[llvm] [DAGCombine] Fold vselect with splat zero (PR #147305)

[via llvm-commits]

badumbatish wrote:

> although wasm doesn't seem to have an andnot instruction, it might be worthwhile exploring if returning true is profitable for vectors anyway.

I think the current impl checks if the scalar bit size is equal before folding to avoid having extra sign extending. I'm not sure if this is enough.

https://github.com/llvm/llvm-project/pull/147305