So yeah the first bit includes: __asm__ __volatile__ ("incl %0" - In essence, increment "at->x" by one, discard the value currently in m, and replace it with the incremented value, and the cc just shows that the value is going to be clobbered/changed by the end of the function.
|Increment register 0|
The second line, as shown here:
|decrement register 0, set byte e to one, otherwise zero|
Inline assembly is a pain the in the butt to find specific answers for some time.