[msbuild/dotnet] Add support for 'MonoUseCompressedInterfaceBitmap' to enable compressed interface bitmaps. (#23834)

Add support for the `MonoUseCompressedInterfaceBitmap` MSBuild property to enable the usage of compressed interface bitmaps in Mono.

Author: rolfbjarne

docs/building-apps/build-properties.md

@@ -683,6 +683,28 @@ Consider using the unified [AppBundleResourcePrefix](#appbundleresourceprefix) p
 
 See also [IPhoneResourcePrefix](#iphoneresourceprefix) and [XamMacResourcePrefix](#xammacresourceprefix).
 
+## MonoUseCompressedInterfaceBitmap
+
+This directs the Mono runtime to use a compressed version of interface bitmaps
+(interface bitmaps are used to determine whether a certain types implements a
+given interface).
+
+These bitmaps can use a significant amount of memory at runtime, in particular
+for apps that have a substantial amount of interfaces.
+
+This setting is disabled by default, but it can be enabled like this, which
+will decrease the amount of memory used at runtime:
+
+```xml
+<PropertyGroup>
+    <MonoUseCompressedInterfaceBitmap>true</MonoUseCompressedInterfaceBitmap>
+</PropertyGroup>
+```
+
+The downside is that type checks (`obj is SomeInterface`) will be slower.
+
+Only applicable when using the Mono runtime.
+
 ## MtouchDebug
 
 Enables debug mode for app bundle creation.

dotnet/targets/Xamarin.Shared.Sdk.targets

@@ -1380,10 +1380,15 @@
 			DependsOnTargets="$(_AOTCompileDependsOn)"
 		>
 
+		<ItemGroup>
+			<_AotEnvironment Condition="'$(MonoUseCompressedInterfaceBitmap)' == 'true'" Include="MONO_COMPRESSED_INTERFACE_BITMAP" Value="1" />
+		</ItemGroup>
+
 		<AOTCompile
 			SessionId="$(BuildSessionId)"
 			Condition="'$(IsMacEnabled)' == 'true'"
 			Assemblies="@(_AssembliesToAOT)"
+			AotEnvironment="@(_AotEnvironment)"
 			AOTCompilerPath="$(_XamarinAOTCompiler)"
 			InputDirectory="$(_AOTInputDirectory)"
 			MaxDegreeOfParallelism="$(AotCompileMaxDegreeOfParallelism)"

msbuild/Xamarin.MacDev.Tasks/Tasks/AOTCompile.cs

@@ -25,6 +25,8 @@ public class AOTCompile : XamarinParallelTask, ITaskCallback, ICancelableTask {
 		[Required]
 		public ITaskItem [] Assemblies { get; set; } = Array.Empty<ITaskItem> ();
 
+		public ITaskItem [] AotEnvironment { get; set; } = Array.Empty<ITaskItem> ();
+
 		[Required]
 		public string InputDirectory { get; set; } = string.Empty;
 
@@ -334,8 +336,12 @@ public override bool Execute ()
 				listOfArguments.Add (new (arguments, input));
 			}
 
+			var environment = new Dictionary<string, string?> ();
+			foreach (var item in AotEnvironment)
+				environment [item.ItemSpec] = item.GetMetadata ("Value");
+
 			ForEach (listOfArguments, (arg) => {
-				ExecuteAsync (AOTCompilerPath, arg.Arguments, sdkDevPath: SdkDevPath, showErrorIfFailure: false /* we show our own error below */)
+				ExecuteAsync (AOTCompilerPath, arg.Arguments, environment: environment, sdkDevPath: SdkDevPath, showErrorIfFailure: false /* we show our own error below */)
 					.ContinueWith ((v) => {
 						if (v.Result.ExitCode != 0)
 							Log.LogError (MSBStrings.E7118 /* Failed to AOT compile {0}, the AOT compiler exited with code {1} */, Path.GetFileName (arg.Input), v.Result.ExitCode);

msbuild/Xamarin.Shared/Xamarin.Shared.targets

@@ -2200,6 +2200,10 @@ Copyright (C) 2018 Microsoft. All rights reserved.
 			<MarshalObjectiveCExceptionMode Condition="'$(MarshalObjectiveCExceptionMode)' == ''">$(_MarshalObjectiveCExceptionMode)</MarshalObjectiveCExceptionMode>
 		</PropertyGroup>
 
+		<ItemGroup>
+			<_BundlerEnvironmentVariables Condition="'$(MonoUseCompressedInterfaceBitmap)' == 'true'" Include="MONO_COMPRESSED_INTERFACE_BITMAP" Value="1" />
+		</ItemGroup>
+
 		<ParseBundlerArguments
 			Aot="@(_AotArguments)"
 			ExtraArgs="$(AppBundleExtraOptions)"