There is a note at the top of SpecConstr which says

  ToDo [Oct 2013]                                                                     
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  1. Nuke ForceSpecConstr for good (it is subsumed by GHC.Types.SPEC in ghc-prim) 
  2. Nuke NoSpecConstr 

ForceSpecConstr still exists so this ticket is to track the progress made on removing it.

It isn't clear to me why it is ok to get rid of NoSpecConstr (which prevents SpecConstr firing) either.