[llvm] [SLP][NFC] Simplify population of `ReducedVals` (PR #156292)

[Piotr Fusik via llvm-commits]

https://github.com/pfusik created https://github.com/llvm/llvm-project/pull/156292

None

>From 568322b1d2334f6cdd66491bad3ed1f594e9ea30 Mon Sep 17 00:00:00 2001
From: Piotr Fusik <p.fusik at samsung.com>
Date: Mon, 1 Sep 2025 10:06:16 +0200
Subject: [PATCH] [SLP][NFC] Simplify population of `ReducedVals`

---
 .../Transforms/Vectorize/SLPVectorizer.cpp    | 25 +++++++++----------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 4d4f34a0bdd38..aab88190fdb7b 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -23835,21 +23835,20 @@ class HorizontalReduction {
       stable_sort(PossibleRedValsVect, [](const auto &P1, const auto &P2) {
         return P1.size() > P2.size();
       });
-      int NewIdx = -1;
+      bool First = true;
       for (ArrayRef<Value *> Data : PossibleRedValsVect) {
-        if (NewIdx < 0 ||
-            (!isGoodForReduction(Data) &&
-             (!isa<LoadInst>(Data.front()) ||
-              !isa<LoadInst>(ReducedVals[NewIdx].front()) ||
-              getUnderlyingObject(
-                  cast<LoadInst>(Data.front())->getPointerOperand()) !=
-                  getUnderlyingObject(
-                      cast<LoadInst>(ReducedVals[NewIdx].front())
-                          ->getPointerOperand())))) {
-          NewIdx = ReducedVals.size();
+        if (First) {
+          First = false;
           ReducedVals.emplace_back();
-        }
-        ReducedVals[NewIdx].append(Data.rbegin(), Data.rend());
+        } else if (!isGoodForReduction(Data)) {
+          auto *LI = dyn_cast<LoadInst>(Data.front());
+          auto *LastLI = dyn_cast<LoadInst>(ReducedVals.back().front());
+          if (!LI || !LastLI ||
+              getUnderlyingObject(LI->getPointerOperand()) !=
+                  getUnderlyingObject(LastLI->getPointerOperand()))
+            ReducedVals.emplace_back();
+        }
+        ReducedVals.back().append(Data.rbegin(), Data.rend());
       }
     }
     // Sort the reduced values by number of same/alternate opcode and/or pointer