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 (file)
--- 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 (file)
--- 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)