EXPERIMENTAL: Metal backend (#441)

This is not a continuation of the Metal backend; this is simply bringing
the branch up to date and merging it as-is behind an experiment.

---------

Co-authored-by: Isaac Marovitz <isaacryu@icloud.com>
Co-authored-by: Samuliak <samuliak77@gmail.com>
Co-authored-by: SamoZ256 <96914946+SamoZ256@users.noreply.github.com>
Co-authored-by: Isaac Marovitz <42140194+IsaacMarovitz@users.noreply.github.com>
Co-authored-by: riperiperi <rhy3756547@hotmail.com>
Co-authored-by: Gabriel A <gab.dark.100@gmail.com>

src/Ryujinx.Graphics.Metal/Auto.cs

@@ -0,0 +1,146 @@
+using System;
+using System.Diagnostics;
+using System.Runtime.Versioning;
+using System.Threading;
+
+namespace Ryujinx.Graphics.Metal
+{
+    interface IAuto
+    {
+        bool HasCommandBufferDependency(CommandBufferScoped cbs);
+
+        void IncrementReferenceCount();
+        void DecrementReferenceCount(int cbIndex);
+        void DecrementReferenceCount();
+    }
+
+    interface IAutoPrivate : IAuto
+    {
+        void AddCommandBufferDependencies(CommandBufferScoped cbs);
+    }
+
+    [SupportedOSPlatform("macos")]
+    class Auto<T> : IAutoPrivate, IDisposable where T : IDisposable
+    {
+        private int _referenceCount;
+        private T _value;
+
+        private readonly BitMap _cbOwnership;
+        private readonly MultiFenceHolder _waitable;
+
+        private bool _disposed;
+        private bool _destroyed;
+
+        public Auto(T value)
+        {
+            _referenceCount = 1;
+            _value = value;
+            _cbOwnership = new BitMap(CommandBufferPool.MaxCommandBuffers);
+        }
+
+        public Auto(T value, MultiFenceHolder waitable) : this(value)
+        {
+            _waitable = waitable;
+        }
+
+        public T Get(CommandBufferScoped cbs, int offset, int size, bool write = false)
+        {
+            _waitable?.AddBufferUse(cbs.CommandBufferIndex, offset, size, write);
+            return Get(cbs);
+        }
+
+        public T GetUnsafe()
+        {
+            return _value;
+        }
+
+        public T Get(CommandBufferScoped cbs)
+        {
+            if (!_destroyed)
+            {
+                AddCommandBufferDependencies(cbs);
+            }
+
+            return _value;
+        }
+
+        public bool HasCommandBufferDependency(CommandBufferScoped cbs)
+        {
+            return _cbOwnership.IsSet(cbs.CommandBufferIndex);
+        }
+
+        public bool HasRentedCommandBufferDependency(CommandBufferPool cbp)
+        {
+            return _cbOwnership.AnySet();
+        }
+
+        public void AddCommandBufferDependencies(CommandBufferScoped cbs)
+        {
+            // We don't want to add a reference to this object to the command buffer
+            // more than once, so if we detect that the command buffer already has ownership
+            // of this object, then we can just return without doing anything else.
+            if (_cbOwnership.Set(cbs.CommandBufferIndex))
+            {
+                if (_waitable != null)
+                {
+                    cbs.AddWaitable(_waitable);
+                }
+
+                cbs.AddDependant(this);
+            }
+        }
+
+        public bool TryIncrementReferenceCount()
+        {
+            int lastValue;
+            do
+            {
+                lastValue = _referenceCount;
+
+                if (lastValue == 0)
+                {
+                    return false;
+                }
+            }
+            while (Interlocked.CompareExchange(ref _referenceCount, lastValue + 1, lastValue) != lastValue);
+
+            return true;
+        }
+
+        public void IncrementReferenceCount()
+        {
+            if (Interlocked.Increment(ref _referenceCount) == 1)
+            {
+                Interlocked.Decrement(ref _referenceCount);
+                throw new InvalidOperationException("Attempted to increment the reference count of an object that was already destroyed.");
+            }
+        }
+
+        public void DecrementReferenceCount(int cbIndex)
+        {
+            _cbOwnership.Clear(cbIndex);
+            DecrementReferenceCount();
+        }
+
+        public void DecrementReferenceCount()
+        {
+            if (Interlocked.Decrement(ref _referenceCount) == 0)
+            {
+                _value.Dispose();
+                _value = default;
+                _destroyed = true;
+            }
+
+            Debug.Assert(_referenceCount >= 0);
+        }
+
+        public void Dispose()
+        {
+            if (!_disposed)
+            {
+                DecrementReferenceCount();
+                _disposed = true;
+            }
+        }
+    }
+}