[Bug fortran/126940] [17 Regression] testsuite fails for libgomp.oacc-fortran/host_data-5.F90

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126940

--- Comment #8 from Tobias Burnus <burnus at gcc dot gnu.org> ---
(In reply to Mikael Morin from comment #5)
> We used to pack-in/unpack-out assumed-shape target arguments before the
> regressing patch. That was wrong because the argument may have pointers
> associated with it on entry, and pointers may be newly associated with it
> during  procedure execution.

It sound wrong in general – as there shouldn't be any reason to do so for
assumed-shape variables in general, unless there is a 'contiguous' argument...

Thanks for the enlightenment.


(In reply to Jerry DeLisle from comment #6)
> Is this an existing problem uncovered by my commit or caused by my commit. I
> have never tested with those options before, so did not see anything here.

I think we have two issues here:

(1) The testcase now fails because of the change. - Like several testcases, it
does not fail in all combinations (hardware, flags) but in some.
This issue can be fixed by changing expected output (dg-...) or adding² the
'contiguous' attribute to the dummy argument.


(2) Suboptimal code gen: we know that the memory must be contiguous¹ and,
hence, there shouldn't be a packed check. This can be fixed (cf. attachment
65371)³ by modifying the interface in the OpenACC module. - This also fixes the
issue (1).² 


¹This is technically required - and, hence, the spec requires the user to pass
only contiguous memory.

²Likely those variants require undoing the changes to the test file, added in
commit r17-3342-gf3943597388db4.

³There are some known bugs (fails if compiled as interfaces aren't
consistently) and omissions (not tested, .map file needs to be updated).

* * *

TODO: Decide for an option - and implement it.