[llvm] [GlobalISel] [AArch64] Skip redundant shift amount masking during isel (PR #223136)

[David Green via llvm-commits]

https://github.com/davemgreen commented:

>> There are a couple of cases getting worse in gisel still in this patch that could do with being cleaned up.
> Do you think we can fix these incrementally? Some cases already have PRs ADD, MVN, and NEG.

It looks like you fixed the ones in the patch. Nice one.

One small thing but if you push a new patch each time it makes it difficult to tell what has changed between revisions. If there is a fixup patch then it is easier to see what has changed and the whole thing doesn't need to be checked again each time.

A couple of points below but this looks OK otherwise.

https://github.com/llvm/llvm-project/pull/223136