Even Clang would greatly benefit from an intermediate IR between the C/C++ AST and LLVM IR; the presentation you linked starts off by going over that (and I can

Even Clang would greatly benefit from an intermediate IR between the C/C++ AST and LLVM IR; the presentation you linked starts off by going over that (and I can confirm that it’s still a problem). That doesn’t mean that LLVM or its IR is bad, or that C or C++ are not suited to being compiled to it. It just means that some analyses and optimizations are best done at a higher level.