The x86 Compare instruction (CMP) subtracts the source operand from the destination operand; it updates the status flags (C, P, A, Z, S, O) but does not alter either of the operands. The CMP instruction can be used to determine if the destination operand is greater than, equal to, or less than the source operand.
a. Suppose the two operands are treated as unsigned integers. Show which status flags are relevant to determine the relative size of the two integer and what values of the flags correspond to greater than, equal to, or less than.
b. Suppose the two operands are treated as twos complement signed integers. Show which status flags are relevant to determine the relative size of the two integer and what values of the flags correspond to greater than, equal to, or less than.
c. The CMP instruction may be followed by a conditional Jump (Jcc) or Set Condition (SETcc) instruction, where cc refers to one of the 16 conditions listed in Table 10.10. Demonstrate that the conditions tested for a signed number comparison are correct.