cleanup old jit functions

ARMeilleure/Translation/JitCache.cs

@@ -17,7 +17,7 @@ namespace ARMeilleure.Translation
 
         private static IntPtr _basePointer;
 
-        private static int _offset;
+        private static JitCacheMemoryAllocator _allocator;
 
         private static List<JitCacheEntry> _cacheEntries;
 
@@ -27,14 +27,20 @@ namespace ARMeilleure.Translation
         {
             _basePointer = MemoryManagement.Allocate(CacheSize);
 
+            int startOffset = 0;
+
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
             {
                 JitUnwindWindows.InstallFunctionTableHandler(_basePointer, CacheSize);
 
                 // The first page is used for the table based SEH structs.
-                _offset = PageSize;
+                startOffset = PageSize;
             }
 
+            ReprotectRange(startOffset, CacheSize - startOffset);
+
+            _allocator = new JitCacheMemoryAllocator(CacheSize, startOffset);
+
             _cacheEntries = new List<JitCacheEntry>();
 
             _lock = new object();
@@ -52,8 +58,6 @@ namespace ARMeilleure.Translation
 
                 Marshal.Copy(code, 0, funcPtr, code.Length);
 
-                ReprotectRange(funcOffset, code.Length);
-
                 Add(new JitCacheEntry(funcOffset, code.Length, func.UnwindInfo));
 
                 return funcPtr;
@@ -76,16 +80,7 @@ namespace ARMeilleure.Translation
             {
                 IntPtr funcPtr = _basePointer + pageStart;
 
-                MemoryManagement.Reprotect(funcPtr, (ulong)fullPagesSize, MemoryProtection.ReadAndExecute);
+                MemoryManagement.Reprotect(funcPtr, (ulong)fullPagesSize, MemoryProtection.ReadWriteExecute);
-            }
-
-            int remaining = endOffs - pageEnd;
-
-            if (remaining != 0)
-            {
-                IntPtr funcPtr = _basePointer + pageEnd;
-
-                MemoryManagement.Reprotect(funcPtr, (ulong)remaining, MemoryProtection.ReadWriteExecute);
             }
         }
 
@@ -93,18 +88,28 @@ namespace ARMeilleure.Translation
         {
             codeSize = checked(codeSize + (CodeAlignment - 1)) & ~(CodeAlignment - 1);
 
-            int allocOffset = _offset;
+            int allocOffset = _allocator.Allocate(codeSize);
-
-            _offset += codeSize;
-
-            if ((ulong)(uint)_offset > CacheSize)
-            {
-                throw new OutOfMemoryException();
-            }
 
             return allocOffset;
         }
 
+        public static void Free(ulong address)
+        {
+            ulong offset = address - (ulong)_basePointer;
+
+            lock (_lock)
+            {
+                if (TryFind((int)offset, out JitCacheEntry entry))
+                {
+                    _cacheEntries.Remove(entry);
+
+                    int size = checked(entry.Size + (CodeAlignment - 1)) & ~(CodeAlignment - 1);
+
+                    _allocator.Free((int)entry.Offset, size);
+                }
+            }
+        }
+
         private static void Add(JitCacheEntry entry)
         {
             _cacheEntries.Add(entry);

ARMeilleure/Translation/JitCacheMemoryAllocator.cs

@@ -0,0 +1,108 @@
+using System;
+using System.Collections.Generic;
+
+namespace ARMeilleure.Translation
+{
+    class JitCacheMemoryAllocator
+    {
+        private int _size;
+
+        private LinkedList<(int Start, int End)> _memoryRanges;
+
+        public JitCacheMemoryAllocator(int size, int startPosition)
+        {
+            _size = size;
+
+            _memoryRanges = new LinkedList<(int start, int end)>();
+
+            _memoryRanges.AddFirst((startPosition, startPosition - 1));
+        }
+
+        public int Allocate(int size)
+        {
+            var node = _memoryRanges.First;
+
+            int offset;
+
+            while (true)
+            {
+                if (node.Value.End > (_size - 1) - size)
+                {
+                    throw new OutOfMemoryException();
+                }
+
+                if (node.Next == null)
+                {
+                    offset = node.Value.End + 1;
+
+                    node.Value = (node.Value.Start, node.Value.End + size);
+
+                    break;
+                }
+                else
+                {
+                    if (node.Next.Value.Start - node.Value.End <= 1)
+                    {
+                        node.Value = (node.Value.Start, node.Next.Value.End);
+
+                        _memoryRanges.Remove(node.Next);
+                    }
+
+                    if (node.Next.Value.Start - size > node.Value.End)
+                    {
+                        offset = node.Value.End + 1;
+
+                        if (node.Next.Value.Start - offset == size)
+                        {
+                            node.Value = (node.Value.Start, node.Next.Value.End);
+
+                            _memoryRanges.Remove(node.Next);
+
+                            break;
+                        }
+
+                        node.Value = (node.Value.Start, offset + size - 1);
+
+                        break;
+                    }
+
+                    node = node.Next;
+                }
+            }
+
+            return offset;
+        }
+
+        public void Free(int offset, int size)
+        {
+            if ((uint)offset >= (ulong)_size)
+            {
+                throw new ArgumentOutOfRangeException();
+            }
+
+            var node = _memoryRanges.First;
+
+            while (true)
+            {
+                if (node == null)
+                {
+                    throw new ArgumentOutOfRangeException();
+                }
+
+                if (offset <= node.Value.End)
+                {
+                    int newRangeStart = offset + size;
+
+                    _memoryRanges.AddAfter(node, (newRangeStart, node.Value.End));
+
+                    break;
+                }
+
+                node = node.Next;
+            }
+
+            node.Value = (node.Value.Start, offset - 1);
+        }
+
+    }
+}

ARMeilleure/Translation/TranslatedFunction.cs

@@ -1,17 +1,24 @@
+using System;
 using System.Threading;
+using System.Runtime.InteropServices;
 
 namespace ARMeilleure.Translation
 {
     class TranslatedFunction
     {
+        public ulong Pointer => (ulong)Marshal.GetFunctionPointerForDelegate(_func);
+
+        public int EntryCount;
+
         private const int MinCallsForRejit = 100;
 
         private GuestFunction _func;
 
+        private ulong _address;
         private bool  _rejit;
         private int   _callCount;
 
-        public TranslatedFunction(GuestFunction func, bool rejit)
+        public TranslatedFunction(GuestFunction func, ulong address, bool rejit)
         {
             _func  = func;
             _rejit = rejit;
@@ -19,7 +26,16 @@ namespace ARMeilleure.Translation
 
         public ulong Execute(State.ExecutionContext context)
         {
-            return _func(context.NativeContextPtr);
+            if (Interlocked.Increment(ref EntryCount) == 0)
+            {
+                return _address;
+            }
+
+            var nextAddress = _func(context.NativeContextPtr);
+
+            Interlocked.Decrement(ref EntryCount);
+
+            return nextAddress;
         }
 
         public bool ShouldRejit()

ARMeilleure/Translation/Translator.cs

@@ -6,6 +6,7 @@ using ARMeilleure.Memory;
 using ARMeilleure.State;
 using System;
 using System.Collections.Concurrent;
+using System.Collections.Generic;
 using System.Threading;
 
 using static ARMeilleure.IntermediateRepresentation.OperandHelper;
@@ -20,6 +21,8 @@ namespace ARMeilleure.Translation
 
         private ConcurrentDictionary<ulong, TranslatedFunction> _funcs;
 
+        private Queue<TranslatedFunction> _oldFunctions;
+
         private PriorityQueue<RejitRequest> _backgroundQueue;
 
         private AutoResetEvent _backgroundTranslatorEvent;
@@ -35,6 +38,8 @@ namespace ARMeilleure.Translation
             _backgroundQueue = new PriorityQueue<RejitRequest>(2);
 
             _backgroundTranslatorEvent = new AutoResetEvent(false);
+
+            _oldFunctions = new Queue<TranslatedFunction>();
         }
 
         private void TranslateQueuedSubs()
@@ -45,7 +50,23 @@ namespace ARMeilleure.Translation
                 {
                     TranslatedFunction func = Translate(request.Address, request.Mode, highCq: true);
 
-                    _funcs.AddOrUpdate(request.Address, func, (key, oldFunc) => func);
+                    _funcs.AddOrUpdate(request.Address, func, (key, oldFunc) =>
+                    {
+                        _oldFunctions.Enqueue(oldFunc);
+
+                        return func;
+                    });
+                }
+                else if (_oldFunctions.TryDequeue(out TranslatedFunction function))
+                {
+                    if (Interlocked.CompareExchange(ref function.EntryCount, -1, 0) != 0)
+                    {
+                        _oldFunctions.Enqueue(function);
+                    }
+                    else
+                    {
+                        JitCache.Free(function.Pointer);
+                    }
                 }
                 else
                 {
@@ -161,7 +182,7 @@ namespace ARMeilleure.Translation
 
             GuestFunction func = Compiler.Compile<GuestFunction>(cfg, argTypes, OperandType.I64, options);
 
-            return new TranslatedFunction(func, rejit: !highCq);
+            return new TranslatedFunction(func, address, rejit: !highCq);
         }
 
         private static ControlFlowGraph EmitAndGetCFG(ArmEmitterContext context, Block[] blocks)