From Verification to Optimizations

Compilers perform static analysis prior to applying an optimization. The analysis results are typically not very precise, however, as a compiler operates with a strict time budget, which constrains reasoning. In this paper, we explore a new direction: using information gathered by external sound static analysis tools to augment the internal compiler reasoning, and investigate whether this leads to better optimization. One of the key problems to be solved is that of propagating the source-level information gathered by a static analyzer deeper into the optimization pipeline. We propose an approach to achieve this and demonstrate its feasibility through an implementation using the LLVM compiler infrastructure. We show how assertions obtained from the Frama-C static analysis tool are propagated through LLVM and are then used to substantially improve the effectiveness of several optimizations.