Add AVX2 version of Vp8_Sse16X16 and Vp8_Sse16X8

src/ImageSharp/Formats/Webp/Lossy/LossyUtils.cs

@@ -43,6 +43,11 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
         public static int Vp8_Sse16X16(Span<byte> a, Span<byte> b)
         {
 #if SUPPORTS_RUNTIME_INTRINSICS
+            if (Avx2.IsSupported)
+            {
+                return Vp8_Sse16xN_Avx2(a, b, 4);
+            }
+
             if (Sse2.IsSupported)
             {
                 return Vp8_Sse16xN_Sse2(a, b, 8);
@@ -58,6 +63,11 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
         public static int Vp8_Sse16X8(Span<byte> a, Span<byte> b)
         {
 #if SUPPORTS_RUNTIME_INTRINSICS
+            if (Avx2.IsSupported)
+            {
+                return Vp8_Sse16xN_Avx2(a, b, 2);
+            }
+
             if (Sse2.IsSupported)
             {
                 return Vp8_Sse16xN_Sse2(a, b, 4);
@@ -194,6 +204,39 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
             return Numerics.ReduceSum(sum);
         }
 
+        [MethodImpl(InliningOptions.ShortMethod)]
+        private static int Vp8_Sse16xN_Avx2(Span<byte> a, Span<byte> b, int numPairs)
+        {
+            Vector256<int> sum = Vector256<int>.Zero;
+            int offset = 0;
+            for (int i = 0; i < numPairs; i++)
+            {
+                // Load values.
+                ref byte aRef = ref MemoryMarshal.GetReference(a);
+                ref byte bRef = ref MemoryMarshal.GetReference(b);
+                var a0 = Vector256.Create(
+                    Unsafe.As<byte, Vector128<byte>>(ref Unsafe.Add(ref aRef, offset)),
+                    Unsafe.As<byte, Vector128<byte>>(ref Unsafe.Add(ref aRef, offset + WebpConstants.Bps)));
+                var b0 = Vector256.Create(
+                    Unsafe.As<byte, Vector128<byte>>(ref Unsafe.Add(ref bRef, offset)),
+                    Unsafe.As<byte, Vector128<byte>>(ref Unsafe.Add(ref bRef, offset + WebpConstants.Bps)));
+                var a1 = Vector256.Create(
+                    Unsafe.As<byte, Vector128<byte>>(ref Unsafe.Add(ref aRef, offset + (2 * WebpConstants.Bps))),
+                    Unsafe.As<byte, Vector128<byte>>(ref Unsafe.Add(ref aRef, offset + (3 * WebpConstants.Bps))));
+                var b1 = Vector256.Create(
+                    Unsafe.As<byte, Vector128<byte>>(ref Unsafe.Add(ref bRef, offset + (2 * WebpConstants.Bps))),
+                    Unsafe.As<byte, Vector128<byte>>(ref Unsafe.Add(ref bRef, offset + (3 * WebpConstants.Bps))));
+
+                Vector256<int> sum1 = SubtractAndAccumulate(a0, b0);
+                Vector256<int> sum2 = SubtractAndAccumulate(a1, b1);
+                sum = Avx2.Add(sum, Avx2.Add(sum1, sum2));
+
+                offset += 4 * WebpConstants.Bps;
+            }
+
+            return Numerics.ReduceSum(sum);
+        }
+
         [MethodImpl(InliningOptions.ShortMethod)]
         private static Vector128<int> SubtractAndAccumulate(Vector128<byte> a, Vector128<byte> b)
         {
@@ -212,6 +255,25 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
 
             return Sse2.Add(sum1, sum2);
         }
+
+        [MethodImpl(InliningOptions.ShortMethod)]
+        private static Vector256<int> SubtractAndAccumulate(Vector256<byte> a, Vector256<byte> b)
+        {
+            // Take abs(a-b) in 8b.
+            Vector256<byte> ab = Avx2.SubtractSaturate(a, b);
+            Vector256<byte> ba = Avx2.SubtractSaturate(b, a);
+            Vector256<byte> absAb = Avx2.Or(ab, ba);
+
+            // Zero-extend to 16b.
+            Vector256<byte> c0 = Avx2.UnpackLow(absAb, Vector256<byte>.Zero);
+            Vector256<byte> c1 = Avx2.UnpackHigh(absAb, Vector256<byte>.Zero);
+
+            // Multiply with self.
+            Vector256<int> sum1 = Avx2.MultiplyAddAdjacent(c0.AsInt16(), c0.AsInt16());
+            Vector256<int> sum2 = Avx2.MultiplyAddAdjacent(c1.AsInt16(), c1.AsInt16());
+
+            return Avx2.Add(sum1, sum2);
+        }
 #endif
 
         [MethodImpl(InliningOptions.ShortMethod)]

tests/ImageSharp.Tests/Formats/WebP/LossyUtilsTests.cs

@@ -320,12 +320,18 @@ namespace SixLabors.ImageSharp.Tests.Formats.Webp
         [Fact]
         public void Vp8Sse16X16_WithoutSSE2_Works() => FeatureTestRunner.RunWithHwIntrinsicsFeature(RunVp8Sse16X16Test, HwIntrinsics.DisableSSE2);
 
+        [Fact]
+        public void Vp8Sse16X16_WithoutAVX2_Works() => FeatureTestRunner.RunWithHwIntrinsicsFeature(RunVp8Sse16X16Test, HwIntrinsics.DisableAVX2);
+
         [Fact]
         public void Vp8Sse16X8_WithHardwareIntrinsics_Works() => FeatureTestRunner.RunWithHwIntrinsicsFeature(RunVp8Sse16X8Test, HwIntrinsics.AllowAll);
 
         [Fact]
         public void Vp8Sse16X8_WithoutSSE2_Works() => FeatureTestRunner.RunWithHwIntrinsicsFeature(RunVp8Sse16X8Test, HwIntrinsics.DisableSSE2);
 
+        [Fact]
+        public void Vp8Sse16X8_WithoutAVX2_Works() => FeatureTestRunner.RunWithHwIntrinsicsFeature(RunVp8Sse16X8Test, HwIntrinsics.DisableAVX2);
+
         [Fact]
         public void Vp8Sse4X4_WithHardwareIntrinsics_Works() => FeatureTestRunner.RunWithHwIntrinsicsFeature(RunVp8Sse4X4Test, HwIntrinsics.AllowAll);