Java (JIT) vs C++ (AOT) for a simple hash table

The goal of this research is to explore the performance differences between JIT (just-in-time compilation) and AOT (ahead-of-time compilation) strategies and to understand their respective advantages and disadvantages. The intent is not to claim that one language is slower or worse than the other. In our tests, we observed better results with the HotSpot JVM 23 using JIT compilation. We got slower results with C++ (compiled with Clang 18), GraalVM 23 (compiled with native-image), and HotSpot JVM 23 with the -Xcomp flag. We are seeking to understand why this happens, and if possible, identify ways to improve the performance of the C++ version to match the results of Java's JIT compilation. Our benchmark involves comparing a hash table (map) implementation in Java to an equivalent implementation in C++. We made every effort to ensure consistency between the two implementations, but it’s possible that some nuances were overlooked. The hash table implementation itself is simple, and we aimed to make the Java and C++ code as equivalent as possible, including how memory is managed. For instance, we ensured that the C++ hash table values are stored by reference, not by value, to avoid unnecessary copying. The benchmark creates a hash table with 5,000,000 buckets and inserts 10,000,000 objects, minimizing collisions. The linear search in each bucket is kept to a maximum of two iterations to avoid discrepancies in measurements due to varying collision behavior across different elements. The Bench class, which handles the measurements, should also be equivalent in both implementations. Given these details, does anyone have insights into why the C++ version of the benchmark was slower than the Java version? Could there be something we overlooked or an aspect of the C++ implementation that could be optimized further? Perhaps specific Clang optimization options we should explore? The link to the project is here => https://github.com/coralblocks/CoralBench?tab=readme-ov-file#hotspotvm--xcomp-and-jit-vs-c-llvm-clang-vs-graalvm https://github.com/coralblocks/CoralBench?tab=readme-ov-file...