Add Wasm EH R2R infrastructure by davidwrighton · Pull Request #129197 · dotnet/runtime

davidwrighton · 2026-06-09T22:43:43Z

Note

This PR description was generated by GitHub Copilot.

Summary

Add runtime and JIT support needed for Wasm EH flow in ReadyToRun scenarios
Export/import the RtlRestoreContext exception tag for Wasm modules
Add a Wasm relocation type for referencing the RtlRestoreContext tag

Testing

Verified that finally clauses work
Verified that the body of catch clauses works
Resume after catch is not yet functional and requires additional JIT changes

Notes:
The exception thrown for catch downstream carries with it the "IP" and SP of the context we want to resume to. The JIT team can decide if this is actually useful. Be aware that the "IP" in this case is simply the return value from the catch clause.

- Make STACKWALK_CONTROLPC_ADJUST_OFFSET 2 so that it doesn't break the IsVirtualIP check - Avoid using STACKWALK_CONTROLPC_ADJUST_OFFSET in most cases with virtual ips - Implement EECodeManager::CallFunclet for WASM - Add GetWasmFunctionTableIndexFromVirtualIP for use by CallFunclet - Add exception tag type for RtlRestoreContext to be used during EH flow

…reContextTag into modules

Copilot

Pull request overview

This PR adds WebAssembly ReadyToRun (R2R) exception-handling plumbing across the runtime, toolchain, and hosts by introducing a CoreCLR-specific Wasm exception tag for RtlRestoreContext, wiring it through Webcil import/export, and extending relocation/JIT-interface support so R2R code can reference that tag.

Changes:

Export/import a new Wasm exception tag (__coreclr_wasm_rtlrestorecontext_tag) and plumb it through the JS hosts and build/link flags.
Implement Wasm RtlRestoreContext using a tag throw with (ip, sp) payload, and add Wasm-specific funclet invocation helpers + stackwalk adjustments for virtual IPs.
Add a new Wasm relocation kind to reference the restore-context exception tag in object writing / relocation resolution, and update the JIT-EE interface version.

Reviewed changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/native/corehost/browserhost/CMakeLists.txt	Exports the restore-context tag from the CoreCLR browserhost Wasm module.
src/mono/browser/build/BrowserWasmApp.CoreCLR.targets	Ensures the restore-context tag is exported during app relink.
src/coreclr/vm/wasm/helpers.cpp	Defines/throws the new tag for `RtlRestoreContext`; adds Wasm funclet call helpers via `call_indirect`.
src/coreclr/vm/wasm/cgencpu.h	Adjusts Wasm stackwalk ControlPC adjust offset.
src/coreclr/vm/exceptionhandling.cpp	Skips ControlPC adjustment for Wasm virtual IP frames during EH stack walks.
src/coreclr/vm/eetwain.cpp	Enables invoking Wasm EH funclets via function table indices and Wasm frame pointer recovery.
src/coreclr/vm/codeman.h	Declares a new ExecutionManager mapping from virtual IP to function table index.
src/coreclr/vm/codeman.cpp	Implements virtualIP→functionIndex mapping; decodes Wasm virtual IP encoding for EH clauses.
src/coreclr/tools/Common/JitInterface/CorInfoTypes.cs	Adds a new `CorInfoReloc` value for the Wasm restore-context exception tag.
src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs	Maps the new `CorInfoReloc` to the internal `RelocType`.
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs	Imports the restore-context tag into Webcil modules; resolves the new relocation kind.
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs	Adds tag-import encoding support (`WasmTagImportType`).
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmInstructions.cs	Allows emitting placeholder bytes for the new relocation kind.
src/coreclr/tools/Common/Compiler/DependencyAnalysis/Relocation.cs	Defines/handles the new relocation type for padded ULEB32 write/read/size.
src/coreclr/inc/jiteeversionguid.h	Updates JIT-EE interface version GUID due to interface surface changes.
src/coreclr/inc/corinfo.h	Adds the new relocation kind to the native JIT-EE contract.
src/coreclr/hosts/corerun/wasm/libCorerun.js	Passes the exported tag as a Webcil import; validates it exists post-link.
src/coreclr/hosts/corerun/CMakeLists.txt	Exports the restore-context tag from the corerun Wasm build.
eng/native.wasm.targets	Adds the tag to the exported-symbol preservation list for Wasm builds.

Use the Wasm R2R stack-walk terminator in funclet helpers, clarify the virtual IP parameter name, and skip stack-trace IP adjustment for Wasm virtual IPs. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

AndyAyersMS

I probably shouldn't be the only approver for this, but these changes work well for me in my initial testing.

I have not tried out using the exception tag yet in codegen. Soon.

Copilot

Pull request overview

Copilot reviewed 21 out of 21 changed files in this pull request and generated 3 comments.

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 21 out of 21 changed files in this pull request and generated 3 comments.

adamperlin

Overall lgtm, but I just had some suggestions about comments

davidwrighton · 2026-06-11T21:38:15Z

/ba-g only interesting test failures are #129242

… wasm_eh_infra

Copilot

Pull request overview

Copilot reviewed 21 out of 21 changed files in this pull request and generated 2 comments.

davidwrighton · 2026-06-13T20:39:01Z

/ba-g known infra problems

dotnet-policy-service · 2026-06-16T06:59:22Z

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

> [!NOTE] > This PR description was generated by GitHub Copilot. ## Summary - Add runtime and JIT support needed for Wasm EH flow in ReadyToRun scenarios - Export/import the `RtlRestoreContext` exception tag for Wasm modules - Add a Wasm relocation type for referencing the `RtlRestoreContext` tag ## Testing - Verified that finally clauses work - Verified that the body of catch clauses works - Resume after catch is not yet functional and requires additional JIT changes Notes: The exception thrown for catch downstream carries with it the "IP" and SP of the context we want to resume to. The JIT team can decide if this is actually useful. Be aware that the "IP" in this case is simply the return value from the catch clause. --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

davidwrighton added 3 commits June 9, 2026 14:59

Export __coreclr_wasm_rtlrestorecontext_tag and import it as rtlResto…
5c9d23f
…reContextTag into modules

Add new relocation type to refer to the RtlRestoreContext tag
5b1bcc9

CopilotAI review requested due to automatic review settings June 9, 2026 22:43

davidwrighton requested review from MichalStrehovsky, akoeplinger and maraf as code owners June 9, 2026 22:43

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github-actionsBot added the area-VM-coreclr label Jun 9, 2026

davidwrighton requested a review from AndyAyersMS June 9, 2026 22:45

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Comment threadsrc/coreclr/vm/wasm/helpers.cpp
Comment threadsrc/coreclr/vm/wasm/helpers.cpp
Comment threadsrc/coreclr/vm/codeman.h Outdated
Comment threadsrc/coreclr/vm/exceptionhandling.cpp
Comment threadsrc/coreclr/vm/codeman.cpp

Address Wasm EH review feedback
d62743a
Use the Wasm R2R stack-walk terminator in funclet helpers, clarify the virtual IP parameter name, and skip stack-trace IP adjustment for Wasm virtual IPs. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

AndyAyersMS mentioned this pull request Jun 10, 2026
[Wasm RyuJit]: don't skip top-level catchrets when marking try resumption #129205
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AndyAyersMS approved these changes Jun 10, 2026
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Merge branch 'main' into wasm_eh_infra
0a7a51c

CopilotAI review requested due to automatic review settings June 10, 2026 23:46

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Comment threadsrc/coreclr/inc/jiteeversionguid.h Outdated
Comment threadsrc/coreclr/vm/eventtrace.cpp
Comment threadsrc/coreclr/vm/eetwain.cpp

Potential fix for pull request finding
6729a3f
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

CopilotAI review requested due to automatic review settings June 11, 2026 00:08

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Comment threadsrc/coreclr/vm/eventtrace.cpp
Comment threadsrc/coreclr/vm/codeman.cpp
Comment threadsrc/coreclr/vm/wasm/helpers.cpp

adamperlin reviewed Jun 11, 2026
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs

build-analysisBot mentioned this pull request Jun 11, 2026
Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. dotnet/dnceng#5922
Open
3 tasks

adamperlin reviewed Jun 11, 2026
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Comment threadsrc/coreclr/vm/wasm/helpers.cpp Outdated

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Comment threadsrc/coreclr/vm/wasm/helpers.cpp Outdated

adamperlin reviewed Jun 11, 2026
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Comment threadsrc/coreclr/vm/wasm/helpers.cpp

adamperlin approved these changes Jun 11, 2026
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davidwrighton added 2 commits June 11, 2026 14:48

Comments adjusted per code review
ecdb0de

Merge branch 'wasm_eh_infra' of github.com:davidwrighton/runtime into…
3c2d674
… wasm_eh_infra

This was referenced Jun 12, 2026
Wasm / R2R: conv_ovf_i8_i aborts at runtime (try / catch [OverflowException] around conv.ovf.i) #129337
Closed
Wasm / R2R: IsFilterFunclet assertion fires when re-throwing from a finally after a cctor failure (throwinclassconstructor) #129341
Closed

Merge branch 'main' into wasm_eh_infra
44a7ce0

CopilotAI review requested due to automatic review settings June 13, 2026 12:39

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Comment threadsrc/coreclr/vm/eventtrace.cpp
Comment threadsrc/coreclr/vm/wasm/helpers.cpp

build-analysisBot mentioned this pull request Jun 13, 2026
Multiple Helix work items fail on maccatalyst/tvos CoreCLR Release #126460
Closed

davidwrighton merged commit f363796 into dotnet:mainJun 13, 2026
174 of 183 checks passed

dotnet-maestroBot mentioned this pull request Jun 14, 2026
[main] Source code updates from dotnet/runtime dotnet/dotnet#7196
Merged

pavelsavara added the arch-wasm WebAssembly architecture label Jun 16, 2026

dotnet-milestone-botBot added this to the 11.0-preview6 milestone Jun 17, 2026

AndyAyersMS mentioned this pull request Jun 19, 2026
[Wasm RyuJIT] Basic Control Flow #121178
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