[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-       |             Owner:
  yamamoto                           |
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.10.2
              Keywords:              |  Operating System:  Unknown/Multiple
          Architecture:              |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
             Test Case:              |        Blocked By:
              Blocking:              |   Related Tickets:
Differential Revisions:              |
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 If we compile the iproute package by GHC, GHC 7.10.2 take much longer than
 GHC 7.8.4. See the report from Travis CI:

 https://travis-ci.org/kazu-yamamoto/iproute/builds/77427248

 I can reproduce this on my local MacBookAir:

 - GHC 7.8.4:  cabal build   8.81s user 0.94s system 103% cpu  9.430 total
 - GHC 7.10.2: cabal build  37.86s user 3.49s system  98% cpu 42.066 total

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