1 /* Round double value to long int.
2 Copyright (C) 1997-2021 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19 #include <fenv.h>
20 #include <limits.h>
21 #include <math.h>
22
23 #include <math_private.h>
24 #include <libm-alias-double.h>
25 #include <fix-fp-int-convert-overflow.h>
26
27 /* For LP64, lround is an alias for llround. */
28 #ifndef _LP64
29
30 long int
__lround(double x)31 __lround (double x)
32 {
33 int32_t j0;
34 int64_t i0;
35 long int result;
36 int sign;
37
38 EXTRACT_WORDS64 (i0, x);
39 j0 = ((i0 >> 52) & 0x7ff) - 0x3ff;
40 sign = i0 < 0 ? -1 : 1;
41 i0 &= UINT64_C(0xfffffffffffff);
42 i0 |= UINT64_C(0x10000000000000);
43
44 if (j0 < (int32_t) (8 * sizeof (long int)) - 1)
45 {
46 if (j0 < 0)
47 return j0 < -1 ? 0 : sign;
48 else if (j0 >= 52)
49 result = i0 << (j0 - 52);
50 else
51 {
52 i0 += UINT64_C(0x8000000000000) >> j0;
53
54 result = i0 >> (52 - j0);
55 #ifdef FE_INVALID
56 if (sizeof (long int) == 4
57 && sign == 1
58 && result == LONG_MIN)
59 /* Rounding brought the value out of range. */
60 feraiseexcept (FE_INVALID);
61 #endif
62 }
63 }
64 else
65 {
66 /* The number is too large. Unless it rounds to LONG_MIN,
67 FE_INVALID must be raised and the return value is
68 unspecified. */
69 #ifdef FE_INVALID
70 if (FIX_DBL_LONG_CONVERT_OVERFLOW
71 && !(sign == -1
72 && (sizeof (long int) == 4
73 ? x > (double) LONG_MIN - 0.5
74 : x >= (double) LONG_MIN)))
75 {
76 feraiseexcept (FE_INVALID);
77 return sign == 1 ? LONG_MAX : LONG_MIN;
78 }
79 else if (!FIX_DBL_LONG_CONVERT_OVERFLOW
80 && sizeof (long int) == 4
81 && x <= (double) LONG_MIN - 0.5)
82 {
83 /* If truncation produces LONG_MIN, the cast will not raise
84 the exception, but may raise "inexact". */
85 feraiseexcept (FE_INVALID);
86 return LONG_MIN;
87 }
88 #endif
89 return (long int) x;
90 }
91
92 return sign * result;
93 }
94
95 libm_alias_double (__lround, lround)
96
97 #endif
98