Wasm: Runtime_79354 fails with test assembly R2R

[AndyAyersMS]

Description

On wasm (FEATURE_PORTABLE_ENTRYPOINTS + cached interface dispatch), invoking an open virtual/interface delegate from ReadyToRun-compiled code asserts in the interpreter:

Assert failure: portableEntryPoint->IsValid()
  src/coreclr/vm/precode_portable.cpp:109  ToPortableEntryPoint
  Frame (InterpreterFrame): MyDelegate::IL_STUB_DelegateShuffleThunk, IR_0014

Found while ReadyToRun-compiling and running the src/tests/JIT tree on wasm. The failing case is src/tests/JIT/Regression/JitBlue/Runtime_79354/Runtime_79354.cs — an open-instance delegate over an interface method (IGetContents.GetContents()), created via MethodInfo.CreateDelegate. IL/interpreter execution passes; only R2R fails.

Root cause

For an open virtual/interface delegate, COMDelegate sets _methodPtrAux = GetVirtualCallStub(...), which under cached interface dispatch is (PCODE)CID_VirtualOpenDelegateDispatch — a native helper, not a portable entry point (comdelegate.cpp:1201, :961).

The delegate's _methodPtr is the IL shuffle thunk (CreateILDelegateShuffleThunk), which does LDFLD _methodPtrAux; calli (comdelegate.cpp:853-854). On wasm the shuffle thunk runs interpreted.

The interpreter's INTOP_CALLDELEGATE path already handles the open-virtual case (detects the CID_VirtualOpenDelegateDispatch / VSD marker and resolves the real target — interpexec.cpp:3422-3448). But that path is bypassed when the delegate is invoked from R2R-compiled code, which calls the shuffle thunk directly. The shuffle thunk's own calli then reaches INTOP_CALLI, which does PortableEntryPoint::GetMethodDesc(calliFunctionPointer) (interpexec.cpp:3326) on the native CID_VirtualOpenDelegateDispatch helper -> ToPortableEntryPoint -> IsValid() assert.

In a release build this is not a checked assert, but the calli target is still not a valid portable entry point, so the dispatch is incorrect.

Repro (wasm R2R)

1. Build clr+libs -os browser (Checked).
2. ReadyToRun-compile Runtime_79354.dll (crossgen2, --targetarch:wasm --targetos:browser) and run under corerun.js with the R2R companion enabled (PLATFORM_NATIVE_R2R=1, APP_ASSEMBLIES=EXTERNAL).

Minimal shape:

public interface IGetContents { (string, int, string) GetContents(); }
public struct MyStruct : IGetContents { /* ... */ public (string,int,string) GetContents() => (s1, a, s2); }
public delegate (string, int, string) MyDelegate(IGetContents arg);

var mi = typeof(IGetContents).GetMethod("GetContents");
var func = (MyDelegate)mi.CreateDelegate(typeof(MyDelegate));  // open delegate over interface method
var r = func(new MyStruct { /* ... */ });                     // asserts under wasm R2R

Suggested fix

Teach the interpreter's INTOP_CALLI (portable-entrypoints path) to recognize the open-virtual dispatch marker — calliFunctionPointer == CID_VirtualOpenDelegateDispatch (cached dispatch) or VirtualCallStubManager::isStubStatic(...) (VSD) — before treating the target as a portable entry point, and resolve the real target the same way INTOP_CALLDELEGATE does (from the shuffle-thunk delegate this + receiver). A working prototype exists.

Notes

• Area: wasm interpreter / R2R (portable entry points).

Note

This issue was drafted with GitHub Copilot.

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