[llvm] [AArch64][SVE] Add partial reduction SDNodes (PR #117185)

[Benjamin Maxwell via llvm-commits]

================
@@ -3010,6 +3010,22 @@ class MaskedHistogramSDNode : public MaskedGatherScatterSDNode {
   }
 };
 
+class PartialReduceAddSDNode : public SDNode {
+public:
+  friend class SelectionDAG;
----------------
MacDue wrote:

A special class is probably not needed (most nodes don't have these), and I think there may be some issues (see next comment). 

https://github.com/llvm/llvm-project/pull/117185