[llvm] [X86][PartialReduction] Lower zext-byte add reductions to vpsadbw (PR #201076)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon requested changes to this pull request.

Please can you use the use the vector.reduce.add.*** intrinsic call instead of the expanded codegen.

Merge some of the files - positive/negative pairs in particular

https://github.com/llvm/llvm-project/pull/201076