[GHC] #8275: Loopification breaks profiling

[GHC]

#8275: Loopification breaks profiling
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        Reporter:  jstolarek            |            Owner:  jstolarek
            Type:  bug                  |           Status:  new
        Priority:  highest              |        Milestone:
       Component:  Profiling            |          Version:  7.7
      Resolution:                       |         Keywords:
Operating System:  Unknown/Multiple     |     Architecture:
 Type of failure:  Building GHC failed  |  Unknown/Multiple
       Test Case:                       |       Difficulty:  Unknown
        Blocking:  8298                 |       Blocked By:
                                        |  Related Tickets:
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Comment (by jstolarek):

 Replying to [comment:12 ezyang]:
 > As for whether or not the LDV code needs to be done again, it depends on
 whether node (R1) changes when looping.
 Yes, R1 does change inside the loop.

 > the loop-back needs to insert a heap check for preemption purposes. And
 if a loop can be preempted, then the era can change, and yes, you need to
 run the LDV check after the preemption.
 I don't fully understand this. What is preemption? If upon entry to the
 loop I will do the LDV code and heap check, will this ensure correctnes of
 profiling and `-falways-yields`? Is this described on the wiki somewhere
 (preemption and LDV)?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8275#comment:13>
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