Inherit buffer tracking handles rather than recreating on resize (#2330)

This greatly speeds up games that constantly resize buffers, and removes stuttering on games that resize large buffers occasionally:

- Large improvement on Super Mario 3D All-Stars (#1663 needed for best performance)
- Improvement to Hyrule Warriors: AoC, and UE4 games. These games can still stutter due to texture creation/loading.
- Small improvement to other games, potential 1-frame stutters avoided.

`ForceSynchronizeMemory`, which was added with POWER, is no longer needed. Some tests have been added for the MultiRegionHandle.

2 files changed, 64 insertions, 5 deletions

diff --git a/Ryujinx.Memory/Tracking/MemoryTracking.cs b/Ryujinx.Memory/Tracking/MemoryTracking.cs
index 70951e8c..aafb418d 100644
--- a/Ryujinx.Memory/Tracking/MemoryTracking.cs
+++ b/Ryujinx.Memory/Tracking/MemoryTracking.cs
@@ -134,13 +134,14 @@ namespace Ryujinx.Memory.Tracking
         /// </summary>
         /// <param name="address">CPU virtual address of the region</param>
         /// <param name="size">Size of the region</param>
+        /// <param name="handles">Handles to inherit state from or reuse. When none are present, provide null</param>
         /// <param name="granularity">Desired granularity of write tracking</param>
         /// <returns>The memory tracking handle</returns>
-        public MultiRegionHandle BeginGranularTracking(ulong address, ulong size, ulong granularity)
+        public MultiRegionHandle BeginGranularTracking(ulong address, ulong size, IEnumerable<IRegionHandle> handles, ulong granularity)
         {
             (address, size) = PageAlign(address, size);
 
-            return new MultiRegionHandle(this, address, size, granularity);
+            return new MultiRegionHandle(this, address, size, handles, granularity);
         }
 
         /// <summary>
diff --git a/Ryujinx.Memory/Tracking/MultiRegionHandle.cs b/Ryujinx.Memory/Tracking/MultiRegionHandle.cs
index 1f09807a..638e7290 100644
--- a/Ryujinx.Memory/Tracking/MultiRegionHandle.cs
+++ b/Ryujinx.Memory/Tracking/MultiRegionHandle.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 
 namespace Ryujinx.Memory.Tracking
 {
@@ -18,16 +19,68 @@ namespace Ryujinx.Memory.Tracking
 
         public bool Dirty { get; private set; } = true;
 
-        internal MultiRegionHandle(MemoryTracking tracking, ulong address, ulong size, ulong granularity)
+        internal MultiRegionHandle(MemoryTracking tracking, ulong address, ulong size, IEnumerable<IRegionHandle> handles, ulong granularity)
         {
             _handles = new RegionHandle[size / granularity];
             Granularity = granularity;
 
-            for (int i = 0; i < _handles.Length; i++)
+            int i = 0;
+
+            if (handles != null)
+            {
+                // Inherit from the handles we were given. Any gaps must be filled with new handles,
+                // and old handles larger than our granularity must copy their state onto new granular handles and dispose.
+                // It is assumed that the provided handles do not overlap, in order, are on page boundaries,
+                // and don't extend past the requested range.
+
+                foreach (RegionHandle handle in handles)
+                {
+                    int startIndex = (int)((handle.Address - address) / granularity);
+
+                    // Fill any gap left before this handle.
+                    while (i < startIndex)
+                    {
+                        RegionHandle fillHandle = tracking.BeginTracking(address + (ulong)i * granularity, granularity);
+                        fillHandle.Parent = this;
+                        _handles[i++] = fillHandle;
+                    }
+
+                    if (handle.Size == granularity)
+                    {
+                        handle.Parent = this;
+                        _handles[i++] = handle;
+                    }
+                    else
+                    {
+                        int endIndex = (int)((handle.EndAddress - address) / granularity);
+
+                        while (i < endIndex)
+                        {
+                            RegionHandle splitHandle = tracking.BeginTracking(address + (ulong)i * granularity, granularity);
+                            splitHandle.Parent = this;
+
+                            splitHandle.Reprotect(handle.Dirty);
+
+                            RegionSignal signal = handle.PreAction;
+                            if (signal != null)
+                            {
+                                splitHandle.RegisterAction(signal);
+                            }
+
+                            _handles[i++] = splitHandle;
+                        }
+
+                        handle.Dispose();
+                    }
+                }
+            }
+
+            // Fill any remaining space with new handles.
+            while (i < _handles.Length)
             {
                 RegionHandle handle = tracking.BeginTracking(address + (ulong)i * granularity, granularity);
                 handle.Parent = this;
-                _handles[i] = handle;
+                _handles[i++] = handle;
             }
 
             Address = address;
@@ -48,6 +101,11 @@ namespace Ryujinx.Memory.Tracking
             }
         }
 
+        public IEnumerable<RegionHandle> GetHandles()
+        {
+            return _handles;
+        }
+
         public void SignalWrite()
         {
             Dirty = true;