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    //! Vectorized Carry-less Multiplication (VCLMUL)
    //!
    //! The reference is [Intel 64 and IA-32 Architectures Software Developer's
    //! Manual Volume 2: Instruction Set Reference, A-Z][intel64_ref] (p. 4-241).
    //!
    //! [intel64_ref]: http://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-instruction-set-reference-manual-325383.pdf

    use crate::core_arch::x86::__m256i;
    use crate::core_arch::x86::__m512i;

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

    #[allow(improper_ctypes)]
    extern "C" {
        #[link_name = "llvm.x86.pclmulqdq.256"]
        fn pclmulqdq_256(a: __m256i, round_key: __m256i, imm8: u8) -> __m256i;
        #[link_name = "llvm.x86.pclmulqdq.512"]
        fn pclmulqdq_512(a: __m512i, round_key: __m512i, imm8: u8) -> __m512i;
    }

    // for some odd reason on x86_64 we generate the correct long name instructions
    // but on i686 we generate the short name + imm8
    // so we need to special-case on that...

    /// Performs a carry-less multiplication of two 64-bit polynomials over the
    /// finite field GF(2^k) - in each of the 4 128-bit lanes.
    ///
    /// The immediate byte is used for determining which halves of each lane `a` and `b`
    /// should be used. Immediate bits other than 0 and 4 are ignored.
    /// All lanes share immediate byte.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_mm512_clmulepi64_epi128)
    #[inline]
    #[target_feature(enable = "avx512vpclmulqdq,avx512f")]
    // technically according to Intel's documentation we don't need avx512f here, however LLVM gets confused otherwise
    #[cfg_attr(test, assert_instr(vpclmul, imm8 = 0))]
    #[rustc_args_required_const(2)]
    pub unsafe fn _mm512_clmulepi64_epi128(a: __m512i, b: __m512i, imm8: i32) -> __m512i {
        macro_rules! call {
            ($imm8:expr) => {
                pclmulqdq_512(a, b, $imm8)
            };
        }
        constify_imm8!(imm8, call)
    }

    /// Performs a carry-less multiplication of two 64-bit polynomials over the
    /// finite field GF(2^k) - in each of the 2 128-bit lanes.
    ///
    /// The immediate byte is used for determining which halves of each lane `a` and `b`
    /// should be used. Immediate bits other than 0 and 4 are ignored.
    /// All lanes share immediate byte.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_mm256_clmulepi64_epi128)
    #[inline]
    #[target_feature(enable = "avx512vpclmulqdq,avx512vl")]
    #[cfg_attr(test, assert_instr(vpclmul, imm8 = 0))]
    #[rustc_args_required_const(2)]
    pub unsafe fn _mm256_clmulepi64_epi128(a: __m256i, b: __m256i, imm8: i32) -> __m256i {
        macro_rules! call {
            ($imm8:expr) => {
                pclmulqdq_256(a, b, $imm8)
            };
        }
        constify_imm8!(imm8, call)
    }

    #[cfg(test)]
    mod tests {
        // The constants in the tests below are just bit patterns. They should not
        // be interpreted as integers; signedness does not make sense for them, but
        // __mXXXi happens to be defined in terms of signed integers.
        #![allow(overflowing_literals)]

        use stdarch_test::simd_test;

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

        macro_rules! verify_kat_pclmul {
            ($broadcast:ident, $clmul:ident, $assert:ident) => {
                // Constants taken from https://software.intel.com/sites/default/files/managed/72/cc/clmul-wp-rev-2.02-2014-04-20.pdf
             let a = _mm_set_epi64x(0x7b5b546573745665, 0x63746f725d53475d);
             let a = $broadcast(a);
             let b = _mm_set_epi64x(0x4869285368617929, 0x5b477565726f6e5d);
             let b = $broadcast(b);
             let r00 = _mm_set_epi64x(0x1d4d84c85c3440c0, 0x929633d5d36f0451);
             let r00 = $broadcast(r00);
             let r01 = _mm_set_epi64x(0x1bd17c8d556ab5a1, 0x7fa540ac2a281315);
             let r01 = $broadcast(r01);
             let r10 = _mm_set_epi64x(0x1a2bf6db3a30862f, 0xbabf262df4b7d5c9);
             let r10 = $broadcast(r10);
             let r11 = _mm_set_epi64x(0x1d1e1f2c592e7c45, 0xd66ee03e410fd4ed);
             let r11 = $broadcast(r11);

             $assert($clmul(a, b, 0x00), r00);
             $assert($clmul(a, b, 0x10), r01);
             $assert($clmul(a, b, 0x01), r10);
             $assert($clmul(a, b, 0x11), r11);

             let a0 = _mm_set_epi64x(0x0000000000000000, 0x8000000000000000);
             let a0 = $broadcast(a0);
             let r = _mm_set_epi64x(0x4000000000000000, 0x0000000000000000);
             let r = $broadcast(r);
             $assert($clmul(a0, a0, 0x00), r);
            }
        }

        macro_rules! unroll {
            ($target:ident[4] = $op:ident($source:ident,4);) => {
                $target[3] = $op($source, 3);
                $target[2] = $op($source, 2);
                unroll! {$target[2] = $op($source,2);}
            };
            ($target:ident[2] = $op:ident($source:ident,2);) => {
                $target[1] = $op($source, 1);
                $target[0] = $op($source, 0);
            };
            (assert_eq_m128i($op:ident($vec_res:ident,4),$lin_res:ident[4]);) => {
                assert_eq_m128i($op($vec_res, 3), $lin_res[3]);
                assert_eq_m128i($op($vec_res, 2), $lin_res[2]);
                unroll! {assert_eq_m128i($op($vec_res,2),$lin_res[2]);}
            };
            (assert_eq_m128i($op:ident($vec_res:ident,2),$lin_res:ident[2]);) => {
                assert_eq_m128i($op($vec_res, 1), $lin_res[1]);
                assert_eq_m128i($op($vec_res, 0), $lin_res[0]);
            };
        }

        // this function tests one of the possible 4 instances
        // with different inputs across lanes
        #[target_feature(enable = "avx512vpclmulqdq,avx512f")]
        unsafe fn verify_512_helper(
            linear: unsafe fn(__m128i, __m128i) -> __m128i,
            vectorized: unsafe fn(__m512i, __m512i) -> __m512i,
        ) {
            let a = _mm512_set_epi64(
                0xDCB4DB3657BF0B7D,
                0x18DB0601068EDD9F,
                0xB76B908233200DC5,
                0xE478235FA8E22D5E,
                0xAB05CFFA2621154C,
                0x1171B47A186174C9,
                0x8C6B6C0E7595CEC9,
                0xBE3E7D4934E961BD,
            );
            let b = _mm512_set_epi64(
                0x672F6F105A94CEA7,
                0x8298B8FFCA5F829C,
                0xA3927047B3FB61D8,
                0x978093862CDE7187,
                0xB1927AB22F31D0EC,
                0xA9A5DA619BE4D7AF,
                0xCA2590F56884FDC6,
                0x19BE9F660038BDB5,
            );

            let mut a_decomp = [_mm_setzero_si128(); 4];
            unroll! {a_decomp[4] = _mm512_extracti32x4_epi32(a,4);}
            let mut b_decomp = [_mm_setzero_si128(); 4];
            unroll! {b_decomp[4] = _mm512_extracti32x4_epi32(b,4);}

            let r = vectorized(a, b);
            let mut e_decomp = [_mm_setzero_si128(); 4];
            for i in 0..4 {
                e_decomp[i] = linear(a_decomp[i], b_decomp[i]);
            }
            unroll! {assert_eq_m128i(_mm512_extracti32x4_epi32(r,4),e_decomp[4]);}
        }

        // this function tests one of the possible 4 instances
        // with different inputs across lanes for the VL version
        #[target_feature(enable = "avx512vpclmulqdq,avx512vl")]
        unsafe fn verify_256_helper(
            linear: unsafe fn(__m128i, __m128i) -> __m128i,
            vectorized: unsafe fn(__m256i, __m256i) -> __m256i,
        ) {
            let a = _mm512_set_epi64(
                0xDCB4DB3657BF0B7D,
                0x18DB0601068EDD9F,
                0xB76B908233200DC5,
                0xE478235FA8E22D5E,
                0xAB05CFFA2621154C,
                0x1171B47A186174C9,
                0x8C6B6C0E7595CEC9,
                0xBE3E7D4934E961BD,
            );
            let b = _mm512_set_epi64(
                0x672F6F105A94CEA7,
                0x8298B8FFCA5F829C,
                0xA3927047B3FB61D8,
                0x978093862CDE7187,
                0xB1927AB22F31D0EC,
                0xA9A5DA619BE4D7AF,
                0xCA2590F56884FDC6,
                0x19BE9F660038BDB5,
            );

            let mut a_decomp = [_mm_setzero_si128(); 2];
            unroll! {a_decomp[2] = _mm512_extracti32x4_epi32(a,2);}
            let mut b_decomp = [_mm_setzero_si128(); 2];
            unroll! {b_decomp[2] = _mm512_extracti32x4_epi32(b,2);}

            let r = vectorized(
                _mm512_extracti64x4_epi64(a, 0),
                _mm512_extracti64x4_epi64(b, 0),
            );
            let mut e_decomp = [_mm_setzero_si128(); 2];
            for i in 0..2 {
                e_decomp[i] = linear(a_decomp[i], b_decomp[i]);
            }
            unroll! {assert_eq_m128i(_mm256_extracti128_si256(r,2),e_decomp[2]);}
        }

        #[simd_test(enable = "avx512vpclmulqdq,avx512f")]
        unsafe fn test_mm512_clmulepi64_epi128() {
            verify_kat_pclmul!(
                _mm512_broadcast_i32x4,
                _mm512_clmulepi64_epi128,
                assert_eq_m512i
            );

            verify_512_helper(
                |a, b| _mm_clmulepi64_si128(a, b, 0x00),
                |a, b| _mm512_clmulepi64_epi128(a, b, 0x00),
            );
            verify_512_helper(
                |a, b| _mm_clmulepi64_si128(a, b, 0x01),
                |a, b| _mm512_clmulepi64_epi128(a, b, 0x01),
            );
            verify_512_helper(
                |a, b| _mm_clmulepi64_si128(a, b, 0x10),
                |a, b| _mm512_clmulepi64_epi128(a, b, 0x10),
            );
            verify_512_helper(
                |a, b| _mm_clmulepi64_si128(a, b, 0x11),
                |a, b| _mm512_clmulepi64_epi128(a, b, 0x11),
            );
        }

        #[simd_test(enable = "avx512vpclmulqdq,avx512vl")]
        unsafe fn test_mm256_clmulepi64_epi128() {
            verify_kat_pclmul!(
                _mm256_broadcastsi128_si256,
                _mm256_clmulepi64_epi128,
                assert_eq_m256i
            );

            verify_256_helper(
                |a, b| _mm_clmulepi64_si128(a, b, 0x00),
                |a, b| _mm256_clmulepi64_epi128(a, b, 0x00),
            );
            verify_256_helper(
                |a, b| _mm_clmulepi64_si128(a, b, 0x01),
                |a, b| _mm256_clmulepi64_epi128(a, b, 0x01),
            );
            verify_256_helper(
                |a, b| _mm_clmulepi64_si128(a, b, 0x10),
                |a, b| _mm256_clmulepi64_epi128(a, b, 0x10),
            );
            verify_256_helper(
                |a, b| _mm_clmulepi64_si128(a, b, 0x11),
                |a, b| _mm256_clmulepi64_epi128(a, b, 0x11),
            );
        }
    }