[llvm] [LV][EVL] Generate negative strided load/store for reversed load/store (PR #123608)

[Elvis Wang via llvm-commits]

ElvisWang123 wrote:

Hi @wangpc-pp,

This patch is good but I think we need a cost model based decision to decide using negative stride or reverse vector.

We've test the performance on x280 for negative-stride load vs. vector load + reverse. And the results shows negative-stride load 10% more **slower** than reverse.

https://github.com/llvm/llvm-project/pull/123608