Alias analysis is widely used in many LLVM transformations. In this tutorial, we will give an overview of pointers, Alias and ModRef analyses. We will first present the concepts around pointers and memory models, including the representation of the different types of pointers in LLVM IR, then discuss the semantics of ptrtoint, inttoptr and getelementptr and how they, along with pointer comparison, are used to determine memory overlaps. We will then show how to efficiently and correctly use LLVM’s alias analysis infrastructure, introduce the new API changes, as well as the highlight common pitfalls in the usage of these APIs.
