[SLP][NFC]Format and improve function, returning std::optional<struct>,

NFC.

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -294,7 +294,7 @@ static bool isCommutative(Instruction *I) {
 /// \returns inserting index of InsertElement or InsertValue instruction,
 /// using Offset as base offset for index.
 static std::optional<unsigned> getInsertIndex(const Value *InsertInst,
-                                         unsigned Offset = 0) {
+                                              unsigned Offset = 0) {
   int Index = Offset;
   if (const auto *IE = dyn_cast<InsertElementInst>(InsertInst)) {
     const auto *VT = dyn_cast<FixedVectorType>(IE->getType());
@@ -1200,7 +1200,8 @@ class BoUpSLP {
   /// reordered and return the most optimal order.
   /// \param TopToBottom If true, include the order of vectorized stores and
   /// insertelement nodes, otherwise skip them.
-  std::optional<OrdersType> getReorderingData(const TreeEntry &TE, bool TopToBottom);
+  std::optional<OrdersType> getReorderingData(const TreeEntry &TE,
+                                              bool TopToBottom);
 
   /// Reorders the current graph to the most profitable order starting from the
   /// root node to the leaf nodes. The best order is chosen only from the nodes
@@ -1798,9 +1799,10 @@ class BoUpSLP {
     // Search all operands in Ops[*][Lane] for the one that matches best
     // Ops[OpIdx][LastLane] and return its opreand index.
     // If no good match can be found, return std::nullopt.
-    std::optional<unsigned> getBestOperand(unsigned OpIdx, int Lane, int LastLane,
-                                      ArrayRef<ReorderingMode> ReorderingModes,
-                                      ArrayRef<Value *> MainAltOps) {
+    std::optional<unsigned>
+    getBestOperand(unsigned OpIdx, int Lane, int LastLane,
+                   ArrayRef<ReorderingMode> ReorderingModes,
+                   ArrayRef<Value *> MainAltOps) {
       unsigned NumOperands = getNumOperands();
 
       // The operand of the previous lane at OpIdx.
@@ -2812,7 +2814,8 @@ class BoUpSLP {
 #endif
 
   /// Create a new VectorizableTree entry.
-  TreeEntry *newTreeEntry(ArrayRef<Value *> VL, std::optional<ScheduleData *> Bundle,
+  TreeEntry *newTreeEntry(ArrayRef<Value *> VL,
+                          std::optional<ScheduleData *> Bundle,
                           const InstructionsState &S,
                           const EdgeInfo &UserTreeIdx,
                           ArrayRef<int> ReuseShuffleIndices = std::nullopt,
@@ -3768,10 +3771,8 @@ BoUpSLP::findReusedOrderedScalars(const BoUpSLP::TreeEntry &TE) {
           return false;
       return true;
     };
-    if (IsIdentityOrder(CurrentOrder)) {
-      CurrentOrder.clear();
-      return CurrentOrder;
-    }
+    if (IsIdentityOrder(CurrentOrder))
+      return OrdersType();
     auto *It = CurrentOrder.begin();
     for (unsigned I = 0; I < NumScalars;) {
       if (UsedPositions.test(I)) {
@@ -3784,7 +3785,7 @@ BoUpSLP::findReusedOrderedScalars(const BoUpSLP::TreeEntry &TE) {
       }
       ++It;
     }
-    return CurrentOrder;
+    return std::move(CurrentOrder);
   }
   return std::nullopt;
 }
@@ -3977,7 +3978,7 @@ BoUpSLP::findPartiallyOrderedLoads(const BoUpSLP::TreeEntry &TE) {
 
   BoUpSLP::OrdersType Order;
   if (clusterSortPtrAccesses(Ptrs, ScalarTy, *DL, *SE, Order))
-    return Order;
+    return std::move(Order);
   return std::nullopt;
 }
 
@@ -4026,8 +4027,8 @@ static bool areTwoInsertFromSameBuildVector(
   return false;
 }
 
-std::optional<BoUpSLP::OrdersType> BoUpSLP::getReorderingData(const TreeEntry &TE,
-                                                         bool TopToBottom) {
+std::optional<BoUpSLP::OrdersType>
+BoUpSLP::getReorderingData(const TreeEntry &TE, bool TopToBottom) {
   // No need to reorder if need to shuffle reuses, still need to shuffle the
   // node.
   if (!TE.ReuseShuffleIndices.empty()) {
@@ -4081,8 +4082,8 @@ std::optional<BoUpSLP::OrdersType> BoUpSLP::getReorderingData(const TreeEntry &T
     }
     if (all_of(enumerate(ResOrder),
                [](const auto &Data) { return Data.index() == Data.value(); }))
-      return {}; // Use identity order.
-    return ResOrder;
+      return std::nullopt; // No need to reorder.
+    return std::move(ResOrder);
   }
   if (TE.State == TreeEntry::Vectorize &&
       (isa<LoadInst, ExtractElementInst, ExtractValueInst>(TE.getMainOp()) ||
@@ -4138,8 +4139,8 @@ std::optional<BoUpSLP::OrdersType> BoUpSLP::getReorderingData(const TreeEntry &T
     for (unsigned Id = 0, Sz = Phis.size(); Id < Sz; ++Id)
       ResOrder[Id] = PhiToId[Phis[Id]];
     if (IsIdentityOrder(ResOrder))
-      return {};
-    return ResOrder;
+      return std::nullopt; // No need to reorder.
+    return std::move(ResOrder);
   }
   if (TE.State == TreeEntry::NeedToGather) {
     // TODO: add analysis of other gather nodes with extractelement
@@ -4165,7 +4166,7 @@ std::optional<BoUpSLP::OrdersType> BoUpSLP::getReorderingData(const TreeEntry &T
       if (Reuse || !CurrentOrder.empty()) {
         if (!CurrentOrder.empty())
           fixupOrderingIndices(CurrentOrder);
-        return CurrentOrder;
+        return std::move(CurrentOrder);
       }
     }
     if (std::optional<OrdersType> CurrentOrder = findReusedOrderedScalars(TE))