[llvm] [VPlan] Strip bad TODO in VPTransformState::get (NFC) (PR #166146)

[Luke Lau via llvm-commits]

lukel97 wrote:

> > > I presume the point of that TODO is not that it should emit a VPInstruction::Broadcast at that point, but all single scalar values should be wrapped in a VPInstruction::Broadcast before execution. So VPTransformState::get should never have to emit a splat.
> > 
> > 
> > Yep, that's the intention of the TODO
> 
> Should we create a new VPTransform to wrap single-scalars in broadcasts?

I think `materializeBroadcasts` does part of this? I'm not super familiar with it though, maybe it doesn't handle all single scalars yet. 

https://github.com/llvm/llvm-project/pull/166146