[GHC] #9561: Clean up mergeSATInfo

[GHC]

#9561: Clean up mergeSATInfo
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              Reporter:  dfeuer      |            Owner:
                  Type:  task        |           Status:  patch
              Priority:  normal      |        Milestone:  7.8.4
             Component:  Compiler    |          Version:  7.9
            Resolution:              |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Easy (less than 1
       Type of failure:              |  hour)
  None/Unknown                       |       Blocked By:
             Test Case:              |  Related Tickets:
              Blocking:              |
Differential Revisions:              |
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Comment (by simonpj):

 Let's do #9374 before implementing this patch.  Right now SAT is only run
 when you say `-fstatic-argument-transformation` (ie almost never) so it
 would be hard to test this (doubtless excellent) refactoring thoroughly.

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9561#comment:2>
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