6681577: PIT: some VM tests fails with -XX:+AggressiveOpts in 6u5p b01

Summary: C2 spends > 60% in escape analysis code during test nsk/regression/b4675027.
Reviewed-by: never

src/share/vm/opto/escape.cpp

@@ -256,23 +256,35 @@ void ConnectionGraph::PointsTo(VectorSet &ptset, Node * n, PhaseTransform *phase
   }
 }
 
-void ConnectionGraph::remove_deferred(uint ni) {
-  VectorSet visited(Thread::current()->resource_area());
+void ConnectionGraph::remove_deferred(uint ni, GrowableArray<uint>* deferred_edges, VectorSet* visited) {
+  // This method is most expensive during ConnectionGraph construction.
+  // Reuse vectorSet and an additional growable array for deferred edges.
+  deferred_edges->clear();
+  visited->Clear();
 
   uint i = 0;
   PointsToNode *ptn = ptnode_adr(ni);
 
-  while(i < ptn->edge_count()) {
+  // Mark current edges as visited and move deferred edges to separate array.
+  for (; i < ptn->edge_count(); i++) {
     uint t = ptn->edge_target(i);
-    PointsToNode *ptt = ptnode_adr(t);
-    if (ptn->edge_type(i) != PointsToNode::DeferredEdge) {
-      i++;
-    } else {
+#ifdef ASSERT
+    assert(!visited->test_set(t), "expecting no duplications");
+#else
+    visited->set(t);
+#endif
+    if (ptn->edge_type(i) == PointsToNode::DeferredEdge) {
       ptn->remove_edge(t, PointsToNode::DeferredEdge);
-      if(!visited.test_set(t)) {
+      deferred_edges->append(t);
+    }
+  }
+  for (int next = 0; next < deferred_edges->length(); ++next) {
+    uint t = deferred_edges->at(next);
+    PointsToNode *ptt = ptnode_adr(t);
     for (uint j = 0; j < ptt->edge_count(); j++) {
       uint n1 = ptt->edge_target(j);
-          PointsToNode *pt1 = ptnode_adr(n1);
+      if (visited->test_set(n1))
+        continue;
       switch(ptt->edge_type(j)) {
         case PointsToNode::PointsToEdge:
           add_pointsto_edge(ni, n1);
@@ -282,7 +294,7 @@ void ConnectionGraph::remove_deferred(uint ni) {
           }
           break;
         case PointsToNode::DeferredEdge:
-              add_deferred_edge(ni, n1);
+          deferred_edges->append(n1);
           break;
         case PointsToNode::FieldEdge:
           assert(false, "invalid connection graph");
@@ -290,8 +302,6 @@ void ConnectionGraph::remove_deferred(uint ni) {
       }
     }
   }
-    }
-  }
 }
 
 
@@ -1238,6 +1248,8 @@ void ConnectionGraph::compute_escape() {
   VectorSet ptset(Thread::current()->resource_area());
   GrowableArray<Node*> alloc_worklist;
   GrowableArray<int>   worklist;
+  GrowableArray<uint>  deferred_edges;
+  VectorSet visited(Thread::current()->resource_area());
 
   // remove deferred edges from the graph and collect
   // information we will need for type splitting
@@ -1247,7 +1259,7 @@ void ConnectionGraph::compute_escape() {
     PointsToNode::NodeType nt = ptn->node_type();
     Node *n = ptn->_node;
     if (nt == PointsToNode::LocalVar || nt == PointsToNode::Field) {
-      remove_deferred(ni);
+      remove_deferred(ni, &deferred_edges, &visited);
       if (n->is_AddP()) {
         // If this AddP computes an address which may point to more that one
         // object, nothing the address points to can be scalar replaceable.

src/share/vm/opto/escape.hpp

@@ -269,7 +269,7 @@ private:
   // Remove outgoing deferred edges from the node referenced by "ni".
   // Any outgoing edges from the target of the deferred edge are copied
   // to "ni".
-  void remove_deferred(uint ni);
+  void remove_deferred(uint ni, GrowableArray<uint>* deferred_edges, VectorSet* visited);
 
   Node_Array _node_map; // used for bookeeping during type splitting
                         // Used for the following purposes: