1 /* Round to long long int long double floating-point values.
2 IBM extended format long double version.
3 Copyright (C) 2006-2023 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
27
28 long long
29 __llrintl (long double x)
30 {
31 double xh, xl;
32 long long res, hi, lo;
33 int save_round;
34
35 ldbl_unpack (x, &xh, &xl);
36
37 /* Limit the range of values handled by the conversion to long long.
38 We do this because we aren't sure whether that conversion properly
39 raises FE_INVALID. */
40 if (__builtin_expect
41 ((__builtin_fabs (xh) <= -(double) (-__LONG_LONG_MAX__ - 1)), 1)
42 #if !defined (FE_INVALID)
43 || 1
44 #endif
45 )
46 {
47 save_round = fegetround ();
48
49 if (__glibc_unlikely ((xh == -(double) (-__LONG_LONG_MAX__ - 1))))
50 {
51 /* When XH is 9223372036854775808.0, converting to long long will
52 overflow, resulting in an invalid operation. However, XL might
53 be negative and of sufficient magnitude that the overall long
54 double is in fact in range. Avoid raising an exception. In any
55 case we need to convert this value specially, because
56 the converted value is not exactly represented as a double
57 thus subtracting HI from XH suffers rounding error. */
58 hi = __LONG_LONG_MAX__;
59 xh = 1.0;
60 }
61 else
62 {
63 hi = (long long) xh;
64 xh -= hi;
65 }
66 ldbl_canonicalize (&xh, &xl);
67
68 lo = (long long) xh;
69
70 /* Peg at max/min values, assuming that the above conversions do so.
71 Strictly speaking, we can return anything for values that overflow,
72 but this is more useful. */
73 res = hi + lo;
74
75 /* This is just sign(hi) == sign(lo) && sign(res) != sign(hi). */
76 if (__glibc_unlikely (((~(hi ^ lo) & (res ^ hi)) < 0)))
77 goto overflow;
78
79 xh -= lo;
80 ldbl_canonicalize (&xh, &xl);
81
82 hi = res;
83 switch (save_round)
84 {
85 case FE_TONEAREST:
86 if (fabs (xh) < 0.5
87 || (fabs (xh) == 0.5
88 && ((xh > 0.0 && xl < 0.0)
89 || (xh < 0.0 && xl > 0.0)
90 || (xl == 0.0 && (res & 1) == 0))))
91 return res;
92
93 if (xh < 0.0)
94 res -= 1;
95 else
96 res += 1;
97 break;
98
99 case FE_TOWARDZERO:
100 if (res > 0 && (xh < 0.0 || (xh == 0.0 && xl < 0.0)))
101 res -= 1;
102 else if (res < 0 && (xh > 0.0 || (xh == 0.0 && xl > 0.0)))
103 res += 1;
104 return res;
105 break;
106
107 case FE_UPWARD:
108 if (xh > 0.0 || (xh == 0.0 && xl > 0.0))
109 res += 1;
110 break;
111
112 case FE_DOWNWARD:
113 if (xh < 0.0 || (xh == 0.0 && xl < 0.0))
114 res -= 1;
115 break;
116 }
117
118 if (__glibc_unlikely (((~(hi ^ (res - hi)) & (res ^ hi)) < 0)))
119 goto overflow;
120
121 return res;
122 }
123 else
124 {
125 if (xh > 0.0)
126 hi = __LONG_LONG_MAX__;
127 else if (xh < 0.0)
128 hi = -__LONG_LONG_MAX__ - 1;
129 else
130 /* Nan */
131 hi = 0;
132 }
133
134 overflow:
135 #ifdef FE_INVALID
136 feraiseexcept (FE_INVALID);
137 #endif
138 return hi;
139 }
140
141 long_double_symbol (libm, __llrintl, llrintl);