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