[GHC] #1290: ghc runs preprocessor too much

[GHC]

#1290: ghc runs preprocessor too much
-------------------------------------+-------------------------------------
        Reporter:  guest             |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:  7.12.1
       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 Revisions:
-------------------------------------+-------------------------------------
Changes (by ezyang):

 * milestone:  ⊥ => 7.12.1


Comment:

 What if this information was cached in the interface file? Essentially,
 interface files should contain enough information for us to construct a
 `ModSummary`, and they are as recent as the source file we can just use
 this directly. (And we're going to read the interface file anyway shortly
 thereafter do check for recompilation avoidance.)

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1290#comment:7>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler