1 /* Round argument to nearest integral value according to current rounding
2 direction.
3 Copyright (C) 1997-2023 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 <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 #include <math-use-builtins.h>
29
30
31 long int
32 __lrint (double x)
33 {
34 #if USE_LRINT_BUILTIN
35 return __builtin_lrint (x);
36 #else
37 /* Use generic implementation. */
38 static const double two52[2] =
39 {
40 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
41 -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
42 };
43
44 int32_t j0;
45 uint32_t i0, i1;
46 double w;
47 double t;
48 long int result;
49 int sx;
50
51 EXTRACT_WORDS (i0, i1, x);
52 j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
53 sx = i0 >> 31;
54 i0 &= 0xfffff;
55 i0 |= 0x100000;
56
57 if (j0 < 20)
58 {
59 w = math_narrow_eval (two52[sx] + x);
60 t = w - two52[sx];
61 EXTRACT_WORDS (i0, i1, t);
62 j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
63 i0 &= 0xfffff;
64 i0 |= 0x100000;
65
66 result = (j0 < 0 ? 0 : i0 >> (20 - j0));
67 }
68 else if (j0 < (int32_t) (8 * sizeof (long int)) - 1)
69 {
70 if (j0 >= 52)
71 result = ((long int) i0 << (j0 - 20)) | ((long int) i1 << (j0 - 52));
72 else
73 {
74 #if defined FE_INVALID || defined FE_INEXACT
75 /* X < LONG_MAX + 1 implied by J0 < 31. */
76 if (sizeof (long int) == 4
77 && x > (double) LONG_MAX)
78 {
79 /* In the event of overflow we must raise the "invalid"
80 exception, but not "inexact". */
81 t = __nearbyint (x);
82 feraiseexcept (t == LONG_MAX ? FE_INEXACT : FE_INVALID);
83 }
84 else
85 #endif
86 {
87 w = math_narrow_eval (two52[sx] + x);
88 t = w - two52[sx];
89 }
90 EXTRACT_WORDS (i0, i1, t);
91 j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
92 i0 &= 0xfffff;
93 i0 |= 0x100000;
94
95 if (j0 == 20)
96 result = (long int) i0;
97 else
98 result = ((long int) i0 << (j0 - 20)) | (i1 >> (52 - j0));
99 }
100 }
101 else
102 {
103 /* The number is too large. Unless it rounds to LONG_MIN,
104 FE_INVALID must be raised and the return value is
105 unspecified. */
106 #if defined FE_INVALID || defined FE_INEXACT
107 if (sizeof (long int) == 4
108 && x < (double) LONG_MIN
109 && x > (double) LONG_MIN - 1.0)
110 {
111 /* If truncation produces LONG_MIN, the cast will not raise
112 the exception, but may raise "inexact". */
113 t = __nearbyint (x);
114 feraiseexcept (t == LONG_MIN ? FE_INEXACT : FE_INVALID);
115 return LONG_MIN;
116 }
117 else if (FIX_DBL_LONG_CONVERT_OVERFLOW && x != (double) LONG_MIN)
118 {
119 feraiseexcept (FE_INVALID);
120 return sx == 0 ? LONG_MAX : LONG_MIN;
121 }
122 #endif
123 return (long int) x;
124 }
125
126 return sx ? -result : result;
127 #endif /* ! USE_LRINT_BUILTIN */
128 }
129
130 libm_alias_double (__lrint, lrint)