106 lines
2.6 KiB
C
106 lines
2.6 KiB
C
/* e_fmodf.c -- float version of e_fmod.c.
|
|
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
|
|
*/
|
|
|
|
/*
|
|
* ====================================================
|
|
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
|
|
*
|
|
* Developed at SunPro, a Sun Microsystems, Inc. business.
|
|
* Permission to use, copy, modify, and distribute this
|
|
* software is freely granted, provided that this notice
|
|
* is preserved.
|
|
* ====================================================
|
|
*/
|
|
|
|
#ifndef lint
|
|
static char rcsid[] = "$FreeBSD$";
|
|
#endif
|
|
|
|
/*
|
|
* __ieee754_fmodf(x,y)
|
|
* Return x mod y in exact arithmetic
|
|
* Method: shift and subtract
|
|
*/
|
|
|
|
#include "math.h"
|
|
#include "math_private.h"
|
|
|
|
static const float one = 1.0, Zero[] = {0.0, -0.0,};
|
|
|
|
float
|
|
__ieee754_fmodf(float x, float y)
|
|
{
|
|
int32_t n,hx,hy,hz,ix,iy,sx,i;
|
|
|
|
GET_FLOAT_WORD(hx,x);
|
|
GET_FLOAT_WORD(hy,y);
|
|
sx = hx&0x80000000; /* sign of x */
|
|
hx ^=sx; /* |x| */
|
|
hy &= 0x7fffffff; /* |y| */
|
|
|
|
/* purge off exception values */
|
|
if(hy==0||(hx>=0x7f800000)|| /* y=0,or x not finite */
|
|
(hy>0x7f800000)) /* or y is NaN */
|
|
return (x*y)/(x*y);
|
|
if(hx<hy) return x; /* |x|<|y| return x */
|
|
if(hx==hy)
|
|
return Zero[(u_int32_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 = hx<<n;
|
|
}
|
|
if(iy >= -126)
|
|
hy = 0x00800000|(0x007fffff&hy);
|
|
else { /* subnormal y, shift y to normal */
|
|
n = -126-iy;
|
|
hy = hy<<n;
|
|
}
|
|
|
|
/* fix point fmod */
|
|
n = ix - iy;
|
|
while(n--) {
|
|
hz=hx-hy;
|
|
if(hz<0){hx = hx+hx;}
|
|
else {
|
|
if(hz==0) /* return sign(x)*0 */
|
|
return Zero[(u_int32_t)sx>>31];
|
|
hx = hz+hz;
|
|
}
|
|
}
|
|
hz=hx-hy;
|
|
if(hz>=0) {hx=hz;}
|
|
|
|
/* convert back to floating value and restore the sign */
|
|
if(hx==0) /* return sign(x)*0 */
|
|
return Zero[(u_int32_t)sx>>31];
|
|
while(hx<0x00800000) { /* normalize x */
|
|
hx = hx+hx;
|
|
iy -= 1;
|
|
}
|
|
if(iy>= -126) { /* normalize output */
|
|
hx = ((hx-0x00800000)|((iy+127)<<23));
|
|
SET_FLOAT_WORD(x,hx|sx);
|
|
} else { /* subnormal output */
|
|
n = -126 - iy;
|
|
hx >>= n;
|
|
SET_FLOAT_WORD(x,hx|sx);
|
|
x *= one; /* create necessary signal */
|
|
}
|
|
return x; /* exact output */
|
|
}
|