lib/libm/math: Make tanhf more efficient and handle large numbers.
Prior to this patch tanhf(large number) would return nan due to inf/inf.
@@ -52,10 +52,14 @@ static const float _M_LN10 = 2.30258509299404; // 0x40135d8e
float log10f(float x) { return logf(x) / (float)_M_LN10; }
float tanhf(float x) {
- if (isinf(x)) {
- return copysignf(1, x);
- }
- return sinhf(x) / coshf(x);
+ int sign = 0;
+ if (x < 0) {
+ sign = 1;
+ x = -x;
+ }
+ x = expm1f(-2 * x);
+ x = x / (x + 2);
+ return sign ? x : -x;
}
/*****************************************************************************/
