[GHC] #14626: No need to enter a scrutinised value

[GHC]

#14626: No need to enter a scrutinised value
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        Reporter:  heisenbug         |                Owner:  heisenbug
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:  performance
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13861            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 > Name.hs:111 is a strict record field BTW. Does this ring a bell? Why is
 it OtherCon _ <- idUnfolding id but not tagged? Is it possibly implicitly
 unpacked?

 Can you explain more?  I can't make sense of this paragraph.  What is "it"
 that might be implicitly unpacked?  What does it mean to be "implicitly
 unpacked" ?

 One good thing would be to distill a tiny example, and it sounds as if you
 have enough insight to do that now.  E.g. perhaps you are saying that
 {{{
 data T = MkT ![Int]
 f (MkT xs) = xs
 }}}
 returns a badly-tagged pointer?  If so, just compile that tiny program and
 see.  etc.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14626#comment:14>
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