fix: optimize chunk merging for shared entry points by IWANABETHATGUY · Pull Request #7194 · rolldown/rolldown

IWANABETHATGUY · 2025-11-22T10:14:15Z

related to #4904

IWANABETHATGUY · 2025-11-22T10:14:30Z

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github-actions · 2025-11-22T10:30:22Z

Benchmarks Rust

target: main(6dc1191)
pr: 11-20-feat_4904(5208010)

group                                                        pr                                     target
-----                                                        --                                     ------
bundle/bundle@multi-duplicated-top-level-symbol              1.03     67.9±2.37ms        ? ?/sec    1.00     65.7±1.56ms        ? ?/sec
bundle/bundle@multi-duplicated-top-level-symbol-sourcemap    1.03     74.8±1.48ms        ? ?/sec    1.00     72.9±1.28ms        ? ?/sec
bundle/bundle@rome_ts                                        1.01    109.6±2.04ms        ? ?/sec    1.00    108.9±1.51ms        ? ?/sec
bundle/bundle@rome_ts-sourcemap                              1.00    123.0±3.90ms        ? ?/sec    1.00    122.6±1.85ms        ? ?/sec
bundle/bundle@threejs                                        1.00     40.2±2.71ms        ? ?/sec    1.01     40.7±2.34ms        ? ?/sec
bundle/bundle@threejs-sourcemap                              1.00     43.1±0.57ms        ? ?/sec    1.01     43.6±0.53ms        ? ?/sec
bundle/bundle@threejs10x                                     1.00    399.2±5.42ms        ? ?/sec    1.00    399.7±6.00ms        ? ?/sec
bundle/bundle@threejs10x-sourcemap                           1.00    457.8±4.49ms        ? ?/sec    1.00    459.3±4.35ms        ? ?/sec
scan/scan@rome_ts                                            1.03     87.0±1.73ms        ? ?/sec    1.00     84.7±1.45ms        ? ?/sec
scan/scan@threejs                                            1.02     28.9±0.43ms        ? ?/sec    1.00     28.3±0.38ms        ? ?/sec
scan/scan@threejs10x                                         1.01    302.0±5.88ms        ? ?/sec    1.00    298.3±5.84ms        ? ?/sec

Copilot

Pull request overview

This PR optimizes chunk generation by merging shared chunks into entry chunks when one entry imports another, reducing the total number of output chunks. The optimization applies to deduplicated entry points (multiple entries with the same source file) and scenarios where entry modules have import relationships.

Key changes:

Modified chunk merging logic to detect when one user-defined entry imports all other entries sharing common modules
Changed imports_from_other_chunks from Vec to FxIndexMap for efficient deduplication and lookup
Moved entry_module_to_entry_chunk assignment earlier in the flow to support the new merging logic

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
crates/rolldown/src/stages/generate_stage/code_splitting.rs	Added new logic to merge shared chunks into entry chunks when one entry imports all others; moved entry_module_to_entry_chunk assignment
crates/rolldown_common/src/chunk/mod.rs	Changed imports_from_other_chunks from Vec to FxIndexMap for O(1) lookups and deduplication
crates/rolldown/src/stages/generate_stage/compute_cross_chunk_links.rs	Updated to merge pre-existing imports_from_other_chunks entries with newly computed ones
packages/rolldown/tests/fixtures/input/deduplicate/named-entry/_config.ts	Updated test expectation: 2 chunks instead of 3 (shared chunk merged into entry)
packages/rolldown/tests/fixtures/input/deduplicate/emit-file2/_config.ts	Updated test expectation: 2 chunks instead of 3
packages/rolldown/tests/fixtures/plugin/context/emit-chunk/_config.ts	Updated hash in snapshot due to changed chunk content
crates/rolldown/tests/snapshots/integration_rolldown__filename_with_hash.snap	Updated hashes for multiple test cases reflecting optimized chunk merging
crates/rolldown/tests/rolldown/semantic/export_star_from_external_as_shared_entries_cjs/artifacts.snap	Demonstrates chunk merging: entry2 now requires entry.js instead of separate main.js
crates/rolldown/tests/rolldown/semantic/export_star_from_external_as_shared_entries/artifacts.snap	ESM equivalent of above optimization
crates/rolldown/tests/rolldown/misc/preserve_entry_signature/issue-4880/artifacts.snap	Shows removal of shared foo22.js chunk, merged into foo2.js
crates/rolldown/tests/rolldown/misc/cjs_entry_as_dependency/artifacts.snap	Demonstrates merging of main22.js into main2.js
crates/rolldown/tests/rolldown/misc/assign_chunk_name_order/artifacts.snap	Shows removal of intermediate shared file2.js chunk
crates/rolldown/tests/rolldown/issues/5011/artifacts.snap	Demonstrates removal of after-preload-dynamic2.js shared chunk
crates/rolldown/tests/rolldown/function/format/cjs/share_chunk_without_symbol/artifacts.snap	Shows merging of main.js into entry1.js for CJS format
crates/rolldown/tests/rolldown/function/experimental/strict_execution_order/ensure_lazy_module_eval/artifacts.snap	Demonstrates removal of dynamic2.js shared chunk
crates/rolldown/tests/rolldown/code_splitting/ensure_side_effect_executed/artifacts.snap	Shows merging of entry.js into entry_js.js
crates/rolldown/tests/rolldown/cjs_compat/multiple_circle_cjs_entries/artifacts.snap	Demonstrates handling of circular CJS entries with chunk merging
crates/rolldown/tests/esbuild/default/duplicate_entry_point/artifacts.snap	Shows removal of entry3.js shared chunk for duplicate entry points

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

Copilot

Pull request overview

Copilot reviewed 18 out of 18 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

crates/rolldown/src/stages/generate_stage/code_splitting.rs:959

The variable name ret is generic and doesn't convey its purpose. Consider renaming it to something more descriptive like all_dynamic_entries_reachable to clarify what the boolean represents.

    let ret = dynamic_entry.iter().all(|idx| {
      entry_chunk_reference
        .get(&chunk_idx)
        .map(|reached_dynamic_chunk| reached_dynamic_chunk.contains(idx))
        .unwrap_or(false)
    });
    ret.then_some(chunk_idx)

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

hyf0

I go through all snapshot changes and they're looking fine, but still want some input from @sapphi-red .

graphite-app · 2025-12-01T01:58:48Z

Merge activity

Dec 1, 1:58 AM UTC: IWANABETHATGUY added this pull request to the Graphite merge queue.
Dec 1, 1:59 AM UTC: sapphi-red removed this pull request from the Graphite merge queue.
Dec 1, 3:15 AM UTC: IWANABETHATGUY added this pull request to the Graphite merge queue.
Dec 1, 3:15 AM UTC: Merged by the Graphite merge queue.

related to #4904

sapphi-red · 2025-12-01T02:00:21Z

Let me check the behavior, in case.

.../rolldown/tests/rolldown/semantic/export_star_from_external_as_shared_entries/artifacts.snap

...ldown/tests/rolldown/semantic/export_star_from_external_as_shared_entries_cjs/artifacts.snap

related to #4904

Copilot

Pull request overview

Copilot reviewed 18 out of 18 changed files in this pull request and generated no new comments.

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@sapphi-red

## [1.0.0-beta.53] - 2025-12-03 💥 Breaking Changes - Drop `i686-pc-windows-msvc` target support 🚀 Chunk Merging Optimization - Rolldown now automatically merges shared chunks when entries import each other (when `preserveEntrySignature` is not `strict`) ```shell Before: entry.js → imports → shared.js (common chunk) entry2.js → imports → shared.js Output: 3 chunks (entry.js, entry2.js, shared.js) After: entry.js → contains shared code entry2.js → imports → entry.js Output: 2 chunks (entry.js, entry2.js) ``` ### 💥 BREAKING CHANGES - drop `i686-pc-windows-msvc` target support (#7230) by @sapphi-red ### 🚀 Features - rolldown_plugin_vite_manifest: pass normalized options to `isLegacy` callback (#7321) by @shulaoda - plugin/vite-resolve: add `disableCache` option (#6763) by @sapphi-red - rolldown: export `createTokioRuntime` for tsdown (#7264) by @shulaoda - rolldown_plugin_vite_html: sync `moduleSideEffects` for already loaded modules (#7254) by @shulaoda - rolldown_plugin_vite_html: load module scripts with side effects to prevent tree-shaking (#7244) by @shulaoda - rolldown_plugin_vite_css_post: implement `cssScopeTo` for scoped CSS tree-shaking (#7240) by @shulaoda ### 🐛 Bug Fixes - export default class decl __name runtime insertion (#7316) by @IWANABETHATGUY - chunk side effects calculation (#7273) by @IWANABETHATGUY - node: `output.generateCode.preset: 'es2015'` should set `output.generateCode.symbols: true` by default (#7314) by @sapphi-red - skip name helper for classes with static name property (#7312) by @IWANABETHATGUY - preserve chunk imports relationship after chunk merging (#7303) by @shulaoda - dev: make `register_modules` async (#7289) by @hyf0 - preserve computed property in object destructuring (#7288) by @IWANABETHATGUY - support dynamic imports with shared dependencies (#7261) by @IWANABETHATGUY - call `defer_sync_scan_data` in non-incremental build mode (#7255) by @shulaoda - optimize chunk merging for shared entry points (#7194) by @IWANABETHATGUY - add indentation for UMD format output (#7263) by @IWANABETHATGUY - rolldown_plugin_vite_css_post: pass options to `isLegacy` callback for proper legacy detection (#7260) by @shulaoda - rolldown_plugin_vite_css_post: also detect `?inline=true` query for inlined CSS (#7245) by @shulaoda - rolldown_plugin_vite_css_post: distinguish empty CSS from no CSS (#7241) by @shulaoda - add Windows support for t-run command (#7242) by @IWANABETHATGUY - cjs: prevent duplicate require declarations for external modules with preserveModules (#7234) by @logaretm - rolldown_plugin_vite_resolve: resolve from root for virtual modules (#7236) by @sapphi-red - include entry level external modules in chunk exports (#7218) by @IWANABETHATGUY ### 🚜 Refactor - dev: make `removeClient` async (#7313) by @hyf0 - move chunk merging code out of code_splitting.rs (#7285) by @IWANABETHATGUY - extract common function util for chunk merging (#7271) by @IWANABETHATGUY - use iterative method to merge chunks (#7256) by @IWANABETHATGUY - use concat_string! instead of string replace for generating chunk level exports (#7247) by @IWANABETHATGUY ### 📚 Documentation - add warning to experimental.resolveNewUrlToAsset about JS/TS files (#7300) by @Copilot - add sequential hook execution difference in plugin-api.md (#7308) by @Copilot - add migration example from onwarn to onLog (#7299) by @Copilot - add migration example for manualChunks to advancedChunks (#7298) by @Copilot - deps: bump vitepress to fix build (#7307) by @sapphi-red - examples & text for experimental.resolveNewUrlToAsset (#7259) by @TheAlexLichter ### ⚡ Performance - rolldown_plugin_vite_css_post: lazily load `cssScopeTo` from JS module options (#7253) by @shulaoda - rolldown_plugin_vite_css_post: avoid unnecessary string clones in `resolve_asset_urls_in_css` (#7250) by @shulaoda ### 🧪 Testing - generate relative path like name in advanced chunks (#7267) by @IWANABETHATGUY - add test case for preserveEntrySignatures with re-exports (#7279) by @IWANABETHATGUY - add test262 integration tests (#7196) by @sapphi-red ### ⚙️ Miscellaneous Tasks - deps: update dependency rolldown-plugin-dts to v0.18.1 (#7304) by @renovate[bot] - enable tracing feature for napi (#7322) by @sapphi-red - deps: update napi (#7320) by @renovate[bot] - deps: update oxc (#7318) by @renovate[bot] - deps: update napi (#7317) by @renovate[bot] - deps: update oxc to v0.100.0 (#7301) by @renovate[bot] - deps: downgrade pnpm to 10.23.0 to fix Netlify build (#7306) by @shulaoda - add `trustPolicyExclude` for chokidar and semver (#7302) by @sapphi-red - update pnpm lockfile (#7291) by @IWANABETHATGUY - deps: update npm packages (#7272) by @renovate[bot] - deps: update rust crates (#7270) by @renovate[bot] - deps: update oxc (#7262) by @renovate[bot] - deps: update github-actions (#7269) by @renovate[bot] - deps: update dependency dprint-typescript to v0.95.13 (#7268) by @renovate[bot] - deps: update `html5gum` to 0.8.1 (#7265) by @shulaoda - rolldown: remove unused `getModuleOptions` from `PluginContext` (#7266) by @shulaoda - remove unnecessary justfile ignore (#7243) by @IWANABETHATGUY - deps: update oxc apps (#7238) by @renovate[bot] - add `nul` to workaround https://github.com/anthropics/claude-c… (#7237) by @IWANABETHATGUY - deps: update dependency valibot to v1.2.0 [security] (#7231) by @renovate[bot] - deps: update crate-ci/typos action to v1.40.0 (#7232) by @renovate[bot] ### ❤️ New Contributors * @logaretm made their first contribution in [#7234](#7234) Co-authored-by: shulaoda <[email protected]>

silvenon · 2026-01-08T09:06:23Z

Pardon my lack of performance knowledge, but when looking at the "After" below doesn't this cause index.js to import all of lib.js just to get the one shared piece, whereas having the shared chunk would result in downloading only the much smaller shared script, the amount that's actually being used?

IWANABETHATGUY · 2026-01-08T09:21:00Z

Pardon my lack of performance knowledge, but when looking at the "After" below doesn't this cause index.js to import all of lib.js just to get the one shared piece, whereas having the shared chunk would result in downloading only the much smaller shared script, the amount that's actually being used?

That only happens when the lib.js is referenced with a single entry. https://repl.rolldown.rs/#eNqFUUtqwzAQvcowG7cQXHfr0DMUutZGtUfBwRkZaZwPwneP5E/ikEA2Qo/R+8xTQINlwIZrOufi052xvOMNVgkeOusEgh7AOHuALP9qm/987zPFdB5npudKGssg5OXjE4JiAEfSOwa9VTxEKcJSXE/DBp1t29qeOK8sm2a3cn4xecggl44gwN/87LdLph6WYAs9A8WKo4YXmJTKJ85PChmTpWPeoiaj+3ahYEw67bmkm9GUaOZMJjrKfRdFsX3Yk1jcZcW/4be9uudmR/JYbRyuy41wXW/0PaasOn0FDlfLrKVl

If it is shared with more than one entry, the optimization would bail out.

silvenon · 2026-01-08T10:22:08Z

Ah, I see now (had to fill in the configuration), that's pretty cool! Thank you for the clarification.

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IWANABETHATGUY force-pushed the 11-20-feat_4904 branch from b158b29 to ffca43f Compare November 22, 2025 10:15

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refactor: use iterative method to merge chunks #7256

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fix: support dynamic imports with shared dependencies #7261

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IWANABETHATGUY changed the title ~~feat: 4904~~ fix: optimize chunk merging for shared entry points Nov 30, 2025

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fix: optimize chunk merging for shared entry points (#7194)

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related to #4904

graphite-app bot force-pushed the 11-20-feat_4904 branch from 0059fc0 to c9cf6b7 Compare December 1, 2025 01:59

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fix: chunk side effects calculation #7273

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test: add test case for preserveEntrySignatures with re-exports #7279

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fix: optimize chunk merging for shared entry points (#7194)

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related to #4904

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[Feature Request]: improve output of export_star_from_external_as_shared_entries #7281

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fix: include dependency files in Netlify ignore check and disable frozen lockfile #7290

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[Bug]: imports field does not include the values it should when the chunks are merged #7297

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release: v1.0.0-beta.53 #7319

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release: v1.0.0-beta.53 #7324

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[Bug]: unnecessary import statement was added #5698

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