[lld] [LLD][COFF] Add support for including native ARM64 objects in ARM64EC images (PR #137653)

[Martin Storsjö via llvm-commits]

https://github.com/mstorsjo commented:

This feels like a quite large change. That makes it feel hard to grasp - even if the final state perhaps isn't that much more complicated than the initial state.

However I'm not sure I understand the full context of this change. Is this input case something that we do expect that we'd ever want to do? (In my understanding of arm64ec/arm64x use cases, I don't see when we'd ever want to do this?) Doesn't this just cause a quite confusing situation where you can link in object files which do end up in the final image, but which are pretty much inactive (not referenced, not used at runtime at all)? As I don't see the real use case, I also feel a bit more hesitant about a change like this which is yet another small step towards a more complex internal linker state.

I'm also a little curious about how you managed to do this change, to check all changes (e.g. regarding delay imports), as we don't really exercise this new case in any of the existing tests? But I guess the fact that you always create two symbol tables even if we essentially never use one of them, causes us to force testing all codepaths in the existing tests anyway...

https://github.com/llvm/llvm-project/pull/137653