[libcxx-commits] [libcxx] Commit mostly working single wrapped module map (PR #87402)

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EricWF wrote:

> I think we need to have an overview of your build environment, is this for Google? Should we try to meed some time with @dwblaikie too and figure out how to best support what you need to do?

This is not at Google, it's me at home trying to save cycles on my LLVM compiles.

The good news is that I haven't been able to reproduce my normal breakages when trying today to create a reproducer :-)

There's been a bunch of work on modules since I last tried this, and I suspect some of it resolved the issues I was seeing.

The less fortunate news is that it appears the current approach, without the top level `std` module, is something like 25% slower to build llvm-tblgen (for example) and produces a module cache about 1.8x the size (205M vs 123M).  than the approach with the top level `std` module.

I'll do some more digging and report back.





https://github.com/llvm/llvm-project/pull/87402