Initial conditional rendering support (#1012)

* Initial conditional rendering support

* Properly reset state

* Support conditional modes and skeleton a counter cache for future host conditional rendering

* Address PR feedback

Ryujinx.Graphics.Gpu/Memory/CounterCache.cs

@@ -0,0 +1,140 @@
+using System.Collections.Generic;
+
+namespace Ryujinx.Graphics.Gpu.Memory
+{
+    /// <summary>
+    /// Represents the GPU counter cache.
+    /// </summary>
+    class CounterCache
+    {
+        private struct CounterEntry
+        {
+            public ulong Address { get; }
+
+            public CounterEntry(ulong address)
+            {
+                Address = address;
+            }
+        }
+
+        private readonly List<CounterEntry> _items;
+
+        /// <summary>
+        /// Creates a new instance of the GPU counter cache.
+        /// </summary>
+        public CounterCache()
+        {
+            _items = new List<CounterEntry>();
+        }
+
+        /// <summary>
+        /// Adds a new counter to the counter cache, or updates a existing one.
+        /// </summary>
+        /// <param name="gpuVa">GPU virtual address where the counter will be written in memory</param>
+        public void AddOrUpdate(ulong gpuVa)
+        {
+            int index = BinarySearch(gpuVa);
+
+            CounterEntry entry = new CounterEntry(gpuVa);
+
+            if (index < 0)
+            {
+                _items.Insert(~index, entry);
+            }
+            else
+            {
+                _items[index] = entry;
+            }
+        }
+
+        /// <summary>
+        /// Handles removal of counters written to a memory region being unmapped.
+        /// </summary>
+        /// <param name="sender">Sender object</param>
+        /// <param name="e">Event arguments</param>
+        public void MemoryUnmappedHandler(object sender, UnmapEventArgs e) => RemoveRange(e.Address, e.Size);
+
+        private void RemoveRange(ulong gpuVa, ulong size)
+        {
+            int index = BinarySearch(gpuVa + size - 1);
+
+            if (index < 0)
+            {
+                index = ~index;
+            }
+
+            if (index >= _items.Count || !InRange(gpuVa, size, _items[index].Address))
+            {
+                return;
+            }
+
+            int count = 1;
+
+            while (index > 0 && InRange(gpuVa, size, _items[index - 1].Address))
+            {
+                index--;
+                count++;
+            }
+
+            _items.RemoveRange(index, count);
+        }
+
+        /// <summary>
+        /// Checks whenever an address falls inside a given range.
+        /// </summary>
+        /// <param name="startVa">Range start address</param>
+        /// <param name="size">Range size</param>
+        /// <param name="gpuVa">Address being checked</param>
+        /// <returns>True if the address falls inside the range, false otherwise</returns>
+        private static bool InRange(ulong startVa, ulong size, ulong gpuVa)
+        {
+            return gpuVa >= startVa && gpuVa < startVa + size;
+        }
+
+        /// <summary>
+        /// Check if any counter value was written to the specified GPU virtual memory address.
+        /// </summary>
+        /// <param name="gpuVa">GPU virtual address</param>
+        /// <returns>True if any counter value was written on the specified address, false otherwise</returns>
+        public bool Contains(ulong gpuVa)
+        {
+            return BinarySearch(gpuVa) >= 0;
+        }
+
+        /// <summary>
+        /// Performs binary search of an address on the list.
+        /// </summary>
+        /// <param name="address">Address to search</param>
+        /// <returns>Index of the item, or complement of the index of the nearest item with lower value</returns>
+        private int BinarySearch(ulong address)
+        {
+            int left = 0;
+            int right = _items.Count - 1;
+
+            while (left <= right)
+            {
+                int range = right - left;
+
+                int middle = left + (range >> 1);
+
+               CounterEntry item = _items[middle];
+
+                if (item.Address == address)
+                {
+                    return middle;
+                }
+
+                if (address < item.Address)
+                {
+                    right = middle - 1;
+                }
+                else
+                {
+                    left = middle + 1;
+                }
+            }
+
+            return ~left;
+        }
+    }
+}