perf(react_compiler): make aliasing effects cheap to intern and clone#24506
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Boshen merged 3 commits intoJul 14, 2026
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Interning aliasing effects (and the fixpoint-stable ValueId cache) hashed every effect by building a formatted `String` per lookup on the hot path of `apply_effect`. Replace the string with an `EffectKey` enum that carries exactly the same identifying fields — other fields such as `Apply::signature`/`span` and `Mutate::reason` still do not participate in identity, and the one collapse the string encoding had (an empty `Apply` argument list vs a single hole) is reproduced explicitly. Building and hashing a key no longer allocates or runs the formatting machinery, except in the rare error-carrying arms which clone their message strings.
… via Rc `AliasingEffect::Apply` inlined an owned `FunctionSignature` — a struct carrying several vectors and strings (builtin aliasing configs like `Array.prototype.map` reach ~20 heap allocations) — so every clone of an Apply effect on the fixpoint hot path was a multi-allocation deep copy, and the enum's size was dominated by this one variant. Wrap it in `Rc`: the signature is deep-cloned out of the shape registry once per call instruction as before, and every subsequent effect clone bumps a refcount. Interning keys already ignore the signature field, and all readers access it immutably.
`apply_signature` cloned the cached signature's whole effect list on every instruction application because the cache borrow conflicts with passing the context on mutably. Wrap cache entries in `Rc` so holding the signature across the loop is a reference-count bump instead of a deep clone.
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@Boshen Here's the follow-up PR I promised! |
Merging this PR will improve performance by 7.26%
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| Mode | Benchmark | BASE |
HEAD |
Efficiency | |
|---|---|---|---|---|---|
| ⚡ | Simulation | react_compiler[RadixUIAdoptionSection.jsx] |
2.9 ms | 2.7 ms | +9.91% |
| ⚡ | Simulation | linter[RadixUIAdoptionSection.jsx] |
3.4 ms | 3.2 ms | +7.64% |
| ⚡ | Simulation | react_compiler[kitchen-sink.tsx] |
201.9 ms | 193.5 ms | +4.31% |
Tip
Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.
Comparing mds-ant:perf/react-compiler-effect-interning (fa9662a) with main (c517aa0)
Footnotes
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61 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩
camc314
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Jul 21, 2026
### 💥 BREAKING CHANGES - 54cc121 ast: [**BREAKING**] Split `MetaProperty` into `ImportMeta` and `NewTarget` (#24557) (camc314) ### 🚀 Features - 4c71560 parser: More friendly error for spread element in dynamic imports (#24705) (sapphi-red) - 7b045cd minfier: Drop last break from last switch case (#24673) (Armano) - 7d3c178 minifier: Remove unreachable recursive functions (#24125) (Dunqing) - 94f99b3 ast: Allow `NONE` to be passed to AST builder methods where `Option<ArenaVec>` is expected (#24629) (overlookmotel) - 77230c5 ast: Accept arrays for `ArenaVec` params of AST builder methods (#24621) (overlookmotel) - f08b152 allocator: Implement `FromIn` for array to `Vec` conversion (#24620) (overlookmotel) - 2338c13 track-memory-allocations: Track heap deallocs, alloc bytes, and peak growth (#24619) (Boshen) - 7aa4739 syntax,transformer: Move JSX entity decoder to `oxc_syntax` (#24617) (camc314) - 2b097c4 str: Export `Str` as `ArenaStr` (#24604) (overlookmotel) - 3acf4c1 minifier: Expand switch optimiation to remove empty cases (#24520) (Armano) - 129b759 parser: Improve diagnostics for unparenthesized LHS on exponential expr (#24569) (camc314) - 4d0c601 minifier: Fold arithmetic over undefined and null operands (#24485) (Dunqing) - 91541dd minifier: Drop empty switch statements (#24527) (Armano) - d05224d ast_visit: Generate VisitJs visitor that skips TypeScript type-space (#24499) (Boshen) - 3d22307 parser: Add `ParseOptions::enable_ident_hashes` (#24491) (Boshen) ### 🐛 Bug Fixes - 64c2241 minifier: Align class heritage removal with assumptions (#24533) (Dunqing) - 48b59f4 parser: Span ambient generator diagnostics (#24711) (camc314) - e750a82 ecmascript: Fix false negative for may_have_side_effects on dynamic property access (#24709) (sapphi-red) - f145d73 minifier: Guard reordered identifier reads (#24698) (Dunqing) - a2ef382 isolated-declarations: Reject `window.Symbol` as global symbol reference (#24689) (camc314) - b1bcf72 minifier: Invalidate facts for redeclared bindings (#24658) (Dunqing) - 921b834 minifier: Don't treat a conditionally-assigned var as write-once (#24650) (Dunqing) - 061af1f minifier: Avoid stale pure function summaries (#24636) (Dunqing) - 40c2f43 allocator: `Vec::from_array_in` do not allocate zero-length array (#24628) (overlookmotel) - 70994ae codegen: Preserve comments before expression operands (#24510) (Dunqing) - 7b4baff parser: Reject new import member access (#23459) (camc314) - 128b385 minifier: Clippy warning with no-debug-assertions (#24547) (camc314) - 8421feb parser: Use first `as` span for imported name (#24537) (leaysgur) - c517aa0 parser: Reject invalid accessor assertions (#24504) (camc314) ### ⚡ Performance - 884d9eb parser: Pre-size cover-grammar assignment target buffers (#24683) (Boshen) - d3f07a0 diagnostics: Box OxcDiagnosticInner to reduce binary size (#24665) (Boshen) - bcc9de0 parser: Defer diagnostic creation until parse exit (#24663) (Boshen) - c35d8ab allocator: Mark `ReplaceWith` panic path cold (#24515) (camc314) - ba65790 semantic, allocator: Branchless `clone_in` for semantic IDs (#24564) (overlookmotel) - 747feec parser: Build AST nodes with the AST builder instead of cloning (#24540) (Boshen) - ba35a0d react_compiler: Use IndexVec for dense id-keyed maps (#24549) (Boshen) - b685062 react_compiler: Keep small hot-path collections inline (#24514) (Marius Schulz) - a149e95 transformer: Outline rare expression exits (#24512) (camc314) - 7808a6e react_compiler: Make aliasing effects cheap to intern and clone (#24506) (Marius Schulz) - 3a36f2a react_compiler: Store AbstractValue reasons as a u16 bitmask (#24480) (Boshen) - 1c96753 react_compiler: Use FxHashMap for the lookup-only aliasing node map (#24490) (Boshen) Co-authored-by: Cameron <[email protected]>
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What
The mutation/aliasing inference interns every effect it applies. Both the interning map and the fixpoint-stable ValueId cache were keyed by a formatted
String, so every lookup on theapply_effecthot path built a fresh string. On top of that,AliasingEffect::Applycarried an ownedFunctionSignature, so cloning an Apply effect meant copying the whole struct including its parameter effect list, andapply_signaturedeep-cloned the cached effect list of every instruction it applied.Change
Stringkey with anEffectKeyenum carrying exactly the fields the string encoded.Apply::signature/spanandMutate::reasonstill don't participate in identity, and the one collision the string format had (an emptyApplyargument list vs a single hole) is reproduced on purpose. Building and hashing a key no longer allocates or formats, except in the rare error-carrying arms, which clone their message strings.FunctionSignatureinApplybehindRc. It's still deep-cloned out of the shape registry once per call instruction, but every later clone of the effect is just a refcount bump. The interning key already ignores the signature, and all readers are immutable.InstructionSignatureentries behindRctoo, soapply_signaturecan hold the signature while passing the context on mutably, instead of cloning the whole effect list each time.Follow-up to #24117; this PR is based on current main, which includes it.
Numbers from linting cal.com with only
react/react-compilerenabled, single thread, fat-LTO release build:Verification
reportAllBailoutson and off.react_compilerexample (parse, compile, codegen) produces identical output on all 1438 corpus files.cargo test -p oxc_react_compilerpasses, including the 1,736-fixture snapshot corpus: compiled output is unchanged on every fixture.cargo clippyandcargo fmtclean.One note for future re-syncs with the vendored React Compiler sources:
EffectKeymirrorsAliasingEffectvariant for variant. Adding an identity-relevant field to a variant without updatingeffect_keysilently changes interning behavior. Keep the two in sync.This PR was assisted by Claude Code.