[GHC] #7258: Compiling DynFlags is jolly slow

[GHC]

#7258: Compiling DynFlags is jolly slow
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        Reporter:  simonpj           |                Owner:  simonpj
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.6.1
      Resolution:                    |             Keywords:  deriving-perf
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 tdammers):

 Replying to [comment:48 simonpj]:
 > Is the labelling in the graph after comment:46 correct?  read-appl looks
 worst by a long way, which wasn't true bef.re  Ditto geline-appl seems
 worse than getline (which is invisible).

 Yes, it is correct; the difference between this new graph and the previous
 one is that the new one uses `-O2`, while the old one doesn't use any
 optimizations. The profiler breakdown looks radically different between
 the optimized and unoptimized versions, for *all* examples - RegAlloc-
 linear and ppr, which are the most serious offenders in the unoptimized
 run, account for less than 1% of execution time in the optimized case.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7258#comment:50>
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