[flang] [llvm] [flang][OpenMP] Decompose compound constructs, do recursive lowering (PR #90098)

[Krzysztof Parzyszek via llvm-commits]

kparzysz wrote:

> A few tests fail for me in my local build since this commit
> 
> ```
> Lower/OpenMP/parallel-sections.f90
> Lower/OpenMP/taskgroup.f90
> Lower/OpenMP/teams.f90
> ```
> 
> But I see the aarch64 buildbot is green: https://lab.llvm.org/buildbot/#/builders/173 so perhaps this is a problem on my end. Do you have any idea where I should look?
> 
> Or has anyone else come across the same problem?

I was just able to reproduce this now.  I don't know what's causing the assertion yet, but I know why it didn't fail `check-flang` for me earlier on.  The test is predicated on the presence of `omp_runtime` in the lit environment (because the test uses the `omp_lib` module).  That module wasn't built in my environment, and the test was silently skipped.  When I ran it by hand, flang-new complained about some other of its own modules not being valid.  I had to rebuild/reinstall the entire project from scratch to force these modules to be rebuilt with a recent flang-new.  FYI, the module errors I was seeing were
```
  use,intrinsic::iso_c_binding,only:c_new_line
                 ^^^^^^^^^^^^^
/work/kparzysz/c/org/bin/../include/flang/omp_lib_kinds.mod:52:16: error: Cannot read module file for module 'iso_c_binding': File is not the right module file for 'iso_c_binding': /work/kparzysz/c/org/bin/../include/flang/iso_c_binding.mod
```

https://github.com/llvm/llvm-project/pull/90098