Abstract: Methods and apparatus are described for an execution unit. A method includes receiving an instruction and one or more operands, determining a plurality of program bits and one or more sets of pluralities of select input bits, based on the instruction and the one or more operands, determining a plurality of extra adder input bits, based on the instruction and the one or more operands, determining a plurality of multiplexer output bits, based on the plurality of program bits and the one or more sets of pluralities of select input bits, determining one or more carry-save adder tree outputs, based on the plurality of multiplexer output bits and the plurality of extra adder input bits, determining a carry-propagate adder sum output, based on the one or more carry-save adder tree output; and determining the result of the instruction on the one or more operands, based on the carry-propagate adder sum output.