1 /* Round argument to nearest integral value according to current rounding
2 direction.
3 Copyright (C) 1997-2022 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
29 static const double two52[2] =
30 {
31 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
32 -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
33 };
34
35
36 long int
__lrint(double x)37 __lrint (double x)
38 {
39 int32_t j0;
40 uint32_t i0, i1;
41 double w;
42 double t;
43 long int result;
44 int sx;
45
46 EXTRACT_WORDS (i0, i1, x);
47 j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
48 sx = i0 >> 31;
49 i0 &= 0xfffff;
50 i0 |= 0x100000;
51
52 if (j0 < 20)
53 {
54 w = math_narrow_eval (two52[sx] + x);
55 t = w - two52[sx];
56 EXTRACT_WORDS (i0, i1, t);
57 j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
58 i0 &= 0xfffff;
59 i0 |= 0x100000;
60
61 result = (j0 < 0 ? 0 : i0 >> (20 - j0));
62 }
63 else if (j0 < (int32_t) (8 * sizeof (long int)) - 1)
64 {
65 if (j0 >= 52)
66 result = ((long int) i0 << (j0 - 20)) | ((long int) i1 << (j0 - 52));
67 else
68 {
69 #if defined FE_INVALID || defined FE_INEXACT
70 /* X < LONG_MAX + 1 implied by J0 < 31. */
71 if (sizeof (long int) == 4
72 && x > (double) LONG_MAX)
73 {
74 /* In the event of overflow we must raise the "invalid"
75 exception, but not "inexact". */
76 t = __nearbyint (x);
77 feraiseexcept (t == LONG_MAX ? FE_INEXACT : FE_INVALID);
78 }
79 else
80 #endif
81 {
82 w = math_narrow_eval (two52[sx] + x);
83 t = w - two52[sx];
84 }
85 EXTRACT_WORDS (i0, i1, t);
86 j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
87 i0 &= 0xfffff;
88 i0 |= 0x100000;
89
90 if (j0 == 20)
91 result = (long int) i0;
92 else
93 result = ((long int) i0 << (j0 - 20)) | (i1 >> (52 - j0));
94 }
95 }
96 else
97 {
98 /* The number is too large. Unless it rounds to LONG_MIN,
99 FE_INVALID must be raised and the return value is
100 unspecified. */
101 #if defined FE_INVALID || defined FE_INEXACT
102 if (sizeof (long int) == 4
103 && x < (double) LONG_MIN
104 && x > (double) LONG_MIN - 1.0)
105 {
106 /* If truncation produces LONG_MIN, the cast will not raise
107 the exception, but may raise "inexact". */
108 t = __nearbyint (x);
109 feraiseexcept (t == LONG_MIN ? FE_INEXACT : FE_INVALID);
110 return LONG_MIN;
111 }
112 else if (FIX_DBL_LONG_CONVERT_OVERFLOW && x != (double) LONG_MIN)
113 {
114 feraiseexcept (FE_INVALID);
115 return sx == 0 ? LONG_MAX : LONG_MIN;
116 }
117 #endif
118 return (long int) x;
119 }
120
121 return sx ? -result : result;
122 }
123
124 libm_alias_double (__lrint, lrint)
125