[GHC] #13536: Program which terminates instantly in GHC 8.0.2 runs for minutes with 8.2.1

[GHC]

#13536: Program which terminates instantly in GHC 8.0.2 runs for minutes with 8.2.1
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 Yes.  It's really
 {{{
       case e of w { p1 -> w; ...; pn -> w }
 ===>
       e
 }}}
 (Core has a more general version involving strictness on `x`.)

 I don't know how much it happens in practice.  It would not be hard to
 include this in `StgCse` though.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13536#comment:16>
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