perf(syn): use switch for hot bits4 usedBits checks

[wolf31o2]

Summary by cubic

Optimized the syn decoder’s bits4() hot path by replacing consecutive if checks with a switch on usedBits to reduce branching and improve performance. No functional changes.

^{Written for commit acfbc6e. Summary will update on new commits.}

Summary by CodeRabbit

• Refactor
  • Improved internal decoding logic efficiency through optimized control flow handling.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: b0a6d933-c9cc-47c5-a554-9047093cd97d

📥 Commits

Reviewing files that changed from the base of the PR and between 8d3415e and acfbc6e.

📒 Files selected for processing (1)

• syn/flat_decode.go

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📝 Walkthrough

Walkthrough

The pull request refactors the control flow in the (*decoder).bits4() method within syn/flat_decode.go. Two sequential if statements checking d.usedBits == 0 and d.usedBits == 4 are replaced with a switch statement using case 0 and case 4. Both approaches set d.usedBits and advance d.pos identically before falling through to existing general cross-byte decoding logic for other usedBits values. The functional behavior remains unchanged.

Possibly related PRs

• perf(syn): low-nibble bits4 fast path #282: Modifies the same decoder.bits4() function, specifically addressing the d.usedBits == 4 case handling with an explicit low-nibble fast path approach.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: refactoring control flow in bits4() to use a switch statement instead of sequential if checks for better performance with hot code paths.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch perf/switch-case

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[cubic-dev-ai]

No issues found across 1 file