Basic net loss per share attributable to Portola Common Stockholders has been computed by dividing the net loss attributable to Portola Common Stockholders by the weighted-average number of shares of Common Stock outstanding during the period. Diluted net loss per share attributable to Portola Common Stockholders is calculated by dividing net loss attributable to Portola Common Stockholders by the weighted average number of shares of Common Stock and potential dilutive securities outstanding during the period. Since we were in a loss position for all periods presented, basic net loss per share attributable to Portola Common Stockholders is the same as diluted net loss per share attributable to Portola Common Stockholders as the inclusion of all potentially dilutive common shares would have been anti-dilutive.

The following outstanding shares of common stock equivalents were excluded from the computation of diluted net loss per share attributable to Portola Common Stockholders for the periods presented because including them would have been antidilutive:

	As of March 31,
	2019		2018
Stock options to purchase common stock		8,331,332		7,293,733
Performance stock options		624,321		163,481
Common stock warrants		1,500		1,500
Restricted stock units		1,179,480		646,125
Performance stock units		108,127		393,225
Employee stock purchase plan		14,619		12,391

Up to 500,000 shares of our common stock may be contingently issued, if certain regulatory and performance conditions are met under an agreement with a contract manufacturer, as described in Note 6, “Contract Manufacturing Agreements”, to these condensed consolidated financial statements.