[GHC] #10137: Rewrite switch code generation

[GHC]

#10137: Rewrite switch code generation
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        Reporter:  nomeata           |                   Owner:
            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:                    |  Differential Revisions:
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Comment (by simonpj):

 Sounds good.  I do think that some work can be done in Core.  For example:
 {{{
 case x of
   1# -> e1
   2# -> e2
   7# -> e1
   _  -> e2
 }}}
 might turn into
 {{{
 case (x ==# 1# `orI#` x ==# 7#) of
   0# -> e2   -- False
   1# -> e1   -- True
 }}}
 I would also '''dearly''' like to implement #8317 to get rid of all those
 stupid `tagToEnum#` calls that clutter up the code.  We don't do this for
 a stupid reason: #8326.  As part of your crusade, dealing with this would
 be fantastic.

 I'd be happy to advise/help.

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10137#comment:1>
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