[llvm] [AArch64][SVE] Enable max vector bandwidth for SVE (PR #109671)

[David Green via llvm-commits]

davemgreen wrote:

My understanding is this is a pretty large change to make, changing the chosen vector factor for a lot of vectorized loops. We were quite careful when doing it for Neon to make sure the performance was OK overall, and it had decent theory behind it. We implemented a number of fixes and improvements to make sure that the performance for larger vector sizes was acceptable.

Do you have performance results for SVE? Is the main reason for dot vectorization? SVE has a different vectorization scheme in general where it relies more on top/bottom vectorization (which are not currently supported very much) and extending load / truncating stores.

https://github.com/llvm/llvm-project/pull/109671