instruction FIFO
The front-end and the back-end are connected by Instruction FIFO. The instruction decoded from the front-end will be pushed into the instruction FIFO. The Dispatch stage will get instruction information from the instruction FIFO.
There is a Schmitt Trigger which controls the FIFO reject signal. When the space of FIFO in use reaches 3/4, it will stall the front-end. When the space of FIFO in use reaches 1/4, it will release the front-end.
