[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):  Phab:D2400
       Wiki Page:                    |
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Comment (by simonpj):

 Why/how does the `TcTypeable` impl rely on them being there???   There
 jolly well ought to be a comment to say so.

 All I see is

 * `knownKeyNames` used in building `knownKeyNamesMap` in `BinIface`.
 Waste of time having tuples in there because they are treated specially by
 `BinIface`.

 * Initialising the name cache in `HscMain`.

 And that's really it.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12357#comment:23>
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