[GHC] #11688: Bytestring break failing rewrite to breakByte and failing to eliminate boxing/unboxing

[GHC]

#11688: Bytestring break failing rewrite to breakByte and failing to eliminate
boxing/unboxing
-------------------------------------+-------------------------------------
           Reporter:  alexbiehl      |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  7.10.3
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 Tyson Whitehead gives a detailed description of the problem
 [https://github.com/haskell/bytestring/issues/70 here].

 Key points:
   - Program fails to rewrite {{{ ByteString.break (== x) chunk }}} to {{{
 ByteString.breakByte x chunk }}}
   - Missed unboxing opportunity (which led to 34gb additional allocations,
 which is why he noticed it)

 I could reproduce the problem on OSX and Windows with GHC 7.10.3. Haven't
 tested Linux.

 I repost it here to make sure it doesn't go unnoticed.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11688>
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