2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 * Developed at SunPro, a Sun Microsystems, Inc. business.
6 * Permission to use, copy, modify, and distribute this
7 * software is freely granted, provided that this notice
9 * ====================================================
14 * Return x mod y in exact arithmetic
15 * Method: shift and subtract
19 #include "math_private.h"
21 static const double one = 1.0, Zero[] = {0.0, -0.0,};
23 double attribute_hidden __ieee754_fmod(double x, double y)
25 int32_t n,hx,hy,hz,ix,iy,sx,i;
28 EXTRACT_WORDS(hx,lx,x);
29 EXTRACT_WORDS(hy,ly,y);
30 sx = hx&0x80000000; /* sign of x */
32 hy &= 0x7fffffff; /* |y| */
34 /* purge off exception values */
35 if((hy|ly)==0||(hx>=0x7ff00000)|| /* y=0,or x not finite */
36 ((hy|((ly|-ly)>>31))>0x7ff00000)) /* or y is NaN */
39 if((hx<hy)||(lx<ly)) return x; /* |x|<|y| return x */
41 return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/
44 /* determine ix = ilogb(x) */
45 if(hx<0x00100000) { /* subnormal x */
47 for (ix = -1043, i=lx; i>0; i<<=1) ix -=1;
49 for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1;
51 } else ix = (hx>>20)-1023;
53 /* determine iy = ilogb(y) */
54 if(hy<0x00100000) { /* subnormal y */
56 for (iy = -1043, i=ly; i>0; i<<=1) iy -=1;
58 for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1;
60 } else iy = (hy>>20)-1023;
62 /* set up {hx,lx}, {hy,ly} and align y to x */
64 hx = 0x00100000|(0x000fffff&hx);
65 else { /* subnormal x, shift x to normal */
68 hx = (hx<<n)|(lx>>(32-n));
76 hy = 0x00100000|(0x000fffff&hy);
77 else { /* subnormal y, shift y to normal */
80 hy = (hy<<n)|(ly>>(32-n));
91 hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
92 if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;}
94 if((hz|lz)==0) /* return sign(x)*0 */
95 return Zero[(u_int32_t)sx>>31];
96 hx = hz+hz+(lz>>31); lx = lz+lz;
99 hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
100 if(hz>=0) {hx=hz;lx=lz;}
102 /* convert back to floating value and restore the sign */
103 if((hx|lx)==0) /* return sign(x)*0 */
104 return Zero[(u_int32_t)sx>>31];
105 while(hx<0x00100000) { /* normalize x */
106 hx = hx+hx+(lx>>31); lx = lx+lx;
109 if(iy>= -1022) { /* normalize output */
110 hx = ((hx-0x00100000)|((iy+1023)<<20));
111 INSERT_WORDS(x,hx|sx,lx);
112 } else { /* subnormal output */
115 lx = (lx>>n)|((u_int32_t)hx<<(32-n));
118 lx = (hx<<(32-n))|(lx>>n); hx = sx;
120 lx = hx>>(n-32); hx = sx;
122 INSERT_WORDS(x,hx|sx,lx);
123 x *= one; /* create necessary signal */
125 return x; /* exact output */
132 double fmod(double x, double y)
134 double z = __ieee754_fmod(x, y);
135 if (_LIB_VERSION == _IEEE_ || isnan(y) || isnan(x))
138 return __kernel_standard(x, y, 27); /* fmod(x,0) */
142 strong_alias(__ieee754_fmod, fmod)
144 libm_hidden_def(fmod)