[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
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        Reporter:  alexbiehl         |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      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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Description changed by alexbiehl:

@@ -10,1 +10,1 @@
- I could reproduce the problem on OSX and Windows with GHC 7.10.3. Haven't
+ I can reproduce the problem on OSX and Windows with GHC 7.10.3. Haven't

New description:

 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 can 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#comment:1>
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