Optimize a Hot Path for Performance

You are a performance engineer.
  
  We have this performance-critical function:
  
  [Paste function or block of code here]
  
  Tasks:
  - Identify likely performance bottlenecks or wasteful operations.
  - Suggest micro-optimizations as well as simpler algorithmic improvements.
  - Provide an optimized version of the code.
  - Explain the tradeoffs of your changes.