perf(react_compiler): store AbstractValue reasons as a u16 bitmask#24480
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…24480) Follow-up to #24476. Profiling the mutation-aliasing pass after that PR showed the `SmallVec<[ValueReason; 4]>` I introduced for `AbstractValue.reason` at **~7% of compile self-time** — it no longer allocates, but it's still copied on every `AbstractValue` clone, which happens once per entry on every `InferenceState` clone in the fixpoint. There are only 12 `ValueReason` variants, so the whole set fits in a `u16` bitmask. `ReasonSet` — and therefore `AbstractValue` — becomes `Copy`, so copying it is a register move instead of a memcpy, and membership / union / superset collapse to single bitwise ops. The one behavioral wrinkle is `primary_reason`, which returns the first non-`Other` reason: it now iterates in `ValueReason` declaration order rather than insertion order. The full snapshot suite (`tests/snapshot.rs`, the ~1288 upstream fixtures) is **unchanged**, confirming the ordering difference is not observable in output. ### Results Real-world React component files (from `bluesky-social/social-app`), compile pass only: | File | before | after | | --- | ---: | ---: | | Explore.tsx (35 KB) | 23.1 ms | **21.2 ms** (−8%) | | MessageItem.tsx (30 KB) | 21.3 ms | **20.5 ms** (−4%) | | Drawer.tsx (21 KB) | 8.6 ms | 8.7 ms (noise; few reasons) | Allocation count is unchanged — the `SmallVec` was already inline, so this is purely a copy/`memcpy` win. 🤖 Generated with [Claude Code](https://claude.com/claude-code)
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### 💥 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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Follow-up to #24476. Profiling the mutation-aliasing pass after that PR showed the
SmallVec<[ValueReason; 4]>I introduced forAbstractValue.reasonat ~7% of compile self-time — it no longer allocates, but it's still copied on everyAbstractValueclone, which happens once per entry on everyInferenceStateclone in the fixpoint.There are only 12
ValueReasonvariants, so the whole set fits in au16bitmask.ReasonSet— and thereforeAbstractValue— becomesCopy, so copying it is a register move instead of a memcpy, and membership / union / superset collapse to single bitwise ops.The one behavioral wrinkle is
primary_reason, which returns the first non-Otherreason: it now iterates inValueReasondeclaration order rather than insertion order. The full snapshot suite (tests/snapshot.rs, the ~1288 upstream fixtures) is unchanged, confirming the ordering difference is not observable in output.Results
Real-world React component files (from
bluesky-social/social-app), compile pass only:Allocation count is unchanged — the
SmallVecwas already inline, so this is purely a copy/memcpywin.🤖 Generated with Claude Code