vendor/llvm/llvm-release_40-r292009

1 files changed, 34 insertions, 3 deletions

diff --git a/include/llvm/Support/GenericDomTree.h b/include/llvm/Support/GenericDomTree.h
index 07a53438085a0..6e6ee40016440 100644
--- a/include/llvm/Support/GenericDomTree.h
+++ b/include/llvm/Support/GenericDomTree.h
@@ -571,9 +571,15 @@ public:
   // API to update (Post)DominatorTree information based on modifications to
   // the CFG...
 
-  /// addNewBlock - Add a new node to the dominator tree information.  This
-  /// creates a new node as a child of DomBB dominator node,linking it into
-  /// the children list of the immediate dominator.
+  /// Add a new node to the dominator tree information.
+  ///
+  /// This creates a new node as a child of DomBB dominator node, linking it
+  /// into the children list of the immediate dominator.
+  ///
+  /// \param BB New node in CFG.
+  /// \param DomBB CFG node that is dominator for BB.
+  /// \returns New dominator tree node that represents new CFG node.
+  ///
   DomTreeNodeBase<NodeT> *addNewBlock(NodeT *BB, NodeT *DomBB) {
     assert(getNode(BB) == nullptr && "Block already in dominator tree!");
     DomTreeNodeBase<NodeT> *IDomNode = getNode(DomBB);
@@ -583,6 +589,31 @@ public:
                 llvm::make_unique<DomTreeNodeBase<NodeT>>(BB, IDomNode))).get();
   }
 
+  /// Add a new node to the forward dominator tree and make it a new root.
+  ///
+  /// \param BB New node in CFG.
+  /// \returns New dominator tree node that represents new CFG node.
+  ///
+  DomTreeNodeBase<NodeT> *setNewRoot(NodeT *BB) {
+    assert(getNode(BB) == nullptr && "Block already in dominator tree!");
+    assert(!this->isPostDominator() &&
+           "Cannot change root of post-dominator tree");
+    DFSInfoValid = false;
+    auto &Roots = DominatorBase<NodeT>::Roots;
+    DomTreeNodeBase<NodeT> *NewNode = (DomTreeNodes[BB] =
+      llvm::make_unique<DomTreeNodeBase<NodeT>>(BB, nullptr)).get();
+    if (Roots.empty()) {
+      addRoot(BB);
+    } else {
+      assert(Roots.size() == 1);
+      NodeT *OldRoot = Roots.front();
+      DomTreeNodes[OldRoot] =
+        NewNode->addChild(std::move(DomTreeNodes[OldRoot]));
+      Roots[0] = BB;
+    }
+    return RootNode = NewNode;
+  }
+
   /// changeImmediateDominator - This method is used to update the dominator
   /// tree information when a node's immediate dominator changes.
   ///