perf(parser): allocate TriviaBuilder comments in the arena#21512
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graphite-app[bot] merged 1 commit intomainfrom Apr 23, 2026
Merged
perf(parser): allocate TriviaBuilder comments in the arena#21512graphite-app[bot] merged 1 commit intomainfrom
TriviaBuilder comments in the arena#21512graphite-app[bot] merged 1 commit intomainfrom
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Merging this PR will not alter performance
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overlookmotel
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Great!
I've rebased on latest main to fix merge conflicts.
Side note: The comment about irregular_whitespaces is not quite correct. Converting an ArenaVec<'a, T> to Box<'a, [T]> is free (no mem copy, no reallocation), as it doesn't need to free the spare capacity - unlike with heap-allocated Vec<T> -> Box<[T]> which does have to reallocate.
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## Summary Thread the arena lifetime into `TriviaBuilder` and store `comments` in an `oxc_allocator::Vec` instead of `std::Vec`. At the end of `parse`, comments are moved directly into `program.comments`, eliminating the finalize-time `vec_from_iter` copy. Sys reallocs drop across the benchmark files: | File | Sys reallocs (before → after) | | --- | --- | | checker.ts | 21 → 10 | | cal.com.tsx | 49 → 41 | | pdf.mjs | 75 → 67 | | antd.js | 235 → 221 | | binder.ts | 7 → 0 | Arena reallocs tick up slightly to absorb the comment pushes; arena bytes unchanged. `irregular_whitespaces` stays as `std::Vec` — it's almost always empty in practice, and its `Box<[Span]>` escape would need a heap copy at finalize either way.
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### 💥 BREAKING CHANGES - 502e804 ast: [**BREAKING**] Reduce size of `TSTypePredicateName` (#21711) (overlookmotel) - 5651539 ast: [**BREAKING**] Reduce size of `JSXExpression` (#21710) (overlookmotel) - c44e280 ast: [**BREAKING**] Reduce size of `ArrayExpressionElement` (#21709) (overlookmotel) - c5b3deb syntax: [**BREAKING**] Remove `CommentNodeId` (#21679) (overlookmotel) ### 🚀 Features - b738a39 allocator: Add `Allocator::cursor_ptr` method (#21773) (overlookmotel) - 678767e ast: Generate node_id accessors for AST enum wrappers (#21653) (camc314) - f091d77 minifier: Inline constant spread elements into arrays (#21095) (Armano) ### 🐛 Bug Fixes - 0d608c2 minifier: Preserve raw CR in template literals (#21645) (Dunqing) - a889ea9 minifier: Track pure functions in DCE mode (#21722) (Dunqing) - 674dfac allocator: `Arena` retry allocation when chunk size approaches maximum (#21777) (overlookmotel) - f130cc0 allocator: Fix arithmetic overflow in `Arena::new_chunk_memory_details` (#21745) (overlookmotel) - b9bf239 allocator: Fix UB in `Arena::grow_zeroed` (#21739) (overlookmotel) - d2b9389 allocator: Clippy warning when building without `testing` feature (#21681) (camc314) - 503dc86 codegen: Map sourcemaps from visible output starts (#21662) (Dunqing) - c92bd3b transformer: Use SPAN for synthesized helper calls to prevent comment misattribution (#21578) (Dunqing) - 0d80441 codegen: Add mapping before printing `#` for private ident (#21619) (camc314) ### ⚡ Performance - 9fa362e napi/parser: Do not generate tokens except in tests (#21811) (overlookmotel) - 0044392 allocator: Reduce branches when allocating new chunk (#21776) (overlookmotel) - 7896bd0 allocator: `Allocator::used_bytes` do not use chunk iterator (#21771) (overlookmotel) - a5c562f allocator: Remove check in `Arena::new_chunk_memory_details` (#21750) (overlookmotel) - 35bbe1f allocator: `Arena` use unchecked size round up where guaranteed no overflow (#21743) (overlookmotel) - ffe229b allocator: Remove unnecessary check from `Arena::try_alloc_layout_slow_impl` (#21732) (overlookmotel) - 72fece5 allocator: Use `NonNull::offset_from_unsigned` in `Arena::chunk_capacity` (#21731) (overlookmotel) - cab32ae ast: Add `#[inline(always)]` to `node_id` methods on enums with all variants unboxed (#21707) (overlookmotel) - b179688 parser: Allocate `TriviaBuilder` comments in the arena (#21512) (Boshen) - 2290f31 lexer: Fix perf of `Token::set_*` methods on Rust 1.95.0 (#21659) (overlookmotel) - 1b58029 allocator: Move code into cold path in `Arena::alloc_layout` (#21622) (overlookmotel) - 3cf7cef allocator: Reduce instructions on allocation hot path (#21510) (overlookmotel) ### 📚 Documentation - ce65070 data_structures: Document why `as_ref` and `as_mut` on `NonNullConst` and `NonNullMut` take `self` (#21800) (overlookmotel) - 93b7dbd allocator: Improve doc comments for `ChunkFooter` (#21733) (overlookmotel) - 295db8d transformer: Fix comment (#21717) (overlookmotel) - 5c93af8 ast: Add comments explaining `#[inline(always)]` to `node_id` methods on enums (#21706) (overlookmotel) - e4cea25 transform: Use the `node:` namespace in the example (#19998) (루밀LuMir) ### 🛡️ Security - d8076c9 deps: Update rolldown (#21639) (renovate) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>
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Summary
Thread the arena lifetime into
TriviaBuilderand storecommentsin anoxc_allocator::Vecinstead ofstd::Vec. At the end ofparse, comments are moved directly intoprogram.comments, eliminating the finalize-timevec_from_itercopy.Sys reallocs drop across the benchmark files:
Arena reallocs tick up slightly to absorb the comment pushes; arena bytes unchanged.
irregular_whitespacesstays asstd::Vec— it's almost always empty in practice, and itsBox<[Span]>escape would need a heap copy at finalize either way.