perf: replace anonymous Member classes with concrete ExprFieldMember/MethodFieldMember#756
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stephenamar-db merged 1 commit intomasterfrom Apr 11, 2026
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…MethodFieldMember Every field in visitMemberList previously created an anonymous Val.Obj.Member subclass, generating N distinct classes per object expression. This pollutes the JIT profile with megamorphic dispatch at invoke() call sites. Replace with two concrete classes (ExprFieldMember, MethodFieldMember) and a shared ObjectScopeFactory. All fields from the same object literal share one factory which encapsulates the scope-caching logic (previously in the makeNewScope/createNewScope closures). Benefits: - Monomorphic dispatch at Member.invoke() -> better JIT inlining - Explicit fields instead of synthetic closure captures - Scope caching preserved via shared ObjectScopeFactory - One factory allocation per object replaces N closure allocations
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We need more pattern-driven AST transformation, too. |
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Summary
Val.Obj.Membersubclasses invisitMemberListwith concreteExprFieldMemberandMethodFieldMemberclasses, giving the JIT a monomorphic type at everyinvoke()call site for better inlining.makeNewScope/createNewScopeclosures) into anObjectScopeFactoryclass. All fields from the same object literal share one factory, preserving per-object scope caching while eliminating per-field closure allocations.Benchmark results
JMH regression suite (
bench.runRegressions), JDK 21.0.10, single fork, 1 warmup + 1 measurement iteration (10s):No regressions observed (remaining benchmarks within noise).
Test plan
./mill 'sjsonnet.jvm[3.3.7]'.test— all tests pass./mill __.checkFormat— formatting verified