libm/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 1.10 2005/12/03 09:00:29 bde 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];
		GET_FLOAT_WORD(i0,t);
		SET_FLOAT_WORD(t,(i0&0x7fffffff)|(sx<<31));
	        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 */
}