How can I create an if statement using logic gates?

I am currently working on a basic binary multiplier and we are limited to using logic gates (AND/OR/NAND/NOR/XOR). I am trying to make the statement listing below but cannot figure out how this would be made without an if.

(x represents the multiplicand and y the multiplier)

if ((y & 1) != 0) product = add(product,x);