Fix DAC GetNativeCodeInfo API to use async variant for thunk MethodDescs

[tommcdon]

Regressed by #125900 from #124354

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[Copilot]

Pull request overview

Adjusts DAC GetNativeCodeInfo to resolve async thunk MethodDescs to the correct associated implementation MethodDesc by selecting the async variant, addressing a regression introduced by changes to async thunking.

Changes:

• Update DacDbiInterfaceImpl::GetNativeCodeInfo to use GetAsyncVariantNoCreate() when the resolved MethodDesc is an async thunk.
• Ensure native code region/EnC info is reported for the async implementation rather than the thunk.

[max-charlamb]

Should we always try to get the non-thunk variant? Regardless of if it is async or ordinary?

[tommcdon]

Should we always try to get the non-thunk variant? Regardless of if it is async or ordinary?

For runtime async methods, I believe FindLoadedMethodRefOrDef always resolves to an async thunk method. So if the method is identified as "async", my guess is that we need to resolve it to the async variant.

[noahfalk]

Suggested change

	MethodDesc* pAsyncVariant = pMethodDesc->GetAsyncVariantNoCreate();
	MethodDesc* pAsyncVariant = pMethodDesc->GetAsyncOtherVariantNoCreate();

I think this is a little more general. The current code probably works too but this one doesn't require assumptions about which variant we will get from FindLoadedMethodRefOrDef in the ordinary case.

[max-charlamb]

I think this is a little more general. The current code probably works too but this one doesn't require assumptions about which variant we will get from FindLoadedMethodRefOrDef in the ordinary case.

I agree, we want this logic, but that exact method was removed recently (#125900).

[noahfalk]

oh hah... I need to catch up it appears ;p

[max-charlamb]

Should we always try to get the non-thunk variant? Regardless of if it is async or ordinary?

For runtime async methods, I believe FindLoadedMethodRefOrDef always resolves to an async thunk method. So if the method is identified as "async", my guess is that we need to resolve it to the async variant.

Okay, that seems reasonable. FindLoadedMethodRefOrDef should always return the ordinary variant given this check when adding method defs to the m_MethodDefToDescMap

 if (!pMD->IsUnboxingStub() && !pMD->IsAsyncVariantMethod())
 {
     pModule->EnsuredStoreMethodDef(pMD->GetMemberDef(), pMD);
 }

(line 2807-2809 in clsload.cpp)

This should mean that if we get into the pMethodDesc->IsAsyncThunkMethod() check, it implies that we have an ordinary thunk and getting the async method will be the true body. I am a little concerned this falls apart with EnC given that registers the methods to the map without the above check.