[Wasm Ryujit]: implement runtime-async codegen for R2R Wasm by AndyAyersMS · Pull Request #131167 · dotnet/runtime

AndyAyersMS · 2026-07-21T20:28:02Z

Adds Wasm R2R support for runtime-async methods.

The continuation is returned by a Wasm global. The continuation global is referenced through the recently introduced CORINFO_WASM_WELLKNOWN_GLOBALS.
Per-method async resume info is emitted into read-only data. The info Resume field points to code, so is emitted as a relocatable function-table index, requiring a new fixup type (function index in data).
AsyncResumptionStub target calls are routed through MethodEntrypoint on Wasm (no direct code-pointer call exists). We may need to revisit this some day to ensure the right IL version is being invoked.
The async continuation is encoded via a new 'a' signature marker. The interp<->R2R thunks and the delay-load import thunk explicitly forward the continuation as needed. There is perhaps too much ceremony in the code to get correct argument ordering.
The Wasm shadow stack pointer is a caller-established local, not continuation state, so it is excluded from async save/restore in JIT codegen.

Adding a new Wasm global requires creating a new JIT Guid.

Copilot-Session: 760f2e57-f8d3-478b-a9cb-de67d71c9452

Adds Wasm R2R support for runtime-async methods. Key design decisions: * The continuation is returned by a Wasm global. The continuation global is referenced through the newly introduced CORINFO_WASM_WELLKNOWN_GLOBALS. * Per-method async resume info is emitted into read-only data. The info `Resume` field points to code, so is emitted as a relocatable function-table index, requiring a new fixup type (function index in data). * AsyncResumptionStub target calls are routed through MethodEntrypoint on Wasm (no direct code-pointer call exists). We may need to revisit this some day to ensure the right IL version is being invoked. * The async continuation is encoded via a new 'a' signature marker. The interp<->R2R thunks and the delay-load import thunk explicitly forward the continuation as needed. There is perhaps too much ceremony in the code to get correct argument ordering. * The Wasm shadow stack pointer is a caller-established local, not continuation state, so it is excluded from async save/restore in JIT codegen. Adding a new Wasm global requires creating a new JIT Guid. Fixes dotnet#130952. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 760f2e57-f8d3-478b-a9cb-de67d71c9452

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AndyAyersMS · 2026-07-21T20:29:02Z

@davidwrighton PTAL
fyi @dotnet/wasm-contrib @jakobbotsch

Simple R2R'd async test case works on top of interpreted SPC. Haven't tested much else yet.

dotnet-policy-service · 2026-07-21T20:29:34Z

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
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Copilot

Pull request overview

This PR extends the Wasm ReadyToRun (R2R) pipeline to support runtime-async codegen by introducing an asyncContinuation well-known Wasm global, updating signature encoding to include an async marker ('a'), and adding the necessary relocations and thunk plumbing across the JIT/EE/ILCompiler/tooling/host to carry async resume metadata and continuation values.

Changes:

Add an asyncContinuation entry to CORINFO_WASM_WELLKNOWN_GLOBALS and plumb it through the JIT/EE interface, SuperPMI replay, r2rdump, object writer, and the Wasm host (libCorerun.js).
Implement Wasm JIT codegen for async nodes (e.g., GT_ASYNC_CONTINUATION, GT_RETURN_SUSPEND, GT_ASYNC_RESUME_INFO, GT_RECORD_ASYNC_RESUME) and add a Wasm-specific reloc to store function-table indices in data.
Update signature encoding/decoding and R2R thunk generation to recognize/forward the async marker ('a') and adjust interpreter ↔ R2R call boundaries accordingly.

Reviewed changes

Copilot reviewed 39 out of 39 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/tasks/WasmAppBuilder/coreclr/SignatureMapper.cs	Updates signature-token parsing docs to include the new async marker token.
src/tasks/WasmAppBuilder/coreclr/InterpToNativeGenerator.cs	Strips the `'a'` marker when generating interp→native call helper signatures / mappings.
src/coreclr/vm/wasmasynccontinuation.h	Adds Wasm-only C-callable accessors for reading/writing the shared async continuation global.
src/coreclr/vm/wasm/helpers.cpp	Updates interpreter→native invocation to optionally pass/handle an async continuation out parameter.
src/coreclr/vm/prestub.cpp	Writes/reads the async continuation via the shared global on Wasm at interpreter boundaries.
src/coreclr/vm/jitinterface.cpp	Adjusts R2R dynamic info resumption stub entry point resolution for Wasm function-table indices.
src/coreclr/vm/interpexec.cpp	Ensures calli paths only pass the continuation slot to async callees under portable entrypoints.
src/coreclr/tools/superpmi/superpmi-shared/methodcontext.cpp	Records/replays the new `asyncContinuation` well-known global for SuperPMI Wasm contexts.
src/coreclr/tools/superpmi/superpmi-shared/agnostic.h	Extends agnostic Wasm well-known globals struct with `asyncContinuation`.
src/coreclr/tools/r2rdump/WasmDisassembler.cs	Annotates `global.get/set` disassembly with well-known global names including `asyncContinuation`.
src/coreclr/tools/r2rdump/R2RDump.csproj	Links `WasmGlobalImports.cs` into r2rdump for consistent global index naming.
src/coreclr/tools/Common/JitInterface/WasmLowering.cs	Adds `'a'` signature marker emission/parsing for async calls and adjusts roundtrip validation.
src/coreclr/tools/Common/JitInterface/CorInfoTypes.cs	Adds `WASM_TABLE_INDEX_I32` reloc and the `asyncContinuation` well-known global field.
src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs	Plumbs `asyncContinuation` global and maps the new reloc kind into object-writer relocation types.
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs	Improves relocation error messages and centralizes global indices via `WasmGlobalImports`.
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmGlobalImports.cs	New shared constants for imported Wasm global indices (including async continuation).
src/coreclr/tools/Common/Compiler/DependencyAnalysis/WasmWellKnownGlobalSymbolNode.cs	Adds symbol name for `__async_continuation`.
src/coreclr/tools/Common/Compiler/DependencyAnalysis/NodeFactory.Wasm.cs	Adds node factory caching for the new well-known global symbol.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/JitInterface/CorInfoImpl.ReadyToRun.cs	Avoids direct-call optimization for async resumption stubs on Wasm (routes through indirection).
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyToRun.csproj	Links `WasmGlobalImports.cs` into ILCompiler.ReadyToRun.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/WasmR2RToInterpreterThunkNode.cs	Forwards async continuation across R2R→interpreter thunks (including generic-context ordering special-case).
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/WasmInterpreterToR2RThunkNode.cs	Adds async-aware interp→R2R thunk signature and forwards the continuation via the shared global.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/WasmImportThunk.cs	Updates import thunk emission to store/forward the async continuation value as needed.
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/ResumptionStubEntryPointSignature.cs	Emits Wasm-specific relocation for resumption stub entry points (table index in data).
src/coreclr/jit/lowerwasm.cpp	Forces managed calls to be treated as indirect on Wasm (no “in-range” direct-call assumption).
src/coreclr/jit/instrswasm.h	Adds `i32.const_dataoffs` pseudo-instruction for data-section offset constants.
src/coreclr/jit/emitwasm.h	Declares `emitDataOffsetConstant` helper.
src/coreclr/jit/emitwasm.cpp	Implements `emitDataOffsetConstant` and adds `IF_DATAOFFS` emission/output/disasm support.
src/coreclr/jit/emitfmtswasm.h	Adds `IF_DATAOFFS` instruction format.
src/coreclr/jit/emit.cpp	Stores async resume `Resume` as a Wasm table index in data and records `WASM_TABLE_INDEX_I32` relocations.
src/coreclr/jit/codegenwasm.cpp	Implements Wasm codegen for async continuation/global handling and async resume info addressing.
src/coreclr/jit/codegenlinear.cpp	Adjusts Wasm `#ifdef` factoring so async resume recording helpers are available where needed.
src/coreclr/jit/codegencommon.cpp	Clears async continuation (global on Wasm) on normal returns from async methods.
src/coreclr/jit/codegen.h	Adds Wasm-only helpers to store/clear the async continuation global.
src/coreclr/jit/async.cpp	Excludes the Wasm shadow stack pointer local from async save/restore sets.
src/coreclr/inc/jiteeversionguid.h	Bumps the JIT/EE interface GUID due to interface shape changes.
src/coreclr/inc/corinfo.h	Adds new reloc kind and extends `CORINFO_WASM_WELLKNOWN_GLOBALS` with `asyncContinuation`.
src/coreclr/hosts/corerun/wasm/libCorerun.js	Creates/imports a shared `WebAssembly.Global` for async continuation and exposes C-callable accessors.
docs/design/coreclr/botr/readytorun-format.md	Updates docs to reflect `'a'` async continuation marker in Wasm signature strings.

AndyAyersMS · 2026-07-21T23:25:42Z

Going to revise things so the async return global is "owned" by the runtime so hosts don't need to define / export accessors.

Make the runtime-async continuation global owned and exported by the runtime module (an inline-asm wasm global in helpers.cpp) and imported by every webcil, instead of a host-JS-created global with JS accessors. This defines RuntimeAsync_Load/StoreAsyncContinuation in the runtime itself, so browserhost's dotnet.native.wasm links (it was failing with undefined symbols, breaking the browser/wasi CoreCLR CI legs). corerun now wires webcils to wasmExports.__async_continuation. Also addresses PR review: * InvokeCalliStub keeps the 3-arg interpreter cookie and reads the continuation from the shared global after the call, instead of casting to a 4-arg cookie the generated CallFunc helpers never provide. * WasmLowering.RaiseSignature derives the generic-context hidden-pointer char from PointerSize (i32/i64) instead of hard-coding 'i'. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 760f2e57-f8d3-478b-a9cb-de67d71c9452

Copilot

Pull request overview

Copilot reviewed 41 out of 41 changed files in this pull request and generated 6 comments.

The async continuation accessors carry an Object* bit-pattern through an i32 wasm global. Use uint32_t instead of int32_t so the pointer->integer round-trip stays bit-preserving for references with the high bit set (wasm32 memory can exceed 2 GB), avoiding implementation-defined uintptr_t->int32_t conversions. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 760f2e57-f8d3-478b-a9cb-de67d71c9452

Copilot

Pull request overview

Copilot reviewed 41 out of 41 changed files in this pull request and generated 1 comment.

…expand, drop Wasi optimistic-ISA disable Rebased for the v2 cleanup. Keeps runtime-async=on (now unconditional in main + dotnet#131167 provides wasm async R2R codegen), so no async-off gate. corerun.cpp R2R host does NOT define the RuntimeAsync accessors (helpers.cpp from dotnet#131167 now owns __async_continuation + the accessors).

…lobal wiring dotnet#131167 makes the runtime own + export __async_continuation (browser wires it via libCorerun.js). The standalone wasi corerun needs an explicit --export so --gc-sections keeps it and the offline merge can wire each composite's webcil.asyncContinuation import to this same runtime global.

…expand, drop Wasi optimistic-ISA disable Rebased for the v2 cleanup. Keeps runtime-async=on (now unconditional in main + dotnet#131167 provides wasm async R2R codegen), so no async-off gate. corerun.cpp R2R host does NOT define the RuntimeAsync accessors (helpers.cpp from dotnet#131167 now owns __async_continuation + the accessors).

…lobal wiring dotnet#131167 makes the runtime own + export __async_continuation (browser wires it via libCorerun.js). The standalone wasi corerun needs an explicit --export so --gc-sections keeps it and the offline merge can wire each composite's webcil.asyncContinuation import to this same runtime global.

The R2R-to-interpreter thunk re-published the async continuation to the shared global from the transition-block arg slot after the call. On wasm that slot is never updated with the callee's result (the register area is unused; the runtime writes the continuation straight to the global in ExecuteInterpretedMethod), so the thunk overwrote the correct value with the stale inbound arg - breaking suspensions that cross an R2R-to-interpreter async call. Drop the post-call store; the runtime is the authoritative publisher. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 760f2e57-f8d3-478b-a9cb-de67d71c9452

- Instead of embedding a table index in the resume info, use a new R2R fixup to place the right PortableEntryPoint into the location - Tweak InterpreterToR2RThunk generation - Always use the standard MehtodSignature for InterpreterToR2RThunks - Build the ArgIterator based on having an async continuation - Always pass 0 as the async continuation parameter. The only case where a non-zero value is passed is on resumptions, and those always pass through the R2R'd resumption stub, not the interpter to R2R thunk

Fix runtime async on wasm

Copilot

Pull request overview

Copilot reviewed 50 out of 50 changed files in this pull request and generated 2 comments.

# Conflicts: # src/coreclr/inc/jiteeversionguid.h # src/coreclr/inc/readytorun.h # src/coreclr/jit/emitwasm.h # src/coreclr/nativeaot/Runtime/inc/ModuleHeaders.h # src/coreclr/tools/Common/Internal/Runtime/ModuleHeaders.cs

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 760f2e57-f8d3-478b-a9cb-de67d71c9452

Copilot

Pull request overview

Copilot reviewed 51 out of 51 changed files in this pull request and generated 1 comment.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 760f2e57-f8d3-478b-a9cb-de67d71c9452

Copilot

Pull request overview

Copilot reviewed 51 out of 51 changed files in this pull request and generated 3 comments.

davidwrighton

My concerns have been addressed, although I think that @jakobbotsch's comments about making the clr-abi change simpler have merit.

- clr-abi.md: compact wasm continuation-return table row (jakobbotsch) - derive generic-context char from PointerSize for wasm64 (3 thunk nodes) - fix misleading roundtrip assert message and WasmGlobalImports doc reference Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 760f2e57-f8d3-478b-a9cb-de67d71c9452

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 760f2e57-f8d3-478b-a9cb-de67d71c9452

AndyAyersMS · 2026-07-27T21:41:33Z

I have to respin CI for a new Guid, so will fix the doc/comment/diagnostic issues above too.

AndyAyersMS · 2026-07-27T23:14:24Z

@davidwrighton need a re-approval

Copilot

Pull request overview

Copilot reviewed 51 out of 51 changed files in this pull request and generated 2 comments.

AndyAyersMS requested a review from maraf as a code owner July 21, 2026 20:28

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github-actions Bot added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label Jul 21, 2026

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Assertion failed: new_time >= loop->time in Component Governance Detection dotnet/dnceng#6510

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Merge pull request #9 from davidwrighton/wasm-async-fix-runtime-async

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Fix runtime async on wasm

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AndyAyersMS and others added 2 commits July 25, 2026 09:00

Merge remote-tracking branch 'upstream/main' into wasm-async

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# Conflicts: # src/coreclr/inc/jiteeversionguid.h # src/coreclr/inc/readytorun.h # src/coreclr/jit/emitwasm.h # src/coreclr/nativeaot/Runtime/inc/ModuleHeaders.h # src/coreclr/tools/Common/Internal/Runtime/ModuleHeaders.cs

Document the wasm continuation-return ABI in clr-abi.md

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Comment thread src/coreclr/tools/Common/Compiler/ObjectWriter/WasmGlobalImports.cs

Fix JIT formatting

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Unable to pull image from mcr.microsoft.com #117164

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[wasm][RyuJIT] Checked assert 'bbNumTryBeg <= bbNumTryLast' crossgen'ing always-suspending async methods that have a try/fault region #131393

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Merge remote-tracking branch 'upstream/main' into wasm-async

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AndyAyersMS merged commit 35ccab4 into dotnet:main Jul 28, 2026
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[main] Source code updates from dotnet/runtime dotnet/dotnet#8022

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[User Story] RyuJIT for WebAssembly (Wasm) #121141

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