[llvm] DAG: Handle load in SimplifyDemandedVectorElts (PR #122671)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

I'm still looking at the x86 mess - but something I've hit is that the hasOneUse() checks on the shouldReduceLoadWidth callback are often getting confused by extra uses of the load nodes's chain - is there anything we can do is clean that up? (See also #126764)

https://github.com/llvm/llvm-project/pull/122671