1/* s_modfl.c -- long double version of s_modf.c.
2 */
3
4/*
5 * ====================================================
6 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
7 *
8 * Developed at SunPro, a Sun Microsystems, Inc. business.
9 * Permission to use, copy, modify, and distribute this
10 * software is freely granted, provided that this notice
11 * is preserved.
12 * ====================================================
13 */
14
15#if defined(LIBM_SCCS) && !defined(lint)
16static char rcsid[] = "$NetBSD: $";
17#endif
18
19/*
20 * modfl(long double x, long double *iptr)
21 * return fraction part of x, and return x's integral part in *iptr.
22 * Method:
23 * Bit twiddling.
24 *
25 * Exception:
26 * No exception.
27 */
28
29#include <math.h>
30#include <math_private.h>
31#include <math_ldbl_opt.h>
32
33static const long double one = 1.0;
34
35long double __modfl(long double x, long double *iptr)
36{
37 int64_t i0,i1,j0;
38 uint64_t i;
39 double xhi, xlo;
40
41 ldbl_unpack (x, &xhi, &xlo);
42 EXTRACT_WORDS64 (i0, xhi);
43 EXTRACT_WORDS64 (i1, xlo);
44 i1 &= 0x000fffffffffffffLL;
45 j0 = ((i0>>52)&0x7ff)-0x3ff; /* exponent of x */
46 if(j0<52) { /* integer part in high x */
47 if(j0<0) { /* |x|<1 */
48 /* *iptr = +-0 */
49 INSERT_WORDS64 (xhi, i0&0x8000000000000000ULL);
50 *iptr = xhi;
51 return x;
52 } else {
53 i = (0x000fffffffffffffLL)>>j0;
54 if(((i0&i)|(i1&0x7fffffffffffffffLL))==0) { /* x is integral */
55 *iptr = x;
56 /* return +-0 */
57 INSERT_WORDS64 (xhi, i0&0x8000000000000000ULL);
58 x = xhi;
59 return x;
60 } else {
61 INSERT_WORDS64 (xhi, i0&(~i));
62 *iptr = xhi;
63 return x - *iptr;
64 }
65 }
66 } else if (j0>103) { /* no fraction part */
67 *iptr = x*one;
68 /* We must handle NaNs separately. */
69 if ((i0 & 0x7fffffffffffffffLL) > 0x7ff0000000000000LL)
70 return x*one;
71 /* return +-0 */
72 INSERT_WORDS64 (xhi, i0&0x8000000000000000ULL);
73 x = xhi;
74 return x;
75 } else { /* fraction part in low x */
76 i = -1ULL>>(j0-52);
77 if((i1&i)==0) { /* x is integral */
78 *iptr = x;
79 /* return +-0 */
80 INSERT_WORDS64 (xhi, i0&0x8000000000000000ULL);
81 x = xhi;
82 return x;
83 } else {
84 INSERT_WORDS64 (xhi, i0);
85 INSERT_WORDS64 (xlo, i1&(~i));
86 *iptr = ldbl_pack (xhi, xlo);
87 return x - *iptr;
88 }
89 }
90}
91#if IS_IN (libm)
92long_double_symbol (libm, __modfl, modfl);
93#else
94long_double_symbol (libc, __modfl, modfl);
95#endif
96

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