[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:  fixed             |                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
                                     |  Phab:D896
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Comment (by TobyGoodwin):

 Fantastic work on this. Can I just point out that it ''is'' real-world
 code? It's the yesod backend for [https://www.mythic-
 beasts.com/auth/register this web page] and I stumbled across this problem
 simply by trying to upgrade from 7.6 to 7.8.

 Which brings me to another point: it's great that this will be in 7.10. Is
 there any chance of getting it into 7.8 too? Most of the distros (Debian,
 Ubuntu LTS, even Fedora) have not made the jump to 7.8 yet, and when they
 do I'd hate for anyone else to have the same experience that I did, of a
 massive slowdown in compile times.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10397#comment:31>
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