[GHC] #8199: Get rid of HEAP_ALLOCED

[GHC]

#8199: Get rid of HEAP_ALLOCED
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        Reporter:  ezyang   |            Owner:  ezyang
            Type:  feature  |           Status:  new
  request                   |        Milestone:  7.10.1
        Priority:  normal   |          Version:  7.7
       Component:           |         Keywords:
  Compiler                  |     Architecture:  Unknown/Multiple
      Resolution:           |       Difficulty:  Project (more than a week)
Operating System:           |       Blocked By:  5435
  Unknown/Multiple          |  Related Tickets:
 Type of failure:           |
  None/Unknown              |
       Test Case:           |
        Blocking:           |
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Comment (by simonmar):

 FYI, I think you uploaded the wrong patch for the latest patch (version
 4).

 Points 1 and 2 are unavoidable.

 Point 3 is interesting - I think we could probably do better there, but we
 should look at the context a bit more.  In many cases where we have a
 tagged pointer, we take the tag into account when operating on it (e.g.
 field index), but here it looks like we're just unconditionally zeroing
 the tag bits.

 Point 4 might be improved by overlapping the indirection word with the
 closure itself.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8199#comment:19>
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