It has been done before



"PortAsm/86 for PowerPC is a source-code translator which converts 80x86
assembly-language code into efficient and maintainable PowerPC
assembly-language. It automatically deals with architectural differences
such as segmented addressing and alignment of memory accesses, and applies
aggressive optimizations to ensure good performance of translated code."

http://www.microapl.co.uk/Porting/PortAsm86.html

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