[GHC] #13900: Core lint in BuildFlavour=perf-llvm

[GHC]

#13900: Core lint in BuildFlavour=perf-llvm
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        Reporter:  bgamari           |                Owner:  bgamari
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by dfeuer):

 As best I can tell, everything is fine for long, long time. After
 SpecConstr, the simplifier runs iteration 1 successfully, but then the
 next round blows up. It looks like the problematic binding is converted to
 a join point here, if I'm reading it right. Around when that happens, its
 type signature changes. The specialization rule for it, however, still
 rewrites it to something with its original type, causing the lint error.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13900#comment:12>
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