[Xamarin.Android.Build.Tasks, monodroid] LLVM Marshal Methods Infra (#7004)

Context: https://github.com/xamarin/xamarin-android/wiki/Blueprint#java-type-registration

Introduce low-level "plumbing" for future JNI marshal method work.

A JNI marshal method is a [JNI-callable][0] function pointer provided
to [`JNIEnv::RegisterNatives()`][1].  Currently, JNI marshal methods
are provided via the interaction between `generator` and
`JNINativeWrapper.CreateDelegate()`:

  * `generator` emits the "actual" JNI-callable method.
  * `JNINativeWrapper.CreateDelegate()` uses System.Reflection.Emit
    to *wrap* the `generator`-emitted for exception marshaling.
    (Though see also 32cff43.)

JNI marshal methods are needed for all Java-to-C# transitions.

Consider the virtual `Activity.OnCreate()` method:

	partial class Activity {
	  static Delegate? cb_onCreate_Landroid_os_Bundle_;
	  static Delegate GetOnCreate_Landroid_os_Bundle_Handler ()
	  {
	    if (cb_onCreate_Landroid_os_Bundle_ == null)
	      cb_onCreate_Landroid_os_Bundle_ = JNINativeWrapper.CreateDelegate ((_JniMarshal_PPL_V) n_OnCreate_Landroid_os_Bundle_);
	    return cb_onCreate_Landroid_os_Bundle_;
	  }
	
	  static void n_OnCreate_Landroid_os_Bundle_ (IntPtr jnienv, IntPtr native__this, IntPtr native_savedInstanceState)
	  {
	    var __this = global::Java.Lang.Object.GetObject<Android.App.Activity> (jnienv, native__this, JniHandleOwnership.DoNotTransfer)!;
	    var savedInstanceState = global::Java.Lang.Object.GetObject<Android.OS.Bundle> (native_savedInstanceState, JniHandleOwnership.DoNotTransfer);
	    __this.OnCreate (savedInstanceState);
	  }
	
	  // Metadata.xml XPath method reference: path="/api/package[@name='android.app']/class[@name='Activity']/method[@name='onCreate' and count(parameter)=1 and parameter[1][@type='android.os.Bundle']]"
	  [Register ("onCreate", "(Landroid/os/Bundle;)V", "GetOnCreate_Landroid_os_Bundle_Handler")]
	  protected virtual unsafe void OnCreate (Android.OS.Bundle? savedInstanceState) => …
	}

`Activity.n_OnCreate_Landroid_os_Bundle_()` is the JNI marshal method,
responsible for marshaling parameters from JNI values into C# types,
forwarding the method invocation to `Activity.OnCreate()`, and (if
necessary) marshaling the return value back to JNI.

`Activity.GetOnCreate_Landroid_os_Bundle_Handler()` is part of the
type registration infrastructure, providing a `Delegate` instance to
`RegisterNativeMembers .RegisterNativeMembers()`, which is eventually
passed to `JNIEnv::RegisterNatives()`.

While this works, it's not incredibly performant: unless using one of
the optimized delegate types (32cff43 et. al),
System.Reflection.Emit is used to create a wrapper around the marshal
method, which is something we've wanted to avoid doing for years.

Thus, the idea: since we're *already* bundling a native toolchain and
using LLVM-IR to produce `libxamarin-app.so` (b21cbf9, 5271f3e),
what if we emitted [Java Native Method Names][2] and *skipped* all
the done as part of `Runtime.register()` and
`JNIEnv.RegisterJniNatives()`?

Given:

	class MyActivity : Activity {
	    protected override void OnCreate(Bundle? state) => …
	}

During the build, `libxamarin-app.so` would contain the function:

	JNIEXPORT void JNICALL
	Java_crc…_MyActivity_n_1onCreate (JNIEnv *env, jobject self, jobject state);

During App runtime, the `Runtime.register()` invocation present in
[Java Callable Wrappers][3] would either be omitted or would be a
no-op, and Android/JNI would instead resolve `MyActivity.n_onCreate()`
as `Java_crc…_MyActivity_n_1onCreate()`.

Many of the specifics are still being investigated, and this feature
will be spread across various areas.

We call this effort "LLVM Marshal Methods".

First, prepare the way.  Update `Xamarin.Android.Build.Tasks.dll`
and `src/monodroid` to introduce support for generating JNI marshal
methods into `libxamarin-app.so`.  Most of the added code is
*disabled and hidden* behind `#if ENABLE_MARSHAL_METHODS`.

~~ TODO ~~

Other pieces, in no particular order:

  * Update [`Java.Interop.Tools.JavaCallableWrappers`][4] so that
    static constructors aren't needed when LLVM Marshal Methods
    are used.

  * Update [`generator`][5] so that *two* sets of marshal methods are
    emitted: the current set e.g.
    `Activity.n_OnCreate_Landroid_os_Bundle_()`, and an "overload"
    set which has [`UnmanagedCallersOnlyAttribute`][6].
    LLVM Marshal Methods will be able to directly call these
    "unmanaged marshal methods" without the overhead of
    `mono_runtime_invoke()`; see also f48b97c.

  * Finish the LLVM code generator so that LLVM Marshal Methods are
    emitted into `libxamarin-app.so`.

  * Update the linker so that much of the earlier marshal method
    infrastructure is removed in Release apps.  When
    LLVM Marshal Methods are used, there is no need for
    `Activity.cb_onCreate_Landroid_os_Bundle_`,
    `Actvitiy.GetOnCreate_Landroid_os_Bundle_Handler()`, or the
    `Activity.n_OnCreate_Landroid_os_Bundle_()` without
    `[UnmanagedCallersOnly]`.

Meanwhile, we cannot remove the existing infrastructure, as the
current System.Reflection.Emit-oriented code is needed for faster app
builds, a desirable feature of Debug configuration builds.

LLVM Marshal Methods will be a Release configuration-only feature.

[0]: https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/design.html#native_method_arguments
[1]: https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/functions.html#RegisterNatives
[2]: https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/design.html#resolving_native_method_names
[3]: https://github.com/xamarin/xamarin-android/wiki/Blueprint#java-type-registration
[4]: https://github.com/xamarin/java.interop/tree/main/src/Java.Interop.Tools.JavaCallableWrappers
[5]: https://github.com/xamarin/xamarin-android/wiki/Blueprint#generator
[6]: https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.unmanagedcallersonlyattribute?view=net-6.0

Author: grendello

Directory.Build.props

@@ -24,6 +24,10 @@
     <RollForward>Major</RollForward>
   </PropertyGroup>
 
+  <PropertyGroup Condition=" '$(MSBuildRuntimeType)' == 'Core' ">
+    <_EnableMarshalMethods>NoThanks</_EnableMarshalMethods> <!-- set to YesPlease to enable -->
+  </PropertyGroup>
+
   <PropertyGroup>
     <ProductVersion>12.3.99</ProductVersion>
     <!-- NuGet package version numbers. See Documentation/guides/OneDotNet.md.

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

@@ -26,6 +26,8 @@ namespace Xamarin.Android.Tasks
 
 	public class GenerateJavaStubs : AndroidTask
 	{
+		public const string MarshalMethodsRegisterTaskKey = ".:!MarshalMethods!:.";
+
 		public override string TaskPrefix => "GJS";
 
 		[Required]
@@ -338,6 +340,9 @@ bool CreateJavaSources (IEnumerable<TypeDefinition> javaTypes, TypeDefinitionCac
 			string monoInit = GetMonoInitSource (AndroidSdkPlatform);
 			bool hasExportReference = ResolvedAssemblies.Any (assembly => Path.GetFileName (assembly.ItemSpec) == "Mono.Android.Export.dll");
 			bool generateOnCreateOverrides = int.Parse (AndroidSdkPlatform) <= 10;
+#if ENABLE_MARSHAL_METHODS
+			var overriddenMethodDescriptors = new List<OverriddenMethodDescriptor> ();
+#endif
 
 			bool ok = true;
 			foreach (var t in javaTypes) {
@@ -355,6 +360,9 @@ bool CreateJavaSources (IEnumerable<TypeDefinition> javaTypes, TypeDefinitionCac
 						};
 
 						jti.Generate (writer);
+#if ENABLE_MARSHAL_METHODS
+						overriddenMethodDescriptors.AddRange (jti.OverriddenMethodDescriptors);
+#endif
 						writer.Flush ();
 
 						var path = jti.GetDestinationPath (outputPath);
@@ -388,6 +396,9 @@ bool CreateJavaSources (IEnumerable<TypeDefinition> javaTypes, TypeDefinitionCac
 					}
 				}
 			}
+#if ENABLE_MARSHAL_METHODS
+			BuildEngine4.RegisterTaskObjectAssemblyLocal (MarshalMethodsRegisterTaskKey, overriddenMethodDescriptors, RegisteredTaskObjectLifetime.Build);
+#endif
 			return ok;
 		}
 

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

@@ -299,8 +299,16 @@ void AddEnvironment ()
 
 			int assemblyCount = 0;
 			HashSet<string> archAssemblyNames = null;
-
+#if ENABLE_MARSHAL_METHODS
+			var uniqueAssemblyNames = new HashSet<string> (StringComparer.OrdinalIgnoreCase);
+#endif
 			Action<ITaskItem> updateAssemblyCount = (ITaskItem assembly) => {
+				string assemblyName = Path.GetFileName (assembly.ItemSpec);
+#if ENABLE_MARSHAL_METHODS
+				if (!uniqueAssemblyNames.Contains (assemblyName)) {
+					uniqueAssemblyNames.Add (assemblyName);
+				}
+#endif
 				if (!UseAssemblyStore) {
 					assemblyCount++;
 					return;
@@ -316,7 +324,6 @@ void AddEnvironment ()
 				} else {
 					archAssemblyNames ??= new HashSet<string> (StringComparer.OrdinalIgnoreCase);
 
-					string assemblyName = Path.GetFileName (assembly.ItemSpec);
 					if (!archAssemblyNames.Contains (assemblyName)) {
 						assemblyCount++;
 						archAssemblyNames.Add (assemblyName);
@@ -431,16 +438,34 @@ void AddEnvironment ()
 				JNIEnvRegisterJniNativesToken = jnienv_registerjninatives_method_token,
 			};
 			appConfigAsmGen.Init ();
-
+#if ENABLE_MARSHAL_METHODS
+			var marshalMethodsAsmGen = new MarshalMethodsNativeAssemblyGenerator () {
+				NumberOfAssembliesInApk = assemblyCount,
+				UniqueAssemblyNames = uniqueAssemblyNames,
+				OverriddenMethodDescriptors = BuildEngine4.GetRegisteredTaskObjectAssemblyLocal<List<Java.Interop.Tools.JavaCallableWrappers.OverriddenMethodDescriptor>> (GenerateJavaStubs.MarshalMethodsRegisterTaskKey, RegisteredTaskObjectLifetime.Build)
+			};
+			marshalMethodsAsmGen.Init ();
+#endif
 			foreach (string abi in SupportedAbis) {
-				string baseAsmFilePath = Path.Combine (EnvironmentOutputDirectory, $"environment.{abi.ToLowerInvariant ()}");
-				string llFilePath  = $"{baseAsmFilePath}.ll";
+				string targetAbi = abi.ToLowerInvariant ();
+				string environmentBaseAsmFilePath = Path.Combine (EnvironmentOutputDirectory, $"environment.{targetAbi}");
+				string marshalMethodsBaseAsmFilePath = Path.Combine (EnvironmentOutputDirectory, $"marshal_methods.{targetAbi}");
+				string environmentLlFilePath  = $"{environmentBaseAsmFilePath}.ll";
+				string marshalMethodsLlFilePath = $"{marshalMethodsBaseAsmFilePath}.ll";
 
+				AndroidTargetArch targetArch = GetAndroidTargetArchForAbi (abi);
+				using (var sw = MemoryStreamPool.Shared.CreateStreamWriter ()) {
+					appConfigAsmGen.Write (targetArch, sw, environmentLlFilePath);
+					sw.Flush ();
+					Files.CopyIfStreamChanged (sw.BaseStream, environmentLlFilePath);
+				}
+#if ENABLE_MARSHAL_METHODS
 				using (var sw = MemoryStreamPool.Shared.CreateStreamWriter ()) {
-					appConfigAsmGen.Write (GetAndroidTargetArchForAbi (abi), sw, llFilePath);
+					marshalMethodsAsmGen.Write (targetArch, sw, marshalMethodsLlFilePath);
 					sw.Flush ();
-					Files.CopyIfStreamChanged (sw.BaseStream, llFilePath);
+					Files.CopyIfStreamChanged (sw.BaseStream, marshalMethodsLlFilePath);
 				}
+#endif
 			}
 
 			void AddEnvironmentVariable (string name, string value)

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

@@ -14,7 +14,9 @@ public class PrepareAbiItems : AndroidTask
 		const string TypeMapBase = "typemaps";
 		const string EnvBase = "environment";
 		const string CompressedAssembliesBase = "compressed_assemblies";
-
+#if ENABLE_MARSHAL_METHODS
+		const string MarshalMethodsBase = "marshal_methods";
+#endif
 		public override string TaskPrefix => "PAI";
 
 		[Required]
@@ -50,6 +52,10 @@ public override bool RunTask ()
 				baseName = EnvBase;
 			} else if (String.Compare ("compressed", Mode, StringComparison.OrdinalIgnoreCase) == 0) {
 				baseName = CompressedAssembliesBase;
+#if ENABLE_MARSHAL_METHODS
+			} else if (String.Compare ("marshal_methods", Mode, StringComparison.OrdinalIgnoreCase) == 0) {
+				baseName = MarshalMethodsBase;
+#endif
 			} else {
 				Log.LogError ($"Unknown mode: {Mode}");
 				return false;

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Resources/Base/BuildReleaseArm64SimpleDotNet.apkdesc

@@ -8,7 +8,7 @@
       "Size": 60736
     },
     "assemblies/Mono.Android.dll": {
-      "Size": 152435
+      "Size": 152344
     },
     "assemblies/rc.bin": {
       "Size": 1083
@@ -59,13 +59,13 @@
       "Size": 9591
     },
     "assemblies/UnnamedProject.dll": {
-      "Size": 3560
+      "Size": 3555
     },
     "classes.dex": {
       "Size": 348440
     },
     "lib/arm64-v8a/libmonodroid.so": {
-      "Size": 484512
+      "Size": 510920
     },
     "lib/arm64-v8a/libmonosgen-2.0.so": {
       "Size": 4667768
@@ -80,7 +80,7 @@
       "Size": 146816
     },
     "lib/arm64-v8a/libxamarin-app.so": {
-      "Size": 15944
+      "Size": 15904
     },
     "META-INF/BNDLTOOL.RSA": {
       "Size": 1213
@@ -92,7 +92,7 @@
       "Size": 3646
     },
     "res/drawable-hdpi-v4/icon.png": {
-      "Size": 4762
+      "Size": 4791
     },
     "res/drawable-mdpi-v4/icon.png": {
       "Size": 2200
@@ -116,5 +116,5 @@
       "Size": 1904
     }
   },
-  "PackageSize": 3492724
+  "PackageSize": 3500916
 }

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Resources/Base/BuildReleaseArm64SimpleLegacy.apkdesc

@@ -5,10 +5,10 @@
       "Size": 2604
     },
     "assemblies/Java.Interop.dll": {
-      "Size": 67948
+      "Size": 67950
     },
     "assemblies/Mono.Android.dll": {
-      "Size": 257194
+      "Size": 257187
     },
     "assemblies/mscorlib.dll": {
       "Size": 769016
@@ -23,7 +23,7 @@
       "Size": 2879
     },
     "classes.dex": {
-      "Size": 349820
+      "Size": 349736
     },
     "lib/arm64-v8a/libmono-btls-shared.so": {
       "Size": 1613872
@@ -32,7 +32,7 @@
       "Size": 750976
     },
     "lib/arm64-v8a/libmonodroid.so": {
-      "Size": 392576
+      "Size": 421872
     },
     "lib/arm64-v8a/libmonosgen-2.0.so": {
       "Size": 4030448
@@ -74,5 +74,5 @@
       "Size": 1724
     }
   },
-  "PackageSize": 4044500
+  "PackageSize": 4052692
 }

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Resources/Base/BuildReleaseArm64XFormsDotNet.apkdesc

@@ -11,7 +11,7 @@
       "Size": 66806
     },
     "assemblies/Mono.Android.dll": {
-      "Size": 447633
+      "Size": 447543
     },
     "assemblies/mscorlib.dll": {
       "Size": 3888
@@ -119,7 +119,7 @@
       "Size": 1906
     },
     "assemblies/UnnamedProject.dll": {
-      "Size": 117250
+      "Size": 117244
     },
     "assemblies/Xamarin.AndroidX.Activity.dll": {
       "Size": 5941
@@ -191,7 +191,7 @@
       "Size": 3460820
     },
     "lib/arm64-v8a/libmonodroid.so": {
-      "Size": 484512
+      "Size": 510920
     },
     "lib/arm64-v8a/libmonosgen-2.0.so": {
       "Size": 4667768
@@ -206,7 +206,7 @@
       "Size": 146816
     },
     "lib/arm64-v8a/libxamarin-app.so": {
-      "Size": 98480
+      "Size": 98440
     },
     "META-INF/android.support.design_material.version": {
       "Size": 12
@@ -773,7 +773,7 @@
       "Size": 470
     },
     "res/drawable-hdpi-v4/icon.png": {
-      "Size": 4762
+      "Size": 4791
     },
     "res/drawable-hdpi-v4/notification_bg_low_normal.9.png": {
       "Size": 212
@@ -1961,5 +1961,5 @@
       "Size": 341228
     }
   },
-  "PackageSize": 8347981
+  "PackageSize": 8356173
 }

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Resources/Base/BuildReleaseArm64XFormsLegacy.apkdesc

@@ -8,10 +8,10 @@
       "Size": 7215
     },
     "assemblies/Java.Interop.dll": {
-      "Size": 68913
+      "Size": 68916
     },
     "assemblies/Mono.Android.dll": {
-      "Size": 567718
+      "Size": 567711
     },
     "assemblies/Mono.Security.dll": {
       "Size": 68432
@@ -65,22 +65,22 @@
       "Size": 131930
     },
     "assemblies/Xamarin.AndroidX.DrawerLayout.dll": {
-      "Size": 15426
+      "Size": 15425
     },
     "assemblies/Xamarin.AndroidX.Fragment.dll": {
-      "Size": 43135
+      "Size": 43134
     },
     "assemblies/Xamarin.AndroidX.Legacy.Support.Core.UI.dll": {
-      "Size": 6715
+      "Size": 6714
     },
     "assemblies/Xamarin.AndroidX.Lifecycle.Common.dll": {
       "Size": 7062
     },
     "assemblies/Xamarin.AndroidX.Lifecycle.LiveData.Core.dll": {
-      "Size": 7193
+      "Size": 7194
     },
     "assemblies/Xamarin.AndroidX.Lifecycle.ViewModel.dll": {
-      "Size": 4872
+      "Size": 4873
     },
     "assemblies/Xamarin.AndroidX.Loader.dll": {
       "Size": 13585
@@ -113,7 +113,7 @@
       "Size": 43497
     },
     "classes.dex": {
-      "Size": 3462252
+      "Size": 3462080
     },
     "lib/arm64-v8a/libmono-btls-shared.so": {
       "Size": 1613872
@@ -122,7 +122,7 @@
       "Size": 750976
     },
     "lib/arm64-v8a/libmonodroid.so": {
-      "Size": 392576
+      "Size": 421872
     },
     "lib/arm64-v8a/libmonosgen-2.0.so": {
       "Size": 4030448
@@ -1883,5 +1883,5 @@
       "Size": 341040
     }
   },
-  "PackageSize": 9562270
+  "PackageSize": 9570462
 }

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

@@ -1,10 +1,8 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-using System.Text;
 
 using Java.Interop.Tools.TypeNameMappings;
-using K4os.Hash.xxHash;
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
 
@@ -342,21 +340,11 @@ void WriteDSOCache (LlvmIrGenerator generator)
 
 			// We need to hash here, because the hash is architecture-specific
 			foreach (StructureInstance<DSOCacheEntry> entry in dsoCache) {
-				entry.Obj.hash = HashName (entry.Obj.HashedName);
+				entry.Obj.hash = HashName (entry.Obj.HashedName, is64Bit);
 			}
 			dsoCache.Sort ((StructureInstance<DSOCacheEntry> a, StructureInstance<DSOCacheEntry> b) => a.Obj.hash.CompareTo (b.Obj.hash));
 
 			generator.WriteStructureArray (dsoCacheEntryStructureInfo, dsoCache, "dso_cache");
-
-			ulong HashName (string name)
-			{
-				byte[] nameBytes = Encoding.UTF8.GetBytes (name);
-				if (is64Bit) {
-					return XXH64.DigestOf (nameBytes, 0, nameBytes.Length);
-				}
-
-				return (ulong)XXH32.DigestOf (nameBytes, 0, nameBytes.Length);
-			}
 		}
 	}
 }