[GHC] #8901: (very) bad inline heuristics

[GHC]

#8901: (very) bad inline heuristics
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        Reporter:  heisenbug         |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.7
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by heisenbug):

 Replying to [comment:3 simonpj]:
 > Can you explain what the bug in GHC is?  And (as Ashley asks) why you
 believe it's a bug in GHC and not the library?

 It is hard to pinpoint. There has been some rope-pulling between me and
 Ashley (on the dev list/in private) as he has not been keen of accepting
 my patch (so far) asking whether it could be a GHC bug. I tend to agree,
 as a quality inliner should not attempt to inline (e.g.) `formatTime`
 which has 8 alternatives and is called from 10+ sites. It would be
 interesting to see whether any bloat-controlling measures failed detecting
 this case, esp. as `Format.hs` appears to be a relatively benign source
 file. Some lessons might be learnt from this.

 OTOH, a library author should keep in eye how popular compilers digest the
 lib.

 I am ending up stuck between a rock and a hard place.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8901#comment:4>
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