[GHC] #12368: Demand Analyzer: Cunnig plan not adhered to with aborting fixpoint interation

[GHC]

#12368: Demand Analyzer: Cunnig plan not adhered to with aborting fixpoint
interation
-------------------------------------+-------------------------------------
        Reporter:  nomeata           |                Owner:
            Type:  bug               |               Status:  patch
        Priority:  low               |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D2392
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by nomeata):

 Fixed the problem, by adding a topDmd demand on all free variables
 mentioned in the strictness signature of the binders to `lazy_fvs`, before
 throwing away the strictness signature. Fixes this test case. Code on Phab
 and the branch, currently awaiting validation.

 While I am at it: `splitFVs` in `Demand.hs` has some intricate special
 handling for thunks, without any comment or justification. Do you have any
 idea why that is there, and whether it is still required?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12368#comment:14>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler