[GHC] #11146: Manual eta expansion leads to orders of magnitude less allocations

[GHC]

#11146: Manual eta expansion leads to orders of magnitude less allocations
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        Reporter:  niteria           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by niteria):

 > Where is the bug in the report?

 I'm not convinced this is a bug. I've created this in response to this
 comment: https://phabricator.haskell.org/D1537#inline-12820.

 > Do you have a (hopefully small and self-contained) bit of code where you
 think “duh, obviously the compiler should be a allowed to eta-expand
 here”, but it does not?

 I can't tell if GHC should be allowed to eta-expand in my example, but the
 fact that it decided to eta-expand in a very similar situation where I
 didn't have mutually recursive functions suggests that it might be able
 to.

 > Do things are better if all the relevant code is in one module, with an
 explicit export list that does not include any of the functions you’d like
 to see eta-expanded?

 Yes, it's enough to not export the functions I want eta-expanded.
 Unfortunately that's exactly what I want do in Phab:D1537 because I'm
 composing a computation from smaller pieces from several modules.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11146#comment:3>
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