Flow Control Instructions

These instructions may alter the flow of the program.

Table B-4: Flow Control Instructions

Instruction	Operands	Affected Flags
call	destination address	O/S/Z/A/C
This pushes what would be the next value for %eip onto the stack, and jumps to the destination address. Used for function calls. Alternatively, the destination address can be an asterisk followed by a register for an indirect function call. For example, call *%eax will call the function at the address in %eax.
int	I	O/S/Z/A/C
Causes an interrupt of the given number. This is usually used for system calls and other kernel interfaces.
Jcc	destination address	O/S/Z/A/C
Conditional branch. cc is the condition code. Jumps to the given address if the condition code is true (set from the previous instruction, probably a comparison). Otherwise, goes to the next instruction. The condition codes are: [n] a [e] - above (unsigned greater than). An n can be added for "not" and an e can be added for "or equal to" [n] b [e] - below (unsigned less than) [n] e - equal to [n]z - zero [n] g [e] - greater than (signed comparison) [n] l [e] - less than (signed comparison) [n] c - carry flag set [n] o - overflow flag set [p] p - parity flag set [n] s - sign flag set ecxz - %ecx is zero
jmp	destination address	O/S/Z/A/C
An unconditional jump. This simply sets %eip to the destination address. Alternatively, the destination address can be an asterisk followed by a register for an indirect jump. For example, jmp *%eax will jump to the address in %eax.
ret		O/S/Z/A/C
Pops a value off of the stack and then sets %eip to that value. Used to return from function calls.