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

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perf(transformer/object-rest-spread): reduce iteration#23720
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@overlookmotel overlookmotel commented Jun 22, 2026 •
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Small perf optimization to object rest/spread transform.

Previously we called bound_names on a VariableDeclaration, which loops through all its VariableDeclarators, processing each's id: BindingPattern. But we just created the VariableDeclaration with a single declarator. Just call bound_names directly on the BindingPattern, to avoid the unnecessary loop.

This was referenced Jun 22, 2026
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@overlookmotel overlookmotel mentioned this pull request Jun 22, 2026
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@github-actions github-actions Bot added the A-transformer Area - Transformer / Transpiler label Jun 22, 2026
@overlookmotel overlookmotel marked this pull request as ready for review June 22, 2026 14:45
@overlookmotel overlookmotel requested a review from Dunqing as a code owner June 22, 2026 14:45
Copilot AI review requested due to automatic review settings June 22, 2026 14:45
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Merging this PR will not alter performance

✅ 52 untouched benchmarks
⏩ 19 skipped benchmarks1

Comparing om/06-21-perf_transformer_object-rest-spread_reduce_iteration (3a989d8) with om/06-21-perf_transformer_allocate_ast_nodes_in_arena_directly (a231889)2

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Footnotes

  1. 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. ↩

  2. No successful run was found on om/06-21-perf_transformer_allocate_ast_nodes_in_arena_directly (55fd31d) during the generation of this report, so 1af8e94 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

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Pull request overview

This PR makes a small performance optimization in the ES2018 object rest/spread transformer by avoiding an unnecessary iteration when updating symbol flags for a newly created temporary binding.

Changes:

  • Call bound_names directly on the single BindingPattern (id) instead of on a freshly constructed VariableDeclaration that only contains one declarator.
  • Reorder construction so symbol-flag updates happen before allocating the VariableDeclaration, removing the now-unneeded temporary decl local.

@overlookmotel overlookmotel force-pushed the om/06-21-perf_transformer_object-rest-spread_reduce_iteration branch from e6a661d to 7b70fe5 Compare June 22, 2026 14:59
@overlookmotel overlookmotel force-pushed the om/06-21-perf_transformer_allocate_ast_nodes_in_arena_directly branch from 8d8dbf2 to a231889 Compare June 22, 2026 14:59
@overlookmotel overlookmotel force-pushed the om/06-21-perf_transformer_object-rest-spread_reduce_iteration branch from 7b70fe5 to 3a989d8 Compare June 23, 2026 00:31
@overlookmotel overlookmotel force-pushed the om/06-21-perf_transformer_allocate_ast_nodes_in_arena_directly branch from a231889 to 55fd31d Compare June 23, 2026 00:31
This was referenced Jun 23, 2026
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@overlookmotel overlookmotel added the 0-merge Merge with Graphite Merge Queue label Jun 23, 2026
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overlookmotel commented Jun 23, 2026 •
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@overlookmotel
perf(transformer/object-rest-spread): reduce iteration (#23720)
5527bef 
Small perf optimization to object rest/spread transform.

Previously we called `bound_names` on a `VariableDeclaration`, which loops through all its `VariableDeclarator`s, processing each's `id: BindingPattern`. But we just created the `VariableDeclaration` with a single declarator. Just call `bound_names` directly on the `BindingPattern`, to avoid the unnecessary loop.
@graphite-app graphite-app Bot force-pushed the om/06-21-perf_transformer_allocate_ast_nodes_in_arena_directly branch from 55fd31d to 680ffbc Compare June 23, 2026 01:02
@graphite-app graphite-app Bot force-pushed the om/06-21-perf_transformer_object-rest-spread_reduce_iteration branch from 3a989d8 to 5527bef Compare June 23, 2026 01:02
@graphite-app graphite-app Bot removed the 0-merge Merge with Graphite Merge Queue label Jun 23, 2026
Base automatically changed from om/06-21-perf_transformer_allocate_ast_nodes_in_arena_directly to main June 23, 2026 01:07
@graphite-app graphite-app Bot merged commit 5527bef into main Jun 23, 2026
31 checks passed
@graphite-app graphite-app Bot deleted the om/06-21-perf_transformer_object-rest-spread_reduce_iteration branch June 23, 2026 01:07
@oxc-guard oxc-guard Bot mentioned this pull request Jun 29, 2026
Merged
camc314 added a commit that referenced this pull request Jun 29, 2026
@oxc-guard @Boshen @camc314
release(crates): oxc v0.138.0 (#23934)
8bf69a3 
### 💥 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>
camc314 pushed a commit that referenced this pull request Jul 3, 2026
@overlookmotel @camc314
perf(transformer/object-rest-spread): reduce iteration (#23720)
21eaa19 
Small perf optimization to object rest/spread transform.

Previously we called `bound_names` on a `VariableDeclaration`, which loops through all its `VariableDeclarator`s, processing each's `id: BindingPattern`. But we just created the `VariableDeclaration` with a single declarator. Just call `bound_names` directly on the `BindingPattern`, to avoid the unnecessary loop.
camc314 added a commit that referenced this pull request Jul 3, 2026
@oxc-guard @Boshen @camc314
release(crates): oxc v0.138.0 (#23934)
3ab7388 
### 💥 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>
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