e_hypotf.c

/*
 *                               POK header
 * 
 * The following file is a part of the POK project. Any modification should
 * made according to the POK licence. You CANNOT use this file or a part of
 * this file is this part of a file for your own project
 *
 * For more information on the POK licence, please see our LICENCE FILE
 *
 * Please follow the coding guidelines described in doc/CODING_GUIDELINES
 *
 *                                      Copyright (c) 2007-2009 POK team 
 *
 * Created by julien on Fri Jan 30 14:41:34 2009 
 */

/* e_hypotf.c -- float version of e_hypot.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.
 * ====================================================
 */

#ifdef POK_NEEDS_LIBMATH

#include "math_private.h"

float
__ieee754_hypotf(float x, float y)
{
        float a=x,b=y,t1,t2,yy1,y2,w;
        int32_t j,k,ha,hb;

        GET_FLOAT_WORD(ha,x);
        ha &= 0x7fffffff;
        GET_FLOAT_WORD(hb,y);
        hb &= 0x7fffffff;
        if(hb > ha) {a=y;b=x;j=ha; ha=hb;hb=j;} else {a=x;b=y;}
        SET_FLOAT_WORD(a,ha);   /* a <- |a| */
        SET_FLOAT_WORD(b,hb);   /* b <- |b| */
        if((ha-hb)>0xf000000) {return a+b;} /* x/y > 2**30 */
        k=0;
        if(ha > 0x58800000) {   /* a>2**50 */
           if(ha >= 0x7f800000) {       /* Inf or NaN */
               w = a+b;                 /* for sNaN */
               if(ha == 0x7f800000) w = a;
               if(hb == 0x7f800000) w = b;
               return w;
           }
           /* scale a and b by 2**-60 */
           ha -= 0x5d800000; hb -= 0x5d800000;  k += 60;
           SET_FLOAT_WORD(a,ha);
           SET_FLOAT_WORD(b,hb);
        }
        if(hb < 0x26800000) {   /* b < 2**-50 */
            if(hb <= 0x007fffff) {      /* subnormal b or 0 */
                if(hb==0) return a;
                SET_FLOAT_WORD(t1,0x3f000000);  /* t1=2^126 */
                b *= t1;
                a *= t1;
                k -= 126;
            } else {            /* scale a and b by 2^60 */
                ha += 0x5d800000;       /* a *= 2^60 */
                hb += 0x5d800000;       /* b *= 2^60 */
                k -= 60;
                SET_FLOAT_WORD(a,ha);
                SET_FLOAT_WORD(b,hb);
            }
        }
    /* medium size a and b */
        w = a-b;
        if (w>b) {
            SET_FLOAT_WORD(t1,ha&0xfffff000);
            t2 = a-t1;
            w  = __ieee754_sqrtf(t1*t1-(b*(-b)-t2*(a+t1)));
        } else {
            a  = a+a;
            SET_FLOAT_WORD(yy1,hb&0xfffff000);
            y2 = b - yy1;
            SET_FLOAT_WORD(t1,ha+0x00800000);
            t2 = a - t1;
            w  = __ieee754_sqrtf(t1*yy1-(w*(-w)-(t1*y2+t2*b)));
        }
        if(k!=0) {
            SET_FLOAT_WORD(t1,0x3f800000+(k<<23));
            return t1*w;
        } else return w;
}
#endif