[GHC] #10457: Revise/remove custom mapM implementation for lists

[GHC]

#10457: Revise/remove custom mapM implementation for lists
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        Reporter:  dolio             |                   Owner:
            Type:  task              |                  Status:  new
        Priority:  normal            |               Milestone:  7.12.1
       Component:  libraries/base    |                 Version:  7.10.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:  Phab:D1124
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Changes (by simonpj):

 * status:  closed => new
 * resolution:  fixed =>


Comment:

 The
 [https://perf.haskell.org/ghc/#revision/60297486fddd5c9695e2263c2ae46fa90f0feb9e
 perf tester says], about nofib allocations:
 {{{
 nofib/allocs/cryptarithm2   + 64.55%
 nofib/allocs/k-nucleotide    - 5.03%
 nofib/time/fannkuch-redux    - 3.62%
 }}}
 This needs looking into!

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10457#comment:16>
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