Rebase and update

Rebase and add comment on VF selection.

In D157484#4638295, @fhahn wrote:

That sounds like a good first step, can you share a patch for that?

In D157484#4628634, @fhahn wrote:

Looks reasonable overall, my only concern is that this adds another codepath to the native path which is already lacking test coverage in general. Do you have any idea/suggestion on how to improve end-to-end test coverage, e.g. in llvm-test-suite (could be adding some SingleSource tests with loop nests and #pragma clang loop vectorize_width(4)?

Add check for optimization remarks and rejection of scalable VFs on targets without scalable vectors.

Fix clang-format

Rebase

Rebase and add call to reportVectorizationFailure()

Please let me know if there is anything I can improve.

Please let me know if there is anything else I can improve.

iamlouk this patch addressed 3 different problems: outerloop vectorization for scalable vectors; vec-report for outerloop and stability fix for outerloop; As fhahn suggested, I split last 2 into their own review: D150696 and D150700.
I assume your approach to enable outerloop vectorization for scalable vectors is more generic than mine adhoc approach here, so can you please post your patch instead ?

Address code review comments: use mtriple and check full IR

Remove unnecessary attributes in test.

Fix clang-format issue.

@nikolaypanchenko, thank you for this patch! Sorry to bother you, but will you update the revision (to support scalable vectorization factors)? I have written a patch myself with the same intention (although it works slightly differently, I also modified determineVPlanVF), not knowing that this revision already exists, so if you do not have the resources for this at the moment, I could present an alternative one, but only if you are ok with that of course.

Thank you for your feedback compnerd. Changing the implementation to mimic GCC's way of handling it's equivalent of this intrinsic requires a completely new approach though, so I am abandoning this revision.

Rebase and Windows on AArch64 treatment