Implement DWARF debugging on powerpc64

debug:

ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 7.11.20151219 for powerpc64-unknown-linux):
        dwarfReturnRegNo: Unsupported platform!
CallStack (from ImplicitParams):
  error, called at compiler/nativeGen/Dwarf/Constants.hs:224:19 in ghc:Dwarf.Constants

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

Provide DWARF constants for registers.

Still TODO:

• add unwinding information to StgCRun to ensure that the unwinder can unwind from Haskell into C
• to support the RTS unwinder: add support to the initial register callback set_initial_registers in rts/Libdw.c
• Valid unwind records in stg_stop_thread (defined in rts/StgStartup.cmm)
• Support in the native code generator (by implementing the extractUnwindPoints field of NcgImpl)
• Unwinding support in libdw

Trac metadata

Trac field	Value
Version	7.11
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (CodeGen)
Test case	debug, T10667
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture