6712835: Server compiler fails with assertion (loop_count < K,"infinite loop in PhaseIterGVN::transform")

Reviewed-by: kvn

hotspot/src/share/vm/ci/ciMethodBlocks.cpp

@@ -351,7 +351,7 @@ void ciBlock::set_exception_range(int start_bci, int limit_bci)  {
 }
 
 #ifndef PRODUCT
-static char *flagnames[] = {
+static const char *flagnames[] = {
   "Processed",
   "Handler",
   "MayThrow",

hotspot/src/share/vm/opto/idealGraphPrinter.cpp

@@ -473,10 +473,12 @@ void IdealGraphPrinter::visit_node(Node *n, void *param) {
         print_prop("is_dontcare", "false");
       }
 
+#ifdef ASSERT
       Node* old = C->matcher()->find_old_node(node);
       if (old != NULL) {
         print_prop("old_node_idx", old->_idx);
       }
+#endif
     }
 
     if (node->is_Proj()) {

hotspot/src/share/vm/opto/ifnode.cpp

@@ -725,6 +725,11 @@ static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
   int true_path = phi->is_diamond_phi();
   if( true_path == 0 ) return NULL;
 
+  // Make sure that iff and the control of the phi are different. This
+  // should really only happen for dead control flow since it requires
+  // an illegal cycle.
+  if (phi->in(0)->in(1)->in(0) == iff) return NULL;
+
   // phi->region->if_proj->ifnode->bool->cmp
   BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
 
@@ -751,6 +756,7 @@ static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
   }
 
   Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
+  assert(new_bol != iff->in(1), "must make progress");
   iff->set_req(1, new_bol);
   // Intervening diamond probably goes dead
   phase->C->set_major_progress();