[GHC] #10818: GHC 7.10.2 takes much longer to compile some packages

[GHC]

#10818: GHC 7.10.2 takes much longer to compile some packages
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        Reporter:  kazu-yamamoto     |                Owner:
            Type:  bug               |               Status:  new
        Priority:  high              |            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):
       Wiki Page:                    |
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Comment (by rwbarton):

 I have to say I don't really understand `cabal install` taking 30 seconds
 either; unless it includes either building your dependencies (random, mtl)
 or the slowest operation known to man, "Updating documentation index" in
 the global package database.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10818#comment:12>
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