Radix-4 modified Booth encoding to reduce the number of partial products and then a sort of modified Wallace tree using 4:2 compressors (or some sort of 3:2 & 4:2 compressor combination based on technology node). There is another type of multiplier sometimes used for maximum performance: unlike Wallace trees where you go through steps of tree reduction, the "Three Dimensional Method" looks at each output bit and generates the fastest possible tree from the partial product matrix. The problem with this method (besides area) is that the wiring and layout of cells is highly irregular. However, now that we are in the age of automated tools, this type of design is more feasible. Paper here: https://www.ece.ucdavis.edu/~vojin/CLASSES/EEC280/Web-page/p...If you're interested, this paper from Synopsys has some neat information about datapath synthesis:
https://guest.iis.ee.ethz.ch/~zimmi/publications/datapath_sy...
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