[CodeGen][SVE] Avoid scalarizing zero splat stores on scalable vectors.

[hkao13]

Summary

Implemented in replaceZeroVectorStore(). Fixes several warnings in AArch64 SVE unit tests.

[sdesmalen]

After D80720 this function will no longer be called from splitStores for scalable vectors, but it still makes sense to bail out early in case that ever changes.

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

12071–12075

Probably better to bail out directly if VT is scalable and leave the call to getVectorNumElements() intact.

[hkao13]

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

12071–12075

Thanks for the review. I reverted the change to use getVectorNumElements(), and added a check above.

[sdesmalen]

LGTM

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

12073

I think you can remove the condition || !VT.isFixedLengthVector(), because this function would otherwise break if it isn't.

[hkao13]

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

12073

Fixed, thanks for feedback.