In our previous blog post about improved OpenMP support in Visual Studio, we announced the addition of the -openmp:llvm switch in Visual Studio 2019 version 16.9 to enable compiled programs to target LLVM’s OpenMP runtime library for the x64 architecture. This switch supports all the OpenMP 2.0 directives that -openmp supports, as well as unsigned integer indices in parallel for loops, and a subset of the SIMD directives that are supported under -openmp:experimental. It also enabled a few correctness fixes. Starting in Visual Studio 2019 version 16.10 Preview 2, the **-openmp:llvm **switch now works for x86 and arm64. We have also fixed a couple of bugs in 16.10 Preview 3.

-openmp:llvm Now Available for x86 and arm64

Starting in Visual Studio 2019 version 16.10 Preview 2, in addition to X64 support, we have added support for targeting LLVM’s OpenMP runtime library with **-openmp:llvm **for the x86 and ARM64 architectures. Compiling with **-openmp:llvm **will automatically add a dynamic link to libomp140.i386.dll (or libomp140d.i386.dll under /DEBUG) when targeting x86, or libomp140.aarch64.dll (or libomp140d.aarch64.dll under /DEBUG) when targeting ARM64. You can find these libraries under the Visual Studio installation directory at VC\Redist\MSVC\<version>\debug_nonredist\<arch>\Microsoft.VC142.OpenMP.LLVM.

As a reminder, the -openmp:llvm switch is experimental, and features from OpenMP 3.0 that were added with the -openmp:llvm switch in Visual Studio version 16.9 are still only supported with the additional -openmp:experimental flag in Visual Studio version 16.10, and thus are provided with certain limitations in 16.10. In particular, **#pragma omp task **is not yet available on x86 or arm64, and there is only limited functionality on x64 in 16.10. Lastly, future versions of the LLVM OpenMP runtime DLLs may not be backwards compatible and the current version of these DLLs is not redistributable.

#c++ #visual studio 2019