1 /* mpfr_ui_div -- divide a machine integer by a floating-point number
2
3 Copyright 2000-2023 Free Software Foundation, Inc.
4 Contributed by the AriC and Caramba projects, INRIA.
5
6 This file is part of the GNU MPFR Library.
7
8 The GNU MPFR Library is free software; you can redistribute it and/or modify
9 it under the terms of the GNU Lesser General Public License as published by
10 the Free Software Foundation; either version 3 of the License, or (at your
11 option) any later version.
12
13 The GNU MPFR Library is distributed in the hope that it will be useful, but
14 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
15 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
16 License for more details.
17
18 You should have received a copy of the GNU Lesser General Public License
19 along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see
20 https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
21 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
22
23
24 #define MPFR_NEED_LONGLONG_H
25 #include "mpfr-impl.h"
26
27 int
mpfr_ui_div(mpfr_ptr y,unsigned long int u,mpfr_srcptr x,mpfr_rnd_t rnd_mode)28 mpfr_ui_div (mpfr_ptr y, unsigned long int u, mpfr_srcptr x, mpfr_rnd_t rnd_mode)
29 {
30 MPFR_LOG_FUNC
31 (("u=%lu x[%Pd]=%.*Rg rnd=%d",
32 u, mpfr_get_prec(x), mpfr_log_prec, x, rnd_mode),
33 ("y[%Pd]=%.*Rg", mpfr_get_prec(y), mpfr_log_prec, y));
34
35 if (MPFR_UNLIKELY(MPFR_IS_SINGULAR(x)))
36 {
37 if (MPFR_IS_NAN(x))
38 {
39 MPFR_SET_NAN(y);
40 MPFR_RET_NAN;
41 }
42 else if (MPFR_IS_INF(x)) /* u/Inf = 0 */
43 {
44 MPFR_SET_ZERO(y);
45 MPFR_SET_SAME_SIGN(y,x);
46 MPFR_RET(0);
47 }
48 else /* u / 0 */
49 {
50 MPFR_ASSERTD(MPFR_IS_ZERO(x));
51 if (u)
52 {
53 /* u > 0, so y = sign(x) * Inf */
54 MPFR_SET_SAME_SIGN(y, x);
55 MPFR_SET_INF(y);
56 MPFR_SET_DIVBY0 ();
57 MPFR_RET(0);
58 }
59 else
60 {
61 /* 0 / 0 */
62 MPFR_SET_NAN(y);
63 MPFR_RET_NAN;
64 }
65 }
66 }
67 else if (MPFR_LIKELY(u != 0))
68 {
69 int inex;
70 MPFR_SAVE_EXPO_DECL (expo);
71
72 /* Optimization note: Exponent save/restore operations may be
73 removed if mpfr_div works even when uu is out-of-range. */
74 MPFR_SAVE_EXPO_MARK (expo);
75
76 #ifdef MPFR_LONG_WITHIN_LIMB
77 {
78 mpfr_t uu;
79 mp_limb_t up[1];
80 int cnt;
81
82 MPFR_TMP_INIT1(up, uu, GMP_NUMB_BITS);
83 MPFR_ASSERTN(u == (mp_limb_t) u);
84 count_leading_zeros(cnt, (mp_limb_t) u);
85 up[0] = (mp_limb_t) u << cnt;
86
87 MPFR_SET_EXP (uu, GMP_NUMB_BITS - cnt);
88 inex = mpfr_div (y, uu, x, rnd_mode);
89 }
90 #else
91 {
92 mpfr_t uu;
93
94 mpfr_init2 (uu, sizeof (unsigned long) * CHAR_BIT);
95 mpfr_set_ui (uu, u, MPFR_RNDZ);
96 inex = mpfr_div (y, uu, x, rnd_mode);
97 mpfr_clear (uu);
98 }
99 #endif
100
101 MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, __gmpfr_flags);
102 MPFR_SAVE_EXPO_FREE (expo);
103 return mpfr_check_range (y, inex, rnd_mode);
104 }
105 else /* u = 0, and x != 0 */
106 {
107 MPFR_SET_ZERO(y); /* if u=0, then set y to 0 */
108 MPFR_SET_SAME_SIGN(y, x); /* u considered as +0: sign(+0/x) = sign(x) */
109 MPFR_RET(0);
110 }
111 }
112