[GHC] #12916: GHC 8.0.1 vs GHC HEAD (8.1.20161202) doesn't do inlining and unboxing very well

[GHC]

#12916: GHC 8.0.1 vs GHC HEAD (8.1.20161202) doesn't do inlining and unboxing very
well
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        Reporter:  alexbiehl         |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       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 RyanGlScott):

 I'm having difficulty reproducing this with a build of GHC HEAD at commit
 ddc271e8ed6c5ec5e83dd50c6c5e77955a0e90ac. In fact, the Core I get looks
 just about identical to the one that GHC 8.0.1 produces (with
 `$wempResult`). FWIW, this is using `io-streams-1.3.5.0` and
 `vector-0.11.0.0`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12916#comment:1>
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