[llvm-branch-commits] [clang] [flang] [llvm] [openmp] [Flang] Move builtin .mod generation into runtimes (Reapply #137828) (PR #171515)

[Petr Hosek via llvm-branch-commits]

petrhosek wrote:

> > However, I notice that `libomp.a` is still in the `lib` directory. Will that be changed in another PR?
> 
> Unrelated to this PR which is only about the .mod files.
> 
> However, changes like this is why I cared to remove the old LLVM_ENABLE_PROJECTS and standalone build from openmp. #177953 would be used to determine the build/install locations of `libomp.a` file (and other runtimes libraries).

Most other runtimes don't use the same naming or directory layout as compiler-rt (or flang-rt). libc, libc++, libc++abi, and libunwind (I'm not familiar with other runtimes like openmp) use different, simpler logic for deriving target-specific directory names. That's mainly because these runtimes arrived later, whereas compiler-rt was grandfathered in.

In all past discussions among build system maintainers, the consensus was that we should not use the compiler-rt scheme for other runtimes, instead we should over time change compiler-rt to use the same logic as other runtimes. We could revisit that, but I think this needs a broader discussion, ideally in an RFC rather individual PR like this one (or #177953).

https://github.com/llvm/llvm-project/pull/171515