Witness Test Program Generation through AST Node Combinations

Compiler bugs can be critical, but localizing them is challenging because of the limited debugging information and complexity of compiler internals. A common approach to address this challenge is to analyze the compiler’s execution behavior while it processes witness test programs. To accurately localize a bug in the compiler, the approach must generate effective witness programs by identifying and modifying the code sections in the seed program that are directly associated with the bug. However, existing methods often struggle to generate such programs due to the random selection of code parts for mutation. In this paper, we propose a novel automated technique to (1) identify abstract syntax tree nodes that are most likely to be related to the bug in the compiler, which can transform a failing program into a passing one, and (2) use this information to generate witness test programs that can effectively localize compiler bugs. To evaluate the effectiveness of our approach, we built a prototype and experimented with it using 40 real-world LLVM bugs. Our approach localized 40% and 100% of bugs within the Top-1 and Top-5 compiler files, respectively.