protze.joachim added a comment.
I was wondering about the connection to OpenACC, so I had a quick look into the
OpenACC spec to try and understand the background.
OpenACC uses two separate reference counters for structured and unstructured
map. If one of them is >0, the data is present. If both become 0, data is
deleted.
I think, the `hold` modifier is not sufficient to replicate OpenACC behavior.
Consider the following example:
#pragma acc data copy(a) // structured ref := 1
{
#pragma acc exit data delete(a) // dynamic ref := 0
#pragma acc enter data copyin(a) // dynamic ref := 1
} // structured ref := 0 // no copyout because dynamic ref >0
As I understand this will be translated to the following OpenMP:
#pragma omp target data map(ompx_hold, tofrom:a) // ref := 1
{
#pragma omp exit data map(delete:a) // ref := 0 // no action because of hold
#pragma omp enter data map(to:a) // ref := 1
} // ref := 0 // perform map from
I don't think, that trying to map the two openacc reference count to a single
openmp reference count will work in general.
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https://reviews.llvm.org/D106509/new/
https://reviews.llvm.org/D106509
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