[wasm][R2R] Root interpreter thunks for closed static delegate targets by pavelsavara · Pull Request #134497 · dotnet/runtime

pavelsavara · 2026-09-23T07:12:24Z

Summary

Root the R2R-to-interpreter thunk needed when a Wasm delegate invocation reaches a closed static target, including a runtime-generated expression or dynamic call-site target.

The delegate call site has an instance signature, while the closed static target takes the bound object as an explicit first parameter. These can have identical physical Wasm parameter types but different interpreter thunk keys. For example, the caller can root IiTiiS4p while the dynamic target requires IiiiiS4p. When the latter is absent, entry-point preparation leaves the code field null and the R2R delegate invocation traps.

Changes

Construct the closed static target as a MethodSignature, prepending the bound object and using normal Wasm lowering rather than rewriting signature strings.
Root the corresponding interpreter thunk specifically when resolving Wasm delegate Invoke calls.
Add ten compiler layout cases covering nullable structs, return buffers, generic-context arguments, and async-continuation arguments.
Add a three-case runtime regression for a compiled expression capturing state and accepting a nullable argument, with static and generic-instance delegate controls.

No VM dispatch changes, diagnostic probes, or experimental switches are included.

Validation

On this branch, based directly on upstream main at 206bf81aa71b157cb03ae7ed1a42d1ed7d3aa2dc:

Compiler build and WasmArgumentLayoutTests: 77 passed, zero failures or skipped tests.
Patch whitespace checks passed.

Before transferring the same four-file patch from the investigation branch, using browser CoreCLR Release with trimming and R2R:

Full Microsoft.CSharp.Tests: 4,805 passed, zero failures or skipped tests, after removing diagnostics and rebuilding native/runtime-loader artifacts.
DynamicMethodCreateDelegateTests: 14 passed.
Negative control: disabling only the new thunk dependency makes the new nullable-expression regression request missing IiiS4p and trap; enabling it passes.
Generated and deployed test-image SHA-256 hashes matched.
A matched 39-image test-closure comparison measured an additional 31,368 bytes (0.0715%) of R2R output.

The complete browser runtime suite has not been rerun against a freshly rebuilt main-based runtime; this remains a draft. The broader expression LambdaTests slice also exposed an interpreter memory-access failure in InvokeComputedLambda, reproduced with the new dependency disabled at the same native instruction, and is not addressed here.

Scope

This is complementary to #134108, which supplies the closed static delegate return-buffer adapter. This PR supplies missing target thunk coverage, including scalar-returning targets; it does not implement that adapter.

Found while investigating #134200. That issue describes a broader startup failure, so this PR does not claim to resolve it in full.

Note

This pull request was prepared with GitHub Copilot assistance.

azure-pipelines · 2026-09-23T07:13:10Z

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dotnet-policy-service · 2026-09-23T07:13:42Z

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dotnet-policy-service · 2026-09-23T07:18:20Z

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
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Copilot

Copilot review overview

🟡 Changes recommended

The closed-static signature construction drops non-Static flags, which can leave required thunks unrooted.

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Review effort: Lite
Findings: 1

Open (1)

Preserve Invoke signature flags in fallback thunk · New

What changed in this PR

Fixes missing WebAssembly R2R interpreter thunks for closed static delegate targets and adds regression coverage.

Changes:

Constructs lowered closed-static delegate signatures.
Roots matching interpreter thunks during delegate invocation.
Adds compiler layout and nullable-expression regression tests.

File	Summary
`src/libraries/tests.proj`	Re-enables Microsoft.CSharp tests for Wasm R2R.
`src/libraries/Microsoft.CSharp/tests/DelegateInDynamicTests.cs`	Adds nullable closed-static delegate regression coverage.
`src/coreclr/tools/Common/JitInterface/WasmLowering.cs`	Builds closed-static delegate signatures; must preserve all original signature flags.
`src/coreclr/tools/aot/ILCompiler.ReadyToRun/JitInterface/CorInfoImpl.ReadyToRun.cs`	Roots the required interpreter thunk.
`src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/WasmArgumentLayoutTests.cs`	Tests ABI layouts and hidden arguments.

Build the target signature with the delegate Invoke flags, and cover default, varargs, and unmanaged calling conventions with a regression test. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: bd5418a9-09c6-4017-a1e1-edb2cf396b39

Copilot

Copilot review overview

🟡 Changes recommended

Fix hidden-argument flag handling and retain or narrow the test exclusion for the known dispatch failure.

Get a fresh assessment by requesting another Copilot review.

Review effort: Lite
Findings: 1

Open (1)

Use resolved call signature for hidden-argument lowering flags · New

Resolved since last review (1)

Preserve Invoke signature flags in fallback thunk

Source the interpreter-thunk lowering flags from the resolved call signature instead of the delegate Invoke MethodDesc, so a shared generic delegate's generic-context hidden argument is reflected, and skip unmanaged calls to match the other call-signature recording paths.

Copilot

Copilot review overview

🔵 Needs a closer look

Full runtime validation remains incomplete, with a broader expression test failure still outside this change.

Review effort: Lite
Findings: None

Resolved since last review (1)

Use resolved call signature for hidden-argument lowering flags

Delegate Invoke cannot be unmanaged, so assert the invariant and root the closed-static interpreter thunk unconditionally. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot review overview

🟡 Changes recommended

Address the three unresolved moderate findings before approval.

Get a fresh assessment by requesting another Copilot review.

Review effort: Lite
Findings: 1

Open (1)

Guard thunk dependency for unmanaged calling conventions · New

pavelsavara · 2026-09-25T09:10:43Z

/ba-g unrelated CI issues

Consume GetClosedStaticDelegateTargetSignature from dotnet#134497 for the closed-static retbuf thunk dependency, removing the duplicate signature construction. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: bd5418a9-09c6-4017-a1e1-edb2cf396b39

[wasm][R2R] Root interpreter thunks for closed static delegate targets

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github-actions Bot added the area-ReadyToRun label Sep 23, 2026

dotnet-policy-service Bot assigned pavelsavara Sep 23, 2026

pavelsavara added the arch-wasm WebAssembly architecture label Sep 23, 2026

pavelsavara requested review from davidwrighton and lewing September 23, 2026 07:18

pavelsavara added this to the 12.0.0 milestone Sep 23, 2026

[wasm][R2R] Re-enable Microsoft.CSharp library tests

d5f2f23

pavelsavara marked this pull request as ready for review September 23, 2026 15:06

Copilot AI lite review requested due to automatic review settings September 23, 2026 15:06

pavelsavara requested a review from MichalStrehovsky as a code owner September 23, 2026 15:06

Copilot started reviewing on behalf of pavelsavara September 23, 2026 15:06 View session

Copilot AI reviewed Sep 23, 2026

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Comment thread src/coreclr/tools/Common/JitInterface/WasmLowering.cs Outdated

lewing mentioned this pull request Sep 23, 2026

[wasm][R2R] Fix closed static delegate struct returns #134108

Merged

build-analysis Bot mentioned this pull request Sep 23, 2026

System.Security.Cryptography.Tests.HpkeImplementationTests.InvalidEncapsulation_Rejected fails in CI #134528

Open

Copilot AI review requested due to automatic review settings September 24, 2026 00:13

Copilot started reviewing on behalf of pavelsavara September 24, 2026 00:13 View session

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Comment thread src/coreclr/tools/aot/ILCompiler.ReadyToRun/JitInterface/CorInfoImpl.ReadyToRun.cs Outdated

lewing mentioned this pull request Sep 24, 2026

[wasm][coreclr][R2R] Delegate construction skips alternate-constructor lowering and remains interpreted #134564

Open

build-analysis Bot mentioned this pull request Sep 24, 2026

HttpWebRequestTest_Async.SendHttpRequest_BindIPEndPoint_Success failure from too many BindIPEndPointDelegate retries #131951

Open

pavelsavara added 2 commits September 24, 2026 09:51

Merge branch 'main' into wasm_r2r_closed_static_delegate_thunks

f487c8b

Copilot AI review requested due to automatic review settings September 24, 2026 08:00

Copilot started reviewing on behalf of pavelsavara September 24, 2026 08:00 View session

Copilot AI reviewed Sep 24, 2026

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This was referenced Sep 24, 2026

System.Net.Quic.QuicException : Connection handshake was canceled due to the configured timeout #133645

Open

[ci-scan] Test failure: Runtime_133207 asserts in ValidateInner on browser WASM R2R #133991

Open

jkotas reviewed Sep 24, 2026

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Comment thread src/coreclr/tools/aot/ILCompiler.ReadyToRun/JitInterface/CorInfoImpl.ReadyToRun.cs Outdated

Assert delegate Invoke uses managed calling convention

f1a20ce

Delegate Invoke cannot be unmanaged, so assert the invariant and root the closed-static interpreter thunk unconditionally. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot AI review requested due to automatic review settings September 24, 2026 16:47

Copilot started reviewing on behalf of pavelsavara September 24, 2026 16:48 View session

Copilot AI reviewed Sep 24, 2026

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Comment thread src/coreclr/tools/aot/ILCompiler.ReadyToRun/JitInterface/CorInfoImpl.ReadyToRun.cs

lewing mentioned this pull request Sep 24, 2026

[wasm][R2R] Call delegate construction helpers directly #134611

Draft

build-analysis Bot mentioned this pull request Sep 24, 2026

Async2TaskAdapters.TestValueTaskOfTaskValueVersusAsync fails with SanityCheck() in Wasm R2R test #133953

Open

pavelsavara enabled auto-merge (squash) September 25, 2026 09:10

lewing approved these changes Sep 25, 2026

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pavelsavara merged commit 6727c91 into dotnet:main Sep 25, 2026
132 of 134 checks passed

pavelsavara deleted the wasm_r2r_closed_static_delegate_thunks branch September 25, 2026 16:07

dotnet-maestro Bot mentioned this pull request Sep 26, 2026

[main] Source code updates from dotnet/runtime dotnet/dotnet#9783

Merged

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[wasm][R2R] Root interpreter thunks for closed static delegate targets - #134497

[wasm][R2R] Root interpreter thunks for closed static delegate targets#134497
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pavelsavara:wasm_r2r_closed_static_delegate_thunks

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pavelsavara commented Sep 23, 2026

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