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

[GHC]

#14001: Inlining does not work between modules
-------------------------------------+-------------------------------------
        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:                    |
-------------------------------------+-------------------------------------

Comment (by mpickering):

 Here is a smaller reproduction. I don't think a lot of the type family
 stuff is necessary for the reproduction.

 https://github.com/mpickering/musical-spork

 You can build it with `cabal new-build`.

 I noticed that the `Strict` language extension was enabled and so the
 definitions were not in fact equivalent. This makes the performance
 difference less surprising.

 If you modify the definition of `(.)` in `A.hs` to remove the bang then
 the program gets a lot slower.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14001#comment:6>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler