[llvm] [AArch64][SVE] - Fix crash Possible incorrect use of EVT::getVectorNumElements(). (PR #218733)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

> I'm not sure how feasible that is because the code below demands the known bits, which might not work for scalable types.

I think known bits works well enough to make this transform work.  (It's not as powerful as the fixed-width version, but it should be sufficient in this context.)

https://github.com/llvm/llvm-project/pull/218733