[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):

 Digging deeper: For `CSD`, `-ticky`, even with all of base instrumted,
 does not not show anything. Same for `cryptarithm1`.

 Judging from the module sizes, in base only `Data.Semigroup`, `GHC.Arr`
 and `GHC.Float` are affected (but maybe floating a let binding can happen
 with equally sized output binary.). A quick look at the core difference
 shows that some thunks are floated inside a `joinrec`, or even inlined
 completely, e.g. in `Arr`’s `(//)` and `accum`.

 None of these look as if they’d affect a benchmark like `CSD`.

 It must be the weather, or the constellation of the stars.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14152#comment:23>
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