It's certainly not trivial, but still an interesting journey. I made a backend for MMIX, heavily influenced by the risc-v implementation, and kept the patches logically consistent by rebasing new changes to serve as an example. The last rebase was a year ago, but I think following a previous implementation is the best way forward as there is so much boiler-plate:
- https://github.com/stuij/mmix-llvm-support
- https://github.com/stuij/mmix-llvm-backend
That said, those kind of olden CPU's aren't a terribly snug fit for LLVM, due to their peculiarities. You'll have to bend LLVM quite a bit to bend it to your will, which also means that you need to get quite familiar with it as well.
That said, those kind of olden CPU's aren't a terribly snug fit for LLVM, due to their peculiarities. You'll have to bend LLVM quite a bit to bend it to your will, which also means that you need to get quite familiar with it as well.
edit: this tutorial is even older still, but for me it was one of the best resources, next to checking other simple backends: https://jonathan2251.github.io/lbd/llvmstructure.html