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/* origin: FreeBSD /usr/src/lib/msun/src/s_remquof.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.
* ====================================================
*/
/*
* Return the IEEE remainder and set *quo to the last n bits of the
* quotient, rounded to the nearest integer. We choose n=31 because
* we wind up computing all the integer bits of the quotient anyway as
* a side-effect of computing the remainder by the shift and subtract
* method. In practice, this is far more bits than are needed to use
* remquo in reduction algorithms.
*/
#include "libm.h"
static const float Zero[] = {0.0, -0.0,};
float remquof(float x, float y, int *quo)
{
int32_t n,hx,hy,hz,ix,iy,sx,i;
uint32_t q,sxy;
GET_FLOAT_WORD(hx, x);
GET_FLOAT_WORD(hy, y);
sxy = (hx ^ hy) & 0x80000000;
sx = hx & 0x80000000; /* sign of x */
hx ^= sx; /* |x| */
hy &= 0x7fffffff; /* |y| */
/* purge off exception values */
if (hy == 0 || hx >= 0x7f800000 || hy > 0x7f800000) /* y=0,NaN;or x not finite */
return (x*y)/(x*y);
if (hx < hy) { /* |x| < |y| return x or x-y */
q = 0;
goto fixup;
} else if(hx==hy) { /* |x| = |y| return x*0*/
*quo = 1;
return Zero[(uint32_t)sx>>31];
}
/* determine ix = ilogb(x) */
if (hx < 0x00800000) { /* subnormal x */
for (ix = -126, i=hx<<8; i>0; i<<=1) ix--;
} else
ix = (hx>>23) - 127;
/* determine iy = ilogb(y) */
if (hy < 0x00800000) { /* subnormal y */
for (iy = -126, i=hy<<8; i>0; i<<=1) iy--;
} else
iy = (hy>>23) - 127;
/* set up {hx,lx}, {hy,ly} and align y to x */
if (ix >= -126)
hx = 0x00800000|(0x007fffff&hx);
else { /* subnormal x, shift x to normal */
n = -126 - ix;
hx <<= n;
}
if (iy >= -126)
hy = 0x00800000|(0x007fffff&hy);
else { /* subnormal y, shift y to normal */
n = -126 - iy;
hy <<= n;
}
/* fix point fmod */
n = ix - iy;
q = 0;
while (n--) {
hz = hx - hy;
if (hz < 0)
hx = hx << 1;
else {
hx = hz << 1;
q++;
}
q <<= 1;
}
hz = hx - hy;
if (hz >= 0) {
hx = hz;
q++;
}
/* convert back to floating value and restore the sign */
if (hx == 0) { /* return sign(x)*0 */
*quo = sxy ? -q : q;
return Zero[(uint32_t)sx>>31];
}
while (hx < 0x00800000) { /* normalize x */
hx <<= 1;
iy--;
}
if (iy >= -126) { /* normalize output */
hx = (hx-0x00800000)|((iy+127)<<23);
} else { /* subnormal output */
n = -126 - iy;
hx >>= n;
}
fixup:
SET_FLOAT_WORD(x,hx);
y = fabsf(y);
if (y < 0x1p-125f) {
if (x + x > y || (x + x == y && (q & 1))) {
q++;
x -= y;
}
} else if (x > 0.5f*y || (x == 0.5f*y && (q & 1))) {
q++;
x -= y;
}
GET_FLOAT_WORD(hx, x);
SET_FLOAT_WORD(x, hx ^ sx);
q &= 0x7fffffff;
*quo = sxy ? -q : q;
return x;
}
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