bmi1.rs.html -- source
Description: Source to the Rust file `src\libcore\..\stdarch\crates\core_arch\src\x86\bmi1.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_u32)
    #[inline]
    #[target_feature(enable = "bmi1")]
    #[cfg_attr(test, assert_instr(bextr))]
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _bextr_u32(a: u32, start: u32, len: u32) -> u32 {
        _bextr2_u32(a, (start & 0xff_u32) | ((len & 0xff_u32) << 8_u32))
    }

    /// 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_u32)
    #[inline]
    #[target_feature(enable = "bmi1")]
    #[cfg_attr(test, assert_instr(bextr))]
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _bextr2_u32(a: u32, control: u32) -> u32 {
        x86_bmi_bextr_32(a, control)
    }

    /// Bitwise logical `AND` of inverted `a` with `b`.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_andn_u32)
    #[inline]
    #[target_feature(enable = "bmi1")]
    #[cfg_attr(test, assert_instr(andn))]
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _andn_u32(a: u32, b: u32) -> u32 {
        !a & b
    }

    /// Extracts lowest set isolated bit.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_blsi_u32)
    #[inline]
    #[target_feature(enable = "bmi1")]
    #[cfg_attr(test, assert_instr(blsi))]
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _blsi_u32(x: u32) -> u32 {
        x & x.wrapping_neg()
    }

    /// Gets mask up to lowest set bit.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_blsmsk_u32)
    #[inline]
    #[target_feature(enable = "bmi1")]
    #[cfg_attr(test, assert_instr(blsmsk))]
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _blsmsk_u32(x: u32) -> u32 {
        x ^ (x.wrapping_sub(1_u32))
    }

    /// Resets the lowest set bit of `x`.
    ///
    /// If `x` is sets CF.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_blsr_u32)
    #[inline]
    #[target_feature(enable = "bmi1")]
    #[cfg_attr(test, assert_instr(blsr))]
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _blsr_u32(x: u32) -> u32 {
        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_u32)
    #[inline]
    #[target_feature(enable = "bmi1")]
    #[cfg_attr(test, assert_instr(tzcnt))]
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _tzcnt_u32(x: u32) -> u32 {
        x.trailing_zeros()
    }

    /// 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_32)
    #[inline]
    #[target_feature(enable = "bmi1")]
    #[cfg_attr(test, assert_instr(tzcnt))]
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _mm_tzcnt_32(x: u32) -> i32 {
        x.trailing_zeros() as i32
    }

    extern "C" {
        #[link_name = "llvm.x86.bmi.bextr.32"]
        fn x86_bmi_bextr_32(x: u32, y: u32) -> u32;
    }

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

        use crate::core_arch::x86::*;

        #[simd_test(enable = "bmi1")]
        unsafe fn test_bextr_u32() {
            let r = _bextr_u32(0b0101_0000u32, 4, 4);
            assert_eq!(r, 0b0000_0101u32);
        }

        #[simd_test(enable = "bmi1")]
        unsafe fn test_andn_u32() {
            assert_eq!(_andn_u32(0, 0), 0);
            assert_eq!(_andn_u32(0, 1), 1);
            assert_eq!(_andn_u32(1, 0), 0);
            assert_eq!(_andn_u32(1, 1), 0);

            let r = _andn_u32(0b0000_0000u32, 0b0000_0000u32);
            assert_eq!(r, 0b0000_0000u32);

            let r = _andn_u32(0b0000_0000u32, 0b1111_1111u32);
            assert_eq!(r, 0b1111_1111u32);

            let r = _andn_u32(0b1111_1111u32, 0b0000_0000u32);
            assert_eq!(r, 0b0000_0000u32);

            let r = _andn_u32(0b1111_1111u32, 0b1111_1111u32);
            assert_eq!(r, 0b0000_0000u32);

            let r = _andn_u32(0b0100_0000u32, 0b0101_1101u32);
            assert_eq!(r, 0b0001_1101u32);
        }

        #[simd_test(enable = "bmi1")]
        unsafe fn test_blsi_u32() {
            assert_eq!(_blsi_u32(0b1101_0000u32), 0b0001_0000u32);
        }

        #[simd_test(enable = "bmi1")]
        unsafe fn test_blsmsk_u32() {
            let r = _blsmsk_u32(0b0011_0000u32);
            assert_eq!(r, 0b0001_1111u32);
        }

        #[simd_test(enable = "bmi1")]
        unsafe fn test_blsr_u32() {
            // TODO: test the behavior when the input is `0`.
            let r = _blsr_u32(0b0011_0000u32);
            assert_eq!(r, 0b0010_0000u32);
        }

        #[simd_test(enable = "bmi1")]
        unsafe fn test_tzcnt_u32() {
            assert_eq!(_tzcnt_u32(0b0000_0001u32), 0u32);
            assert_eq!(_tzcnt_u32(0b0000_0000u32), 32u32);
            assert_eq!(_tzcnt_u32(0b1001_0000u32), 4u32);
        }
    }