[boost] Context support for power architecture and mach-o ABI

I am interested in developing *ppc*_macho_gas.S implementations for the Boost.Context library. Has anyone already done some work on this combination? Any suggestions are welcome. I have prior experience in assembly programming and some understanding of processor scheduling concepts, but I have not done any work in these areas for a long time. I expect my re-learning curve to be steep. Thanks, John