Add 4 Channel Shuffle Intrinsics

src/ImageSharp/Common/Helpers/IComponentShuffle.cs

@@ -0,0 +1,165 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+using System.Buffers.Binary;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace SixLabors.ImageSharp
+{
+    /// <summary>
+    /// Defines the contract for methods that allow the shuffling of pixel components.
+    /// Used for shuffling on platforms that do not support Hardware Intrinsics.
+    /// </summary>
+    internal interface IComponentShuffle
+    {
+        /// <summary>
+        /// Gets the shuffle control.
+        /// </summary>
+        byte Control { get; }
+
+        /// <summary>
+        /// Shuffle 8-bit integers within 128-bit lanes in <paramref name="source"/>
+        /// using the control and store the results in <paramref name="dest"/>.
+        /// </summary>
+        /// <param name="source">The source span of bytes.</param>
+        /// <param name="dest">The destination span of bytes.</param>
+        void RunFallbackShuffle(ReadOnlySpan<byte> source, Span<byte> dest);
+    }
+
+    internal readonly struct DefaultShuffle4 : IComponentShuffle
+    {
+        public DefaultShuffle4(byte p3, byte p2, byte p1, byte p0)
+            : this(SimdUtils.Shuffle.MmShuffle(p3, p2, p1, p0))
+        {
+        }
+
+        public DefaultShuffle4(byte control) => this.Control = control;
+
+        public byte Control { get; }
+
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void RunFallbackShuffle(ReadOnlySpan<byte> source, Span<byte> dest)
+        {
+            ref byte sBase = ref MemoryMarshal.GetReference(source);
+            ref byte dBase = ref MemoryMarshal.GetReference(dest);
+            SimdUtils.Shuffle.InverseMmShuffle(
+                this.Control,
+                out int p3,
+                out int p2,
+                out int p1,
+                out int p0);
+
+            for (int i = 0; i < source.Length; i += 4)
+            {
+                Unsafe.Add(ref dBase, i) = Unsafe.Add(ref sBase, p0 + i);
+                Unsafe.Add(ref dBase, i + 1) = Unsafe.Add(ref sBase, p1 + i);
+                Unsafe.Add(ref dBase, i + 2) = Unsafe.Add(ref sBase, p2 + i);
+                Unsafe.Add(ref dBase, i + 3) = Unsafe.Add(ref sBase, p3 + i);
+            }
+        }
+    }
+
+    internal readonly struct WXYZShuffle4 : IComponentShuffle
+    {
+        public byte Control => SimdUtils.Shuffle.MmShuffle(2, 1, 0, 3);
+
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void RunFallbackShuffle(ReadOnlySpan<byte> source, Span<byte> dest)
+        {
+            ReadOnlySpan<uint> s = MemoryMarshal.Cast<byte, uint>(source);
+            Span<uint> d = MemoryMarshal.Cast<byte, uint>(dest);
+            ref uint sBase = ref MemoryMarshal.GetReference(s);
+            ref uint dBase = ref MemoryMarshal.GetReference(d);
+
+            // The JIT can detect and optimize rotation idioms ROTL (Rotate Left)
+            // and ROTR (Rotate Right) emitting efficient CPU instructions:
+            // https://github.com/dotnet/coreclr/pull/1830
+            for (int i = 0; i < s.Length; i++)
+            {
+                uint packed = Unsafe.Add(ref sBase, i);
+
+                // packed          = [W Z Y X]
+                // ROTL(8, packed) = [Z Y X W]
+                Unsafe.Add(ref dBase, i) = (packed << 8) | (packed >> 24);
+            }
+        }
+    }
+
+    internal readonly struct WZYXShuffle4 : IComponentShuffle
+    {
+        public byte Control => SimdUtils.Shuffle.MmShuffle(0, 1, 2, 3);
+
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void RunFallbackShuffle(ReadOnlySpan<byte> source, Span<byte> dest)
+        {
+            ReadOnlySpan<uint> s = MemoryMarshal.Cast<byte, uint>(source);
+            Span<uint> d = MemoryMarshal.Cast<byte, uint>(dest);
+            ref uint sBase = ref MemoryMarshal.GetReference(s);
+            ref uint dBase = ref MemoryMarshal.GetReference(d);
+
+            for (int i = 0; i < s.Length; i++)
+            {
+                uint packed = Unsafe.Add(ref sBase, i);
+
+                // packed              = [W Z Y X]
+                // REVERSE(packedArgb) = [X Y Z W]
+                Unsafe.Add(ref dBase, i) = BinaryPrimitives.ReverseEndianness(packed);
+            }
+        }
+    }
+
+    internal readonly struct YZWXShuffle4 : IComponentShuffle
+    {
+        public byte Control => SimdUtils.Shuffle.MmShuffle(0, 3, 2, 1);
+
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void RunFallbackShuffle(ReadOnlySpan<byte> source, Span<byte> dest)
+        {
+            ReadOnlySpan<uint> s = MemoryMarshal.Cast<byte, uint>(source);
+            Span<uint> d = MemoryMarshal.Cast<byte, uint>(dest);
+            ref uint sBase = ref MemoryMarshal.GetReference(s);
+            ref uint dBase = ref MemoryMarshal.GetReference(d);
+
+            for (int i = 0; i < s.Length; i++)
+            {
+                uint packed = Unsafe.Add(ref sBase, i);
+
+                // packed              = [W Z Y X]
+                // ROTR(8, packedArgb) = [Y Z W X]
+                Unsafe.Add(ref dBase, i) = (packed >> 8) | (packed << 24);
+            }
+        }
+    }
+
+    internal readonly struct ZYXWShuffle4 : IComponentShuffle
+    {
+        public byte Control => SimdUtils.Shuffle.MmShuffle(3, 0, 1, 2);
+
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void RunFallbackShuffle(ReadOnlySpan<byte> source, Span<byte> dest)
+        {
+            ReadOnlySpan<uint> s = MemoryMarshal.Cast<byte, uint>(source);
+            Span<uint> d = MemoryMarshal.Cast<byte, uint>(dest);
+            ref uint sBase = ref MemoryMarshal.GetReference(s);
+            ref uint dBase = ref MemoryMarshal.GetReference(d);
+
+            for (int i = 0; i < s.Length; i++)
+            {
+                uint packed = Unsafe.Add(ref sBase, i);
+
+                // packed              = [W Z Y X]
+                // tmp1                = [W 0 Y 0]
+                // tmp2                = [0 Z 0 X]
+                // tmp3=ROTL(16, tmp2) = [0 X 0 Z]
+                // tmp1 + tmp3         = [W X Y Z]
+                uint tmp1 = packed & 0xFF00FF00;
+                uint tmp2 = packed & 0x00FF00FF;
+                uint tmp3 = (tmp2 << 16) | (tmp2 >> 16);
+
+                Unsafe.Add(ref dBase, i) = tmp1 + tmp3;
+            }
+        }
+    }
+}