[GHC] #9370: unfolding info as seen when building a module depends on flags in a previously-compiled module

[GHC]

#9370: unfolding info as seen when building a module depends on flags in a
previously-compiled module
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        Reporter:  carter            |                Owner:  richardfung
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  7.8.3
      Resolution:                    |             Keywords:  newcomer,
                                     |  Inlining
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #8635             |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by richardfung):

 Am I correct in thinking the right way to test this is to write a function
 which would only be inlined if the INLINE pragma is there? Otherwise, the
 function would be inlined even in source files that import it with
 OPTIONS_GHC -O0 right?

 I was completely unfamiliar with inlining before this ticket so please
 bear with me. It seems like imported modules are still inlined even if
 OPTIONS_GHC -O0 is set if you run ghc --make -O. The documentation also
 says that -O enables cross module inlining so I'm guessing even if the
 source file has OPTIONS_GHC -O0, inlinings from other modules are still
 supposed to happen?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9370#comment:34>
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