[GHC] #10397: Compiler performance regression 7.6 -> 7.8 in elimCommonBlocks

[GHC]

#10397: Compiler performance regression 7.6 -> 7.8 in elimCommonBlocks
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        Reporter:  TobyGoodwin       |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.8.4
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |  performance
 Type of failure:  None/Unknown      |            Architecture:
      Blocked By:                    |  Unknown/Multiple
 Related Tickets:                    |               Test Case:  see ticket
                                     |                Blocking:
                                     |  Differential Revisions:
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Comment (by nomeata):

 Maybe the blocks could be grouped not by hash, but rather by block they
 might possible jump to. Then for each block B one only needs to compare
 the blocks that can jump to B. When identical blocks are found, the
 corresponding may-jump-to-sets can simply be unioned.

 OTOH, this seems relatively obvious, so there must be a reason why it is
 not done this way.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10397#comment:2>
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