[GHC] #8635: GHC optimisation flag ignored when importing a local module with derived type classes

[GHC]

#8635: GHC optimisation flag ignored when importing a local module with derived
type classes
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        Reporter:  NeilMitchell      |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.6.3
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by NeilMitchell):

 Thanks for the explanation. As long as it doesn't happen at `-O1` (which
 it won't, from your explanation) it won't actually matter to me in
 practice. It does mean that at `-O0` the effect of things like `-O2` is
 dependent on what modules you import, what functions they use, what order
 things are processed by `ghc --make` etc.

 I suspect that inlining very small things like `$` can only be a win in
 terms of code size. Seeing them in the output, even at `-O0`, was a little
 surprising (although entirely understandable).

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8635#comment:3>
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