1/* Round to int long double floating-point values.
2 IBM extended format long double version.
3 Copyright (C) 2006-2022 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/* This has been coded in assembler because GCC makes such a mess of it
21 when it's coded in C. */
22
23#define NO_MATH_REDIRECT
24#include <math.h>
25#include <fenv.h>
26#include <math-barriers.h>
27#include <math_private.h>
28#include <fenv_private.h>
29#include <math_ldbl_opt.h>
30#include <float.h>
31#include <ieee754.h>
32
33#ifdef USE_AS_NEARBYINTL
34# define rintl nearbyintl
35# define __rintl __nearbyintl
36#endif
37
38
39long double
40__rintl (long double x)
41{
42 double xh, xl, hi, lo;
43
44 ldbl_unpack (x, &xh, &xl);
45
46 /* Return Inf, Nan, +/-0 unchanged. */
47 if (__builtin_expect (xh != 0.0
48 && __builtin_isless (__builtin_fabs (xh),
49 __builtin_inf ()), 1))
50 {
51 double orig_xh;
52 int save_round = fegetround ();
53
54 /* Long double arithmetic, including the canonicalisation below,
55 only works in round-to-nearest mode. */
56#ifdef USE_AS_NEARBYINTL
57 SET_RESTORE_ROUND_NOEX (FE_TONEAREST);
58#else
59 fesetround (FE_TONEAREST);
60#endif
61
62 /* Convert the high double to integer. */
63 orig_xh = xh;
64 hi = ldbl_nearbyint (xh);
65
66 /* Subtract integral high part from the value. If the low double
67 happens to be exactly 0.5 or -0.5, you might think that this
68 subtraction could result in an incorrect conversion. For
69 instance, subtracting an odd number would cause this function
70 to round in the wrong direction. However, if we have a
71 canonical long double with the low double 0.5 or -0.5, then the
72 high double must be even. */
73 xh -= hi;
74 ldbl_canonicalize (&xh, &xl);
75
76 /* Now convert the low double, adjusted for any remainder from the
77 high double. */
78 lo = ldbl_nearbyint (xh);
79
80 xh -= lo;
81 ldbl_canonicalize (&xh, &xl);
82
83 switch (save_round)
84 {
85 case FE_TONEAREST:
86 if (xl > 0.0 && xh == 0.5)
87 lo += 1.0;
88 else if (xl < 0.0 && -xh == 0.5)
89 lo -= 1.0;
90 break;
91
92 case FE_TOWARDZERO:
93 if (orig_xh < 0.0)
94 goto do_up;
95 /* Fall thru */
96
97 case FE_DOWNWARD:
98 if (xh < 0.0 || (xh == 0.0 && xl < 0.0))
99 lo -= 1.0;
100 break;
101
102 case FE_UPWARD:
103 do_up:
104 if (xh > 0.0 || (xh == 0.0 && xl > 0.0))
105 lo += 1.0;
106 break;
107 }
108
109 /* Ensure the final value is canonical. In certain cases,
110 rounding causes hi,lo calculated so far to be non-canonical. */
111 xh = hi;
112 xl = lo;
113 ldbl_canonicalize (&xh, &xl);
114
115 /* Ensure we return -0 rather than +0 when appropriate. */
116 if (orig_xh < 0.0)
117 xh = -__builtin_fabs (xh);
118
119#ifdef USE_AS_NEARBYINTL
120 math_force_eval (xh);
121 math_force_eval (xl);
122#else
123 fesetround (save_round);
124#endif
125 }
126 else
127 /* Quiet signaling NaN arguments. */
128 xh += xh;
129
130 return ldbl_pack (xh, xl);
131}
132
133long_double_symbol (libm, __rintl, rintl);
134

source code of glibc/sysdeps/ieee754/ldbl-128ibm/s_rintl.c