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Make IL Scanner report both variants #128107

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Make IL Scanner report both variants #128107

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32 changes: 28 additions & 4 deletions src/coreclr/tools/aot/ILCompiler.Compiler/IL/ILImporter.Scanner.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -449,6 +449,8 @@ private void ImportCall(ILOpcode opcode, int token)
Debug.Assert(false); break;
}

MethodDesc asyncVariantMethod = null;
MethodDesc asyncVariantRuntimeDeterminedMethod = null;
// Are we scanning a call within a state machine?
if (opcode is ILOpcode.call or ILOpcode.callvirt
&& _canonMethod.IsAsyncCall())
Expand All @@ -475,8 +477,10 @@ private void ImportCall(ILOpcode opcode, int token)
_dependencies.Add(_factory.MethodEntrypoint(asyncHelpers.GetKnownMethod("FinishSuspensionWithContinuationContext"u8, null)), asyncReason);
}

// If this is the task await pattern, we're actually going to call the variant
// so switch our focus to the variant.
// If this is the task await pattern, the JIT will first resolve the call to the
// async variant, then may switch back to the original if the async variant is just
// a thunk (for non-runtime-async methods). Report both variants as dependencies such
// that the JIT can pick either one.
Comment on lines +480 to +483

// in rare cases a method that returns Task is not actually TaskReturning (i.e. returns T).
// we cannot resolve to an Async variant in such case.
Expand All @@ -487,8 +491,8 @@ private void ImportCall(ILOpcode opcode, int token)

if (allowAsyncVariant && MatchTaskAwaitPattern())
{
runtimeDeterminedMethod = _factory.TypeSystemContext.GetAsyncVariantMethod(runtimeDeterminedMethod);
method = _factory.TypeSystemContext.GetAsyncVariantMethod(method);
asyncVariantMethod = _factory.TypeSystemContext.GetAsyncVariantMethod(method);
asyncVariantRuntimeDeterminedMethod = _factory.TypeSystemContext.GetAsyncVariantMethod(runtimeDeterminedMethod);
}
}

Expand Down Expand Up @@ -812,6 +816,16 @@ private void ImportCall(ILOpcode opcode, int token)
}

_dependencies.Add(_factory.CanonicalEntrypoint(targetMethod), reason);

if (asyncVariantMethod != null && _canonMethod.IsSharedByGenericInstantiations)
{
MethodDesc avTargetMethod = asyncVariantMethod.GetCanonMethodTarget(CanonicalFormKind.Specific);
if (avTargetMethod.RequiresInstMethodDescArg())
_dependencies.Add(GetGenericLookupHelper(ReadyToRunHelperId.MethodDictionary, asyncVariantRuntimeDeterminedMethod), reason);
else if (avTargetMethod.RequiresInstMethodTableArg())
_dependencies.Add(GetGenericLookupHelper(ReadyToRunHelperId.TypeHandle, asyncVariantRuntimeDeterminedMethod.OwningType), reason);
Comment on lines +820 to +826
Comment on lines +820 to +826
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@MichalStrehovsky MichalStrehovsky May 13, 2026

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This is going to be really difficult to review for correctness. I wonder if we can instead split ImportCall into two methods:

private void ImportCall(ILOpcode opcode, int token);
private void ImportCall(ILOpcode opcode, MethodDesc method, MethodDesc runtimeDeterminedMethod)

and have the token based ImportCall call the other one, potentially twice.

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@eduardo-vp eduardo-vp May 13, 2026

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Ah yes this is much better, will do

_dependencies.Add(_factory.CanonicalEntrypoint(avTargetMethod), reason);
}
}
else
{
Expand Down Expand Up @@ -853,6 +867,16 @@ private void ImportCall(ILOpcode opcode, int token)
}

_dependencies.Add(GetMethodEntrypoint(targetMethod), reason);

if (asyncVariantMethod != null)
{
MethodDesc avTargetMethod = asyncVariantMethod.GetCanonMethodTarget(CanonicalFormKind.Specific);
if (avTargetMethod.RequiresInstMethodDescArg())
_dependencies.Add(_compilation.NodeFactory.MethodGenericDictionary(asyncVariantMethod), reason);
else if (avTargetMethod.RequiresInstMethodTableArg())
_dependencies.Add(_compilation.NodeFactory.ConstructedTypeSymbol(asyncVariantMethod.OwningType), reason);
_dependencies.Add(GetMethodEntrypoint(avTargetMethod), reason);
}
}
}
else if (staticResolution is DefaultInterfaceMethodResolution.Diamond or DefaultInterfaceMethodResolution.Reabstraction)
Expand Down
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