[GHC] #7647: UNPACK polymorphic fields

[GHC]

#7647: UNPACK polymorphic fields
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        Reporter:  liyang            |                   Owner:
            Type:  feature request   |                  Status:  new
        Priority:  normal            |               Milestone:  7.12.1
       Component:  Compiler          |                 Version:  7.6.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:  #3990             |  Differential Revisions:
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Changes (by thomie):

 * cc: MikeIzbicki (added)
 * related:  3990 => #3990


Comment:

 See this [https://izbicki.me/blog/fast-nearest-neighbor-queries-in-
 haskell.html blog post] for a request for "polymorphic unpacking", in the
 section "Lesson 1: Polymorphic code in GHC is slower than it needs to be."

 The blog post also refers to a
 [https://www.reddit.com/r/haskell/comments/29onpf/why_does_ghc_always_box_polymorphic_fields_in/
 reddit discussion] on the subject.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7647#comment:10>
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