1/* Compute remainder and a congruent to the quotient.
2 Copyright (C) 1997-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <math.h>
20
21#include <math_private.h>
22#include <libm-alias-ldouble.h>
23
24
25static const long double zero = 0.0;
26
27
28long double
29__remquol (long double x, long double p, int *quo)
30{
31 int32_t ex,ep,hx,hp;
32 uint32_t sx,lx,lp;
33 int cquo,qs;
34
35 GET_LDOUBLE_WORDS (ex, hx, lx, x);
36 GET_LDOUBLE_WORDS (ep, hp, lp, p);
37 sx = ex & 0x8000;
38 qs = (sx ^ (ep & 0x8000)) >> 15;
39 ep &= 0x7fff;
40 ex &= 0x7fff;
41
42 /* Purge off exception values. */
43 if ((ep | hp | lp) == 0)
44 return (x * p) / (x * p); /* p = 0 */
45 if ((ex == 0x7fff) /* x not finite */
46 || ((ep == 0x7fff) /* p is NaN */
47 && (((hp & 0x7fffffff) | lp) != 0)))
48 return (x * p) / (x * p);
49
50 if (ep <= 0x7ffb)
51 x = __ieee754_fmodl (x, 8 * p); /* now x < 8p */
52
53 if (((ex - ep) | (hx - hp) | (lx - lp)) == 0)
54 {
55 *quo = qs ? -1 : 1;
56 return zero * x;
57 }
58
59 x = fabsl (x);
60 p = fabsl (p);
61 cquo = 0;
62
63 if (ep <= 0x7ffc && x >= 4 * p)
64 {
65 x -= 4 * p;
66 cquo += 4;
67 }
68 if (ep <= 0x7ffd && x >= 2 * p)
69 {
70 x -= 2 * p;
71 cquo += 2;
72 }
73
74 if (ep < 0x0002)
75 {
76 if (x + x > p)
77 {
78 x -= p;
79 ++cquo;
80 if (x + x >= p)
81 {
82 x -= p;
83 ++cquo;
84 }
85 }
86 }
87 else
88 {
89 long double p_half = 0.5 * p;
90 if (x > p_half)
91 {
92 x -= p;
93 ++cquo;
94 if (x >= p_half)
95 {
96 x -= p;
97 ++cquo;
98 }
99 }
100 }
101
102 *quo = qs ? -cquo : cquo;
103
104 /* Ensure correct sign of zero result in round-downward mode. */
105 if (x == 0.0L)
106 x = 0.0L;
107 if (sx)
108 x = -x;
109 return x;
110}
111libm_alias_ldouble (__remquo, remquo)
112