[llvm] [SLP] Ensure TreeCost is scaled for ordered fadd reductions (PR #199388)

[Alexey Bataev via llvm-commits]

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@@ -18752,7 +18757,8 @@ InstructionCost BoUpSLP::calculateTreeCostAndTrimNonProfitable(
       }
     }
     if (!CostIsFree && !Scale) {
-      Scale = IsGatherLike ? getGatherNodeEffectiveScale(TE)
+      Scale = IsGatherLike ? getGatherNodeEffectiveScale(
+                                 TE, (TE.Idx == 0) ? RdxRoot : nullptr)
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alexey-bataev wrote:

Drop parens

https://github.com/llvm/llvm-project/pull/199388