[GHC] #10137: Rewrite switch code generation

[GHC]

#10137: Rewrite switch code generation
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        Reporter:  nomeata           |                   Owner:  nomeata
            Type:  task              |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.9
  (CodeGen)                          |                Keywords:
      Resolution:                    |            Architecture:
Operating System:  Unknown/Multiple  |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:  #9157, #8326,     |  Differential Revisions:
  #8317, #9159                       |
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Comment (by nomeata):

 Fist benchmarks results are in; binary sizes are reduced, runtime changes
 varies with a small tendency towards improvement:

 {{{
                           Size    Allocs   Runtime   Elapsed  TotalMem
             Min          -1.8%     -0.0%     -4.5%     -7.8%      0.0%
             Max          -0.7%      0.0%     +3.3%     +3.4%     +2.9%
  Geometric Mean          -1.4%     -0.0%     -0.2%     -0.6%     +0.1%
 }}}

 The code still has some magic constants where an optimum could probably be
 found somehow.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10137#comment:8>
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