Initialize target library with only a target data

[hahnjo]

This corner case may occur in benchmarks that want to measure data movement.

I didn't know how to implement a test case for the global initializer, but I could verify with a simple program:

int main(int argc, char* argv[])
{
        int a = 0;
        #pragma omp target data map(a)
        {
        }

        return 0;
}

[sfantao]

Hi hahnjo,

Thanks for the patch! However, I don't think we should do a registration for this case. Avoiding a registrations is something we should always do, as long as we provide the right functionality. If a user is interested in measuring data movements he should do something like:

int a;
#pragma omp target data map(alloc:a)
{
  // start timer
  #pragma omp target update to(a)
  // stop timer

  #pragma omp target 
  {} 
}

Regards,
Samuel