bmi.rs.html -- source
Description: Source to the Rust file `src/libcore/../stdarch/crates/core_arch/src/x86_64/bmi.rs`.
Keywords: rust, rustlang, rust-lang

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    //! Bit Manipulation Instruction (BMI) Set 1.0.
    //!
    //! The reference is [Intel 64 and IA-32 Architectures Software Developer's
    //! Manual Volume 2: Instruction Set Reference, A-Z][intel64_ref].
    //!
    //! [Wikipedia][wikipedia_bmi] provides a quick overview of the instructions
    //! available.
    //!
    //! [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;

    /// Extracts bits in range [`start`, `start` + `length`) from `a` into
    /// the least significant bits of the result.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#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)
    }

    /// Extracts bits of `a` specified by `control` into
    /// the least significant bits of the result.
    ///
    /// Bits `[7,0]` of `control` specify the index to the first bit in the range
    /// to be extracted, and bits `[15,8]` specify the length of the range.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#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)
    }

    /// Bitwise logical `AND` of inverted `a` with `b`.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#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
    }

    /// Extracts lowest set isolated bit.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_blsi_u64)
    #[inline]
    #[target_feature(enable = "bmi1")]
    #[cfg_attr(test, assert_instr(blsi))]
    #[cfg(not(target_arch = "x86"))] // generates lots of instructions
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _blsi_u64(x: u64) -> u64 {
        x & x.wrapping_neg()
    }

    /// Gets mask up to lowest set bit.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_blsmsk_u64)
    #[inline]
    #[target_feature(enable = "bmi1")]
    #[cfg_attr(test, assert_instr(blsmsk))]
    #[cfg(not(target_arch = "x86"))] // generates lots of instructions
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _blsmsk_u64(x: u64) -> u64 {
        x ^ (x.wrapping_sub(1_u64))
    }

    /// Resets the lowest set bit of `x`.
    ///
    /// If `x` is sets CF.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_blsr_u64)
    #[inline]
    #[target_feature(enable = "bmi1")]
    #[cfg_attr(test, assert_instr(blsr))]
    #[cfg(not(target_arch = "x86"))] // generates lots of instructions
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _blsr_u64(x: u64) -> u64 {
        x & (x.wrapping_sub(1))
    }

    /// Counts the number of trailing least significant zero bits.
    ///
    /// When the source operand is `0`, it returns its size in bits.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#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
    }

    /// Counts the number of trailing least significant zero bits.
    ///
    /// When the source operand is `0`, it returns its size in bits.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#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: test the behavior when the input is `0`.
            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);
        }
    }