CFA with no frame pointer

Hi,

I'm working on the port of LLDB for PowerPC, and running into a small
snag. The CFA-based unwind code seems to require a frame pointer. The
frame address on PowerPC is stored in *r1, and a frame pointer is
completely optional. What would be the best way to unwind, in an ABI
plugin, without a frame pointer? I've thought about creating a fake
register, and implementing it in the elf-core handler, but not sure if
that's the best way to go.

Thanks,
Justin