[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:  merge
        Priority:  normal            |               Milestone:  7.10.2
       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:  Phab:D892
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Comment (by simonpj):

 That's a trememdous improvement, thanks Joachim.

 That said, 20% of compilation time in one, relatively minor, optimisation
 is far too much.  I wonder how we could improve matters further?  For
 example, the bigger the block the less likely it is to be identical, but
 the more expensive it is to compare (I guess).  Maybe we can cut off at
 some block size?

 Also why are you comparing (hash, list of successor labels) rather than
 just including the successor labels in the hash?

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10397#comment:22>
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