> The takeaway here is that the Clang AST is missing information that is invented by the LLVM IR code generator, but LLVM IR is also missing information that is destroyed by said code generator. And if you want to bridge that gap, you need to rely on an approximation: the Clang CFG.

This is how optimizers do terrible things with no way to warn users: information loss across multiple transformed representations of the original. It's a telephone game.