[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 bgamari):

 Replying to [comment:27 simonpj]:
 > >  If we exclude tuple type representations from the known key list then
 they will be loaded from GHC/Tuple.hi with the wrong unique
 >
 > I don't understand. Isn't that what `-- Note [Symbol table
 representation of names]`
 >  is all about? What gets loaded with the wrong key?
 >
 The `TypeRepName` (e.g. `$tc(,,)`).

 > >     Add a special encoding to the symbol table format for type rep
 names. However, it seems odd to add special encodings in the interface
 file format for such a narrow case
 >
 > Not really.  We already have
 > {{{
 > --   A tuple name:
 > --    x is the tuple sort (00b ==> boxed, 01b ==> unboxed, 10b ==>
 constraint)
 > --    y is the thing (00b ==> tycon, 01b ==> datacon, 10b ==> datacon
 worker)
 > --    z is the arity
 > }}}
 > Data con workers seems similarly specialised.  It's just an encoding for
 a large family.  Maybe 11b for rep-name?

 Fair enough. Alright; I'll move ahead with this option then.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12357#comment:28>
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