[gcc/gdb/LLVM outsider here]

If someone is interested in what's being done to improve LLVMs debuginfo, here's a talk by Djordje Todorovic from two years ago: https://www.youtube.com/watch?v=GpMLt1oecOk. It's about tracking dwarf locations for variables by keeping around information from the parent frame. According to that presentation, at least that work has been progressing.