[GHC] #8763: forM_ [1..N] does not get fused (10 times slower than go function)

[GHC]

#8763: forM_ [1..N] does not get fused (10 times slower than go function)
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        Reporter:  nh2               |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  7.6.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #7206             |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by sgraf):

 I just ran some quick `quickCheck $ withMaxSuccess 100000 $ \i j k -> take
 1000 [i,j..k] == take 1000 (efdtInt (unI# i) (unI# j) (unI# k))` tests and
 both versions pass. Given that simonpj's is much more to the point, let's
 run with that one! Although the duplicate `n` has potential to cause
 pain...

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8763#comment:55>
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