[PATCH] D21845: [Driver][OpenMP] Add specialized action builder for OpenMP offloading actions.

[Samuel Antao via cfe-commits]

sfantao added a comment.

Hi Michael,

In https://reviews.llvm.org/D21845#581988, @mkuron wrote:

> I think `OffloadAction::DeviceDependences::add(..., ..., /*BoundArch=*/nullptr, Action::OFK_OpenMP)` is never sufficient. The invalid `BoundArch` eventually ends up in `NVPTX::Assembler::ConstructJob` and triggers an assert; I don't think there is any code path with OpenMP offloading where the GPU architecture is set correctly. If I compile a simple test file with
>
>   clang -fopenmp=libomp -fopenmp-targets=nvptx64-nvidia-cuda -c example.c -march=sm_30
>
>
> the error message is the following:
>
>   clang: /llvm/tools/clang/lib/Driver/Tools.cpp:11960: virtual void clang::driver::tools::NVPTX::Assembler::ConstructJob(clang::driver::Compilation&, const clang::driver::JobAction&, const clang::driver::InputInfo&, const InputInfoList&, const llvm::opt::ArgList&, const char*) const: Assertion `gpu_arch != CudaArch::UNKNOWN && "Device action expected to have an architecture."' failed.
>
>
> On a related but different note, leaving out `-march=sm_30` in the clang call above causes an earlier assert to trigger:
>
>   clang: /llvm/tools/clang/lib/Driver/ToolChains.cpp:5049: virtual void clang::driver::toolchains::CudaToolChain::addClangTargetOptions(const llvm::opt::ArgList&, llvm::opt::ArgStringList&) const: Assertion `!GpuArch.empty() && "Must have an explicit GPU arch."' failed.
>
>
> The more appropriate flag would probably be `--cuda-gpu-arch=sm_30`, but that is not recognized.
>
> I thought I'd just report this here as it seemed to me that with the merge of all of @sfantao's code yesterday the OpenMP offloading support should mostly work. If this is not the case or I should report the issue elsewhere, please let me know. Also, I'm not sure if/how this relates to the bug report you mentioned.


These patches do not implement any specific support for GPUs. Only toolchains based on gcc are expected to work. GPUs will require some extra work on the toolchain which is under progress.

In any case, it is not nice to have these assertions when trying an unsupported toolchain. I'll work on a diagnostic so that the driver stops before attempting to create jobs for unsupported toolchains.

Thanks for reporting this!


https://reviews.llvm.org/D21845