1/* Compute remainder and a congruent to the quotient.
2 Copyright (C) 1997-2020 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C Library 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 GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <https://www.gnu.org/licenses/>. */
19
20#include <math.h>
21
22#include <math_private.h>
23#include <libm-alias-double.h>
24#include <stdint.h>
25
26static const double zero = 0.0;
27
28
29double
30__remquo (double x, double y, int *quo)
31{
32 int64_t hx, hy;
33 uint64_t sx, qs;
34 int cquo;
35
36 EXTRACT_WORDS64 (hx, x);
37 EXTRACT_WORDS64 (hy, y);
38 sx = hx & UINT64_C(0x8000000000000000);
39 qs = sx ^ (hy & UINT64_C(0x8000000000000000));
40 hy &= UINT64_C(0x7fffffffffffffff);
41 hx &= UINT64_C(0x7fffffffffffffff);
42
43 /* Purge off exception values. */
44 if (__glibc_unlikely (hy == 0))
45 return (x * y) / (x * y); /* y = 0 */
46 if (__builtin_expect (hx >= UINT64_C(0x7ff0000000000000) /* x not finite */
47 || hy > UINT64_C(0x7ff0000000000000), 0))/* y is NaN */
48 return (x * y) / (x * y);
49
50 if (hy <= UINT64_C(0x7fbfffffffffffff))
51 x = __ieee754_fmod (x, 8 * y); /* now x < 8y */
52
53 if (__glibc_unlikely (hx == hy))
54 {
55 *quo = qs ? -1 : 1;
56 return zero * x;
57 }
58
59 x = fabs (x);
60 INSERT_WORDS64 (y, hy);
61 cquo = 0;
62
63 if (hy <= UINT64_C(0x7fcfffffffffffff) && x >= 4 * y)
64 {
65 x -= 4 * y;
66 cquo += 4;
67 }
68 if (hy <= UINT64_C(0x7fdfffffffffffff) && x >= 2 * y)
69 {
70 x -= 2 * y;
71 cquo += 2;
72 }
73
74 if (hy < UINT64_C(0x0020000000000000))
75 {
76 if (x + x > y)
77 {
78 x -= y;
79 ++cquo;
80 if (x + x >= y)
81 {
82 x -= y;
83 ++cquo;
84 }
85 }
86 }
87 else
88 {
89 double y_half = 0.5 * y;
90 if (x > y_half)
91 {
92 x -= y;
93 ++cquo;
94 if (x >= y_half)
95 {
96 x -= y;
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 == 0.0)
106 x = 0.0;
107 if (sx)
108 x = -x;
109 return x;
110}
111libm_alias_double (__remquo, remquo)
112