We are getting close. We have been trying to stabilize a chunk of functionality, and fix up the commit messages and the test suite so we could submit a patch. I would anticipate a couple of more weeks. Even before then we will make something available for folks who feel competent to clone a repository on GitHub and give them a try. Here is a branch you could try now:
GitHub - Ada-Rapporteur-Group/gcc-mirror at devel/arg-proto/parallel-exp-par-1