Update EmitTaskReturningThunk in Native AOT

src/coreclr/nativeaot/System.Private.CoreLib/src/System.Private.CoreLib.csproj

@@ -244,6 +244,7 @@
     <Compile Include="System\Runtime\CompilerServices\AnalysisCharacteristicAttribute.cs" />
     <Compile Include="System\Runtime\CompilerServices\ClassConstructorRunner.cs" />
     <Compile Include="System\Runtime\CompilerServices\RuntimeHelpers.NativeAot.cs" />
+    <Compile Include="System\StubHelpers.NativeAot.cs" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetsWindows)'=='true'">
     <Compile Include="$(CommonPath)\Interop\Windows\Kernel32\Interop.ExitProcess.cs">

src/coreclr/nativeaot/System.Private.CoreLib/src/System/StubHelpers.NativeAot.cs

@@ -0,0 +1,10 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.StubHelpers
+{
+    internal static partial class StubHelpers
+    {
+        internal static object? AsyncCallContinuation() => throw new Exception(); // Unconditionally expanded intrinsic
+    }
+}

src/coreclr/tools/Common/TypeSystem/IL/Stubs/AsyncThunks.cs

@@ -1,37 +1,228 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System;
 using Internal.TypeSystem;
 
 namespace Internal.IL.Stubs
 {
     public static class AsyncThunkILEmitter
     {
+        // Emits a thunk that wraps an async method to return a Task or ValueTask.
+        // The thunk calls the async method, and if it completes synchronously,
+        // it returns a completed Task/ValueTask. If the async method suspends,
+        // it calls FinalizeTaskReturningThunk/FinalizeValueTaskReturningThunk method to get the Task/ValueTask.
+
+        // The emitted code matches method EmitTaskReturningThunk in CoreCLR VM.
         public static MethodIL EmitTaskReturningThunk(MethodDesc taskReturningMethod, MethodDesc asyncMethod)
         {
             TypeSystemContext context = taskReturningMethod.Context;
 
             var emitter = new ILEmitter();
             var codestream = emitter.NewCodeStream();
 
-            // TODO: match EmitTaskReturningThunk in CoreCLR VM
+            MethodSignature sig = taskReturningMethod.Signature;
+            TypeDesc returnType = sig.ReturnType;
+
+            bool isValueTask = returnType.IsValueType;
+
+            TypeDesc logicalReturnType = null;
+            ILLocalVariable logicalResultLocal = 0;
+            if (returnType.HasInstantiation)
+            {
+                // The return type is either Task<T> or ValueTask<T>, exactly one generic argument
+                logicalReturnType = returnType.Instantiation[0];
+                logicalResultLocal = emitter.NewLocal(logicalReturnType);
+            }
 
-            MethodSignature sig = asyncMethod.Signature;
-            int numParams = (sig.IsStatic || sig.IsExplicitThis) ? sig.Length : sig.Length + 1;
-            for (int i = 0; i < numParams; i++)
-                codestream.EmitLdArg(i);
+            ILLocalVariable returnTaskLocal = emitter.NewLocal(returnType);
 
-            codestream.Emit(ILOpcode.call, emitter.NewToken(asyncMethod));
+            // TODO: Check if store/restore is responsibility of the async callee
+            // after https://github.com/dotnet/runtime/pull/121448 gets merged.
 
-            if (sig.ReturnType.IsVoid)
+            TypeDesc executionAndSyncBlockStoreType = context.SystemModule.GetKnownType("System.Runtime.CompilerServices"u8, "ExecutionAndSyncBlockStore"u8);
+            ILLocalVariable executionAndSyncBlockStoreLocal = emitter.NewLocal(executionAndSyncBlockStoreType);
+
+            ILCodeLabel returnTaskLabel = emitter.NewCodeLabel();
+            ILCodeLabel suspendedLabel = emitter.NewCodeLabel();
+            ILCodeLabel finishedLabel = emitter.NewCodeLabel();
+
+            codestream.EmitLdLoca(executionAndSyncBlockStoreLocal);
+            codestream.Emit(ILOpcode.call, emitter.NewToken(executionAndSyncBlockStoreType.GetKnownMethod("Push"u8, null)));
+
+            ILExceptionRegionBuilder tryFinallyRegion = emitter.NewFinallyRegion();
             {
-                codestream.Emit(ILOpcode.call, emitter.NewToken(context.SystemModule.GetKnownType("System.Threading.Tasks"u8, "Task"u8).GetKnownMethod("get_CompletedTask"u8, null)));
+                codestream.BeginTry(tryFinallyRegion);
+                codestream.Emit(ILOpcode.nop);
+                ILExceptionRegionBuilder tryCatchRegion = emitter.NewCatchRegion(context.GetWellKnownType(WellKnownType.Object));
+                {
+                    codestream.BeginTry(tryCatchRegion);
+
+                    int localArg = 0;
+                    if (!sig.IsStatic)
+                    {
+                        codestream.EmitLdArg(localArg++);
+                    }
+
+                    for (int iArg = 0; iArg < sig.Length; iArg++)
+                    {
+                        codestream.EmitLdArg(localArg++);
+                    }
+
+                    if (asyncMethod.OwningType.HasInstantiation)
+                    {
+                        var inst = new TypeDesc[asyncMethod.OwningType.Instantiation.Length];
+                        for (int i = 0; i < inst.Length; i++)
+                        {
+                            inst[i] = context.GetSignatureVariable(i, false);
+                        }
+
+                        var instantiatedType = context.GetInstantiatedType((MetadataType)asyncMethod.OwningType, new Instantiation(inst));
+                        asyncMethod = context.GetMethodForInstantiatedType(asyncMethod, instantiatedType);
+                    }
+
+                    if (asyncMethod.HasInstantiation)
+                    {
+                        var inst = new TypeDesc[asyncMethod.Instantiation.Length];
+                        for (int i = 0; i < inst.Length; i++)
+                        {
+                            inst[i] = context.GetSignatureVariable(i, true);
+                        }
+                        asyncMethod = asyncMethod.MakeInstantiatedMethod(new Instantiation(inst));
+                    }
+
+                    codestream.Emit(ILOpcode.call, emitter.NewToken(asyncMethod));
+
+                    if (logicalReturnType != null)
+                    {
+                        codestream.EmitStLoc(logicalResultLocal);
+                    }
+
+                    MethodDesc asyncCallContinuationMd = context.SystemModule
+                                                .GetKnownType("System.StubHelpers"u8, "StubHelpers"u8)
+                                                .GetKnownMethod("AsyncCallContinuation"u8, null);
+
+                    codestream.Emit(ILOpcode.call, emitter.NewToken(asyncCallContinuationMd));
+
+
+                    codestream.Emit(ILOpcode.brfalse, finishedLabel);
+                    codestream.Emit(ILOpcode.leave, suspendedLabel);
+                    codestream.EmitLabel(finishedLabel);
+
+                    if (logicalReturnType != null)
+                    {
+                        codestream.EmitLdLoc(logicalResultLocal);
+
+                        MethodDesc fromResultMethod;
+                        if (isValueTask)
+                        {
+                            fromResultMethod = context.SystemModule
+                                .GetKnownType("System.Threading.Tasks"u8, "ValueTask`1"u8)
+                                .GetKnownMethod("FromResult"u8, null)
+                                .MakeInstantiatedMethod(new Instantiation(logicalReturnType));
+                        }
+                        else
+                        {
+                            fromResultMethod = context.SystemModule
+                                .GetKnownType("System.Threading.Tasks"u8, "Task"u8)
+                                .GetKnownMethod("FromResult"u8, null)
+                                .MakeInstantiatedMethod(new Instantiation(logicalReturnType));
+                        }
+
+                        codestream.Emit(ILOpcode.call, emitter.NewToken(fromResultMethod));
+                    }
+                    else
+                    {
+                        MethodDesc getCompletedTaskMethod;
+                        if (isValueTask)
+                        {
+                            getCompletedTaskMethod = context.SystemModule
+                                .GetKnownType("System.Threading.Tasks"u8, "ValueTask"u8)
+                                .GetKnownMethod("get_CompletedTask"u8, null);
+                        }
+                        else
+                        {
+                            getCompletedTaskMethod = context.SystemModule
+                                .GetKnownType("System.Threading.Tasks"u8, "Task"u8)
+                                .GetKnownMethod("get_CompletedTask"u8, null);
+                        }
+                        codestream.Emit(ILOpcode.call, emitter.NewToken(getCompletedTaskMethod));
+                    }
+
+                    codestream.EmitStLoc(returnTaskLocal);
+                    codestream.Emit(ILOpcode.leave, returnTaskLabel);
+
+                    codestream.EndTry(tryCatchRegion);
+                }
+                // Catch
+                {
+                    codestream.BeginHandler(tryCatchRegion);
+
+                    MethodDesc fromExceptionMd;
+                    if (isValueTask)
+                    {
+                        fromExceptionMd = context.SystemModule
+                            .GetKnownType("System.Threading.Tasks"u8, "ValueTask"u8)
+                            .GetKnownMethod("FromException"u8, null);
+                    }
+                    else
+                    {
+                        fromExceptionMd = context.SystemModule
+                            .GetKnownType("System.Threading.Tasks"u8, "Task"u8)
+                            .GetKnownMethod("FromException"u8, null);
+                    }
+
+                    if (logicalReturnType != null)
+                    {
+                        fromExceptionMd = fromExceptionMd.MakeInstantiatedMethod(new Instantiation(logicalReturnType));
+                    }
+
+                    codestream.Emit(ILOpcode.call, emitter.NewToken(fromExceptionMd));
+                    codestream.EmitStLoc(returnTaskLocal);
+                    codestream.Emit(ILOpcode.leave, returnTaskLabel);
+                    codestream.EndHandler(tryCatchRegion);
+                }
+
+                codestream.EmitLabel(suspendedLabel);
+
+                MethodDesc finalizeTaskReturningThunkMd;
+
+                if (isValueTask)
+                {
+                    finalizeTaskReturningThunkMd = context.SystemModule
+                        .GetKnownType("System.Runtime.CompilerServices"u8, "AsyncHelpers"u8)
+                        .GetKnownMethod("FinalizeValueTaskReturningThunk"u8, null);
+                }
+                else
+                {
+                    finalizeTaskReturningThunkMd = context.SystemModule
+                        .GetKnownType("System.Runtime.CompilerServices"u8, "AsyncHelpers"u8)
+                        .GetKnownMethod("FinalizeTaskReturningThunk"u8, null);
+                }
+
+                if (logicalReturnType != null)
+                {
+                    finalizeTaskReturningThunkMd = finalizeTaskReturningThunkMd.MakeInstantiatedMethod(new Instantiation(logicalReturnType));
+                }
+
+                codestream.Emit(ILOpcode.call, emitter.NewToken(finalizeTaskReturningThunkMd));
+                codestream.EmitStLoc(returnTaskLocal);
+                codestream.Emit(ILOpcode.leave, returnTaskLabel);
+
+                codestream.EndTry(tryFinallyRegion);
             }
-            else
+
             {
-                codestream.Emit(ILOpcode.call, emitter.NewToken(context.SystemModule.GetKnownType("System.Threading.Tasks"u8, "Task"u8).GetKnownMethod("FromResult"u8, null).MakeInstantiatedMethod(sig.ReturnType)));
+                codestream.BeginHandler(tryFinallyRegion);
+
+                codestream.EmitLdLoca(executionAndSyncBlockStoreLocal);
+                codestream.Emit(ILOpcode.call, emitter.NewToken(executionAndSyncBlockStoreType.GetKnownMethod("Pop"u8, null)));
+                codestream.Emit(ILOpcode.endfinally);
+                codestream.EndHandler(tryFinallyRegion);
             }
 
+            codestream.EmitLabel(returnTaskLabel);
+            codestream.EmitLdLoc(returnTaskLocal);
             codestream.Emit(ILOpcode.ret);
 
             return emitter.Link(taskReturningMethod);

src/coreclr/tools/Common/TypeSystem/IL/Stubs/ILEmitter.cs

@@ -517,8 +517,15 @@ public class ILExceptionRegionBuilder
         internal ILCodeStream _endHandlerStream;
         internal int _endHandlerOffset;
 
-        internal ILExceptionRegionBuilder()
+        internal ILExceptionRegionKind _exceptionRegionKind;
+        internal TypeDesc _catchExceptionType;
+
+        internal ILExceptionRegionBuilder(ILExceptionRegionKind exceptionRegionKind, TypeDesc catchExceptionType = null)
         {
+            _exceptionRegionKind = exceptionRegionKind;
+            _catchExceptionType = catchExceptionType;
+            Debug.Assert((exceptionRegionKind == ILExceptionRegionKind.Catch && catchExceptionType != null)
+                || (exceptionRegionKind != ILExceptionRegionKind.Catch && catchExceptionType == null));
         }
 
         internal int TryOffset => _beginTryStream.RelativeToAbsoluteOffset(_beginTryOffset);
@@ -669,7 +676,7 @@ public class ILEmitter
         private ArrayBuilder<ILCodeStream> _codeStreams;
         private ArrayBuilder<LocalVariableDefinition> _locals;
         private ArrayBuilder<object> _tokens;
-        private ArrayBuilder<ILExceptionRegionBuilder> _finallyRegions;
+        private ArrayBuilder<ILExceptionRegionBuilder> _exceptionRegions;
 
         public ILEmitter()
         {
@@ -727,10 +734,18 @@ public ILCodeLabel NewCodeLabel()
             return newLabel;
         }
 
+        // For now, only catches exceptions of type Exception.
+        public ILExceptionRegionBuilder NewCatchRegion(TypeDesc exceptionType)
+        {
+            var region = new ILExceptionRegionBuilder(ILExceptionRegionKind.Catch, exceptionType);
+            _exceptionRegions.Add(region);
+            return region;
+        }
+
         public ILExceptionRegionBuilder NewFinallyRegion()
         {
-            var region = new ILExceptionRegionBuilder();
-            _finallyRegions.Add(region);
+            var region = new ILExceptionRegionBuilder(ILExceptionRegionKind.Finally);
+            _exceptionRegions.Add(region);
             return region;
         }
 
@@ -782,21 +797,34 @@ public MethodIL Link(MethodDesc owningMethod)
 
             ILExceptionRegion[] exceptionRegions = null;
 
-            int numberOfExceptionRegions = _finallyRegions.Count;
+            int numberOfExceptionRegions = _exceptionRegions.Count;
             if (numberOfExceptionRegions > 0)
             {
                 exceptionRegions = new ILExceptionRegion[numberOfExceptionRegions];
-
-                for (int i = 0; i < _finallyRegions.Count; i++)
+                for (int i = 0; i < _exceptionRegions.Count; i++)
                 {
-                    ILExceptionRegionBuilder region = _finallyRegions[i];
+                    ILExceptionRegionBuilder region = _exceptionRegions[i];
 
                     Debug.Assert(region.IsDefined);
 
-                    exceptionRegions[i] = new ILExceptionRegion(ILExceptionRegionKind.Finally,
+                    int exceptionTypeToken = (region._catchExceptionType != null) ? (int)NewToken(region._catchExceptionType) : 0;
+
+                    exceptionRegions[i] = new ILExceptionRegion(region._exceptionRegionKind,
                         region.TryOffset, region.TryLength, region.HandlerOffset, region.HandlerLength,
-                        classToken: 0, filterOffset: 0);
+                        classToken: exceptionTypeToken, filterOffset: 0);
                 }
+
+                // Sort exception regions so that innermost (most nested) regions come first
+                // as this is required by the spec.
+                // Innermost regions have higher TryOffset and smaller TryLength.
+                Array.Sort(exceptionRegions, (a, b) =>
+                {
+                    int offsetComparison = b.TryOffset.CompareTo(a.TryOffset);
+                    if (offsetComparison != 0)
+                        return offsetComparison;
+
+                    return a.TryLength.CompareTo(b.TryLength);
+                });
             }
 
             var result = new ILStubMethodIL(owningMethod, ilInstructions, _locals.ToArray(), _tokens.ToArray(), exceptionRegions, debugInfo);

src/coreclr/vm/asyncthunks.cpp

@@ -58,7 +58,8 @@ bool MethodDesc::TryGenerateAsyncThunk(DynamicResolver** resolver, COR_ILMETHOD_
     return true;
 }
 
-// provided an async method, emits a Task-returning wrapper.
+// Provided an async method, emits a Task-returning wrapper.
+// The emitted code matches method EmitTaskReturningThunk in the Managed Type System.
 void MethodDesc::EmitTaskReturningThunk(MethodDesc* pAsyncOtherVariant, MetaSig& thunkMsig, ILStubLinker* pSL)
 {
     _ASSERTE(!pAsyncOtherVariant->IsAsyncThunkMethod());