[GHC] #12603: INLINE and manually inlining produce different code

[GHC]

#12603: INLINE and manually inlining produce different code
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        Reporter:  bgamari           |                Owner:  bgamari
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.0.1
      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 MikolajKonarski):

 > I think that's very problematic.  Currently GHC decides on a call-site-
 by-call-site basis whether to inline a given function.[...]

 When there is only one call site, IMHO it's reasonable that the outcome
 should be reproducible with either INLINE or NOINLINE (and it is not
 currently, see above).

 > INLINE/NOINLINE let you take control; otherwise you are letting GHC
 decide.

 I'm all for letting GHC outsmart me, but I'd like to be able to then fix
 the result GHC came up with and tweak it further or tweak other bits of
 code, keeping this part constant, or stick to it in order to debug my
 program with slightly varying other portions of code or easily come up
 with a minimized example for a GHC bug, without GHC sneakily intefering.
 Currently I can't. Let's move the discussion to
 ​https://ghc.haskell.org/trac/ghc/ticket/12747#ticket where I also suggest
 that INLINABLE+inline+noinline should let the programmer reproduce GHC
 choices in the multi-call-site case.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12603#comment:12>
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