[GHC] #13236: Improve floating for join points

[GHC]

#13236: Improve floating for join points
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        Reporter:  simonpj           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  JoinPoints
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by David Feuer <David.Feuer@…>):

 In [changeset:"6eb52cfc2e31df2561860f43d41766464ccfe8af/ghc"
 6eb52cfc/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="6eb52cfc2e31df2561860f43d41766464ccfe8af"
 Improve SetLevels for join points

 C.f. Trac #13286, #13236

 * Never destroy a join point unless it goes to top level
   See Note [Floating join point bindings]

 * Never float a MFE if it has a free join variable
   Note [Free join points]

 * Stop treating nullary join points specially

 * Enforce the invariant that le_join_ceil >= le_ctxt_lvl
   (Needs more thought...)

 Reviewers: austin, bgamari

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D3199
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13236#comment:6>
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