Add support for using NativeAOT. (#17374)

Add support for using NativeAOT on all our platforms.

This contains numerous changes in a lot of places to add support for
NativeAOT:

* build logic
* runtime
* managed code
* tests 

And it all pretty much consists of special-casing NativeAOT everywhere
we need to.

Note: NativeAOT doesn't work on macOS yet, because a dotnet/runtime fix
is required, and thus the corresponding test variations for
monotouch-test have been commented out.

This PR is best reviewed commit-by-commit.

This contributes towards #17339.

.gitmodules

@@ -13,15 +13,15 @@
 [submodule "external/Touch.Unit"]
     path = external/Touch.Unit
     url = ../../spouliot/Touch.Unit.git
-    branch = main
+    branch = net8.0
 [submodule "external/Xamarin.MacDev"]
     path = external/Xamarin.MacDev
     url = ../../xamarin/Xamarin.MacDev
     branch = main
 [submodule "external/MonoTouch.Dialog"]
     path = external/MonoTouch.Dialog
     url = ../../migueldeicaza/MonoTouch.Dialog
-    branch = dotnet
+    branch = net8.0
 [submodule "api-tools"]
     path = external/api-tools
     url = ../../rolfbjarne/api-tools

Make.config

@@ -288,6 +288,12 @@ DOTNET_MIN_TVOS_SDK_VERSION=11.0
 DOTNET_MIN_MACCATALYST_SDK_VERSION=13.1
 DOTNET_MIN_MACOS_SDK_VERSION=10.15
 
+# Minimum OS versions when using NativeOAT - these are at least the general min versions above (but may be higher).
+DOTNET_MIN_NATIVEAOT_IOS_SDK_VERSION=12.2
+DOTNET_MIN_NATIVEAOT_TVOS_SDK_VERSION=12.2
+DOTNET_MIN_NATIVEAOT_MACCATALYST_SDK_VERSION=13.1
+DOTNET_MIN_NATIVEAOT_MACOS_SDK_VERSION=10.15
+
 # The min simulator version available in the Xcode we're using
 MIN_IOS_SIMULATOR_VERSION=13.7
 MIN_WATCHOS_SIMULATOR_VERSION=7.0
@@ -712,6 +718,7 @@ DOTNET_PLATFORMS=
 ifdef INCLUDE_IOS
 DOTNET_PLATFORMS+=iOS
 DOTNET_IOS_BITNESSES+=64
+DOTNET_NATIVEAOT_PLATFORMS+=iOS
 
 # 32-bit architectures
 ifdef IOS_SUPPORTS_32BIT_ARCHITECTURES
@@ -735,6 +742,7 @@ endif # INCLUDE_IOS
 ifdef INCLUDE_TVOS
 DOTNET_PLATFORMS+=tvOS
 DOTNET_TVOS_BITNESSES+=64
+DOTNET_NATIVEAOT_PLATFORMS+=tvOS
 ifdef INCLUDE_DEVICE
 DOTNET_TVOS_RUNTIME_IDENTIFIERS=tvos-arm64 tvossimulator-x64 tvossimulator-arm64
 else
@@ -758,6 +766,7 @@ endif
 ifdef INCLUDE_MACCATALYST
 DOTNET_PLATFORMS+=MacCatalyst
 DOTNET_MACCATALYST_BITNESSES+=64
+DOTNET_NATIVEAOT_PLATFORMS+=MacCatalyst
 DOTNET_MACCATALYST_RUNTIME_IDENTIFIERS=maccatalyst-x64 maccatalyst-arm64
 DOTNET_MACCATALYST_RUNTIME_IDENTIFIERS_64+=$(DOTNET_MACCATALYST_RUNTIME_IDENTIFIERS)
 endif
@@ -766,6 +775,7 @@ ifdef INCLUDE_MAC
 DOTNET_PLATFORMS+=macOS
 DOTNET_CORECLR_PLATFORMS+=macOS
 DOTNET_MACOS_BITNESSES+=64
+DOTNET_NATIVEAOT_PLATFORMS+=macOS
 DOTNET_MACOS_RUNTIME_IDENTIFIERS=osx-x64 osx-arm64
 DOTNET_MACOS_RUNTIME_IDENTIFIERS_64=$(DOTNET_MACOS_RUNTIME_IDENTIFIERS)
 endif

dotnet/generate-target-platforms.csharp

@@ -24,10 +24,16 @@ var doc = new XmlDocument ();
 doc.Load (plistPath);
 var nodes = doc.SelectNodes ($"/plist/dict/key[text()='KnownVersions']/following-sibling::dict[1]/key[text()='{platform}']/following-sibling::array[1]/string");
 
+var allLines = File.ReadAllLines ("../Make.config");
+
 var minSdkVersionName = $"DOTNET_MIN_{platform.ToUpper ()}_SDK_VERSION";
-var minSdkVersionString = File.ReadAllLines ("../Make.config").Single (v => v.StartsWith (minSdkVersionName + "=", StringComparison.Ordinal)).Substring (minSdkVersionName.Length + 1);
+var minSdkVersionString = allLines.Single (v => v.StartsWith (minSdkVersionName + "=", StringComparison.Ordinal)).Substring (minSdkVersionName.Length + 1);
 var minSdkVersion = Version.Parse (minSdkVersionString);
 
+var minNativeAotSdkVersionName = $"DOTNET_MIN_NATIVEAOT_{platform.ToUpper ()}_SDK_VERSION";
+var minNativeAotSdkVersionString = allLines.Single (v => v.StartsWith (minNativeAotSdkVersionName + "=", StringComparison.Ordinal)).Substring (minNativeAotSdkVersionName.Length + 1);
+var minNativeAotSdkVersion = Version.Parse (minNativeAotSdkVersionString);
+
 using (TextWriter writer = new StreamWriter (outputPath)) {
 	writer.WriteLine ($"<!-- This file contains a generated list of the {platform} platform versions that are supported for this SDK -->");
 	writer.WriteLine ($"<!-- Generation script: https://github.com/xamarin/xamarin-macios/blob/main/dotnet/generate-target-platforms.csharp -->");
@@ -36,17 +42,23 @@ using (TextWriter writer = new StreamWriter (outputPath)) {
 
 	foreach (XmlNode n in nodes) {
 		var version = n.InnerText;
-		if (Version.Parse (version) < minSdkVersion)
+		var parsedVersion = Version.Parse (version);
+		if (parsedVersion < minSdkVersion)
 			continue;
-		writer.WriteLine ($"\t\t<{platform}SdkSupportedTargetPlatformVersion Include=\"{n.InnerText}\" />");
+		if (parsedVersion < minNativeAotSdkVersion) {
+			writer.WriteLine ($"\t\t<{platform}SdkSupportedTargetPlatformVersion Include=\"{n.InnerText}\" Condition=\"!('$(PublishAot)' == 'true' And '$(_IsPublishing)' == 'true')\" />");
+		} else {
+			writer.WriteLine ($"\t\t<{platform}SdkSupportedTargetPlatformVersion Include=\"{n.InnerText}\" />");
+		}
 	}
 
 	writer.WriteLine ("\t</ItemGroup>");
 	writer.WriteLine ("\t<ItemGroup>");
 	writer.WriteLine ($"\t\t<SdkSupportedTargetPlatformVersion Condition=\"'$(TargetPlatformIdentifier)' == '{platform}'\" Include=\"@({platform}SdkSupportedTargetPlatformVersion)\" />");
 	writer.WriteLine ("\t</ItemGroup>");
 	writer.WriteLine ("\t<PropertyGroup>");
-	writer.WriteLine ($"\t\t<{platform}MinSupportedOSPlatformVersion>{minSdkVersionString}</{platform}MinSupportedOSPlatformVersion>");
+	writer.WriteLine ($"\t\t<{platform}MinSupportedOSPlatformVersion Condition=\"!('$(PublishAot)' == 'true' And '$(_IsPublishing)' == 'true')\">{minSdkVersionString}</{platform}MinSupportedOSPlatformVersion>");
+	writer.WriteLine ($"\t\t<{platform}MinSupportedOSPlatformVersion Condition=\"'$(PublishAot)' == 'true' And '$(_IsPublishing)' == 'true'\">{minNativeAotSdkVersionString}</{platform}MinSupportedOSPlatformVersion>");
 	writer.WriteLine ("\t</PropertyGroup>");
 	writer.WriteLine ("</Project>");
 }

dotnet/targets/Xamarin.Shared.Sdk.DefaultItems.targets

@@ -11,8 +11,17 @@
     <EnableDefaultmacOSItems Condition=" '$(_PlatformName)' == 'macOS' And '$(EnableDefaultmacOSItems)' == '' ">$(EnableDefaultItems)</EnableDefaultmacOSItems>
     <EnableDefaultMacCatalystItems Condition=" '$(_PlatformName)' == 'MacCatalyst' And '$(EnableDefaultMacCatalystItems)' == '' ">$(EnableDefaultItems)</EnableDefaultMacCatalystItems>
 
-    <UseMonoRuntime Condition=" '$(UseMonoRuntime)' == '' And '$(_PlatformName)' != 'macOS'">true</UseMonoRuntime>
+    <!--
+        PublishAot should only take effect when doing 'dotnet publish', not when doing 'dotnet build'. We distinguish these cases using the '_IsPublishing' property,
+        but it's rather annoying to always have to check both PublishAot and _IsPublishing to see if we're using NativeAOT, so introduce a third property that's
+        only set to true if both PublishAot=true and _IsPublishing=true
+    -->
+    <_UseNativeAot Condition="'$(PublishAot)' == 'true' And '$(_IsPublishing)' == 'true'">true</_UseNativeAot>
+
     <UseMonoRuntime Condition=" '$(UseMonoRuntime)' == '' And '$(_PlatformName)' == 'macOS'">false</UseMonoRuntime>
+    <UseMonoRuntime Condition=" '$(UseMonoRuntime)' == '' And '$(_UseNativeAot)' == 'true'">false</UseMonoRuntime>
+    <UseMonoRuntime Condition=" '$(UseMonoRuntime)' == ''">true</UseMonoRuntime>
+
   </PropertyGroup>
 
   <ItemGroup>

dotnet/targets/Xamarin.Shared.Sdk.props

@@ -58,6 +58,13 @@
 
 		<!-- Explicitly export symbols using clang command-line option "-exported_symbols_list export_list" -->
 		<_ExportSymbolsExplicitly Condition="'$(_ExportSymbolsExplicitly)' == ''">true</_ExportSymbolsExplicitly>
+
+		<!--
+			Some runtime libraries feature switches defaults that need to be set early
+			Available feature switches: https://github.com/dotnet/runtime/blob/master/docs/workflow/trimming/feature-switches.md
+		-->
+		<!-- AutoreleasePoolSupport needs to be set earlier than other switches, so that illink doesn't override it - https://github.com/dotnet/runtime/pull/86753 - so it's set here, instead of in Xamarin.Shared.Sdk.targets -->
+		<AutoreleasePoolSupport Condition="'$(AutoreleasePoolSupport)' == ''">true</AutoreleasePoolSupport>
 	</PropertyGroup>
 
 	<!-- Set the default RuntimeIdentifier if not already specified. -->
@@ -95,6 +102,20 @@
 		<SelfContained>true</SelfContained>
 	</PropertyGroup>
 
+	<!--
+
+		SelfContained is automatically enabled if PublishAot is true, and that
+		doesn't work properly (restore fails because RuntimeIdentifier is not
+		set) when doing the outer build of a universal apps (when
+		RuntimeIdentifier=''), so manually disable SelfContained in that case.
+
+		This might not be necessary after: https://github.com/dotnet/sdk/pull/33229
+
+	-->
+	<PropertyGroup Condition="'$(PublishAot)' == 'true' And '$(_IsPublishing)' == 'true' And '$(RuntimeIdentifiers)' != '' And '$(RuntimeIdentifier)' == '' And '$(SelfContained)' == ''">
+		<SelfContained>false</SelfContained>
+	</PropertyGroup>
+
 	<!--
 		Enable LLVM by default for mobile release builds.
 
@@ -105,4 +126,22 @@
 	<PropertyGroup Condition="'$(MtouchUseLlvm)' == '' And '$(Configuration)' == 'Release' And ('$(_PlatformName)' == 'iOS' Or '$(_PlatformName)' == 'tvOS')">
 		<MtouchUseLlvm>true</MtouchUseLlvm>
 	</PropertyGroup>
+
+	<!-- Various options when using NativeAOT -->
+	<PropertyGroup Condition="'$(PublishAot)' == 'true' And '$(_IsPublishing)' == 'true'">
+		<!-- Disable our own assembly IL stripping logic, because ILC does that already -->
+		<EnableAssemblyILStripping>false</EnableAssemblyILStripping>
+
+		<!-- We're using our own native main function when using NativeAOT -->
+		<CustomNativeMain>true</CustomNativeMain>
+
+		<!-- We must find the BCL libraries using the runtime pack instead of using the built-in NativeAOT BCL -->
+		<PublishAotUsingRuntimePack>true</PublishAotUsingRuntimePack>
+
+		<!-- This turns off some NativeAOT logic we don't want nor need -->
+		<NativeCompilationDuringPublish>false</NativeCompilationDuringPublish>
+
+		<!-- This works around an issue in NativeAOT: https://github.com/dotnet/runtime/issues/86186 -->
+		<IlcKeepManagedDebuggerSupport>true</IlcKeepManagedDebuggerSupport>
+	</PropertyGroup>
 </Project>