[GHC] #13317: exprIsConApp_maybe should deal better with strings

[GHC]

#13317: exprIsConApp_maybe should deal better with strings
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        Reporter:  simonpj           |                Owner:  (none)
            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 Simon Peyton Jones <simonpj@…>):

 In [changeset:"a6e13d502ef46de854ec1babcd764ccce68c95e3/ghc"
 a6e13d50/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="a6e13d502ef46de854ec1babcd764ccce68c95e3"
 Make exprIsConApp_maybe work better for literals strings

 There are two things here

 * Use exprIsLiteral_maybe to "look through" a variable bound
   to a literal string.

 * Add CONLIKE to the NOINLINE pragma for unpackCString# and
   unpackCStringUtf8#

 See Trac #13317, Trac #10844, and
 Note [exprIsConApp_maybe on literal strings] in CoreSubst

 I did a nofib run and got essentially zero change except for one
 2.2% improvement in allocation for 'pretty'.
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13317#comment:1>
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