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

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[BZ #13840]
	* sysdeps/ieee754/flt-32/e_hypotf.c (__ieee754_hypotf): Rewrite to use
	double-precision for the calculation instead of scaling.
This commit is contained in:
David S. Miller 2012-03-13 18:08:58 -07:00
parent f453b98b6b
commit 7c10fd3515
2 changed files with 31 additions and 52 deletions
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6
ChangeLog
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@ -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> 2012-03-13 Joseph Myers <joseph@codesourcery.com>
* sysdeps/ieee754/dbl-64/s_nearbyint.c (__nearbyint): Do not * sysdeps/ieee754/dbl-64/s_nearbyint.c (__nearbyint): Do not

77
sysdeps/ieee754/flt-32/e_hypotf.c
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@ -19,62 +19,35 @@
float float
__ieee754_hypotf(float x, float y) __ieee754_hypotf(float x, float y)
{ {
float a,b,t1,t2,y1,y2,w; double d_x, d_y;
int32_t j,k,ha,hb; int32_t ha, hb;
GET_FLOAT_WORD(ha,x); GET_FLOAT_WORD(ha,x);
ha &= 0x7fffffff; ha &= 0x7fffffff;
GET_FLOAT_WORD(hb,y); GET_FLOAT_WORD(hb,y);
hb &= 0x7fffffff; hb &= 0x7fffffff;
if(hb > ha) {a=y;b=x;j=ha; ha=hb;hb=j;} else {a=x;b=y;} if (ha == 0x7f800000)
SET_FLOAT_WORD(a,ha); /* a <- |a| */ {
SET_FLOAT_WORD(b,hb); /* b <- |b| */ if (x == y)
if((ha-hb)>0xf000000) {return a+b;} /* x/y > 2**30 */ return fabsf(y);
k=0; return fabsf(x);
if(__builtin_expect(ha > 0x58800000, 0)) { /* a>2**50 */ }
if(ha >= 0x7f800000) { /* Inf or NaN */ else if (hb == 0x7f800000)
w = a+b; /* for sNaN */ {
if(ha == 0x7f800000) w = a; if (x == y)
if(hb == 0x7f800000) w = b; return fabsf(x);
return w; return fabsf(y);
} }
/* scale a and b by 2**-60 */ else if (ha > 0x7f800000 || hb > 0x7f800000)
ha -= 0x1e000000; hb -= 0x1e000000; k += 60; return fabsf(x) * fabsf(y);
SET_FLOAT_WORD(a,ha); else if (ha == 0)
SET_FLOAT_WORD(b,hb); return fabsf(y);
} else if (hb == 0)
if(__builtin_expect(hb < 0x26800000, 0)) { /* b < 2**-50 */ return fabsf(x);
if(hb <= 0x007fffff) { /* subnormal b or 0 */
if(hb==0) return a; d_x = (double) x;
SET_FLOAT_WORD(t1,0x7e800000); /* t1=2^126 */ d_y = (double) y;
b *= t1;
a *= t1; return (float) __ieee754_sqrt(d_x * d_x + d_y * d_y);
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;
} }
strong_alias (__ieee754_hypotf, __hypotf_finite) strong_alias (__ieee754_hypotf, __hypotf_finite)