about summary refs log tree commit diff
path: root/sysdeps/ieee754/ldbl-128/e_fmodl.c
blob: b60d3537f82a813c42eb5887a5aecf57fbadc930 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
/* e_fmodl.c -- long double version of e_fmod.c.
 */
/*
 * ====================================================
 * Copyright (C) 1993, 2011 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

/*
 * __ieee754_fmodl(x,y)
 * Return x mod y in exact arithmetic
 * Method: shift and subtract
 */

#include <math.h>
#include <math_private.h>
#include <libm-alias-finite.h>

static const _Float128 one = 1.0, Zero[] = {0.0, -0.0,};

_Float128
__ieee754_fmodl (_Float128 x, _Float128 y)
{
	int64_t n,hx,hy,hz,ix,iy,sx,i;
	uint64_t lx,ly,lz;

	GET_LDOUBLE_WORDS64(hx,lx,x);
	GET_LDOUBLE_WORDS64(hy,ly,y);
	sx = hx&0x8000000000000000ULL;		/* sign of x */
	hx ^=sx;				/* |x| */
	hy &= 0x7fffffffffffffffLL;		/* |y| */

    /* purge off exception values */
	if((hy|ly)==0||(hx>=0x7fff000000000000LL)|| /* y=0,or x not finite */
	  ((hy|((ly|-ly)>>63))>0x7fff000000000000LL))	/* or y is NaN */
	    return (x*y)/(x*y);
	if(hx<=hy) {
	    if((hx<hy)||(lx<ly)) return x;	/* |x|<|y| return x */
	    if(lx==ly)
		return Zero[(uint64_t)sx>>63];	/* |x|=|y| return x*0*/
	}

    /* determine ix = ilogb(x) */
	if(hx<0x0001000000000000LL) {	/* subnormal x */
	    if(hx==0) {
		for (ix = -16431, i=lx; i>0; i<<=1) ix -=1;
	    } else {
		for (ix = -16382, i=hx<<15; i>0; i<<=1) ix -=1;
	    }
	} else ix = (hx>>48)-0x3fff;

    /* determine iy = ilogb(y) */
	if(hy<0x0001000000000000LL) {	/* subnormal y */
	    if(hy==0) {
		for (iy = -16431, i=ly; i>0; i<<=1) iy -=1;
	    } else {
		for (iy = -16382, i=hy<<15; i>0; i<<=1) iy -=1;
	    }
	} else iy = (hy>>48)-0x3fff;

    /* set up {hx,lx}, {hy,ly} and align y to x */
	if(ix >= -16382)
	    hx = 0x0001000000000000LL|(0x0000ffffffffffffLL&hx);
	else {		/* subnormal x, shift x to normal */
	    n = -16382-ix;
	    if(n<=63) {
		hx = (hx<<n)|(lx>>(64-n));
		lx <<= n;
	    } else {
		hx = lx<<(n-64);
		lx = 0;
	    }
	}
	if(iy >= -16382)
	    hy = 0x0001000000000000LL|(0x0000ffffffffffffLL&hy);
	else {		/* subnormal y, shift y to normal */
	    n = -16382-iy;
	    if(n<=63) {
		hy = (hy<<n)|(ly>>(64-n));
		ly <<= n;
	    } else {
		hy = ly<<(n-64);
		ly = 0;
	    }
	}

    /* fix point fmod */
	n = ix - iy;
	while(n--) {
	    hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
	    if(hz<0){hx = hx+hx+(lx>>63); lx = lx+lx;}
	    else {
		if((hz|lz)==0)		/* return sign(x)*0 */
		    return Zero[(uint64_t)sx>>63];
		hx = hz+hz+(lz>>63); lx = lz+lz;
	    }
	}
	hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
	if(hz>=0) {hx=hz;lx=lz;}

    /* convert back to floating value and restore the sign */
	if((hx|lx)==0)			/* return sign(x)*0 */
	    return Zero[(uint64_t)sx>>63];
	while(hx<0x0001000000000000LL) {	/* normalize x */
	    hx = hx+hx+(lx>>63); lx = lx+lx;
	    iy -= 1;
	}
	if(iy>= -16382) {	/* normalize output */
	    hx = ((hx-0x0001000000000000LL)|((iy+16383)<<48));
	    SET_LDOUBLE_WORDS64(x,hx|sx,lx);
	} else {		/* subnormal output */
	    n = -16382 - iy;
	    if(n<=48) {
		lx = (lx>>n)|((uint64_t)hx<<(64-n));
		hx >>= n;
	    } else if (n<=63) {
		lx = (hx<<(64-n))|(lx>>n); hx = sx;
	    } else {
		lx = hx>>(n-64); hx = sx;
	    }
	    SET_LDOUBLE_WORDS64(x,hx|sx,lx);
	    x *= one;		/* create necessary signal */
	}
	return x;		/* exact output */
}
libm_alias_finite (__ieee754_fmodl, __fmodl)