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#include <sys/cdefs.h>
17__FBSDID("$FreeBSD$");
18
19/*
20 * __ieee754_fmodf(x,y)
21 * Return x mod y in exact arithmetic
22 * Method: shift and subtract
23 */
24
25#include "math.h"
26#include "math_private.h"
27
28static const float one = 1.0, Zero[] = {0.0, -0.0,};
29
30float
31__ieee754_fmodf(float x, float y)
32{
33	int32_t n,hx,hy,hz,ix,iy,sx,i;
34
35	GET_FLOAT_WORD(hx,x);
36	GET_FLOAT_WORD(hy,y);
37	sx = hx&0x80000000;		/* sign of x */
38	hx ^=sx;		/* |x| */
39	hy &= 0x7fffffff;	/* |y| */
40
41    /* purge off exception values */
42	if(hy==0||(hx>=0x7f800000)||		/* y=0,or x not finite */
43	   (hy>0x7f800000))			/* or y is NaN */
44	    return (x*y)/(x*y);
45	if(hx<hy) return x;			/* |x|<|y| return x */
46	if(hx==hy)
47	    return Zero[(u_int32_t)sx>>31];	/* |x|=|y| return x*0*/
48
49    /* determine ix = ilogb(x) */
50	if(hx<0x00800000) {	/* subnormal x */
51	    for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1;
52	} else ix = (hx>>23)-127;
53
54    /* determine iy = ilogb(y) */
55	if(hy<0x00800000) {	/* subnormal y */
56	    for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1;
57	} else iy = (hy>>23)-127;
58
59    /* set up {hx,lx}, {hy,ly} and align y to x */
60	if(ix >= -126)
61	    hx = 0x00800000|(0x007fffff&hx);
62	else {		/* subnormal x, shift x to normal */
63	    n = -126-ix;
64	    hx = hx<<n;
65	}
66	if(iy >= -126)
67	    hy = 0x00800000|(0x007fffff&hy);
68	else {		/* subnormal y, shift y to normal */
69	    n = -126-iy;
70	    hy = hy<<n;
71	}
72
73    /* fix point fmod */
74	n = ix - iy;
75	while(n--) {
76	    hz=hx-hy;
77	    if(hz<0){hx = hx+hx;}
78	    else {
79	    	if(hz==0) 		/* return sign(x)*0 */
80		    return Zero[(u_int32_t)sx>>31];
81	    	hx = hz+hz;
82	    }
83	}
84	hz=hx-hy;
85	if(hz>=0) {hx=hz;}
86
87    /* convert back to floating value and restore the sign */
88	if(hx==0) 			/* return sign(x)*0 */
89	    return Zero[(u_int32_t)sx>>31];
90	while(hx<0x00800000) {		/* normalize x */
91	    hx = hx+hx;
92	    iy -= 1;
93	}
94	if(iy>= -126) {		/* normalize output */
95	    hx = ((hx-0x00800000)|((iy+127)<<23));
96	    SET_FLOAT_WORD(x,hx|sx);
97	} else {		/* subnormal output */
98	    n = -126 - iy;
99	    hx >>= n;
100	    SET_FLOAT_WORD(x,hx|sx);
101	    x *= one;		/* create necessary signal */
102	}
103	return x;		/* exact output */
104}
105