[llvm] [LV] Add support for partial reductions without a binary op (PR #133922)

[Florian Hahn via llvm-commits]

================
@@ -24,22 +24,23 @@ struct HistogramInfo;
 struct VFRange;
 
 /// A chain of instructions that form a partial reduction.
-/// Designed to match: reduction_bin_op (bin_op (extend (A), (extend (B))),
-/// accumulator).
+/// Designed to match either:
+///   reduction_bin_op (extend (A), accumulator), or
+///   reduction_bin_op (bin_op (extend (A), (extend (B))), accumulator).
 struct PartialReductionChain {
   PartialReductionChain(Instruction *Reduction, Instruction *ExtendA,
-                        Instruction *ExtendB, Instruction *BinOp)
-      : Reduction(Reduction), ExtendA(ExtendA), ExtendB(ExtendB), BinOp(BinOp) {
-  }
+                        Instruction *ExtendB, Instruction *ExtendUser)
+      : Reduction(Reduction), ExtendA(ExtendA), ExtendB(ExtendB),
+        ExtendUser(ExtendUser) {}
   /// The top-level binary operation that forms the reduction to a scalar
   /// after the loop body.
   Instruction *Reduction;
   /// The extension of each of the inner binary operation's operands.
   Instruction *ExtendA;
   Instruction *ExtendB;
 
-  /// The binary operation using the extends that is then reduced.
-  Instruction *BinOp;
+  /// The user of the extend that is then reduced.
----------------
fhahn wrote:

```suggestion
  /// The user of the extends that is then reduced.
```

Still for multiple extends, right?

https://github.com/llvm/llvm-project/pull/133922