[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
      Resolution:                    |             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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Description changed by bgamari:

@@ -5,1 +5,1 @@
- `real/fulsom/Shapes.hs` module regresses by 16% in both compiler
+ `real/fulsom/Shapes.hs` module regresses by around 15% in both compiler

New description:

 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 around 15% in both compiler
 allocations and compile time.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12357#comment:1>
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