tokens: As shown in Table , a general propagation rule for any operation ( O ) should be able to decide that what the tag on the program counter in the next machine state ( ) and the tag on the instruction ’s result ( R ) should be if the current tag on the program counter is PC , the tag on the current instruction is CI , the tags on its input operands ( if any ) are OP1 and OP2 , and the tag on the memory location ( in case of load / store ) is MR .