perf(minify): skip renaming symbols with zero use count

[robobun]

Summary

• Filter out zero-count slots before sorting in MinifyRenamer, avoiding unnecessary sorting and iteration

These slots represent declared symbols in nested scopes that were tree-shaken away. By filtering them out before sorting, we avoid unnecessary name generation work.

Ported from oxc: oxc-project/oxc#18183

Test plan

• Added minify/SkipUnusedSymbolSlots test that verifies the optimization works when nested scopes are tree-shaken
• Existing bundler minify tests pass

🤖 Generated with Claude Code

[robobun]

^{Updated 11:23 PM PT - Jan 18th, 2026}

❌ Your commit ab9ba5be has 2 failures in Build #35276 (All Failures):

• cmake/targets/BuildBun.cmake - cmake error on 🐧 x64-asan - build-cpp
• test/integration/next-pages/test/dev-server.test.ts - 1 failing on 🍎 13 aarch64

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[coderabbitai]

Walkthrough

Frequency-based renaming in src/renamer.zig now builds candidates by iterating slots and skipping symbols with zero use count; a regression test was added to ensure unused symbol slots are not assigned short minified names.

Changes

Cohort / File(s)	Summary
Renaming Logic Updates src/renamer.zig	MinifyRenamer.assignNamesByFrequency: build the candidate list by iterating each namespace slot and appending only slots with non-zero use counts, then sort by count; removed prior pre-population of zero-count entries.
Tests test/bundler/bundler_minify.test.ts	Added regression test minify/SkipUnusedSymbolSlots to verify the minifier skips pre-allocated zero-use symbol slots and assigns short names only to used symbols.

Suggested reviewers

• pfgithub

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main performance optimization: skipping renaming of symbols with zero use count, which directly aligns with the core change in MinifyRenamer.assignNamesByFrequency.
Description check	✅ Passed	The description covers both required sections: explains what the PR does (filtering zero-count slots) and provides a test plan (added regression test and existing tests pass). It includes helpful context about the purpose and oxc source.

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[Jarred-Sumner]

Could not find a measurable performance difference.