[mono][fullaot] Calling static virtual method from a generic method leads to "Attempting to JIT" error

[lambdageek]

Compile this sample for FullAOT, then make run. Expected result: "Taking transition" is printed out. Actual result:

Unhandled Exception:
System.ExecutionEngineException: Attempting to JIT compile method 'St`1<Brz> Q:Delta<Brz> (St`1<Brz>,M`1<Brz>)' while running in aot-only mode. See https://docs.microsoft.com/xamarin/ios/internals/limitations for more information.

   at HelloWorld.Program.Main(String[] args) in /Users/alklig/work/dotnet-runtime/runtime/src/mono/sample/HelloWorld/Program.cs:line 45
[ERROR] FATAL UNHANDLED EXCEPTION: System.ExecutionEngineException: Attempting to JIT compile method 'St`1<Brz> Q:Delta<Brz> (St`1<Brz>,M`1<Brz>)' while running in aot-only mode. See https://docs.microsoft.com/xamarin/ios/internals/limitations for more information.

   at HelloWorld.Program.Main(String[] args) in /Users/alklig/work/dotnet-runtime/runtime/src/mono/sample/HelloWorld/Program.cs:line 45

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;

public class St<T> {
    public T t;
    public T GetIt() => t;
}

public class M<T> {
    public bool Matches(T state) => false;
}

public interface Itf<T>  {
    static abstract St<T> TakeTransition(M<T> matcher, T state);
}

public class Q {
    public St<T> Delta<T> (St<T> src, M<T> matcher) where T : Itf<T>{
	Console.WriteLine ("Taking transition");
	return T.TakeTransition(matcher, src.GetIt());
    }
}

public class Brz : Itf<Brz> {
    public static St<Brz> TakeTransition (M<Brz> matcher, Brz state) {
	return new St<Brz>() { t = state };
    }
}

namespace HelloWorld
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            bool isMono = typeof(object).Assembly.GetType("Mono.RuntimeStructs") != null;
            Console.WriteLine($"Hello World {(isMono ? "from Mono!" : "from CoreCLR!")}");
            Console.WriteLine(typeof(object).Assembly.FullName);
            Console.WriteLine(System.Reflection.Assembly.GetEntryAssembly ());
            Console.WriteLine(System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription);
	    Console.WriteLine (GetEE());

	    new Q().Delta<Brz> (new St<Brz>(), new M<Brz>());
        }

	public static string GetEE() {
	    if (!System.Runtime.CompilerServices.RuntimeFeature.IsDynamicCodeSupported)
		return "FullAOT";
	    if (!System.Runtime.CompilerServices.RuntimeFeature.IsDynamicCodeCompiled)
		return "Interp";
	    return "JIT";
	}
    }
}

Makefile:

TOP=../../../../
DOTNET:=$(TOP)./dotnet.sh
DOTNET_Q_ARGS=--nologo -v:q -consoleloggerparameters:NoSummary

MONO_CONFIG ?=Release
MONO_ARCH=x64

OS := $(shell uname -s)
ifeq ($(OS),Darwin)
	TARGET_OS=osx
else
	TARGET_OS=linux
endif

MONO_ENV_OPTIONS ?=--full-aot

ARTIFACTS_BIN=$(abspath $(TOP)artifacts/bin/HelloWorld/$(MONO_ARCH)/$(MONO_CONFIG)/$(TARGET_OS)-$(MONO_ARCH))

MONO_AOT_COMPILER=$(abspath $(TOP)artifacts/obj/mono/OSX.x64.Release/out/bin/mono-sgen)

publish: $(ARTIFACTS_BIN)/.touch-publish

$(ARTIFACTS_BIN)/.touch-publish: HelloWorld.csproj Program.cs
	$(DOTNET) publish -c $(MONO_CONFIG) -r $(TARGET_OS)-$(MONO_ARCH) /p:RunAOTCompilation=true
	touch $(ARTIFACTS_BIN)/.touch-publish

$(ARTIFACTS_BIN)/.touch-fullaot: $(ARTIFACTS_BIN)/.touch-publish
	pushd $(ARTIFACTS_BIN)/publish ; \
	for i in *.dll ; do \
		MONO_PATH=$(ARTIFACTS_BIN)/publish \
		$(MONO_AOT_COMPILER) --aot=full $${i} ; \
	done ; \
	popd
	touch $(ARTIFACTS_BIN)/.touch-fullaot

aot: $(ARTIFACTS_BIN)/.touch-fullaot

.PHONY: run

run: $(ARTIFACTS_BIN)/.touch-fullaot
	COMPlus_DebugWriteToStdErr=1 \
	MONO_ENV_OPTIONS="$(MONO_ENV_OPTIONS)" \
	$(TOP)artifacts/bin/HelloWorld/$(MONO_ARCH)/$(MONO_CONFIG)/$(TARGET_OS)-$(MONO_ARCH)/publish/HelloWorld

clean:
	rm -rf $(TOP)artifacts/bin/HelloWorld/

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[lambdageek]

FYI @vargaz

[lambdageek]

Running with mono-sgen --aot=full -v -v -v -v -v we can see this during AOT compilation of HelloWorld.dll:

cmethod = St`1<T_GSHAREDVT> Itf`1<T_GSHAREDVT>:TakeTransition (M`1<T_GSHAREDVT>,T_GSHAREDVT)
sharing failed for method .Q.Delta/2 opcode call line 7362

runtime/src/mono/mono/mini/method-to-ir.c

Lines 7360 to 7362 in a702712

	if (m_method_is_static (cil_method) && mini_class_check_context_used (cfg, constrained_class))
	// FIXME:
	GENERIC_SHARING_FAILURE (CEE_CALL);