[GHC] #8275: Loopification breaks profiling

[GHC]

#8275: Loopification breaks profiling
----------------------------------------+----------------------------------
        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:
----------------------------------------+----------------------------------

Comment (by ezyang):

 {{{
 Program received signal SIGSEGV, Segmentation fault.
 0x000000000509dced in enterFunCCS (reg=0x64540d8, ccsfn=0x644496000) at
 rts/Profiling.c:367
 367         if (ccsfn->prevStack == CCS_MAIN) {
 (gdb) bt
 #0  0x000000000509dced in enterFunCCS (reg=0x64540d8, ccsfn=0x644496000)
 at rts/Profiling.c:367
 #1  0x000000000095ad66 in s47v_info ()
 #2  0x0000000000000000 in ?? ()
 }}}

 where `0x644496000` is nonsense memory. My guess is that the nodeReg isn't
 being restored properly upon the loop back. Some sample code which the
 loopification triggers on would be helpful for debugging; you will
 probably be able to figure it out by eyeballing the C--.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8275#comment:4>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler