[llvm] [SLP] Order clustered load base pointers by ascending offsets (PR #100653)

[David Green via llvm-commits]

https://github.com/davemgreen commented:

Thanks for the review.

> Would be good to have a test that shows benefits, current test changes do no demonstrate this

The phase-ordering test shows the benefit as the final shuffles are much better for AAch64. `[0 2 4 6 ...]` is a zip, where as `[0 3 4 7 ...]` is a difficult shuffle to materialize. And `[0 1 2 3 ...]` is obviously better than `[0 4 1 5 ...]` at the end. I can try to add a comment to the test case.

https://github.com/llvm/llvm-project/pull/100653