[GHC] #15300: Unboxed Sums Crash

[GHC]

#15300: Unboxed Sums Crash
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        Reporter:  andrewthad        |                Owner:  osa1
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.5
      Resolution:                    |             Keywords:  UnboxedSums
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):

 Good sleuthing!

 What about doing StgCse after unarising?  Then the difference would be
 obvious!

 We do CSE in STG even though we've done it already in Core, because we can
 sometimes common-up things that have the same representation in STG even
 though they have different types in Core.  So it's possible that as well
 as prevent bogus CSE in the case you describe, you might get extra CSE in
 some other case.  But I'm not close enough to StgCSE to think of an
 example.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15300#comment:17>
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