musl/src/math/hypotf.c

/* origin: FreeBSD /usr/src/lib/msun/src/e_hypotf.c */
/*
 * Conversion to float by Ian Lance Taylor, Cygnus Support, [email protected].
 */
/*
 * ====================================================
 * 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.
 * ====================================================
 */

#include "libm.h"

float hypotf(float x, float y)
{
	float a,b,t1,t2,y1,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;
	}
	a = fabsf(a);
	b = fabsf(b);
	if (ha - hb > 0xf000000)  /* x/y > 2**30 */
		return a+b;
	k = 0;
	if (ha > 0x58800000) {    /* a > 2**50 */
		if(ha >= 0x7f800000) {  /* Inf or NaN */
			/* Use original arg order iff result is NaN; quieten sNaNs. */
			w = fabsf(x+0.0f) - fabsf(y+0.0f);
			if (ha == 0x7f800000) w = a;
			if (hb == 0x7f800000) w = b;
			return w;
		}
		/* scale a and b by 2**-68 */
		ha -= 0x22000000; hb -= 0x22000000; k += 68;
		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, 0x7e800000);  /* t1 = 2^126 */
			b *= t1;
			a *= t1;
			k -= 126;
		} else {   /* scale a and b by 2^68 */
			ha += 0x22000000;  /* a *= 2^68 */
			hb += 0x22000000;  /* b *= 2^68 */
			k -= 68;
			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  = sqrtf(t1*t1-(b*(-b)-t2*(a+t1)));
	} else {
		a  = a + a;
		SET_FLOAT_WORD(y1, hb&0xfffff000);
		y2 = b - y1;
		SET_FLOAT_WORD(t1,(ha+0x00800000)&0xfffff000);
		t2 = a - t1;
		w  = sqrtf(t1*y1-(w*(-w)-(t1*y2+t2*b)));
	}
	if (k)
		w = scalbnf(w, k);
	return w;
}