[GHC] #13861: Take more advantage of STG representation invariance (follows up #9291)

[GHC]

#13861: Take more advantage of STG representation invariance (follows up #9291)
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        Reporter:  heisenbug         |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.2
      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 heisenbug):

 Replying to [comment:7 bgamari]:
 > It would be nice to know what the motivation for *not* using the
 available tag space for big families is. Surely there was a reason, even
 if it was just keeping implementation complexity at bay.

 Probably the motivation was "we'll think about this later". Implementation
 complexity seems to be fairly low, see my branch (caveat: ''very WIP'')
 https://github.com/ggreif/ghc/tree/wip/tag-big-families

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13861#comment:9>
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