[llvm] [SelectionDAG] Add PARTIAL_REDUCE_U/SMLA ISD Nodes (PR #125207)

[James Chesterman via llvm-commits]

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@@ -5624,7 +5624,14 @@ class TargetLowering : public TargetLoweringBase {
 
   // Expands PARTIAL_REDUCE_S/UMLA nodes to a series of simpler operations,
   // consisting of zext/sext, extract_subvector, mul and add operations.
-  SDValue expandPartialReduceMLA(SDNode *N, SelectionDAG &DAG) const;
+  SDValue expandPartialReduceMLA(SDLoc DL, SDValue Acc, SDValue Input1,
+                                 SDValue Input2, SelectionDAG &DAG) const;
+
+  // Create the DAG equivalent of vector_partial_reduce where Op1 and Op2 are
+  // its operands and ReducedTY is the return type.
+  static SDValue getPartialReduceAdd(SDLoc DL, EVT ReducedTy, EVT FullTy,
+                                     SDValue Op1, SDValue Op2,
+                                     SelectionDAG &DAG);
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JamesChesterman wrote:

Done, sorry I misunderstood, I thought we might have wanted to keep the two functions separate for now and have the new code path follow the `expandPartialReduceMLA()` function. But I understand now that they would do the same thing, so I've just combined the two functions into the `expandPartialReduceMLA()` function.

https://github.com/llvm/llvm-project/pull/125207