Move solution and projects to src

9 files changed, 1067 insertions, 0 deletions

diff --git a/src/ARMeilleure/Common/AddressTable.cs b/src/ARMeilleure/Common/AddressTable.cs
new file mode 100644
index 00000000..9db2d00d
--- /dev/null
+++ b/src/ARMeilleure/Common/AddressTable.cs
@@ -0,0 +1,252 @@
+using ARMeilleure.Diagnostics;
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+
+namespace ARMeilleure.Common
+{
+    /// <summary>
+    /// Represents a table of guest address to a value.
+    /// </summary>
+    /// <typeparam name="TEntry">Type of the value</typeparam>
+    unsafe class AddressTable<TEntry> : IDisposable where TEntry : unmanaged
+    {
+        /// <summary>
+        /// Represents a level in an <see cref="AddressTable{TEntry}"/>.
+        /// </summary>
+        public readonly struct Level
+        {
+            /// <summary>
+            /// Gets the index of the <see cref="Level"/> in the guest address.
+            /// </summary>
+            public int Index { get; }
+
+            /// <summary>
+            /// Gets the length of the <see cref="Level"/> in the guest address.
+            /// </summary>
+            public int Length { get; }
+
+            /// <summary>
+            /// Gets the mask which masks the bits used by the <see cref="Level"/>.
+            /// </summary>
+            public ulong Mask => ((1ul << Length) - 1) << Index;
+
+            /// <summary>
+            /// Initializes a new instance of the <see cref="Level"/> structure with the specified
+            /// <paramref name="index"/> and <paramref name="length"/>.
+            /// </summary>
+            /// <param name="index">Index of the <see cref="Level"/></param>
+            /// <param name="length">Length of the <see cref="Level"/></param>
+            public Level(int index, int length)
+            {
+                (Index, Length) = (index, length);
+            }
+
+            /// <summary>
+            /// Gets the value of the <see cref="Level"/> from the specified guest <paramref name="address"/>.
+            /// </summary>
+            /// <param name="address">Guest address</param>
+            /// <returns>Value of the <see cref="Level"/> from the specified guest <paramref name="address"/></returns>
+            public int GetValue(ulong address)
+            {
+                return (int)((address & Mask) >> Index);
+            }
+        }
+
+        private bool _disposed;
+        private TEntry** _table;
+        private readonly List<IntPtr> _pages;
+
+        /// <summary>
+        /// Gets the bits used by the <see cref="Levels"/> of the <see cref="AddressTable{TEntry}"/> instance.
+        /// </summary>
+        public ulong Mask { get; }
+
+        /// <summary>
+        /// Gets the <see cref="Level"/>s used by the <see cref="AddressTable{TEntry}"/> instance.
+        /// </summary>
+        public Level[] Levels { get; }
+
+        /// <summary>
+        /// Gets or sets the default fill value of newly created leaf pages.
+        /// </summary>
+        public TEntry Fill { get; set; }
+
+        /// <summary>
+        /// Gets the base address of the <see cref="EntryTable{TEntry}"/>.
+        /// </summary>
+        /// <exception cref="ObjectDisposedException"><see cref="EntryTable{TEntry}"/> instance was disposed</exception>
+        public IntPtr Base
+        {
+            get
+            {
+                ObjectDisposedException.ThrowIf(_disposed, this);
+
+                lock (_pages)
+                {
+                    return (IntPtr)GetRootPage();
+                }
+            }
+        }
+
+        /// <summary>
+        /// Constructs a new instance of the <see cref="AddressTable{TEntry}"/> class with the specified list of
+        /// <see cref="Level"/>.
+        /// </summary>
+        /// <exception cref="ArgumentNullException"><paramref name="levels"/> is null</exception>
+        /// <exception cref="ArgumentException">Length of <paramref name="levels"/> is less than 2</exception>
+        public AddressTable(Level[] levels)
+        {
+            ArgumentNullException.ThrowIfNull(levels);
+
+            if (levels.Length < 2)
+            {
+                throw new ArgumentException("Table must be at least 2 levels deep.", nameof(levels));
+            }
+
+            _pages = new List<IntPtr>(capacity: 16);
+
+            Levels = levels;
+            Mask = 0;
+
+            foreach (var level in Levels)
+            {
+                Mask |= level.Mask;
+            }
+        }
+
+        /// <summary>
+        /// Determines if the specified <paramref name="address"/> is in the range of the
+        /// <see cref="AddressTable{TEntry}"/>.
+        /// </summary>
+        /// <param name="address">Guest address</param>
+        /// <returns><see langword="true"/> if is valid; otherwise <see langword="false"/></returns>
+        public bool IsValid(ulong address)
+        {
+            return (address & ~Mask) == 0;
+        }
+
+        /// <summary>
+        /// Gets a reference to the value at the specified guest <paramref name="address"/>.
+        /// </summary>
+        /// <param name="address">Guest address</param>
+        /// <returns>Reference to the value at the specified guest <paramref name="address"/></returns>
+        /// <exception cref="ObjectDisposedException"><see cref="EntryTable{TEntry}"/> instance was disposed</exception>
+        /// <exception cref="ArgumentException"><paramref name="address"/> is not mapped</exception>
+        public ref TEntry GetValue(ulong address)
+        {
+            ObjectDisposedException.ThrowIf(_disposed, this);
+
+            if (!IsValid(address))
+            {
+                throw new ArgumentException($"Address 0x{address:X} is not mapped onto the table.", nameof(address));
+            }
+
+            lock (_pages)
+            {
+                return ref GetPage(address)[Levels[^1].GetValue(address)];
+            }
+        }
+
+        /// <summary>
+        /// Gets the leaf page for the specified guest <paramref name="address"/>.
+        /// </summary>
+        /// <param name="address">Guest address</param>
+        /// <returns>Leaf page for the specified guest <paramref name="address"/></returns>
+        private TEntry* GetPage(ulong address)
+        {
+            TEntry** page = GetRootPage();
+
+            for (int i = 0; i < Levels.Length - 1; i++)
+            {
+                ref Level level = ref Levels[i];
+                ref TEntry* nextPage = ref page[level.GetValue(address)];
+
+                if (nextPage == null)
+                {
+                    ref Level nextLevel = ref Levels[i + 1];
+
+                    nextPage = i == Levels.Length - 2 ?
+                        (TEntry*)Allocate(1 << nextLevel.Length, Fill, leaf: true) :
+                        (TEntry*)Allocate(1 << nextLevel.Length, IntPtr.Zero, leaf: false);
+                }
+
+                page = (TEntry**)nextPage;
+            }
+
+            return (TEntry*)page;
+        }
+
+        /// <summary>
+        /// Lazily initialize and get the root page of the <see cref="AddressTable{TEntry}"/>.
+        /// </summary>
+        /// <returns>Root page of the <see cref="AddressTable{TEntry}"/></returns>
+        private TEntry** GetRootPage()
+        {
+            if (_table == null)
+            {
+                _table = (TEntry**)Allocate(1 << Levels[0].Length, fill: IntPtr.Zero, leaf: false);
+            }
+
+            return _table;
+        }
+
+        /// <summary>
+        /// Allocates a block of memory of the specified type and length.
+        /// </summary>
+        /// <typeparam name="T">Type of elements</typeparam>
+        /// <param name="length">Number of elements</param>
+        /// <param name="fill">Fill value</param>
+        /// <param name="leaf"><see langword="true"/> if leaf; otherwise <see langword="false"/></param>
+        /// <returns>Allocated block</returns>
+        private IntPtr Allocate<T>(int length, T fill, bool leaf) where T : unmanaged
+        {
+            var size = sizeof(T) * length;
+            var page = (IntPtr)NativeAllocator.Instance.Allocate((uint)size);
+            var span = new Span<T>((void*)page, length);
+
+            span.Fill(fill);
+
+            _pages.Add(page);
+
+            TranslatorEventSource.Log.AddressTableAllocated(size, leaf);
+
+            return page;
+        }
+
+        /// <summary>
+        /// Releases all resources used by the <see cref="AddressTable{TEntry}"/> instance.
+        /// </summary>
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        /// <summary>
+        /// Releases all unmanaged and optionally managed resources used by the <see cref="AddressTable{TEntry}"/>
+        /// instance.
+        /// </summary>
+        /// <param name="disposing"><see langword="true"/> to dispose managed resources also; otherwise just unmanaged resouces</param>
+        protected virtual void Dispose(bool disposing)
+        {
+            if (!_disposed)
+            {
+                foreach (var page in _pages)
+                {
+                    Marshal.FreeHGlobal(page);
+                }
+
+                _disposed = true;
+            }
+        }
+
+        /// <summary>
+        /// Frees resources used by the <see cref="AddressTable{TEntry}"/> instance.
+        /// </summary>
+        ~AddressTable()
+        {
+            Dispose(false);
+        }
+    }
+}
diff --git a/src/ARMeilleure/Common/Allocator.cs b/src/ARMeilleure/Common/Allocator.cs
new file mode 100644
index 00000000..247a8e8b
--- /dev/null
+++ b/src/ARMeilleure/Common/Allocator.cs
@@ -0,0 +1,24 @@
+using System;
+
+namespace ARMeilleure.Common
+{
+    unsafe abstract class Allocator : IDisposable
+    {
+        public T* Allocate<T>(ulong count = 1) where T : unmanaged
+        {
+            return (T*)Allocate(count * (uint)sizeof(T));
+        }
+
+        public abstract void* Allocate(ulong size);
+
+        public abstract void Free(void* block);
+
+        protected virtual void Dispose(bool disposing) { }
+
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+    }
+}
diff --git a/src/ARMeilleure/Common/ArenaAllocator.cs b/src/ARMeilleure/Common/ArenaAllocator.cs
new file mode 100644
index 00000000..bce6794a
--- /dev/null
+++ b/src/ARMeilleure/Common/ArenaAllocator.cs
@@ -0,0 +1,187 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+
+namespace ARMeilleure.Common
+{
+    unsafe sealed class ArenaAllocator : Allocator
+    {
+        private class PageInfo
+        {
+            public byte* Pointer;
+            public byte Unused;
+            public int UnusedCounter;
+        }
+
+        private int _lastReset;
+        private ulong _index;
+        private int _pageIndex;
+        private PageInfo _page;
+        private List<PageInfo> _pages;
+        private readonly ulong _pageSize;
+        private readonly uint _pageCount;
+        private readonly List<IntPtr> _extras;
+
+        public ArenaAllocator(uint pageSize, uint pageCount)
+        {
+            _lastReset = Environment.TickCount;
+
+            // Set _index to pageSize so that the first allocation goes through the slow path.
+            _index = pageSize;
+            _pageIndex = -1;
+
+            _page = null;
+            _pages = new List<PageInfo>();
+            _pageSize = pageSize;
+            _pageCount = pageCount;
+
+            _extras = new List<IntPtr>();
+        }
+
+        public Span<T> AllocateSpan<T>(ulong count) where T : unmanaged
+        {
+            return new Span<T>(Allocate<T>(count), (int)count);
+        }
+
+        public override void* Allocate(ulong size)
+        {
+            if (_index + size <= _pageSize)
+            {
+                byte* result = _page.Pointer + _index;
+
+                _index += size;
+
+                return result;
+            }
+
+            return AllocateSlow(size);
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private void* AllocateSlow(ulong size)
+        {
+            if (size > _pageSize)
+            {
+                void* extra = NativeAllocator.Instance.Allocate(size);
+
+                _extras.Add((IntPtr)extra);
+
+                return extra;
+            }
+
+            if (_index + size > _pageSize)
+            {
+                _index = 0;
+                _pageIndex++;
+            }
+
+            if (_pageIndex < _pages.Count)
+            {
+                _page = _pages[_pageIndex];
+                _page.Unused = 0;
+            }
+            else
+            {
+                _page = new PageInfo();
+                _page.Pointer = (byte*)NativeAllocator.Instance.Allocate(_pageSize);
+
+                _pages.Add(_page);
+            }
+
+            byte* result = _page.Pointer + _index;
+
+            _index += size;
+
+            return result;
+        }
+
+        public override void Free(void* block) { }
+
+        public void Reset()
+        {
+            _index = _pageSize;
+            _pageIndex = -1;
+            _page = null;
+
+            // Free excess pages that was allocated.
+            while (_pages.Count > _pageCount)
+            {
+                NativeAllocator.Instance.Free(_pages[_pages.Count - 1].Pointer);
+
+                _pages.RemoveAt(_pages.Count - 1);
+            }
+
+            // Free extra blocks that are not page-sized
+            foreach (IntPtr ptr in _extras)
+            {
+                NativeAllocator.Instance.Free((void*)ptr);
+            }
+
+            _extras.Clear();
+
+            // Free pooled pages that has not been used in a while. Remove pages at the back first, because we try to
+            // keep the pages at the front alive, since they're more likely to be hot and in the d-cache.
+            bool removing = true;
+
+            // If arena is used frequently, keep pages for longer. Otherwise keep pages for a shorter amount of time.
+            int now = Environment.TickCount;
+            int count = (now - _lastReset) switch {
+                >= 5000 => 0,
+                >= 2500 => 50,
+                >= 1000 => 100,
+                >= 10   => 1500,
+                _       => 5000
+            };
+
+            for (int i = _pages.Count - 1; i >= 0; i--)
+            {
+                PageInfo page = _pages[i];
+
+                if (page.Unused == 0)
+                {
+                    page.UnusedCounter = 0;
+                }
+
+                page.UnusedCounter += page.Unused;
+                page.Unused = 1;
+
+                // If page not used after `count` resets, remove it.
+                if (removing && page.UnusedCounter >= count)
+                {
+                    NativeAllocator.Instance.Free(page.Pointer);
+
+                    _pages.RemoveAt(i);
+                }
+                else
+                {
+                    removing = false;
+                }
+            }
+
+            _lastReset = now;
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            if (_pages != null)
+            {
+                foreach (PageInfo info in _pages)
+                {
+                    NativeAllocator.Instance.Free(info.Pointer);
+                }
+
+                foreach (IntPtr ptr in _extras)
+                {
+                    NativeAllocator.Instance.Free((void*)ptr);
+                }
+
+                _pages = null;
+            }
+        }
+
+        ~ArenaAllocator()
+        {
+            Dispose(false);
+        }
+    }
+}
diff --git a/src/ARMeilleure/Common/BitMap.cs b/src/ARMeilleure/Common/BitMap.cs
new file mode 100644
index 00000000..27ef031f
--- /dev/null
+++ b/src/ARMeilleure/Common/BitMap.cs
@@ -0,0 +1,222 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Numerics;
+using System.Runtime.CompilerServices;
+
+namespace ARMeilleure.Common
+{
+    unsafe class BitMap : IEnumerable<int>, IDisposable
+    {
+        private const int IntSize = 64;
+        private const int IntMask = IntSize - 1;
+
+        private int _count;
+        private long* _masks;
+        private readonly Allocator _allocator;
+
+        public BitMap(Allocator allocator)
+        {
+            _allocator = allocator;
+        }
+
+        public BitMap(Allocator allocator, int capacity) : this(allocator)
+        {
+            EnsureCapacity(capacity);
+        }
+
+        public bool Set(int bit)
+        {
+            EnsureCapacity(bit + 1);
+
+            int wordIndex = bit / IntSize;
+            int wordBit = bit & IntMask;
+
+            long wordMask = 1L << wordBit;
+
+            if ((_masks[wordIndex] & wordMask) != 0)
+            {
+                return false;
+            }
+
+            _masks[wordIndex] |= wordMask;
+
+            return true;
+        }
+
+        public void Clear(int bit)
+        {
+            EnsureCapacity(bit + 1);
+
+            int wordIndex = bit / IntSize;
+            int wordBit = bit & IntMask;
+
+            long wordMask = 1L << wordBit;
+
+            _masks[wordIndex] &= ~wordMask;
+        }
+
+        public bool IsSet(int bit)
+        {
+            EnsureCapacity(bit + 1);
+
+            int wordIndex = bit / IntSize;
+            int wordBit = bit & IntMask;
+
+            return (_masks[wordIndex] & (1L << wordBit)) != 0;
+        }
+
+        public int FindFirstUnset()
+        {
+            for (int index = 0; index < _count; index++)
+            {
+                long mask = _masks[index];
+
+                if (mask != -1L)
+                {
+                    return BitOperations.TrailingZeroCount(~mask) + index * IntSize;
+                }
+            }
+
+            return _count * IntSize;
+        }
+
+        public bool Set(BitMap map)
+        {
+            EnsureCapacity(map._count * IntSize);
+
+            bool modified = false;
+
+            for (int index = 0; index < _count; index++)
+            {
+                long newValue = _masks[index] | map._masks[index];
+
+                if (_masks[index] != newValue)
+                {
+                    _masks[index] = newValue;
+
+                    modified = true;
+                }
+            }
+
+            return modified;
+        }
+
+        public bool Clear(BitMap map)
+        {
+            EnsureCapacity(map._count * IntSize);
+
+            bool modified = false;
+
+            for (int index = 0; index < _count; index++)
+            {
+                long newValue = _masks[index] & ~map._masks[index];
+
+                if (_masks[index] != newValue)
+                {
+                    _masks[index] = newValue;
+
+                    modified = true;
+                }
+            }
+
+            return modified;
+        }
+
+        private void EnsureCapacity(int size)
+        {
+            int count = (size + IntMask) / IntSize;
+
+            if (count > _count)
+            {
+                var oldMask = _masks;
+                var oldSpan = new Span<long>(_masks, _count);
+
+                _masks = _allocator.Allocate<long>((uint)count);
+                _count = count;
+
+                var newSpan = new Span<long>(_masks, _count);
+
+                oldSpan.CopyTo(newSpan);
+                newSpan.Slice(oldSpan.Length).Clear();
+
+                _allocator.Free(oldMask);
+            }
+        }
+
+        public void Dispose()
+        {
+            if (_masks != null)
+            {
+                _allocator.Free(_masks);
+
+                _masks = null;
+            }
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return GetEnumerator();
+        }
+
+        IEnumerator<int> IEnumerable<int>.GetEnumerator()
+        {
+            return GetEnumerator();
+        }
+
+        public Enumerator GetEnumerator()
+        {
+            return new Enumerator(this);
+        }
+
+        public struct Enumerator : IEnumerator<int>
+        {
+            private long _index;
+            private long _mask;
+            private int _bit;
+            private readonly BitMap _map;
+
+            public int Current => (int)_index * IntSize + _bit;
+            object IEnumerator.Current => Current;
+
+            public Enumerator(BitMap map)
+            {
+                _index = -1;
+                _mask = 0;
+                _bit = 0;
+                _map = map;
+            }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            public bool MoveNext()
+            {
+                if (_mask != 0)
+                {
+                    _mask &= ~(1L << _bit);
+                }
+
+                // Manually hoist these loads, because RyuJIT does not.
+                long count = (uint)_map._count;
+                long* masks = _map._masks;
+
+                while (_mask == 0)
+                {
+                    if (++_index >= count)
+                    {
+                        return false;
+                    }
+
+                    _mask = masks[_index];
+                }
+
+                _bit = BitOperations.TrailingZeroCount(_mask);
+
+                return true;
+            }
+
+            public void Reset() { }
+
+            public void Dispose() { }
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/ARMeilleure/Common/BitUtils.cs b/src/ARMeilleure/Common/BitUtils.cs
new file mode 100644
index 00000000..e7697ff3
--- /dev/null
+++ b/src/ARMeilleure/Common/BitUtils.cs
@@ -0,0 +1,57 @@
+using System;
+using System.Numerics;
+
+namespace ARMeilleure.Common
+{
+    static class BitUtils
+    {
+        private static ReadOnlySpan<sbyte> HbsNibbleLut => new sbyte[] { -1, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3 };
+
+        public static long FillWithOnes(int bits)
+        {
+            return bits == 64 ? -1L : (1L << bits) - 1;
+        }
+
+        public static int HighestBitSet(int value)
+        {
+            return 31 - BitOperations.LeadingZeroCount((uint)value);
+        }
+
+        public static int HighestBitSetNibble(int value)
+        {
+            return HbsNibbleLut[value];
+        }
+
+        public static long Replicate(long bits, int size)
+        {
+            long output = 0;
+
+            for (int bit = 0; bit < 64; bit += size)
+            {
+                output |= bits << bit;
+            }
+
+            return output;
+        }
+
+        public static int RotateRight(int bits, int shift, int size)
+        {
+            return (int)RotateRight((uint)bits, shift, size);
+        }
+
+        public static uint RotateRight(uint bits, int shift, int size)
+        {
+            return (bits >> shift) | (bits << (size - shift));
+        }
+
+        public static long RotateRight(long bits, int shift, int size)
+        {
+            return (long)RotateRight((ulong)bits, shift, size);
+        }
+
+        public static ulong RotateRight(ulong bits, int shift, int size)
+        {
+            return (bits >> shift) | (bits << (size - shift));
+        }
+    }
+}
diff --git a/src/ARMeilleure/Common/Counter.cs b/src/ARMeilleure/Common/Counter.cs
new file mode 100644
index 00000000..d7210d15
--- /dev/null
+++ b/src/ARMeilleure/Common/Counter.cs
@@ -0,0 +1,98 @@
+using System;
+
+namespace ARMeilleure.Common
+{
+    /// <summary>
+    /// Represents a numeric counter which can be used for instrumentation of compiled code.
+    /// </summary>
+    /// <typeparam name="T">Type of the counter</typeparam>
+    class Counter<T> : IDisposable where T : unmanaged
+    {
+        private bool _disposed;
+        /// <summary>
+        /// Index in the <see cref="EntryTable{T}"/>
+        /// </summary>
+        private readonly int _index;
+        private readonly EntryTable<T> _countTable;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Counter{T}"/> class from the specified
+        /// <see cref="EntryTable{T}"/> instance and index.
+        /// </summary>
+        /// <param name="countTable"><see cref="EntryTable{T}"/> instance</param>
+        /// <exception cref="ArgumentNullException"><paramref name="countTable"/> is <see langword="null"/></exception>
+        /// <exception cref="ArgumentException"><typeparamref name="T"/> is unsupported</exception>
+        public Counter(EntryTable<T> countTable)
+        {
+            if (typeof(T) != typeof(byte) && typeof(T) != typeof(sbyte) &&
+                typeof(T) != typeof(short) && typeof(T) != typeof(ushort) &&
+                typeof(T) != typeof(int) && typeof(T) != typeof(uint) &&
+                typeof(T) != typeof(long) && typeof(T) != typeof(ulong) &&
+                typeof(T) != typeof(nint) && typeof(T) != typeof(nuint) &&
+                typeof(T) != typeof(float) && typeof(T) != typeof(double))
+            {
+                throw new ArgumentException("Counter does not support the specified type.");
+            }
+
+            _countTable = countTable ?? throw new ArgumentNullException(nameof(countTable));
+            _index = countTable.Allocate();
+        }
+
+        /// <summary>
+        /// Gets a reference to the value of the counter.
+        /// </summary>
+        /// <exception cref="ObjectDisposedException"><see cref="Counter{T}"/> instance was disposed</exception>
+        /// <remarks>
+        /// This can refer to freed memory if the owning <see cref="EntryTable{TEntry}"/> is disposed.
+        /// </remarks>
+        public ref T Value
+        {
+            get
+            {
+                ObjectDisposedException.ThrowIf(_disposed, this);
+
+                return ref _countTable.GetValue(_index);
+            }
+        }
+
+        /// <summary>
+        /// Releases all resources used by the <see cref="Counter{T}"/> instance.
+        /// </summary>
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        /// <summary>
+        /// Releases all unmanaged and optionally managed resources used by the <see cref="Counter{T}"/> instance.
+        /// </summary>
+        /// <param name="disposing"><see langword="true"/> to dispose managed resources also; otherwise just unmanaged resources</param>
+        protected virtual void Dispose(bool disposing)
+        {
+            if (!_disposed)
+            {
+                try
+                {
+                    // The index into the EntryTable is essentially an unmanaged resource since we allocate and free the
+                    // resource ourselves.
+                    _countTable.Free(_index);
+                }
+                catch (ObjectDisposedException)
+                {
+                    // Can happen because _countTable may be disposed before the Counter instance.
+                }
+
+                _disposed = true;
+            }
+        }
+
+        /// <summary>
+        /// Frees resources used by the <see cref="Counter{T}"/> instance.
+        /// </summary>
+        ~Counter()
+        {
+            Dispose(false);
+        }
+    }
+}
diff --git a/src/ARMeilleure/Common/EntryTable.cs b/src/ARMeilleure/Common/EntryTable.cs
new file mode 100644
index 00000000..6f205797
--- /dev/null
+++ b/src/ARMeilleure/Common/EntryTable.cs
@@ -0,0 +1,188 @@
+using System;
+using System.Collections.Generic;
+using System.Numerics;
+
+namespace ARMeilleure.Common
+{
+    /// <summary>
+    /// Represents an expandable table of the type <typeparamref name="TEntry"/>, whose entries will remain at the same
+    /// address through out the table's lifetime.
+    /// </summary>
+    /// <typeparam name="TEntry">Type of the entry in the table</typeparam>
+    class EntryTable<TEntry> : IDisposable where TEntry : unmanaged
+    {
+        private bool _disposed;
+        private int _freeHint;
+        private readonly int _pageCapacity; // Number of entries per page.
+        private readonly int _pageLogCapacity;
+        private readonly Dictionary<int, IntPtr> _pages;
+        private readonly BitMap _allocated;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="EntryTable{TEntry}"/> class with the desired page size in
+        /// bytes.
+        /// </summary>
+        /// <param name="pageSize">Desired page size in bytes</param>
+        /// <exception cref="ArgumentOutOfRangeException"><paramref name="pageSize"/> is less than 0</exception>
+        /// <exception cref="ArgumentException"><typeparamref name="TEntry"/>'s size is zero</exception>
+        /// <remarks>
+        /// The actual page size may be smaller or larger depending on the size of <typeparamref name="TEntry"/>.
+        /// </remarks>
+        public unsafe EntryTable(int pageSize = 4096)
+        {
+            if (pageSize < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(pageSize), "Page size cannot be negative.");
+            }
+
+            if (sizeof(TEntry) == 0)
+            {
+                throw new ArgumentException("Size of TEntry cannot be zero.");
+            }
+
+            _allocated = new BitMap(NativeAllocator.Instance);
+            _pages = new Dictionary<int, IntPtr>();
+            _pageLogCapacity = BitOperations.Log2((uint)(pageSize / sizeof(TEntry)));
+            _pageCapacity = 1 << _pageLogCapacity;
+        }
+
+        /// <summary>
+        /// Allocates an entry in the <see cref="EntryTable{TEntry}"/>.
+        /// </summary>
+        /// <returns>Index of entry allocated in the table</returns>
+        /// <exception cref="ObjectDisposedException"><see cref="EntryTable{TEntry}"/> instance was disposed</exception>
+        public int Allocate()
+        {
+            ObjectDisposedException.ThrowIf(_disposed, this);
+
+            lock (_allocated)
+            {
+                if (_allocated.IsSet(_freeHint))
+                {
+                    _freeHint = _allocated.FindFirstUnset();
+                }
+
+                int index = _freeHint++;
+                var page = GetPage(index);
+
+                _allocated.Set(index);
+
+                GetValue(page, index) = default;
+
+                return index;
+            }
+        }
+
+        /// <summary>
+        /// Frees the entry at the specified <paramref name="index"/>.
+        /// </summary>
+        /// <param name="index">Index of entry to free</param>
+        /// <exception cref="ObjectDisposedException"><see cref="EntryTable{TEntry}"/> instance was disposed</exception>
+        public void Free(int index)
+        {
+            ObjectDisposedException.ThrowIf(_disposed, this);
+
+            lock (_allocated)
+            {
+                if (_allocated.IsSet(index))
+                {
+                    _allocated.Clear(index);
+
+                    _freeHint = index;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets a reference to the entry at the specified allocated <paramref name="index"/>.
+        /// </summary>
+        /// <param name="index">Index of the entry</param>
+        /// <returns>Reference to the entry at the specified <paramref name="index"/></returns>
+        /// <exception cref="ObjectDisposedException"><see cref="EntryTable{TEntry}"/> instance was disposed</exception>
+        /// <exception cref="ArgumentException">Entry at <paramref name="index"/> is not allocated</exception>
+        public ref TEntry GetValue(int index)
+        {
+            ObjectDisposedException.ThrowIf(_disposed, this);
+
+            lock (_allocated)
+            {
+                if (!_allocated.IsSet(index))
+                {
+                    throw new ArgumentException("Entry at the specified index was not allocated", nameof(index));
+                }
+
+                var page = GetPage(index);
+
+                return ref GetValue(page, index);
+            }
+        }
+
+        /// <summary>
+        /// Gets a reference to the entry at using the specified <paramref name="index"/> from the specified
+        /// <paramref name="page"/>.
+        /// </summary>
+        /// <param name="page">Page to use</param>
+        /// <param name="index">Index to use</param>
+        /// <returns>Reference to the entry</returns>
+        private ref TEntry GetValue(Span<TEntry> page, int index)
+        {
+            return ref page[index & (_pageCapacity - 1)];
+        }
+
+        /// <summary>
+        /// Gets the page for the specified <see cref="index"/>.
+        /// </summary>
+        /// <param name="index">Index to use</param>
+        /// <returns>Page for the specified <see cref="index"/></returns>
+        private unsafe Span<TEntry> GetPage(int index)
+        {
+            var pageIndex = (int)((uint)(index & ~(_pageCapacity - 1)) >> _pageLogCapacity);
+
+            if (!_pages.TryGetValue(pageIndex, out IntPtr page))
+            {
+                page = (IntPtr)NativeAllocator.Instance.Allocate((uint)sizeof(TEntry) * (uint)_pageCapacity);
+
+                _pages.Add(pageIndex, page);
+            }
+
+            return new Span<TEntry>((void*)page, _pageCapacity);
+        }
+
+        /// <summary>
+        /// Releases all resources used by the <see cref="EntryTable{TEntry}"/> instance.
+        /// </summary>
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        /// <summary>
+        /// Releases all unmanaged and optionally managed resources used by the <see cref="EntryTable{TEntry}"/>
+        /// instance.
+        /// </summary>
+        /// <param name="disposing"><see langword="true"/> to dispose managed resources also; otherwise just unmanaged resouces</param>
+        protected unsafe virtual void Dispose(bool disposing)
+        {
+            if (!_disposed)
+            {
+                _allocated.Dispose();
+
+                foreach (var page in _pages.Values)
+                {
+                    NativeAllocator.Instance.Free((void*)page);
+                }
+
+                _disposed = true;
+            }
+        }
+
+        /// <summary>
+        /// Frees resources used by the <see cref="EntryTable{TEntry}"/> instance.
+        /// </summary>
+        ~EntryTable()
+        {
+            Dispose(false);
+        }
+    }
+}
diff --git a/src/ARMeilleure/Common/EnumUtils.cs b/src/ARMeilleure/Common/EnumUtils.cs
new file mode 100644
index 00000000..2a4aa645
--- /dev/null
+++ b/src/ARMeilleure/Common/EnumUtils.cs
@@ -0,0 +1,12 @@
+using System;
+
+namespace ARMeilleure.Common
+{
+    static class EnumUtils
+    {
+        public static int GetCount(Type enumType)
+        {
+            return Enum.GetNames(enumType).Length;
+        }
+    }
+}
diff --git a/src/ARMeilleure/Common/NativeAllocator.cs b/src/ARMeilleure/Common/NativeAllocator.cs
new file mode 100644
index 00000000..71c04a9b
--- /dev/null
+++ b/src/ARMeilleure/Common/NativeAllocator.cs
@@ -0,0 +1,27 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace ARMeilleure.Common
+{
+    unsafe sealed class NativeAllocator : Allocator
+    {
+        public static NativeAllocator Instance { get; } = new();
+
+        public override void* Allocate(ulong size)
+        {
+            void* result = (void*)Marshal.AllocHGlobal((IntPtr)size);
+
+            if (result == null)
+            {
+                throw new OutOfMemoryException();
+            }
+
+            return result;
+        }
+
+        public override void Free(void* block)
+        {
+            Marshal.FreeHGlobal((IntPtr)block);
+        }
+    }
+}