/* origin: FreeBSD /usr/src/lib/msun/src/e_fmod.c */
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunSoft, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
/*
* fmod(x,y)
* Return x mod y in exact arithmetic
* Method: shift and subtract
*/
#include "libm.h"
static const double one = 1.0, Zero[] = {0.0, -0.0,};
double fmod(double x, double y)
{
int32_t n,hx,hy,hz,ix,iy,sx,i;
uint32_t lx,ly,lz;
EXTRACT_WORDS(hx, lx, x);
EXTRACT_WORDS(hy, ly, y);
sx = hx & 0x80000000; /* sign of x */
hx ^= sx; /* |x| */
hy &= 0x7fffffff; /* |y| */
/* purge off exception values */
if ((hy|ly) == 0 || hx >= 0x7ff00000 || /* y=0,or x not finite */
(hy|((ly|-ly)>>31)) > 0x7ff00000) /* or y is NaN */
return (x*y)/(x*y);
if (hx <= hy) {
if (hx < hy || lx < ly) /* |x| < |y| */
return x;
if (lx == ly) /* |x| = |y|, return x*0 */
return Zero[(uint32_t)sx>>31];
}
/* determine ix = ilogb(x) */
if (hx < 0x00100000) { /* subnormal x */
if (hx == 0) {
for (ix = -1043, i = lx; i > 0; i <<= 1)
ix -= 1;
} else {
for (ix = -1022, i = hx<<11; i > 0; i <<= 1)
ix -= 1;
}
} else
ix = (hx>>20) - 1023;
/* determine iy = ilogb(y) */
if (hy < 0x00100000) { /* subnormal y */
if (hy == 0) {
for (iy = -1043, i = ly; i > 0; i <<= 1)
iy -= 1;
} else {
for (iy = -1022, i = hy<<11; i > 0; i <<= 1)
iy -= 1;
}
} else
iy = (hy>>20) - 1023;
/* set up {hx,lx}, {hy,ly} and align y to x */
if (ix >= -1022)
hx = 0x00100000|(0x000fffff&hx);
else { /* subnormal x, shift x to normal */
n = -1022-ix;
if (n <= 31) {
hx = (hx<<n)|(lx>>(32-n));
lx <<= n;
} else {
hx = lx<<(n-32);
lx = 0;
}
}
if(iy >= -1022)
hy = 0x00100000|(0x000fffff&hy);
else { /* subnormal y, shift y to normal */
n = -1022-iy;
if (n <= 31) {
hy = (hy<<n)|(ly>>(32-n));
ly <<= n;
} else {
hy = ly<<(n-32);
ly = 0;
}
}
/* fix point fmod */
n = ix - iy;
while (n--) {
hz = hx-hy;
lz = lx-ly;
if (lx < ly)
hz -= 1;
if (hz < 0) {
hx = hx+hx+(lx>>31);
lx = lx+lx;
} else {
if ((hz|lz) == 0) /* return sign(x)*0 */
return Zero[(uint32_t)sx>>31];
hx = hz+hz+(lz>>31);
lx = lz+lz;
}
}
hz = hx-hy;
lz = lx-ly;
if (lx < ly)
hz -= 1;
if (hz >= 0) {
hx = hz;
lx = lz;
}
/* convert back to floating value and restore the sign */
if ((hx|lx) == 0) /* return sign(x)*0 */
return Zero[(uint32_t)sx>>31];
while (hx < 0x00100000) { /* normalize x */
hx = hx+hx+(lx>>31);
lx = lx+lx;
iy -= 1;
}
if (iy >= -1022) { /* normalize output */
hx = ((hx-0x00100000)|((iy+1023)<<20));
INSERT_WORDS(x, hx|sx, lx);
} else { /* subnormal output */
n = -1022 - iy;
if (n <= 20) {
lx = (lx>>n)|((uint32_t)hx<<(32-n));
hx >>= n;
} else if (n <= 31) {
lx = (hx<<(32-n))|(lx>>n);
hx = sx;
} else {
lx = hx>>(n-32); hx = sx;
}
INSERT_WORDS(x, hx|sx, lx);
x *= one; /* create necessary signal */
}
return x; /* exact output */
}
