[GHC] #15002: Panic: collectNBinders

[GHC]

#15002: Panic: collectNBinders
-------------------------------------+-------------------------------------
        Reporter:  crockeea          |                Owner:  nomeata
            Type:  bug               |               Status:  patch
        Priority:  highest           |            Milestone:  8.4.2
       Component:  Profiling         |              Version:  8.4.1
      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):  Phab:D4572
       Wiki Page:                    |
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Comment (by nomeata):

 Ah, things are never easy. Yes, adding `noCSE` in the right places is the
 right thing to do, and it fixes this bug. But as often when fixing a “bug”
 in an optimization, it makes it less aggressive, and we get regressions:

 {{{
 Nofib allocations
 nofib/allocs/rewrite    16255960        + 5.52%         17153208
 bytes
 nofib/allocs/scs        902408848       + 5.22%         949533296
 bytes

 Nofib instruction counts
 nofib/instr/rewrite     55292296        + 4.73%         57910048

 Testsuite allocations
 tests/alloc/T8766       16828080        + 348.94%       75548336
 bytes
 }}}

 Did not investigate anything yet (it’s 1am here).

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15002#comment:13>
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