Found this: https://old.reddit.com/r/rust/comments/1l6odxa/which_rust_versions_correspond_to_specific_llvm/mwqfzbr/

Basically you can go through the llvm-project commits and find the version you need using that.

When opening the commit view on GitHub you can also see which tags the commit is a part of - which correspond to the different rust versions. So with that you should be able to find the versions you want.

I guess it could also be possible to automate this and produce an auto-generated table. It would potentially be something interesting to include in the rust docs :)