Making collection operations optimal with aggressive JIT compilation

Functional collection combinators are a neat and widely accepted data processing abstraction. However, their generic nature results in high abstraction overheads -- Scala collections are known to be notoriously slow for typical tasks. We show that proper optimizations in a JIT compiler can widely eliminate overheads imposed by these abstractions. Using the open-source Graal JIT compiler, we achieve speedups of up to 20x on collection workloads compared to the standard HotSpot C2 compiler. Consequently, a sufficiently aggressive JIT compiler allows the language compiler, such as Scalac, to focus on other concerns.