[GHC] #14295: tagToEnum# leads to some silly closures

[GHC]

#14295: tagToEnum# leads to some silly closures
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.2.1
      Resolution:                    |             Keywords:  datacon-tags
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by dfeuer):

 Replying to [comment:11 simonpj]:

 >   So yes one could do it as a `CorePrep` tactic, but it's delicate; and
 we risk not getting the benefits because we don't implement the follow-on
 transformations.

 What makes it delicate? For `quotInt#` et al, I don't imagine that there
 ''are'' many interesting follow-on transformations in most cases, although
 I could be wrong. For `tagToEnum#`, we should decide whether to "inline"
 in core2core. If we go to the trouble of a `quotInt#` cleanup in
 `CorePrep`, then we can just tack the `tagToEnum#` cleanup on in the same
 way.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14295#comment:12>
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