1*2fe8fb19SBen Gras /* e_fmodf.c -- float version of e_fmod.c.
2*2fe8fb19SBen Gras * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3*2fe8fb19SBen Gras */
4*2fe8fb19SBen Gras
5*2fe8fb19SBen Gras /*
6*2fe8fb19SBen Gras * ====================================================
7*2fe8fb19SBen Gras * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8*2fe8fb19SBen Gras *
9*2fe8fb19SBen Gras * Developed at SunPro, a Sun Microsystems, Inc. business.
10*2fe8fb19SBen Gras * Permission to use, copy, modify, and distribute this
11*2fe8fb19SBen Gras * software is freely granted, provided that this notice
12*2fe8fb19SBen Gras * is preserved.
13*2fe8fb19SBen Gras * ====================================================
14*2fe8fb19SBen Gras */
15*2fe8fb19SBen Gras
16*2fe8fb19SBen Gras #include <sys/cdefs.h>
17*2fe8fb19SBen Gras #if defined(LIBM_SCCS) && !defined(lint)
18*2fe8fb19SBen Gras __RCSID("$NetBSD: e_fmodf.c,v 1.7 2002/05/26 22:01:49 wiz Exp $");
19*2fe8fb19SBen Gras #endif
20*2fe8fb19SBen Gras
21*2fe8fb19SBen Gras /*
22*2fe8fb19SBen Gras * __ieee754_fmodf(x,y)
23*2fe8fb19SBen Gras * Return x mod y in exact arithmetic
24*2fe8fb19SBen Gras * Method: shift and subtract
25*2fe8fb19SBen Gras */
26*2fe8fb19SBen Gras
27*2fe8fb19SBen Gras #include "math.h"
28*2fe8fb19SBen Gras #include "math_private.h"
29*2fe8fb19SBen Gras
30*2fe8fb19SBen Gras static const float one = 1.0, Zero[] = {0.0, -0.0,};
31*2fe8fb19SBen Gras
32*2fe8fb19SBen Gras float
__ieee754_fmodf(float x,float y)33*2fe8fb19SBen Gras __ieee754_fmodf(float x, float y)
34*2fe8fb19SBen Gras {
35*2fe8fb19SBen Gras int32_t n,hx,hy,hz,ix,iy,sx,i;
36*2fe8fb19SBen Gras
37*2fe8fb19SBen Gras GET_FLOAT_WORD(hx,x);
38*2fe8fb19SBen Gras GET_FLOAT_WORD(hy,y);
39*2fe8fb19SBen Gras sx = hx&0x80000000; /* sign of x */
40*2fe8fb19SBen Gras hx ^=sx; /* |x| */
41*2fe8fb19SBen Gras hy &= 0x7fffffff; /* |y| */
42*2fe8fb19SBen Gras
43*2fe8fb19SBen Gras /* purge off exception values */
44*2fe8fb19SBen Gras if(hy==0||(hx>=0x7f800000)|| /* y=0,or x not finite */
45*2fe8fb19SBen Gras (hy>0x7f800000)) /* or y is NaN */
46*2fe8fb19SBen Gras return (x*y)/(x*y);
47*2fe8fb19SBen Gras if(hx<hy) return x; /* |x|<|y| return x */
48*2fe8fb19SBen Gras if(hx==hy)
49*2fe8fb19SBen Gras return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/
50*2fe8fb19SBen Gras
51*2fe8fb19SBen Gras /* determine ix = ilogb(x) */
52*2fe8fb19SBen Gras if(hx<0x00800000) { /* subnormal x */
53*2fe8fb19SBen Gras for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1;
54*2fe8fb19SBen Gras } else ix = (hx>>23)-127;
55*2fe8fb19SBen Gras
56*2fe8fb19SBen Gras /* determine iy = ilogb(y) */
57*2fe8fb19SBen Gras if(hy<0x00800000) { /* subnormal y */
58*2fe8fb19SBen Gras for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1;
59*2fe8fb19SBen Gras } else iy = (hy>>23)-127;
60*2fe8fb19SBen Gras
61*2fe8fb19SBen Gras /* set up {hx,lx}, {hy,ly} and align y to x */
62*2fe8fb19SBen Gras if(ix >= -126)
63*2fe8fb19SBen Gras hx = 0x00800000|(0x007fffff&hx);
64*2fe8fb19SBen Gras else { /* subnormal x, shift x to normal */
65*2fe8fb19SBen Gras n = -126-ix;
66*2fe8fb19SBen Gras hx = hx<<n;
67*2fe8fb19SBen Gras }
68*2fe8fb19SBen Gras if(iy >= -126)
69*2fe8fb19SBen Gras hy = 0x00800000|(0x007fffff&hy);
70*2fe8fb19SBen Gras else { /* subnormal y, shift y to normal */
71*2fe8fb19SBen Gras n = -126-iy;
72*2fe8fb19SBen Gras hy = hy<<n;
73*2fe8fb19SBen Gras }
74*2fe8fb19SBen Gras
75*2fe8fb19SBen Gras /* fix point fmod */
76*2fe8fb19SBen Gras n = ix - iy;
77*2fe8fb19SBen Gras while(n--) {
78*2fe8fb19SBen Gras hz=hx-hy;
79*2fe8fb19SBen Gras if(hz<0){hx = hx+hx;}
80*2fe8fb19SBen Gras else {
81*2fe8fb19SBen Gras if(hz==0) /* return sign(x)*0 */
82*2fe8fb19SBen Gras return Zero[(u_int32_t)sx>>31];
83*2fe8fb19SBen Gras hx = hz+hz;
84*2fe8fb19SBen Gras }
85*2fe8fb19SBen Gras }
86*2fe8fb19SBen Gras hz=hx-hy;
87*2fe8fb19SBen Gras if(hz>=0) {hx=hz;}
88*2fe8fb19SBen Gras
89*2fe8fb19SBen Gras /* convert back to floating value and restore the sign */
90*2fe8fb19SBen Gras if(hx==0) /* return sign(x)*0 */
91*2fe8fb19SBen Gras return Zero[(u_int32_t)sx>>31];
92*2fe8fb19SBen Gras while(hx<0x00800000) { /* normalize x */
93*2fe8fb19SBen Gras hx = hx+hx;
94*2fe8fb19SBen Gras iy -= 1;
95*2fe8fb19SBen Gras }
96*2fe8fb19SBen Gras if(iy>= -126) { /* normalize output */
97*2fe8fb19SBen Gras hx = ((hx-0x00800000)|((iy+127)<<23));
98*2fe8fb19SBen Gras SET_FLOAT_WORD(x,hx|sx);
99*2fe8fb19SBen Gras } else { /* subnormal output */
100*2fe8fb19SBen Gras n = -126 - iy;
101*2fe8fb19SBen Gras hx >>= n;
102*2fe8fb19SBen Gras SET_FLOAT_WORD(x,hx|sx);
103*2fe8fb19SBen Gras x *= one; /* create necessary signal */
104*2fe8fb19SBen Gras }
105*2fe8fb19SBen Gras return x; /* exact output */
106*2fe8fb19SBen Gras }
107