Expert Checksum with AVX

crc32_expert_avx.cs

public static unsafe uint ChecksumExpertAvx(ReadOnlySpan<byte> arr)
{
        ref byte refSpan = ref MemoryMarshal.GetReference<byte>(arr);

        uint z = 0;            
        uint sum = 0;
        
        var vectorSum = Avx.Xor(Vector128<byte>.Zero, Vector128<byte>.Zero).AsUInt32();  
        var mask = Vector128.Create((byte)3, 2, 1, 0, 7, 6, 5, 4, 11, 10, 9, 8, 15, 14, 13, 12);

        int limit = arr.Length - 64;
        while (z <= limit)
        {                
            var v1 = Vector128.LoadUnsafe(ref Unsafe.Add(ref refSpan, z));
            var v2 = Vector128.LoadUnsafe(ref Unsafe.Add(ref refSpan, z+16));
            var v3 = Vector128.LoadUnsafe(ref Unsafe.Add(ref refSpan, z+32));
            var v4 = Vector128.LoadUnsafe(ref Unsafe.Add(ref refSpan, z+48));

            var s1 = Avx.Shuffle(v1, mask).AsUInt32();
            var s2 = Avx.Shuffle(v2, mask).AsUInt32();
            var s3 = Avx.Shuffle(v3, mask).AsUInt32();
            var s4 = Avx.Shuffle(v4, mask).AsUInt32();

            var s5 = Avx.Add(Avx.Add(s1, s2), Avx.Add(s3, s4));

            vectorSum = Avx.Add(vectorSum,s5);

            z += 64;
        }

       ...
}