[Openmp-commits] [openmp] [OpenMP] [cmake] Don't use -fno-semantic-interposition on Windows (PR #81113)

[Martin Storsjö via Openmp-commits]

mstorsjo wrote:

> You could likely remove this entire thing until we figure out a better way to handle this. It seems our options handling is kind of a mess right now and doesn't do a good job separating runtime builds from the LLVM project itself. But this is fine.

Thanks! Yes, openmp doesn't work quite smoothly in all these build settings. Contrary to other runtimes such as libcxx, there's actually 4 different ways one can build openmp; building the main llvm directory, including openmp in `LLVM_ENABLE_PROJECTS` (which afaik is probably the most default and tested way), including openmp in `LLVM_ENABLE_RUNTIMES`. Then one can also build it standalone by pointing cmake at `llvm-project/runtimes` and including openmp in `LLVM_ENABLE_RUNTIMES`. And finally, one can build it by pointing cmake directly at `llvm-project/openmp` (which is mostly supported and tested, but some things break occasionally).

In the case of libcxx, it only supports the two ways where it is specified via `LLVM_ENABLE_RUNTIMES` (either via `llvm-project/llvm` or by directly pointing at `llvm-project/runtimes`).

Anyway, would you be fine with backporting this to 18.x, to reduce the amount of build time warnings there?

https://github.com/llvm/llvm-project/pull/81113