Leveraging Compilation Statistics for Compiler Phase Ordering

Choosing the optimal order and combination of compiler optimization passes - known as phase ordering - can enhance the performance of compiled binaries. However, existing approaches struggle to capture the subtle interaction between compiler passes and waste time on low-profitable pass sequences. We introduce CITROEN, a better approach for compiler phase ordering. CITROEN leverages pass-related compilation statistics to reject low-profitable compiler pass sequences to reduce the overhead of phase ordering search. It employs Bayesian optimization to navigate the search space, using compilation statistics instead of traditional tuning parameters to build an online cost model that provides both the performance prediction and the prediction uncertainty of compilation configurations. It dynamically allocates search iterations across source files to optimize search time in multi-file programs. We evaluate CITROEN by integrating it with the LLVM compiler and applying it to benchmarks from cBench and SPEC CPU 2017. CITROEN outperforms existing autotuning methods, discovering high-performing configurations quicker with fewer search iterations.