1/* Round argument to nearest integral value according to current rounding
2 direction.
3 Copyright (C) 1997-2024 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#include <math-use-builtins.h>
29
30
31long long int
32__llrint (double x)
33{
34#if USE_LLRINT_BUILTIN
35 return __builtin_llrint (x);
36#else
37 /* Use generic implementation. */
38 static const double two52[2] =
39 {
40 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
41 -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
42 };
43
44 int32_t j0;
45 uint32_t i1, i0;
46 long long int result;
47 double w;
48 double t;
49 int sx;
50
51 EXTRACT_WORDS (i0, i1, x);
52 j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
53 sx = i0 >> 31;
54 i0 &= 0xfffff;
55 i0 |= 0x100000;
56
57 if (j0 < 20)
58 {
59 w = math_narrow_eval (two52[sx] + x);
60 t = w - two52[sx];
61 EXTRACT_WORDS (i0, i1, t);
62 j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
63 i0 &= 0xfffff;
64 i0 |= 0x100000;
65
66 result = (j0 < 0 ? 0 : i0 >> (20 - j0));
67 }
68 else if (j0 < (int32_t) (8 * sizeof (long long int)) - 1)
69 {
70 if (j0 >= 52)
71 result = (((long long int) i0 << 32) | i1) << (j0 - 52);
72 else
73 {
74 w = math_narrow_eval (two52[sx] + x);
75 t = w - two52[sx];
76 EXTRACT_WORDS (i0, i1, t);
77 j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
78 i0 &= 0xfffff;
79 i0 |= 0x100000;
80
81 if (j0 == 20)
82 result = (long long int) i0;
83 else
84 result = ((long long int) i0 << (j0 - 20)) | (i1 >> (52 - j0));
85 }
86 }
87 else
88 {
89#ifdef FE_INVALID
90 /* The number is too large. Unless it rounds to LLONG_MIN,
91 FE_INVALID must be raised and the return value is
92 unspecified. */
93 if (FIX_DBL_LLONG_CONVERT_OVERFLOW && x != (double) LLONG_MIN)
94 {
95 feraiseexcept (FE_INVALID);
96 return sx == 0 ? LLONG_MAX : LLONG_MIN;
97 }
98#endif
99 return (long long int) x;
100 }
101
102 return sx ? -result : result;
103#endif /* ! USE_LLRINT_BUILTIN */
104}
105
106libm_alias_double (__llrint, llrint)
107

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