[GHC] #11226: Performance regression (involving sum, map, enumFromThenTo)

[GHC]

#11226: Performance regression (involving sum, map, enumFromThenTo)
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        Reporter:  j.waldmann        |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      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:                    |
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Changes (by nomeata):

 * cc: nomeata (added)


Comment:

 No time to look deeply, but: Does the problem go away if the list is not
 statically known and thus prevented from floated out, e.g.:

 {{{#!hs
 main = print $ foo (2^24-1)

 foo n = sum $ map bitcount [0, 4 .. n]
 {-# NOINLINE foo #-}

 bitcount :: Int -> Int
 bitcount x =
   if x > 0 then let (d,m) = divMod x 2 in bitcount d + m else 0
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11226#comment:1>
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