Move thin lock acquire/release in CoreCLR to managed code

src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.CoreCLR.cs

@@ -392,6 +392,11 @@ internal static unsafe void CopyConstruct<T>(T* dest, T* src) where T : unmanage
         internal static ref byte GetRawData(this object obj) =>
             ref Unsafe.As<RawData>(obj).Data;
 
+        [DebuggerHidden]
+        [DebuggerStepThrough]
+        internal static ref nint GetMethodTableRef(this object obj)
+            => ref Unsafe.Subtract(ref Unsafe.As<byte, nint>(ref GetRawData(obj)), 1);
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         internal static unsafe nuint GetRawObjectDataSize(object obj)
         {

src/coreclr/System.Private.CoreLib/src/System/Threading/ManagedThreadId.CoreCLR.cs

@@ -10,8 +10,16 @@ internal static class ManagedThreadId
         // This will be initialized by the runtime.
         [ThreadStatic]
         private static int t_currentManagedThreadId;
+
         internal static int CurrentManagedThreadIdUnchecked => t_currentManagedThreadId;
 
-        public static int Current => t_currentManagedThreadId;
+        public static int Current
+        {
+            get
+            {
+                Debug.Assert(t_currentManagedThreadId != 0, "The runtime should have initialized the thread id by now.");
+                return t_currentManagedThreadId;
+            }
+        }
     }
 }

src/coreclr/System.Private.CoreLib/src/System/Threading/Monitor.CoreCLR.cs

@@ -54,55 +54,31 @@ static Lock GetLockObjectFallback(object obj)
         #endregion
 
         #region Public Enter/Exit methods
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
         public static void Enter(object obj)
         {
-            ObjectHeader.HeaderLockResult result = ObjectHeader.TryAcquireThinLock(obj);
-            if (result == ObjectHeader.HeaderLockResult.Success)
-                return;
-
-            GetLockObject(obj).Enter();
+            ObjectHeader.AcquireThinLock(obj);
         }
 
+        [MethodImpl(MethodImplOptions.NoInlining)]
         public static bool TryEnter(object obj)
         {
-            ObjectHeader.HeaderLockResult result = ObjectHeader.TryAcquireThinLock(obj);
-            if (result == ObjectHeader.HeaderLockResult.Success)
-                return true;
-
-            if (result == ObjectHeader.HeaderLockResult.Failure)
-                return false;
-
-            return GetLockObject(obj).TryEnter();
+            return ObjectHeader.TryAcquireThinLock(obj);
         }
 
+        [MethodImpl(MethodImplOptions.NoInlining)]
         public static bool TryEnter(object obj, int millisecondsTimeout)
         {
             ArgumentOutOfRangeException.ThrowIfLessThan(millisecondsTimeout, -1);
-
-            ObjectHeader.HeaderLockResult result = ObjectHeader.TryAcquireThinLock(obj);
-            if (result == ObjectHeader.HeaderLockResult.Success)
-                return true;
-
-            return GetLockObject(obj).TryEnter(millisecondsTimeout);
+            return ObjectHeader.TryAcquireThinLock(obj, millisecondsTimeout);
         }
 
         [MethodImpl(MethodImplOptions.NoInlining)]
         public static void Exit(object obj)
         {
             ArgumentNullException.ThrowIfNull(obj);
-            ObjectHeader.HeaderLockResult result = ObjectHeader.Release(obj);
-
-            if (result == ObjectHeader.HeaderLockResult.Success)
-            {
-                return;
-            }
-
-            if (result == ObjectHeader.HeaderLockResult.Failure)
-            {
-                throw new SynchronizationLockException();
-            }
-
-            GetLockObject(obj).Exit();
+            ObjectHeader.Release(obj);
         }
 
         // Marked no-inlining to prevent recursive inlining of IsAcquired.
@@ -122,14 +98,7 @@ public static bool IsEntered(object obj)
 
         internal static void SynchronizedMethodEnter(object obj, ref bool lockTaken)
         {
-            ObjectHeader.HeaderLockResult result = ObjectHeader.TryAcquireThinLock(obj);
-            if (result == ObjectHeader.HeaderLockResult.Success)
-            {
-                lockTaken = true;
-                return;
-            }
-
-            GetLockObject(obj).Enter();
+            ObjectHeader.AcquireThinLock(obj);
             lockTaken = true;
         }
 
@@ -139,19 +108,7 @@ internal static void SynchronizedMethodExit(object obj, ref bool lockTaken)
             if (!lockTaken)
                 return;
 
-            ObjectHeader.HeaderLockResult result = ObjectHeader.Release(obj);
-
-            if (result == ObjectHeader.HeaderLockResult.Success)
-            {
-                return;
-            }
-
-            if (result == ObjectHeader.HeaderLockResult.Failure)
-            {
-                throw new SynchronizationLockException();
-            }
-
-            GetLockObject(obj).Exit();
+            ObjectHeader.Release(obj);
         }
     }
 }