[RFC] Offloading Support in libgomp

[Jakub Jelinek]

On Thu, Jul 17, 2014 at 04:30:15PM +0400, Ilya Verbin wrote:
> 2014-07-17 11:51 GMT+04:00 Thomas Schwinge <thomas@codesourcery.com>:
> >> +  plugin_path = getenv ("LIBGOMP_PLUGIN_PATH");
> >
> > What is the benefit of making this an environment variable that the user
> > set to set, LIBGOMP_PLUGIN_PATH, as opposed to hard-coding it to
> > somewhere inside the GCC installation directory ([...]/lib/libgomp/*.so)?
> > (There, it can still be overridden; dlopen obeys DT_RPATH/DT_RUNPATH, and
> > LD_LIBRARY_PATH.)  Hard-coding it would make libgomp testing a bit
> > easier, and it generally seems to make sense to me that the compiler
> > (libgomp) should be able to locate its own resources, and I don't think
> > the plugin search path is something that a user generally would want to
> > override -- or is your use case indeed that the plugin is not built as
> > part of libgomp's build process?  (But, in this case you still could use
> > LD_LIBRARY_PATH to have it found.)
> 
> We invented this environment variable almost a year ago, when we
> didn’t fully understand how all the parts will work together. So for
> now, likely, your proposal is better.
> Jakub, what do you think?

Yeah, certainly.  Though, ideally the path it looks at should be relative
to the directory where libgomp is installed, and I'm afraid it is hard to
figure out portably where it was loaded from, and DT_RPATH/DT_RUNPATH on
libgomp would affect all dlopen calls, not just the loading of the plugins.
Not sure if one can use at least on Linux ${ORIGIN} in dlopen and what
exactly will it expand to.

	Jakub