[GHC] #13027: The let/app invariant, evaluated-ness, and reallyUnsafePtrEquality#

[GHC]

#13027: The let/app invariant, evaluated-ness, and reallyUnsafePtrEquality#
-------------------------------------+-------------------------------------
        Reporter:  erikd             |                Owner:  dfeuer
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Building GHC      |            Test Case:
  failed                             |  simplCore/should_compile/T13027
      Blocked By:                    |             Blocking:
 Related Tickets:  #11444            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by David Feuer <David.Feuer@…>):

 In [changeset:"b3576ed22570364f917c620a3cd29709355e4d51/ghc" b3576ed/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="b3576ed22570364f917c620a3cd29709355e4d51"
 Mark reallyUnsafePtrEquality# as can_fail

 As described in the note, floating `reallyUnsafePtrEquality#`
 out can make it much less precise. Marking it `can_fail` will
 prevent it from floating out, which I believe is particularly
 important in light of 5a9a1738023aeb742e537fb4a59c4aa8fecc1f8a,
 and should also help prevent let/app invariant failures as seen
 in #11444 and #13027.

 Reviewers: simonpj, austin, bgamari

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D2987

 GHC Trac Issues: #13027, #11444
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13027#comment:37>
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