perf: use u32 for string indices in string_wizard and rolldown to reduce memory usage by IWANABETHATGUY · Pull Request #7989 · rolldown/rolldown

IWANABETHATGUY · 2026-01-21T11:22:04Z

Rationale

oxc only supports parsing files up to 4GB, which fits within u32's range
string_wizard is an internal crate used exclusively by rolldown, so we don't need to consider broader scalability concerns

IWANABETHATGUY · 2026-01-21T11:22:20Z

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Copilot

Pull request overview

This PR optimizes performance by changing span-related data structures from usize to u32 throughout the string_wizard crate and its consumers.

Changes:

Changed Span struct and all span-related fields from usize to u32 in the string_wizard crate
Updated all consumer code (plugins, rolldown, rolldown_binding) to cast indices appropriately when calling string_wizard APIs
Modified tests to cast usize values from len() calls to u32 when needed

Reviewed changes

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Show a summary per file

File	Description
crates/string_wizard/src/span.rs	Changed Span tuple fields and methods from usize to u32
crates/string_wizard/src/source_map/locator.rs	Changed line_offsets storage and location tracking to u32
crates/string_wizard/src/source_map/sourcemap_builder.rs	Changed generated code line/column tracking to u32, removed unnecessary casts
crates/string_wizard/src/magic_string/*.rs	Updated all MagicString method signatures to accept u32 indices instead of usize
crates/string_wizard/src/chunk.rs	Changed chunk start/end methods to return u32
crates/rolldown_common/src/css/css_view.rs	Changed at_import_ranges to store (u32, u32) tuples
crates/rolldown/src/css/mod.rs	Added casts when working with oxc Span fields
crates/rolldown_binding/src/types/binding_magic_string.rs	Added casts from usize byte indices to u32 for string_wizard calls
crates/rolldown_plugin_/src/.rs	Added casts from usize or oxc Span to u32 when calling string_wizard APIs
crates/string_wizard/tests/*.rs	Updated test code to cast indices to u32

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github-actions · 2026-01-21T11:40:45Z

Benchmarks Rust

target: main(eb0e97b)
pr: 01-21-perf_use_u32_instead_of_usize_to_store_span_related_data(f3f1545)

group                                                        pr                                     target
-----                                                        --                                     ------
bundle/bundle@multi-duplicated-top-level-symbol              1.00     69.6±1.99ms        ? ?/sec    1.03     71.4±2.47ms        ? ?/sec
bundle/bundle@multi-duplicated-top-level-symbol-sourcemap    1.00     77.0±2.53ms        ? ?/sec    1.01     77.9±2.59ms        ? ?/sec
bundle/bundle@rome_ts                                        1.00    101.2±1.82ms        ? ?/sec    1.03    103.8±1.97ms        ? ?/sec
bundle/bundle@rome_ts-sourcemap                              1.00    112.7±1.79ms        ? ?/sec    1.02    115.2±3.14ms        ? ?/sec
bundle/bundle@threejs                                        1.00     36.7±3.04ms        ? ?/sec    1.01     37.1±0.96ms        ? ?/sec
bundle/bundle@threejs-sourcemap                              1.00     40.6±0.64ms        ? ?/sec    1.05     42.8±0.99ms        ? ?/sec
bundle/bundle@threejs10x                                     1.00    369.6±4.30ms        ? ?/sec    1.02    378.8±6.83ms        ? ?/sec
bundle/bundle@threejs10x-sourcemap                           1.00    425.5±4.05ms        ? ?/sec    1.03    436.5±5.37ms        ? ?/sec
scan/scan@rome_ts                                            1.00     82.5±1.64ms        ? ?/sec    1.00     82.8±2.38ms        ? ?/sec
scan/scan@threejs                                            1.03     29.3±1.90ms        ? ?/sec    1.00     28.4±0.48ms        ? ?/sec
scan/scan@threejs10x                                         1.00    288.6±4.04ms        ? ?/sec    1.01    292.9±5.91ms        ? ?/sec

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IWANABETHATGUY · 2026-01-21T17:21:01Z

Merge activity

Jan 21, 5:21 PM UTC: The merge label 'graphite: merge-when-ready' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Jan 21, 6:13 PM UTC: IWANABETHATGUY added this pull request to the Graphite merge queue.
Jan 21, 6:22 PM UTC: Merged by the Graphite merge queue.

Copilot

Pull request overview

Copilot reviewed 32 out of 32 changed files in this pull request and generated 6 comments.

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crates/string_wizard/src/magic_string/mod.rs

crates/string_wizard/src/magic_string/slice.rs

crates/string_wizard/src/magic_string/movement.rs

crates/string_wizard/src/magic_string/reset.rs

crates/string_wizard/src/magic_string/mod.rs

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Pull request overview

Copilot reviewed 32 out of 32 changed files in this pull request and generated 1 comment.

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crates/string_wizard/tests/magic_string_source_map.rs

…uce memory usage (#7989) ## Rationale - oxc only supports parsing files up to 4GB, which fits within `u32`'s range - `string_wizard` is an internal crate used exclusively by rolldown, so we don't need to consider broader scalability concerns

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@IWANABETHATGUY

## [1.0.0-rc.1] - 2026-01-22 ### 🚀 Features - debug_info: add facade chunk elimination reason (#7980) by @IWANABETHATGUY - support lazy barrel optimization (#7933) by @shulaoda - add `experimental.lazyBarrel` option (#7908) by @shulaoda - skip unused external modules from IIFE parameter list (#7978) by @sapphi-red - add custom panic hook for better crash reporting (#7752) by @shulaoda - treeshake: add `invalidImportSideEffects` option (#7958) by @shulaoda - merge allow-extension emitted chunks (#7940) by @IWANABETHATGUY - nativeMagicString generateMap (#7944) by @IWANABETHATGUY - Include meta.magicString in RenderChunkMeta (#7943) by @IWANABETHATGUY - debug_info: add debug info for eliminated facade chunks (#7946) by @IWANABETHATGUY - stablize `strictExecutionOrder` and move to `output.strictExecutionOrder` from `experimental.strictExecutionOrder` (#7901) by @sapphi-red - add documentation link to require() error message (#7898) by @Copilot - add `codeSplitting: boolean` and deprecate `inlineDynamicImports` (#7870) by @hyf0 - dev: change lazy module URL to `/@vite/lazy` from `/lazy` (#7884) by @sapphi-red ### 🐛 Bug Fixes - transform JS files containing `</script>` to escape template literals (#7987) by @IWANABETHATGUY - apply avoid-breaking-exported-api = false to clippy.toml and fix clippy errors (#7982) by @Boshen - pass `kind` from `this.resolve` (#7981) by @sapphi-red - rolldown_plugin_vite_resolve: ignore yarn resolution errors and fallback to other resolvers (#7968) by @sapphi-red - renamer: prevent renaming symbols when there no conflicts (#7936) by @Dunqing - correct minifyInterExports when emitted chunk got merged (#7941) by @IWANABETHATGUY - deduplicate entry points when module is both emitted and dynamically imported (#7885) by @IWANABETHATGUY - dev: add `@vite-ignore` to lazy compilation proxy module import (#7883) by @sapphi-red ### 🚜 Refactor - rust: enable clippy nursery lint group (#8002) by @Boshen - rust: fix inconsistent_struct_constructor clippy lint (#7999) by @Boshen - rust: fix needless_pass_by_ref_mut clippy lint (#7994) by @Boshen - rust: fix unnecessary_wraps clippy lint (#7993) by @Boshen - rust: fix enum_variant_names clippy lint (#7992) by @Boshen - fix single_match clippy lint (#7997) by @Boshen - rust: fix redundant_clone clippy lint (#7996) by @Boshen - rust: rename CJS to Cjs to follow upper_case_acronyms lint (#7991) by @Boshen - rust: remove unnecessary Box wrapper around Vec in MemberExprRef (#7990) by @Boshen - import_record: make resolved_module optional (#7907) by @shulaoda - remove unnecessary `.parse` (#7966) by @sapphi-red - remove unused `ImportRecordMeta::IsPlainImport` (#7948) by @shulaoda - proper set chunk meta (#7939) by @IWANABETHATGUY - module_loader: remove `try_spawn_with_cache` (#7920) by @shulaoda - link_stage: simplify `ImportStatus::NoMatch` to unit variant (#7909) by @shulaoda - improve global scope symbol reservation in chunk deconfliction (#7906) by @IWANABETHATGUY - simplify ast unwrapping in generate stage (#7900) by @IWANABETHATGUY - generate_stage: optimize cross-chunk imports computation (#7889) by @shulaoda - link_stage: move runtime require logic into match branch (#7892) by @shulaoda - link_stage: simplify runtime require reference conditions (#7891) by @shulaoda - link_stage: inline and simplify external dynamic import check (#7890) by @shulaoda - generate_stage: simplify external module import collection logic (#7887) by @shulaoda - avoid redundant module lookup in TLA computation (#7886) by @shulaoda - dev: `devEngine.compileEntry` does not return null (#7882) by @sapphi-red - dev: fix type errors for test HMR runtime (#7881) by @sapphi-red - dev: move `clientId` property to `DevRuntime` base class (#7880) by @sapphi-red - dev: generate client id in browser (#7878) by @hyf0 ### 📚 Documentation - apis: organize hook filters documentation and add composable filters section (#8003) by @sapphi-red - update `vitepress-plugin-group-icons` (#7947) by @yuyinws - add in-depth documentation for lazy barrel optimization (#7969) by @shulaoda - bump theme & update activeMatch for reference (#7963) by @mdong1909 - mark `build()` API as experimental (#7954) by @sapphi-red - enhance search functionality with improved scoring and filtering logic (#7935) by @hyf0 - add minor comments to multiple types (#7930) by @sapphi-red - refactor advanedChunks related content to adapt manual code splitting concept (#7925) by @hyf0 - apis: add content to Bundler API page (#7926) by @sapphi-red - apis: restructure plugin API related docs (#7924) by @sapphi-red - add plugin API docs (#7923) by @sapphi-red - apis: add docs to important APIs (#7913) by @sapphi-red - move the important APIs to the top of the sidebar (#7912) by @sapphi-red - apis: add more content to CLI documentation (#7911) by @sapphi-red - apis: generate CLI docs from --help output (#7910) by @sapphi-red - add fathom analytics (#7896) by @mdong1909 ### ⚡ Performance - use u32 for string indices in string_wizard and rolldown to reduce memory usage (#7989) by @IWANABETHATGUY - rust: remove all usages of `with_scope_tree_child_ids(true)` for `SemanticBuilder` (#7995) by @Dunqing - renamer: skip unnecessary nested scope symbol processing (#7899) by @Dunqing - module_loader: use ArcStr for importer_id to avoid string copy (#7922) by @shulaoda - module_loader: defer `ModuleTaskOwner` construction until needed (#7921) by @shulaoda - renamer: optimize symbol renaming by eliminating `rename_non_root_symbol` pass (#7867) by @Dunqing ### 🧪 Testing - add lazy barrel optimization test cases (#7967) by @shulaoda ### ⚙️ Miscellaneous Tasks - remove lazy barrel option (#8010) by @shulaoda - mark watch API as experimental (#8004) by @sapphi-red - deps: update dependency lodash-es to v4.17.23 [security] (#8001) by @renovate[bot] - git ignore zed local config (#7988) by @IWANABETHATGUY - setup publint for published packages (#7972) by @Copilot - enable `tagged_template_transform ` uncondionally (#7975) by @IWANABETHATGUY - deps: update oxc to v0.110.0 (#7964) by @renovate[bot] - deps: update oxc apps (#7962) by @renovate[bot] - ai: add upgrade-oxc Claude skill (#7957) by @Boshen - deps: update rollup submodule for tests to v4.55.2 (#7959) by @sapphi-red - deps: update test262 submodule for tests (#7960) by @sapphi-red - deps: update crate-ci/typos action to v1.42.1 (#7961) by @renovate[bot] - deps: update rust crates (#7951) by @renovate[bot] - deps: update npm packages (#7953) by @renovate[bot] - deps: update github-actions (#7952) by @renovate[bot] - deps: update npm packages (#7950) by @renovate[bot] - format magic-string test before write to disk (#7945) by @IWANABETHATGUY - deps: update dependency rolldown-plugin-dts to ^0.21.0 (#7915) by @renovate[bot] - deps: update dependency oxlint-tsgolint to v0.11.1 (#7914) by @renovate[bot] - deps: update dependency diff to v8.0.3 [security] (#7904) by @renovate[bot] - remove outdated TODO comment in `collect_depended_symbols` (#7888) by @shulaoda - deps: update oxc resolver to v11.16.3 (#7876) by @renovate[bot]

github-actions bot assigned IWANABETHATGUY Jan 21, 2026

IWANABETHATGUY marked this pull request as ready for review January 21, 2026 11:25

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IWANABETHATGUY changed the title ~~perf: use u32 instead of usize to store span related data~~ fix: use u32 for string indices in string_wizard and rolldown Jan 21, 2026

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IWANABETHATGUY force-pushed the 01-21-perf_use_u32_instead_of_usize_to_store_span_related_data branch from 53fd067 to dcf13a6 Compare January 21, 2026 12:03

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IWANABETHATGUY marked this pull request as draft January 21, 2026 13:32

IWANABETHATGUY force-pushed the 01-21-perf_use_u32_instead_of_usize_to_store_span_related_data branch from 737ca26 to 4ee3e76 Compare January 21, 2026 17:00

IWANABETHATGUY changed the title ~~fix: use u32 for string indices in string_wizard and rolldown~~ perf: use u32 for string indices in string_wizard and rolldown to reduce memory usage Jan 21, 2026

IWANABETHATGUY force-pushed the 01-21-perf_use_u32_instead_of_usize_to_store_span_related_data branch from 4ee3e76 to f3f1545 Compare January 21, 2026 17:19

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crates/string_wizard/tests/magic_string_source_map.rs Outdated Show resolved Hide resolved

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release: v1.0.0-rc.1 #8011

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