[GHC] #14208: Performance with O0 is much better than the default or with -O2, runghc performs the best

GHC ghc-devs at haskell.org
Tue Mar 27 23:59:35 UTC 2018


#14208: Performance with O0 is much better than the default or with -O2, runghc
performs the best
-------------------------------------+-------------------------------------
        Reporter:  harendra          |                Owner:  osa1
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.1
      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:                    |
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Comment (by mpickering):

 Another possible answer is that your library has a lot of recursive
 functions in it and the base types are written in CPS which means things
 don't optimise too well. Again, this is not an answer as to why the
 optimiser makes the program slower.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14208#comment:36>
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