ref: e047274e8dedebb9588a82e48e6cd9d7e50cae79
dir: /libmath/fdlibm/s_rint.c/
/* derived from /netlib/fdlibm */
/* @(#)s_rint.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.
* ====================================================
*/
/* dummy routine to get around over-eager arm compiler optimization.
* Calling this causes a store and reload of floating point numbers
*/
void
dummy(void)
{
}
/*
* rint(x)
* Return x rounded to integral value according to the prevailing
* rounding mode.
* Method:
* Using floating addition.
* Exception:
* Inexact flag raised if x not equal to rint(x).
*/
#include "fdlibm.h"
static const double
TWO52[2]={
4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
-4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
};
double rint(double x)
{
int i0,j0,sx;
unsigned i,i1;
double w,t;
i0 = __HI(x);
sx = (i0>>31)&1;
i1 = __LO(x);
j0 = ((i0>>20)&0x7ff)-0x3ff;
if(j0<20) {
if(j0<0) {
if(((i0&0x7fffffff)|i1)==0) return x;
i1 |= (i0&0x0fffff);
i0 &= 0xfffe0000;
i0 |= ((i1|-i1)>>12)&0x80000;
__HI(x)=i0;
w = TWO52[sx]+x;
dummy(); /* fix optimiser */
t = w-TWO52[sx];
i0 = __HI(t);
__HI(t) = (i0&0x7fffffff)|(sx<<31);
return t;
} else {
i = (0x000fffff)>>j0;
if(((i0&i)|i1)==0) return x; /* x is integral */
i>>=1;
if(((i0&i)|i1)!=0) {
if(j0==19) i1 = 0x40000000; else
i0 = (i0&(~i))|((0x20000)>>j0);
}
}
} else if (j0>51) {
if(j0==0x400) return x+x; /* inf or NaN */
else return x; /* x is integral */
} else {
i = ((unsigned)(0xffffffff))>>(j0-20);
if((i1&i)==0) return x; /* x is integral */
i>>=1;
if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20));
}
__HI(x) = i0;
__LO(x) = i1;
w = TWO52[sx]+x;
dummy(); /* fix optimiser */
return w-TWO52[sx];
}