Merge r358245 and r358775 to the 8.0 branch

[llvmbot]

Bugzilla Link	41543
Resolution	WONTFIX
Resolved on	Aug 11, 2020 00:00
Version	8.0
OS	OpenBSD
Blocks	#40566
Reporter	LLVM Bugzilla Contributor
CC	@zygoloid,@tstellar

Extended Description

Merge r358245 and r358775 back to the 8.0 branch. Enable frame pointer elimination for OpenBSD.

[tstellar]

These seem more like new features, why are these changes needed in the 8.0.1 release?