8175345: Reported null pointer dereference defect groups

Summary: Added required explicit NULL checks
Reviewed-by: thartmann, kvn

src/share/vm/opto/callnode.cpp

@@ -743,8 +743,8 @@ bool CallNode::may_modify(const TypeOopPtr *t_oop, PhaseTransform *phase) {
       }
       // May modify (by reflection) if an boxing object is passed
       // as argument or returned.
-      if (returns_pointer() && (proj_out(TypeFunc::Parms) != NULL)) {
-        Node* proj = proj_out(TypeFunc::Parms);
+      Node* proj = returns_pointer() ? proj_out(TypeFunc::Parms) : NULL;
+      if (proj != NULL) {
         const TypeInstPtr* inst_t = phase->type(proj)->isa_instptr();
         if ((inst_t != NULL) && (!inst_t->klass_is_exact() ||
                                  (inst_t->klass() == boxing_klass))) {

src/share/vm/opto/ifnode.cpp

@@ -1081,8 +1081,9 @@ void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) {
   // be skipped. For example, range check predicate has two checks
   // for lower and upper bounds.
   ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
-  if (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate))
+  if ((unc_proj != NULL) && (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate))) {
     prev_dom = idom;
+  }
 
   // Now walk the current IfNode's projections.
   // Loop ends when 'this' has no more uses.

src/share/vm/opto/loopTransform.cpp

@@ -2714,6 +2714,11 @@ bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) {
     return false;
   }
 
+  Node* exit = head->loopexit()->proj_out(0);
+  if (exit == NULL) {
+    return false;
+  }
+
 #ifndef PRODUCT
   if (TraceLoopOpts) {
     tty->print("ArrayFill    ");
@@ -2831,7 +2836,6 @@ bool PhaseIdealLoop::intrinsify_fill(IdealLoopTree* lpt) {
 */
 
   // Redirect the old control and memory edges that are outside the loop.
-  Node* exit = head->loopexit()->proj_out(0);
   // Sometimes the memory phi of the head is used as the outgoing
   // state of the loop.  It's safe in this case to replace it with the
   // result_mem.

src/share/vm/opto/stringopts.cpp

@@ -891,8 +891,9 @@ bool StringConcat::validate_control_flow() {
       ctrl_path.push(cn);
       ctrl_path.push(cn->proj_out(0));
       ctrl_path.push(cn->proj_out(0)->unique_out());
-      if (cn->proj_out(0)->unique_out()->as_Catch()->proj_out(0) != NULL) {
-        ctrl_path.push(cn->proj_out(0)->unique_out()->as_Catch()->proj_out(0));
+      Node* catchproj = cn->proj_out(0)->unique_out()->as_Catch()->proj_out(0);
+      if (catchproj != NULL) {
+        ctrl_path.push(catchproj);
       }
     } else {
       ShouldNotReachHere();