perf(mangler): replace FixedBitSet with BitSet based on Rolldown's implementation

[sapphi-red]

Just recalled that there's a bitset implementation in rolldown that is not complicated. I've copied that and change it to use the allocator. This might work?

refs #11347

[sapphi-red]

• perf(mangler): replace FixedBitSet with BitSet based on Rolldown's implementation #13419 👈 (View in Graphite)
• main

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[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #13419 will degrade performances by 17.18%

_{Comparing 08-30-perf_mangler_replace_fixedbitset_with_bitset_based_on_rolldown_s_implementation (e473b83) with main (f97283b)¹}

Summary

⚡ 1 improvements
❌ 2 regressions
✅ 34 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	mangler[RadixUIAdoptionSection.jsx]	14.7 µs	11.9 µs	+24.02%
❌	mangler[binder.ts]	828.6 µs	894.9 µs	-7.41%
❌	mangler[cal.com.tsx]	3.4 ms	4.1 ms	-17.18%

Footnotes

1. No successful run was found on main (e473b83) during the generation of this report, so f97283b was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[Copilot]

Pull Request Overview

This PR replaces the external FixedBitSet dependency with a custom BitSet implementation based on Rolldown's implementation to improve performance in the mangler. The custom implementation uses the allocator for memory management.

• Removes the fixedbitset dependency and implements a custom BitSet struct
• Updates mangler code to use the new BitSet API methods (has_bit, set_bit)
• Integrates the new BitSet with the existing allocator system for better memory management

Reviewed Changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

File	Description
crates/oxc_mangler/src/lib.rs	Updates imports and replaces FixedBitSet usage with custom BitSet
crates/oxc_mangler/src/bitset.rs	Adds new custom BitSet implementation with allocator support
crates/oxc_mangler/Cargo.toml	Removes fixedbitset dependency
Cargo.toml	Removes fixedbitset from workspace dependencies

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[Boshen]

Merge activity

• Aug 30, 11:15 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Aug 30, 11:15 AM UTC: Boshen added this pull request to the Graphite merge queue.
• Aug 30, 11:27 AM UTC: Merged by the Graphite merge queue.