Logic Instructions

These instructions operate on memory as bits instead of words.

Table B-3: Logic Instructions

Instruction	Operands	Affected Flags
andl	I/R/M, R/M	O/S/Z/P/C
Performs a logical and of the contents of the two operands, and stores the result in the second operand. Sets the overflow and carry flags to false.
notl	R/M
Performs a logical not on each bit in the operand. Also known as a one's complement.
orl	I/R/M, R/M	O/S/Z/A/P/C
Performs a logical or between the two operands, and stores the result in the second operand. Sets the overflow and carry flags to false.
rcll	I/%c1, R/M	O/C
Rotates the given location's bits to the left the number of times in the first operand, which is either an immediate-mode value or the register %cl. The carry flag is included in the rotation, making it use 33 bits instead of 32. Also sets the overflow flag.
rcrl	I/%cl, R/M	O/C
Same as above, but rotates right.
roll	I/%cl, R/M	O/C
Rotate bits to the left. It sets the overflow and carry flags, but does not count the carry flag as part of the rotation. The number of bits to roll is either specified in immediate mode or is contained in the %cl register.
rorl	I/%cl, R/M	O/C
Same as above, but rotates right.
sall	I/%cl, R/M	C
Arithmetic shift left. The sign bit is shifted out to the carry flag, and a zero bit is placed in the least significant bit. Other bits are simply shifted to the left. This is the same as the regular shift left. The number of bits to shift is either specified in immediate mode or is contained in the %cl register.
sarl	I/%cl, R/M	C
Arithmetic shift right. The least significant bit is shifted out to the carry flag. The sign bit is shifted in, and kept as the sign bit. Other bits are simply shifted to the right. The number of bits to shift is either specified in immediate mode or is contained in the %cl register.
shll	I/%cl, R/M	C
Logical shift left. This shifts all bits to the left (sign bit is not treated specially). The leftmost bit is pushed to the carry flag. The number of bits to shift is either specified in immediate mode or is contained in the %cl register.
shrl	I/%cl, R/M	C
Logical shift right. This shifts all bits in the register to the right (sign bit is not treated specially). The rightmost bit is pushed to the carry flag. The number of bits o shift is either specified in immediate mode or is contained in the %cl register.
testl	I/R/M, R/M	O/S/Z/A/P/C
Does a logical and of both operands and discards the results, but sets the flags accordingly.
xorl	I/R/M, R/M	O/S/Z/A/P/C
Does an exclusive or on the two operands, and stores the result in the second operand. Sets the overflow and carry flags to false.