1/* Compute remainder and a congruent to the quotient.
2 Copyright (C) 1997-2017 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 <http://www.gnu.org/licenses/>. */
19
20#include <math.h>
21
22#include <math_private.h>
23#include <stdint.h>
24
25static const double zero = 0.0;
26
27
28double
29__remquo (double x, double y, int *quo)
30{
31 int64_t hx, hy;
32 uint64_t sx, qs;
33 int cquo;
34
35 EXTRACT_WORDS64 (hx, x);
36 EXTRACT_WORDS64 (hy, y);
37 sx = hx & UINT64_C(0x8000000000000000);
38 qs = sx ^ (hy & UINT64_C(0x8000000000000000));
39 hy &= UINT64_C(0x7fffffffffffffff);
40 hx &= UINT64_C(0x7fffffffffffffff);
41
42 /* Purge off exception values. */
43 if (__glibc_unlikely (hy == 0))
44 return (x * y) / (x * y); /* y = 0 */
45 if (__builtin_expect (hx >= UINT64_C(0x7ff0000000000000) /* x not finite */
46 || hy > UINT64_C(0x7ff0000000000000), 0))/* y is NaN */
47 return (x * y) / (x * y);
48
49 if (hy <= UINT64_C(0x7fbfffffffffffff))
50 x = __ieee754_fmod (x, 8 * y); /* now x < 8y */
51
52 if (__glibc_unlikely (hx == hy))
53 {
54 *quo = qs ? -1 : 1;
55 return zero * x;
56 }
57
58 x = fabs (x);
59 INSERT_WORDS64 (y, hy);
60 cquo = 0;
61
62 if (hy <= UINT64_C(0x7fcfffffffffffff) && x >= 4 * y)
63 {
64 x -= 4 * y;
65 cquo += 4;
66 }
67 if (hy <= UINT64_C(0x7fdfffffffffffff) && x >= 2 * y)
68 {
69 x -= 2 * y;
70 cquo += 2;
71 }
72
73 if (hy < UINT64_C(0x0020000000000000))
74 {
75 if (x + x > y)
76 {
77 x -= y;
78 ++cquo;
79 if (x + x >= y)
80 {
81 x -= y;
82 ++cquo;
83 }
84 }
85 }
86 else
87 {
88 double y_half = 0.5 * y;
89 if (x > y_half)
90 {
91 x -= y;
92 ++cquo;
93 if (x >= y_half)
94 {
95 x -= y;
96 ++cquo;
97 }
98 }
99 }
100
101 *quo = qs ? -cquo : cquo;
102
103 /* Ensure correct sign of zero result in round-downward mode. */
104 if (x == 0.0)
105 x = 0.0;
106 if (sx)
107 x = -x;
108 return x;
109}
110weak_alias (__remquo, remquo)
111#ifdef NO_LONG_DOUBLE
112strong_alias (__remquo, __remquol)
113weak_alias (__remquo, remquol)
114#endif
115