Assert failure: Compiler optimization assumption invalid: FAILED: pMgr != 0 #70259

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1. BruceForstall

   added

   area-CodeGen-coreclrCLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMICLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI

   blocking-clean-ci-optionalBlocking optional rolling runsBlocking optional rolling runs

   on Jun 5, 2022
2. BruceForstall

   added this to the 7.0.0 milestone on Jun 5, 2022
4. jkotas commented on Jun 5, 2022

   

   jkotas

   on Jun 5, 2022

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   This looks like JIT stress issue. JIT stress converted delegate call to tailcall. This conversion is not valid when the delegate points to virtual interface method.
5. BruceForstall commented on Jun 5, 2022

   

   BruceForstall

   on Jun 5, 2022

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   @jakobbotsch Related to #69941? #70033?
6. jakobbotsch commented on Jun 5, 2022

   

   jakobbotsch

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   Probably #70033, though it is curious that this seemingly used to work. Maybe something rotted in the period that the JIT helper was not being used.
7. jakobbotsch

   self-assigned this

   on Jun 5, 2022
8. jakobbotsch commented on Jun 5, 2022

   

   jakobbotsch

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   @jkotas

   This looks like JIT stress issue. JIT stress converted delegate call to tailcall. This conversion is not valid when the delegate points to virtual interface method.

   What exactly do you mean by virtual interface method here? Do you mean any call that may go through VSD?
9. jkotas commented on Jun 5, 2022

   

   jkotas

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   Here is what is happening based on the crash dump:

   // This delegate points to shuffle thunk that in turn points to VSD stub
   // The VSD stub expects the callsite to be VSD DelegateCallSite.
   var d = typeof(IFace).GetMethod("Method").CreateDelegate<Action<IFace>>();
   
   var c = new ClassA();
   
   // JIT stress converted this to tailcall. The callsite is not identified as 
   // DelegateCallSite anymore and that's why we get the assert.
   d(c); 
   
   public class ClassA : IFace
   {
       public virtual void Method() { Console.WriteLine("Method"); }
   }
   
   public interface IFace
   {
       public void Method();
   }
   

   it is curious that this seemingly used to work.

   These delegates pointing to VSD stubs are very rare. It is quite possible that it was broken for a long time and we just got lucky that the JIT stress did not hit it before.
10. jakobbotsch commented on Jun 5, 2022

    

    jakobbotsch

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    These delegates pointing to VSD stubs are very rare. It is quite possible that it was broken for a long time and we just got lucky that the JIT stress did not hit it before.

    I see, thanks for the example. In practice does this mean that tail prefixed delegate calls cannot be done through the old mechanism?
11. jkotas commented on Jun 5, 2022

    

    jkotas

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    Right.

    It may be possible to fix up the x86 JIT_TailCall helper to handle this case, but I do not think that it is worth it.

    👍React with 👍1Reacted by Jakob Botsch Nielsen
12. jakobbotsch commented on Jun 5, 2022

    

    jakobbotsch

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    The other half of why we may not have seen this before is that isCallRelativeIndirect inside StubCallSite::StubCallSite needs to pass, i.e. the tailcaller's caller need to be on the form call [rel32]. If that check does not pass the VSD resolver properly sees the call as a delegate call.
13. jakobbotsch

    added a commit that references this issue on Jun 5, 2022

    Always use portable tailcalling mechanism for delegate tailcalls

    ...

    This issue will close once commit 77a4450 is merged into the 'main' branch.

    77a4450
14. ghost added

    in-prThere is an active PR which will close this issue when it is mergedThere is an active PR which will close this issue when it is merged

    on Jun 5, 2022
15. BruceForstall

    closed this as completedin #70269on Jun 7, 2022
16. BruceForstall

    added a commit that references this issue on Jun 7, 2022

    Always use portable tailcalling mechanism for delegate tailcalls (#70269

    ...

    This issue will close once commit caff7b0 is merged into the 'main' branch.

    caff7b0
17. ghost removed

    in-prThere is an active PR which will close this issue when it is mergedThere is an active PR which will close this issue when it is merged

    on Jun 7, 2022
18. ghost locked as resolved and limited conversation to collaborators on Jul 7, 2022