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

/* s_ilogbf.c -- float version of s_ilogb.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_ilogbf.c,v 1.7 2004/10/09 17:14:28 stefanf Exp $";
#endif

#include <limits.h>

#include "math.h"
#include "math_private.h"

        int ilogbf(float x)
{
        int32_t hx,ix;

        GET_FLOAT_WORD(hx,x);
        hx &= 0x7fffffff;
        if(hx<0x00800000) {
            if(hx==0)
                return FP_ILOGB0;
            else                        /* subnormal x */
                for (ix = -126,hx<<=8; hx>0; hx<<=1) ix -=1;
            return ix;
        }
        else if (hx<0x7f800000) return (hx>>23)-127;
        else if (hx>0x7f800000) return FP_ILOGBNAN;
        else return INT_MAX;
}