1 /* Round to 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
29 __lrintl (long double x)
30 {
31 double xh, xl;
32 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.
38 We do this because we aren't sure whether that conversion properly
39 raises FE_INVALID. */
40 if (
41 #if __LONG_MAX__ == 2147483647
42 __builtin_expect
43 ((__builtin_fabs (xh) <= (double) __LONG_MAX__ + 2), 1)
44 #else
45 __builtin_expect
46 ((__builtin_fabs (xh) <= -(double) (-__LONG_MAX__ - 1)), 1)
47 #endif
48 #if !defined (FE_INVALID)
49 || 1
50 #endif
51 )
52 {
53 save_round = fegetround ();
54
55 #if __LONG_MAX__ == 2147483647
56 long long llhi = (long long) xh;
57 if (llhi != (long) llhi)
58 hi = llhi < 0 ? -__LONG_MAX__ - 1 : __LONG_MAX__;
59 else
60 hi = llhi;
61 xh -= hi;
62 #else
63 if (__glibc_unlikely ((xh == -(double) (-__LONG_MAX__ - 1))))
64 {
65 /* When XH is 9223372036854775808.0, converting to long long will
66 overflow, resulting in an invalid operation. However, XL might
67 be negative and of sufficient magnitude that the overall long
68 double is in fact in range. Avoid raising an exception. In any
69 case we need to convert this value specially, because
70 the converted value is not exactly represented as a double
71 thus subtracting HI from XH suffers rounding error. */
72 hi = __LONG_MAX__;
73 xh = 1.0;
74 }
75 else
76 {
77 hi = (long) xh;
78 xh -= hi;
79 }
80 #endif
81 ldbl_canonicalize (&xh, &xl);
82
83 lo = (long) xh;
84
85 /* Peg at max/min values, assuming that the above conversions do so.
86 Strictly speaking, we can return anything for values that overflow,
87 but this is more useful. */
88 res = (long int) ((unsigned long int) hi + (unsigned long int) lo);
89
90 /* This is just sign(hi) == sign(lo) && sign(res) != sign(hi). */
91 if (__glibc_unlikely (((~(hi ^ lo) & (res ^ hi)) < 0)))
92 goto overflow;
93
94 xh -= lo;
95 ldbl_canonicalize (&xh, &xl);
96
97 hi = res;
98 switch (save_round)
99 {
100 case FE_TONEAREST:
101 if (fabs (xh) < 0.5
102 || (fabs (xh) == 0.5
103 && ((xh > 0.0 && xl < 0.0)
104 || (xh < 0.0 && xl > 0.0)
105 || (xl == 0.0 && (res & 1) == 0))))
106 return res;
107
108 if (xh < 0.0)
109 res -= 1UL;
110 else
111 res += 1UL;
112 break;
113
114 case FE_TOWARDZERO:
115 if (res > 0 && (xh < 0.0 || (xh == 0.0 && xl < 0.0)))
116 res -= 1UL;
117 else if (res < 0 && (xh > 0.0 || (xh == 0.0 && xl > 0.0)))
118 res += 1UL;
119 return res;
120 break;
121
122 case FE_UPWARD:
123 if (xh > 0.0 || (xh == 0.0 && xl > 0.0))
124 res += 1UL;
125 break;
126
127 case FE_DOWNWARD:
128 if (xh < 0.0 || (xh == 0.0 && xl < 0.0))
129 res -= 1UL;
130 break;
131 }
132
133 if (__glibc_unlikely (((~(hi ^ (res - hi)) & (res ^ hi)) < 0)))
134 goto overflow;
135
136 return res;
137 }
138 else
139 {
140 if (xh > 0.0)
141 hi = __LONG_MAX__;
142 else if (xh < 0.0)
143 hi = -__LONG_MAX__ - 1;
144 else
145 /* Nan */
146 hi = 0;
147 }
148
149 overflow:
150 #ifdef FE_INVALID
151 feraiseexcept (FE_INVALID);
152 #endif
153 return hi;
154 }
155
156 long_double_symbol (libm, __lrintl, lrintl);