[afdbcreid]

> The compiler does not get to look at that and say "well this looks like undefined behavior, let me get rid of this line!".

No production compiler does that (directly). This is silly. We want to help programmers. They sometimes keep it even if it is known to be UB just because removing it is unlikely to help optimizations.

But if you are optimizing assuming something does not happen, then you have undefined behavior. And you are always assuming something does not happen when optimizing.