forked from KolibriOS/kolibrios
131 lines
3.4 KiB
C
131 lines
3.4 KiB
C
/* Adapted for Newlib, 2009. (Allow for int < 32 bits; return *quo=0 during
|
|
* errors to make test scripts easier.) */
|
|
/* @(#)e_fmod.c 1.3 95/01/18 */
|
|
/*-
|
|
* ====================================================
|
|
* 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.
|
|
* ====================================================
|
|
*/
|
|
|
|
#include <math.h>
|
|
#include "fdlibm.h"
|
|
|
|
/* For quotient, return either all 31 bits that can from calculation (using
|
|
* int32_t), or as many as can fit into an int that is smaller than 32 bits. */
|
|
#if INT_MAX > 0x7FFFFFFFL
|
|
#define QUO_MASK 0x7FFFFFFF
|
|
# else
|
|
#define QUO_MASK INT_MAX
|
|
#endif
|
|
|
|
static const float Zero[] = {0.0, -0.0,};
|
|
|
|
/*
|
|
* Return the IEEE remainder and set *quo to the last n bits of the
|
|
* quotient, rounded to the nearest integer. We choose n=31--if that many fit--
|
|
* 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.
|
|
*/
|
|
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 */
|
|
*quo = 0; /* Not necessary, but return consistent value */
|
|
return (x*y)/(x*y);
|
|
}
|
|
if(hx<hy) {
|
|
q = 0;
|
|
goto fixup; /* |x|<|y| return x or x-y */
|
|
} else if(hx==hy) {
|
|
*quo = 1;
|
|
return Zero[(__uint32_t)sx>>31]; /* |x|=|y| return x*0*/
|
|
}
|
|
|
|
/* determine ix = ilogb(x) */
|
|
if(hx<0x00800000) { /* subnormal x */
|
|
for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1;
|
|
} 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 -=1;
|
|
} 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 -= 1;
|
|
}
|
|
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;
|
|
}
|