--- a/src/share/vm/oops/generateOopMap.cpp	Tue Mar 19 10:56:33 2013 -0700
+++ b/src/share/vm/oops/generateOopMap.cpp	Tue Mar 19 16:31:10 2013 -0700
@@ -762,6 +762,7 @@
 // monitor matching is purely informational and doesn't say anything
 // about the correctness of the code.
 void GenerateOopMap::merge_state_into_bb(BasicBlock *bb) {
+  guarantee(bb != NULL, "null basicblock");
   assert(bb->is_alive(), "merging state into a dead basicblock");
 
   if (_stack_top == bb->_stack_top) {
@@ -1189,6 +1190,7 @@
 
       if (start_pc <= bci && bci < end_pc) {
         BasicBlock *excBB = get_basic_block_at(handler_pc);
+        guarantee(excBB != NULL, "no basic block for exception");
         CellTypeState *excStk = excBB->stack();
         CellTypeState *cOpStck = stack();
         CellTypeState cOpStck_0 = cOpStck[0];
@@ -1803,6 +1805,7 @@
     // possibility that this bytecode will throw an
     // exception.
     BasicBlock* bb = get_basic_block_containing(bci);
+    guarantee(bb != NULL, "no basic block for bci");
     bb->set_changed(true);
     bb->_monitor_top = bad_monitors;
 
@@ -2190,6 +2193,7 @@
 
   // Find basicblock and report results
   BasicBlock* bb = get_basic_block_containing(bci);
+  guarantee(bb != NULL, "no basic block for bci");
   assert(bb->is_reachable(), "getting result from unreachable basicblock");
   bb->set_changed(true);
   interp_bb(bb);

--- a/src/share/vm/opto/loopnode.hpp	Tue Mar 19 10:56:33 2013 -0700
+++ b/src/share/vm/opto/loopnode.hpp	Tue Mar 19 16:31:10 2013 -0700
@@ -603,7 +603,10 @@
   }
 
 public:
-  bool has_node( Node* n ) const { return _nodes[n->_idx] != NULL; }
+  bool has_node( Node* n ) const {
+    guarantee(n != NULL, "No Node.");
+    return _nodes[n->_idx] != NULL;
+  }
   // check if transform created new nodes that need _ctrl recorded
   Node *get_late_ctrl( Node *n, Node *early );
   Node *get_early_ctrl( Node *n );
@@ -737,7 +740,8 @@
     return n;
   }
   uint dom_depth(Node* d) const {
-    assert(d->_idx < _idom_size, "");
+    guarantee(d != NULL, "Null dominator info.");
+    guarantee(d->_idx < _idom_size, "");
     return _dom_depth[d->_idx];
   }
   void set_idom(Node* d, Node* n, uint dom_depth);

--- a/src/share/vm/opto/loopopts.cpp	Tue Mar 19 10:56:33 2013 -0700
+++ b/src/share/vm/opto/loopopts.cpp	Tue Mar 19 16:31:10 2013 -0700
@@ -232,7 +232,11 @@
   // Loop predicates may have depending checks which should not
   // be skipped. For example, range check predicate has two checks
   // for lower and upper bounds.
-  ProjNode* unc_proj = iff->as_If()->proj_out(1 - dp->as_Proj()->_con)->as_Proj();
+  if (dp == NULL)
+    return;
+
+  ProjNode* dp_proj  = dp->as_Proj();
+  ProjNode* unc_proj = iff->as_If()->proj_out(1 - dp_proj->_con)->as_Proj();
   if (exclude_loop_predicate &&
       is_uncommon_trap_proj(unc_proj, Deoptimization::Reason_predicate))
     return; // Let IGVN transformation change control dependence.
@@ -866,8 +870,11 @@
 
     // Now split the bool up thru the phi
     Node *bolphi = split_thru_phi( bol, n_ctrl, -1 );
+    guarantee(bolphi != NULL, "null boolean phi node");
+
     _igvn.replace_node( bol, bolphi );
     assert( iff->in(1) == bolphi, "" );
+
     if( bolphi->Value(&_igvn)->singleton() )
       return;
 
@@ -1628,6 +1635,7 @@
 //------------------------------ short_circuit_if -------------------------------------
 // Force the iff control output to be the live_proj
 Node* PhaseIdealLoop::short_circuit_if(IfNode* iff, ProjNode* live_proj) {
+  guarantee(live_proj != NULL, "null projection");
   int proj_con = live_proj->_con;
   assert(proj_con == 0 || proj_con == 1, "false or true projection");
   Node *con = _igvn.intcon(proj_con);
@@ -1686,6 +1694,7 @@
   set_idom(proj, new_if, ddepth);
 
   ProjNode* new_exit = proj_clone(other_proj, new_if)->as_Proj();
+  guarantee(new_exit != NULL, "null exit node");
   register_node(new_exit, get_loop(other_proj), new_if, ddepth);
 
   return new_exit;
@@ -1793,7 +1802,10 @@
   int stride = stride_of_possible_iv(if_cmpu);
   if (stride == 0) return NULL;
 
-  ProjNode* lp_continue = stay_in_loop(if_cmpu, loop)->as_Proj();
+  Node* lp_proj = stay_in_loop(if_cmpu, loop);
+  guarantee(lp_proj != NULL, "null loop node");
+
+  ProjNode* lp_continue = lp_proj->as_Proj();
   ProjNode* lp_exit     = if_cmpu->proj_out(!lp_continue->is_IfTrue())->as_Proj();
 
   Node* limit = NULL;
@@ -1805,6 +1817,7 @@
   }
   // Create a new region on the exit path
   RegionNode* reg = insert_region_before_proj(lp_exit);
+  guarantee(reg != NULL, "null region node");
 
   // Clone the if-cmpu-true-false using a signed compare
   BoolTest::mask rel_i = stride > 0 ? bol->_test._test : BoolTest::ge;