[Openmp-commits] [openmp] [openmp] Allow testing OpenMP without a full clang build tree (PR #182470)

[Martin Storsjö via Openmp-commits]

mstorsjo wrote:

> Could you also add logic that disables testing again when `OPENMP_TEST_C_COMPILER` is not set despite no clang target available?

As we implicitly set `OPENMP_TEST_C_COMPILER` from `CMAKE_C_COMPILER`, so the only case that would hit is if the user manually sets `OPENMP_TEST_C_COMPILER` to an empty string. So we shouldn't need that, as configuring the project does require a working `CMAKE_C_COMPILER` to begin with.

> If not too much work, could you make `OPENMP_TEST_Fortran_COMPILER` be handled the same way?

Sure, I tried to make that mostly consistent. There's some extra logic for printing/disabling that if that's unavailable, that I left untouched for now.

Now whether a build with `LLVM_ENABLE_PROJECTS="clang;flang" LLVM_ENABLE_RUNTIMES=openmp` will build flang before attempting to configure openmp or not, I'm not sure; currently it builds clang before configuring openmp at least. (That might require changes to `llvm-project/llvm/runtimes` if we'd want to add such an implicit dependency there. But I feel that's out of scope for this PR in any case.)

https://github.com/llvm/llvm-project/pull/182470