--- a/src/share/vm/opto/locknode.cpp	Fri Feb 24 18:30:42 2012 -0800
+++ b/src/share/vm/opto/locknode.cpp	Mon Feb 27 13:10:13 2012 +0100
@@ -49,18 +49,22 @@
 
 //-----------------------------hash--------------------------------------------
 uint BoxLockNode::hash() const {
+  if (EliminateNestedLocks)
+    return NO_HASH; // Each locked region has own BoxLock node
   return Node::hash() + _slot + (_is_eliminated ? Compile::current()->fixed_slots() : 0);
 }
 
 //------------------------------cmp--------------------------------------------
 uint BoxLockNode::cmp( const Node &n ) const {
+  if (EliminateNestedLocks)
+    return (&n == this); // Always fail except on self
   const BoxLockNode &bn = (const BoxLockNode &)n;
   return bn._slot == _slot && bn._is_eliminated == _is_eliminated;
 }
 
-OptoReg::Name BoxLockNode::stack_slot(Node* box_node) {
-  // Chase down the BoxNode
-  while (!box_node->is_BoxLock()) {
+BoxLockNode* BoxLockNode::box_node(Node* box) {
+  // Chase down the BoxNode after RA which may spill box nodes.
+  while (!box->is_BoxLock()) {
     //    if (box_node->is_SpillCopy()) {
     //      Node *m = box_node->in(1);
     //      if (m->is_Mach() && m->as_Mach()->ideal_Opcode() == Op_StoreP) {
@@ -68,10 +72,64 @@
     //        continue;
     //      }
     //    }
-    assert(box_node->is_SpillCopy() || box_node->is_Phi(), "Bad spill of Lock.");
-    box_node = box_node->in(1);
+    assert(box->is_SpillCopy() || box->is_Phi(), "Bad spill of Lock.");
+    // Only BoxLock nodes with the same stack slot are merged.
+    // So it is enough to trace one path to find the slot value.
+    box = box->in(1);
   }
-  return box_node->in_RegMask(0).find_first_elem();
+  return box->as_BoxLock();
+}
+
+OptoReg::Name BoxLockNode::reg(Node* box) {
+  return box_node(box)->in_RegMask(0).find_first_elem();
+}
+
+// Is BoxLock node used for one simple lock region (same box and obj)?
+bool BoxLockNode::is_simple_lock_region(LockNode** unique_lock, Node* obj) {
+  LockNode* lock = NULL;
+  bool has_one_lock = false;
+  for (uint i = 0; i < this->outcnt(); i++) {
+    Node* n = this->raw_out(i);
+    assert(!n->is_Phi(), "should not merge BoxLock nodes");
+    if (n->is_AbstractLock()) {
+      AbstractLockNode* alock = n->as_AbstractLock();
+      // Check lock's box since box could be referenced by Lock's debug info.
+      if (alock->box_node() == this) {
+        if (alock->obj_node()->eqv_uncast(obj)) {
+          if ((unique_lock != NULL) && alock->is_Lock()) {
+            if (lock == NULL) {
+              lock = alock->as_Lock();
+              has_one_lock = true;
+            } else if (lock != alock->as_Lock()) {
+              has_one_lock = false;
+            }
+          }
+        } else {
+          return false; // Different objects
+        }
+      }
+    }
+  }
+#ifdef ASSERT
+  // Verify that FastLock and Safepoint reference only this lock region.
+  for (uint i = 0; i < this->outcnt(); i++) {
+    Node* n = this->raw_out(i);
+    if (n->is_FastLock()) {
+      FastLockNode* flock = n->as_FastLock();
+      assert((flock->box_node() == this) && flock->obj_node()->eqv_uncast(obj),"");
+    }
+    // Don't check monitor info in safepoints since the referenced object could
+    // be different from the locked object. It could be Phi node of different
+    // cast nodes which point to this locked object.
+    // We assume that no other objects could be referenced in monitor info
+    // associated with this BoxLock node because all associated locks and
+    // unlocks are reference only this one object.
+  }
+#endif
+  if (unique_lock != NULL && has_one_lock) {
+    *unique_lock = lock;
+  }
+  return true;
 }
 
 //=============================================================================