x86 Instruction Set Reference

Computes the effective address of the second operand (the source operand) and stores it in the first operand (destination operand). The source operand is a memory address (offset part) specified with one of the processors addressing modes; the destination operand is a general-purpose register. The address-size and operand-size attributes affect the action performed by this instruction, as shown in the following table. The operand-size attribute of the instruction is determined by the chosen register; the address-size attribute is determined by the attribute of the code segment.

Different assemblers may use different algorithms based on the size attribute and symbolic reference of the source operand.

if(OperandSize == 16 && AddressSize == 16) Destination = EffectiveAddress(Source); //16-bit address
else if(OperandSize == 16 && AddressSize == 32) {
	Temporary = EffectiveAddress(Source); //32-bit address
	Destination = Temporary[0..15]; //16-bit address
}
else if(OperandSize == 32 && AddressSize == 16) {
	Temporary = EffectiveAddress(Source); //16-bit address;
	Destination = ZeroExtend(Temporary); //32-bit address
}
else if(OperandSize == 32 && AddressSize == 32) Destination = EffectiveAddress(Source) //32-bit address

None.