[PATCH,nvptx] Use CUDA driver API to select default runtime launch, geometry

[Tom de Vries]

On 08/01/2018 12:18 PM, Tom de Vries wrote:

> I think we need to add and handle:
> ...
>   CUDA_ONE_CALL_MAYBE_NULL (cuOccupancyMaxPotentialBlockSize)
> ...
> 

I realized that the patch I posted introducing CUDA_ONE_CALL_MAYBE_NULL
was incomplete, and needed to use the weak attribute in case of linking
against a concrete libcuda.so.

So, I've now committed a patch implementing just CUDA_ONE_CALL_MAYBE_NULL:
"[libgomp, nvptx] Handle CUDA_ONE_CALL_MAYBE_NULL" @
https://gcc.gnu.org/ml/gcc-patches/2018-08/msg00447.html . You can use
"CUDA_CALL_EXISTS (cuOccupancyMaxPotentialBlockSize)" to test for
existence of the function in the cuda driver API.

> The patch doesn't build in a setup with
> --enable-offload-targets=nvptx-none and without cuda, that enables usage
> of plugin/cuda/cuda.h:
> ...
> /data/offload-nvptx/src/libgomp/plugin/plugin-nvptx.c:98:16: error:
> ‘cuOccupancyMaxPotentialBlockSize’ undeclared here (not in a function);
> did you mean ‘cuOccupancyMaxPotentialBlockSizeWithFlags’?
>  CUDA_ONE_CALL (cuOccupancyMaxPotentialBlockSize) \
> ...
> 

I've committed a patch "[libgomp, nvptx, --without-cuda-driver] Don't
use system cuda driver" @
https://gcc.gnu.org/ml/gcc-patches/2018-08/msg00348.html .

Using --without-cuda-driver should make it easy to build using the
dlopen interface without having to de-install the system libcuda.so.

Thanks,
- Tom