[GHC] #13182: Rethinking dataToTag#

[GHC]

#13182: Rethinking dataToTag#
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        Reporter:  dfeuer            |                Owner:
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 > Then dataToTag# could be inlined in CorePrep, just like runRW#.

 I think that is precisely equivalent to what happens now, so yes it'd be
 ok.

 But then `CorePrep` would need to be able to eliminate the freshly-
 introduced case if it was redundant:
 {{{
 case x of { DEFAULT -> dataToTag# x }
 }}}
 Now if we inline `dataToTag#` we'll get a second case that must be
 eliminated.  The simplifier does this already.

 To me the status quo looks simpler.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13182#comment:1>
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