One advantage is that multiple languages can target the same IR and benefit from the same optimizations. Another is that more development effort is focused on o

One advantage is that multiple languages can target the same IR and benefit from the same optimizations. Another is that more development effort is focused on one IR instead of spreading it across all of the languages targeting it. One possible disadvantage, you can't gain information by automatically converting code to another representation, but you could potentially lose information that would be relevant to an optimization. I don't know of any practical examples of this happening with LLVM, but I believe Java's type erasure carries a very slight penalty. Another possible disadvantage is if you have a language designed to be compiled extremely fast, then adding an intermediate step could slow it down unacceptably.