LLVM has a pretty decent walk-through/tutorial for building an LLVM language frontend. I know it's in the article but this is definitely my go to for helping people learn about using LLVM.
https://llvm.org/docs/tutorial/MyFirstLanguageFrontend/index...
Not by any means a tutorial but Rust has a guide for understanding their LLVM compiler frontend. It has some useful insights into what actually makes up a real "production grade" compiler outside the stuff in the LLVM tutorial.