src/math/tanhf.c

   1 #include "libm.h"
   2
   3 float tanhf(float x)
   4 {
   5         union {float f; uint32_t i;} u = {.f = x};
   6         uint32_t w;
   7         int sign;
   8         float t;
   9
  10         /* x = |x| */
  11         sign = u.i >> 31;
  12         u.i &= 0x7fffffff;
  13         x = u.f;
  14         w = u.i;
  15
  16         if (w > 0x3f0c9f54) {
  17                 /* |x| > log(3)/2 ~= 0.5493 or nan */
  18                 if (w > 0x41200000) {
  19                         /* |x| > 10 */
  20                         t = 1 + 0/x;
  21                 } else {
  22                         t = expm1f(2*x);
  23                         t = 1 - 2/(t+2);
  24                 }
  25         } else if (w > 0x3e82c578) {
  26                 /* |x| > log(5/3)/2 ~= 0.2554 */
  27                 t = expm1f(2*x);
  28                 t = t/(t+2);
  29         } else if (w >= 0x00800000) {
  30                 /* |x| >= 0x1p-126 */
  31                 t = expm1f(-2*x);
  32                 t = -t/(t+2);
  33         } else {
  34                 /* |x| is subnormal */
  35                 FORCE_EVAL(x*x);
  36                 t = x;
  37         }
  38         return sign ? -t : t;
  39 }