Quantifying Compiler-induced Reliability Loss in Software-Implemented Hardware Fault Tolerance

Compiler mechanisms for Software-Implemented Hardware Fault Tolerance (SIHFT) offer a cost-effective solution for reliability, paving the way towards the adoption of Commercial Off-The-Shelf (COTS) components in safety-critical environments. However, default compiler optimizations can remove the SIHFT-induced redundancy and checks. For this reason, the use of compiler optimizations was discouraged in the literature. This article presents a comprehensive study of the reliability degradation introduced by LLVM's O2 optimization pipeline when using a state-of-the-art SIHFT tool. We quantify, via RTL fault injection, the impact of O2 at different optimization stages, which identified a data corruption rate increase by up to 48x. We also propose a static exploration methodology to identify the LLVM passes that harm the reliability. Then, we remove these harmful passes from the optimization pipeline, demonstrating how to tune optimization pipelines to make SIHFT successful even in presence of compiler optimizations.