> All of which is to say, I don't see how "what constitutes exposing a pointer" would be a hard question.

It's a hard question because any coherent semantics you come up with breaks optimizations that are obviously correct™. This is difficult to convey in toy examples, because in toy examples, there's clearly enough information present that the optimizer could do the right thing™ if it were smart enough.

The other thing to keep in mind is that optimization generally works on semi-mangled forms of the source code, so if you have a pointer-to-integer that has no use at the IR level, that doesn't necessarily mean that the pointer-to-integer had no use at the source code level (and same for the converse, incidentally--the IR might materialize uses that didn't exist at the source code level).