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//! 位操作指令 (BMI) 设置 1.0。
//!
//! 引用的是 [英特尔 64 位和 IA-32 架构软件开发人员手册第 2 卷：指令集参考，A-Z][intel64_ref]。
//!
//! [维基百科][wikipedia_bmi] 提供了可用指令的快速概览。
//!
//! [intel64_ref]: http://www.intel.de/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-instruction-set-reference-manual-325383.pdf
//! [wikipedia_bmi]: https://en.wikipedia.org/wiki/Bit_Manipulation_Instruction_Sets#ABM_.28Advanced_Bit_Manipulation.29
//!
//!

#[cfg(test)]
use stdarch_test::assert_instr;

/// 从 `a` 提取范围为 [start，`start` + `length`) 的位到结果的最低有效位。
///
/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_bextr_u64)
///
#[inline]
#[target_feature(enable = "bmi1")]
#[cfg_attr(test, assert_instr(bextr))]
#[cfg(not(target_arch = "x86"))]
#[stable(feature = "simd_x86", since = "1.27.0")]
pub unsafe fn _bextr_u64(a: u64, start: u32, len: u32) -> u64 {
    _bextr2_u64(a, ((start & 0xff) | ((len & 0xff) << 8)) as u64)
}

/// 将 `control` 指定的 `a` 的位提取到结果的最低有效位中。
///
/// `control` 的位 `[7,0]` 指定要提取的范围中第一位的索引，而 `[15,8]` 的位指定范围的长度。
///
///
/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_bextr2_u64)
///
#[inline]
#[target_feature(enable = "bmi1")]
#[cfg_attr(test, assert_instr(bextr))]
#[cfg(not(target_arch = "x86"))]
#[stable(feature = "simd_x86", since = "1.27.0")]
pub unsafe fn _bextr2_u64(a: u64, control: u64) -> u64 {
    x86_bmi_bextr_64(a, control)
}

/// `a` 和 `b` 的按位逻辑 `AND`。
///
/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_andn_u64)
#[inline]
#[target_feature(enable = "bmi1")]
#[cfg_attr(test, assert_instr(andn))]
#[stable(feature = "simd_x86", since = "1.27.0")]
pub unsafe fn _andn_u64(a: u64, b: u64) -> u64 {
    !a & b
}

/// 提取最低位隔离位。
///
/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_blsi_u64)
#[inline]
#[target_feature(enable = "bmi1")]
#[cfg_attr(test, assert_instr(blsi))]
#[cfg(not(target_arch = "x86"))] // 产生很多指令
#[stable(feature = "simd_x86", since = "1.27.0")]
pub unsafe fn _blsi_u64(x: u64) -> u64 {
    x & x.wrapping_neg()
}

/// 将掩码提高到最低设置位。
///
/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_blsmsk_u64)
#[inline]
#[target_feature(enable = "bmi1")]
#[cfg_attr(test, assert_instr(blsmsk))]
#[cfg(not(target_arch = "x86"))] // 产生很多指令
#[stable(feature = "simd_x86", since = "1.27.0")]
pub unsafe fn _blsmsk_u64(x: u64) -> u64 {
    x ^ (x.wrapping_sub(1_u64))
}

/// 复位 `x` 的最低位。
///
/// 如果 `x` 设置为 CF。
///
/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_blsr_u64)
#[inline]
#[target_feature(enable = "bmi1")]
#[cfg_attr(test, assert_instr(blsr))]
#[cfg(not(target_arch = "x86"))] // 产生很多指令
#[stable(feature = "simd_x86", since = "1.27.0")]
pub unsafe fn _blsr_u64(x: u64) -> u64 {
    x & (x.wrapping_sub(1))
}

/// 计算尾随的最低有效零位的数量。
///
/// 当源操作数为 `0` 时，它将返回其大小 (以位为单位)。
///
/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_tzcnt_u64)
#[inline]
#[target_feature(enable = "bmi1")]
#[cfg_attr(test, assert_instr(tzcnt))]
#[stable(feature = "simd_x86", since = "1.27.0")]
pub unsafe fn _tzcnt_u64(x: u64) -> u64 {
    x.trailing_zeros() as u64
}

/// 计算尾随的最低有效零位的数量。
///
/// 当源操作数为 `0` 时，它将返回其大小 (以位为单位)。
///
/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_mm_tzcnt_64)
#[inline]
#[target_feature(enable = "bmi1")]
#[cfg_attr(test, assert_instr(tzcnt))]
#[stable(feature = "simd_x86", since = "1.27.0")]
pub unsafe fn _mm_tzcnt_64(x: u64) -> i64 {
    x.trailing_zeros() as i64
}

extern "C" {
    #[link_name = "llvm.x86.bmi.bextr.64"]
    fn x86_bmi_bextr_64(x: u64, y: u64) -> u64;
}

#[cfg(test)]
mod tests {
    use stdarch_test::simd_test;

    use crate::core_arch::{x86::*, x86_64::*};

    #[simd_test(enable = "bmi1")]
    unsafe fn test_bextr_u64() {
        let r = _bextr_u64(0b0101_0000u64, 4, 4);
        assert_eq!(r, 0b0000_0101u64);
    }

    #[simd_test(enable = "bmi1")]
    unsafe fn test_andn_u64() {
        assert_eq!(_andn_u64(0, 0), 0);
        assert_eq!(_andn_u64(0, 1), 1);
        assert_eq!(_andn_u64(1, 0), 0);
        assert_eq!(_andn_u64(1, 1), 0);

        let r = _andn_u64(0b0000_0000u64, 0b0000_0000u64);
        assert_eq!(r, 0b0000_0000u64);

        let r = _andn_u64(0b0000_0000u64, 0b1111_1111u64);
        assert_eq!(r, 0b1111_1111u64);

        let r = _andn_u64(0b1111_1111u64, 0b0000_0000u64);
        assert_eq!(r, 0b0000_0000u64);

        let r = _andn_u64(0b1111_1111u64, 0b1111_1111u64);
        assert_eq!(r, 0b0000_0000u64);

        let r = _andn_u64(0b0100_0000u64, 0b0101_1101u64);
        assert_eq!(r, 0b0001_1101u64);
    }

    #[simd_test(enable = "bmi1")]
    unsafe fn test_blsi_u64() {
        assert_eq!(_blsi_u64(0b1101_0000u64), 0b0001_0000u64);
    }

    #[simd_test(enable = "bmi1")]
    unsafe fn test_blsmsk_u64() {
        let r = _blsmsk_u64(0b0011_0000u64);
        assert_eq!(r, 0b0001_1111u64);
    }

    #[simd_test(enable = "bmi1")]
    unsafe fn test_blsr_u64() {
        // TODO: 测试输入为 `0` 时的行为。
        let r = _blsr_u64(0b0011_0000u64);
        assert_eq!(r, 0b0010_0000u64);
    }

    #[simd_test(enable = "bmi1")]
    unsafe fn test_tzcnt_u64() {
        assert_eq!(_tzcnt_u64(0b0000_0001u64), 0u64);
        assert_eq!(_tzcnt_u64(0b0000_0000u64), 64u64);
        assert_eq!(_tzcnt_u64(0b1001_0000u64), 4u64);
    }
}