[GHC] #7367: Optimiser / Linker Problem on amd64

[GHC]

#7367: Optimiser / Linker Problem on amd64
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        Reporter:  wurmli                   |            Owner:
            Type:  bug                      |           Status:  new
        Priority:  normal                   |        Milestone:  7.8.1
       Component:  Build System             |          Version:  7.6.1
      Resolution:                           |         Keywords:
Operating System:  Linux                    |     Architecture:  x86_64
 Type of failure:  Runtime performance bug  |  (amd64)
       Test Case:                           |       Difficulty:  Unknown
        Blocking:                           |       Blocked By:
                                            |  Related Tickets:
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Comment (by simonpj):

 I don't think `flopS` uses its continuation linearly!
 {{{
 flopS :: Perm -> (Int -> IO a) -> IO a
 flopS !xs f = do
         let go !acc = do
                 k <- peekElemOff xs 0
                 if k == 0 then f acc else flop (fromIntegral k) xs >> go
 (acc+1)
         go 0
 }}}
 One call to `flopS` will give many calls to its argument `f`.  Actually
 the new cardinality analyser does spot (and exploit) this kind of
 linearity.

 I'd be happy to hear more ideas as you get more familiar with GHC.

 Simon

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7367#comment:8>
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