llvm dev - Aug 2021 - building LLVM 11 with OpenMP on Windows

I'm not sure this is the right place to post... If not, feel free to
redirect me.

I am trying to build LLVM 11, including Clang and OpenMP, on a Windows
machine with Visual Studio 2019 installed.

Clearly the openmp project is not adapted to a multiple configuration build
system like Visual Studio. It assumes that library files are in a lib
directory rather than in lib/Release, lib/Debug, etc. I have tried to build
with LIBOMP_COPY_EXPORTS disabled, which helps, but I still get link errors.

So I have tried to build with nmake instead, which is a single
configuration system like make. Strangely, this works for a release build,
but not for a debug build. When I try to build in debug, I get error
messages about unacceptable uses of std::atomic<unsigned int>.

Perhaps a solution would be to compile LLVM/Clang and OpenMP with Visual
Studio but separately? Only I don't know how to do that...

Has anybody out there managed to solve this problem one way or another?

Geoff
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Am Di., 3. Aug. 2021 um 05:05 Uhr schrieb Geoff Levner via llvm-dev
<llvm-dev at lists.llvm.org>:
> Perhaps a solution would be to compile LLVM/Clang and OpenMP with Visual
Studio but separately? Only I don't know how to do that...
You could use ninja on Windows (-cmake GNinja) which only has a single
configuration per builddir. If compilation with cl.exe fail, try
LLVM_ENABLE_RUMTIMES=openmp (instead of LLVM_ENABLE_PROJECTS=openmp)
which will build libomp using just-built clang.

Michael