Look out, Mentor.

Noted investor/corporate raider Carl Icahn keeps upping his stake in the EDA company. At last report, it was 9.5% (that’s as of Tuesday), up from 6.86% a month ago. Reports hold that Icahn plans “to discuss ways to maximize shareholder value with the Mentor management.”

Even though the company’s stock is up more than 75% over the past year, Icahn’s interest can’t be comforting news to Mentor. Indeed, it may be that Icahn’s buying and holding (coupled with similar moves by those looking to draft off his moves) is helping boost the price.

In his 10+ years at the helm of Mentor, chairman and CEO Wally Rhines has been a good steward, hands-on and clearly vested in the long-term outcome of the company and the industry. Multi-billionaire raiders like Icahn might be able to “unlock” a little more wealth — but for whom, and at what cost?