Replace some uses of MethodDescCallSite with UnmanagedCallersOnly methods

src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/StaticsHelpers.cs

@@ -140,7 +140,7 @@ private static ref byte GetNonGCThreadStaticsByIndexSlow(int index)
         {
             ByteRef result = default;
             GetThreadStaticsByIndex(ByteRefOnStack.Create(ref result), index, false);
-            return ref result.Get();
+            return ref result.Value;
         }
 
         [DebuggerHidden]
@@ -149,7 +149,7 @@ private static ref byte GetGCThreadStaticsByIndexSlow(int index)
         {
             ByteRef result = default;
             GetThreadStaticsByIndex(ByteRefOnStack.Create(ref result), index, true);
-            return ref result.Get();
+            return ref result.Value;
         }
 
         [DebuggerHidden]
@@ -158,7 +158,7 @@ private static ref byte GetNonGCThreadStaticBaseSlow(MethodTable* mt)
         {
             ByteRef result = default;
             GetThreadStaticsByMethodTable(ByteRefOnStack.Create(ref result), mt, false);
-            return ref result.Get();
+            return ref result.Value;
         }
 
         [DebuggerHidden]
@@ -167,7 +167,7 @@ private static ref byte GetGCThreadStaticBaseSlow(MethodTable* mt)
         {
             ByteRef result = default;
             GetThreadStaticsByMethodTable(ByteRefOnStack.Create(ref result), mt, true);
-            return ref result.Get();
+            return ref result.Value;
         }
 
         [DebuggerHidden]

src/coreclr/System.Private.CoreLib/src/System/RuntimeHandles.cs

@@ -1553,9 +1553,9 @@ internal static ref byte GetFieldDataReference(object target, RuntimeFieldInfo f
         {
             ByteRef fieldDataRef = default;
             GetFieldDataReference(((RtFieldInfo)field).GetFieldDesc(), ObjectHandleOnStack.Create(ref target), ByteRefOnStack.Create(ref fieldDataRef));
-            Debug.Assert(!Unsafe.IsNullRef(ref fieldDataRef.Get()));
+            Debug.Assert(!Unsafe.IsNullRef(ref fieldDataRef.Value));
             GC.KeepAlive(field);
-            return ref fieldDataRef.Get();
+            return ref fieldDataRef.Value;
         }
 
         internal static ref byte GetFieldDataReference(ref byte target, RuntimeFieldInfo field)

src/coreclr/System.Private.CoreLib/src/System/StubHelpers.cs

@@ -831,6 +831,19 @@ internal static void ClearNative(IntPtr pMarshalState, in object pManagedHome, I
 
     internal static unsafe partial class MngdRefCustomMarshaler
     {
+        [UnmanagedCallersOnly]
+        internal static void ConvertContentsToNative(ICustomMarshaler* pMarshaler, object* pManagedHome, IntPtr* pNativeHome, Exception* pException)
+        {
+            try
+            {
+                ConvertContentsToNative(*pMarshaler, in *pManagedHome, pNativeHome);
+            }
+            catch (Exception ex)
+            {
+                *pException = ex;
+            }
+        }
+
         internal static void ConvertContentsToNative(ICustomMarshaler marshaler, in object pManagedHome, IntPtr* pNativeHome)
         {
             // COMPAT: We never pass null to MarshalManagedToNative.
@@ -843,6 +856,19 @@ internal static void ConvertContentsToNative(ICustomMarshaler marshaler, in obje
             *pNativeHome = marshaler.MarshalManagedToNative(pManagedHome);
         }
 
+        [UnmanagedCallersOnly]
+        internal static void ConvertContentsToManaged(ICustomMarshaler* pMarshaler, object* pManagedHome, IntPtr* pNativeHome, Exception* pException)
+        {
+            try
+            {
+                ConvertContentsToManaged(*pMarshaler, ref *pManagedHome, pNativeHome);
+            }
+            catch (Exception ex)
+            {
+                *pException = ex;
+            }
+        }
+
         internal static void ConvertContentsToManaged(ICustomMarshaler marshaler, ref object? pManagedHome, IntPtr* pNativeHome)
         {
             // COMPAT: We never pass null to MarshalNativeToManaged.
@@ -855,8 +881,20 @@ internal static void ConvertContentsToManaged(ICustomMarshaler marshaler, ref ob
             pManagedHome = marshaler.MarshalNativeToManaged(*pNativeHome);
         }
 
-#pragma warning disable IDE0060 // Remove unused parameter. These APIs need to match a the shape of a "managed" marshaler.
-        internal static void ClearNative(ICustomMarshaler marshaler, ref object pManagedHome, IntPtr* pNativeHome)
+        [UnmanagedCallersOnly]
+        internal static void ClearNative(ICustomMarshaler* pMarshaler, object* pManagedHome, IntPtr* pNativeHome, Exception* pException)
+        {
+            try
+            {
+                ClearNative(*pMarshaler, ref *pManagedHome, pNativeHome);
+            }
+            catch (Exception ex)
+            {
+                *pException = ex;
+            }
+        }
+
+        internal static void ClearNative(ICustomMarshaler marshaler, ref object _, IntPtr* pNativeHome)
         {
             // COMPAT: We never pass null to CleanUpNativeData.
             if (*pNativeHome == IntPtr.Zero)
@@ -874,7 +912,20 @@ internal static void ClearNative(ICustomMarshaler marshaler, ref object pManaged
             }
         }
 
-        internal static void ClearManaged(ICustomMarshaler marshaler, in object pManagedHome, IntPtr* pNativeHome)
+        [UnmanagedCallersOnly]
+        internal static void ClearManaged(ICustomMarshaler* pMarshaler, object* pManagedHome, IntPtr* pNativeHome, Exception* pException)
+        {
+            try
+            {
+                ClearManaged(*pMarshaler, in *pManagedHome, pNativeHome);
+            }
+            catch (Exception ex)
+            {
+                *pException = ex;
+            }
+        }
+
+        internal static void ClearManaged(ICustomMarshaler marshaler, in object pManagedHome, IntPtr* _)
         {
             // COMPAT: We never pass null to CleanUpManagedData.
             if (pManagedHome is null)
@@ -884,7 +935,6 @@ internal static void ClearManaged(ICustomMarshaler marshaler, in object pManaged
 
             marshaler.CleanUpManagedData(pManagedHome);
         }
-#pragma warning restore IDE0060
     }  // class MngdRefCustomMarshaler
 
     internal struct AsAnyMarshaler

src/coreclr/vm/callhelpers.h

@@ -660,6 +660,86 @@ enum DispatchCallSimpleFlags
 
 void CallDefaultConstructor(OBJECTREF ref);
 
+//
+// Helper types for calling managed methods marked with [UnmanagedCallersOnly]
+// from native code.
+//
+
+// Helper class for calling managed methods marked with [UnmanagedCallersOnly].
+// This provides a more efficient alternative to MethodDescCallSite for methods
+// using the reverse P/Invoke infrastructure.
+// This class assumes the target method signature has a trailing argument for
+// returning the exception (that is, Exception* in C#).
+//
+// Example usage:
+//   UnmanagedCallersOnlyCaller caller(BinderMethodID::MyMethod);
+//   ...
+//   caller.InvokeThrowing(arg1, arg2);
+//
+// The corresponding C# method would be declared as:
+//   [UnmanagedCallersOnly]
+//   public static void MyMethod(int arg1, object* arg2, Exception* pException);
+//
+class UnmanagedCallersOnlyCaller final
+{
+    MethodDesc* _pMD;
+public:
+    explicit UnmanagedCallersOnlyCaller(BinderMethodID id)
+        : _pMD{}
+    {
+        CONTRACTL
+        {
+            THROWS;
+            GC_TRIGGERS;
+            MODE_COOPERATIVE;
+        }
+        CONTRACTL_END;
+
+        _pMD = CoreLibBinder::GetMethod(id);
+        _ASSERTE(_pMD != NULL);
+        _ASSERTE(_pMD->HasUnmanagedCallersOnlyAttribute());
+    }
+
+    template<typename... Args>
+    void InvokeThrowing(Args... args)
+    {
+        CONTRACTL
+        {
+            THROWS;
+            GC_TRIGGERS;
+            MODE_COOPERATIVE;
+        }
+        CONTRACTL_END;
+
+        struct
+        {
+            OBJECTREF Exception;
+        } gc;
+        gc.Exception = NULL;
+        GCPROTECT_BEGIN(gc);
+
+        {
+            GCX_PREEMP();
+
+            PCODE methodEntry = _pMD->GetSingleCallableAddrOfCodeForUnmanagedCallersOnly();
+            _ASSERTE(methodEntry != (PCODE)NULL);
+
+            // Cast the function pointer to the appropriate type.
+            // Note that we append the exception handle argument.
+            auto fptr = reinterpret_cast<void(*)(Args..., OBJECTREF*)>(methodEntry);
+
+            // The last argument is the implied exception handle for any exceptions.
+            fptr(args..., &gc.Exception);
+        }
+
+        // If an exception was thrown, propagate it
+        if (gc.Exception != NULL)
+            COMPlusThrow(gc.Exception);
+
+        GCPROTECT_END();
+    }
+};
+
 #endif //!DACCESS_COMPILE
 
 #endif // __CALLHELPERS_H__

src/coreclr/vm/corelib.h

@@ -97,7 +97,7 @@ DEFINE_FIELD(ACCESS_VIOLATION_EXCEPTION, TARGET,            _target)
 DEFINE_FIELD(ACCESS_VIOLATION_EXCEPTION, ACCESSTYPE,        _accessType)
 
 DEFINE_CLASS(APPCONTEXT,            System,                 AppContext)
-DEFINE_METHOD(APPCONTEXT,   SETUP,              Setup,          SM_PtrPtrChar_PtrPtrChar_Int_RetVoid)
+DEFINE_METHOD(APPCONTEXT,   SETUP,              Setup,          SM_PtrPtrChar_PtrPtrChar_Int_PtrException_RetVoid)
 DEFINE_METHOD(APPCONTEXT,   ON_PROCESS_EXIT,    OnProcessExit,  SM_RetVoid)
 DEFINE_METHOD(APPCONTEXT,   ON_UNHANDLED_EXCEPTION,     OnUnhandledException,  SM_Obj_RetVoid)
 DEFINE_FIELD(APPCONTEXT, FIRST_CHANCE_EXCEPTION,        FirstChanceException)
@@ -1187,6 +1187,10 @@ DEFINE_METHOD(MNGD_REF_CUSTOM_MARSHALER, CONVERT_CONTENTS_TO_NATIVE,  ConvertCon
 DEFINE_METHOD(MNGD_REF_CUSTOM_MARSHALER, CONVERT_CONTENTS_TO_MANAGED, ConvertContentsToManaged,   SM_ICustomMarshaler_RefObj_PtrIntPtr_RetVoid)
 DEFINE_METHOD(MNGD_REF_CUSTOM_MARSHALER, CLEAR_NATIVE,                ClearNative,                SM_ICustomMarshaler_RefObj_PtrIntPtr_RetVoid)
 DEFINE_METHOD(MNGD_REF_CUSTOM_MARSHALER, CLEAR_MANAGED,               ClearManaged,               SM_ICustomMarshaler_RefObj_PtrIntPtr_RetVoid)
+DEFINE_METHOD(MNGD_REF_CUSTOM_MARSHALER, CONVERT_CONTENTS_TO_NATIVE_UCO,  ConvertContentsToNative,    SM_PtrICustomMarshaler_PtrObj_PtrIntPtr_PtrException_RetVoid)
+DEFINE_METHOD(MNGD_REF_CUSTOM_MARSHALER, CONVERT_CONTENTS_TO_MANAGED_UCO, ConvertContentsToManaged,   SM_PtrICustomMarshaler_PtrObj_PtrIntPtr_PtrException_RetVoid)
+DEFINE_METHOD(MNGD_REF_CUSTOM_MARSHALER, CLEAR_NATIVE_UCO,                ClearNative,                SM_PtrICustomMarshaler_PtrObj_PtrIntPtr_PtrException_RetVoid)
+DEFINE_METHOD(MNGD_REF_CUSTOM_MARSHALER, CLEAR_MANAGED_UCO,               ClearManaged,               SM_PtrICustomMarshaler_PtrObj_PtrIntPtr_PtrException_RetVoid)
 
 DEFINE_CLASS(ASANY_MARSHALER,            StubHelpers,                 AsAnyMarshaler)
 DEFINE_METHOD(ASANY_MARSHALER,           CTOR,                        .ctor,                      IM_IntPtr_RetVoid)

src/coreclr/vm/corhost.cpp

@@ -571,14 +571,8 @@ HRESULT CorHost2::CreateAppDomainWithManager(
     {
         GCX_COOP();
 
-        MethodDescCallSite setup(METHOD__APPCONTEXT__SETUP);
-
-        ARG_SLOT args[3];
-        args[0] = PtrToArgSlot(pPropertyNames);
-        args[1] = PtrToArgSlot(pPropertyValues);
-        args[2] = PtrToArgSlot(nProperties);
-
-        setup.Call(args);
+        UnmanagedCallersOnlyCaller setup(METHOD__APPCONTEXT__SETUP);
+        setup.InvokeThrowing(pPropertyNames, pPropertyValues, nProperties);
     }
 
     LPCWSTR pwzNativeDllSearchDirectories = NULL;