[llvm] LAA: fix logic for MaxTargetVectorWidth (PR #125487)

[Florian Hahn via llvm-commits]

https://github.com/fhahn approved this pull request.

LGTM, thanks! Left one more comment inline to check if COMMON could be used there.

Might be good to clarify in the commit message/title that this  now uses the fixed register width if scalable vectorization is not enabled (via TargetTransformInfo::enableScalableVectorization) and that this improves results if there are scalable vector registers, but they shouldn't be used.


https://github.com/llvm/llvm-project/pull/125487