[GHC] #12847: ghci -fobject-code -O2 doesn't do the same optimisations as ghc --make -O2

[GHC]

#12847: ghci -fobject-code -O2 doesn't do the same optimisations as ghc --make -O2
-------------------------------------+-------------------------------------
        Reporter:  nh2               |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Other             |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by rwbarton):

 Although you don't say so explicitly, you seem to be invoking `ghci` and
 then running `:set -fforce-recomp -fobject-code -O2 -v` at the prompt.
 Does the same happen with `ghci -fforce-recomp -fobject-code -O2 -v`?

 This could be because of #9370, where decisions about whether to inline a
 function are effectively made when reading the interface file in which the
 function is defined; and at that point you may not have `-O2` set yet.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12847#comment:1>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler