[GHC] #1290: ghc runs preprocessor too much

[GHC]

#1290: ghc runs preprocessor too much
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        Reporter:  guest             |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Driver            |              Version:  6.7
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by ezyang):

 This is related to #618, as if `ghc --make` remembered dependency
 information it would not need to preprocess *stable* modules.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1290#comment:9>
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