I haven't done any work on 65C816. Just 6502 so far.
It should be possible to make a 'CPU module' for the decompiler which takes into account the features of the 65C816 (such as 16-bit registers).
It should be possible to make a 'CPU module' for the decompiler which takes into account the features of the 65C816 (such as 16-bit registers).