Minotaur is a synthesis-based superoptimizer for the LLVM intermediate representation, that focuses on optimizing LLVM’s portable vector operations as well as intrinsics specific to the Intel AVX extensions. The goal is to automatically discover transformation rules that are missing from LLVM, which are challenging due to the large number of intrinsics, their semantic complexity, and their counterintuitive costs. Minotaur has found many new transformations for vectors instruction. We have evaluated Minotaur on various micro-benchmarks and real-world applications such as GNU MP library. The micro-benchmarks optimized by Minotaur show speedups up to 1.4x, and the real-world applications show speedups up to 1.06x.