Implement ReadyToRunGenericHelperNode for WASM

[Copilot]

WASM compilation could not emit ReadyToRun generic helper stubs because their architecture-specific implementation was missing.

Changes

• Define WASM signatures for generic lookup and delegate helpers.
• Emit dictionary and type-context lookups.
• Support static-base, thread-static, delegate, and handle helpers.
• Route invalid dictionary entries to ThrowUnavailableType.

Note

This description was generated by GitHub Copilot.

• Fixes Implement ReadyToRunGenericHelperNode for WASM #134077

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[Copilot]

🟡 Changes recommended

Critical and moderate stack/dictionary-pointer issues remain unresolved.

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Pull request overview

Adds WASM ReadyToRun generic helper emission for dictionary, static-base, thread-static, delegate, type-context, and handle lookups.

Changes:

• Defines WASM helper signatures and lookup emission.
• Handles invalid dictionary entries via ThrowUnavailableType.
• Supports generic static and delegate helpers.

File summaries

File	Description
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/Target_Wasm/WasmReadyToRunGenericHelperNode.cs	Adds WASM generic helper code generation.

Review details

Suppressed comments (5)

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/Target_Wasm/WasmReadyToRunGenericHelperNode.cs:125

• ❌ The Tee preserves the index-cell value on the stack while the code also loads the type-manager pointer and thread-static index from it. Together with the initial Local.Get(0), the call stack becomes [SP, indexCell, manager, index], leaving an extra operand; the corresponding non-generic WASM helper passes only [SP, manager, index]. Consume the lookup result with Local.Set before reloading it for the two loads.

[!NOTE] This review comment was generated by GitHub Copilot.

                    expressions.Add(Local.Tee(resultLocalIndex));

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/Target_Wasm/WasmReadyToRunGenericHelperNode.cs:199

• The generic context is not at these local indices: the non-delegate signature has one parameter (so its context is local 0), and the delegate signature has three parameters (so its context is local 2). Local.Get(1)/Local.Get(3) therefore read the first uninitialized local, causing every lookup to use an invalid dictionary pointer. Load index 0 for regular helpers and index 2 for DelegateCtor, matching the argument layout used by the other target implementations.

        protected virtual void EmitLoadGenericContext(
            NodeFactory factory,
            List<WasmExpr> expressions,
            bool relocsOnly)
        {
            expressions.Add(Local.Get(Id == ReadyToRunHelperId.DelegateCtor ? 3 : 1));

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/Target_Wasm/WasmReadyToRunGenericHelperNode.cs:154

• For DelegateCtor, the third parameter is the generic context and is overwritten by EmitDictionaryLookup with the target method before invoking the constructor. Passing Local.Get(2) here also passes the unmodified generic context as a third constructor argument, shifting the lookup result and optional thunk to the wrong positions (the x64 implementation only forwards Arg0/Arg1 before replacing Arg2). Remove this expression so the constructor receives its expected arguments.

                    expressions.Add(Local.Get(0));
                    expressions.Add(Local.Get(1));
                    expressions.Add(Local.Get(2));
                    EmitDictionaryLookup(factory, expressions, contextLocalIndex, resultLocalIndex, LookupSignature, relocsOnly);

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/Target_Wasm/WasmReadyToRunGenericHelperNode.cs:115

• In the lazy-cctor GC-static path, this subtraction leaves the adjusted non-GC static-base pointer on the operand stack, but the next EmitDictionaryLookup reads contextLocalIndex, which still contains the original dictionary pointer. Store the adjusted pointer back to contextLocalIndex before the second lookup; otherwise the GC lookup is performed against the wrong dictionary.

                        GenericLookupResult nonGcRegionLookup =
                            factory.GenericLookup.TypeNonGCStaticBase((MetadataType)Target);
                        EmitDictionaryLookup(factory, expressions, contextLocalIndex, resultLocalIndex, nonGcRegionLookup, relocsOnly);
                        expressions.Add(I32.Const(NonGCStaticsNode.GetClassConstructorContextSize(factory.Target)));
                        expressions.Add(I32.Sub);
                        EmitDictionaryLookup(factory, expressions, contextLocalIndex, resultLocalIndex, LookupSignature, relocsOnly);

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/Target_Wasm/WasmReadyToRunGenericHelperNode.cs:69

• This adds all of the WASM generic-helper code paths without a WASM regression test. The existing generic lookup R2R test is explicitly excluded on WASM (R2RTestSuites.cs:2168), and the current WASM tests only compile non-generic smoke cases, so failures in these stack layouts, helper signatures, or invalid-slot handling can regress unnoticed. Add a WASM-targeted R2R test that forces representative generic dictionary/type lookups (including a static or delegate helper) and validates that crossgen2 emits the module successfully.

[!NOTE] This review comment was generated by GitHub Copilot.

        protected sealed override void EmitCode(NodeFactory factory, ref WasmEmitter encoder, bool relocsOnly)

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

[Copilot]

Copilot review overview

🟡 Changes recommended

The lazy non-GC static-base path generates an invalid operand stack and class-constructor context.

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Review effort: Balanced
Findings: 1

Open (1)

• Preserve static base with Local.Tee before context subtraction · New

Resolved since last review (1)

• ❌ Local.Tee leaves the dictionary result on the operand stack. Since the preceding Local.Get(0)…

[Copilot]

Copilot review overview

🟡 Changes recommended

The new code-generation paths lack targeted WASM regression coverage.

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Review effort: Balanced
Findings: 1

Open (1)

• Missing WASM regression coverage for generic helper emission · New

Resolved since last review (1)

• Preserve static base with Local.Tee before context subtraction

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