I am not sure why you mention LLM, the post mentions LLVM. Second, you can have different optimization options with different tradeoffs in compile-time and run-time. Third, even if the default and only options distributed with clang are too compile-time intensive, the good news is that this is open source and you could argue against it, or fork and maintain your own compile-time run-time tradeoff compiler along with other people who also want that behaviour. I don't see any benefit of arguing against research. Having new techniques to improve compilers is not a zero sum game.