GPU: Use a bitmap to track buffer modified flags. (#3775)

* Initial implementation

* Some improvements.

* Fix incorrect cast

* Performance improvement and improved correctness

* Add very fast path when all handles are checked.

* Slightly faster

* Add comment

* De-virtualize region handle

All region handles are now bitmap backed.

* Remove non-bitmap tracking

* Remove unused methods

* Add docs, remove unused methods

* Address Feedback

* Rename file

Ryujinx.Memory/Tracking/RegionHandle.cs

@@ -1,5 +1,4 @@
-using Ryujinx.Memory.Range;
-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading;
@@ -10,7 +9,7 @@ namespace Ryujinx.Memory.Tracking
     /// A tracking handle for a given region of virtual memory. The Dirty flag is updated whenever any changes are made,
     /// and an action can be performed when the region is read to or written from.
     /// </summary>
-    public class RegionHandle : IRegionHandle, IRange
+    public class RegionHandle : IRegionHandle
     {
         /// <summary>
         /// If more than this number of checks have been performed on a dirty flag since its last reprotect,
@@ -23,7 +22,20 @@ namespace Ryujinx.Memory.Tracking
         /// </summary>
         private static int VolatileThreshold = 5;
 
-        public bool Dirty { get; private set; }
+        public bool Dirty
+        {
+            get
+            {
+                return Bitmap.IsSet(DirtyBit);
+            }
+            protected set
+            {
+                Bitmap.Set(DirtyBit, value);
+            }
+        }
+
+        internal int SequenceNumber { get; set; }
+
         public bool Unmapped { get; private set; }
 
         public ulong Address { get; }
@@ -31,7 +43,6 @@ namespace Ryujinx.Memory.Tracking
         public ulong EndAddress { get; }
 
         internal IMultiRegionHandle Parent { get; set; }
-        internal int SequenceNumber { get; set; }
 
         private event Action _onDirty;
 
@@ -68,17 +79,26 @@ namespace Ryujinx.Memory.Tracking
 
         internal RegionSignal PreAction => _preAction;
 
+        internal ConcurrentBitmap Bitmap;
+        internal int DirtyBit;
+
         /// <summary>
-        /// Create a new region handle. The handle is registered with the given tracking object,
+        /// Create a new bitmap backed region handle. The handle is registered with the given tracking object,
         /// and will be notified of any changes to the specified region.
         /// </summary>
         /// <param name="tracking">Tracking object for the target memory block</param>
         /// <param name="address">Virtual address of the region to track</param>
         /// <param name="size">Size of the region to track</param>
+        /// <param name="bitmap">The bitmap the dirty flag for this handle is stored in</param>
+        /// <param name="bit">The bit index representing the dirty flag for this handle</param>
         /// <param name="mapped">True if the region handle starts mapped</param>
-        internal RegionHandle(MemoryTracking tracking, ulong address, ulong size, bool mapped = true)
+        internal RegionHandle(MemoryTracking tracking, ulong address, ulong size, ConcurrentBitmap bitmap, int bit, bool mapped = true)
         {
+            Bitmap = bitmap;
+            DirtyBit = bit;
+
             Dirty = mapped;
+
             Unmapped = !mapped;
             Address = address;
             Size = size;
@@ -92,6 +112,54 @@ namespace Ryujinx.Memory.Tracking
             }
         }
 
+        /// <summary>
+        /// Create a new region handle. The handle is registered with the given tracking object,
+        /// and will be notified of any changes to the specified region.
+        /// </summary>
+        /// <param name="tracking">Tracking object for the target memory block</param>
+        /// <param name="address">Virtual address of the region to track</param>
+        /// <param name="size">Size of the region to track</param>
+        /// <param name="mapped">True if the region handle starts mapped</param>
+        internal RegionHandle(MemoryTracking tracking, ulong address, ulong size, bool mapped = true)
+        {
+            Bitmap = new ConcurrentBitmap(1, mapped);
+
+            Unmapped = !mapped;
+            Address = address;
+            Size = size;
+            EndAddress = address + size;
+
+            _tracking = tracking;
+            _regions = tracking.GetVirtualRegionsForHandle(address, size);
+            foreach (var region in _regions)
+            {
+                region.Handles.Add(this);
+            }
+        }
+
+        /// <summary>
+        /// Replace the bitmap and bit index used to track dirty state.
+        /// </summary>
+        /// <remarks>
+        /// The tracking lock should be held when this is called, to ensure neither bitmap is modified.
+        /// </remarks>
+        /// <param name="bitmap">The bitmap the dirty flag for this handle is stored in</param>
+        /// <param name="bit">The bit index representing the dirty flag for this handle</param>
+        internal void ReplaceBitmap(ConcurrentBitmap bitmap, int bit)
+        {
+            // Assumes the tracking lock is held, so nothing else can signal right now.
+
+            var oldBitmap = Bitmap;
+            var oldBit = DirtyBit;
+
+            bitmap.Set(bit, Dirty);
+
+            Bitmap = bitmap;
+            DirtyBit = bit;
+
+            Dirty |= oldBitmap.IsSet(oldBit);
+        }
+
         /// <summary>
         /// Clear the volatile state of this handle.
         /// </summary>
@@ -108,7 +176,7 @@ namespace Ryujinx.Memory.Tracking
         public bool DirtyOrVolatile()
         {
             _checkCount++;
-            return Dirty || _volatile;
+            return _volatile || Dirty;
         }
 
         /// <summary>
@@ -195,6 +263,8 @@ namespace Ryujinx.Memory.Tracking
         /// </summary>
         public void ForceDirty()
         {
+            _checkCount++;
+
             Dirty = true;
         }