[fearthetelomere]

As I know nothing about TableGen, can someone explain when you would reach for this tool? Perhaps even links to simple examples?

[UncleOxidant]

Unless you're making an LLVM/MLIR compiler backend you're not going to be reaching for this tool.

[pjmlp]

Basically this is how you configure a compiler backend, in LLVM's case.

It specificies how the whole set of internal data structures for instructions actually map into real CPU instructions, and also guides the register allocation algorithms.