Make updateDFSNumbers API public

Summary:
There are a number of passes that could be sped up by using dominator tree DFS numbers to order or compare things across multiple bbs
(MemorySSA, MergedLoadStoreMotion, EarlyCSE, Sinking, GVN, NewGVN, for starters :P).

For example, GVN/CSE elimination can be done with a simple stack/etc (instead of full-on scoped hash table or repeated leader set walks)
  if the DFS pair is stored next to leaders.

The dominator tree keeps them, and the DOM tree nodes expose them as public, but you have no guarantee they are up to date (and in fact,
if you split blocks or whatever during your pass, they definitely won't be)

This means passes either have to compute their own versions[1], or make 32 queries, or ....
Rather than try to hide this, i just made the API public, and make it do nothing if the numbers are already valid.

[1] Which we want as a non-recursive walk, which is not pretty, sadly,
because it cannot use the depth first iterators since you don't get called on the way back up. So you either have to do one walk with po_iterator
and one with df_iterator, or write your own non-recursive walk that looks identical to the one in updateDFSNumbers.

Reviewers: chandlerc

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D8946

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234930 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Support/GenericDomTree.h b/include/llvm/Support/GenericDomTree.h
index 0998eb963255070419cde1a559bde8598f2bee10..5d11766ef44a52f7634bf6115bd23b7fb909e521 100644 (file)
--- a/include/llvm/Support/GenericDomTree.h
+++ b/include/llvm/Support/GenericDomTree.h
@@ -637,6 +637,29 @@ protected:
   friend void
   Calculate(DominatorTreeBase<typename GraphTraits<N>::NodeType> &DT, FuncT &F);
 
+
+  DomTreeNodeBase<NodeT> *getNodeForBlock(NodeT *BB) {
+    if (DomTreeNodeBase<NodeT> *Node = getNode(BB))
+      return Node;
+
+    // Haven't calculated this node yet?  Get or calculate the node for the
+    // immediate dominator.
+    NodeT *IDom = getIDom(BB);
+
+    assert(IDom || this->DomTreeNodes[nullptr]);
+    DomTreeNodeBase<NodeT> *IDomNode = getNodeForBlock(IDom);
+
+    // Add a new tree node for this NodeT, and link it as a child of
+    // IDomNode
+    return (this->DomTreeNodes[BB] = IDomNode->addChild(
+                llvm::make_unique<DomTreeNodeBase<NodeT>>(BB, IDomNode))).get();
+  }
+
+  NodeT *getIDom(NodeT *BB) const { return IDoms.lookup(BB); }
+
+  void addRoot(NodeT *BB) { this->Roots.push_back(BB); }
+
+public:
   /// updateDFSNumbers - Assign In and Out numbers to the nodes while walking
   /// dominator tree in dfs order.
   void updateDFSNumbers() const {
@@ -682,28 +705,6 @@ protected:
     DFSInfoValid = true;
   }
 
-  DomTreeNodeBase<NodeT> *getNodeForBlock(NodeT *BB) {
-    if (DomTreeNodeBase<NodeT> *Node = getNode(BB))
-      return Node;
-
-    // Haven't calculated this node yet?  Get or calculate the node for the
-    // immediate dominator.
-    NodeT *IDom = getIDom(BB);
-
-    assert(IDom || this->DomTreeNodes[nullptr]);
-    DomTreeNodeBase<NodeT> *IDomNode = getNodeForBlock(IDom);
-
-    // Add a new tree node for this NodeT, and link it as a child of
-    // IDomNode
-    return (this->DomTreeNodes[BB] = IDomNode->addChild(
-                llvm::make_unique<DomTreeNodeBase<NodeT>>(BB, IDomNode))).get();
-  }
-
-  NodeT *getIDom(NodeT *BB) const { return IDoms.lookup(BB); }
-
-  void addRoot(NodeT *BB) { this->Roots.push_back(BB); }
-
-public:
   /// recalculate - compute a dominator tree for the given function
   template <class FT> void recalculate(FT &F) {
     typedef GraphTraits<FT *> TraitsTy;