|Spring 2002 Laboratory Notes: Computer Engineering II|
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IRET ; CF  IRETW ; o16 CF  IRETD ; o32 CF 
IRET returns from an interrupt (hardware or software) by means of popping IP (or EIP), CS, and the flags off the stack and then continuing execution from the new CS:IP.
IRETW pops IP, CS and the flags as 2 bytes each, taking 6 bytes off the stack in total. IRETD pops EIP as 4 bytes, pops a further 4 bytes of which the top two are discarded and the bottom two go into CS, and pops the flags as 4 bytes as well, taking 12 bytes off the stack.
IRET is a shorthand for either IRETW or IRETD, depending on the default BITS setting at the time.