Efficient Signed Multiplier with good timing

I am making a signed multiplier for that i have created half adder, full adder, ripple carry adder and then finally a multiplier. The code is shown below. How can i make it faster to achieve better timing. My final task is to make a fir filter operating running at 100Mhz. This filter use multiple multiplication operation(by using my multiplier). So Can you help me to make my design better by some optimizing technique like pipelining or parallelism or other??

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