In this chapter, we looked into the modular design of LLVM: How it is used in the opt tool of LLVM, and how it is applicable across LLVM core libraries. Then we took a look into LLVM intermediate representation, and how various entities (variables, functions etc.) of a language are mapped to LLVM IR. In the last section, we discussed about some of the important LLVM tools, and how they can be used to transform the LLVM IR from one form to another.

In the next chapter, we will see how we can write a frontend for a language that can output LLVM IR using the LLVM machinery.