ASTC optimizations (#845)

* ASTC optimizations

* Move code to Ryujinx.Common

* Support 3D textures

* Address feedback

* Remove ASTC logging

* Use stackalloc instead of a Buffer20 struct

* Code style and cleanup

* Respond to feedback

* Rearrange public/private property ordering

2 files changed, 120 insertions, 0 deletions

diff --git a/Ryujinx.Common/Utilities/Buffers.cs b/Ryujinx.Common/Utilities/Buffers.cs
new file mode 100644
index 00000000..d614bfc4
--- /dev/null
+++ b/Ryujinx.Common/Utilities/Buffers.cs
@@ -0,0 +1,59 @@
+using System;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.Common.Utilities
+{
+    [DebuggerDisplay("{ToString()}")]
+    [StructLayout(LayoutKind.Sequential, Size = 16)]
+    public struct Buffer16
+    {
+        [DebuggerBrowsable(DebuggerBrowsableState.Never)] private ulong _dummy0;
+        [DebuggerBrowsable(DebuggerBrowsableState.Never)] private ulong _dummy1;
+
+        public byte this[int i]
+        {
+            get => Bytes[i];
+            set => Bytes[i] = value;
+        }
+
+        public Span<byte> Bytes => SpanHelpers.AsByteSpan(ref this);
+
+        // Prevent a defensive copy by changing the read-only in reference to a reference with Unsafe.AsRef()
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static implicit operator Span<byte>(in Buffer16 value)
+        {
+            return SpanHelpers.AsByteSpan(ref Unsafe.AsRef(in value));
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static implicit operator ReadOnlySpan<byte>(in Buffer16 value)
+        {
+            return SpanHelpers.AsReadOnlyByteSpan(ref Unsafe.AsRef(in value));
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ref T As<T>() where T : unmanaged
+        {
+            if (Unsafe.SizeOf<T>() > (uint)Unsafe.SizeOf<Buffer16>())
+            {
+                throw new ArgumentException();
+            }
+
+            return ref MemoryMarshal.GetReference(AsSpan<T>());
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public Span<T> AsSpan<T>() where T : unmanaged
+        {
+            return SpanHelpers.AsSpan<Buffer16, T>(ref this);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public readonly ReadOnlySpan<T> AsReadOnlySpan<T>() where T : unmanaged
+        {
+            return SpanHelpers.AsReadOnlySpan<Buffer16, T>(ref Unsafe.AsRef(in this));
+        }
+    }
+}
diff --git a/Ryujinx.Common/Utilities/SpanHelpers.cs b/Ryujinx.Common/Utilities/SpanHelpers.cs
new file mode 100644
index 00000000..84c13023
--- /dev/null
+++ b/Ryujinx.Common/Utilities/SpanHelpers.cs
@@ -0,0 +1,61 @@
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.Common.Utilities
+{
+    public static class SpanHelpers
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Span<T> CreateSpan<T>(ref T reference, int length)
+        {
+            return MemoryMarshal.CreateSpan(ref reference, length);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Span<T> AsSpan<T>(ref T reference) where T : unmanaged
+        {
+            return CreateSpan(ref reference, 1);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Span<TSpan> AsSpan<TStruct, TSpan>(ref TStruct reference)
+            where TStruct : unmanaged where TSpan : unmanaged
+        {
+            return CreateSpan(ref Unsafe.As<TStruct, TSpan>(ref reference),
+                Unsafe.SizeOf<TStruct>() / Unsafe.SizeOf<TSpan>());
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Span<byte> AsByteSpan<T>(ref T reference) where T : unmanaged
+        {
+            return CreateSpan(ref Unsafe.As<T, byte>(ref reference), Unsafe.SizeOf<T>());
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ReadOnlySpan<T> CreateReadOnlySpan<T>(ref T reference, int length)
+        {
+            return MemoryMarshal.CreateReadOnlySpan(ref reference, length);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ReadOnlySpan<T> AsReadOnlySpan<T>(ref T reference) where T : unmanaged
+        {
+            return CreateReadOnlySpan(ref reference, 1);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ReadOnlySpan<TSpan> AsReadOnlySpan<TStruct, TSpan>(ref TStruct reference)
+            where TStruct : unmanaged where TSpan : unmanaged
+        {
+            return CreateReadOnlySpan(ref Unsafe.As<TStruct, TSpan>(ref reference),
+                Unsafe.SizeOf<TStruct>() / Unsafe.SizeOf<TSpan>());
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ReadOnlySpan<byte> AsReadOnlyByteSpan<T>(ref T reference) where T : unmanaged
+        {
+            return CreateReadOnlySpan(ref Unsafe.As<T, byte>(ref reference), Unsafe.SizeOf<T>());
+        }
+    }
+}