[llvm] [AArch64] Fix incorrect big-endian spill in foldMemoryOperandImpl (PR #65601)

[David Green via llvm-commits]

davemgreen wrote:

Sorry I missed this - github isn't a great system at times.

This will create larger stores than we had in the past? Is it worth making this "little endian only", or are the smaller stores not worth it, when you start considering the load-store forwarding and that kind of thing?

And does the IsFill code below have similar problems, or is it already valid?

https://github.com/llvm/llvm-project/pull/65601