[GHC] #2915: Arity is smaller than need be

[GHC]

#2915: Arity is smaller than need be
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        Reporter:  simonpj                  |            Owner:  simonpj
            Type:  bug                      |           Status:  closed
        Priority:  lowest                   |        Milestone:  7.6.2
       Component:  Compiler                 |          Version:  6.10.1
      Resolution:  fixed                    |         Keywords:
Operating System:  Unknown/Multiple         |     Architecture:
 Type of failure:  Runtime performance bug  |  Unknown/Multiple
       Test Case:                           |       Difficulty:  Unknown
        Blocking:                           |       Blocked By:
                                            |  Related Tickets:
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Changes (by nomeata):

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


Comment:

 It seems that not test cases fail with this change, and only one nofib
 benchmark profits (mandel -1.9%). It would also simplify `CoreArity` (no
 need for the `ae_bndrs` field).

 (Or course the scrunitee must not be expensive; I guard this using the
 `ae_cheap_fn`. If I don't do that, fluid improves allocation by -2.3%, but
 of course it's wrong. In most cases, though, FloatOut will have ensured
 that the scrutinee is cheap)

 I’ll need to run another round of nofib, with an unloaded machine, to
 ensure that the runtimes are still ok... and here it is

 {{{
             Min          -0.1%     -1.9%     -3.0%     -2.9%      0.0%
             Max          +0.0%     +0.0%     +3.5%     +2.2%     +3.8%
  Geometric Mean          -0.0%     -0.0%     -0.4%     -0.4%     +0.0%
 }}}

 Runtime varies a bit, with a slight tendency to an improvement. Guess that
 is good enough to push.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2915#comment:13>
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