bitintr 0.1.0

Portable Bit Manipulation Intrinsics.
Documentation 
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use int::IntF32T64;
use alg;

mod intrinsics {
    use int::IntF32T64;
    use std::mem::size_of;

    #[allow(dead_code)]
    extern "platform-intrinsic" {
        fn x86_bmi2_bzhi_32(x: u32, y: u32) -> u32;
        fn x86_bmi2_bzhi_64(x: u64, y: u64) -> u64;
    }

    pub unsafe fn bzhi<T: IntF32T64>(x: T, y: T) -> T {
        match size_of::<T>() * 8 {
            32 => T::from_u32(x86_bmi2_bzhi_32(x.to_u32(), y.to_u32())),
            64 => T::from_u64(x86_bmi2_bzhi_64(x.to_u64(), y.to_u64())),
            _ => unreachable!(),
        }
    }

} // mod intrinsics

pub fn bzhi<T: IntF32T64>(x: T, bit_position: T) -> T {
    debug_assert!(bit_position < T::bit_size());
    if cfg!(target_feature = "bmi2") {
        unsafe { intrinsics::bzhi(x, bit_position) }
    } else {
        alg::bmi2::bzhi(x, bit_position)
    }
}