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#include "libm.h" // for FORCE_EVAL
#include <math.h> // for expm1f, tanhf
#include <stdint.h> // for uint32_t
float tanhf(float x)
{
union {
float f;
uint32_t i;
} u = { .f = x };
uint32_t w;
uint32_t sign;
float t;
/* x = |x| */
sign = u.i >> 31;
u.i &= 0x7fffffff;
x = u.f;
w = u.i;
if (w > 0x3f0c9f54) {
/* |x| > log(3)/2 ~= 0.5493 or nan */
if (w > 0x41200000) {
/* |x| > 10 */
t = 1 + 0 / x;
} else {
t = expm1f(2 * x);
t = 1 - 2 / (t + 2);
}
} else if (w > 0x3e82c578) {
/* |x| > log(5/3)/2 ~= 0.2554 */
t = expm1f(2 * x);
t = t / (t + 2);
} else if (w >= 0x00800000) {
/* |x| >= 0x1p-126 */
t = expm1f(-2 * x);
t = -t / (t + 2);
} else {
/* |x| is subnormal */
FORCE_EVAL(x * x);
t = x;
}
return sign ? -t : t;
}
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