[GHC] #14001: Inlining does not work between modules

[GHC]

#14001: Inlining does not work between modules
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        Reporter:  danilo2           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:
       Component:  Compiler          |              Version:  8.0.2
      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 simonpj):

 I'm confused.   In Matthew's repro case,

 * Function `(.)` is defined in module `A` and not exported.
 * So far as I can see, it is inlined at all its call sites in `A`.
 * The comment says that adding a bang to one of `(.)`'s arguments makes a
 big perf difference.  That does not sound like a bug to me.

 Can someone explain what the problem is?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14001#comment:7>
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