1/* e_fmodl.c -- long double version of e_fmod.c.
2 */
3/*
4 * ====================================================
5 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6 *
7 * Developed at SunPro, a Sun Microsystems, Inc. business.
8 * Permission to use, copy, modify, and distribute this
9 * software is freely granted, provided that this notice
10 * is preserved.
11 * ====================================================
12 */
13
14/* __ieee754_remainderl(x,p)
15 * Return :
16 * returns x REM p = x - [x/p]*p as if in infinite
17 * precise arithmetic, where [x/p] is the (infinite bit)
18 * integer nearest x/p (in half way case choose the even one).
19 * Method :
20 * Based on fmodl() return x-[x/p]chopped*p exactlp.
21 */
22
23#include <math.h>
24#include <math_private.h>
25#include <libm-alias-finite.h>
26
27static const long double zero = 0.0L;
28
29
30long double
31__ieee754_remainderl(long double x, long double p)
32{
33 int64_t hx,hp;
34 uint64_t sx,lx,lp;
35 long double p_half;
36 double xhi, xlo, phi, plo;
37
38 ldbl_unpack (x, &xhi, &xlo);
39 EXTRACT_WORDS64 (hx, xhi);
40 EXTRACT_WORDS64 (lx, xlo);
41 ldbl_unpack (p, &phi, &plo);
42 EXTRACT_WORDS64 (hp, phi);
43 EXTRACT_WORDS64 (lp, plo);
44 sx = hx&0x8000000000000000ULL;
45 lp ^= hp & 0x8000000000000000ULL;
46 hp &= 0x7fffffffffffffffLL;
47 lx ^= sx;
48 hx &= 0x7fffffffffffffffLL;
49 if (lp == 0x8000000000000000ULL)
50 lp = 0;
51 if (lx == 0x8000000000000000ULL)
52 lx = 0;
53
54 /* purge off exception values */
55 if(hp==0) return (x*p)/(x*p); /* p = 0 */
56 if((hx>=0x7ff0000000000000LL)|| /* x not finite */
57 (hp>0x7ff0000000000000LL)) /* p is NaN */
58 return (x*p)/(x*p);
59
60
61 if (hp<=0x7fdfffffffffffffLL) x = __ieee754_fmodl(x,p+p); /* now x < 2p */
62 if (((hx-hp)|(lx-lp))==0) return zero*x;
63 x = fabsl(x: x);
64 p = fabsl(x: p);
65 if (hp<0x0020000000000000LL) {
66 if(x+x>p) {
67 x-=p;
68 if(x+x>=p) x -= p;
69 }
70 } else {
71 p_half = 0.5L*p;
72 if(x>p_half) {
73 x-=p;
74 if(x>=p_half) x -= p;
75 }
76 }
77 if (sx)
78 x = -x;
79 return x;
80}
81libm_alias_finite (__ieee754_remainderl, __remainderl)
82

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