     sign_a = sign_y;
91     exponent_a = exponent_y;
92     coefficient_a = coefficient_y;
93     sign_b = sign_x;
94     exponent_b = exponent_x;
95     coefficient_b = coefficient_x;
96   } else {
97     sign_a = sign_x;
98     exponent_a = exponent_x;
99     coefficient_a = coefficient_x;
100     sign_b = sign_y;
101     exponent_b = exponent_y;
102     coefficient_b = coefficient_y;
103   }
104 
105   // exponent difference
106   diff_dec_expon = exponent_a - exponent_b;
107 
108   /* get binary coefficients of x and y */
109 
110   //--- get number of bits in the coefficients of x and y ---
111 
112   tempx.d = (double) coefficient_a;
113   bin_expon_ca = ((tempx.i & MASK_BINARY_EXPONENT) >> 52) - 0x3ff;
114 
115   if (!coefficient_a) {
116     return get_BID64 (sign_b, exponent_b, coefficient_b, rounding_mode,
117                           fpsc);
118   }
119   if (diff_dec_expon > MAX_FORMAT_DIGITS) {
120     // normalize a to a 16-digit coefficient
121 
122     scale_ca = estimate_decimal_digits[bin_expon_ca];
123     if (coefficient_a >= power10_table_128[scale_ca].w[0])
124       scale_ca++;
125 
126     scale_k = 16 - scale_ca;
127 
128     coefficient_a *= power10_table_128[scale_k].w[0];
129 
130     diff_dec_expon -= scale_k;
131     exponent_a -= scale_k;
132 
133     /* get binary coefficients of x and y */
134 
135     //--- get number of bits in the coefficients of x and y ---
136     tempx.d = (double) coefficient_a;
137     bin_expon_ca = ((tempx.i & MASK_BINARY_EXPONENT) >> 52) - 0x3ff;
138 
139     if (diff_dec_expon > MAX_FORMAT_DIGITS) {
140 #ifdef SET_STATUS_FLAGS
141       if (coefficient_b) {
142           __set_status_flags (fpsc, INEXACT_EXCEPTION);
143       }
144 #endif
145 
146 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
147 #ifndef IEEE_ROUND_NEAREST
148       if (((rounding_mode) & 3) && coefficient_b) // not ROUNDING_TO_NEAREST
149       {
150           switch (rounding_mode) {
151           case ROUNDING_DOWN:
152             if (sign_b) {
153               coefficient_a -= ((((SINT64) sign_a) >> 63) | 1);
154               if (coefficient_a < 1000000000000000ull) {
155                 exponent_a--;
156                 coefficient_a = 9999999999999999ull;
157               } else if (coefficient_a >= 10000000000000000ull) {
158                 exponent_a++;
159                 coefficient_a = 1000000000000000ull;
160               }
161             }
162             break;
163           case ROUNDING_UP:
164             if (!sign_b) {
165               coefficient_a += ((((SINT64) sign_a) >> 63) | 1);
166               if (coefficient_a < 1000000000000000ull) {
167                 exponent_a--;
168                 coefficient_a = 9999999999999999ull;
169               } else if (coefficient_a >= 10000000000000000ull) {
170                 exponent_a++;
171                 coefficient_a = 1000000000000000ull;
172               }
173             }
174             break;
175           default:  // RZ
176             if (sign_a != sign_b) {
177               coefficient_a--;
178               if (coefficient_a < 1000000000000000ull) {
179                 exponent_a--;
180                 coefficient_a = 9999999999999999ull;
181               }
182             }
183             break;
184           }
185       } else
186 #endif
187 #endif
188           // check special case here
189           if ((coefficient_a == 1000000000000000ull)
190               && (diff_dec_expon == MAX_FORMAT_DIGITS + 1)
191               && (sign_a ^ sign_b)
192               && (coefficient_b > 5000000000000000ull)) {
193           coefficient_a = 9999999999999999ull;
194           exponent_a--;
195       }
196 
197       return get_BID64 (sign_a, exponent_a, coefficient_a,
198                               rounding_mode, fpsc);
199     }
200   }
201   // test whether coefficient_a*10^(exponent_a-exponent_b)  may exceed 2^62
202   if (bin_expon_ca + estimate_bin_expon[diff_dec_expon] < 60) {
203     // coefficient_a*10^(exponent_a-exponent_b)<2^63
204 
205     // multiply by 10^(exponent_a-exponent_b)
206     coefficient_a *= power10_table_128[diff_dec_expon].w[0];
207 
208     // sign mask
209     sign_b = ((SINT64) sign_b) >> 63;
210     // apply sign to coeff. of b
211     coefficient_b = (coefficient_b + sign_b) ^ sign_b;
212 
213     // apply sign to coefficient a
214     sign_a = ((SINT64) sign_a) >> 63;
215     coefficient_a = (coefficient_a + sign_a) ^ sign_a;
216 
217     coefficient_a += coefficient_b;
218     // get sign
219     sign_s = ((SINT64) coefficient_a) >> 63;
220     coefficient_a = (coefficient_a + sign_s) ^ sign_s;
221     sign_s &= 0x8000000000000000ull;
222 
223     // coefficient_a < 10^16 ?
224     if (coefficient_a < power10_table_128[MAX_FORMAT_DIGITS].w[0]) {
225 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
226 #ifndef IEEE_ROUND_NEAREST
227       if (rounding_mode == ROUNDING_DOWN && (!coefficient_a)
228             && sign_a != sign_b)
229           sign_s = 0x8000000000000000ull;
230 #endif
231 #endif
232       return get_BID64 (sign_s, exponent_b, coefficient_a,
233                               rounding_mode, fpsc);
234     }
235     // otherwise rounding is necessary
236 
237     // already know coefficient_a<10^19
238     // coefficient_a < 10^17 ?
239     if (coefficient_a < power10_table_128[17].w[0])
240       extra_digits = 1;
241     else if (coefficient_a < power10_table_128[18].w[0])
242       extra_digits = 2;
243     else
244       extra_digits = 3;
245 
246 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
247 #ifndef IEEE_ROUND_NEAREST
248     rmode = rounding_mode;
249     if (sign_s && (unsigned) (rmode - 1) < 2)
250       rmode = 3 - rmode;
251 #else
252     rmode = 0;
253 #endif
254 #else
255     rmode = 0;
256 #endif
257     coefficient_a += round_const_table[rmode][extra_digits];
258 
259     // get P*(2^M[extra_digits])/10^extra_digits
260     __mul_64x64_to_128 (CT, coefficient_a,
261                               reciprocals10_64[extra_digits]);
262 
263     // now get P/10^extra_digits: shift C64 right by M[extra_digits]-128
264     amount = short_recip_scale[extra_digits];
265     C64 = CT.w[1] >> amount;
266 
267   } else {
268     // coefficient_a*10^(exponent_a-exponent_b) is large
269     sign_s = sign_a;
270 
271 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
272 #ifndef IEEE_ROUND_NEAREST
273     rmode = rounding_mode;
274     if (sign_s && (unsigned) (rmode - 1) < 2)
275       rmode = 3 - rmode;
276 #else
277     rmode = 0;
278 #endif
279 #else
280     rmode = 0;
281 #endif
282 
283     // check whether we can take faster path
284     scale_ca = estimate_decimal_digits[bin_expon_ca];
285 
286     sign_ab = sign_a ^ sign_b;
287     sign_ab = ((SINT64) sign_ab) >> 63;
288 
289     // T1 = 10^(16-diff_dec_expon)
290     T1 = power10_table_128[16 - diff_dec_expon].w[0];
291 
292     // get number of digits in coefficient_a
293     //P_ca = power10_table_128[scale_ca].w[0];
294     //P_ca_m1 = power10_table_128[scale_ca-1].w[0];
295     if (coefficient_a >= power10_table_128[scale_ca].w[0]) {
296       scale_ca++;
297       //P_ca_m1 = P_ca;
298       //P_ca = power10_table_128[scale_ca].w[0];
299     }
300 
301     scale_k = 16 - scale_ca;
302 
303     // apply sign
304     //Ts = (T1 + sign_ab) ^ sign_ab;
305 
306     // test range of ca
307     //X = coefficient_a + Ts - P_ca_m1;
308 
309     // addition
310     saved_ca = coefficient_a - T1;
311     coefficient_a =
312       (SINT64) saved_ca *(SINT64) power10_table_128[scale_k].w[0];
313     extra_digits = diff_dec_expon - scale_k;
314 
315     // apply sign
316     saved_cb = (coefficient_b + sign_ab) ^ sign_ab;
317     // add 10^16 and rounding constant
318     coefficient_b =
319       saved_cb + 10000000000000000ull +
320       round_const_table[rmode][extra_digits];
321 
322     // get P*(2^M[extra_digits])/10^extra_digits
323     __mul_64x64_to_128 (CT, coefficient_b,
324                               reciprocals10_64[extra_digits]);
325 
326     // now get P/10^extra_digits: shift C64 right by M[extra_digits]-128
327     amount = short_recip_scale[extra_digits];
328     C0_64 = CT.w[1] >> amount;
329 
330     // result coefficient
331     C64 = C0_64 + coefficient_a;
332     // filter out difficult (corner) cases
333     // the following test is equivalent to
334     // ( (initial_coefficient_a + Ts) < P_ca &&
335     //     (initial_coefficient_a + Ts) > P_ca_m1 ),
336     // which ensures the number of digits in coefficient_a does not change
337     // after adding (the appropriately scaled and rounded) coefficient_b
338     if ((UINT64) (C64 - 1000000000000000ull - 1) >
339           9000000000000000ull - 2) {
340       if (C64 >= 10000000000000000ull) {
341           // result has more than 16 digits
342           if (!scale_k) {
343             // must divide coeff_a by 10
344             saved_ca = saved_ca + T1;
345             __mul_64x64_to_128 (CA, saved_ca, 0x3333333333333334ull);
346             //reciprocals10_64[1]);
347             coefficient_a = CA.w[1] >> 1;
348             rem_a =
349               saved_ca - (coefficient_a << 3) - (coefficient_a << 1);
350             coefficient_a = coefficient_a - T1;
351 
352             saved_cb +=
353               /*90000000000000000 */ +rem_a *
354               power10_table_128[diff_dec_expon].w[0];
355           } else
356             coefficient_a =
357               (SINT64) (saved_ca - T1 -
358                           (T1 << 3)) * (SINT64) power10_table_128[scale_k -
359                                                                             1].w[0];
360 
361           extra_digits++;
362           coefficient_b =
363             saved_cb + 100000000000000000ull +
364             round_const_table[rmode][extra_digits];
365 
366           // get P*(2^M[extra_digits])/10^extra_digits
367           __mul_64x64_to_128 (CT, coefficient_b,
368                                   reciprocals10_64[extra_digits]);
369 
370           // now get P/10^extra_digits: shift C64 right by M[extra_digits]-128
371           amount = short_recip_scale[extra_digits];
372           C0_64 = CT.w[1] >> amount;
373 
374           // result coefficient
375           C64 = C0_64 + coefficient_a;
376       } else if (C64 <= 1000000000000000ull) {
377           // less than 16 digits in result
378           coefficient_a =
379             (SINT64) saved_ca *(SINT64) power10_table_128[scale_k +
380                                                                       1].w[0];
381           //extra_digits --;
382           exponent_b--;
383           coefficient_b =
384             (saved_cb << 3) + (saved_cb << 1) + 100000000000000000ull +
385             round_const_table[rmode][extra_digits];
386 
387           // get P*(2^M[extra_digits])/10^extra_digits
388           __mul_64x64_to_128 (CT_new, coefficient_b,
389                                   reciprocals10_64[extra_digits]);
390 
391           // now get P/10^extra_digits: shift C64 right by M[extra_digits]-128
392           amount = short_recip_scale[extra_digits];
393           C0_64 = CT_new.w[1] >> amount;
394 
395           // result coefficient
396           C64_new = C0_64 + coefficient_a;
397           if (C64_new < 10000000000000000ull) {
398             C64 = C64_new;
399 #ifdef SET_STATUS_FLAGS
400             CT = CT_new;
401 #endif
402           } else
403             exponent_b++;
404       }
405 
406     }
407 
408   }
409 
410 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
411 #ifndef IEEE_ROUND_NEAREST
412   if (rmode == 0)   //ROUNDING_TO_NEAREST
413 #endif
414     if (C64 & 1) {
415       // check whether fractional part of initial_P/10^extra_digits
416       // is exactly .5
417       // this is the same as fractional part of
418       //      (initial_P + 0.5*10^extra_digits)/10^extra_digits is exactly zero
419 
420       // get remainder
421       remainder_h = CT.w[1] << (64 - amount);
422 
423       // test whether fractional part is 0
424       if (!remainder_h && (CT.w[0] < reciprocals10_64[extra_digits])) {
425           C64--;
426       }
427     }
428 #endif
429 
430 #ifdef SET_STATUS_FLAGS
431   status = INEXACT_EXCEPTION;
432 
433   // get remainder
434   remainder_h = CT.w[1] << (64 - amount);
435 
436   switch (rmode) {
437   case ROUNDING_TO_NEAREST:
438   case ROUNDING_TIES_AWAY:
439     // test whether fractional part is 0
440     if ((remainder_h == 0x8000000000000000ull)
441           && (CT.w[0] < reciprocals10_64[extra_digits]))
442       status = EXACT_STATUS;
443     break;
444   case ROUNDING_DOWN:
445   case ROUNDING_TO_ZERO:
446     if (!remainder_h && (CT.w[0] < reciprocals10_64[extra_digits]))
447       status = EXACT_STATUS;
448     break;
449   default:
450     // round up
451     __add_carry_out (tmp, carry, CT.w[0],
452                          reciprocals10_64[extra_digits]);
453     if ((remainder_h >> (64 - amount)) + carry >=
454           (((UINT64) 1) << amount))
455       status = EXACT_STATUS;
456     break;
457   }
458   __set_status_flags (fpsc, status);
459 
460 #endif
461 
462   return get_BID64 (sign_s, exponent_b + extra_digits, C64,
463                         rounding_mode, fpsc);
464 }
465 
466 
467 ///////////////////////////////////////////////////////////////////
468 // round 128-bit coefficient and return result in BID64 format
469 // do not worry about midpoint cases
470 //////////////////////////////////////////////////////////////////
471 static UINT64
__bid_simple_round64_sticky(UINT64 sign,int exponent,UINT128 P,int extra_digits,int rounding_mode,unsigned * fpsc)472 __bid_simple_round64_sticky (UINT64 sign, int exponent, UINT128 P,
473                                    int extra_digits, int rounding_mode,
474                                    unsigned *fpsc) {
475   UINT128 Q_high, Q_low, C128;
476   UINT64 C64;
477   int amount, rmode;
478 
479   rmode = rounding_mode;
480 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
481 #ifndef IEEE_ROUND_NEAREST
482   if (sign && (unsigned) (rmode - 1) < 2)
483     rmode = 3 - rmode;
484 #endif
485 #endif
486   __add_128_64 (P, P, round_const_table[rmode][extra_digits]);
487 
488   // get P*(2^M[extra_digits])/10^extra_digits
489   __mul_128x128_full (Q_high, Q_low, P,
490                           reciprocals10_128[extra_digits]);
491 
492   // now get P/10^extra_digits: shift Q_high right by M[extra_digits]-128
493   amount = recip_scale[extra_digits];
494   __shr_128 (C128, Q_high, amount);
495 
496   C64 = __low_64 (C128);
497 
498 #ifdef SET_STATUS_FLAGS
499 
500   __set_status_flags (fpsc, INEXACT_EXCEPTION);
501 
502 #endif
503 
504   return get_BID64 (sign, exponent, C64, rounding_mode, fpsc);
505 }
506 
507 ///////////////////////////////////////////////////////////////////
508 // round 128-bit coefficient and return result in BID64 format
509 ///////////////////////////////////////////////////////////////////
510 static UINT64
__bid_full_round64(UINT64 sign,int exponent,UINT128 P,int extra_digits,int rounding_mode,unsigned * fpsc)511 __bid_full_round64 (UINT64 sign, int exponent, UINT128 P,
512                         int extra_digits, int rounding_mode,
513                         unsigned *fpsc) {
514   UINT128 Q_high, Q_low, C128, Stemp, PU;
515   UINT64 remainder_h, C64, carry, CY;
516   int amount, amount2, rmode, status = 0;
517 
518   if (exponent < 0) {
519     if (exponent >= -16 && (extra_digits + exponent < 0)) {
520       extra_digits = -exponent;
521 #ifdef SET_STATUS_FLAGS
522       if (extra_digits > 0) {
523           rmode = rounding_mode;
524           if (sign && (unsigned) (rmode - 1) < 2)
525             rmode = 3 - rmode;
526           __add_128_128 (PU, P,
527                            round_const_table_128[rmode][extra_digits]);
528           if (__unsigned_compare_gt_128
529               (power10_table_128[extra_digits + 15], PU))
530             status = UNDERFLOW_EXCEPTION;
531       }
532 #endif
533     }
534   }
535 
536   if (extra_digits > 0) {
537     exponent += extra_digits;
538     rmode = rounding_mode;
539     if (sign && (unsigned) (rmode - 1) < 2)
540       rmode = 3 - rmode;
541     __add_128_128 (P, P, round_const_table_128[rmode][extra_digits]);
542 
543     // get P*(2^M[extra_digits])/10^extra_digits
544     __mul_128x128_full (Q_high, Q_low, P,
545                               reciprocals10_128[extra_digits]);
546 
547     // now get P/10^extra_digits: shift Q_high right by M[extra_digits]-128
548     amount = recip_scale[extra_digits];
549     __shr_128_long (C128, Q_high, amount);
550 
551     C64 = __low_64 (C128);
552 
553 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
554 #ifndef IEEE_ROUND_NEAREST
555     if (rmode == 0) //ROUNDING_TO_NEAREST
556 #endif
557       if (C64 & 1) {
558           // check whether fractional part of initial_P/10^extra_digits
559           // is exactly .5
560 
561           // get remainder
562           amount2 = 64 - amount;
563           remainder_h = 0;
564           remainder_h--;
565           remainder_h >>= amount2;
566           remainder_h = remainder_h & Q_high.w[0];
567 
568           if (!remainder_h
569               && (Q_low.w[1] < reciprocals10_128[extra_digits].w[1]
570                     || (Q_low.w[1] == reciprocals10_128[extra_digits].w[1]
571                         && Q_low.w[0] <
572                         reciprocals10_128[extra_digits].w[0]))) {
573             C64--;
574           }
575       }
576 #endif
577 
578 #ifdef SET_STATUS_FLAGS
579     status |= INEXACT_EXCEPTION;
580 
581     // get remainder
582     remainder_h = Q_high.w[0] << (64 - amount);
583 
584     switch (rmode) {
585     case ROUNDING_TO_NEAREST:
586     case ROUNDING_TIES_AWAY:
587       // test whether fractional part is 0
588       if (remainder_h == 0x8000000000000000ull
589             && (Q_low.w[1] < reciprocals10_128[extra_digits].w[1]
590                 || (Q_low.w[1] == reciprocals10_128[extra_digits].w[1]
591                       && Q_low.w[0] <
592                       reciprocals10_128[extra_digits].w[0])))
593           status = EXACT_STATUS;
594       break;
595     case ROUNDING_DOWN:
596     case ROUNDING_TO_ZERO:
597       if (!remainder_h
598             && (Q_low.w[1] < reciprocals10_128[extra_digits].w[1]
599                 || (Q_low.w[1] == reciprocals10_128[extra_digits].w[1]
600                       && Q_low.w[0] <
601                       reciprocals10_128[extra_digits].w[0])))
602           status = EXACT_STATUS;
603       break;
604     default:
605       // round up
606       __add_carry_out (Stemp.w[0], CY, Q_low.w[0],
607                            reciprocals10_128[extra_digits].w[0]);
608       __add_carry_in_out (Stemp.w[1], carry, Q_low.w[1],
609                                 reciprocals10_128[extra_digits].w[1], CY);
610       if ((remainder_h >> (64 - amount)) + carry >=
611             (((UINT64) 1) << amount))
612           status = EXACT_STATUS;
613     }
614 
615     __set_status_flags (fpsc, status);
616 
617 #endif
618   } else {
619     C64 = P.w[0];
620     if (!C64) {
621       sign = 0;
622       if (rounding_mode == ROUNDING_DOWN)
623           sign = 0x8000000000000000ull;
624     }
625   }
626   return get_BID64 (sign, exponent, C64, rounding_mode, fpsc);
627 }
628 
629 /////////////////////////////////////////////////////////////////////////////////
630 // round 192-bit coefficient (P, remainder_P) and return result in BID64 format
631 // the lowest 64 bits (remainder_P) are used for midpoint checking only
632 ////////////////////////////////////////////////////////////////////////////////
633 static UINT64
__bid_full_round64_remainder(UINT64 sign,int exponent,UINT128 P,int extra_digits,UINT64 remainder_P,int rounding_mode,unsigned * fpsc,unsigned uf_status)634 __bid_full_round64_remainder (UINT64 sign, int exponent, UINT128 P,
635                                     int extra_digits, UINT64 remainder_P,
636                                     int rounding_mode, unsigned *fpsc,
637                                     unsigned uf_status) {
638   UINT128 Q_high, Q_low, C128, Stemp;
639   UINT64 remainder_h, C64, carry, CY;
640   int amount, amount2, rmode, status = uf_status;
641 
642   rmode = rounding_mode;
643   if (sign && (unsigned) (rmode - 1) < 2)
644     rmode = 3 - rmode;
645   if (rmode == ROUNDING_UP && remainder_P) {
646     P.w[0]++;
647     if (!P.w[0])
648       P.w[1]++;
649   }
650 
651   if (extra_digits) {
652     __add_128_64 (P, P, round_const_table[rmode][extra_digits]);
653 
654     // get P*(2^M[extra_digits])/10^extra_digits
655     __mul_128x128_full (Q_high, Q_low, P,
656                               reciprocals10_128[extra_digits]);
657 
658     // now get P/10^extra_digits: shift Q_high right by M[extra_digits]-128
659     amount = recip_scale[extra_digits];
660     __shr_128 (C128, Q_high, amount);
661 
662     C64 = __low_64 (C128);
663 
664 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
665 #ifndef IEEE_ROUND_NEAREST
666     if (rmode == 0) //ROUNDING_TO_NEAREST
667 #endif
668       if (!remainder_P && (C64 & 1)) {
669           // check whether fractional part of initial_P/10^extra_digits
670           // is exactly .5
671 
672           // get remainder
673           amount2 = 64 - amount;
674           remainder_h = 0;
675           remainder_h--;
676           remainder_h >>= amount2;
677           remainder_h = remainder_h & Q_high.w[0];
678 
679           if (!remainder_h
680               && (Q_low.w[1] < reciprocals10_128[extra_digits].w[1]
681                     || (Q_low.w[1] == reciprocals10_128[extra_digits].w[1]
682                         && Q_low.w[0] <
683                         reciprocals10_128[extra_digits].w[0]))) {
684             C64--;
685           }
686       }
687 #endif
688 
689 #ifdef SET_STATUS_FLAGS
690     status |= INEXACT_EXCEPTION;
691 
692     if (!remainder_P) {
693       // get remainder
694       remainder_h = Q_high.w[0] << (64 - amount);
695 
696       switch (rmode) {
697       case ROUNDING_TO_NEAREST:
698       case ROUNDING_TIES_AWAY:
699           // test whether fractional part is 0
700           if (remainder_h == 0x8000000000000000ull
701               && (Q_low.w[1] < reciprocals10_128[extra_digits].w[1]
702                     || (Q_low.w[1] == reciprocals10_128[extra_digits].w[1]
703                         && Q_low.w[0] <
704                         reciprocals10_128[extra_digits].w[0])))
705             status = EXACT_STATUS;
706           break;
707       case ROUNDING_DOWN:
708       case ROUNDING_TO_ZERO:
709           if (!remainder_h
710               && (Q_low.w[1] < reciprocals10_128[extra_digits].w[1]
711                     || (Q_low.w[1] == reciprocals10_128[extra_digits].w[1]
712                         && Q_low.w[0] <
713                         reciprocals10_128[extra_digits].w[0])))
714             status = EXACT_STATUS;
715           break;
716       default:
717           // round up
718           __add_carry_out (Stemp.w[0], CY, Q_low.w[0],
719                                reciprocals10_128[extra_digits].w[0]);
720           __add_carry_in_out (Stemp.w[1], carry, Q_low.w[1],
721                                   reciprocals10_128[extra_digits].w[1], CY);
722           if ((remainder_h >> (64 - amount)) + carry >=
723               (((UINT64) 1) << amount))
724             status = EXACT_STATUS;
725       }
726     }
727     __set_status_flags (fpsc, status);
728 
729 #endif
730   } else {
731     C64 = P.w[0];
732 #ifdef SET_STATUS_FLAGS
733     if (remainder_P) {
734       __set_status_flags (fpsc, uf_status | INEXACT_EXCEPTION);
735     }
736 #endif
737   }
738 
739   return get_BID64 (sign, exponent + extra_digits, C64, rounding_mode,
740                         fpsc);
741 }
742 
743 
744 ///////////////////////////////////////////////////////////////////
745 // get P/10^extra_digits
746 // result fits in 64 bits
747 ///////////////////////////////////////////////////////////////////
748 __BID_INLINE__ UINT64
__truncate(UINT128 P,int extra_digits)749 __truncate (UINT128 P, int extra_digits)
750 // extra_digits <= 16
751 {
752   UINT128 Q_high, Q_low, C128;
753   UINT64 C64;
754   int amount;
755 
756   // get P*(2^M[extra_digits])/10^extra_digits
757   __mul_128x128_full (Q_high, Q_low, P,
758                           reciprocals10_128[extra_digits]);
759 
760   // now get P/10^extra_digits: shift Q_high right by M[extra_digits]-128
761   amount = recip_scale[extra_digits];
762   __shr_128 (C128, Q_high, amount);
763 
764   C64 = __low_64 (C128);
765 
766   return C64;
767 }
768 
769 
770 ///////////////////////////////////////////////////////////////////
771 // return number of decimal digits in 128-bit value X
772 ///////////////////////////////////////////////////////////////////
773 __BID_INLINE__ int
__get_dec_digits64(UINT128 X)774 __get_dec_digits64 (UINT128 X) {
775   int_double tempx;
776   int digits_x, bin_expon_cx;
777 
778   if (!X.w[1]) {
779     //--- get number of bits in the coefficients of x and y ---
780     tempx.d = (double) X.w[0];
781     bin_expon_cx = ((tempx.i & MASK_BINARY_EXPONENT) >> 52) - 0x3ff;
782     // get number of decimal digits in the coeff_x
783     digits_x = estimate_decimal_digits[bin_expon_cx];
784     if (X.w[0] >= power10_table_128[digits_x].w[0])
785       digits_x++;
786     return digits_x;
787   }
788   tempx.d = (double) X.w[1];
789   bin_expon_cx = ((tempx.i & MASK_BINARY_EXPONENT) >> 52) - 0x3ff;
790   // get number of decimal digits in the coeff_x
791   digits_x = estimate_decimal_digits[bin_expon_cx + 64];
792   if (__unsigned_compare_ge_128 (X, power10_table_128[digits_x]))
793     digits_x++;
794 
795   return digits_x;
796 }
797 
798 
799 ////////////////////////////////////////////////////////////////////////////////
800 //
801 // add 64-bit coefficient to 128-bit coefficient, return result in BID64 format
802 //
803 ////////////////////////////////////////////////////////////////////////////////
804 __BID_INLINE__ UINT64
get_add128(UINT64 sign_x,int exponent_x,UINT64 coefficient_x,UINT64 sign_y,int final_exponent_y,UINT128 CY,int extra_digits,int rounding_mode,unsigned * fpsc)805 get_add128 (UINT64 sign_x, int exponent_x, UINT64 coefficient_x,
806               UINT64 sign_y, int final_exponent_y, UINT128 CY,
807               int extra_digits, int rounding_mode, unsigned *fpsc) {
808   UINT128 CY_L, CX, FS, F, CT, ST, T2;
809   UINT64 CYh, CY0L, T, S, coefficient_y, remainder_y;
810   SINT64 D = 0;
811   int_double tempx;
812   int diff_dec_expon, extra_digits2, exponent_y, status;
813   int extra_dx, diff_dec2, bin_expon_cx, digits_x, rmode;
814 
815   // CY has more than 16 decimal digits
816 
817   exponent_y = final_exponent_y - extra_digits;
818 
819 #ifdef IEEE_ROUND_NEAREST_TIES_AWAY
820   rounding_mode = 0;
821 #endif
822 #ifdef IEEE_ROUND_NEAREST
823   rounding_mode = 0;
824 #endif
825 
826   if (exponent_x > exponent_y) {
827     // normalize x
828     //--- get number of bits in the coefficients of x and y ---
829     tempx.d = (double) coefficient_x;
830     bin_expon_cx = ((tempx.i & MASK_BINARY_EXPONENT) >> 52) - 0x3ff;
831     // get number of decimal digits in the coeff_x
832     digits_x = estimate_decimal_digits[bin_expon_cx];
833     if (coefficient_x >= power10_table_128[digits_x].w[0])
834       digits_x++;
835 
836     extra_dx = 16 - digits_x;
837     coefficient_x *= power10_table_128[extra_dx].w[0];
838     if ((sign_x ^ sign_y) && (coefficient_x == 1000000000000000ull)) {
839       extra_dx++;
840       coefficient_x = 10000000000000000ull;
841     }
842     exponent_x -= extra_dx;
843 
844     if (exponent_x > exponent_y) {
845 
846       // exponent_x > exponent_y
847       diff_dec_expon = exponent_x - exponent_y;
848 
849       if (exponent_x <= final_exponent_y + 1) {
850           __mul_64x64_to_128 (CX, coefficient_x,
851                                   power10_table_128[diff_dec_expon].w[0]);
852 
853           if (sign_x == sign_y) {
854             __add_128_128 (CT, CY, CX);
855             if ((exponent_x >
856                  final_exponent_y) /*&& (final_exponent_y>0) */ )
857               extra_digits++;
858             if (__unsigned_compare_ge_128
859                 (CT, power10_table_128[16 + extra_digits]))
860               extra_digits++;
861           } else {
862             __sub_128_128 (CT, CY, CX);
863             if (((SINT64) CT.w[1]) < 0) {
864               CT.w[0] = 0 - CT.w[0];
865               CT.w[1] = 0 - CT.w[1];
866               if (CT.w[0])
867                 CT.w[1]--;
868               sign_y = sign_x;
869             } else if (!(CT.w[1] | CT.w[0])) {
870               sign_y =
871                 (rounding_mode !=
872                  ROUNDING_DOWN) ? 0 : 0x8000000000000000ull;
873             }
874             if ((exponent_x + 1 >=
875                  final_exponent_y) /*&& (final_exponent_y>=0) */ ) {
876               extra_digits = __get_dec_digits64 (CT) - 16;
877               if (extra_digits <= 0) {
878                 if (!CT.w[0] && rounding_mode == ROUNDING_DOWN)
879                     sign_y = 0x8000000000000000ull;
880                 return get_BID64 (sign_y, exponent_y, CT.w[0],
881                                         rounding_mode, fpsc);
882               }
883             } else
884               if (__unsigned_compare_gt_128
885                     (power10_table_128[15 + extra_digits], CT))
886               extra_digits--;
887           }
888 
889           return __bid_full_round64 (sign_y, exponent_y, CT, extra_digits,
890                                            rounding_mode, fpsc);
891       }
892       // diff_dec2+extra_digits is the number of digits to eliminate from
893       //                           argument CY
894       diff_dec2 = exponent_x - final_exponent_y;
895 
896       if (diff_dec2 >= 17) {
897 #ifndef IEEE_ROUND_NEAREST
898 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
899           if ((rounding_mode) & 3) {
900             switch (rounding_mode) {
901             case ROUNDING_UP:
902               if (!sign_y) {
903                 D = ((SINT64) (sign_x ^ sign_y)) >> 63;
904                 D = D + D + 1;
905                 coefficient_x += D;
906               }
907               break;
908             case ROUNDING_DOWN:
909               if (sign_y) {
910                 D = ((SINT64) (sign_x ^ sign_y)) >> 63;
911                 D = D + D + 1;
912                 coefficient_x += D;
913               }
914               break;
915             case ROUNDING_TO_ZERO:
916               if (sign_y != sign_x) {
917                 D = 0 - 1;
918                 coefficient_x += D;
919               }
920               break;
921             }
922             if (coefficient_x < 1000000000000000ull) {
923               coefficient_x -= D;
924               coefficient_x =
925                 D + (coefficient_x << 1) + (coefficient_x << 3);
926               exponent_x--;
927             }
928           }
929 #endif
930 #endif
931 #ifdef SET_STATUS_FLAGS
932           if (CY.w[1] | CY.w[0])
933             __set_status_flags (fpsc, INEXACT_EXCEPTION);
934 #endif
935           return get_BID64 (sign_x, exponent_x, coefficient_x,
936                                 rounding_mode, fpsc);
937       }
938       // here exponent_x <= 16+final_exponent_y
939 
940       // truncate CY to 16 dec. digits
941       CYh = __truncate (CY, extra_digits);
942 
943       // get remainder
944       T = power10_table_128[extra_digits].w[0];
945       __mul_64x64_to_64 (CY0L, CYh, T);
946 
947       remainder_y = CY.w[0] - CY0L;
948 
949       // align coeff_x, CYh
950       __mul_64x64_to_128 (CX, coefficient_x,
951                                 power10_table_128[diff_dec2].w[0]);
952 
953       if (sign_x == sign_y) {
954           __add_128_64 (CT, CX, CYh);
955           if (__unsigned_compare_ge_128
956               (CT, power10_table_128[16 + diff_dec2]))
957             diff_dec2++;
958       } else {
959           if (remainder_y)
960             CYh++;
961           __sub_128_64 (CT, CX, CYh);
962           if (__unsigned_compare_gt_128
963               (power10_table_128[15 + diff_dec2], CT))
964             diff_dec2--;
965       }
966 
967       return __bid_full_round64_remainder (sign_x, final_exponent_y, CT,
968                                                      diff_dec2, remainder_y,
969                                                      rounding_mode, fpsc, 0);
970     }
971   }
972   // Here (exponent_x <= exponent_y)
973   {
974     diff_dec_expon = exponent_y - exponent_x;
975 
976     if (diff_dec_expon > MAX_FORMAT_DIGITS) {
977       rmode = rounding_mode;
978 
979       if ((sign_x ^ sign_y)) {
980           if (!CY.w[0])
981             CY.w[1]--;
982           CY.w[0]--;
983           if (__unsigned_compare_gt_128
984               (power10_table_128[15 + extra_digits], CY)) {
985             if (rmode & 3) {
986               extra_digits--;
987               final_exponent_y--;
988             } else {
989               CY.w[0] = 1000000000000000ull;
990               CY.w[1] = 0;
991               extra_digits = 0;
992             }
993           }
994       }
995       __scale128_10 (CY, CY);
996       extra_digits++;
997       CY.w[0] |= 1;
998 
999       return __bid_simple_round64_sticky (sign_y, final_exponent_y, CY,
1000                                                     extra_digits, rmode, fpsc);
1001     }
1002     // apply sign to coeff_x
1003     sign_x ^= sign_y;
1004     sign_x = ((SINT64) sign_x) >> 63;
1005     CX.w[0] = (coefficient_x + sign_x) ^ sign_x;
1006     CX.w[1] = sign_x;
1007 
1008     // check whether CY (rounded to 16 digits) and CX have
1009     //                     any digits in the same position
1010     diff_dec2 = final_exponent_y - exponent_x;
1011 
1012     if (diff_dec2 <= 17) {
1013       // align CY to 10^ex
1014       S = power10_table_128[diff_dec_expon].w[0];
1015       __mul_64x128_short (CY_L, S, CY);
1016 
1017       __add_128_128 (ST, CY_L, CX);
1018       extra_digits2 = __get_dec_digits64 (ST) - 16;
1019       return __bid_full_round64 (sign_y, exponent_x, ST, extra_digits2,
1020                                          rounding_mode, fpsc);
1021     }
1022     // truncate CY to 16 dec. digits
1023     CYh = __truncate (CY, extra_digits);
1024 
1025     // get remainder
1026     T = power10_table_128[extra_digits].w[0];
1027     __mul_64x64_to_64 (CY0L, CYh, T);
1028 
1029     coefficient_y = CY.w[0] - CY0L;
1030     // add rounding constant
1031     rmode = rounding_mode;
1032     if (sign_y && (unsigned) (rmode - 1) < 2)
1033       rmode = 3 - rmode;
1034 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
1035 #ifndef IEEE_ROUND_NEAREST
1036     if (!(rmode & 3))         //ROUNDING_TO_NEAREST
1037 #endif
1038 #endif
1039     {
1040       coefficient_y += round_const_table[rmode][extra_digits];
1041     }
1042     // align coefficient_y,  coefficient_x
1043     S = power10_table_128[diff_dec_expon].w[0];
1044     __mul_64x64_to_128 (F, coefficient_y, S);
1045 
1046     // fraction
1047     __add_128_128 (FS, F, CX);
1048 
1049 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
1050 #ifndef IEEE_ROUND_NEAREST
1051     if (rmode == 0) //ROUNDING_TO_NEAREST
1052 #endif
1053     {
1054       // rounding code, here RN_EVEN
1055       // 10^(extra_digits+diff_dec_expon)
1056       T2 = power10_table_128[diff_dec_expon + extra_digits];
1057       if (__unsigned_compare_gt_128 (FS, T2)
1058             || ((CYh & 1) && __test_equal_128 (FS, T2))) {
1059           CYh++;
1060           __sub_128_128 (FS, FS, T2);
1061       }
1062     }
1063 #endif
1064 #ifndef IEEE_ROUND_NEAREST
1065 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
1066     if (rmode == 4) //ROUNDING_TO_NEAREST
1067 #endif
1068     {
1069       // rounding code, here RN_AWAY
1070       // 10^(extra_digits+diff_dec_expon)
1071       T2 = power10_table_128[diff_dec_expon + extra_digits];
1072       if (__unsigned_compare_ge_128 (FS, T2)) {
1073           CYh++;
1074           __sub_128_128 (FS, FS, T2);
1075       }
1076     }
1077 #endif
1078 #ifndef IEEE_ROUND_NEAREST
1079 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
1080     switch (rmode) {
1081     case ROUNDING_DOWN:
1082     case ROUNDING_TO_ZERO:
1083       if ((SINT64) FS.w[1] < 0) {
1084           CYh--;
1085           if (CYh < 1000000000000000ull) {
1086             CYh = 9999999999999999ull;
1087             final_exponent_y--;
1088           }
1089       } else {
1090           T2 = power10_table_128[diff_dec_expon + extra_digits];
1091           if (__unsigned_compare_ge_128 (FS, T2)) {
1092             CYh++;
1093             __sub_128_128 (FS, FS, T2);
1094           }
1095       }
1096       break;
1097     case ROUNDING_UP:
1098       if ((SINT64) FS.w[1] < 0)
1099           break;
1100       T2 = power10_table_128[diff_dec_expon + extra_digits];
1101       if (__unsigned_compare_gt_128 (FS, T2)) {
1102           CYh += 2;
1103           __sub_128_128 (FS, FS, T2);
1104       } else if ((FS.w[1] == T2.w[1]) && (FS.w[0] == T2.w[0])) {
1105           CYh++;
1106           FS.w[1] = FS.w[0] = 0;
1107       } else if (FS.w[1] | FS.w[0])
1108           CYh++;
1109       break;
1110     }
1111 #endif
1112 #endif
1113 
1114 #ifdef SET_STATUS_FLAGS
1115     status = INEXACT_EXCEPTION;
1116 #ifndef IEEE_ROUND_NEAREST
1117 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
1118     if (!(rmode & 3))
1119 #endif
1120 #endif
1121     {
1122       // RN modes
1123       if ((FS.w[1] ==
1124              round_const_table_128[0][diff_dec_expon + extra_digits].w[1])
1125             && (FS.w[0] ==
1126                 round_const_table_128[0][diff_dec_expon +
1127                                                extra_digits].w[0]))
1128           status = EXACT_STATUS;
1129     }
1130 #ifndef IEEE_ROUND_NEAREST
1131 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
1132     else if (!FS.w[1] && !FS.w[0])
1133       status = EXACT_STATUS;
1134 #endif
1135 #endif
1136 
1137     __set_status_flags (fpsc, status);
1138 #endif
1139 
1140     return get_BID64 (sign_y, final_exponent_y, CYh, rounding_mode,
1141                           fpsc);
1142   }
1143 
1144 }
1145 
1146 //////////////////////////////////////////////////////////////////////////
1147 //
1148 //  If coefficient_z is less than 16 digits long, normalize to 16 digits
1149 //
1150 /////////////////////////////////////////////////////////////////////////
1151 static UINT64
BID_normalize(UINT64 sign_z,int exponent_z,UINT64 coefficient_z,UINT64 round_dir,int round_flag,int rounding_mode,unsigned * fpsc)1152 BID_normalize (UINT64 sign_z, int exponent_z,
1153                  UINT64 coefficient_z, UINT64 round_dir, int round_flag,
1154                  int rounding_mode, unsigned *fpsc) {
1155   SINT64 D;
1156   int_double tempx;
1157   int digits_z, bin_expon, scale, rmode;
1158 
1159 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
1160 #ifndef IEEE_ROUND_NEAREST
1161   rmode = rounding_mode;
1162   if (sign_z && (unsigned) (rmode - 1) < 2)
1163     rmode = 3 - rmode;
1164 #else
1165   if (coefficient_z >= power10_table_128[15].w[0])
1166     return z;
1167 #endif
1168 #endif
1169 
1170   //--- get number of bits in the coefficients of x and y ---
1171   tempx.d = (double) coefficient_z;
1172   bin_expon = ((tempx.i & MASK_BINARY_EXPONENT) >> 52) - 0x3ff;
1173   // get number of decimal digits in the coeff_x
1174   digits_z = estimate_decimal_digits[bin_expon];
1175   if (coefficient_z >= power10_table_128[digits_z].w[0])
1176     digits_z++;
1177 
1178   scale = 16 - digits_z;
1179   exponent_z -= scale;
1180   if (exponent_z < 0) {
1181     scale += exponent_z;
1182     exponent_z = 0;
1183   }
1184   coefficient_z *= power10_table_128[scale].w[0];
1185 
1186 #ifdef SET_STATUS_FLAGS
1187   if (round_flag) {
1188     __set_status_flags (fpsc, INEXACT_EXCEPTION);
1189     if (coefficient_z < 1000000000000000ull)
1190       __set_status_flags (fpsc, UNDERFLOW_EXCEPTION);
1191     else if ((coefficient_z == 1000000000000000ull) && !exponent_z
1192                && ((SINT64) (round_dir ^ sign_z) < 0) && round_flag
1193                && (rmode == ROUNDING_DOWN || rmode == ROUNDING_TO_ZERO))
1194       __set_status_flags (fpsc, UNDERFLOW_EXCEPTION);
1195   }
1196 #endif
1197 
1198 #ifndef IEEE_ROUND_NEAREST_TIES_AWAY
1199 #ifndef IEEE_ROUND_NEAREST
1200   if (round_flag && (rmode & 3)) {
1201     D = round_dir ^ sign_z;
1202 
1203     if (rmode == ROUNDING_UP) {
1204       if (D >= 0)
1205           coefficient_z++;
1206     } else {
1207       if (D < 0)
1208           coefficient_z--;
1209       if (coefficient_z < 1000000000000000ull && exponent_z) {
1210           coefficient_z = 9999999999999999ull;
1211           exponent_z--;
1212       }
1213     }
1214   }
1215 #endif
1216 #endif
1217 
1218   return get_BID64 (sign_z, exponent_z, coefficient_z, rounding_mode,
1219                         fpsc);
1220 }
1221 
1222 
1223 //////////////////////////////////////////////////////////////////////////
1224 //
1225 //    0*10^ey + cz*10^ez,   ey<ez
1226 //
1227 //////////////////////////////////////////////////////////////////////////
1228 
1229 __BID_INLINE__ UINT64
add_zero64(int exponent_y,UINT64 sign_z,int exponent_z,UINT64 coefficient_z,unsigned * prounding_mode,unsigned * fpsc)1230 add_zero64 (int exponent_y, UINT64 sign_z, int exponent_z,
1231               UINT64 coefficient_z, unsigned *prounding_mode,
1232               unsigned *fpsc) {
1233   int_double tempx;
1234   int bin_expon, scale_k, scale_cz;
1235   int diff_expon;
1236 
1237   diff_expon = exponent_z - exponent_y;
1238 
1239   tempx.d = (double) coefficient_z;
1240   bin_expon = ((tempx.i & MASK_BINARY_EXPONENT) >> 52) - 0x3ff;
1241   scale_cz = estimate_decimal_digits[bin_expon];
1242   if (coefficient_z >= power10_table_128[scale_cz].w[0])
1243     scale_cz++;
1244 
1245   scale_k = 16 - scale_cz;
1246   if (diff_expon < scale_k)
1247     scale_k = diff_expon;
1248   coefficient_z *= power10_table_128[scale_k].w[0];
1249 
1250   return get_BID64 (sign_z, exponent_z - scale_k, coefficient_z,
1251                         *prounding_mode, fpsc);
1252 }
1253 #endif
1254