[GHC] #14684: combineIdenticalAlts is only partially implemented

[GHC]

#14684: combineIdenticalAlts is only partially implemented
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        Reporter:  mpickering        |                Owner:  sjakobi
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:  newcomer
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4542
       Wiki Page:                    |
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Comment (by simonpj):

 > I'm wondering though if we'd recreate alts that may have been excluded
 (by the programmer or optimization steps) based on information that isn't
 available in CSE.

 Good point.

 Let's not be over-elaborate.

 My suggestion:

 * Try doing it all in `CSE.combineAlts`, as you suggest in comment:9
 * Switch off `combineIdenticalAlts` altogether
 * Do not try the clever stuff suggested in comment:13 for the reasons you
 mention

 If we can get away with doing this only in CSE, that'd be an advantage, I
 think.  Less duplication of effort.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14684#comment:15>
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