[llvm] [LV] Simplify the chain traversal in `getScaledReductions()` (NFCI) (PR #184830)

[Benjamin Maxwell via llvm-commits]

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@@ -6055,22 +6049,20 @@ static bool isValidPartialReduction(const VPPartialReductionChain &Chain,
       Range);
 }
 
-/// Examines reduction operations to see if the target can use a cheaper
-/// operation with a wider per-iteration input VF and narrower PHI VF.
-/// Recursively calls itself to identify chained scaled reductions.
-/// Returns true if this invocation added an entry to Chains, otherwise false.
-static bool
-getScaledReductions(VPReductionPHIRecipe *RedPhiR, VPValue *PrevValue,
-                    SmallVectorImpl<VPPartialReductionChain> &Chains,
-                    VPCostContext &CostCtx, VFRange &Range) {
-  auto *UpdateR = dyn_cast<VPWidenRecipe>(PrevValue);
-  if (!UpdateR || !Instruction::isBinaryOp(UpdateR->getOpcode()))
-    return false;
+/// Holds the binary operation used to compute the extended operand and the
+/// casts that feed into it.
+struct ExtendedReductionOperand {
+  VPWidenRecipe *BinOp = nullptr;
+  std::array<VPWidenCastRecipe *, 2> CastRecipes = {nullptr};
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MacDue wrote:

Yep, wrong constructor :+1: Fixed this 

https://github.com/llvm/llvm-project/pull/184830