1/* Round argument to nearest integral value according to current rounding
2 direction.
3 Copyright (C) 1997-2022 Free Software Foundation, Inc.
4 This file is part of the GNU C Library.
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 <fenv.h>
21#include <limits.h>
22#include <math.h>
23
24#include <math-narrow-eval.h>
25#include <math_private.h>
26#include <libm-alias-double.h>
27#include <fix-fp-int-convert-overflow.h>
28
29static const double two52[2] =
30{
31 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
32 -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
33};
34
35
36long long int
37__llrint (double x)
38{
39 int32_t j0;
40 uint32_t i1, i0;
41 long long int result;
42 double w;
43 double t;
44 int sx;
45
46 EXTRACT_WORDS (i0, i1, x);
47 j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
48 sx = i0 >> 31;
49 i0 &= 0xfffff;
50 i0 |= 0x100000;
51
52 if (j0 < 20)
53 {
54 w = math_narrow_eval (two52[sx] + x);
55 t = w - two52[sx];
56 EXTRACT_WORDS (i0, i1, t);
57 j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
58 i0 &= 0xfffff;
59 i0 |= 0x100000;
60
61 result = (j0 < 0 ? 0 : i0 >> (20 - j0));
62 }
63 else if (j0 < (int32_t) (8 * sizeof (long long int)) - 1)
64 {
65 if (j0 >= 52)
66 result = (((long long int) i0 << 32) | i1) << (j0 - 52);
67 else
68 {
69 w = math_narrow_eval (two52[sx] + x);
70 t = w - two52[sx];
71 EXTRACT_WORDS (i0, i1, t);
72 j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
73 i0 &= 0xfffff;
74 i0 |= 0x100000;
75
76 if (j0 == 20)
77 result = (long long int) i0;
78 else
79 result = ((long long int) i0 << (j0 - 20)) | (i1 >> (52 - j0));
80 }
81 }
82 else
83 {
84#ifdef FE_INVALID
85 /* The number is too large. Unless it rounds to LLONG_MIN,
86 FE_INVALID must be raised and the return value is
87 unspecified. */
88 if (FIX_DBL_LLONG_CONVERT_OVERFLOW && x != (double) LLONG_MIN)
89 {
90 feraiseexcept (FE_INVALID);
91 return sx == 0 ? LLONG_MAX : LLONG_MIN;
92 }
93#endif
94 return (long long int) x;
95 }
96
97 return sx ? -result : result;
98}
99
100libm_alias_double (__llrint, llrint)
101

source code of glibc/sysdeps/ieee754/dbl-64/s_llrint.c