Why the insistence that this has to be perfect for it to be of any use? If the optimizer can prove it isn’t used and elides any code that might call it, great.

Why the insistence that this has to be perfect for it to be of any use? If the optimizer can prove it isn’t used and elides any code that might call it, great. If it can’t, I can rewrite my code to not use that function or call it in a way where the optimizer can make that guarantee. There are all sorts of useful things that technically depend on deciding the halting problem, but turn out to be pretty easily solvable for virtually all practical cases.