[llvm] [ExpandVectorPredication] Expand vp.load.ff. (PR #154440)

[Luke Lau via llvm-commits]

lukel97 wrote:

> The current LangRef text allows the EVL parameter to be zero. As a result, this lowering is unsound - we need to conditionally zero the first mask element based on whether the EVL is zero.

The EVL is folded into the mask in `foldEVLIntoMask` so if the EVL is zero then the mask in the expansion will also be zero


https://github.com/llvm/llvm-project/pull/154440