[GHC] #11162: T783 regresses severely in allocations with new pattern match checker

[GHC]

#11162: T783 regresses severely in allocations with new pattern match checker
-------------------------------------+-------------------------------------
           Reporter:  bgamari        |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  7.10.2
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Compile-time
  Unknown/Multiple                   |  performance bug
          Test Case:  T783           |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 The new pattern match checker (Phab:D1535) allocates 115% more than the
 previous checker on the T783 testcase,
 {{{
 bytes allocated value is too high:
     Expected    T783(normal) bytes allocated:  526230456 +/-10%
     Lower bound T783(normal) bytes allocated:  473607410
     Upper bound T783(normal) bytes allocated:  578853502
     Actual      T783(normal) bytes allocated: 1134085384
     Deviation   T783(normal) bytes allocated:      115.5 %
 *** unexpected stat test failure for T783(normal)
 }}}

 I suspect this isn't avoidable as this testcase consists of nothing more
 than 500 guarded equations, so exercises the checker quite thoroughly.
 That being said, perhaps it's worth a closer look.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11162>
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