[TrimmableTypeMap][NativeAOT] Initialize trimmable typemap runtime

[simonrozsival]

Summary

Fix NativeAOT startup with the trimmable typemap implementation enabled, and make the generated trimmable typemap usable for NativeAOT without rooting the full Mono.Android framework ACW closure.

This PR is currently stacked on the trimmable array typemap work in #11238 so the NativeAOT path can use the current array-entry implementation and so the PR shows the real size impact of the combined work.

Key changes:

• Initialize generated trimmable typemap data before creating the NativeAOT Java.Interop runtime.
• Register trimmable typemap native methods after JniRuntime.Current is available.
• Add generated typemap assemblies to ILC inputs before ILC input computation and emit --typemap-entry-assembly for the root typemap assembly.
• Populate NativeAOT JnienvInitializeArgs with GC-user-peer class refs and GREF threshold so managed runtime state matches the Mono/CoreCLR init path.
• Add an explicit RuntimeFeature.IsNativeAotRuntime switch for NativeAOT-specific runtime identity.
• Keep scanning framework assemblies for typemap entries, but treat framework ACW implementors as conditional trim-target entries instead of unconditional user ACW roots.
• Compile the shared __ArrayMapRankN anchors into Mono.Android so NativeAOT can resolve the generated array typemap groups.

Fixes #11052.

Current state

The repo HelloWorld sample now builds, installs, and launches with NativeAOT + trimmable typemap enabled.

Current clean android-arm64 Release output:

Artifact	Size
signed APK	3,601,583 bytes
signed AAB	1,543,717 bytes
libHelloWorld.DotNet.so	3,481,288 bytes

This is about 1.4 MiB smaller than the earlier NativeAOT managed/legacy typemap result measured in this investigation, while startup remains in the same range. The latest smoke launch on emulator-5554 was successful:

Status: ok
LaunchState: COLD
TotalTime: 254
WaitTime: 258

The size is not the final expected floor. There is still obvious room to improve as we continue identifying and reducing NativeAOT codegen and metadata roots; this PR gets the NativeAOT trimmable typemap path into a working, measurable state so those follow-up reductions can be targeted with real data.

Validation

MSBUILDDISABLENODEREUSE=1 ./dotnet-local.sh build \
  src/Xamarin.Android.Build.Tasks/Xamarin.Android.Build.Tasks.csproj \
  -c Debug -nr:false --nologo

MSBUILDDISABLENODEREUSE=1 ./dotnet-local.sh test \
  tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests.csproj \
  -c Debug -nr:false --nologo

MSBUILDDISABLENODEREUSE=1 ./dotnet-local.sh test \
  src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Xamarin.Android.Build.Tests.csproj \
  -c Debug -nr:false --nologo \
  --filter FullyQualifiedName~GenerateTrimmableTypeMapTests

Results:

• Xamarin.Android.Build.Tasks.csproj build passed.
• Microsoft.Android.Sdk.TrimmableTypeMap.Tests: 457/457 passed.
• focused GenerateTrimmableTypeMapTests: 9/9 passed.
• clean HelloWorld NativeAOT trimmable build passed with no __ArrayMapRank ILC failure.
• HelloWorld installed and launched successfully on emulator-5554; logcat showed libHelloWorld.DotNet.so loaded and no fatal exception/native crash.

[Copilot]

Pull request overview

This PR wires the trimmable typemap path into NativeAOT startup and build-time ILC inputs so NativeAOT apps can initialize the managed/runtime typemap state before Java interop begins.

Changes:

• Adds NativeAOT-specific build plumbing for trimmable typemap assemblies and runtime feature switches.
• Updates NativeAOT host/runtime initialization so typemap data is initialized earlier and native registration happens after JniRuntime.Current is available.
• Aligns NativeAOT runtime state with the Mono/CoreCLR init path for GREF/GC-user-peer setup and runtime identification.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.TypeMap.Trimmable.NativeAOT.targets	Adds typemap assemblies to NativeAOT ILC inputs and sets the typemap entry assembly.
src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk.NativeAOT.targets	Adds a NativeAOT runtime feature switch to host configuration.
src/native/nativeaot/host/host.cc	Populates NativeAOT init args with GREF threshold and GC-user-peer class refs.
src/Mono.Android/Microsoft.Android.Runtime/RuntimeFeature.cs	Introduces IsNativeAotRuntime runtime identity switch.
src/Mono.Android/Android.Runtime/JNIEnvInit.cs	Splits NativeAOT typemap initialization/registration into explicit helper steps and applies more init state from args.
src/Mono.Android/Android.Runtime/JNIEnv.cs	Treats NativeAOT like CoreCLR for uncaught exception propagation.
src/Mono.Android/Android.Runtime/AndroidRuntimeInternal.cs	Treats NativeAOT like CoreCLR for unhandled-exception callback selection.
src/Microsoft.Android.Runtime.NativeAOT/Android.Runtime.NativeAOT/JavaInteropRuntime.cs	Reorders NativeAOT startup to initialize typemap data before runtime creation and register natives afterward.

[simonrozsival]

Additional NativeAOT testing update:

• Made ForceUnconditionalEntries configurable and disabled it for NativeAOT trimmable typemap builds only.
• Rebuilt HelloWorld as single-RID android-arm64 across the measured configs using -p:RuntimeIdentifier=android-arm64.

Arm64-only local Debug-pack measurements:

Variant	APK size	TotalTime avg / median	Runs
Mono	8.47 MiB	242.8 / 210 ms	414, 211, 198, 210, 181
CoreCLR llvm-ir typemap	14.64 MiB	259.6 / 235 ms	381, 210, 235, 218, 254
CoreCLR trimmable typemap	24.70 MiB	290.0 / 264 ms	404, 304, 229, 249, 264
NativeAOT original managed typemap	4.86 MiB	169.8 / 163 ms	230, 165, 152, 139, 163
NativeAOT trimmable typemap, ForceUnconditionalEntries=false	11.84 MiB	186.6 / 170 ms	262, 164, 171, 170, 166

No fatal/crash logcat hits were found for these runs. The NativeAOT trimmable APK contains only lib/arm64-v8a/libHelloWorld.DotNet.so after switching to RuntimeIdentifier=android-arm64.

[simonrozsival]

Follow-up on blanket rooting for NativeAOT trimmable typemap:

• The current NativeAOT trimmable ILC response has no --root: entries and no root descriptors.
• I found one real blanket root item: we were passing every generated typemap assembly to UnmanagedEntryPointsAssembly, which emitted:
  • _HelloLibrary.DotNet.TypeMap
  • _HelloWorld.DotNet.TypeMap
  • _Java.Interop.TypeMap
  • _Microsoft.Android.TypeMaps
  • _Mono.Android.TypeMap
• I narrowed this so only app/library typemap assemblies are exported for JNI UCO wrappers. Framework/root typemap assemblies stay as IlcReference inputs, but are no longer unmanaged-entrypoint roots.

Validated NativeAOT trimmable arm64 after the change:

--scanreflection
--generateunmanagedentrypoints:System.Private.CoreLib,HIDDEN
--generateunmanagedentrypoints:_HelloLibrary.DotNet.TypeMap
--generateunmanagedentrypoints:_HelloWorld.DotNet.TypeMap
--generateunmanagedentrypoints:Microsoft.Android.Runtime.NativeAOT

Result:

APK: 13,124,718 bytes / 12.52 MiB
libHelloWorld.DotNet.so: 13,000,904 bytes / 12.40 MiB
TotalTime runs: 266, 166, 165, 168, 169 ms
TotalTime avg/median: 186.8 / 168.0 ms
No fatal/crash logcat hits

I also tried disabling IlcScanReflection for this path. That produced much smaller APKs, but it is not currently runnable:

• without scanreflection: APK 3.22 MiB, crash in TypeMapLazyDictionary.CreateExternalTypeMap(RuntimeType) for Java.Lang.Object
• with narrow rd.xml / dynamic dependencies: APK ~4.0-4.3 MiB, same crash
• with IlcGenerateCompleteTypeMetadata=true: APK 13.76 MiB, same crash

So --scanreflection appears to be required today for ILC to emit the NativeAOT type-map blob consumed by TypeMapLazyDictionary, even though --typemap-entry-assembly:_Microsoft.Android.TypeMaps is present. I did not commit the broken no-scan experiment.