** Shares of U.S. software companies extend gains for a second straight session after coming under selling pressure for much of this year on concerns about new AI tools upending traditional business models

** The S&P 500 Software and Services index .SPLRCIS rises 2.3%, adding to a 1.25% gain in the prior session

** Cloud software provider Salesforce CRM.N gains 2.1% ahead of quarterly results, expected after the bell; while U.S.-listed shares of Thomson Reuters TRI.TO add 8.5% after co announces $600 mln share buyback and $605 mln return of capital

** CrowdStrike CRWD.O, Intuit INTU.O and Atlassian Corp TEAM.O gain between 1.2% and 3.3%

** The broader software sector rallied on Tuesday after an announcement that artificial intelligence startup Anthropic was partnering with an array of companies

** SPLRCIS still down 21% YTD

(Reporting by Avinash P in Bengaluru)

((Avinash.P@thomsonreuters.com;))