third_party/rust/libm/src/math/tanhf.rs


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use super::expm1f;

#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
pub fn tanhf(mut x: f32) -> f32 {
    /* x = |x| */
    let mut ix = x.to_bits();
    let sign = (ix >> 31) != 0;
    ix &= 0x7fffffff;
    x = f32::from_bits(ix);
    let w = ix;

    let tt = if w > 0x3f0c9f54 {
        /* |x| > log(3)/2 ~= 0.5493 or nan */
        if w > 0x41200000 {
            /* |x| > 10 */
            1. + 0. / x
        } else {
            let t = expm1f(2. * x);
            1. - 2. / (t + 2.)
        }
    } else if w > 0x3e82c578 {
        /* |x| > log(5/3)/2 ~= 0.2554 */
        let t = expm1f(2. * x);
        t / (t + 2.)
    } else if w >= 0x00800000 {
        /* |x| >= 0x1p-126 */
        let t = expm1f(-2. * x);
        -t / (t + 2.)
    } else {
        /* |x| is subnormal */
        force_eval!(x * x);
        x
    };
    if sign {
        -tt
    } else {
        tt
    }
}