[clang-tools-extra] [clangd] [C++20] [Modules] Introduce initial support for C++20 Modules (PR #66462)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

> thanks a lot, LGTM!
> 
> i think the only big item remaining is injecting resource-dir correctly when running clang-scan-deps.
> 
> the most important follow up (for functionality, rather than optimizations and usability) is indexing the PCMs as we build them (similar to preamble-indexing we run today). For any future travelers, please do start a discussion in advance for that one.

Thanks for reviewing!

For future plans, I still like to chase for optimizations and usability first. For example, we need to reuse built module files across opened files. Otherwise every time we open a new file, we need to build all the modules dependent. This can't be tolerant in real workloads. For example, some modules and their dependent modules need 10+ seconds to build. Then it is a nightmare.

For index the PCMs, what's your suggestion and the path to do that? I don't have an idea for that yet.

https://github.com/llvm/llvm-project/pull/66462