[GHC] #10401: state hack-related regression

[GHC]

#10401: state hack-related regression
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        Reporter:  rwbarton          |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by rwbarton):

 But the ticket is mostly about the behavior of 7.10.1 with `-O2 -fno-
 state-hack`. Does that change things? (Probably should have been clearer
 about this.)

 In 7.8 we have `-fno-state-hack` as an escape hatch for when the state
 hack heuristic goes wrong. But we can't expect people to rebuild all their
 dependencies including `base` with `-fno-state-hack`, and disabling
 optimizations completely is not very satisfactory either.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10401#comment:2>
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