Add AVX2 Vector4Octet.Pack implementation

src/ImageSharp/Common/Helpers/SimdUtils.HwIntrinsics.cs

@@ -14,7 +14,32 @@ internal static partial class SimdUtils
     {
         public static class HwIntrinsics
         {
-            private static ReadOnlySpan<byte> PermuteMaskDeinterleave8x32 => new byte[] { 0, 0, 0, 0, 4, 0, 0, 0, 1, 0, 0, 0, 5, 0, 0, 0, 2, 0, 0, 0, 6, 0, 0, 0, 3, 0, 0, 0, 7, 0, 0, 0 };
+            public static ReadOnlySpan<byte> PermuteMaskDeinterleave8x32 => new byte[] { 0, 0, 0, 0, 4, 0, 0, 0, 1, 0, 0, 0, 5, 0, 0, 0, 2, 0, 0, 0, 6, 0, 0, 0, 3, 0, 0, 0, 7, 0, 0, 0 };
+
+            public static ReadOnlySpan<byte> PermuteMaskEvenOdd8x32 => new byte[] { 0, 0, 0, 0, 2, 0, 0, 0, 4, 0, 0, 0, 6, 0, 0, 0, 1, 0, 0, 0, 3, 0, 0, 0, 5, 0, 0, 0, 7, 0, 0, 0 };
+
+            /// <summary>
+            /// Performs a multiplication and an addition of the <see cref="Vector256{T}"/>.
+            /// </summary>
+            /// <param name="va">The vector to add to the intermediate result.</param>
+            /// <param name="vm0">The first vector to multiply.</param>
+            /// <param name="vm1">The second vector to multiply.</param>
+            /// <returns>The <see cref="Vector256{T}"/>.</returns>
+            [MethodImpl(InliningOptions.ShortMethod)]
+            public static Vector256<float> MultiplyAdd(
+                in Vector256<float> va,
+                in Vector256<float> vm0,
+                in Vector256<float> vm1)
+            {
+                if (Fma.IsSupported)
+                {
+                    return Fma.MultiplyAdd(vm1, vm0, va);
+                }
+                else
+                {
+                    return Avx.Add(Avx.Multiply(vm0, vm1), va);
+                }
+            }
 
             /// <summary>
             /// <see cref="ByteToNormalizedFloat"/> as many elements as possible, slicing them down (keeping the remainder).

src/ImageSharp/Formats/Jpeg/Components/Decoder/ColorConverters/JpegColorConverter.FromYCbCrSimdAvx2.cs

@@ -1,11 +1,15 @@
-// Copyright (c) Six Labors.
+// Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
 using System;
 using System.Numerics;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
-
+#if SUPPORTS_RUNTIME_INTRINSICS
+using System.Runtime.Intrinsics;
+using System.Runtime.Intrinsics.X86;
+using static SixLabors.ImageSharp.SimdUtils;
+#endif
 using SixLabors.ImageSharp.Tuples;
 
 // ReSharper disable ImpureMethodCallOnReadonlyValueField
@@ -47,6 +51,73 @@ internal static void ConvertCore(in ComponentValues values, Span<Vector4> result
                         "JpegColorConverter.FromYCbCrSimd256 can be used only on architecture having 256 byte floating point SIMD registers!");
                 }
 
+#if SUPPORTS_RUNTIME_INTRINSICS
+                ref Vector256<float> yBase =
+                    ref Unsafe.As<float, Vector256<float>>(ref MemoryMarshal.GetReference(values.Component0));
+                ref Vector256<float> cbBase =
+                    ref Unsafe.As<float, Vector256<float>>(ref MemoryMarshal.GetReference(values.Component1));
+                ref Vector256<float> crBase =
+                    ref Unsafe.As<float, Vector256<float>>(ref MemoryMarshal.GetReference(values.Component2));
+
+                ref Vector256<float> resultBase =
+                    ref Unsafe.As<Vector4, Vector256<float>>(ref MemoryMarshal.GetReference(result));
+
+                // Used for the color conversion
+                var chromaOffset = Vector256.Create(-halfValue);
+                var scale = Vector256.Create(1 / maxValue);
+                var rCrMult = Vector256.Create(1.402F);
+                var gCbMult = Vector256.Create(-0.344136F);
+                var gCrMult = Vector256.Create(-0.714136F);
+                var bCbMult = Vector256.Create(1.772F);
+
+                // Used for packing.
+                var va = Vector256.Create(1F);
+                ref byte control = ref MemoryMarshal.GetReference(HwIntrinsics.PermuteMaskEvenOdd8x32);
+                Vector256<int> vcontrol = Unsafe.As<byte, Vector256<int>>(ref control);
+
+                // Walking 8 elements at one step:
+                int n = result.Length / 8;
+                for (int i = 0; i < n; i++)
+                {
+                    // y = yVals[i];
+                    // cb = cbVals[i] - 128F;
+                    // cr = crVals[i] - 128F;
+                    Vector256<float> y = Unsafe.Add(ref yBase, i);
+                    Vector256<float> cb = Avx.Add(Unsafe.Add(ref cbBase, i), chromaOffset);
+                    Vector256<float> cr = Avx.Add(Unsafe.Add(ref crBase, i), chromaOffset);
+
+                    y = Avx2.PermuteVar8x32(y, vcontrol);
+                    cb = Avx2.PermuteVar8x32(cb, vcontrol);
+                    cr = Avx2.PermuteVar8x32(cr, vcontrol);
+
+                    // r = y + (1.402F * cr);
+                    // g = y - (0.344136F * cb) - (0.714136F * cr);
+                    // b = y + (1.772F * cb);
+                    // Adding & multiplying 8 elements at one time:
+                    Vector256<float> r = HwIntrinsics.MultiplyAdd(y, cr, rCrMult);
+                    Vector256<float> g = HwIntrinsics.MultiplyAdd(HwIntrinsics.MultiplyAdd(y, cb, gCbMult), cr, gCrMult);
+                    Vector256<float> b = HwIntrinsics.MultiplyAdd(y, cb, bCbMult);
+
+                    // TODO: We should be savving to RGBA not Vector4
+                    r = Avx.Multiply(Avx.RoundToNearestInteger(r), scale);
+                    g = Avx.Multiply(Avx.RoundToNearestInteger(g), scale);
+                    b = Avx.Multiply(Avx.RoundToNearestInteger(b), scale);
+
+                    Vector256<float> vte = Avx.UnpackLow(r, b);
+                    Vector256<float> vto = Avx.UnpackLow(g, va);
+
+                    ref Vector256<float> destination = ref Unsafe.Add(ref resultBase, i * 4);
+
+                    destination = Avx.UnpackLow(vte, vto);
+                    Unsafe.Add(ref destination, 1) = Avx.UnpackHigh(vte, vto);
+
+                    vte = Avx.UnpackHigh(r, b);
+                    vto = Avx.UnpackHigh(g, va);
+
+                    Unsafe.Add(ref destination, 2) = Avx.UnpackLow(vte, vto);
+                    Unsafe.Add(ref destination, 3) = Avx.UnpackHigh(vte, vto);
+                }
+#else
                 ref Vector<float> yBase =
                     ref Unsafe.As<float, Vector<float>>(ref MemoryMarshal.GetReference(values.Component0));
                 ref Vector<float> cbBase =
@@ -104,6 +175,7 @@ internal static void ConvertCore(in ComponentValues values, Span<Vector4> result
                     ref Vector4Octet destination = ref Unsafe.Add(ref resultBase, i);
                     destination.Pack(ref rr, ref gg, ref bb);
                 }
+#endif
             }
         }
     }

src/ImageSharp/Formats/Jpeg/Components/Decoder/ColorConverters/JpegColorConverter.cs

@@ -4,7 +4,6 @@
 using System;
 using System.Collections.Generic;
 using System.Numerics;
-
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.Tuples;
 

tests/ImageSharp.Benchmarks/Config.HwIntrinsics.cs

@@ -73,7 +73,9 @@ public HwIntrinsics_SSE_AVX()
                 }
 #endif
                 this.AddJob(Job.Default.WithRuntime(CoreRuntime.Core31)
-                    .WithEnvironmentVariables(new EnvironmentVariable(EnableHWIntrinsic, Off))
+                    .WithEnvironmentVariables(
+                        new EnvironmentVariable(EnableHWIntrinsic, Off),
+                        new EnvironmentVariable(FeatureSIMD, Off))
                     .WithId("No HwIntrinsics"));
             }
         }