[GHC] #11528: Representation of value set abstractions as trees causes performance issues

[GHC]

#11528: Representation of value set abstractions as trees causes performance issues
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           Reporter:  gkaracha       |             Owner:  gkaracha
               Type:  task           |            Status:  new
           Priority:  lowest         |         Milestone:  Research needed
          Component:  Compiler       |           Version:
           Keywords:                 |  Operating System:  Unknown/Multiple
  PatternMatchWarnings               |
       Architecture:                 |   Type of failure:  Compile-time
  Unknown/Multiple                   |  performance bug
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 The new exhaustiveness checker has been originally designed to use a
 prefix tree representation of value set abstractions. Unfortunately, this
 resulted in huge performance problems (see for example #11160, #11161,
 #11162, #11163, #11195, #11276, #11303, #11374, #11302) and we had to
 switch to a representation of value set abstractions as a list of value
 vector abstractions.

 It would be nice to switch back to the prefix tree representation but the
 performance problems with it are yet to be characterized so I have created
 a branch using this representation (`wip/gadtpm-prefix-tree`) to further
 investigate this approach.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11528>
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