feat(allocator): add Vec::push_fast method#19959
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Pull request overview
This PR adds a performance-focused alternative to Vec::push in oxc_allocator’s bump-allocated Vec, optimizing for the common case where the vector already has spare capacity (as expected in parser hot paths).
Changes:
- Added
Vec::push_fast, which keeps the “grow” path out-of-line via a#[cold]+#[inline(never)]slow function. - Updated
Vec::pushrustdoc to cross-reference the newpush_fastAPI. - Added rustdoc for
push_fast, including usage guidance and an example.
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`Vec::push` considers the "the `Vec` needs to grow" case as fairly likely. Benchmarking showed this is the best strategy for the parser. Add a method `Vec::push_fast` which is optimized for the opposite scenario - the `Vec` is highly likely to have sufficient capacity to push the element without growing. It makes the "needs to grow" path `#[cold]` and `#[inline(never)]` so `Vec::push_fast` can be inlined into call sites with minimum of instructions. `Vec::push_fast` is the best choice where either: 1. The `Vec` is large and grows infrequently. 2. Sufficient capacity is allocated when initializing the `Vec`, so it will *never* need to grow. `Vec::push` is a better choice for: 1. Small `Vec`s (which will grow on every push). 2. `Vec`s which start with zero capacity, so first push will always cause growth.
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Use `Vec::push_fast` method (introduced in #19959) for pushing to the tokens `Vec`. We allocate sufficient capacity upfront in the `Vec`, so it should never need to grow. `Vec::push_fast` makes the "need to grow" path cold and `#[inline(never)]`, which should reduce the size of `Lexer::finish_next`, and help the branch predictor make accurate predictions. +1% on benchmark for parsing with tokens in CodSpeed. *Possible* it'll have more impact in real world as CodSpeed doesn't take branch predictor into account in its simulations.
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### 🚀 Features - e8547cc parser: Report error for using declarations in ambient contexts (#19934) (camc314) - 8345318 allocator: Add methods for boxed slices `ArenaBox<[T]>` (#19968) (overlookmotel) - f83be30 allocator: Add `Vec::push_fast` method (#19959) (overlookmotel) ### 🐛 Bug Fixes - 291d867 transformer_plugins: Unwrap ChainExpression after define replacement removes optional markers (#20058) (IWANABETHATGUY) - 36b2e56 codegen: Print type for TSImportEqualsDeclaration (#20128) (camc314) - 5a246ec codegen: Print type arguments for JSXOpeningElement (#20127) (camc314) - a40870e codegen: Preserve parens for TSNonNullExpression (#20125) (camc314) - ae830b2 codegen: Print `declare` for `TSInterfaceDeclaration` (#20124) (camc314) - 92cfb14 linter/plugins: Fix types for `walkProgram` and `walkProgramWithCfg` (#20081) (overlookmotel) - ee0491e apps,napi: Explicitly specify libs in tsconfigs (#20071) (camc314) - 588009e codegen: Print `static` keyword for TSIndexSignature (#19755) (Dunqing) - 5a8799c codegen: Print `with_clause` for `ExportNamedDeclaration` (#20002) (Dunqing) - 7502afe parser: Correct capacity for tokens `Vec` (#19967) (overlookmotel) ### ⚡ Performance - 4ea8f9a napi: Remove `napi_build::setup()` from `oxc_napi` to avoid redundant rebuilds (#20094) (Boshen) - 2baa5fb napi: Unify build-test profile to coverage for cache sharing (#20090) (Boshen) - 8ba61dd parser: Make pushing tokens faster (#19960) (overlookmotel) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>
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Vec::pushconsiders the "theVecneeds to grow" case as fairly likely. Benchmarking showed this is the best strategy for the parser.Add a method
Vec::push_fastwhich is optimized for the opposite scenario - theVecis highly likely to have sufficient capacity to push the element without growing.It makes the "needs to grow" path
#[cold]and#[inline(never)]soVec::push_fastcan be inlined into call sites with minimum of instructions.Vec::push_fastis the best choice where either:Vecis large and grows infrequently.Vec, so it will never need to grow.Vec::pushis a better choice for:Vecs (which will grow on every push).Vecs which start with zero capacity, so first push will always cause growth.