I am guessing there would be a LOT of false negatives of compilers removing dead code for good reason. For example, if you only use a portion of a library's enum then it seems reasonable to me that the compilers optimizes away all the if-else that uses those enums that will never manifest.
I don't think it is unreasonable to have an option for "warn me about places that might be UB" that would tell you if it removes something it thinks is dead because it assumed UB doesn't happen?
