bmi2.rs.html -- source
Description: Source to the Rust file `src/libcore/../stdsimd/coresimd/x86/bmi2.rs`.
Keywords: rust, rustlang, rust-lang

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    //! Bit Manipulation Instruction (BMI) Set 2.0.
    //!
    //! 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 stdsimd_test::assert_instr;

    /// Unsigned multiply without affecting flags.
    ///
    /// Unsigned multiplication of `a` with `b` returning a pair `(lo, hi)` with
    /// the low half and the high half of the result.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_mulx_u32)
    #[inline]
    // LLVM BUG (should be mulxl): https://bugs.llvm.org/show_bug.cgi?id=34232
    #[cfg_attr(all(test, target_arch = "x86_64"), assert_instr(imul))]
    #[cfg_attr(all(test, target_arch = "x86"), assert_instr(mulx))]
    #[target_feature(enable = "bmi2")]
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _mulx_u32(a: u32, b: u32, hi: &mut u32) -> u32 {
        let result: u64 = (a as u64) * (b as u64);
        *hi = (result >> 32) as u32;
        result as u32
    }

    /// Zero higher bits of `a` >= `index`.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_bzhi_u32)
    #[inline]
    #[target_feature(enable = "bmi2")]
    #[cfg_attr(test, assert_instr(bzhi))]
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _bzhi_u32(a: u32, index: u32) -> u32 {
        x86_bmi2_bzhi_32(a, index)
    }

    /// Scatter contiguous low order bits of `a` to the result at the positions
    /// specified by the `mask`.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_pdep_u32)
    #[inline]
    #[target_feature(enable = "bmi2")]
    #[cfg_attr(test, assert_instr(pdep))]
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _pdep_u32(a: u32, mask: u32) -> u32 {
        x86_bmi2_pdep_32(a, mask)
    }

    /// Gathers the bits of `x` specified by the `mask` into the contiguous low
    /// order bit positions of the result.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_pext_u32)
    #[inline]
    #[target_feature(enable = "bmi2")]
    #[cfg_attr(test, assert_instr(pext))]
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _pext_u32(a: u32, mask: u32) -> u32 {
        x86_bmi2_pext_32(a, mask)
    }

    extern "C" {
        #[link_name = "llvm.x86.bmi.bzhi.32"]
        fn x86_bmi2_bzhi_32(x: u32, y: u32) -> u32;
        #[link_name = "llvm.x86.bmi.pdep.32"]
        fn x86_bmi2_pdep_32(x: u32, y: u32) -> u32;
        #[link_name = "llvm.x86.bmi.pext.32"]
        fn x86_bmi2_pext_32(x: u32, y: u32) -> u32;
    }

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

        use coresimd::x86::*;

        #[simd_test(enable = "bmi2")]
        unsafe fn test_pext_u32() {
            let n = 0b1011_1110_1001_0011u32;

            let m0 = 0b0110_0011_1000_0101u32;
            let s0 = 0b0000_0000_0011_0101u32;

            let m1 = 0b1110_1011_1110_1111u32;
            let s1 = 0b0001_0111_0100_0011u32;

            assert_eq!(_pext_u32(n, m0), s0);
            assert_eq!(_pext_u32(n, m1), s1);
        }

        #[simd_test(enable = "bmi2")]
        unsafe fn test_pdep_u32() {
            let n = 0b1011_1110_1001_0011u32;

            let m0 = 0b0110_0011_1000_0101u32;
            let s0 = 0b0000_0010_0000_0101u32;

            let m1 = 0b1110_1011_1110_1111u32;
            let s1 = 0b1110_1001_0010_0011u32;

            assert_eq!(_pdep_u32(n, m0), s0);
            assert_eq!(_pdep_u32(n, m1), s1);
        }

        #[simd_test(enable = "bmi2")]
        unsafe fn test_bzhi_u32() {
            let n = 0b1111_0010u32;
            let s = 0b0001_0010u32;
            assert_eq!(_bzhi_u32(n, 5), s);
        }

        #[simd_test(enable = "bmi2")]
        unsafe fn test_mulx_u32() {
            let a: u32 = 4_294_967_200;
            let b: u32 = 2;
            let mut hi = 0;
            let lo = _mulx_u32(a, b, &mut hi);
            /*
            result = 8589934400
                   = 0b0001_1111_1111_1111_1111_1111_1111_0100_0000u64
                       ^~hi ^~lo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                    */
            assert_eq!(lo, 0b1111_1111_1111_1111_1111_1111_0100_0000u32);
            assert_eq!(hi, 0b0001u32);
        }
    }

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