source: vendor/FreeBSD-msun/current/src/s_rintf.c

/* s_rintf.c -- float version of s_rint.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: src/lib/msun/src/s_rintf.c,v 1.9 2004/06/09 21:24:52 das Exp $";
#endif

#include <sys/types.h>
#include "math.h"
#include "math_private.h"

static const float
TWO23[2]={
  8.3886080000e+06, /* 0x4b000000 */
 -8.3886080000e+06, /* 0xcb000000 */
};

float
rintf(float x)
{
        int32_t i0,j0,sx;
        volatile float w,t;     /* volatile works around gcc bug */
        GET_FLOAT_WORD(i0,x);
        sx = (i0>>31)&1;
        j0 = ((i0>>23)&0xff)-0x7f;
        if(j0<23) {
            if(j0<0) {
                if((i0&0x7fffffff)==0) return x;
                w = TWO23[sx]+x;
                t =  w-TWO23[sx];
                return t;
            }
            w = TWO23[sx]+x;
            return w-TWO23[sx];
        }
        if(j0==0x80) return x+x;        /* inf or NaN */
        else return x;                  /* x is integral */
}