[llvm] Use llvm::SmallVector::pop_back_val (NFC) (#136533)

Author: kazutakahirata

llvm/lib/CodeGen/ComplexDeinterleavingPass.cpp

@@ -1151,8 +1151,7 @@ ComplexDeinterleavingGraph::identifyReassocNodes(Instruction *Real,
     SmallVector<PointerIntPair<Value *, 1, bool>> Worklist = {{Insn, true}};
     SmallPtrSet<Value *, 8> Visited;
     while (!Worklist.empty()) {
-      auto [V, IsPositive] = Worklist.back();
-      Worklist.pop_back();
+      auto [V, IsPositive] = Worklist.pop_back_val();
       if (!Visited.insert(V).second)
         continue;
 

llvm/lib/CodeGen/SplitKit.cpp

@@ -1519,8 +1519,7 @@ void SplitEditor::forceRecomputeVNI(const VNInfo &ParentVNI) {
   const LiveInterval &ParentLI = Edit->getParent();
   const SlotIndexes &Indexes = *LIS.getSlotIndexes();
   do {
-    const VNInfo &VNI = *WorkList.back();
-    WorkList.pop_back();
+    const VNInfo &VNI = *WorkList.pop_back_val();
     for (unsigned I = 0, E = Edit->size(); I != E; ++I)
       forceRecompute(I, VNI);
     if (!VNI.isPHIDef())

llvm/lib/Support/SuffixTree.cpp

@@ -95,8 +95,7 @@ void SuffixTree::setSuffixIndices() {
   unsigned CurrNodeLen = 0;
   ToVisit.push_back({CurrNode, CurrNodeLen});
   while (!ToVisit.empty()) {
-    std::tie(CurrNode, CurrNodeLen) = ToVisit.back();
-    ToVisit.pop_back();
+    std::tie(CurrNode, CurrNodeLen) = ToVisit.pop_back_val();
     // Length of the current node from the root down to here.
     CurrNode->setConcatLen(CurrNodeLen);
     if (auto *InternalNode = dyn_cast<SuffixTreeInternalNode>(CurrNode))