[GHC] #13270: Make Core Lint faster

[GHC]

#13270: Make Core Lint faster
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           Reporter:  rwbarton       |             Owner:
               Type:  task           |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.1
           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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 Not using `-dcore-lint` makes the validate build 25% faster overall. See
 https://perf.haskell.org/ghc/#compare/639e702b6129f501c539b158b982ed8489e3d09c/0206750fcd3fe2299419a9020ec39fa557a866d0.

 We should at least profile it and check for anything egregiously
 inefficient.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13270>
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