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

[GHC]

#13027: The let/app invariant, evaluated-ness, and reallyUnsafePtrEquality#
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        Reporter:  erikd             |                Owner:
            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 Simon Peyton Jones <simonpj@…>):

 In [changeset:"5a9a1738023aeb742e537fb4a59c4aa8fecc1f8a/ghc" 5a9a173/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="5a9a1738023aeb742e537fb4a59c4aa8fecc1f8a"
 Refine exprOkForSpeculation

 This patch implements two related changes, both inspired by
 the discussion on Trac #13027, comment:23:

 * exprOkForSpeculation (op# a1 .. an), where op# is a primop,
   now skips over arguments ai of lifted type.  See the comments
   at Note [Primops with lifted arguments] in CoreUtils.

   There is no need to treat dataToTag# specially any more.

 * dataToTag# is now treated as a can-fail primop.  See
   Note [dataToTag#] in primops.txt.pp

 I don't expect this to have a visible effect on anything, but
 it's much more solid than before.
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13027#comment:29>
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