mirror of https://github.com/SixLabors/ImageSharp
Anton Firszov
8 years ago
9 changed files with 256 additions and 48 deletions
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using System; |
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using System.Numerics; |
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using System.Runtime.CompilerServices; |
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using System.Runtime.InteropServices; |
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namespace SixLabors.ImageSharp |
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{ |
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internal static partial class SimdUtils |
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{ |
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/// <summary>
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/// Fallback implementation based on <see cref="Vector4"/> (128bit).
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/// For <see cref="Vector4"/>, efficient software fallback implementations are present
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/// + maybe even mono can emit intrinsics for that type :P
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/// </summary>
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public static class FallbackIntrinsics128 |
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{ |
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/// <summary>
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/// <see cref="BulkConvertByteToNormalizedFloat"/> as much elements as possible, slicing them down (keeping the remainder).
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/// </summary>
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internal static void BulkConvertByteToNormalizedFloatReduce( |
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ref ReadOnlySpan<byte> source, |
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ref Span<float> dest) |
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{ |
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DebugGuard.IsTrue(source.Length == dest.Length, nameof(source), "Input spans must be of same size!"); |
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int remainder = source.Length % 4; |
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int alignedCount = source.Length - remainder; |
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if (alignedCount > 0) |
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{ |
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BulkConvertByteToNormalizedFloat( |
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source.Slice(0, alignedCount), |
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dest.Slice(0, alignedCount)); |
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source = source.Slice(alignedCount); |
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dest = dest.Slice(alignedCount); |
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} |
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} |
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/// <summary>
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/// <see cref="BulkConvertNormalizedFloatToByteClampOverflows"/> as much elements as possible, slicing them down (keeping the remainder).
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/// </summary>
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internal static void BulkConvertNormalizedFloatToByteClampOverflowsReduce( |
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ref ReadOnlySpan<float> source, |
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ref Span<byte> dest) |
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{ |
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DebugGuard.IsTrue(source.Length == dest.Length, nameof(source), "Input spans must be of same size!"); |
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int remainder = source.Length % 4; |
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int alignedCount = source.Length - remainder; |
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if (alignedCount > 0) |
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{ |
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BulkConvertNormalizedFloatToByteClampOverflows( |
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source.Slice(0, alignedCount), |
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dest.Slice(0, alignedCount)); |
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source = source.Slice(alignedCount); |
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dest = dest.Slice(alignedCount); |
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} |
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} |
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/// <summary>
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/// Implementation of <see cref="SimdUtils.BulkConvertByteToNormalizedFloat"/> using <see cref="Vector4"/>.
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/// </summary>
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internal static void BulkConvertByteToNormalizedFloat(ReadOnlySpan<byte> source, Span<float> dest) |
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{ |
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DebugGuard.IsTrue((dest.Length % 4) == 0, nameof(dest), "dest.Length should be divisible by 4!"); |
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int count = dest.Length / 4; |
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if (count == 0) |
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{ |
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return; |
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} |
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ref ByteVector4 sBase = ref Unsafe.As<byte, ByteVector4>(ref MemoryMarshal.GetReference(source)); |
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ref Vector4 dBase = ref Unsafe.As<float, Vector4>(ref MemoryMarshal.GetReference(dest)); |
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const float Scale = 1f / 255f; |
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Vector4 d = default; |
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for (int i = 0; i < count; i++) |
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{ |
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ref ByteVector4 s = ref Unsafe.Add(ref sBase, i); |
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d.X = s.X; |
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d.Y = s.Y; |
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d.Z = s.Z; |
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d.W = s.W; |
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d *= Scale; |
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Unsafe.Add(ref dBase, i) = d; |
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} |
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} |
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/// <summary>
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/// Implementation of <see cref="SimdUtils.BulkConvertNormalizedFloatToByteClampOverflows"/> using <see cref="Vector4"/>.
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/// </summary>
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internal static void BulkConvertNormalizedFloatToByteClampOverflows( |
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ReadOnlySpan<float> source, |
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Span<byte> dest) |
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{ |
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DebugGuard.IsTrue((source.Length % 4) == 0, nameof(source), "source.Length should be divisible by 4!"); |
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int count = source.Length / 4; |
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if (count == 0) |
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{ |
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return; |
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} |
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ref Vector4 sBase = ref Unsafe.As<float, Vector4>(ref MemoryMarshal.GetReference(source)); |
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ref ByteVector4 dBase = ref Unsafe.As<byte, ByteVector4>(ref MemoryMarshal.GetReference(dest)); |
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var half = new Vector4(0.5f); |
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var maxBytes = new Vector4(255f); |
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for (int i = 0; i < count; i++) |
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{ |
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Vector4 s = Unsafe.Add(ref sBase, i); |
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s *= maxBytes; |
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s += half; |
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// I'm not sure if Clamp() is properly implemented with intrinsics.
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s = Vector4.Max(Vector4.Zero, s); |
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s = Vector4.Min(maxBytes, s); |
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ref ByteVector4 d = ref Unsafe.Add(ref dBase, i); |
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d.X = (byte)s.X; |
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d.Y = (byte)s.Y; |
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d.Z = (byte)s.Z; |
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d.W = (byte)s.W; |
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} |
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} |
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[StructLayout(LayoutKind.Sequential)] |
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private struct ByteVector4 |
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{ |
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public byte X; |
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public byte Y; |
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public byte Z; |
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public byte W; |
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} |
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} |
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} |
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} |
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