perf(rolldown): some minor perf optimization found by autoresearch by Brooooooklyn · Pull Request #8730 · rolldown/rolldown

Brooooooklyn · 2026-03-16T03:29:11Z

Note

Medium Risk
Touches collapse_sourcemaps, which is used in chunk rendering/minification; incorrect source_id propagation could subtly break sourcemap fidelity even though the change is small and performance-motivated.

Overview
Optimizes sourcemap processing by removing rustc-hash/rolldown_utils dependencies and simplifying collapse_sourcemaps to pass through source_id directly instead of remapping via cached hash maps.

Also swaps newline counting in SourceMapSource to use memchr::memchr_iter for faster \n scanning.

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Brooooooklyn · 2026-03-16T03:29:27Z

perf(rolldown): some minor perf optimization found by autoresearch #8730 👈 (View in Graphite)
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Copilot

Pull request overview

This PR targets minor performance optimizations in rolldown_sourcemap’s collapse_sourcemaps implementation by removing hash-map based source ID remapping and introducing parallel processing over tokens, along with dropping the direct rustc-hash dependency from this crate.

Changes:

Parallelize token processing in collapse_sourcemaps using rolldown_utils::rayon.
Simplify source ID handling by using original_token.get_source_id() directly (removing source-index remapping/caching).
Remove rustc-hash from crates/rolldown_sourcemap dependencies (and update Cargo.lock).

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 1 comment.

File	Description
crates/rolldown_sourcemap/src/lib.rs	Switches `collapse_sourcemaps` token traversal to rayon and removes source-id remapping logic.
crates/rolldown_sourcemap/Cargo.toml	Drops `rustc-hash` dependency for this crate.
Cargo.lock	Updates lockfile to reflect removed dependency.

crates/rolldown_sourcemap/src/lib.rs

cursor

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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crates/rolldown_sourcemap/src/lib.rs

Copilot

Pull request overview

This PR targets small performance improvements in rolldown by optimizing sourcemap collapsing and adjusting a JSX parsing flag used during chunk minification.

Changes:

Parallelize token processing in rolldown_sourcemap::collapse_sourcemaps and remove rustc-hash usage from rolldown_sourcemap.
Optimize newline counting in rolldown_sourcemap with memchr_iter.
Make minify-stage JSX parsing conditional on transform_options.is_jsx_preserve().

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
crates/rolldown_sourcemap/src/source.rs	Switch newline counting to `memchr_iter` for simpler/faster scanning.
crates/rolldown_sourcemap/src/lib.rs	Parallelize collapse token mapping and remove hash-based source-id remapping/cache.
crates/rolldown_sourcemap/Cargo.toml	Drop `rustc-hash` dependency from `rolldown_sourcemap`.
crates/rolldown/src/stages/generate_stage/minify_chunks.rs	Make JSX parsing toggle depend on `is_jsx_preserve()`.
Cargo.lock	Remove `rustc-hash` from the resolved dependency set for `rolldown_sourcemap`.

Comments suppressed due to low confidence (1)

crates/rolldown_sourcemap/src/lib.rs:90

par_bridge() produces an unindexed ParallelIterator, so the subsequent collect::<Vec<_>>() does not guarantee preserving the original token order. Sourcemap token ordering is typically required to be sorted by (dst_line, dst_col) for correct lookup/serialization and for deterministic output; collecting in parallel here can silently scramble ordering. Consider switching to an indexed parallel iterator (e.g. collect tokens first then into_par_iter()), or sort the resulting tokens by destination position before constructing the SourceMap.

  let tokens = last_map
    .get_source_view_tokens()
    .par_bridge()
    .filter_map(|token| {
      let original_token = sourcemap_and_lookup_table.iter().rev().try_fold(
        token,
        |token, (sourcemap, lookup_table)| {
          sourcemap.lookup_source_view_token(
            lookup_table,
            token.get_src_line(),
            token.get_src_col(),
          )
        },
      );
      original_token.map(|original_token| {
        Token::new(
          token.get_dst_line(),
          token.get_dst_col(),
          original_token.get_src_line(),
          original_token.get_src_col(),
          original_token.get_source_id(),
          original_token.get_name_id(),
        )
      })
    })
    .collect::<Vec<_>>();

Copilot

Pull request overview

This PR aims to improve build performance by streamlining sourcemap collapsing and reducing unnecessary work during minification (notably around line counting and JSX parsing mode selection).

Changes:

Optimizes newline counting in SourceMapSource by switching to memchr_iter.
Simplifies collapse_sourcemaps by removing rustc-hash-based source remapping/cache and directly forwarding source/name IDs from the folded token.
Adjusts chunk minification to enable JSX parsing only when transform_options.is_jsx_preserve() is set, and removes rustc-hash from rolldown_sourcemap dependencies.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
crates/rolldown_sourcemap/src/source.rs	Uses `memchr_iter` for faster newline counting.
crates/rolldown_sourcemap/src/lib.rs	Removes `FxHashMap` remapping/cache in `collapse_sourcemaps`; forwards `source_id` directly.
crates/rolldown_sourcemap/Cargo.toml	Drops `rustc-hash` dependency from the sourcemap crate.
crates/rolldown/src/stages/generate_stage/minify_chunks.rs	Makes JSX parsing in minifier conditional on `is_jsx_preserve()`.
Cargo.lock	Updates lockfile to reflect removed `rustc-hash` dependency.

Comments suppressed due to low confidence (1)

crates/rolldown_sourcemap/src/lib.rs:88

The PR description mentions collapsing sourcemaps by processing tokens in parallel and re-sorting tokens for deterministic output. In the current implementation here, tokens are processed sequentially via get_source_view_tokens().filter_map(...).collect::<Vec<_>>() and there is no explicit re-sort step. If the description is meant to reflect the final behavior, either update the implementation or adjust the PR description to match what’s actually shipped.

  let tokens = last_map
    .get_source_view_tokens()
    .filter_map(|token| {
      let original_token = sourcemap_and_lookup_table.iter().rev().try_fold(
        token,
        |token, (sourcemap, lookup_table)| {
          sourcemap.lookup_source_view_token(
            lookup_table,
            token.get_src_line(),
            token.get_src_col(),
          )
        },
      );
      original_token.map(|original_token| {
        Token::new(
          token.get_dst_line(),
          token.get_dst_col(),
          original_token.get_src_line(),
          original_token.get_src_col(),
          original_token.get_source_id(),
          original_token.get_name_id(),
        )
      })
    })
    .collect::<Vec<_>>();

crates/rolldown/src/stages/generate_stage/minify_chunks.rs

crates/rolldown_sourcemap/src/lib.rs

crates/rolldown/src/stages/generate_stage/minify_chunks.rs

github-actions · 2026-03-16T04:10:18Z

Benchmarks Rust

target: main(2a906e6)
pr: perf/claude-code-autoresearch(308427e)

group                                                        pr                                     target
-----                                                        --                                     ------
bundle/bundle@multi-duplicated-top-level-symbol              1.00     66.1±2.13ms        ? ?/sec    1.02     67.2±3.47ms        ? ?/sec
bundle/bundle@multi-duplicated-top-level-symbol-sourcemap    1.00     74.8±2.19ms        ? ?/sec    1.00     74.5±1.68ms        ? ?/sec
bundle/bundle@rome_ts                                        1.00    146.5±7.18ms        ? ?/sec    1.03    151.3±5.95ms        ? ?/sec
bundle/bundle@rome_ts-sourcemap                              1.00    167.4±6.58ms        ? ?/sec    1.02    170.8±6.80ms        ? ?/sec
bundle/bundle@threejs                                        1.07     67.5±4.34ms        ? ?/sec    1.00     63.0±2.45ms        ? ?/sec
bundle/bundle@threejs-sourcemap                              1.01     74.3±3.24ms        ? ?/sec    1.00     73.3±3.56ms        ? ?/sec
bundle/bundle@threejs10x                                     1.02   733.0±10.24ms        ? ?/sec    1.00   716.8±11.12ms        ? ?/sec
bundle/bundle@threejs10x-sourcemap                           1.02   835.9±10.07ms        ? ?/sec    1.00    820.0±8.70ms        ? ?/sec

codspeed-hq · 2026-03-16T04:18:37Z

Merging this PR will not alter performance

✅ 6 untouched benchmarks
⏩ 8 skipped benchmarks¹

_{Comparing perf/claude-code-autoresearch (308427e) with main (2a906e6)²}

8 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. ↩
No successful run was found on main (308427e) during the generation of this report, so 2a906e6 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

Brooooooklyn · 2026-03-16T06:46:20Z

It's not too much, but it's worth taking a look

graphite-app · 2026-03-16T08:50:04Z

Merge activity

Mar 16, 8:50 AM UTC: Brooooooklyn added this pull request to the Graphite merge queue.
Mar 16, 8:55 AM UTC: Merged by the Graphite merge queue.

…8730)  > [!NOTE] > **Medium Risk** > Touches `collapse_sourcemaps`, which is used in chunk rendering/minification; incorrect `source_id` propagation could subtly break sourcemap fidelity even though the change is small and performance-motivated. > > **Overview** > **Optimizes sourcemap processing** by removing `rustc-hash`/`rolldown_utils` dependencies and simplifying `collapse_sourcemaps` to pass through `source_id` directly instead of remapping via cached hash maps. > > Also swaps newline counting in `SourceMapSource` to use `memchr::memchr_iter` for faster `\n` scanning. > > <sup>Written by [Cursor Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit 56cddc8. This will update automatically on new commits. Configure [here](https://cursor.com/dashboard?tab=bugbot).</sup>

socket-security · 2026-03-16T08:50:52Z

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	util-deprecate@1.0.2
	source-map-js@1.2.1
	pathe@2.0.3
	signal-exit@4.1.0
	source-map-support@0.5.21
	picomatch@4.0.3
	terser@5.46.0
	ws@8.19.0
	semver@7.7.4
	typescript@5.9.3

View full report

@IWANABETHATGUY

## [1.0.0-rc.10] - 2026-03-18 ### 🚀 Features - add indentExclusionRanges property to MagicString (#8746) by @IWANABETHATGUY - expose `oxcRuntimePlugin` (#8654) by @sapphi-red - rust: make bundler generic over FileSystem for in-memory benchmarks (#8652) by @Boshen ### 🐛 Bug Fixes - rolldown_plugin_vite_dynamic_import_vars: align dynamic import fast check with Vite (#8760) by @shulaoda - renamer: handle existing bindings in nested scopes when finding unique names (#8741) by @drewolson - pass `yarn_pnp` option where needed (#8736) by @sapphi-red - preserve optional chaining in namespace member expr rewrite (#8712) by @Copilot - correct UTF-16 index handling in native MagicString (#8693) by @IWANABETHATGUY - mark failing doctests as ignore (#8700) by @Boshen - prevent may_partial_namespace from leaking through include_module (#8682) by @IWANABETHATGUY - ci: bump native-build cache key to invalidate stale napi-rs artifacts (#8678) by @Boshen - `comments.annotation: false` breaking tree-shaking (#8657) by @IWANABETHATGUY - validate filenames for NUL bytes from chunkFileNames/entryFileNames (#8644) by @IWANABETHATGUY - dce-only minify should not set NODE_ENV to production (#8651) by @IWANABETHATGUY ### 🚜 Refactor - rust: remove dead `CrossModuleOptimizationConfig::side_effects_free_function_optimization` (#8673) by @Dunqing - rust: simplify `cross_module_optimization` by removing redundant scope tracking (#8672) by @Dunqing - simplify string repeat in guess_indentor (#8753) by @IWANABETHATGUY - consolidate custom magic-string tests into one file (#8696) by @IWANABETHATGUY - extract CJS bailout checks from include_symbol (#8683) by @IWANABETHATGUY - rust: remove `BindingIdentifierExt` to use `BindingIdentifier::symbol_id()` instead (#8667) by @Dunqing - bench: add bench_preset helper and inline presets (#8658) by @Boshen - rust: filter external modules from entries instead of mapping bit positions (#8637) by @Dunqing ### 📚 Documentation - clarify watch mode behavior and its limitations (#8751) by @sapphi-red - add external link icon to GitHub button in Hero section (#8731) by @thisisnkc - guide: clarify that `inject` option is only conceptually similar to esbuild's one (#8743) by @sapphi-red - meta/design: add `devtools.md` (#8663) by @hyf0 - add viteplus alpha announcement banner (#8668) by @shulaoda ### ⚡ Performance - rolldown: some minor perf optimization found by autoresearch (#8730) by @Brooooooklyn - replace Vec allocation with lazy iterator in find_hash_placeholders (#8703) by @Boshen - replace TypedDashMap with TypedMap in CustomField (#8708) by @Boshen - bench: remove scan benchmark binary to halve LTO link time (#8694) by @Boshen ### 🧪 Testing - watch: increase timeout for error output (#8766) by @sapphi-red - vite-tests: remove JS plugin tests (#8767) by @sapphi-red - watch: add CLI exit code test (#8752) by @sapphi-red - normalize paths on Windows even if `resolve.symlinks` is false (#8483) by @sapphi-red ### ⚙️ Miscellaneous Tasks - correct comment in bundle-analyzer-plugin.ts (#8770) by @origami-z - upgrade oxc to 0.120.0 (#8764) by @Boshen - enable all test for `reset` category in MagicString.test.ts (#8749) by @IWANABETHATGUY - deps: update test262 submodule for tests (#8742) by @sapphi-red - deps: update oxc apps (#8734) by @renovate[bot] - deps: update softprops/action-gh-release action to v2.6.1 (#8724) by @renovate[bot] - deps: update npm packages (major) (#8722) by @renovate[bot] - deps: update github-actions (major) (#8721) by @renovate[bot] - deps: update softprops/action-gh-release action to v2.6.0 (#8720) by @renovate[bot] - deps: update npm packages (#8718) by @renovate[bot] - deps: update rust crates (#8717) by @renovate[bot] - deps: update github-actions (#8716) by @renovate[bot] - deps: update dependency oxlint-tsgolint to v0.17.0 (#8713) by @renovate[bot] - deps: bump cargo-shear to v1.11.2 (#8711) by @Boshen - use org level `CODE_OF_CONDUCT.md` (#8706) by @sapphi-red - fix cache key mismatch and remove redundant cache saves (#8695) by @Boshen - deps: update oxc apps (#8692) by @renovate[bot] - deps: update oxc apps (#8649) by @renovate[bot] - should do matrix out side of reusable workflows 2 (#8691) by @hyf0 - should do matrix out side of reusable workflows (#8690) by @hyf0 - deps: update dependency rolldown-plugin-dts to v0.22.5 (#8689) by @renovate[bot] - upgrade oxc to 0.119.0 and oxc_resolver to 11.19.1 (#8686) by @Boshen - correct if condition of `type-check` job (#8677) by @hyf0 - Gate CI type-check job on node changes (#8669) by @Copilot - benchmark: improve codspeed build (#8665) by @Boshen - deps: update oxc to v0.118.0 (#8650) by @renovate[bot] - deps: update crate-ci/typos action to v1.44.0 (#8647) by @renovate[bot] - deps: update oxc resolver to v11.19.1 (#8646) by @renovate[bot] - deps: update dependency rust to v1.94.0 (#8648) by @renovate[bot] - deps: update dependency rolldown-plugin-dts to v0.22.4 (#8645) by @renovate[bot] ### ◀️ Revert - Revert "ci: Gate CI type-check job on node changes" (#8674) by @hyf0 - "chore(deps): update dependency rust to v1.94.0 (#8648)" (#8660) by @shulaoda ### ❤️ New Contributors * @origami-z made their first contribution in [#8770](#8770) * @drewolson made their first contribution in [#8741](#8741) * @thisisnkc made their first contribution in [#8731](#8731) Co-authored-by: shulaoda <165626830+shulaoda@users.noreply.github.com>

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This was referenced Mar 18, 2026

release: v1.0.0-rc.10 #8759

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release: v1.0.0-rc.10 #8774

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Merging this PR will not alter performance

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