Please merge r369886 ([LoopUnroll] Handle certain PHIs in full unrolling properly)

[fhahn]

Bugzilla Link	43118
Resolution	FIXED
Resolved on	Aug 29, 2019 12:00
Version	9.0
OS	All
Blocks	#41819
CC	@zmodem

Extended Description

This fixes a miscompile when unrolling some loops with -Oz.

[zmodem]

Is the miscompile a regression from LLVM 8?

I'm a little vary of merging a fix like this so close to the release, in case it breaks something else..

[fhahn]

Yes it is a regression from LLVM 8.

Alternatively we could revert r364398 on the release branch(https://reviews.llvm.org/rL364398)

[zmodem]

Okay, thanks for explaining! I've merged the fix in r370182.

[fhahn]

Awesome, thanks!