[llvm] [IR] Verify oracle functions are only used by llvm.speculative.load. (PR #226669)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

> I think this could fail if the oracle function is merged with another function, and thus additional uses are added.
>
> I think we may want to require these functions to have a special attribute.

In the initial version, I required them marked with an `oracle-function` string attribute and also use it in https://github.com/llvm/llvm-project/pull/188017 directly. Does that sound good?

https://github.com/llvm/llvm-project/pull/226669