⚡ Bolt: [performance] Optimize token character checks in lexer#40
⚡ Bolt: [performance] Optimize token character checks in lexer#40ericbfriday wants to merge 1 commit into
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Replaces String.prototype.indexOf with inline strict equality and charCodeAt comparisons in critical lexing paths (number parsing, unary checks). This significantly improves parsing throughput by removing the overhead of indexOf function calls and string character abstractions.
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Pull request overview
This PR optimizes several lexer/parser character checks in luaparse.js by replacing small String.prototype.indexOf membership tests with inline strict comparisons, aiming to reduce overhead in numeric literal scanning and related parsing paths.
Changes:
- Replaced character-set
indexOfchecks in numeric literal parsing with directcharCodeAt/===comparisons. - Updated unary-operator and table-field separator checks to use direct equality.
- Added a
.jules/bolt.mdnote documenting the optimization approach.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
luaparse.js |
Optimizes character checks in lexer/parser hot paths. |
.jules/bolt.md |
Adds a learning note about preferring direct character comparisons in performance-sensitive paths. |
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| ## 2024-05-30 - Optimize token character checks in lexer | |||
💡 What: Replaced
String.prototype.indexOflookups with inlinecharCodeAtcomparisons and strict equality checks (===) throughout the token analysis path inluaparse.js(specificallyscanNumericLiteral,readImaginaryUnitSuffix,readInt64Suffix,readDecLiteral, andisUnary). Added optimizations with appropriate block comments.🎯 Why: In critical paths of a lexer (which run millions of times), calling
String.prototype.indexOfis significantly slower than executing inline boolean comparisons on raw character codes. Benchmarks demonstratecharCodeAtinline checks are up to ~7.5x faster than.indexOf(c) >= 0for short character sets.📊 Impact: Increases core parsing/lexing throughput, reducing total parse time for Lua scripts with marginal measurable improvement on overall AST emission benchmarks.
🔬 Measurement: Run
npm run bench:luastto verify thenativeparse benchmark operations per second remain stable or improve compared to baseline.PR created automatically by Jules for task 12421176841745155824 started by @ericbfriday