1/* Round to long int long double floating-point values.
2 IBM extended format long double version.
3 Copyright (C) 2006-2024 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 <math.h>
21#include <fenv.h>
22#include <math_private.h>
23#include <math_ldbl_opt.h>
24#include <float.h>
25#include <ieee754.h>
26
27long
28__lroundl (long double x)
29{
30 double xh, xl;
31 long res, hi, lo;
32
33 ldbl_unpack (x, &xh, &xl);
34
35 /* Limit the range of values handled by the conversion to long.
36 We do this because we aren't sure whether that conversion properly
37 raises FE_INVALID. */
38 if (
39#if __LONG_MAX__ == 2147483647
40 __builtin_expect
41 ((__builtin_fabs (xh) <= (double) __LONG_MAX__ + 2), 1)
42#else
43 __builtin_expect
44 ((__builtin_fabs (xh) <= -(double) (-__LONG_MAX__ - 1)), 1)
45#endif
46#if !defined (FE_INVALID)
47 || 1
48#endif
49 )
50 {
51#if __LONG_MAX__ == 2147483647
52 long long llhi = (long long) xh;
53 if (llhi != (long) llhi)
54 hi = llhi < 0 ? -__LONG_MAX__ - 1 : __LONG_MAX__;
55 else
56 hi = llhi;
57 xh -= hi;
58#else
59 if (__glibc_unlikely ((xh == -(double) (-__LONG_MAX__ - 1))))
60 {
61 /* When XH is 9223372036854775808.0, converting to long long will
62 overflow, resulting in an invalid operation. However, XL might
63 be negative and of sufficient magnitude that the overall long
64 double is in fact in range. Avoid raising an exception. In any
65 case we need to convert this value specially, because
66 the converted value is not exactly represented as a double
67 thus subtracting HI from XH suffers rounding error. */
68 hi = __LONG_MAX__;
69 xh = 1.0;
70 }
71 else
72 {
73 hi = (long) xh;
74 xh -= hi;
75 }
76#endif
77 ldbl_canonicalize (&xh, &xl);
78
79 lo = (long) xh;
80
81 /* Peg at max/min values, assuming that the above conversions do so.
82 Strictly speaking, we can return anything for values that overflow,
83 but this is more useful. */
84 res = (long int) ((unsigned long int) hi + (unsigned long int) lo);
85
86 /* This is just sign(hi) == sign(lo) && sign(res) != sign(hi). */
87 if (__glibc_unlikely (((~(hi ^ lo) & (res ^ hi)) < 0)))
88 goto overflow;
89
90 xh -= lo;
91 ldbl_canonicalize (&xh, &xl);
92
93 hi = res;
94 if (xh > 0.5)
95 {
96 res += 1UL;
97 }
98 else if (xh == 0.5)
99 {
100 if (xl > 0.0 || (xl == 0.0 && res >= 0))
101 res += 1UL;
102 }
103 else if (-xh > 0.5)
104 {
105 res -= 1UL;
106 }
107 else if (-xh == 0.5)
108 {
109 if (xl < 0.0 || (xl == 0.0 && res <= 0))
110 res -= 1UL;
111 }
112
113 if (__glibc_unlikely (((~(hi ^ (res - hi)) & (res ^ hi)) < 0)))
114 goto overflow;
115
116 return res;
117 }
118 else
119 {
120 if (xh > 0.0)
121 hi = __LONG_MAX__;
122 else if (xh < 0.0)
123 hi = -__LONG_MAX__ - 1;
124 else
125 /* Nan */
126 hi = 0;
127 }
128
129overflow:
130#ifdef FE_INVALID
131 feraiseexcept (FE_INVALID);
132#endif
133 return hi;
134}
135
136long_double_symbol (libm, __lroundl, lroundl);
137

source code of glibc/sysdeps/ieee754/ldbl-128ibm/s_lroundl.c