[llvm] [SLP] NFC. Make InstructionsState more constant. (PR #118609)

[Han-Kuan Chen via llvm-commits]

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@@ -8198,20 +8212,20 @@ void BoUpSLP::buildTree_rec(ArrayRef<Value *> VL, unsigned Depth,
     SmallVector<SmallVector<std::pair<Value *, Value *>>> Candidates;
     auto *I1 = cast<Instruction>(VL.front());
     auto *I2 = cast<Instruction>(VL.back());
-    for (int Op = 0, E = S.MainOp->getNumOperands(); Op < E; ++Op)
+    for (int Op = 0, E = S.getMainOp()->getNumOperands(); Op < E; ++Op)
       Candidates.emplace_back().emplace_back(I1->getOperand(Op),
                                              I2->getOperand(Op));
     if (static_cast<unsigned>(count_if(
             Candidates, [this](ArrayRef<std::pair<Value *, Value *>> Cand) {
               return findBestRootPair(Cand, LookAheadHeuristics::ScoreSplat);
-            })) >= S.MainOp->getNumOperands() / 2)
+            })) >= S.getMainOp()->getNumOperands() / 2)
       return false;
-    if (S.MainOp->getNumOperands() > 2)
+    if (S.getMainOp()->getNumOperands() > 2)
       return true;
     if (IsCommutative) {
       // Check permuted operands.
       Candidates.clear();
-      for (int Op = 0, E = S.MainOp->getNumOperands(); Op < E; ++Op)
+      for (int Op = 0, E = S.getMainOp()->getNumOperands(); Op < E; ++Op)
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HanKuanChen wrote:

`E` is required later.

https://github.com/llvm/llvm-project/pull/118609