[llvm] [X86] Recognise vectors with zeros in all upper elements to improve VMOVS*Z folding (PR #193263)

[Phoebe Wang via llvm-commits]

phoebewang wrote:

> Currently the VMOVSHZ (etc.) patterns are mainly limited to merging with X86vzmovl patterns which explicitly demonstrate the upper elements should be zero (and we can remove the X86vzmovl node).

Does it mean we will replace it with X86vzelts in the future?

https://github.com/llvm/llvm-project/pull/193263