Check out the companies making headlines in midday trading.

Unity Software — Shares tumbled 17% after the interactive software company announced a merger agreement with app software company ironSource in a $4.4 billion all-stock transaction. Unity also cut its full-year revenue guidance. Shares of ironSource soared more than 45% on the news.

Stitch Fix — Shares of Stitch Fix surged 18% after Bill Gurley of Benchmark Capital, who also sits on the board of the clothing company, announced that he’d bought 1 million shares of the stock, adding to his previous stake of 1.22 million shares. Gurley paid an average price of $5.43 per share for the stock, according to an SEC filing.

Twitter — Shares of the social media company climbed more than 8% after the firm filed suit against Elon Musk after he terminated his $44 billion deal to buy the company. Twitter said that Musk’s conduct during his pursuit of the social network amounted to “bad faith.” The stock is still down nearly 2% week to date.

DigitalOcean — Shares of the cloud computing company dropped 2% after Goldman Sachs issued a double downgrade to sell from buy. DigitalOcean could get hit with slowing demand, particularly from consumers overseas, the firm said.

Delta Air Lines — Shares of Delta Air Lines dropped 6% following a mixed earnings report. Other airline stocks dropped. Shares of American Airlines also declined more than 4%, and Alaska Air Group fell more than 2%.

Fastenal — Shares of Fastenal declined 5% after the industrial supplies company reported softening demand in its most recent quarter. “Demand remained generally healthy, but there were certain signs of softening that emerged in May and June,” read remarks from CEO Daniel L. Florness.

Gap — Shares of the retailer dropped 2.5% on the heels of a downgrade to hold from buy at Deutsche Bank. The firm cited execution issues at the company, the increased promotional environment of retail and the departure of CEO Sonia Syngal as reasons for the downgrade.

Advanced Micro Devices — Several chip stocks outperformed on Wednesday. Shares of Advanced Micro Devices and Qualcomm each jumped more than 2%.

— CNBC’s Yun Li, Jesse Pound and Carmen Reinicke contributed reporting