[clang] [Serialization] Storing DeclID separately (PR #95897)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

> Thanks for this patch, I will try it on our codebase to see the effects of it and report back to you. I am also trying to understand in which cases this would be a win and when not. IIUC, this is always a win when `ModuleFileIndex != 0` and a pessimization otherwise.

Yes, I think.

> 
> When is `ModuleFileIndex == 0`? Does this only happen for predefined decls (that we never deserialize) or also for the declarations owned by the currently written module?

Yes, this is what I thought.



https://github.com/llvm/llvm-project/pull/95897