1/* e_fmodf.c -- float version of e_fmod.c.
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3 */
4
5/*
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8 *
9 * Developed at SunPro, a Sun Microsystems, Inc. business.
10 * Permission to use, copy, modify, and distribute this
11 * software is freely granted, provided that this notice
12 * is preserved.
13 * ====================================================
14 */
15
16#if defined(LIBM_SCCS) && !defined(lint)
17static char rcsid[] = "$NetBSD: e_fmodf.c,v 1.4 1995/05/10 20:45:10 jtc Exp $";
18#endif
19
20/*
21 * __ieee754_fmodf(x,y)
22 * Return x mod y in exact arithmetic
23 * Method: shift and subtract
24 */
25
26#include "math.h"
27#include "math_private.h"
28
29#ifdef __STDC__
30static const float one = 1.0, Zero[] = {0.0, -0.0,};
31#else
32static float one = 1.0, Zero[] = {0.0, -0.0,};
33#endif
34
35#ifdef __STDC__
36	float __ieee754_fmodf(float x, float y)
37#else
38	float __ieee754_fmodf(x,y)
39	float x,y ;
40#endif
41{
42	int32_t n,hx,hy,hz,ix,iy,sx,i;
43
44	GET_FLOAT_WORD(hx,x);
45	GET_FLOAT_WORD(hy,y);
46	sx = hx&0x80000000;		/* sign of x */
47	hx ^=sx;		/* |x| */
48	hy &= 0x7fffffff;	/* |y| */
49
50    /* purge off exception values */
51	if(hy==0||(hx>=0x7f800000)||		/* y=0,or x not finite */
52	   (hy>0x7f800000))			/* or y is NaN */
53	    return (x*y)/(x*y);
54	if(hx<hy) return x;			/* |x|<|y| return x */
55	if(hx==hy)
56	    return Zero[(u_int32_t)sx>>31];	/* |x|=|y| return x*0*/
57
58    /* determine ix = ilogb(x) */
59	if(hx<0x00800000) {	/* subnormal x */
60	    for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1;
61	} else ix = (hx>>23)-127;
62
63    /* determine iy = ilogb(y) */
64	if(hy<0x00800000) {	/* subnormal y */
65	    for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1;
66	} else iy = (hy>>23)-127;
67
68    /* set up {hx,lx}, {hy,ly} and align y to x */
69	if(ix >= -126)
70	    hx = 0x00800000|(0x007fffff&hx);
71	else {		/* subnormal x, shift x to normal */
72	    n = -126-ix;
73	    hx = hx<<n;
74	}
75	if(iy >= -126)
76	    hy = 0x00800000|(0x007fffff&hy);
77	else {		/* subnormal y, shift y to normal */
78	    n = -126-iy;
79	    hy = hy<<n;
80	}
81
82    /* fix point fmod */
83	n = ix - iy;
84	while(n--) {
85	    hz=hx-hy;
86	    if(hz<0){hx = hx+hx;}
87	    else {
88	    	if(hz==0) 		/* return sign(x)*0 */
89		    return Zero[(u_int32_t)sx>>31];
90	    	hx = hz+hz;
91	    }
92	}
93	hz=hx-hy;
94	if(hz>=0) {hx=hz;}
95
96    /* convert back to floating value and restore the sign */
97	if(hx==0) 			/* return sign(x)*0 */
98	    return Zero[(u_int32_t)sx>>31];
99	while(hx<0x00800000) {		/* normalize x */
100	    hx = hx+hx;
101	    iy -= 1;
102	}
103	if(iy>= -126) {		/* normalize output */
104	    hx = ((hx-0x00800000)|((iy+127)<<23));
105	    SET_FLOAT_WORD(x,hx|sx);
106	} else {		/* subnormal output */
107	    n = -126 - iy;
108	    hx >>= n;
109	    SET_FLOAT_WORD(x,hx|sx);
110	    x *= one;		/* create necessary signal */
111	}
112	return x;		/* exact output */
113}
114