switch the DomTreeNodes and IDoms maps in idom/postidom to a

DenseMap instead of an std::map.  This speeds up postdomtree
by about 25% and domtree by about 23%.  It also speeds up clients,
for example, domfrontier by 11%, mem2reg by 4% and ADCE by 6%.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40826 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 22 insertions, 20 deletions

diff --git a/lib/Analysis/PostDominators.cpp b/lib/Analysis/PostDominators.cpp
index 1188cff030..e3169a5c83 100644
--- a/lib/Analysis/PostDominators.cpp
+++ b/lib/Analysis/PostDominators.cpp
@@ -28,7 +28,7 @@ static RegisterPass<PostDominatorTree>
 F("postdomtree", "Post-Dominator Tree Construction", true);
 
 unsigned PostDominatorTree::DFSPass(BasicBlock *V, InfoRec &VInfo,
-                                          unsigned N) {
+                                    unsigned N) {
   std::vector<std::pair<BasicBlock *, InfoRec *> > workStack;
   std::set<BasicBlock *> visited;
   workStack.push_back(std::make_pair(V, &VInfo));
@@ -111,13 +111,18 @@ void PostDominatorTree::calculate(Function &F) {
   // Step #0: Scan the function looking for the root nodes of the post-dominance
   // relationships.  These blocks, which have no successors, end with return and
   // unwind instructions.
-  for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
-    if (succ_begin(I) == succ_end(I)) {
-      Instruction *Insn = I->getTerminator();
+  for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
+    TerminatorInst *Insn = I->getTerminator();
+    if (Insn->getNumSuccessors() == 0) {
       // Unreachable block is not a root node.
       if (!isa<UnreachableInst>(Insn))
         Roots.push_back(I);
     }
+    
+    // Prepopulate maps so that we don't get iterator invalidation issues later.
+    IDoms[I] = 0;
+    DomTreeNodes[I] = 0;
+  }
   
   Vertex.push_back(0);
   
diff --git a/lib/VMCore/Dominators.cpp b/lib/VMCore/Dominators.cpp
index 91b422c704..9b36e1de63 100644
--- a/lib/VMCore/Dominators.cpp
+++ b/lib/VMCore/Dominators.cpp
@@ -212,8 +212,7 @@ void DominatorTree::Compress(BasicBlock *VIn) {
 
   std::vector<BasicBlock *> Work;
   std::set<BasicBlock *> Visited;
-  InfoRec &VInInfo = Info[VIn];
-  BasicBlock *VInAncestor = VInInfo.Ancestor;
+  BasicBlock *VInAncestor = Info[VIn].Ancestor;
   InfoRec &VInVAInfo = Info[VInAncestor];
 
   if (VInVAInfo.Ancestor != 0)
@@ -233,7 +232,7 @@ void DominatorTree::Compress(BasicBlock *VIn) {
     } 
     Work.pop_back(); 
 
-    // Update VINfo based on Ancestor info
+    // Update VInfo based on Ancestor info
     if (VAInfo.Ancestor == 0)
       continue;
     BasicBlock *VAncestorLabel = VAInfo.Label;
@@ -366,17 +365,16 @@ void DominatorTree::calculate(Function& F) {
   // Loop over all of the reachable blocks in the function...
   for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
     if (BasicBlock *ImmDom = getIDom(I)) {  // Reachable block.
-      DomTreeNode *&BBNode = DomTreeNodes[I];
-      if (!BBNode) {  // Haven't calculated this node yet?
-        // Get or calculate the node for the immediate dominator
-        DomTreeNode *IDomNode = getNodeForBlock(ImmDom);
-
-        // Add a new tree node for this BasicBlock, and link it as a child of
-        // IDomNode
-        DomTreeNode *C = new DomTreeNode(I, IDomNode);
-        DomTreeNodes[I] = C;
-        BBNode = IDomNode->addChild(C);
-      }
+      DomTreeNode *BBNode = DomTreeNodes[I];
+      if (BBNode) continue;  // Haven't calculated this node yet?
+
+      // Get or calculate the node for the immediate dominator
+      DomTreeNode *IDomNode = getNodeForBlock(ImmDom);
+
+      // Add a new tree node for this BasicBlock, and link it as a child of
+      // IDomNode
+      DomTreeNode *C = new DomTreeNode(I, IDomNode);
+      DomTreeNodes[I] = IDomNode->addChild(C);
     }
 
   // Free temporary memory used to construct idom's
@@ -387,8 +385,7 @@ void DominatorTree::calculate(Function& F) {
   updateDFSNumbers();
 }
 
-void DominatorTreeBase::updateDFSNumbers()
-{
+void DominatorTreeBase::updateDFSNumbers() {
   int dfsnum = 0;
   // Iterate over all nodes in depth first order.
   for (unsigned i = 0, e = Roots.size(); i != e; ++i)