double exp(double x)
{
- double hi, lo, c, z;
+ double hi, lo, c, xx;
int k, sign;
uint32_t hx;
if (hx >= 0x40862e42) { /* if |x| >= 709.78... */
if (isnan(x))
return x;
+ if (hx == 0x7ff00000 && sign) /* -inf */
+ return 0;
if (x > 709.782712893383973096) {
/* overflow if x!=inf */
STRICT_ASSIGN(double, x, 0x1p1023 * x);
return x;
}
if (x < -745.13321910194110842) {
- /* underflow if x!=-inf */
- STRICT_ASSIGN(double, x, 0x1p-1000 / -x * 0x1p-1000);
+ /* underflow */
+ STRICT_ASSIGN(double, x, 0x1p-1000 * 0x1p-1000);
return x;
}
}
/* argument reduction */
if (hx > 0x3fd62e42) { /* if |x| > 0.5 ln2 */
- if (hx < 0x3ff0a2b2) /* if |x| < 1.5 ln2 */
- k = 1 - sign - sign; /* optimization */
- else
+ if (hx >= 0x3ff0a2b2) /* if |x| >= 1.5 ln2 */
k = (int)(invln2*x + half[sign]);
+ else
+ k = 1 - sign - sign;
hi = x - k*ln2hi; /* k*ln2hi is exact here */
lo = k*ln2lo;
STRICT_ASSIGN(double, x, hi - lo);
}
/* x is now in primary range */
- z = x*x;
- c = x - z*(P1+z*(P2+z*(P3+z*(P4+z*P5))));
- x = 1 + ((x*c/(2-c) - lo) + hi);
+ xx = x*x;
+ c = x - xx*(P1+xx*(P2+xx*(P3+xx*(P4+xx*P5))));
+ x = 1 + (x*c/(2-c) - lo + hi);
if (k == 0)
return x;
return scalbn(x, k);