[llvm] [VPlan] Sink vector loop region recipes in licm (PR #172343)

[Luke Lau via llvm-commits]

lukel97 wrote:

> Looks like this is similar to @Mel-Chen 's #168031

Oh I didn't see that PR before, looks like we're doing the same thing! 

Just briefly checking that PR it looks like this one is a bit more general since it can sink down to the NCD block not just the regions successor. I think this PR also avoids the need for a worklist by doing a post order traversal. I'm not sure why this PR doesn't seem to need the VPlanUnroll.cpp changes either

https://github.com/llvm/llvm-project/pull/172343