I would rather pass the register to the macro? If you start toThe intent is that these code sequences can be patched in place, so they need to have a specific abi at the machine-code level. Some of the operations whose Xen implementation clobbers a register have that in their definition, on the assumption that 1 temp is enough, and that another interface which needs more can organize save/restoring registers for itself.
clobber registers you would need to pass in the tmp registers
too I guess.