Fix wasm EH resume for handlers nested inside VM-invoked funclets

[davidwrighton]

Summary

Fixes wasm exception-handling resume for a handler that is lexically nested inside a funclet (e.g. a catch inside a finally) when the runtime is R2R-compiled and the funclet was invoked by the VM via EECodeManager::CallFunclet.

This PR contains three commits:

1. Fix wasm EH resume for handlers nested inside funclets (@AndyAyersMS) — cherry-picked from fix-wasm-funclet-eh-resume. When invoking a funclet whose handler is lexically nested inside another funclet, it natively unwinds out of the funclet frames to recover the enclosing method's establishing frame.

2. Add EH test interleaving interpreter and R2R funclets — a Methodical EH test (InterpR2RFunclets) that throws out of an interpreted method (forced via a test-local BypassReadyToRun attribute) and unwinds through compiled funclets, including a finally funclet that itself catches an exception thrown by interpreted code. Registered in the eh-bearing merged variants (_d1, _do, _r1, _ro).

3. Fix wasm funclet establishing frame for handlers nested in VM-invoked funclets — corrects a defect in commit 1.

The defect being fixed

There are two ways a funclet can be reached:

• Inline within the method's own native frame — Andy's native unwind loop correctly lands on the method frame and GetWasmFramePointerFromStackPointer yields the right establishing frame.
• Via CallFuncletWith[out]Throwable — these helpers push a synthetic 16-byte frame marked with TERMINATE_R2R_STACK_WALK. Native unwinding terminates at that synthetic frame (EECodeInfo::IsValid() becomes false) before reaching the method frame, so calling GetWasmFramePointerFromStackPointer on that SP produces a bogus establishing frame.

The fix

• CallFuncletWith[out]Throwable now store the establishing (method) frame pointer immediately after the TERMINATE_R2R_STACK_WALK marker (at TERMINATE_R2R_STACK_WALK_FP_OFFSET).
• When the unwind loop lands on the terminator (!ci.IsValid()), the establishing frame is recovered via the new GetWasmEstablishingFramePointerFromTerminator helper instead of GetWasmFramePointerFromStackPointer. The inline case (ci.IsValid() && !ci.IsFunclet()) keeps the original behavior.

Validation

Verified on the standalone form of the test under wasm R2R (crossgen2):

Mode	Before fix	After fix
R2R (crossgen2)	Actual: 1 (unhandled exception escapes)	Actual: 100 (PASS)
Interpreted	Actual: 100	Actual: 100 (PASS)

A temporary printf confirmed the new GetWasmEstablishingFramePointerFromTerminator code path is the one exercised by the nested-funclet scenario.

Known limitation

The test is included in the merged Methodical assemblies rather than as a process-isolation test (merged tests are generally preferred). Crossgen2 currently emits an invalid R2R wasm image for the merged Methodical assembly due to an unrelated codegen issue, so under R2R the merged image is discarded and the assembly runs interpreted — meaning the merged test does not yet exercise the R2R funclet path. That unrelated invalid-R2R-method issue will be addressed separately; the standalone validation above confirms the fix.

Note

This pull request was authored with assistance from GitHub Copilot.

[Copilot]

Pull request overview

This PR fixes WebAssembly exception-handling resume when an EH handler is lexically nested inside a VM-invoked funclet (e.g., catch inside a finally) by ensuring the correct establishing (method) frame pointer is available when native unwinding terminates at a synthetic “terminate R2R stack walk” marker frame.

Changes:

• Persist the establishing frame pointer in the synthetic terminator frame created by CallFuncletWith[out]Throwable, and add a helper to recover it.
• Update EECodeManager::CallFunclet (wasm) to unwind out of nested funclet frames and choose the right establishing frame source depending on whether unwinding ends at the terminator or reaches the method frame.
• Add a Methodical EH test (InterpR2RFunclets) and register it in merged Methodical variants.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/coreclr/vm/wasm/helpers.cpp	Stores establishing FP next to TERMINATE_R2R_STACK_WALK and adds GetWasmEstablishingFramePointerFromTerminator.
src/coreclr/vm/wasm/callhelpers.hpp	Defines TERMINATE_R2R_STACK_WALK_FP_OFFSET and documents the synthetic frame layout.
src/coreclr/vm/eetwain.cpp	Adjusts wasm EECodeManager::CallFunclet establishing-frame selection for handlers nested in funclets.
src/tests/JIT/Methodical/eh/interp/interpr2rfunclets.cs	Adds EH test interleaving interpreted throws with compiled funclets and nested handler behavior.
src/tests/JIT/Methodical/Methodical_ro.csproj	Includes the new Methodical test in the _ro merged variant.
src/tests/JIT/Methodical/Methodical_r1.csproj	Includes the new Methodical test in the _r1 merged variant.
src/tests/JIT/Methodical/Methodical_do.csproj	Includes the new Methodical test in the _do merged variant.
src/tests/JIT/Methodical/Methodical_d1.csproj	Includes the new Methodical test in the _d1 merged variant.

[AndyAyersMS]

LGTM, just wondering if there are cases where finding the method frame might be more involved...

[davidwrighton]

/ba-g unrelated infra failures.

[dotnet-policy-service]

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
See info in area-owners.md if you want to be subscribed.