[GHC] #9669: Long compile time/high memory usage for modules with many deriving clauses

[GHC]

#9669: Long compile time/high memory usage for modules with many deriving clauses
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              Reporter:  snoyberg    |            Owner:
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:
             Component:  Compiler    |          Version:  7.8.3
            Resolution:              |         Keywords:
      Operating System:  Linux       |     Architecture:  x86_64 (amd64)
       Type of failure:  Compile-    |       Difficulty:  Unknown
  time performance bug               |       Blocked By:
             Test Case:              |  Related Tickets:
              Blocking:              |
Differential Revisions:              |
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Comment (by snoyberg):

 I've attached a file (generate.hs) to hopefully give a simpler view of the
 problem. This module (which depends only on base) will generate a Haskell
 source file which itself depends only on base. You can test this out with
 `runghc generate.hs > Bar.hs && time ghc --make Bar.hs +RTS -s`. You can
 also edit the generate.hs file to change which classes are derived and how
 many datatypes are generated.

 In my testing, without switching optimization flags, I noticed the
 following (all results generated when using 200 types):

 * All classes: 247MB max residency, 17.7s runtime
 * Removing `Generic`: 109MB, 13.4s
 * Removing `Generic` and `Data`: 78MB, 9.4s
 * Removing all but `Typeable`: 23MB, 1.1s
 * Removing all deriving: 13MB, 0.6s

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9669#comment:1>
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