[Experimental] Add alternative way of resolving UCO function pointers for Marshal Methods

src/Mono.Android/Android.Runtime/JNIEnvInit.cs

@@ -33,6 +33,7 @@ internal struct JnienvInitializeArgs {
 			public bool            marshalMethodsEnabled;
 			public IntPtr          grefGCUserPeerable;
 			public uint            runtimeType;
+			public bool            managedMarshalMethodsLookupEnabled;
 		}
 #pragma warning restore 0649
 
@@ -122,9 +123,17 @@ internal static unsafe void Initialize (JnienvInitializeArgs* args)
 				}
 			}
 
+			if (args->managedMarshalMethodsLookupEnabled) {
+				delegate* unmanaged <int, int, int, IntPtr*, void> getFunctionPointer = &ManagedMarshalMethodsLookupTable.GetFunctionPointer;
+				xamarin_app_init (args->env, getFunctionPointer);
+			}
+
 			SetSynchronizationContext ();
 		}
 
+		[DllImport ("xamarin-app")]
+		static extern unsafe void xamarin_app_init (IntPtr env, delegate* unmanaged <int, int, int, IntPtr*, void> get_function_pointer);
+
 		// NOTE: prevents Android.App.Application static ctor from running
 		[MethodImpl (MethodImplOptions.NoInlining)]
 		static void SetSynchronizationContext () =>

src/Mono.Android/Java.Interop/ManagedMarshalMethodsLookupTable.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+using Android.Runtime;
+
+namespace Java.Interop;
+
+internal class ManagedMarshalMethodsLookupTable
+{
+	[UnmanagedCallersOnly]
+	internal static unsafe void GetFunctionPointer (int assemblyIndex, int classIndex, int methodIndex, IntPtr* target)
+	{
+		try {
+			IntPtr result = GetFunctionPointer (assemblyIndex, classIndex, methodIndex);
+			if (result == IntPtr.Zero || result == (IntPtr)(-1)) {
+				throw new InvalidOperationException ($"Failed to get function pointer for ({assemblyIndex}, {classIndex}, {methodIndex})");
+			}
+
+			*target = result;
+		} catch (Exception ex) {
+			AndroidEnvironment.UnhandledException (ex);
+			AndroidEnvironment.FailFast ("GetFunctionPointer failed: should not be reached");
+		}
+	}
+
+	static IntPtr GetFunctionPointer (int assemblyIndex, int classIndex, int methodIndex)
+	{
+		// ManagedMarshalMethodsLookupGenerator generates the body of this method is generated at app build time
+		throw new NotImplementedException ();
+	}
+}

src/Mono.Android/Mono.Android.csproj

@@ -313,6 +313,7 @@
     <Compile Include="Java.Interop\JavaLocationException.cs" />
     <Compile Include="Java.Interop\JavaObjectExtensions.cs" />
     <Compile Include="Java.Interop\JavaTypeParametersAttribute.cs" />
+    <Compile Include="Java.Interop\ManagedMarshalMethodsLookupTable.cs" />
     <Compile Include="Java.Interop\Runtime.cs" />
     <Compile Include="Java.Interop\TypeManager.cs" />
     <Compile Include="Java.Lang\Boolean.cs" />

src/Xamarin.Android.Build.Tasks/Tasks/GenerateJavaStubs.cs

@@ -54,6 +54,7 @@ public class GenerateJavaStubs : AndroidTask
 		public bool LinkingEnabled { get; set; }
 		public bool HaveMultipleRIDs { get; set; }
 		public bool EnableMarshalMethods { get; set; }
+		public bool EnableManagedMarshalMethodsLookup { get; set; }
 		public string ManifestTemplate { get; set; }
 		public string[] MergedManifestDocuments { get; set; }
 
@@ -244,8 +245,16 @@ void Run (bool useMarshalMethods)
 
 				foreach (var kvp in nativeCodeGenStates) {
 					NativeCodeGenState state = kvp.Value;
-					RewriteMarshalMethods (state, brokenExceptionTransitionsEnabled);
-					state.Classifier.AddSpecialCaseMethods ();
+					if (!EnableManagedMarshalMethodsLookup) {
+						RewriteMarshalMethods (state, brokenExceptionTransitionsEnabled);
+						state.Classifier.AddSpecialCaseMethods ();
+					} else {
+						// We need to run `AddSpecialCaseMethods` before `RewriteMarshalMethods` so that we can see the special case
+						// methods (such as TypeManager.n_Activate_mm) when generating the managed lookup tables.
+						state.Classifier.AddSpecialCaseMethods ();
+						state.ManagedMarshalMethodsLookupInfo = new ManagedMarshalMethodsLookupInfo (Log);
+						RewriteMarshalMethods (state, brokenExceptionTransitionsEnabled);
+					}
 
 					Log.LogDebugMessage ($"[{state.TargetArch}] Number of generated marshal methods: {state.Classifier.MarshalMethods.Count}");
 					if (state.Classifier.RejectedMethodCount > 0) {
@@ -460,7 +469,7 @@ void RewriteMarshalMethods (NativeCodeGenState state, bool brokenExceptionTransi
 				return;
 			}
 
-			var rewriter = new MarshalMethodsAssemblyRewriter (Log, state.TargetArch, state.Classifier, state.Resolver);
+			var rewriter = new MarshalMethodsAssemblyRewriter (Log, state.TargetArch, state.Classifier, state.Resolver, state.ManagedMarshalMethodsLookupInfo);
 			rewriter.Rewrite (brokenExceptionTransitionsEnabled);
 		}
 

src/Xamarin.Android.Build.Tasks/Tasks/GeneratePackageManagerJava.cs

@@ -62,6 +62,7 @@ public class GeneratePackageManagerJava : AndroidTask
 		public bool EnablePreloadAssembliesDefault { get; set; }
 
 		public bool EnableMarshalMethods { get; set; }
+		public bool EnableManagedMarshalMethodsLookup { get; set; }
 		public string RuntimeConfigBinFilePath { get; set; }
 		public string BoundExceptionType { get; set; }
 
@@ -339,6 +340,7 @@ void AddEnvironment ()
 				JniRemappingReplacementTypeCount = jniRemappingNativeCodeInfo == null ? 0 : jniRemappingNativeCodeInfo.ReplacementTypeCount,
 				JniRemappingReplacementMethodIndexEntryCount = jniRemappingNativeCodeInfo == null ? 0 : jniRemappingNativeCodeInfo.ReplacementMethodIndexEntryCount,
 				MarshalMethodsEnabled = EnableMarshalMethods,
+				ManagedMarshalMethodsLookupEnabled = EnableManagedMarshalMethodsLookup,
 				IgnoreSplitConfigs = ShouldIgnoreSplitConfigs (),
 			};
 			LLVMIR.LlvmIrModule appConfigModule = appConfigAsmGen.Construct ();
@@ -367,7 +369,8 @@ void AddEnvironment ()
 						Log,
 						assemblyCount,
 						uniqueAssemblyNames,
-						EnsureCodeGenState (targetArch)
+						EnsureCodeGenState (targetArch),
+						EnableManagedMarshalMethodsLookup
 					);
 				} else {
 					marshalMethodsAsmGen = new MarshalMethodsNativeAssemblyGenerator (

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BuildTest2.cs

@@ -469,7 +469,7 @@ public void XA1037PropertyDeprecatedWarning (string property, string value, bool
 			XamarinAndroidProject proj = isBindingProject ? new XamarinAndroidBindingProject () : new XamarinAndroidApplicationProject ();
 			proj.IsRelease = isRelease;
 			proj.SetProperty (property, value);
-			
+
 			using (ProjectBuilder b = isBindingProject ? CreateDllBuilder (Path.Combine ("temp", TestName)) : CreateApkBuilder (Path.Combine ("temp", TestName))) {
 				Assert.IsTrue (b.Build (proj), "Build should have succeeded.");
 				Assert.IsTrue (StringAssertEx.ContainsText (b.LastBuildOutput, $"The '{property}' MSBuild property is deprecated and will be removed"),

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Utilities/EnvironmentHelper.cs

@@ -65,9 +65,10 @@ public sealed class ApplicationConfig
 			public uint   jni_remapping_replacement_method_index_entry_count;
 			public uint   mono_components_mask;
 			public string android_package_name = String.Empty;
+			public bool   managed_marshal_methods_lookup_enabled;
 		}
 
-		const uint ApplicationConfigFieldCount = 26;
+		const uint ApplicationConfigFieldCount = 27;
 
 		const string ApplicationConfigSymbolName = "application_config";
 		const string AppEnvironmentVariablesSymbolName = "app_environment_variables";
@@ -335,6 +336,11 @@ static ApplicationConfig ReadApplicationConfig (EnvironmentFile envFile)
 						Assert.IsTrue (expectedPointerTypes.Contains (field [0]), $"Unexpected pointer field type in '{envFile.Path}:{item.LineNumber}': {field [0]}");
 						pointers.Add (field [1].Trim ());
 						break;
+
+					case 26: // managed_marshal_methods_lookup_enabled: bool / .byte
+						AssertFieldType (envFile.Path, parser.SourceFilePath, ".byte", field [0], item.LineNumber);
+						ret.managed_marshal_methods_lookup_enabled = ConvertFieldToBool ("managed_marshal_methods_lookup_enabled", envFile.Path, parser.SourceFilePath, item.LineNumber, field [1]);
+						break;
 				}
 				fieldCount++;
 			}

src/Xamarin.Android.Build.Tasks/Utilities/ApplicationConfig.cs

@@ -58,5 +58,6 @@ sealed class ApplicationConfig
 		[NativeAssembler (NumberFormat = LLVMIR.LlvmIrVariableNumberFormat.Hexadecimal)]
 		public uint   mono_components_mask;
 		public string android_package_name = String.Empty;
+		public bool   managed_marshal_methods_lookup_enabled;
 	}
 }

src/Xamarin.Android.Build.Tasks/Utilities/ApplicationConfigNativeAssemblyGenerator.cs

@@ -193,6 +193,7 @@ sealed class XamarinAndroidBundledAssembly
 		public PackageNamingPolicy PackageNamingPolicy { get; set; }
 		public List<ITaskItem> NativeLibraries { get; set; }
 		public bool MarshalMethodsEnabled { get; set; }
+		public bool ManagedMarshalMethodsLookupEnabled { get; set; }
 		public bool IgnoreSplitConfigs { get; set; }
 
 		public ApplicationConfigNativeAssemblyGenerator (IDictionary<string, string> environmentVariables, IDictionary<string, string> systemProperties, TaskLoggingHelper log)
@@ -237,6 +238,7 @@ protected override void Construct (LlvmIrModule module)
 				have_runtime_config_blob = HaveRuntimeConfigBlob,
 				have_assemblies_blob = HaveAssemblyStore,
 				marshal_methods_enabled = MarshalMethodsEnabled,
+				managed_marshal_methods_lookup_enabled = ManagedMarshalMethodsLookupEnabled,
 				ignore_split_configs = IgnoreSplitConfigs,
 				bound_stream_io_exception_type = (byte)BoundExceptionType,
 				package_naming_policy = (uint)PackageNamingPolicy,