use core::f64;

#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]

pub fn trunc(x: f64) -> f64 {

    // On wasm32 we know that LLVM's intrinsic will compile to an optimized

    // `f64.trunc` native instruction, so we can leverage this for both code size

    // and speed.

    llvm_intrinsically_optimized! {

        #[cfg(target_arch = "wasm32")] {

            return unsafe { ::core::intrinsics::truncf64(x) }

        }

    }

    let x1p120 = f64::from_bits(0x4770000000000000); // 0x1p120f === 2 ^ 120

    let mut i: u64 = x.to_bits();

    let mut e: i64 = (i >> 52 & 0x7ff) as i64 - 0x3ff + 12;

    let m: u64;

    if e >= 52 + 12 {

        return x;

    }

    if e < 12 {

        e = 1;

    }

    m = -1i64 as u64 >> e;

    if (i & m) == 0 {

        return x;

    }

    force_eval!(x + x1p120);

    i &= !m;

    f64::from_bits(i)

}

#[cfg(test)]

mod tests {

    #[test]

    fn sanity_check() {

        assert_eq!(super::trunc(1.1), 1.0);

    }

}