[GHC] #11095: -O0 -g slows GHC down on list literals (compared to -O0 without -g)

[GHC]

#11095: -O0 -g slows GHC down on list literals (compared to -O0 without -g)
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        Reporter:  slyfox            |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  phab:D3001
       Wiki Page:                    |
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Comment (by bgamari):

 There is a `nubBy` in `Debug` which uses `tickishContains` which would
 make this N^2. This is likely the reason why the above patch made such a
 difference.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11095#comment:7>
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