DPH tests

[Simon Peyton-Jones]

| However, the code likely to be causing the problem is in the backend
| library, and adding -fno-spec-constr (or otherwise reducing the
| optimisation level) should fix it.
| 
| TooMuchInlining + ForceSpecConstr = BOOM!.

Yes, this is a delicate point.  DPH relies on aggressive inlining, and aggressive use of SpecConstr.  These are not things that it's easy for someone unfamiliar with what's going on to debug.  Amos was working on the SpecConstr part, I believe.

Ben, would you be able to look at the failing tests and see what's going on?  There isn't much point in running them if they fail anyway -- then we aren't checking that the vectoriser is working.

If there is something I can do to help, just say.

Simon