xtensa backend

Can you give me some insights to implement the windowed calling convention in this xtensa backend : https://github.com/afonso360/llvm-xtensa/tree/xtensa/lib/Target/Xtensa ?

For now, only the simpler CALL0 calling convention is implemented.

In order to implement the windowed calling convention, every routines must start with the ENTRY instruction which increments the register window pointer.

Do I have to manually insert this instruction during the PrologEpilog phase, and how can I declare this instruction ?


Are these like SPARC register windows? Have you looked at what the SPARC backend does?