In this paper, we present a novel algorithm for latch placement, LatchPlanner which enables a placement engine to deliver high quality placement for datapath-oriented design. Datapath-oriented VLSI designs are in general hand-crafted by human at high cost, as understanding and capturing datapath structure is critical for the performance. The conventional placement algorithms by itself cannot exploit the underlying datapath due to lack of logic structure recognition and inaccurate/approximated wirelength estimation. LatchPlanner addresses such drawbacks by placing and fixing latches in the datapath context, a key element in datapath structure. By taking placed/fixed latches as constraints, a placer can find a more datapath-friendly placement effectively, which results in higher-quality hardware. LatchPlanner begins latch clustering/sizing/ordering to prepare the following steps, a) global latch placement based on linear programming to place latch clusters, and b) local latch placement based on network flow optimization to place latches within each cluster. Experimental results on eighteen industrial benchmarks show that LatchPlanner improves total wirelength by 32%, total negative slack by 25%, and area by 3% without CPU overhead over a commercial placement engine, and delivers near semi-custom-quality solutions.
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