[GHC] #5218: Add unpackCStringLen# to create Strings from string literals

[GHC]

#5218: Add unpackCStringLen# to create Strings from string literals
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        Reporter:  tibbe             |                Owner:  thoughtpolice
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.0.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #5877 #10064      |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonmar):

 We'll need to think about how we want to do this for GHCi.  I presume we
 can't do unarise on Core because it can't generate type-correct Core,
 right @osa1?  It seems like a lot of trouble to have a whole pass just for
 strings in GHCi, especially since it overlaps with what unarise does.

 Perhaps it could be handled in the byte code generator directly?

 Anyway, feel free to put your patch up on Phabricator for review.  If it
 depends on submodule changes, I believe the right way to handle those is
 to fork the submodule on github and make the `.gitmodule` file point to
 your fork, at least while the patch is in review, and then when pushing,
 revert the `.gitmodules` changes and push to the upstream submodules
 first.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5218#comment:50>
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