[llvm] [CAS] Add LLVMCAS library with InMemoryCAS implementation (PR #114096)

[Nikita Popov via llvm-commits]

nikic wrote:

Checking getMaxConcurrency() would work, but really I don't think using ThreadPool is appropriate for what you are doing here. These are not "tasks" where it's okay to schedule the later ones only after the earlier ones have finished. You should probably be using std::thread directly.

https://github.com/llvm/llvm-project/pull/114096