My experience is that LLVM can generally optimize the IR produced from clang frontend a bit better than the IR produced by myself. The advantage is small, but s

My experience is that LLVM can generally optimize the IR produced from clang frontend a bit better than the IR produced by myself. The advantage is small, but still exists. I think the major reason is that TBAA optimization is only possible if you manually emit those metadata (clang does, but I didn't, due to time limitation and fear of aliasing-related bugs). But that LLVM is designed to work best on the pattern emitted by Clang is definitely another reason. In fact, even the official documentation recommends users to emit IR in a way that looks similar to what is emitted by Clang, so you have a better chance to keep the LLVM optimizer happy.