[Patch][OpenMP/OpenACC/Fortran] Fix mapping of optional (present|absent) arguments

[Tobias Burnus]

Early *PING*.

Tobias Burnus wrote:
> This patch does two things regarding explicit and automatical variable 
> mapping to offloaded devices:
>
> * Fixes bugs with optional arguments, which are present. They were 
> mapped but the mapping had issues causing run-time failures.
> * It now also handles absent optional arguments.
>
> Compared to the previous patch set,** I added several OpenMP test 
> cases – and fixed the fallout.
>
> Except for trivial changes to libgomp/oacc-mem.c and omp-low.c, all 
> changes are in fortran/trans-openmp.c and only affect optional arguments.
>
> The patch was bootstrapped and tested on x86_64-gnu-linux w/o 
> offloading-support configured and with nvptx offloading.
>
> Tobias
>
> ** Included in the attached patch are the following previously posted 
> patches: [1] the trivial libgomp/oacc-mem.c change, [2] only the 
> remaining single-line change in omp-low.c, [3] the trans-openmp.c 
> changes (which had to be modified+extended), and [5] the test cases. 
> ([2] and [4] are already in GCC 10.) See: 
> https://gcc.gnu.org/ml/gcc-patches/2019-07/threads.html#00960 for the 
> original patches.
>
> PS: For full OpenMP support, (absent) optional arguments also needed 
> to be handled for data-share clauses.
>