Integer Instructions

These are basic calculating instructions that operate on signed or unsigned integers.

Table B-2: Integer Instructions

Instruction	Operands	Affected Flags
adcl	I/R/M, R/M	O/S/Z/A/P/C
Add with carry. Adds the carry bit and the first operand to the second, and, if there is an overflow, sets overflow and carry to true. This is usually used for operations larger than a machine word. The addition on the least-significant word would take place using addl, while additions to the other words would used the adcl instruction to take the carry from the previous add into account. For the usual case, this is not used, and addl is used instead.
addl	I/R/M, R/M	O/S/Z/A/P/C
Addition. Adds the first operand to the second, storing the result in the second. If the result is larger than the destination register, the overflow and carry bits are set to true. This instruction operates on both signed and unsigned integers.
cdq		O/S/Z/A/P/C
Converts the %eax word into the double-word consisting of %edx:%eax with sign extension. The q signifies that it is a quad-word. It's actually a double-word, but it's called a quad-word because of the terminology used in the 16-bit days. This is usually used before issuing an idivl instruction.
cmpl	I/R/M, R/M	O/S/Z/A/P/C
Compares two integers. It does this by subtracting the first operand from the second. It discards the results, but sets the flags accordingly. Usually used before a conditional jump.
decl	R/M	O/S/Z/A/P
Decrements the register or memory location. Use decb to decrement a byte instead of a word.
divl	R/M	O/S/Z/A/P
Performs unsigned division. Divides the contents of the double-word contained in the combined %edx:%eax registers by the value in the register or memory location specified. The %eax register contains the resulting quotient, and the %edx register contains the resulting remainder. If the quotient is too large to fit in %eax, it triggers a type 0 interrupt.
idivl	R/M	O/S/Z/A/P
Performs signed division. Operates just like divl above.
imull	R/M/I, R	O/S/Z/A/P/C
Performs signed multiplication and stores the result in the second operand. If the second operand is left out, it is assumed to be %eax, and the full result is stored in the double-word %edx:%eax.
incl	R/M	O/S/Z/A/P
Increments the given register or memory location. Use incb to increment a byte instead of a word.
mull	R/M/I, R	O/S/Z/A/P/C
Perform unsigned multiplication. Same rules as apply to imull.
negl	R/M	O/S/Z/A/P/C
Negates (gives the two's complement inversion of) the given register or memory location.
sbbl	I/R/M, R/M	O/S/Z/A/P/C
Subtract with borrowing. This is used in the same way that adc is, except for subtraction. Normally only subl is used.
subl	I/R/M, R/M	O/S/Z/A/P/C
Subtract the two operands. This subtracts the first operand from the second, and stores the result in the second operand. This instruction can be used on both signed and unsigned numbers.