[GHC] #10034: Regression in mapM_ performance

[GHC]

#10034: Regression in mapM_ performance
-------------------------------------+-------------------------------------
        Reporter:  dfeuer            |                   Owner:  ekmett
            Type:  bug               |                  Status:  new
        Priority:  normal            |               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
-------------------------------------+-------------------------------------

Comment (by Austin Seipp <austin@…>):

 In [changeset:"7cf87fc6928f0252d9f61719e2344e6c69237079/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="7cf87fc6928f0252d9f61719e2344e6c69237079"
 Eta-expand argument to foldr in mapM_ for []

 Summary:
 This improves performance, at least sometimes--the previous
 implementation can be worse than the version in base 4.7. I
 have not had the time to run benchmarks and such, but `mapM`
 already does this.

 Also, inline `mapM_`, like `mapM`.

 Reviewers: hvr, nomeata, ekmett, austin

 Reviewed By: ekmett, austin

 Subscribers: thomie

 Projects: #ghc

 Differential Revision: https://phabricator.haskell.org/D632

 GHC Trac Issues: #10034
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10034#comment:4>
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