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 <math_private.h>
26#include <math_ldbl_opt.h>
27#include <float.h>
28#include <ieee754.h>
29
30double round (double) asm ("__round");
31
32
33long double
34__roundl (long double x)
35{
36 double xh, xl, hi, lo;
37
38 ldbl_unpack (x, &xh, &xl);
39
40 /* Return Inf, Nan, +/-0 unchanged. */
41 if (__builtin_expect (xh != 0.0
42 && __builtin_isless (__builtin_fabs (xh),
43 __builtin_inf ()), 1))
44 {
45 hi = round (xh);
46 if (hi != xh)
47 {
48 /* The high part is not an integer; the low part only
49 affects the result if the high part is exactly half way
50 between two integers and the low part is nonzero with the
51 opposite sign. */
52 if (fabs (x: hi - xh) == 0.5)
53 {
54 if (xh > 0 && xl < 0)
55 xh = hi - 1;
56 else if (xh < 0 && xl > 0)
57 xh = hi + 1;
58 else
59 xh = hi;
60 }
61 else
62 xh = hi;
63 xl = 0;
64 }
65 else
66 {
67 /* The high part is a nonzero integer. */
68 lo = round (xl);
69 if (fabs (x: lo - xl) == 0.5)
70 {
71 if (xh > 0 && xl < 0)
72 xl = lo + 1;
73 else if (xh < 0 && lo > 0)
74 xl = lo - 1;
75 else
76 xl = lo;
77 }
78 else
79 xl = lo;
80 xh = hi;
81 ldbl_canonicalize_int (&xh, &xl);
82 }
83 }
84 else
85 /* Quiet signaling NaN arguments. */
86 xh += xh;
87
88 return ldbl_pack (xh, xl);
89}
90
91long_double_symbol (libm, __roundl, roundl);
92

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