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In this project studied the theory and
algorithm for SPFD-based global rewiring (SPFD-GR). SPFD-GR allows us to
globally replace a target wire with some alternative wire possibly far away from
the target, thereby successfully overcoming the limitations of the existing SPFD-based
local rewiring algorithm (SPFD-LR), which can only replace a wire with another
wire that has the same destination node. In order to perform SPFD-based global
rewiring, we developed the theory and algorithm for solving a fundamental
problem in SPFD-based rewiring: Given the in-pin functions of a node and the SPFD at the
node’s out-pin, is there a way to modify the node’s internal function so
that the SPFD at the node’s out-pin can be satisfied? Combined with a
state-of-art partitioning algorithm, SPFD-GR scales well to large circuits with
good synthesis quality.
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Extensive experimental results show that
for LUT-based FPGAs, the rewiring ability of SPFD-GR (in terms of the number of
wires that have alternative wires) is 1.45, and 3 times that of SPFD-LR and an
ATPG-based rewiring algorithm (with a preliminary experimental flow),
respectively, while the run time is quite acceptable. When applied to the
post-mapping area reduction for large LUT-based FPGAs under circuit depth
restriction, SPFD-GR achieves 17.1% average area reduction, with no delay
increase.
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