perf(isolated_declarations): allocate AST nodes in arena directly by overlookmotel · Pull Request #23709 · oxc-project/oxc

overlookmotel · 2026-06-22T12:30:58Z

Small perf optimizations around AST builder calls.

AST nodes which end up in Boxes, allocate into the Box as early as possible, to increase chance compiler sees the type can be built directly in arena, rather than built on the stack, and then copied from stack into arena.
Functions return Box<T> rather than T where the value needs to be boxed anyway. If function is not inlined, this avoids stack allocation + copy.

Also, shorten code where possible by using more specific AstBuilder methods.

In transform_formal_parameters, clone the Box<FormalParameters> instead of cloning FormalParameters on stack and then moving it into a Box.

overlookmotel · 2026-06-22T12:31:12Z

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codspeed-hq · 2026-06-22T12:34:57Z

Merging this PR will not alter performance

✅ 52 untouched benchmarks
⏩ 19 skipped benchmarks¹

_{Comparing om/06-21-perf_isolated_declarations_allocate_ast_nodes_in_arena_directly (2e9ab4d) with main (ef5b472)}

19 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. ↩

Copilot

Pull request overview

This PR applies small performance-oriented refactors in oxc_isolated_declarations to allocate AST nodes directly into the arena earlier (and to return boxed nodes where boxing is inevitable), reducing intermediate stack allocations and copies.

Changes:

Switch transform_export_named_declaration to return an arena-allocated Box and build it via alloc_export_named_declaration.
Avoid extra allocations when producing transformed statements by constructing Statement variants directly with already-boxed nodes.
Update transform_formal_parameters to accept &ArenaBox<FormalParameters> and fast-path by cloning the boxed value directly.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
crates/oxc_isolated_declarations/src/module.rs	Return/export named declarations as arena-allocated boxes (`alloc_export_named_declaration`).
crates/oxc_isolated_declarations/src/lib.rs	Use statement variants directly with boxed nodes; allocate variable declarations directly in the arena.
crates/oxc_isolated_declarations/src/function.rs	Accept boxed formal parameters and clone the box directly in the fast-path.

graphite-app · 2026-06-23T00:59:34Z

Merge activity

Jun 23, 12:59 AM UTC: overlookmotel added this pull request to the Graphite merge queue.
Jun 23, 1:04 AM UTC: Merged by the Graphite merge queue.

…3709) Small perf optimizations around AST builder calls. - AST nodes which end up in `Box`es, allocate into the `Box` as early as possible, to increase chance compiler sees the type can be built directly in arena, rather than built on the stack, and then copied from stack into arena. - Functions return `Box<T>` rather than `T` where the value needs to be boxed anyway. If function is not inlined, this avoids stack allocation + copy. Also, shorten code where possible by using more specific `AstBuilder` methods. In `transform_formal_parameters`, clone the `Box<FormalParameters>` instead of cloning `FormalParameters` on stack and then moving it into a `Box`.

Same as #23709. Small perf optimizations around AST builder calls. - AST nodes which end up in `Box`es, allocate into the `Box` as early as possible, to increase chance compiler sees the type can be built directly in arena, rather than built on the stack, and then copied from stack into arena. - Functions return `Box<T>` rather than `T` where the value needs to be boxed anyway. If function is not inlined, this avoids stack allocation + copy. Also, shorten code where possible by using more specific `AstBuilder` methods.

Same as #23709. Small perf optimizations around AST builder calls. - AST nodes which end up in `Box`es, allocate into the `Box` as early as possible, to increase chance compiler sees the type can be built directly in arena, rather than built on the stack, and then copied from stack into arena. - Functions return `Box<T>` rather than `T` where the value needs to be boxed anyway. If function is not inlined, this avoids stack allocation + copy. Also, shorten code where possible by using more specific `AstBuilder` methods. In `transform_ts_import_equals`, additionally avoid unnecessarily allocating the string `"require"` into arena, by using `static_ident!` instead.

### 💥 BREAKING CHANGES - 94fbacb ast: [**BREAKING**] Only export `AstBuilder` and `NONE` in `builder` module (#23876) (overlookmotel) - 8de5122 ecmascript: [**BREAKING**] Switch to new `AstBuilder` (#23834) (overlookmotel) - dc0ef38 transformer: [**BREAKING**] Switch to new `AstBuilder` (#23831) (overlookmotel) - 88f4455 str: [**BREAKING**] `Str` and `Ident` methods take `&GetAllocator` (#23781) (overlookmotel) - 36009dd allocator: [**BREAKING**] `GetAllocator::allocator` take `&self` (#23676) (overlookmotel) - bd74f9d allocator: [**BREAKING**] Rename `AllocatorAccessor` trait to `GetAllocator` (#23675) (overlookmotel) ### 🚀 Features - 326fe25 transformer_plugins: Support `typeof` `define` keys (#23605) (Alexander Lichter) - f2091b3 ast: Unify old and new `AstBuilder`s (#23875) (overlookmotel) - cd1fd12 codegen: Expose `Codegen::print_string` API (#23785) (camc314) - 785461b ast: Add custom builder methods to AST types (#23651) (overlookmotel) - 05d1357 ast: Add AST creation methods to AST types (#23650) (overlookmotel) - 2580eda str: Add `Str::from_str_in` and `Ident::from_str_in` methods (#23767) (overlookmotel) - 6883fcf minifier: Fold write-once falsy var to false in boolean context (#23540) (Dunqing) - fcbf993 allocator: Add `Vec::from_value_in` method (#23718) (overlookmotel) - 989ddb7 allocator: Add `Vec::from_box_in` method (#23717) (overlookmotel) - 9d1aa7f allocator: Improve `PartialEq` for `Vec` (#23716) (overlookmotel) ### 🐛 Bug Fixes - da0e5bf minifier: Don't reorder a closed-over TDZ read when inlining a var (#23771) (Dunqing) - 0b3021f allocator: Remove `Vec::from_box_in` (#23873) (overlookmotel) - 0ab64ec ast: Silence deprecation warnings within files defining deprecated `AstBuilder` methods (#23889) (overlookmotel) - 8c07cad all: Enable `disable_old_builder` Cargo feature for `oxc_ast` crate in tests (#23888) (overlookmotel) - 3800f01 ast: Legacy `AstBuilder` methods take `self` not `&self` (#23891) (overlookmotel) - 869ac20 semantic/cfg: Connect for update exit to loop test (#23791) (camc314) - d3e92d5 semantic/cfg: Connect while branches from condition exit (#23790) (camc314) - 025045d ast: `ExportNamedDeclaration` plain builder methods return boxed nodes (#23783) (overlookmotel) - 7537c58 ast: Fix name of `AstBuilder` method for `Expression::V8IntrinsicExpression` (#23766) (overlookmotel) - 3f574f5 traverse: Fix unsoundness in `Traverse` walk functions (#23745) (overlookmotel) - 585760f parser: String in AST reference arena (#23721) (overlookmotel) - 7231d55 allocator: Fix unsound lifetime extension in `Box::new_in` (#23685) (overlookmotel) ### ⚡ Performance - d5c916a semantic: Flatten hoisting_variables to avoid per-scope map allocation (#23927) (Lawrence Lin) - e71609d minifier: Bail member-expr folding before the side-effect walk (#23924) (Lawrence Lin) - e1f89ab minifier: Reduce string allocations folding addition (#23846) (overlookmotel) - 9f6ee3b isolated-declarations: Pool scope maps to avoid per-scope alloc/rehash (#23761) (Boshen) - 0b07c4c semantic: Avoid heap alloc for catch-clause binding ids (#23911) (Lawrence Lin) - c5eef8b regular_expression: Skip capturing-group pre-parse when pattern has no `(` (#23908) (Lawrence Lin) - b4f5b4b isolated_declarations: Remove redundant clone of formal parameter pattern (#23912) (Lawrence Lin) - 53d083f isolated_declarations: Use `TakeIn` not `CloneIn` (#23847) (overlookmotel) - 3ea9304 react_compiler: Use faster API to arena allocate strings (#23849) (overlookmotel) - a6d8e45 parser: Avoid span lookup for arrow expression body (#23788) (camc314) - e1886a0 transformer, minifier: Use `static_ident!` macro to create static `Ident`s (#23727) (overlookmotel) - 5527bef transformer/object-rest-spread: Reduce iteration (#23720) (overlookmotel) - 680ffbc transformer: Allocate AST nodes in arena directly (#23711) (overlookmotel) - 1c63c66 parser: Allocate AST nodes in arena directly (#23712) (overlookmotel) - 3855f0c minifier: Allocate AST nodes in arena directly (#23710) (overlookmotel) - d025887 isolated_declarations: Allocate AST nodes in arena directly (#23709) (overlookmotel) - 10b96c6 parser: Remove string search from parsing JSX element name (#23713) (overlookmotel) ### 📚 Documentation - 3d61dea all: Correct capitalization in comments (#23887) (overlookmotel) - aa1ad74 ast: Add `#[deprecated]` to legacy `AstBuilder` methods (#23877) (overlookmotel) - a4676db ast: Correct doc comment for `NONE` (#23765) (overlookmotel) - 419ec80 syntax: Fix typo in doc comment (#23674) (overlookmotel) ### 🛡️ Security - 3cdd18f deps: Update npm packages (#23690) (renovate[bot]) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com> Co-authored-by: Cameron <cameron.clark@hey.com>

…3709) Small perf optimizations around AST builder calls. - AST nodes which end up in `Box`es, allocate into the `Box` as early as possible, to increase chance compiler sees the type can be built directly in arena, rather than built on the stack, and then copied from stack into arena. - Functions return `Box<T>` rather than `T` where the value needs to be boxed anyway. If function is not inlined, this avoids stack allocation + copy. Also, shorten code where possible by using more specific `AstBuilder` methods. In `transform_formal_parameters`, clone the `Box<FormalParameters>` instead of cloning `FormalParameters` on stack and then moving it into a `Box`.

Same as #23709. Small perf optimizations around AST builder calls. - AST nodes which end up in `Box`es, allocate into the `Box` as early as possible, to increase chance compiler sees the type can be built directly in arena, rather than built on the stack, and then copied from stack into arena. - Functions return `Box<T>` rather than `T` where the value needs to be boxed anyway. If function is not inlined, this avoids stack allocation + copy. Also, shorten code where possible by using more specific `AstBuilder` methods.

Same as #23709. Small perf optimizations around AST builder calls. - AST nodes which end up in `Box`es, allocate into the `Box` as early as possible, to increase chance compiler sees the type can be built directly in arena, rather than built on the stack, and then copied from stack into arena. - Functions return `Box<T>` rather than `T` where the value needs to be boxed anyway. If function is not inlined, this avoids stack allocation + copy. Also, shorten code where possible by using more specific `AstBuilder` methods. In `transform_ts_import_equals`, additionally avoid unnecessarily allocating the string `"require"` into arena, by using `static_ident!` instead.

### 💥 BREAKING CHANGES - 94fbacb ast: [**BREAKING**] Only export `AstBuilder` and `NONE` in `builder` module (#23876) (overlookmotel) - 8de5122 ecmascript: [**BREAKING**] Switch to new `AstBuilder` (#23834) (overlookmotel) - dc0ef38 transformer: [**BREAKING**] Switch to new `AstBuilder` (#23831) (overlookmotel) - 88f4455 str: [**BREAKING**] `Str` and `Ident` methods take `&GetAllocator` (#23781) (overlookmotel) - 36009dd allocator: [**BREAKING**] `GetAllocator::allocator` take `&self` (#23676) (overlookmotel) - bd74f9d allocator: [**BREAKING**] Rename `AllocatorAccessor` trait to `GetAllocator` (#23675) (overlookmotel) ### 🚀 Features - 326fe25 transformer_plugins: Support `typeof` `define` keys (#23605) (Alexander Lichter) - f2091b3 ast: Unify old and new `AstBuilder`s (#23875) (overlookmotel) - cd1fd12 codegen: Expose `Codegen::print_string` API (#23785) (camc314) - 785461b ast: Add custom builder methods to AST types (#23651) (overlookmotel) - 05d1357 ast: Add AST creation methods to AST types (#23650) (overlookmotel) - 2580eda str: Add `Str::from_str_in` and `Ident::from_str_in` methods (#23767) (overlookmotel) - 6883fcf minifier: Fold write-once falsy var to false in boolean context (#23540) (Dunqing) - fcbf993 allocator: Add `Vec::from_value_in` method (#23718) (overlookmotel) - 989ddb7 allocator: Add `Vec::from_box_in` method (#23717) (overlookmotel) - 9d1aa7f allocator: Improve `PartialEq` for `Vec` (#23716) (overlookmotel) ### 🐛 Bug Fixes - da0e5bf minifier: Don't reorder a closed-over TDZ read when inlining a var (#23771) (Dunqing) - 0b3021f allocator: Remove `Vec::from_box_in` (#23873) (overlookmotel) - 0ab64ec ast: Silence deprecation warnings within files defining deprecated `AstBuilder` methods (#23889) (overlookmotel) - 8c07cad all: Enable `disable_old_builder` Cargo feature for `oxc_ast` crate in tests (#23888) (overlookmotel) - 3800f01 ast: Legacy `AstBuilder` methods take `self` not `&self` (#23891) (overlookmotel) - 869ac20 semantic/cfg: Connect for update exit to loop test (#23791) (camc314) - d3e92d5 semantic/cfg: Connect while branches from condition exit (#23790) (camc314) - 025045d ast: `ExportNamedDeclaration` plain builder methods return boxed nodes (#23783) (overlookmotel) - 7537c58 ast: Fix name of `AstBuilder` method for `Expression::V8IntrinsicExpression` (#23766) (overlookmotel) - 3f574f5 traverse: Fix unsoundness in `Traverse` walk functions (#23745) (overlookmotel) - 585760f parser: String in AST reference arena (#23721) (overlookmotel) - 7231d55 allocator: Fix unsound lifetime extension in `Box::new_in` (#23685) (overlookmotel) ### ⚡ Performance - d5c916a semantic: Flatten hoisting_variables to avoid per-scope map allocation (#23927) (Lawrence Lin) - e71609d minifier: Bail member-expr folding before the side-effect walk (#23924) (Lawrence Lin) - e1f89ab minifier: Reduce string allocations folding addition (#23846) (overlookmotel) - 9f6ee3b isolated-declarations: Pool scope maps to avoid per-scope alloc/rehash (#23761) (Boshen) - 0b07c4c semantic: Avoid heap alloc for catch-clause binding ids (#23911) (Lawrence Lin) - c5eef8b regular_expression: Skip capturing-group pre-parse when pattern has no `(` (#23908) (Lawrence Lin) - b4f5b4b isolated_declarations: Remove redundant clone of formal parameter pattern (#23912) (Lawrence Lin) - 53d083f isolated_declarations: Use `TakeIn` not `CloneIn` (#23847) (overlookmotel) - 3ea9304 react_compiler: Use faster API to arena allocate strings (#23849) (overlookmotel) - a6d8e45 parser: Avoid span lookup for arrow expression body (#23788) (camc314) - e1886a0 transformer, minifier: Use `static_ident!` macro to create static `Ident`s (#23727) (overlookmotel) - 5527bef transformer/object-rest-spread: Reduce iteration (#23720) (overlookmotel) - 680ffbc transformer: Allocate AST nodes in arena directly (#23711) (overlookmotel) - 1c63c66 parser: Allocate AST nodes in arena directly (#23712) (overlookmotel) - 3855f0c minifier: Allocate AST nodes in arena directly (#23710) (overlookmotel) - d025887 isolated_declarations: Allocate AST nodes in arena directly (#23709) (overlookmotel) - 10b96c6 parser: Remove string search from parsing JSX element name (#23713) (overlookmotel) ### 📚 Documentation - 3d61dea all: Correct capitalization in comments (#23887) (overlookmotel) - aa1ad74 ast: Add `#[deprecated]` to legacy `AstBuilder` methods (#23877) (overlookmotel) - a4676db ast: Correct doc comment for `NONE` (#23765) (overlookmotel) - 419ec80 syntax: Fix typo in doc comment (#23674) (overlookmotel) ### 🛡️ Security - 3cdd18f deps: Update npm packages (#23690) (renovate[bot]) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com> Co-authored-by: Cameron <cameron.clark@hey.com>

overlookmotel mentioned this pull request Jun 22, 2026

refactor(ast): remove AstBuilder::alloc calls #23708

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This was referenced Jun 22, 2026

perf(minifier): allocate AST nodes in arena directly #23710

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perf(transformer): allocate AST nodes in arena directly #23711

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perf(parser): allocate AST nodes in arena directly #23712

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github-actions Bot added the A-isolated-declarations Isolated Declarations label Jun 22, 2026

overlookmotel marked this pull request as ready for review June 22, 2026 12:37

overlookmotel requested a review from Dunqing as a code owner June 22, 2026 12:37

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graphite-app Bot changed the base branch from om/06-21-refactor_ast_remove_astbuilder_alloc_calls to graphite-base/23709 June 22, 2026 12:49

graphite-app Bot force-pushed the graphite-base/23709 branch from c8df7fb to cf5e47e Compare June 22, 2026 12:54

graphite-app Bot force-pushed the om/06-21-perf_isolated_declarations_allocate_ast_nodes_in_arena_directly branch from 538a2ad to 23c2d47 Compare June 22, 2026 12:54

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overlookmotel mentioned this pull request Jun 22, 2026

perf(transformer/object-rest-spread): reduce iteration #23720

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overlookmotel force-pushed the om/06-21-perf_isolated_declarations_allocate_ast_nodes_in_arena_directly branch from 3e5ef15 to 2e9ab4d Compare June 23, 2026 00:31

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oxc-guard Bot mentioned this pull request Jun 29, 2026

release(crates): oxc v0.138.0 #23934

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perf(isolated_declarations): allocate AST nodes in arena directly#23709

perf(isolated_declarations): allocate AST nodes in arena directly#23709
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