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[Babel 7] Improve generator performance#17642

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nicolo-ribaudo merged 4 commits intobabel:7.xbabel/babel:7.xfrom
liuxingbaoyu:perf-generatorliuxingbaoyu/babel:perf-generatorCopy head branch name to clipboard
Jan 16, 2026
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[Babel 7] Improve generator performance#17642
nicolo-ribaudo merged 4 commits intobabel:7.xbabel/babel:7.xfrom
liuxingbaoyu:perf-generatorliuxingbaoyu/babel:perf-generatorCopy head branch name to clipboard

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@liuxingbaoyu liuxingbaoyu commented Dec 6, 2025 •
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Q                       A
Fixed Issues? Fixes #1, Fixes #2
Patch: Bug Fix?
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass? Yes
Documentation PR Link
Any Dependency Changes?
License MIT

Close #17627

This resulted in a 20%+ performance improvement vs v7.26.3 and a ~25% performance improvement vs the latest v7 version.

I did the following to improve performance:

  1. Store generator functions in a Map instead of class prototypes.
  2. Remove the queue.
  3. Reduce calls of charCodeAt.
  4. Reduce node.type comparisons.
  5. Make the identifier extraction logic run only when the source map is enabled.

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babel-bot commented Dec 6, 2025 •
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Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/60557

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pkg-pr-new Bot commented Dec 6, 2025 •
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commit: 369cfac

@liuxingbaoyu liuxingbaoyu marked this pull request as draft December 12, 2025 12:07
@liuxingbaoyu liuxingbaoyu marked this pull request as ready for review December 15, 2025 19:21
JLHwung
JLHwung reviewed Dec 15, 2025
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Comment thread babel.config.js
*/
function pluginGeneratorOptimization({ types: t }) {
const generatorNames = [];
fs.globSync(
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The globSync is not available in Node.js 6. The Babel config will be invoked by Jest to transform unit tests written in ESM.

@liuxingbaoyu liuxingbaoyu force-pushed the perf-generator branch 2 times, most recently from 22e537f to 666738c Compare December 16, 2025 00:09
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liuxingbaoyu commented Dec 16, 2025

Benchmark results compared to v7.26.3.

PS F:\babel\benchmark\babel-generator> node --expose-gc .\real-case.mjs
babel-generator/real-case.mjs babel-parser-express.ts @ current: 840 ops/sec ±0.6% 4128 runs (1.211ms)
babel-generator/real-case.mjs babel-parser-express.ts @ baseline: 497 ops/sec ±2.37% 2406 runs (2.079ms)
babel-generator/real-case.mjs jquery-3.6.js @ current: 263 ops/sec ±1.19% 1296 runs (3.861ms)
babel-generator/real-case.mjs jquery-3.6.js @ baseline: 163 ops/sec ±1.83% 798 runs (6.267ms)
babel-generator/real-case.mjs ts-checker.mjs @ current: 28.24 ops/sec ±1.42% 141 runs (36ms)
babel-generator/real-case.mjs ts-checker.mjs @ baseline: 20.69 ops/sec ±2.32% 103 runs (49ms)
babel-generator/real-case.mjs ts-checker.ts @ current: 21.99 ops/sec ±1.56% 110 runs (46ms)
babel-generator/real-case.mjs ts-checker.ts @ baseline: 16.3 ops/sec ±2.14% 81 runs (62ms)
babel-generator/real-case.mjs ts-parser.mjs @ current: 260 ops/sec ±1.03% 1286 runs (3.89ms)
babel-generator/real-case.mjs ts-parser.mjs @ baseline: 163 ops/sec ±1.73% 801 runs (6.244ms)
babel-generator/real-case.mjs ts-parser.ts @ current: 190 ops/sec ±1.36% 934 runs (5.358ms)
babel-generator/real-case.mjs ts-parser.ts @ baseline: 119 ops/sec ±1.96% 584 runs (8.572ms)
babel-generator/real-case.mjs typescript-5.6.2.js @ current: 5.72 ops/sec ±1.44% 64 runs (175ms)
babel-generator/real-case.mjs typescript-5.6.2.js @ baseline: 4.32 ops/sec ±1.65% 64 runs (232ms)

@liuxingbaoyu liuxingbaoyu mentioned this pull request Dec 18, 2025
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@liuxingbaoyu liuxingbaoyu added PR: Performance 🏃‍♀️ A type of pull request used for our changelog categories pkg: generator labels Jan 2, 2026
nicolo-ribaudo
nicolo-ribaudo approved these changes Jan 9, 2026
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Very nice!

Comment thread packages/babel-runtime-corejs3/helpers/esm/regeneratorDefineIM.js
@@ -1,10 +0,0 @@
import regeneratorDefine from "./regeneratorDefine.js";
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Q: Why is this deleted?

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@liuxingbaoyu liuxingbaoyu Jan 9, 2026

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This is in Babel 7, and we didn't remove it before.

JLHwung
JLHwung approved these changes Jan 10, 2026
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Has this PR been landed to Babel 8? If not could you prepare a new PR for Babel 8?

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liuxingbaoyu commented Jan 10, 2026

Has this PR been landed to Babel 8? If not could you prepare a new PR for Babel 8?

Not yet, but I will.

@nicolo-ribaudo nicolo-ribaudo merged commit 68e1577 into babel:7.x Jan 16, 2026
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