Getting Started with LLVM Core Libraries

Optimizing at the IR level

Once translated to the LLVM IR, a program is subject to a variety of target-independent code optimizations. The optimizations can work, for example, on one function at a time or on one module at a time. The latter is used when the optimizations are interprocedural. To intensify the impact of the interprocedural optimizations, the user can use the llvm-link tool to link several LLVM modules together into a single one. This enables optimizations to work on a larger scope; these are sometimes called link-time optimizations because they are only possible in a compiler that optimizes beyond the translation-unit boundary. An LLVM user has access to all of these optimizations and can individually invoke them using the opt