[GHC] #15164: Slowdown in ghc compile times from GHC 8.0.2 to GHC 8.2.1 when doing Called arity analysis

[GHC]

#15164: Slowdown in ghc compile times from GHC 8.0.2 to GHC 8.2.1 when doing Called
arity analysis
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        Reporter:  flip101           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.2.1
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:  x86_64
 Type of failure:  Compile-time      |  (amd64)
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"f2ce86c2edc0840f5e731d5286a2a5e484263e3f/ghc" f2ce86c/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="f2ce86c2edc0840f5e731d5286a2a5e484263e3f"
 Do better sharing in the short-cut solver

 Trac #15164 showed that it sometimes really matters to share
 sub-proofs when solving constraints.  Without it, we can get
 exponentialy bad behaviour.

 Fortunately, it's easily solved.
 Note [Shortcut try_solve_from_instance] explains.

 I did some minor assocaited refactoring.
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15164#comment:18>
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