Implement wasm JumpStubNode with signature-matched argument forwarding by Copilot · Pull Request #133248 · dotnet/runtime

Copilot · 2026-09-04T16:51:06Z

Implements JumpStubNode for Wasm so address-taken method stubs no longer throw NotImplementedException during emission. The stub now preserves the target method’s lowered Wasm signature, forwards all arguments, and transfers control to the target.

Wasm JumpStub emission
- Replaces the Wasm JumpStubNode.EmitCode stub implementation with real body generation.
- Computes the lowered Wasm function type from INodeWithTypeSignature.
- Emits local.get for each parameter and calls the target symbol.
Signature propagation for address-taken methods
- Updates AddressTakenMethodNode to implement IMethodCodeNodeWithTypeSignature.
- Ensures Wasm method declaration/signature recording uses the target method signature for emitted jump stubs.

for(inti=0;i<signature.Params.Types.Length;i++){expressions.Add(Local.Get(i));}expressions.Add(ControlFlow.Call(_target));encoder.FunctionBody=newWasmFunctionBody(signature,expressions.ToArray());

FixesImplement JumpStubNode for WASM #133247

azure-pipelines · 2026-09-04T16:51:23Z

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Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

azure-pipelines · 2026-09-04T18:15:08Z

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dotnet-policy-service · 2026-09-04T18:15:42Z

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
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dotnet-policy-service · 2026-09-04T18:16:21Z

Tagging subscribers to this area: @agocke, @dotnet/ilc-contrib
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Copilot

🟡 Changes recommended

The new Wasm stub uses return_call (tail-call proposal opcode), which can break compatibility on runtimes that don’t enable tail calls.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR adds a real Wasm implementation of JumpStubNode so address-taken method stubs can be emitted with a signature that matches the target method, forwarding all lowered Wasm arguments and transferring control to the target.

Changes:

Add a new Wasm instruction kind and helper for return_call.
Implement JumpStubNode.EmitCode for Wasm by computing the lowered WasmFuncType, emitting local.get for each parameter, and invoking the target.
Update AddressTakenMethodNode to implement IMethodCodeNodeWithTypeSignature so signature metadata can flow through for Wasm emission.

File summaries

File	Description
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmInstructions.cs	Adds `ReturnCall` opcode support and a `ControlFlow.ReturnCall` helper.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/Target_Wasm/WasmJumpStubNode.cs	Implements Wasm `JumpStubNode` emission with signature-based argument forwarding and target invocation.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/AddressTakenMethodNode.cs	Switches to `IMethodCodeNodeWithTypeSignature` to propagate method signature info for Wasm stub emission.

Review details

Files reviewed: 3/3 changed files
Comments generated: 1
Review effort level: Lite

jtschuster · 2026-09-04T18:35:25Z

+ WasmLowering.LoweringFlags flags = WasmLowering.LoweringFlags.None;
+
+ if (signatureNode.HasGenericContextArg)
+ {
+ flags |= WasmLowering.LoweringFlags.HasGenericContextArg;
+ }
+
+ if (signatureNode.IsAsyncCall)
+ {
+ flags |= WasmLowering.LoweringFlags.IsAsyncCall;
+ }
+
+ if (signatureNode.IsUnmanagedCallersOnly)
+ {
+ flags |= WasmLowering.LoweringFlags.IsUnmanagedCallersOnly;
+ }
+
+ WasmFuncType signature = WasmLowering.GetSignature(signatureNode.Signature, flags).FuncType;


Not required for this PR, but we have similar logic in CorInfoImpl.recordCallSite(), CorInfoImpl.recordWasmManagedCallSig and WasmObjectWriter.RecordMethodDeclaration(). Should we add an overloads of WasmLowering.GetSignature() that take INodeWithTypeSignature or CORINFO_SIG_INFO* and generates the flags?

jtschuster · 2026-09-04T18:40:15Z

 protected override void EmitCode(NodeFactory factory, ref WasmEmitter encoder, bool relocsOnly)
 {
- throw new NotImplementedException();
+ INodeWithTypeSignature signatureNode = (INodeWithTypeSignature)this;


JumpStubNode doesn't implement INodeWithTypeSignature, though its only implementation, AddressTakenMethodNode, does. Should we add INodeWithTypeSignature to JumpStubNode with abstract implementations?

jtschuster · 2026-09-04T18:42:24Z

+ List<WasmExpr> expressions = new List<WasmExpr>(signature.Params.Types.Length + 1);
+ for (int i = 0; i < signature.Params.Types.Length; i++)
+ {
+ expressions.Add(Local.Get(i));
+ }
+
+ expressions.Add(ControlFlow.ReturnCall(_target));
+ encoder.FunctionBody = new WasmFunctionBody(signature, expressions.ToArray());


nit: could we preallocate the array instead of using a List and ToArray()?

jtschuster

Couple nits, but not necessarily blocking.

jkoritzinsky · 2026-09-05T18:28:13Z

@copilot please address all feedback from jtschuster.

Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Copilot · 2026-09-05T18:52:17Z

@copilot please address all feedback from jtschuster.

Addressed in 492d5db4: added shared WasmLowering overloads/helpers for signature lowering flags, made JumpStubNode carry the INodeWithTypeSignature contract directly, and preallocated the JumpStub expression array.

Note

AI-generated via GitHub Copilot.

Copilot

🟡 Changes recommended

WasmLowering.GetLoweringFlags(CORINFO_SIG_INFO*) currently treats any non-zero callConv flag bits (e.g., HASTHIS) as unmanaged, which can produce incorrect lowered signatures for normal managed calls.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review details

Files reviewed: 7/7 changed files
Comments generated: 1
Review effort level: Lite

…lags Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Copilot

🟢 Approval recommended

The changes are cohesive and consistent with existing Wasm lowering/signature patterns, and no correctness issues were identified in the updated emission and flag/signature propagation.

Review details

Files reviewed: 7/7 changed files
Comments generated: 0 new
Review effort level: Lite

Initial plan
fd5c0ba

CopilotAI assigned Copilot and jkoritzinsky Sep 4, 2026

github-project-automationBot added this to AppModel Sep 4, 2026

CopilotAI linked an issue Sep 4, 2026 that may be closed by this pull request
Implement JumpStubNode for WASM #133247
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Copilotstarted work on behalf of jkoritzinsky September 4, 2026 16:51 View session

github-actionsBot added the area-Build-mono label Sep 4, 2026

Implement wasm JumpStubNode argument-forwarding stub
b687e78
Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

CopilotAI changed the title ~~[WIP] Implement JumpStubNode as a WASM stub~~Implement wasm JumpStubNode with signature-matched argument forwardingSep 4, 2026

Copilotfinished work on behalf of jkoritzinsky September 4, 2026 17:18

CopilotAI requested a review from jkoritzinsky September 4, 2026 17:18

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Comment thread...lr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/Target_Wasm/WasmJumpStubNode.cs Outdated

Copilotstarted work on behalf of jkoritzinsky September 4, 2026 17:22 View session

Use return_call for wasm JumpStubNode tail-call
4384ac0
Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

Copilotfinished work on behalf of jkoritzinsky September 4, 2026 17:40

CopilotAI requested a review from jkoritzinsky September 4, 2026 17:40

jkoritzinsky marked this pull request as ready for review September 4, 2026 18:14

jkoritzinsky requested a review from MichalStrehovsky as a code owner September 4, 2026 18:14

jkoritzinsky requested review from jtschuster and a lite review from Copilot September 4, 2026 18:14

Copilotstarted reviewing on behalf of jkoritzinsky September 4, 2026 18:15 View session

jkoritzinsky added arch-wasm WebAssembly architecture area-NativeAOT-coreclr and removed area-Build-mono labels Sep 4, 2026

CopilotAI reviewed Sep 4, 2026
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Comment thread...lr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/Target_Wasm/WasmJumpStubNode.cs Outdated

jtschuster reviewed Sep 4, 2026
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jtschuster approved these changes Sep 4, 2026
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CopilotAI mentioned this pull request Sep 4, 2026
[WIP] Fix test failure for Regression_o_2 browser-wasm R2R incompatibilities #133274
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Copilotstarted work on behalf of jkoritzinsky September 5, 2026 18:28 View session

Address wasm JumpStub review feedback
492d5db
Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

CopilotAI review requested due to automatic review settings September 5, 2026 18:51

Copilotstarted reviewing on behalf of jkoritzinsky September 5, 2026 18:51 View session

Copilotfinished work on behalf of jkoritzinsky September 5, 2026 18:53

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Comment threadsrc/coreclr/tools/Common/JitInterface/WasmLowering.cs Outdated

Copilotstarted work on behalf of jkoritzinsky September 5, 2026 18:59 View session

Mask callConv with CORINFO_CALLCONV_MASK in WasmLowering.GetLoweringF…
1449c72
…lags Co-authored-by: jkoritzinsky <1571408+jkoritzinsky@users.noreply.github.com>

CopilotAI review requested due to automatic review settings September 5, 2026 19:04

Copilotfinished work on behalf of jkoritzinsky September 5, 2026 19:04

Copilotstarted reviewing on behalf of jkoritzinsky September 5, 2026 19:05 View session

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