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Dec 8, 2013
Description. Subtracts operand1 from operand2, but does not store the result; only changes the flags. cmp is typically executed in conjunction with conditional jumps and the set cc instruction. If an operand greater than one byte is compared to an immediate byte, the immediate byte value is first sign-extended.
Jul 11, 2007 At the end of the article I will explain how this is done, but I'll move onto the more important matters for now since that knowledge is not really needed for cracking or coding. Sign and Zero Flag: The four flags that the CMP instruction can set - Z,O,C, and S, are known as the zero, overflow, carry, and
The main difference between cmp and sub is that cmp does not store the result of the subtract operation; it performs subtraction only to set the status flags. Here are some examples: cmp char , '$' ; ZF = 1 if char is '$ ' Similarly, two registers
Difference is then discarded. If subtrahend is an immediate value it will be sign extended to the length of minuend . The EFLAGS register is set in the same manner as a sub instruction. Note that the GAS/AT&T syntax can be rather confusing, as for example cmp $0, %rax followed by jl branch will branch if %rax < 0 (and not
The cmp (compare) instruction is identical to the sub (subtract without borrow) instruction with one important difference - it does not store the difference back into the destination operand. The syntax of a subtract instruction is: sub dest, src dest = dest - src and set flags. The generic form of the instruction is:
JNZ is short for "Jump if not zero (ZF = 0)", and NOT "Jump if the ZF is set". If it's any easier to remember, consider that JNZ and JNE (jump if not equal) are equivalent. Therefore, when you're doing cmp al, 47 and the content of AL is equal to 47, the ZF is set, ergo the jump (if Not Equal - JNE) should not be
CMP Instruction. The CMP instruction compares two operands. It is generally used in conditional execution.
Operation These instructions compare the value in a register with Operand2. They update the condition flags on the result, but do not place the result in any register. The CMP instruction subtracts the value of Operand2 from the value in Rn. This is the same as a SUBS instruction, except that the result is discarded. The CMN
See Extended Mnemonics of Fixed-Point Compare Instructions for more information. Description. The cmp instruction compares the contents of general-purpose register (GPR) RA with the contents of GPR RB as signed integers and sets one of the bits in Condition Register Field BF. BF can be Condition Register Field 0-7;
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