[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:  new
        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):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by simonpj):

 That's quite right.  After thinking it briefly (ie I might well be wrong)
 I don't see a good way to fix it.

 The trouble is that the fixpoint iteration starts from an unsound
 assumption: that the function is hyperstrict.  It then iterates to a sound
 conclusion.  So if you have to abandon the process, the current
 approximation is unsound. So you can't just attach it.

 I don't see how to take advantage of the work done so far.

 Mind you, 10 iterations is a lot!  I think it prints a warning: worth
 investigating.  If it's rare enough it probably doesn't matter much.

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12368#comment:1>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler