[GHC] #10034: Regression in mapM_ performance

[GHC]

#10034: Regression in mapM_ performance
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        Reporter:  dfeuer            |                   Owner:  ekmett
            Type:  bug               |                  Status:  new
        Priority:  highest           |               Milestone:  7.10.1
       Component:  Core Libraries    |                 Version:  7.10.1-rc2
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:  Phab:D632
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Comment (by Austin Seipp <austin@…>):

 In [changeset:"91d9530525803403c3c012901115d54ff4fc3b5e/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="91d9530525803403c3c012901115d54ff4fc3b5e"
 Revert "Eta-expand argument to foldr in mapM_ for []"

 This change lacked justification (or a test!) for its improvements, and
 I merged it on a sweep of Phabricator without fixing this. Trac #10034.

 This reverts commit 7cf87fc6928f0252d9f61719e2344e6c69237079.
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10034#comment:6>
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