[GHC] #8456: Control flow optimisations duplicate blocks

[GHC]

#8456: Control flow optimisations duplicate blocks
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        Reporter:  jstolarek                |            Owner:  jstolarek
            Type:  bug                      |           Status:  new
        Priority:  high                     |        Milestone:
       Component:  Compiler                 |          Version:  7.7
      Resolution:                           |         Keywords:
Operating System:  Unknown/Multiple         |     Architecture:
 Type of failure:  Runtime performance bug  |  Unknown/Multiple
       Test Case:                           |       Difficulty:  Unknown
        Blocking:  8275                     |       Blocked By:
                                            |  Related Tickets:
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Comment (by simonmar):

 Simon - the set of blocks is updated as we go along (there's a foldr at
 the top).  So it does what you're suggesting.

 For a backward goto to a goto, I was imagining that the forward goto would
 be concatenated with its destination.  But it might not be, if the
 destination has multiple predecessors, so I withdraw my suggestion.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8456#comment:4>
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