Rust for C-Programmers

21.19 Performance Considerations

Rust’s match expressions and pattern matching are designed for efficiency. The compiler translates patterns into optimized low-level code:

• Jump Tables: For matching enums without associated data, or integers within a dense range, the compiler often generates a jump table (similar to optimized C switch statements), providing O(1) dispatch time.
• Decision Trees: For more complex patterns involving different types, data destructuring, ranges, or guards, the compiler constructs efficient decision trees using sequences of comparisons and branches.

The overhead of the pattern matching itself is typically minimal compared to the code executed within the match arms. While micro-optimizations are possible, match is generally considered a highly efficient control flow mechanism in Rust. Profiling tools should be used if performance in a specific match expression is critical.