[llvm] LangRef: Clarify that unnamed_addr constants can be duplicated. (PR #199251)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic commented:

The set of transforms we currently do is known not to be self-consistent.  Declaring one set legal, and the other illegal, is not usefully clarifying anything.

If you want to say something here, it's probably better to just describe the current status: duplication causes miscompiles, but LTO does it anyway.

https://github.com/llvm/llvm-project/pull/199251