[GHC] #12367: Commit adding instances to GHC.Generics regression compiler performance

[GHC]

#12367: Commit adding instances to GHC.Generics regression compiler performance
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        Reporter:  bgamari           |                Owner:  bgamari
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.0.2
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  Generics
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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Comment (by bgamari):

 In our call yesterday Simon expressed skepticism that the performance
 regression is entirely due to a larger interface file. More like, he said,
 is that an interface is now being loaded which wasn't previously
 necessary. Indeed this is the case: interface files for both
 `GHC.Generics` and `GHC.Ptr` are now loaded while compiling
 `Data.Foldable` but were not previously,

 {{{
 $ grep 'Reading interface' dump-if.log
 Reading interface for Prelude; reason: Prelude is directly imported
 Reading interface for Geomfuns;
 Reading interface for Auxprogfuns;
 Reading interface for GHC.Base;
 Reading interface for GHC.Float;
 Reading interface for GHC.Types;
 Reading interface for Data.Foldable;
 Reading interface for GHC.List;
 Reading interface for GHC.Show;
 Reading interface for GHC.Prim;
 Reading interface for GHC.Classes; reason: Need decl for Eq
 Reading interface for GHC.Num; reason: Need decl for Num
 Reading interface for GHC.Stack.Types; reason: Need decl for SrcLoc
 Reading interface for GHC.Integer.Type;
 Reading interface for GHC.Generics; reason: Need decl for V1
 Reading interface for GHC.Ptr; reason: Need decl for Ptr
 Reading interface for Data.Monoid; reason: Need decl for Sum
 Reading interface for Data.Proxy; reason: Need decl for Proxy
 Reading interface for Data.Either; reason: Need decl for Either
 Reading interface for GHC.Arr; reason: Need decl for Array
 Reading interface for GHC.Tuple;
 Reading interface for GHC.Enum; reason: Need decl for enumFromTo
 Reading interface for GHC.CString;
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12367#comment:7>
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