[llvm] [VectorCombine] Fold binary op of reductions. (PR #121567)

[Mikhail Gudim via llvm-commits]

mgudim wrote:

@davemgreen I still need your input on this: https://github.com/llvm/llvm-project/pull/121567#issuecomment-2650197122 Should I basically repeat all the code from LoopVectorizer here?

In general, I find it weird that opt has to know about some pattern which exists on AArch64 (dot product) and try to preserve it

https://github.com/llvm/llvm-project/pull/121567