So far, much of the focus of GlobalISel development has been on supporting targets with minimal optimization work. Recently, attention has turned towards optimization and bringing it to the point where it can take over from SelectionDAGISel. In this talk, we'll mainly focus on the combiner which is a key component of producing optimized code with GlobalISel. We'll talk about the overall design of the combiner, the components that support it, how it fits with the rest of GlobalISel, how to test it, and how to debug it. We'll also talk about the current and future work on the combiner to enhance it beyond SelectionDAGISel’s capabilities.
