From: David S. Miller <davem@davemloft.net>
Date: Wed, 14 Mar 2012 01:08:58 +0000 (-0700)
Subject: Fix hypotf overflow/underflow by using double precision instead of scaling.
X-Git-Tag: glibc-2.16-tps~815
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=7c10fd3515f983ca732b2166ccffebbf83603f1f;p=platform%2Fupstream%2Fglibc.git

Fix hypotf overflow/underflow by using double precision instead of scaling.

	[BZ #13840]
	* sysdeps/ieee754/flt-32/e_hypotf.c (__ieee754_hypotf): Rewrite to use
	double-precision for the calculation instead of scaling.
---

diff --git a/ChangeLog b/ChangeLog
index b8f1fe5..b65f68a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2012-03-13  David S. Miller  <davem@davemloft.net>
+
+	[BZ #13840]
+	* sysdeps/ieee754/flt-32/e_hypotf.c (__ieee754_hypotf): Rewrite to use
+	double-precision for the calculation instead of scaling.
+
 2012-03-13  Joseph Myers  <joseph@codesourcery.com>
 
 	* sysdeps/ieee754/dbl-64/s_nearbyint.c (__nearbyint): Do not
diff --git a/sysdeps/ieee754/flt-32/e_hypotf.c b/sysdeps/ieee754/flt-32/e_hypotf.c
index 97e7d34..8f499b5 100644
--- a/sysdeps/ieee754/flt-32/e_hypotf.c
+++ b/sysdeps/ieee754/flt-32/e_hypotf.c
@@ -19,62 +19,35 @@
 float
 __ieee754_hypotf(float x, float y)
 {
-	float a,b,t1,t2,y1,y2,w;
-	int32_t j,k,ha,hb;
+	double d_x, d_y;
+	int32_t 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(__builtin_expect(ha > 0x58800000, 0)) {	/* 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 -= 0x1e000000; hb -= 0x1e000000;	k += 60;
-	   SET_FLOAT_WORD(a,ha);
-	   SET_FLOAT_WORD(b,hb);
-	}
-	if(__builtin_expect(hb < 0x26800000, 0)) {	/* 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 2^60 */
-		ha += 0x1e000000;	/* a *= 2^60 */
-		hb += 0x1e000000;	/* 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(y1,hb&0xfffff000);
-	    y2 = b - y1;
-	    SET_FLOAT_WORD(t1,ha+0x00800000);
-	    t2 = a - t1;
-	    w  = __ieee754_sqrtf(t1*y1-(w*(-w)-(t1*y2+t2*b)));
-	}
-	if(k!=0) {
-	    SET_FLOAT_WORD(t1,0x3f800000+(k<<23));
-	    return t1*w;
-	} else return w;
+	if (ha == 0x7f800000)
+	  {
+	    if (x == y)
+	      return fabsf(y);
+	    return fabsf(x);
+	  }
+	else if (hb == 0x7f800000)
+	  {
+	    if (x == y)
+	      return fabsf(x);
+	    return fabsf(y);
+	  }
+	else if (ha > 0x7f800000 || hb > 0x7f800000)
+	  return fabsf(x) * fabsf(y);
+	else if (ha == 0)
+	  return fabsf(y);
+	else if (hb == 0)
+	  return fabsf(x);
+
+	d_x = (double) x;
+	d_y = (double) y;
+
+	return (float) __ieee754_sqrt(d_x * d_x + d_y * d_y);
 }
 strong_alias (__ieee754_hypotf, __hypotf_finite)