1 /* @(#)e_fmod.c 1.3 95/01/18 */
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6 * Developed at SunSoft, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
10 * ====================================================
14 #include "math_private.h"
16 static const float Zero[] = {0.0, -0.0,};
19 * Return the IEEE remainder and set *quo to the last n bits of the
20 * quotient, rounded to the nearest integer. We choose n=31 because
21 * we wind up computing all the integer bits of the quotient anyway as
22 * a side-effect of computing the remainder by the shift and subtract
23 * method. In practice, this is far more bits than are needed to use
24 * remquo in reduction algorithms.
27 remquof(float x, float y, int *quo)
29 int32_t n,hx,hy,hz,ix,iy,sx,i;
34 sxy = (hx ^ hy) & 0x80000000;
35 sx = hx&0x80000000; /* sign of x */
37 hy &= 0x7fffffff; /* |y| */
39 /* purge off exception values */
40 if(hy==0||hx>=0x7f800000||hy>0x7f800000) /* y=0,NaN;or x not finite */
44 goto fixup; /* |x|<|y| return x or x-y */
47 return Zero[(uint32_t)sx>>31]; /* |x|=|y| return x*0*/
50 /* determine ix = ilogb(x) */
51 if(hx<0x00800000) { /* subnormal x */
52 for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1;
53 } else ix = (hx>>23)-127;
55 /* determine iy = ilogb(y) */
56 if(hy<0x00800000) { /* subnormal y */
57 for (iy = -126,i=(hy<<8); i>0; i<<=1) iy -=1;
58 } else iy = (hy>>23)-127;
60 /* set up {hx,lx}, {hy,ly} and align y to x */
62 hx = 0x00800000|(0x007fffff&hx);
63 else { /* subnormal x, shift x to normal */
68 hy = 0x00800000|(0x007fffff&hy);
69 else { /* subnormal y, shift y to normal */
79 if(hz<0) hx = hx << 1;
80 else {hx = hz << 1; q++;}
84 if(hz>=0) {hx=hz;q++;}
86 /* convert back to floating value and restore the sign */
87 if(hx==0) { /* return sign(x)*0 */
88 *quo = (sxy ? -q : q);
89 return Zero[(uint32_t)sx>>31];
91 while(hx<0x00800000) { /* normalize x */
95 if(iy>= -126) { /* normalize output */
96 hx = ((hx-0x00800000)|((iy+127)<<23));
97 } else { /* subnormal output */
102 SET_FLOAT_WORD(x,hx);
105 if (x+x>y || (x+x==y && (q & 1))) {
109 } else if (x>0.5f*y || (x==0.5f*y && (q & 1))) {
113 GET_FLOAT_WORD(hx,x);
114 SET_FLOAT_WORD(x,hx^sx);
116 *quo = (sxy ? -q : q);