Check out the companies making headlines before the bell: Nvidia — The chip stock rose 0.5% after the company unveiled new autonomous vehicle software at CES, the global tech conference. Vistra — Shares rose 4.7% after the electricity generation company said it agreed to acquire Cogentrix Energy for roughly $4 billion. Microchip Technology — The stock advanced 4.2% after Microchip Technology issued fiscal third-quarter revenue guidance of about $1.185 billion, higher than prior forecast of $1.109 billion to $1.149 billion. Onestream — Shares surged 22% after Bloomberg News, citing people familiar, reported that buyout firm Hg is in advanced talks to acquire the financial software maker. Under Armour — The stock jumped about 5% after Fairfax Financial disclosed it purchased nearly 42 million shares of the sportswear company, representing a 22% stake. Veeva Systems — The provider of cloud services for the life sciences industry gained 1.9% after Veeva’s board approved a share repurchase program with authorization to purchase up to $2 billion in Class A common stock. American International Group — The global insurer fell 1.5% after announcing CEO Peter Zaffino will step down by mid-year and move into the role of executive chair of the board. Zaffino will be replaced by former Aon president Eric Andersen, effective February 16. — CNBC’s Michelle Fox contributed reporting.