[GHC] #12191: 7% allocation regression in Haddock performance tests

[GHC]

#12191: 7% allocation regression in Haddock performance tests
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        Reporter:  bgamari           |                Owner:  niteria
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #10482            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by niteria):

 It appears that `checkFamInstConsistency` is sensitive to `Module`
 ordering.
 Making it a noop also reduces allocations by `9%`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12191#comment:9>
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