Exhibit 99.4

AGREEMENT OF JOINT FILING

Each of the undersigned acknowledge and agree that the foregoing statement on Schedule 13G is filed on behalf of each of the undersigned and that all subsequent amendments to this statement on Schedule 13G shall be filed on behalf of each of the undersigned without the necessity of filing additional joint filing agreements. Each of the undersigned acknowledge that each shall be responsible for the timely filing of such amendments, and for the completeness and accuracy of the information concerning him or it contained herein and therein, but shall not be responsible for the completeness and accuracy of the information concerning the others, except to the extent that he or it knows or has reason to believe that such information is inaccurate.

	MUBADALA INVESTMENT COMPANY PJSC

	August 15, 2019
	Date

	/s/ Andre C. Namphy
	Signature

	Andre C. Namphy / Authorized Signatory
	Name/Title

	MUBADALA DEVELOPMENT COMPANY PJSC

	August 15, 2019
	Date

	/s/ Andre C. Namphy
	Signature

	Andre C. Namphy / Authorized Signatory
	Name/Title


	WEST COAST HITECH L.P. by its general partner, WEST COAST HITECH G.P., LTD.

	August 15, 2019
	Date

	/s/ Andre C. Namphy
	Signature

	Andre C. Namphy / Authorized Signatory
	Name/Title

	WEST COAST HITECH G.P., LTD.

	August 15, 2019
	Date

	/s/ Andre C. Namphy
	Signature

	Andre C. Namphy / Authorized Signatory
	Name/Title