wreduce - reduce the word size of operations if possible

yosys> help wreduce
wreduce [options] [selection]
This command reduces the word size of operations. For example it will replace
the 32 bit adders in the following code with adders of more appropriate widths:

    module test(input [3:0] a, b, c, output [7:0] y);
        assign y = a + b + c + 1;

Do not change the width of memory address ports. Use this options in
flows that use the 'memory_memx' pass.
remove 'undef' inputs from $mux, $pmux and $_MUX_ cells
Do not optimize explicit don't-care values.