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use int::Int;
use alg;

#[cfg(RUSTC_IS_NIGHTLY)]
mod intrinsics {
    use int::Int;
    use alg;

    #[allow(dead_code)]
    extern "platform-intrinsic" {
        fn x86_bmi_bextr_32(x: u32, y: u32) -> u32;
        fn x86_bmi_bextr_64(x: u64, y: u64) -> u64;
    }

    #[inline]
    pub unsafe fn bextr<T: Int>(source: T, range: T) -> T {
        match T::bit_size().to_u8() {
            32 => T::from_u32(x86_bmi_bextr_32(source.to_u32(), range.to_u32())),
            64 => T::from_u64(x86_bmi_bextr_64(source.to_u64(), range.to_u64())),
            _ => alg::x86::tbm::bextr(source, range),
        }
    }


} // mod intrinsics

/// Bit Field Extract.
///
/// Extracts bits in `range` from the `source` to the least significant bits of
/// the result. Bits [7,0] of `range` specify the index to the first bit in the
/// range to be extracted, and bits [15,8] specify the length of the range.
///
/// Only bits up to `T::bit_size() - 1` are extracted.
///
/// The extracted bits are written in the result starting from the
/// least-significant bit. The high-order bits of the result are zeroed.
///
/// # Assembly Instructions
///
/// - [`BEXTR`](https://support.amd.com/TechDocs/24594.pdf):
///   - Description: Bit field extract.
///   - Architecture: x86.
///   - Instruction set: TBM.
///   - Registers: 32/64 bit.
///
/// # Example
///
/// ```
/// use bitintr::x86::tbm::*;
///
/// assert_eq!(bextr(0b0000_0000_0101_0000u16, 0b0000_0100_0000_0100u16), 0b0000_0000_0000_0101u16);
/// assert_eq!(0b0000_0000_0101_0000u16.bextr(0b0000_0100_0000_0100u16), 0b0000_0000_0000_0101u16);
/// ```
#[inline]
pub fn bextr<T: Int>(source: T, range: T) -> T {
    #[cfg(RUSTC_IS_NIGHTLY)]
    {
        if cfg!(target_feature = "bmi2") {
            unsafe { intrinsics::bextr(source, range) }
        } else {
            alg::x86::tbm::bextr(source, range)
        }
    }
    #[cfg(not(RUSTC_IS_NIGHTLY))]
    {
        alg::x86::tbm::bextr(source, range)
    }
}

/// Method version of [`bextr`](fn.bextr.html).
pub trait BEXTR {
    #[inline]
    fn bextr(self, Self) -> Self;
}

impl<T: Int> BEXTR for T {
    #[inline]
    fn bextr(self, range: Self) -> Self {
        bextr(self, range)
    }
}