[GHC] #7803: Superclass methods are left unspecialized

[GHC]

#7803: Superclass methods are left unspecialized
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        Reporter:  akio              |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.6.2
      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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Comment (by bgamari):

 Here is a nofib comparison based on
 38af3d1db2889423a12a2232b9d52181bba23d75 with and without the following
 patch,

 {{{#!patch
 diff --git a/compiler/simplCore/SimplCore.hs
 b/compiler/simplCore/SimplCore.hs
 index 6badbf8..c573b45 100644
 --- a/compiler/simplCore/SimplCore.hs
 +++ b/compiler/simplCore/SimplCore.hs
 @@ -182,7 +182,7 @@ getCoreToDo dflags
                         (base_mode { sm_phase = InitialPhase
                                    , sm_names = ["Gentle"]
                                    , sm_rules = rules_on   -- Note [RULEs
 enabled in SimplGently]
 -                                  , sm_inline = False
 +                                  , sm_inline = True
                                    , sm_case_case = False })
                            -- Don't do case-of-case transformations.
                            -- This makes full laziness work better
 }}}

 Unfortunately things don't look terribly promising,
 {{{
         Program           Size    Allocs   Runtime   Elapsed  TotalMem
 --------------------------------------------------------------------------------
             Min          -0.3%    -95.0%     -0.6%     -1.2%      0.0%
             Max          +0.9%    +10.6%    +14.3%    +14.3%   +100.0%
  Geometric Mean          +0.4%     -2.8%     +1.6%     +1.5%     +0.8%
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7803#comment:13>
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