[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        |           Version:  7.10.1-rc2
  Libraries                          |  Operating System:  Unknown/Multiple
              Keywords:              |   Type of failure:  Runtime
          Architecture:              |  performance bug
  Unknown/Multiple                   |        Blocked By:
             Test Case:              |   Related Tickets:
              Blocking:              |
Differential Revisions:  Phab:D632   |
-------------------------------------+-------------------------------------
 The current `mapM_` is sometimes worse than the version in 7.8.3. This can
 be fixed easily by eta-expansion, matching `mapM`.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10034>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler