Computing system and computer-implemented method for designing integrated circuit

A computer-implemented method includes placing standard cells based on design data defining an integrated circuit. A layout of the integrated circuit is generated by performing colorless routing. First, second, third and fourth patterns included in a quadruple patterning lithography (QPL) layer are arranged, based on space constraints, on the placed standard cells. The generated layout is stored to a computer-readable storage medium. The space constraints define minimum spaces between the first, second, third and fourth patterns. The method includes assigning first, second, third and fourth colors to the first, second, third and fourth patterns, respectively. Masks are generated based on the layout. A semiconductor device is manufactured by using the generated masks.