[GHC] #15179: Unwinding info for stg_ap_v_info is wrong

[GHC]

#15179: Unwinding info for stg_ap_v_info is wrong
-------------------------------------+-------------------------------------
           Reporter:  niteria        |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.5
  (Debugging)                        |
           Keywords:                 |  Operating System:  Linux
       Architecture:                 |   Type of failure:  Debugging
  Unknown/Multiple                   |  information is incorrect
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 The `readelf --debug-dump=frames-interp` output for `stg_ap_v_info` is:

 {{{
 00000018 0000000000000034 00000000 FDE cie=00000000
 pc=000000000000000f..000000000000021d
    LOC           CFA      rbp   rsp   ra
 000000000000000f rbp+0    v+0   u     c+0
 0000000000000037 rbp+0    v+0   vexp  c+0
 0000000000000047 rbp+0    v+0   s     c+0
 }}}

 It's wrong because it unwinds to the same frame, see `cfa = rbp + 0`.

 I know the reason, I will put it in the comments below.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15179>
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