[llvm] [LoopVectorize][AArch64][SVE] Generate wide active lane masks (PR #81140)

[Momchil Velikov via llvm-commits]

momchil-velikov wrote:

>  always emit a VF*UF sized active lane mask when it is used for control flow. Then leave the code generator to split it when necessary.

Because the code generator can't split it without introducing inefficient control flow for wrap-around checks.

> Perhaps we'll need to add wrap flag support to get.active.mask to make that job easier but this should not be all that different to what LoopVectorize would have to do anyway.

What would be the advantage compared to the current approach?

https://github.com/llvm/llvm-project/pull/81140