[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:  patch
        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):  Phab:D3437
       Wiki Page:                    |
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Comment (by Joachim Breitner <mail@…>):

 In [changeset:"b55f310d06b8d3988d40aaccc0ff13601ee52b84/ghc"
 b55f310d/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="b55f310d06b8d3988d40aaccc0ff13601ee52b84"
 StgCse: Do not re-use trivial case scrutinees

 as they might be marked as one-shot, and suddenly we’d evaluate them
 multiple times. This came up in #13536 (test cases included).

 The solution was layed out by SPJ in ticket:13536#comment:12.

 Differential Revision: https://phabricator.haskell.org/D3437
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13536#comment:19>
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