[GHC] #14880: GHC panic: updateRole

[GHC]

#14880: GHC panic: updateRole
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        Reporter:  RyanGlScott       |                Owner:  goldfire
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.2.2
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #15076            |  Differential Rev(s):  Phab:D4769
       Wiki Page:                    |
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Comment (by tdammers):

 Hah, that's a good hint! I did another run, this time compiling with
 `-fprof-auto-top` on `TyCoRep` only, and this reveals two interesting
 things:

 - `tcvs_of_type`, which doesn't exist in the old version yet, is
 responsible for 4.5% of CPU time in the new version
 - `zonkTopDecls`, while allocating about 8.8% in both versions, jumps from
 5.9% CPU to 8.2%

 I'll dig deeper on these two.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14880#comment:42>
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