[mono] Implement synch block fast paths in managed

src/mono/System.Private.CoreLib/System.Private.CoreLib.csproj

@@ -266,6 +266,7 @@
       <Compile Include="$(BclSourcesRoot)\System\Security\DynamicSecurityMethodAttribute.cs" />
       <Compile Include="$(BclSourcesRoot)\System\Threading\Interlocked.Mono.cs" />
       <Compile Include="$(BclSourcesRoot)\System\Threading\Monitor.Mono.cs" />
+      <Compile Include="$(BclSourcesRoot)\System\Threading\ObjectHeader.Mono.cs" />
       <Compile Include="$(BclSourcesRoot)\System\Threading\Thread.Mono.cs" />
       <Compile Include="$(BclSourcesRoot)\System\Threading\ThreadPool.Mono.cs" />
   </ItemGroup>

src/mono/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.Mono.cs

@@ -39,8 +39,12 @@ public static int OffsetToStringData
         [MethodImplAttribute(MethodImplOptions.InternalCall)]
         private static extern int InternalGetHashCode(object? o);
 
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static int GetHashCode(object? o)
         {
+            // NOTE: the interpreter does not run this code.  It intrinsifies the whole RuntimeHelpers.GetHashCode function
+            if (Threading.ObjectHeader.TryGetHashCode (o, out int hash))
+                return hash;
             return InternalGetHashCode(o);
         }
 
@@ -55,8 +59,12 @@ public static int GetHashCode(object? o)
         /// The advantage of this over <see cref="GetHashCode" /> is that it avoids assigning a hash
         /// code to the object if it does not already have one.
         /// </remarks>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         internal static int TryGetHashCode(object? o)
         {
+            // NOTE: the interpreter does not run this code.  It intrinsifies the whole RuntimeHelpers.TryGetHashCode function
+            if (Threading.ObjectHeader.TryGetHashCode (o, out int hash))
+                return hash;
             return InternalTryGetHashCode(o);
         }
 

src/mono/System.Private.CoreLib/src/System/Threading/Monitor.Mono.cs

@@ -23,7 +23,17 @@ public static void Enter(object obj, ref bool lockTaken)
         }
 
         [MethodImplAttribute(MethodImplOptions.InternalCall)]
-        public static extern void Exit(object obj);
+        private static extern void InternalExit(object obj);
+
+        public static void Exit(object obj)
+        {
+            if (obj == null)
+                ArgumentNullException.ThrowIfNull(obj);
+            if (ObjectHeader.TryExitChecked(obj))
+                return;
+
+            InternalExit(obj);
+        }
 
         public static bool TryEnter(object obj)
         {
@@ -43,6 +53,7 @@ public static void TryEnter(object obj, ref bool lockTaken)
         public static bool TryEnter(object obj, int millisecondsTimeout)
         {
             bool lockTaken = false;
+
             TryEnter(obj, millisecondsTimeout, ref lockTaken);
             return lockTaken;
         }
@@ -51,13 +62,14 @@ public static void TryEnter(object obj, int millisecondsTimeout, ref bool lockTa
         {
             if (lockTaken)
                 throw new ArgumentException(SR.Argument_MustBeFalse, nameof(lockTaken));
+
             ReliableEnterTimeout(obj, millisecondsTimeout, ref lockTaken);
         }
 
         public static bool IsEntered(object obj)
         {
             ArgumentNullException.ThrowIfNull(obj);
-            return IsEnteredNative(obj);
+            return ObjectHeader.IsEntered(obj);
         }
 
         [UnsupportedOSPlatform("browser")]
@@ -79,15 +91,12 @@ public static void PulseAll(object obj)
             ObjPulseAll(obj);
         }
 
-        [MethodImplAttribute(MethodImplOptions.InternalCall)]
-        private static extern bool Monitor_test_synchronised(object obj);
-
         [MethodImplAttribute(MethodImplOptions.InternalCall)]
         private static extern void Monitor_pulse(object obj);
 
         private static void ObjPulse(object obj)
         {
-            if (!Monitor_test_synchronised(obj))
+            if (!ObjectHeader.HasOwner(obj))
                 throw new SynchronizationLockException();
 
             Monitor_pulse(obj);
@@ -98,7 +107,7 @@ private static void ObjPulse(object obj)
 
         private static void ObjPulseAll(object obj)
         {
-            if (!Monitor_test_synchronised(obj))
+            if (!ObjectHeader.HasOwner(obj))
                 throw new SynchronizationLockException();
 
             Monitor_pulse_all(obj);
@@ -111,7 +120,7 @@ private static bool ObjWait(int millisecondsTimeout, object obj)
         {
             if (millisecondsTimeout < 0 && millisecondsTimeout != (int)Timeout.Infinite)
                 throw new ArgumentOutOfRangeException(nameof(millisecondsTimeout));
-            if (!Monitor_test_synchronised(obj))
+            if (!ObjectHeader.HasOwner(obj))
                 throw new SynchronizationLockException();
 
             return Monitor_wait(obj, millisecondsTimeout, true);
@@ -120,22 +129,22 @@ private static bool ObjWait(int millisecondsTimeout, object obj)
         [MethodImplAttribute(MethodImplOptions.InternalCall)]
         internal static extern void try_enter_with_atomic_var(object obj, int millisecondsTimeout, bool allowInterruption, ref bool lockTaken);
 
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private static void ReliableEnterTimeout(object obj, int timeout, ref bool lockTaken)
         {
-            ArgumentNullException.ThrowIfNull(obj);
+            if (obj == null)
+                ArgumentNullException.ThrowIfNull(obj);
 
             if (timeout < 0 && timeout != (int)Timeout.Infinite)
                 throw new ArgumentOutOfRangeException(nameof(timeout));
 
-            try_enter_with_atomic_var(obj, timeout, true, ref lockTaken);
-        }
+            // fast path
+            if (ObjectHeader.TryEnterFast(obj)) {
+                lockTaken = true;
+                return;
+            }
 
-        [MethodImplAttribute(MethodImplOptions.InternalCall)]
-        private static extern bool Monitor_test_owner(object obj);
-
-        private static bool IsEnteredNative(object obj)
-        {
-            return Monitor_test_owner(obj);
+            try_enter_with_atomic_var(obj, timeout, true, ref lockTaken);
         }
 
         public static extern long LockContentionCount