Western Digital shares are sliding Wednesday as a landmark IPO filing from a Chinese memory rival stoked fears of a powerful new competitor.

China's leading memory chipmaker, CXMT, is set to debut on the Shanghai Stock Exchange on July 27 after launching a 29.5 billion yuan IPO, expected to be Asia's largest this year.

Chinese memory giant CXMT, which we have discussed extensively in recent weeks due to its critical role in the Chinese memory supply chain (here, here and here), and which Apple…