U.S. stocks were set to open sharply lower Tuesday as a tech sell-off that began during the prior session picked up steam overnight, with global markets in Asia routed as memory chip-related shares tumbled. Nasdaq futures were pointing to a nearly 3% decline on Tuesday. Nasdaq 100 futures slid 3.1%. S&P 500 futures were 1.4% lower, while futures tied to the Dow Jones Industrial Average were down 215 points, or 0.4%.