According to this, C-- is still a large part of the Glasgow Haskell Compiler. It looks like (Fig 5.2) code goes into C-- before being translated to LLVM.
Uh, I believe that the GHC C-- (Cmm) is one of the dozen different C--es that have nothing in common with this project save for the name.
Given that Simon Peyton Jones is listed as a co-author on several of the papers, I find that a bit too coincidental to be true.
This thing is written in ML, not in Haskell, and the GHC docs themselves claim that Cmm (the GHC thingy) is "is rather like C--. The syntax is almost C-- (a few constructs are missing), and it is augmented with some macros that are expanded by GHC's code generator". So "GHC's Cmm/C--" sounds rather like an independent reimplementation of a superset of a subset of "this C--".
It literally can't be an "independent reimplementation" if one person played a major role in both of them.
Domain specific dialect?
The GHC C-- is a subset of the full Norman Ramsey C--