[Bug libgomp/85129] [openacc] Document GOMP_OPENACC_DIM

[tschwinge at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85129

Thomas Schwinge <tschwinge at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2018-04-10
     Ever confirmed|0                           |1

--- Comment #3 from Thomas Schwinge <tschwinge at gcc dot gnu.org> ---
(In reply to Tom de Vries from comment #2)
> GOMP_OPENACC_DIM seems to be the odd one here, and we should document
> the non-standard behaviour that it supports being set in main using setenv.

Amongst other things, in
<http://mid.mail-archive.com/87r32z87mx.fsf@euler.schwinge.homeip.net> I
wondered whether "GOMP_OPENACC_DIM parsing conceptually belongs into generic
libgomp code, instead of the nvptx plugin.  (But [...] currently, the nvptx
plugin is the only one supporting/using it.)".

So, I'm not sure we should really document now and thus set the expectation
that 'setenv("GOMP_OPENACC_DIM")' will continue to work as it does now.