2 /* @(#)e_fmod.c 1.3 95/01/18 */
4 * ====================================================
5 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
7 * Developed at SunSoft, a Sun Microsystems, Inc. business.
8 * Permission to use, copy, modify, and distribute this
9 * software is freely granted, provided that this notice
11 * ====================================================
14 #include <sys/cdefs.h>
15 __FBSDID("$FreeBSD$");
19 * Return x mod y in exact arithmetic
20 * Method: shift and subtract
26 #include "math_private.h"
28 static const double one = 1.0, Zero[] = {0.0, -0.0,};
31 __ieee754_fmod(double x, double y)
33 int32_t n,hx,hy,hz,ix,iy,sx,i;
36 EXTRACT_WORDS(hx,lx,x);
37 EXTRACT_WORDS(hy,ly,y);
38 sx = hx&0x80000000; /* sign of x */
40 hy &= 0x7fffffff; /* |y| */
42 /* purge off exception values */
43 if((hy|ly)==0||(hx>=0x7ff00000)|| /* y=0,or x not finite */
44 ((hy|((ly|-ly)>>31))>0x7ff00000)) /* or y is NaN */
47 if((hx<hy)||(lx<ly)) return x; /* |x|<|y| return x */
49 return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/
52 /* determine ix = ilogb(x) */
53 if(hx<0x00100000) { /* subnormal x */
55 for (ix = -1043, i=lx; i>0; i<<=1) ix -=1;
57 for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1;
59 } else ix = (hx>>20)-1023;
61 /* determine iy = ilogb(y) */
62 if(hy<0x00100000) { /* subnormal y */
64 for (iy = -1043, i=ly; i>0; i<<=1) iy -=1;
66 for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1;
68 } else iy = (hy>>20)-1023;
70 /* set up {hx,lx}, {hy,ly} and align y to x */
72 hx = 0x00100000|(0x000fffff&hx);
73 else { /* subnormal x, shift x to normal */
76 hx = (hx<<n)|(lx>>(32-n));
84 hy = 0x00100000|(0x000fffff&hy);
85 else { /* subnormal y, shift y to normal */
88 hy = (hy<<n)|(ly>>(32-n));
99 hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
100 if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;}
102 if((hz|lz)==0) /* return sign(x)*0 */
103 return Zero[(u_int32_t)sx>>31];
104 hx = hz+hz+(lz>>31); lx = lz+lz;
107 hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
108 if(hz>=0) {hx=hz;lx=lz;}
110 /* convert back to floating value and restore the sign */
111 if((hx|lx)==0) /* return sign(x)*0 */
112 return Zero[(u_int32_t)sx>>31];
113 while(hx<0x00100000) { /* normalize x */
114 hx = hx+hx+(lx>>31); lx = lx+lx;
117 if(iy>= -1022) { /* normalize output */
118 hx = ((hx-0x00100000)|((iy+1023)<<20));
119 INSERT_WORDS(x,hx|sx,lx);
120 } else { /* subnormal output */
123 lx = (lx>>n)|((u_int32_t)hx<<(32-n));
126 lx = (hx<<(32-n))|(lx>>n); hx = sx;
128 lx = hx>>(n-32); hx = sx;
130 INSERT_WORDS(x,hx|sx,lx);
131 x *= one; /* create necessary signal */
133 return x; /* exact output */
136 #if (LDBL_MANT_DIG == 53)
137 __weak_reference(fmod, fmodl);