Check out the companies making the biggest moves before the bell: Confluent – The Wall Street Journal published a report on Sunday that IBM is in advanced talks to seal an $11 billion deal to acquire data-infrastructure company Confluent, boosting the latter company’s shares by 27%. Broadcom — The chipmaker rose more than 2% after The Information reported it was in talks of moving its custom chips business to Broadcom from Marvell Technology . Shares of Marvell shed 6%. Lumentum Holdings — The optical and photonic product manufacturer’s stock added 4% after it announced an extension of its strategic agreement with IQE, a British semiconductor company. Carvana , CRH — Ireland-based manufacturer CRH and automobile e-commerce platform Carvana will join the S & P 500, S & P Dow Jones Indices announced Friday. The changes will be reflected prior to the open of Dec. 22. CRH gained 7%, while Carvana rose nearly 9%. Berkshire Hathaway — Warren Buffett’s conglomerate announced the departure of Todd Combs, investment officer and Geico CEO, who will be joining JPMorgan Chase as head of the bank’s new Security and Resiliency Initiative to find direct equity investments. Berkshire also announced a few other structural changes before the legendary CEO steps aside at the end of this year. The stock inched up slightly in premarket. CoreWeave — Shares of the cloud AI company shed nearly 6% after announcing a $2 billion convertible debt offering. Five Below — The discount retailer rose more than 2% after Truist upgraded it to buy from hold. “Given the sustainability of the comps and upward earnings potential, we think the stock has much further to go on the upside,” the firm wrote about Five Below. — CNBC’s Yun Li contributed reporting.