perf(minifier): reduce string allocations folding addition#23846
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Dunqing
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Small perf optimization to minifier. In constant-folding pass for addition, we were joining 2 strings together as a `String`, then allocating that string into the arena. Instead, use `Str::from_strs_array_in` to build the concatenated string directly in the arena, avoiding allocating a temporary `String` in the middle.
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Small perf optimization to minifier. In constant-folding pass for addition, we were joining 2 strings together as a `String`, then allocating that string into the arena. Instead, use `Str::from_strs_array_in` to build the concatenated string directly in the arena, avoiding allocating a temporary `String` in the middle.
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linyiru
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Jun 29, 2026
`substitute_template_literal` called `TemplateLiteral::to_js_string`, which builds a transient `std::String` (system allocation), then copied it into the arena via `Str::from_cow_in`. Build the folded string directly in the arena instead: - a single-quasi template (`` `abc` ``) reuses the cooked arena string with no allocation at all; - the general case builds into a pre-sized `ArenaStringBuilder`. Behaviour is identical — same all-or-nothing fold (bails if any quasi/expression isn't stringifiable). Same technique as oxc-project#20386 / oxc-project#23846. `cargo allocs` (system allocations): minifier antd.js 3041 -> 2340 minifier kitchen-sink.tsx 2585 -> 684 minifier checker.ts 162 -> 53 minifier pdf.mjs 2587 -> 2227
linyiru
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Jun 29, 2026
`substitute_template_literal` called `TemplateLiteral::to_js_string`, which builds a transient `std::String` (system allocation), then copied it into the arena via `Str::from_cow_in`. Build the folded string directly in the arena instead: - a single-quasi template (`` `abc` ``) reuses the cooked arena string with no allocation at all; - the general case builds into a pre-sized `ArenaStringBuilder`. Behaviour is identical — same all-or-nothing fold (bails if any quasi/expression isn't stringifiable). Same technique as oxc-project#20386 / oxc-project#23846. `cargo allocs` (system allocations): minifier antd.js 3041 -> 2340 minifier kitchen-sink.tsx 2585 -> 684 minifier checker.ts 162 -> 53 minifier pdf.mjs 2587 -> 2227
linyiru
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Jun 29, 2026
`substitute_template_literal` folded a constant template literal into a string literal by calling `TemplateLiteral::to_js_string`, which builds a transient `std::String` (system allocation), then copied it into the arena via `Str::from_cow_in`. So every folded template paid a system allocation for a string that immediately ends up in the arena anyway. This builds the folded string directly in the arena instead: - a single-quasi template with no interpolations (`` `abc` ``) reuses the cooked arena string directly — no allocation at all; - the general case builds into a pre-sized `ArenaStringBuilder`. Behaviour is identical: the same all-or-nothing fold, byte-identical output. Same technique as oxc-project#20386 / oxc-project#23846, applied to a spot that still went through std::String. `cargo allocs` (minifier system allocations): kitchen-sink.tsx 2576 -> 675 (-74%) antd.js 1040 -> 339 (-701) pdf.mjs 2569 -> 2209 checker.ts 162 -> 53 Arena allocations rise slightly (the intended std::String -> arena trade-off).
camc314
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### 💥 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
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Jul 3, 2026
Small perf optimization to minifier. In constant-folding pass for addition, we were joining 2 strings together as a `String`, then allocating that string into the arena. Instead, use `Str::from_strs_array_in` to build the concatenated string directly in the arena, avoiding allocating a temporary `String` in the middle.
camc314
added a commit
that referenced
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Jul 3, 2026
### 💥 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>
linyiru
added a commit
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Jul 4, 2026
`substitute_template_literal` folded a constant template literal into a string literal by calling `TemplateLiteral::to_js_string`, which builds a transient `std::String` (system allocation), then copied it into the arena via `Str::from_cow_in`. So every folded template paid a system allocation for a string that immediately ends up in the arena anyway. This builds the folded string directly in the arena instead: - a single-quasi template with no interpolations (`` `abc` ``) reuses the cooked arena string directly — no allocation at all; - the general case builds into a pre-sized `ArenaStringBuilder`. Behaviour is identical: the same all-or-nothing fold, byte-identical output. Same technique as oxc-project#20386 / oxc-project#23846, applied to a spot that still went through std::String. `cargo allocs` (minifier system allocations): kitchen-sink.tsx 2576 -> 675 (-74%) antd.js 1040 -> 339 (-701) pdf.mjs 2569 -> 2209 checker.ts 162 -> 53 Arena allocations rise slightly (the intended std::String -> arena trade-off).
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Small perf optimization to minifier.
In constant-folding pass for addition, we were joining 2 strings together as a
String, then allocating that string into the arena.Instead, use
Str::from_strs_array_into build the concatenated string directly in the arena, avoiding allocating a temporaryStringin the middle.