Comment by jcranmer

Given some of the discussions I've been stuck in over the past couple of weeks, one of the things I especially want to see built out for LLVM is a comprehensive executable test suite that starts not from C but from LLVM IR. If you've ever tried working on your own backend, one of the things you notice is there's not a lot of documentation about all of the SelectionDAG stuff (or GlobalISel), and there is also a lot of semi-generic "support X operation on top of Y operation if X isn't supported." And the precise semantics of X or Y aren't clearly documented, so it's quite easy to build the wrong thing.