Isolating Compiler Bugs through Compilation Steps Analysis

Compilers are essential to software systems, and their bugs can propagate to dependent software. Ensuring compiler correctness is critical. However, isolating compiler bugs remains challenging due to the internal complexity of compiler execution. Existing techniques primarily mutate compilation inputs to generate passing and failing tests, but often lack causal analysis of internal steps, limiting their effectiveness. To address this limitation, we propose CompSCAN, a novel compiler bug isolation technique that applies analysis over the sequence of compilation steps. CompSCAN follows a three-stage process: (1) extracting the array of compilation steps that leads to the original failure, (2) identifying bug-causing steps and collecting corresponding compiler code elements, and (3) calculating suspicious scores for each code element and outputting a suspicious ranking list as the bug isolation result. We evaluate CompSCAN on 185 real-world LLVM and GCC bugs. Results show that CompSCAN outperforms state-of-the-art techniques in both effectiveness and efficiency. CompSCAN successfully isolates 50, 85, 100, and 123 bugs within the Top-1/3/5/10 ranks, respectively. Compared with ETEM and ODFL, two state-of-the-art compiler bug isolation techniques, CompSCAN achieves relative improvements of 44.51% / 50.18% / 36.24% / 24.49% over ETEM, and 31.58% / 49.12% / 44.93% / 21.78% over ODFL on those metrics. Moreover, CompSCAN runs faster on average per bug than both baselines.