Stock up: Google-parent Alphabet joins $1 trillion valuation club

As Google-parent Alphabet Inc became on Thursday the fourth U.S. company to top a market value of more than $1 trillion, some funds holding its shares are wondering whether now is the time to cash in on the stock's extraordinary gains.

Shares of the Internet search giant are up nearly 17% over the last three months, outpacing a broader rally in the S&P 500 index over the same period by 6 percentage points.

Short interest in the stock, a measure of how many investors are betting on a price decline, is at 1%, near a 52-week high for the company