[llvm] [VectorCombine] Enable transform 'scalarizeLoadExtract' for scalable vector types (PR #65443)

[Florian Hahn via llvm-commits]

fhahn wrote:

> The transform 'scalarizeLoadExtract' can be applied to scalable vector types if the index is less than the minimum number of elements.
> 


Would be good to clarify this in the commit message; we need to prove that the index is < # of vector elements independent of whether the vector is scalable or not. IIUC the restriction on minimum number of elements is only because it makes things work well with the existing reasoning, but this restriction could be weakened in the future, i.e. there may be scenarios where we could prove an index < vscale * min number of elements.

https://github.com/llvm/llvm-project/pull/65443