Hallo! I got a bit further with my problem. Now I'm stuck on how to save the register used when -fPIC is enabled to the stack before my seven input operands, needing all registers, get loaded. Is that somehow possible? I couldn't find any examples on the net. It seems not to be necessary in the original code for MSC. Also I wonder which -f option that comes with -O2 makes gcc stop reporting: error: can't find a register in class 'LEGACY_REGS' while reloading 'asm' Thanks. Lynx