perf(linter/plugins): remove bounds checks on regex tokens#20478
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Pull request overview
This PR applies a micro-optimization in the hot token deserialization path by rewriting a regex-cache bounds comparison into a form that V8/Maglev can use to elide an array bounds check.
Changes:
- Swaps the regex cache guard from
regexObjects.length > regexIndextoregexIndex < regexObjects.lengthto enable Maglev bounds-check elimination. - Updates the surrounding comment to document the V8-specific rationale and constraint.
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Possibly the most absurd optimization I've ever encountered.
```diff
- if (regexObjects.length > regexIndex) {
+ if (regexIndex < regexObjects.length) {
regex = regexObjects[regexIndex];
}
```
There is no semantic difference whatsoever between `regexObjects.length > regexIndex` and `regexIndex < regexObjects.length`. But V8's 2nd-tier Maglev compiler treats them differently. In the`>` version, `regexObjects[regexIndex]` incurs a bounds check, whereas in the new `<` version, no bounds check.
This is a micro-optimization, but this function is extremely hot, so it may actually move the needle in code that includes a lot of regexes. The same optimization is also applied in #20480.
Claude found this oddity by reading V8's source code!
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March 21, 2026 12:50
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Possibly the most absurd optimization I've ever encountered.
There is no semantic difference whatsoever between
regexObjects.length > regexIndexandregexIndex < regexObjects.length. But V8's 2nd-tier Maglev compiler treats them differently. In the>version,regexObjects[regexIndex]incurs a bounds check, whereas in the new<version, no bounds check.This is a micro-optimization, but this function is extremely hot, so it may actually move the needle in code that includes a lot of regexes. The same optimization is also applied in #20480.
Claude found this oddity by reading V8's source code!