DomTree: Remove getChildren() accessor

Summary:
Avoid exposing details about how children are stored. This will enable
subsequent type-erasure changes.

New methods are introduced to cover common access patterns.

Change-Id: Idb5f4b1b9c84e4cc71ddb39bb52a388682f5674f

Reviewers: arsenm, RKSimon, mehdi_amini, courbet

Subscribers: qcolombet, sdardis, wdng, hiraditya, jrtc27, zzheng, atanasyan, asbirlea, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D83083

15 files changed, 46 insertions, 49 deletions

diff --git a/llvm/include/llvm/Support/GenericDomTree.h b/llvm/include/llvm/Support/GenericDomTree.h
index f90fe0b..d932938 100644
--- a/llvm/include/llvm/Support/GenericDomTree.h
+++ b/llvm/include/llvm/Support/GenericDomTree.h
@@ -77,18 +77,25 @@ template <class NodeT> class DomTreeNodeBase {
   const_iterator begin() const { return Children.begin(); }
   const_iterator end() const { return Children.end(); }
 
+  DomTreeNodeBase *const &back() const { return Children.back(); }
+  DomTreeNodeBase *&back() { return Children.back(); }
+
+  iterator_range<iterator> children() { return make_range(begin(), end()); }
+  iterator_range<const_iterator> children() const {
+    return make_range(begin(), end());
+  }
+
   NodeT *getBlock() const { return TheBB; }
   DomTreeNodeBase *getIDom() const { return IDom; }
   unsigned getLevel() const { return Level; }
 
-  const std::vector<DomTreeNodeBase *> &getChildren() const { return Children; }
-
   std::unique_ptr<DomTreeNodeBase> addChild(
       std::unique_ptr<DomTreeNodeBase> C) {
     Children.push_back(C.get());
     return C;
   }
 
+  bool isLeaf() const { return Children.empty(); }
   size_t getNumChildren() const { return Children.size(); }
 
   void clearAllChildren() { Children.clear(); }
@@ -619,7 +626,7 @@ protected:
   void eraseNode(NodeT *BB) {
     DomTreeNodeBase<NodeT> *Node = getNode(BB);
     assert(Node && "Removing node that isn't in dominator tree.");
-    assert(Node->getChildren().empty() && "Node is not a leaf node.");
+    assert(Node->isLeaf() && "Node is not a leaf node.");
 
     DFSInfoValid = false;
 
diff --git a/llvm/include/llvm/Support/GenericDomTreeConstruction.h b/llvm/include/llvm/Support/GenericDomTreeConstruction.h
index 7c94a26..1e9b0f2 100644
--- a/llvm/include/llvm/Support/GenericDomTreeConstruction.h
+++ b/llvm/include/llvm/Support/GenericDomTreeConstruction.h
@@ -1396,7 +1396,7 @@ struct SemiNCAInfo {
       const TreeNodePtr Node = NodeToTN.second.get();
 
       // Handle tree leaves.
-      if (Node->getChildren().empty()) {
+      if (Node->isLeaf()) {
         if (Node->getDFSNumIn() + 1 != Node->getDFSNumOut()) {
           errs() << "Tree leaf should have DFSOut = DFSIn + 1:\n\t";
           PrintNodeAndDFSNums(Node);
@@ -1508,7 +1508,8 @@ struct SemiNCAInfo {
     for (auto &NodeToTN : DT.DomTreeNodes) {
       const TreeNodePtr TN = NodeToTN.second.get();
       const NodePtr BB = TN->getBlock();
-      if (!BB || TN->getChildren().empty()) continue;
+      if (!BB || TN->isLeaf())
+        continue;
 
       LLVM_DEBUG(dbgs() << "Verifying parent property of node "
                         << BlockNamePrinter(TN) << "\n");
@@ -1517,7 +1518,7 @@ struct SemiNCAInfo {
         return From != BB && To != BB;
       });
 
-      for (TreeNodePtr Child : TN->getChildren())
+      for (TreeNodePtr Child : TN->children())
         if (NodeToInfo.count(Child->getBlock()) != 0) {
           errs() << "Child " << BlockNamePrinter(Child)
                  << " reachable after its parent " << BlockNamePrinter(BB)
@@ -1541,17 +1542,17 @@ struct SemiNCAInfo {
     for (auto &NodeToTN : DT.DomTreeNodes) {
       const TreeNodePtr TN = NodeToTN.second.get();
       const NodePtr BB = TN->getBlock();
-      if (!BB || TN->getChildren().empty()) continue;
+      if (!BB || TN->isLeaf())
+        continue;
 
-      const auto &Siblings = TN->getChildren();
-      for (const TreeNodePtr N : Siblings) {
+      for (const TreeNodePtr N : TN->children()) {
         clear();
         NodePtr BBN = N->getBlock();
         doFullDFSWalk(DT, [BBN](NodePtr From, NodePtr To) {
           return From != BBN && To != BBN;
         });
 
-        for (const TreeNodePtr S : Siblings) {
+        for (const TreeNodePtr S : TN->children()) {
           if (S == N) continue;
 
           if (NodeToInfo.count(S->getBlock()) == 0) {
diff --git a/llvm/lib/CodeGen/EarlyIfConversion.cpp b/llvm/lib/CodeGen/EarlyIfConversion.cpp
index a67072c..96d4efb 100644
--- a/llvm/lib/CodeGen/EarlyIfConversion.cpp
+++ b/llvm/lib/CodeGen/EarlyIfConversion.cpp
@@ -759,7 +759,7 @@ void updateDomTree(MachineDominatorTree *DomTree, const SSAIfConv &IfConv,
     assert(Node != HeadNode && "Cannot erase the head node");
     while (Node->getNumChildren()) {
       assert(Node->getBlock() == IfConv.Tail && "Unexpected children");
-      DomTree->changeImmediateDominator(Node->getChildren().back(), HeadNode);
+      DomTree->changeImmediateDominator(Node->back(), HeadNode);
     }
     DomTree->eraseNode(B);
   }
diff --git a/llvm/lib/CodeGen/InlineSpiller.cpp b/llvm/lib/CodeGen/InlineSpiller.cpp
index 7e4a89c..41eef2f 100644
--- a/llvm/lib/CodeGen/InlineSpiller.cpp
+++ b/llvm/lib/CodeGen/InlineSpiller.cpp
@@ -1306,10 +1306,7 @@ void HoistSpillHelper::getVisitOrders(
   Orders.push_back(MDT.getBase().getNode(Root));
   do {
     MachineDomTreeNode *Node = Orders[idx++];
-    const std::vector<MachineDomTreeNode *> &Children = Node->getChildren();
-    unsigned NumChildren = Children.size();
-    for (unsigned i = 0; i != NumChildren; ++i) {
-      MachineDomTreeNode *Child = Children[i];
+    for (MachineDomTreeNode *Child : Node->children()) {
       if (WorkSet.count(Child))
         Orders.push_back(Child);
     }
@@ -1377,10 +1374,7 @@ void HoistSpillHelper::runHoistSpills(
 
     // Collect spills in subtree of current node (*RIt) to
     // SpillsInSubTreeMap[*RIt].first.
-    const std::vector<MachineDomTreeNode *> &Children = (*RIt)->getChildren();
-    unsigned NumChildren = Children.size();
-    for (unsigned i = 0; i != NumChildren; ++i) {
-      MachineDomTreeNode *Child = Children[i];
+    for (MachineDomTreeNode *Child : (*RIt)->children()) {
       if (SpillsInSubTreeMap.find(Child) == SpillsInSubTreeMap.end())
         continue;
       // The stmt "SpillsInSubTree = SpillsInSubTreeMap[*RIt].first" below
diff --git a/llvm/lib/CodeGen/MachineCSE.cpp b/llvm/lib/CodeGen/MachineCSE.cpp
index 8c195ad..0953127 100644
--- a/llvm/lib/CodeGen/MachineCSE.cpp
+++ b/llvm/lib/CodeGen/MachineCSE.cpp
@@ -747,9 +747,8 @@ bool MachineCSE::PerformCSE(MachineDomTreeNode *Node) {
   do {
     Node = WorkList.pop_back_val();
     Scopes.push_back(Node);
-    const std::vector<MachineDomTreeNode*> &Children = Node->getChildren();
-    OpenChildren[Node] = Children.size();
-    for (MachineDomTreeNode *Child : Children)
+    OpenChildren[Node] = Node->getNumChildren();
+    for (MachineDomTreeNode *Child : Node->children())
       WorkList.push_back(Child);
   } while (!WorkList.empty());
 
@@ -862,8 +861,7 @@ bool MachineCSE::PerformSimplePRE(MachineDominatorTree *DT) {
   BBs.push_back(DT->getRootNode());
   do {
     auto Node = BBs.pop_back_val();
-    const std::vector<MachineDomTreeNode *> &Children = Node->getChildren();
-    for (MachineDomTreeNode *Child : Children)
+    for (MachineDomTreeNode *Child : Node->children())
       BBs.push_back(Child);
 
     MachineBasicBlock *MBB = Node->getBlock();
diff --git a/llvm/lib/CodeGen/MachineLICM.cpp b/llvm/lib/CodeGen/MachineLICM.cpp
index 98638b9..5e8a916 100644
--- a/llvm/lib/CodeGen/MachineLICM.cpp
+++ b/llvm/lib/CodeGen/MachineLICM.cpp
@@ -737,8 +737,7 @@ void MachineLICMBase::HoistOutOfLoop(MachineDomTreeNode *HeaderN) {
       continue;
 
     Scopes.push_back(Node);
-    const std::vector<MachineDomTreeNode*> &Children = Node->getChildren();
-    unsigned NumChildren = Children.size();
+    unsigned NumChildren = Node->getNumChildren();
 
     // Don't hoist things out of a large switch statement.  This often causes
     // code to be hoisted that wasn't going to be executed, and increases
@@ -747,13 +746,14 @@ void MachineLICMBase::HoistOutOfLoop(MachineDomTreeNode *HeaderN) {
       NumChildren = 0;
 
     OpenChildren[Node] = NumChildren;
-    // Add children in reverse order as then the next popped worklist node is
-    // the first child of this node.  This means we ultimately traverse the
-    // DOM tree in exactly the same order as if we'd recursed.
-    for (int i = (int)NumChildren-1; i >= 0; --i) {
-      MachineDomTreeNode *Child = Children[i];
-      ParentMap[Child] = Node;
-      WorkList.push_back(Child);
+    if (NumChildren) {
+      // Add children in reverse order as then the next popped worklist node is
+      // the first child of this node.  This means we ultimately traverse the
+      // DOM tree in exactly the same order as if we'd recursed.
+      for (MachineDomTreeNode *Child : reverse(Node->children())) {
+        ParentMap[Child] = Node;
+        WorkList.push_back(Child);
+      }
     }
   }
 
diff --git a/llvm/lib/CodeGen/MachineSink.cpp b/llvm/lib/CodeGen/MachineSink.cpp
index 1d253a6..5f958bb 100644
--- a/llvm/lib/CodeGen/MachineSink.cpp
+++ b/llvm/lib/CodeGen/MachineSink.cpp
@@ -623,14 +623,13 @@ MachineSinking::GetAllSortedSuccessors(MachineInstr &MI, MachineBasicBlock *MBB,
   //   if () {} else {}
   //   use x
   //
-  const std::vector<MachineDomTreeNode *> &Children =
-    DT->getNode(MBB)->getChildren();
-  for (const auto &DTChild : Children)
+  for (MachineDomTreeNode *DTChild : DT->getNode(MBB)->children()) {
     // DomTree children of MBB that have MBB as immediate dominator are added.
     if (DTChild->getIDom()->getBlock() == MI.getParent() &&
         // Skip MBBs already added to the AllSuccs vector above.
         !MBB->isSuccessor(DTChild->getBlock()))
       AllSuccs.push_back(DTChild->getBlock());
+  }
 
   // Sort Successors according to their loop depth or block frequency info.
   llvm::stable_sort(
diff --git a/llvm/lib/Target/AArch64/AArch64ConditionalCompares.cpp b/llvm/lib/Target/AArch64/AArch64ConditionalCompares.cpp
index 4613002..82e8df3 100644
--- a/llvm/lib/Target/AArch64/AArch64ConditionalCompares.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ConditionalCompares.cpp
@@ -828,7 +828,7 @@ void AArch64ConditionalCompares::updateDomTree(
     assert(Node != HeadNode && "Cannot erase the head node");
     assert(Node->getIDom() == HeadNode && "CmpBB should be dominated by Head");
     while (Node->getNumChildren())
-      DomTree->changeImmediateDominator(Node->getChildren().back(), HeadNode);
+      DomTree->changeImmediateDominator(Node->back(), HeadNode);
     DomTree->eraseNode(RemovedMBB);
   }
 }
diff --git a/llvm/lib/Target/Mips/MipsOptimizePICCall.cpp b/llvm/lib/Target/Mips/MipsOptimizePICCall.cpp
index 8bd64ff..2823d30 100644
--- a/llvm/lib/Target/Mips/MipsOptimizePICCall.cpp
+++ b/llvm/lib/Target/Mips/MipsOptimizePICCall.cpp
@@ -218,8 +218,7 @@ bool OptimizePICCall::runOnMachineFunction(MachineFunction &F) {
     MBBI.preVisit(ScopedHT);
     Changed |= visitNode(MBBI);
     const MachineDomTreeNode *Node = MBBI.getNode();
-    const std::vector<MachineDomTreeNode *> &Children = Node->getChildren();
-    WorkList.append(Children.begin(), Children.end());
+    WorkList.append(Node->begin(), Node->end());
   }
 
   return Changed;
diff --git a/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp b/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp
index fa3bc5f..7c14b69 100644
--- a/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp
+++ b/llvm/lib/Transforms/Scalar/ConstantHoisting.cpp
@@ -250,7 +250,7 @@ static void findBestInsertionSet(DominatorTree &DT, BlockFrequencyInfo &BFI,
   Orders.push_back(Entry);
   while (Idx != Orders.size()) {
     BasicBlock *Node = Orders[Idx++];
-    for (auto ChildDomNode : DT.getNode(Node)->getChildren()) {
+    for (auto ChildDomNode : DT.getNode(Node)->children()) {
       if (Candidates.count(ChildDomNode->getBlock()))
         Orders.push_back(ChildDomNode->getBlock());
     }
diff --git a/llvm/lib/Transforms/Scalar/NewGVN.cpp b/llvm/lib/Transforms/Scalar/NewGVN.cpp
index 576d40f..0ed1773 100644
--- a/llvm/lib/Transforms/Scalar/NewGVN.cpp
+++ b/llvm/lib/Transforms/Scalar/NewGVN.cpp
@@ -3436,7 +3436,7 @@ bool NewGVN::runGVN() {
   // Sort dominator tree children arrays into RPO.
   for (auto &B : RPOT) {
     auto *Node = DT->getNode(B);
-    if (Node->getChildren().size() > 1)
+    if (Node->getNumChildren() > 1)
       llvm::sort(Node->begin(), Node->end(),
                  [&](const DomTreeNode *A, const DomTreeNode *B) {
                    return RPOOrdering[A] < RPOOrdering[B];
diff --git a/llvm/lib/Transforms/Utils/LoopSimplify.cpp b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
index c33f36f..a8445e9 100644
--- a/llvm/lib/Transforms/Utils/LoopSimplify.cpp
+++ b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
@@ -696,10 +696,8 @@ ReprocessLoop:
       LI->removeBlock(ExitingBlock);
 
       DomTreeNode *Node = DT->getNode(ExitingBlock);
-      const std::vector<DomTreeNodeBase<BasicBlock> *> &Children =
-        Node->getChildren();
-      while (!Children.empty()) {
-        DomTreeNode *Child = Children.front();
+      while (!Node->isLeaf()) {
+        DomTreeNode *Child = Node->back();
         DT->changeImmediateDominator(Child, Node->getIDom());
       }
       DT->eraseNode(ExitingBlock);
diff --git a/llvm/lib/Transforms/Utils/LoopUnroll.cpp b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
index b86c62a..3875c63 100644
--- a/llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -809,7 +809,7 @@ LoopUnrollResult llvm::UnrollLoop(Loop *L, UnrollLoopOptions ULO, LoopInfo *LI,
     for (auto *BB : OriginalLoopBlocks) {
       auto *BBDomNode = DT->getNode(BB);
       SmallVector<BasicBlock *, 16> ChildrenToUpdate;
-      for (auto *ChildDomNode : BBDomNode->getChildren()) {
+      for (auto *ChildDomNode : BBDomNode->children()) {
         auto *ChildBB = ChildDomNode->getBlock();
         if (!L->contains(ChildBB))
           ChildrenToUpdate.push_back(ChildBB);
diff --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index c0d97cf..2515b16 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -848,7 +848,7 @@ bool llvm::UnrollRuntimeLoopRemainder(
     // dominator of the exit blocks.
     for (auto *BB : L->blocks()) {
       auto *DomNodeBB = DT->getNode(BB);
-      for (auto *DomChild : DomNodeBB->getChildren()) {
+      for (auto *DomChild : DomNodeBB->children()) {
         auto *DomChildBB = DomChild->getBlock();
         if (!L->contains(LI->getLoopFor(DomChildBB)))
           ChildrenToUpdate.push_back(DomChildBB);
diff --git a/llvm/lib/Transforms/Utils/LoopUtils.cpp b/llvm/lib/Transforms/Utils/LoopUtils.cpp
index 9241377..4336373 100644
--- a/llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -512,9 +512,10 @@ llvm::collectChildrenInLoop(DomTreeNode *N, const Loop *CurLoop) {
 
   AddRegionToWorklist(N);
 
-  for (size_t I = 0; I < Worklist.size(); I++)
-    for (DomTreeNode *Child : Worklist[I]->getChildren())
+  for (size_t I = 0; I < Worklist.size(); I++) {
+    for (DomTreeNode *Child : Worklist[I]->children())
       AddRegionToWorklist(Child);
+  }
 
   return Worklist;
 }