By Shristi Achar A and Johann M Cherian Dec 12 (Reuters) - Wall Street's main indexes slipped on Tuesday following inflation data that was in line with estimates ahead of the U.S. Federal Reserve's policy decision later in the week, while losses in energy stocks also weighed. Among megacap stocks, Google-parent Alphabet GOOGL.O lost 1.1%, after "Fortnite" maker Epic Games prevailed in its high-profile antitrust trial over the company. Amgen AMGN.O rose 0.8%, limiting losses on the blue-chip Dow, after RBC Capital Markets upgraded the drugmaker's shares to "outperform" from "sector perform".