Generate less metadata for generic compositions

[MichalStrehovsky]

Something I noticed as I was working on #129609. I don't think we need fully constructed MethodTable for composition information (neither for types, nor for generic virtual methods).

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Pull request overview

This PR adjusts NativeAOT (ILCompiler) dependency analysis so “generic composition” data can be emitted without forcing fully constructed EEType / MethodTable nodes, by introducing a “metadata-enabled” path for generic compositions and type arguments.

Changes:

• Renamed the “constructed” generic composition cache/API to “metadata-enabled” and routed relevant emit sites to use it.
• Added MaximallyMetadataEnabledType to pick metadata-capable EEType symbols for generic composition arguments without requiring fully constructed types.
• Updated EEType instantiation detail emission and GVM dispatch cell info emission to use metadata-enabled compositions/types.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/NodeFactory.cs	Adds MaximallyMetadataEnabledType, renames/rewires generic composition caches to “metadata-enabled”.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/GvmDispatchCellInfoSectionNode.cs	Switches GVM instantiation info emission/deps to metadata-enabled generic composition.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/GenericCompositionNode.cs	Renames flag to metadataEnabled and uses MaximallyMetadataEnabledType for arg EEType selection.
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/EETypeNode.cs	Uses metadata-enabled generic composition/types when emitting reflection-visible instantiation details.

[MichalStrehovsky]

/azp run runtime-nativeaot-outerloop

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[github-actions]

Holistic Review

Motivation: MethodTables referenced by generic composition information (for generic types and generic virtual methods) were being emitted as fully constructed types, which pulls in more metadata than is actually needed. Composition info only needs enough of a MethodTable to be metadata-enabled, not fully constructed. The author noticed this while working on #129609, so the goal is a straightforward size/metadata optimization for NativeAOT output.

Approach: The PR renames the constructed concept in generic composition to metadataEnabled and introduces two new NodeFactory helpers: MaximallyMetadataEnabledType(TypeDesc) (returns NecessaryTypeSymbol for canonical-definition types, otherwise MetadataTypeSymbol) and MetadataEnabledGenericComposition(Instantiation). Call sites in EETypeNode, GvmDispatchCellInfoSectionNode, and GenericCompositionNode are switched from the Constructed* variants to the new MetadataEnabled* variants, and the backing node cache/field (_constructedGenericCompositions → _metadataEnabledGenericCompositions) plus the GenericCompositionNode._constructed flag are renamed consistently.

Summary: This is a focused, low-risk change confined to the NativeAOT (ILCompiler) dependency-analysis layer. The renames are applied consistently across the node, factory, cache, and comparison (CompareToImpl) paths, so node identity/ordering semantics are preserved. The new MaximallyMetadataEnabledType correctly mirrors MaximallyConstructableType's canonical-type fallback via IsCanonicalDefinitionType, and generic-composition type arguments are concrete or canonical instantiation types — not generic definitions or synthetic AsyncContinuationTypes — so the tightened Debug.Asserts inside MetadataTypeSymbol are not expected to trip. The author has run runtime-nativeaot-outerloop to exercise the affected code paths, which is the appropriate validation for a metadata-reduction change of this kind. No correctness or maintainability concerns were found. LGTM.

Note

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Generated by Holistic Review · 54.3 AIC · ⌖ 10.3 AIC · ⊞ 10K

[Copilot]

🔵 Needs a closer look

Review details

Suppressed comments (1)

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/NodeFactory.cs:831

• MaximallyMetadataEnabledType unconditionally calls MetadataTypeSymbol for non-canonical types, but MetadataTypeSymbol asserts that AsyncContinuationType is not passed (see Debug.Assert in MetadataTypeSymbol). Prior code paths using MaximallyConstructableType would route AsyncContinuationType to ConstructedTypeSymbol, so this introduces a potential debug-build assert/regression if an instantiation/composition contains AsyncContinuationType. Consider mirroring the existing special-case handling to keep behavior consistent and avoid the assert.

        public IEETypeNode MaximallyMetadataEnabledType(TypeDesc type)
        {
            if (type.IsCanonicalDefinitionType(CanonicalFormKind.Any))
                return NecessaryTypeSymbol(type);
            else
                return MetadataTypeSymbol(type);
        }

• Files reviewed: 4/4 changed files
• Comments generated: 0 new
• Review effort level: Lite

[MichalStrehovsky]

@jkotas could you please reapprove? there was a merge conflict and the approval got reset :(