[GHC] #12357: Increasing maximum constraint tuple size significantly blows up compiler allocations

[GHC]

#12357: Increasing maximum constraint tuple size significantly blows up compiler
allocations
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           Reporter:  bgamari        |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  7.10.3
           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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 In July 2015 (dd3080fe0263082f65bf2570f49189c277b12e28) the maximum
 constraint tuple size was raised from 16 to 62 to address #10451. It turns
 out that this change is apparently one of the larger compile-time
 regressions in recent GHC history. For instance, the nofib
 `real/fulsom/Shapes.hs` module regresses by 16% in both compiler
 allocations and compile time.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12357>
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