A really really terrible (but worth while keeping around) version of an AVX Levenshtein calculator

Levenshtein.Avx.cs

#if NETCOREAPP3_0
using System;
using System.Runtime.CompilerServices;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;

namespace Quickenshtein
{
	public static partial class Levenshtein
	{

		[MethodImpl(MethodImplOptions.AggressiveInlining)]
		private static unsafe void CalculateDistance_Avx2(char sourcePrevChar, ushort* targetPtr, int targetLength, ref int lastInsertionCost, ref int lastSubstitutionCost, int* previousRowPtr, ref int columnIndex)
		{
			var sourcePrevCharVector = Vector128.Create(sourcePrevChar);
			var negationVector = Vector128.Create((ushort)1);
			var allOnesVector128 = Vector128.Create(1);
			var allOnesVector256 = Vector256.Create(1);

			while (targetLength >= 8)
			{
				targetLength -= 8;

				var targetCharVector = Sse3.LoadDquVector128(targetPtr + columnIndex);
				var notEqualVector = Sse2.AndNot(Sse2.CompareEqual(sourcePrevCharVector, targetCharVector), negationVector);
				var deletionCostsVector = Avx.LoadDquVector256(previousRowPtr + columnIndex);
				
				var substitutionCostsVector = Avx2.Subtract(deletionCostsVector, allOnesVector256);
				substitutionCostsVector = Avx2.Add(Avx2.ConvertToVector256Int32(notEqualVector), substitutionCostsVector);

				lastInsertionCost = Sse41.Min(
					Sse2.Add(
						Sse41.Min(
							Vector128.Create(lastInsertionCost, 0, 0, 0),
							Vector128.Create(deletionCostsVector.GetElement(0), 0, 0, 0)
						),
						allOnesVector128
					),
					Vector128.Create(substitutionCostsVector.GetElement(0), 0, 0, 0)
				).GetElement(0);
				previousRowPtr[columnIndex++] = lastInsertionCost;

				lastInsertionCost = Sse41.Min(
					Sse2.Add(
						Sse41.Min(
							Vector128.Create(lastInsertionCost, 0, 0, 0),
							Vector128.Create(deletionCostsVector.GetElement(1), 0, 0, 0)
						),
						allOnesVector128
					),
					Vector128.Create(substitutionCostsVector.GetElement(1), 0, 0, 0)
				).GetElement(0);
				previousRowPtr[columnIndex++] = lastInsertionCost;

				lastInsertionCost = Sse41.Min(
					Sse2.Add(
						Sse41.Min(
							Vector128.Create(lastInsertionCost, 0, 0, 0),
							Vector128.Create(deletionCostsVector.GetElement(2), 0, 0, 0)
						),
						allOnesVector128
					),
					Vector128.Create(substitutionCostsVector.GetElement(2), 0, 0, 0)
				).GetElement(0);
				previousRowPtr[columnIndex++] = lastInsertionCost;

				lastInsertionCost = Sse41.Min(
					Sse2.Add(
						Sse41.Min(
							Vector128.Create(lastInsertionCost, 0, 0, 0),
							Vector128.Create(deletionCostsVector.GetElement(3), 0, 0, 0)
						),
						allOnesVector128
					),
					Vector128.Create(substitutionCostsVector.GetElement(3), 0, 0, 0)
				).GetElement(0);
				previousRowPtr[columnIndex++] = lastInsertionCost;

				lastInsertionCost = Sse41.Min(
					Sse2.Add(
						Sse41.Min(
							Vector128.Create(lastInsertionCost, 0, 0, 0),
							Vector128.Create(deletionCostsVector.GetElement(4), 0, 0, 0)
						),
						allOnesVector128
					),
					Vector128.Create(substitutionCostsVector.GetElement(4), 0, 0, 0)
				).GetElement(0);
				previousRowPtr[columnIndex++] = lastInsertionCost;

				lastInsertionCost = Sse41.Min(
					Sse2.Add(
						Sse41.Min(
							Vector128.Create(lastInsertionCost, 0, 0, 0),
							Vector128.Create(deletionCostsVector.GetElement(5), 0, 0, 0)
						),
						allOnesVector128
					),
					Vector128.Create(substitutionCostsVector.GetElement(5), 0, 0, 0)
				).GetElement(0);
				previousRowPtr[columnIndex++] = lastInsertionCost;

				lastInsertionCost = Sse41.Min(
					Sse2.Add(
						Sse41.Min(
							Vector128.Create(lastInsertionCost, 0, 0, 0),
							Vector128.Create(deletionCostsVector.GetElement(6), 0, 0, 0)
						),
						allOnesVector128
					),
					Vector128.Create(substitutionCostsVector.GetElement(6), 0, 0, 0)
				).GetElement(0);
				previousRowPtr[columnIndex++] = lastInsertionCost;

				lastInsertionCost = Sse41.Min(
					Sse2.Add(
						Sse41.Min(
							Vector128.Create(lastInsertionCost, 0, 0, 0),
							Vector128.Create(deletionCostsVector.GetElement(7), 0, 0, 0)
						),
						allOnesVector128
					),
					Vector128.Create(substitutionCostsVector.GetElement(7), 0, 0, 0)
				).GetElement(0);
				previousRowPtr[columnIndex++] = lastInsertionCost;

				lastSubstitutionCost = deletionCostsVector.GetElement(7);
			}
		}
	}
}
#endif