[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)
-------------------------------------+-------------------------------------
        Reporter:  nh2               |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       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:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by simonpj):

 Good to know that's it.

 The program in rep.hs is rather unusual because it has a ''constant''
 list, not dependent on input data.  Real programs usually depend on input
 data.  So this probem may be less of a probem in practice than in
 benchmarks.

 It would be great if someone felt able to dig into #7206 and figure out
 why it's not a straight win

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8763#comment:30>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler