[GHC] #14152: Float exit paths out of recursive functions

[GHC]

#14152: Float exit paths out of recursive functions
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        Reporter:  nomeata           |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.1
      Resolution:                    |             Keywords:  JoinPoints
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #14137 #10918     |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by nomeata):

 >  I do quite like this approach. I'm not ready to give it up yet!

 I like this game of bad-cop/good-cop with switching roles. Certainly a
 productive way of investigating an issue :-)

 * `preInlineUnconditionally`:  Well, `int_cxt` certainly is `True` –
 otherwise `int_cxt && canInlineInLam rhs` would be `False` and inlining
 would not happen. Are you saying that it should be made `False`?

 * `completeCall`: Let me try to make sure I understand the reasoning:
 Normally a join point will not have `occ_in_lam`, because if it would
 occur under a “normal” lambda, it wouldn’t be a tail-call. The exception
 are the lambdas on the RHS of a join points, as these are ignored when
 calculating `occ_in_lam`. But there is an exception to that: Inside a
 recursive join point we do set `occ_in_lam`.

   So the occurrence analyzer should detect this? I’ll try.

 >  NB: right at the end (in CorePrep perhaps) we may want to inline them
 after all, just to reduce clutter and jumps.

 Right, I keep that in the back of my mind, but first I need it to actually
 _not_ inline :-)

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14152#comment:10>
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