@jer It doesn’t require deep knowledge of either usually to just get rustc building with a new LLVM, mostly just requires getting the Rust LLVM wrappers and src/rustllvm to build again. Once the new rustc builds you might run into test suite failures, and resolving those gets more difficult. If you wanted to get started you could just rebase the src/llvm submodule onto upstream llvm/master and start building it. @shepmaster’s fork should provide some solid hints about what needs to be fixed.