In your wiki model (of do's and don'ts), you are probably talking of a C++ subset. If that was to be used, then any compliant compiler would still compile this subset. If this is not the case, this means that subset was probably not compliant in the first place.
Well, it probably evolved but some time ago, Pathscale was not a so efficient compiler as it was marketed. Michael's figures tend to say "yes" nowadays though. Anyway, they did a great job at making it more GCC compatible (newer C++ ABI at that time) than what the original Pro64/Open64/ORC/whatever was. I still wish ENZO is going open source instead of EKOPath. IIRC, for the latter, sources were already available to some research institutions.PathScale EKOPath, for its part, doesn't seem to have anything to do with a GPU; it's just a very efficient C/C++ compiler for the CPU.