DomTree: add private create{Child,Node} helpers

Summary:
Aside from unifying the code a bit, this change smooths the
transition to use of future "opaque generic block references"
in the type-erased dominator tree base class.

Change-Id: If924b092cc8561c4b6a7450fe79bc96df0e12472

Reviewers: arsenm, RKSimon, mehdi_amini, courbet

Subscribers: wdng, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D83086

Author: nhaehnle

llvm/include/llvm/Support/GenericDomTree.h

@@ -590,8 +590,7 @@ class DominatorTreeBase {
     DomTreeNodeBase<NodeT> *IDomNode = getNode(DomBB);
     assert(IDomNode && "Not immediate dominator specified for block!");
     DFSInfoValid = false;
-    return (DomTreeNodes[BB] = IDomNode->addChild(
-                std::make_unique<DomTreeNodeBase<NodeT>>(BB, IDomNode))).get();
+    return createChild(BB, IDomNode);
   }
 
   /// Add a new node to the forward dominator tree and make it a new root.
@@ -604,8 +603,7 @@ class DominatorTreeBase {
     assert(!this->isPostDominator() &&
            "Cannot change root of post-dominator tree");
     DFSInfoValid = false;
-    DomTreeNodeBase<NodeT> *NewNode = (DomTreeNodes[BB] =
-      std::make_unique<DomTreeNodeBase<NodeT>>(BB, nullptr)).get();
+    DomTreeNodeBase<NodeT> *NewNode = createNode(BB);
     if (Roots.empty()) {
       addRoot(BB);
     } else {
@@ -786,6 +784,18 @@ class DominatorTreeBase {
 protected:
   void addRoot(NodeT *BB) { this->Roots.push_back(BB); }
 
+  DomTreeNodeBase<NodeT> *createChild(NodeT *BB, DomTreeNodeBase<NodeT> *IDom) {
+    return (DomTreeNodes[BB] = IDom->addChild(
+                std::make_unique<DomTreeNodeBase<NodeT>>(BB, IDom)))
+        .get();
+  }
+
+  DomTreeNodeBase<NodeT> *createNode(NodeT *BB) {
+    return (DomTreeNodes[BB] =
+                std::make_unique<DomTreeNodeBase<NodeT>>(BB, nullptr))
+        .get();
+  }
+
   // NewBB is split and now it has one successor. Update dominator tree to
   // reflect this change.
   template <class N>

llvm/include/llvm/Support/GenericDomTreeConstruction.h

@@ -187,9 +187,7 @@ struct SemiNCAInfo {
 
     // Add a new tree node for this NodeT, and link it as a child of
     // IDomNode
-    return (DT.DomTreeNodes[BB] = IDomNode->addChild(
-        std::make_unique<DomTreeNodeBase<NodeT>>(BB, IDomNode)))
-        .get();
+    return DT.createChild(BB, IDomNode);
   }
 
   static bool AlwaysDescend(NodePtr, NodePtr) { return true; }
@@ -587,9 +585,7 @@ struct SemiNCAInfo {
     // all real exits (including multiple exit blocks, infinite loops).
     NodePtr Root = IsPostDom ? nullptr : DT.Roots[0];
 
-    DT.RootNode = (DT.DomTreeNodes[Root] =
-                       std::make_unique<DomTreeNodeBase<NodeT>>(Root, nullptr))
-        .get();
+    DT.RootNode = DT.createNode(Root);
     SNCA.attachNewSubtree(DT, DT.RootNode);
   }
 
@@ -610,8 +606,7 @@ struct SemiNCAInfo {
 
       // Add a new tree node for this BasicBlock, and link it as a child of
       // IDomNode.
-      DT.DomTreeNodes[W] = IDomNode->addChild(
-          std::make_unique<DomTreeNodeBase<NodeT>>(W, IDomNode));
+      DT.createChild(W, IDomNode);
     }
   }
 
@@ -661,10 +656,7 @@ struct SemiNCAInfo {
 
       // The unreachable node becomes a new root -- a tree node for it.
       TreeNodePtr VirtualRoot = DT.getNode(nullptr);
-      FromTN =
-          (DT.DomTreeNodes[From] = VirtualRoot->addChild(
-               std::make_unique<DomTreeNodeBase<NodeT>>(From, VirtualRoot)))
-              .get();
+      FromTN = DT.createChild(From, VirtualRoot);
       DT.Roots.push_back(From);
     }