One can have sanitizers also for defined behavior. The issue is that a sanitizer that has no false positives is about 100x more useful than a sanitizer that has false positives. You can treat each case where a sanitizer detects signed overflow as an error, even in production. You can not do this same when the behavior is defined and not an error. (you can make it an error and still define it, but there is not much of a practical difference)
If you think signed overflow is a mistake, you could forbid it from your code base, even if it weren't UB, and then any instance of it that a sanitizer finds would not be a true positive, because your code style forbids signed integer overflow.
You can do even better than this. You can _make_ it undefined behavior with __builtin_unreachable().
No idea if the optimization potential is the same but at least then you can feel like your sanitizer is necessary in all cases (to help you find and add these calls).
