--- a/hotspot/src/share/vm/opto/compile.cpp	Fri May 02 09:30:17 2014 +0000
+++ b/hotspot/src/share/vm/opto/compile.cpp	Fri May 02 16:44:54 2014 -0700
@@ -704,6 +704,7 @@
 #endif
   set_print_inlining(PrintInlining || method()->has_option("PrintInlining") NOT_PRODUCT( || PrintOptoInlining));
   set_print_intrinsics(PrintIntrinsics || method()->has_option("PrintIntrinsics"));
+  set_has_irreducible_loop(true); // conservative until build_loop_tree() reset it
 
   if (ProfileTraps RTM_OPT_ONLY( || UseRTMLocking )) {
     // Make sure the method being compiled gets its own MDO,
@@ -988,6 +989,8 @@
   set_print_assembly(PrintFrameConverterAssembly);
   set_parsed_irreducible_loop(false);
 #endif
+  set_has_irreducible_loop(false); // no loops
+
   CompileWrapper cw(this);
   Init(/*AliasLevel=*/ 0);
   init_tf((*generator)());
@@ -1158,7 +1161,7 @@
     if( start->is_Start() )
       return start->as_Start();
   }
-  ShouldNotReachHere();
+  fatal("Did not find Start node!");
   return NULL;
 }
 

--- a/hotspot/src/share/vm/opto/compile.hpp	Fri May 02 09:30:17 2014 +0000
+++ b/hotspot/src/share/vm/opto/compile.hpp	Fri May 02 16:44:54 2014 -0700
@@ -319,6 +319,7 @@
   bool                  _trace_opto_output;
   bool                  _parsed_irreducible_loop; // True if ciTypeFlow detected irreducible loops during parsing
 #endif
+  bool                  _has_irreducible_loop;  // Found irreducible loops
   // JSR 292
   bool                  _has_method_handle_invokes; // True if this method has MethodHandle invokes.
   RTMState              _rtm_state;             // State of Restricted Transactional Memory usage
@@ -604,6 +605,8 @@
   void          set_parsed_irreducible_loop(bool z) { _parsed_irreducible_loop = z; }
   int _in_dump_cnt;  // Required for dumping ir nodes.
 #endif
+  bool              has_irreducible_loop() const { return _has_irreducible_loop; }
+  void          set_has_irreducible_loop(bool z) { _has_irreducible_loop = z; }
 
   // JSR 292
   bool              has_method_handle_invokes() const { return _has_method_handle_invokes;     }

--- a/hotspot/src/share/vm/opto/loopnode.cpp	Fri May 02 09:30:17 2014 +0000
+++ b/hotspot/src/share/vm/opto/loopnode.cpp	Fri May 02 16:44:54 2014 -0700
@@ -267,9 +267,9 @@
 
   // Counted loop head must be a good RegionNode with only 3 not NULL
   // control input edges: Self, Entry, LoopBack.
-  if (x->in(LoopNode::Self) == NULL || x->req() != 3)
+  if (x->in(LoopNode::Self) == NULL || x->req() != 3 || loop->_irreducible) {
     return false;
-
+  }
   Node *init_control = x->in(LoopNode::EntryControl);
   Node *back_control = x->in(LoopNode::LoopBackControl);
   if (init_control == NULL || back_control == NULL)    // Partially dead
@@ -1523,11 +1523,11 @@
 
   // If I have one hot backedge, peel off myself loop.
   // I better be the outermost loop.
-  if( _head->req() > 3 ) {
+  if (_head->req() > 3 && !_irreducible) {
     split_outer_loop( phase );
     result = true;
 
-  } else if( !_head->is_Loop() && !_irreducible ) {
+  } else if (!_head->is_Loop() && !_irreducible) {
     // Make a new LoopNode to replace the old loop head
     Node *l = new (phase->C) LoopNode( _head->in(1), _head->in(2) );
     l = igvn.register_new_node_with_optimizer(l, _head);
@@ -2939,6 +2939,7 @@
           return pre_order;
         }
       }
+      C->set_has_irreducible_loop(_has_irreducible_loops);
     }
 
     // This Node might be a decision point for loops.  It is only if

--- a/hotspot/src/share/vm/opto/memnode.cpp	Fri May 02 09:30:17 2014 +0000
+++ b/hotspot/src/share/vm/opto/memnode.cpp	Fri May 02 16:44:54 2014 -0700
@@ -308,33 +308,16 @@
     int alias_idx = phase->C->get_alias_index(t_adr->is_ptr());
   }
 
-#ifdef ASSERT
   Node* base = NULL;
-  if (address->is_AddP())
+  if (address->is_AddP()) {
     base = address->in(AddPNode::Base);
+  }
   if (base != NULL && phase->type(base)->higher_equal(TypePtr::NULL_PTR) &&
       !t_adr->isa_rawptr()) {
     // Note: raw address has TOP base and top->higher_equal(TypePtr::NULL_PTR) is true.
-    Compile* C = phase->C;
-    tty->cr();
-    tty->print_cr("===== NULL+offs not RAW address =====");
-    if (C->is_dead_node(this->_idx))    tty->print_cr("'this' is dead");
-    if ((ctl != NULL) && C->is_dead_node(ctl->_idx)) tty->print_cr("'ctl' is dead");
-    if (C->is_dead_node(mem->_idx))     tty->print_cr("'mem' is dead");
-    if (C->is_dead_node(address->_idx)) tty->print_cr("'address' is dead");
-    if (C->is_dead_node(base->_idx))    tty->print_cr("'base' is dead");
-    tty->cr();
-    base->dump(1);
-    tty->cr();
-    this->dump(2);
-    tty->print("this->adr_type():     "); adr_type()->dump(); tty->cr();
-    tty->print("phase->type(address): "); t_adr->dump(); tty->cr();
-    tty->print("phase->type(base):    "); phase->type(address)->dump(); tty->cr();
-    tty->cr();
+    // Skip this node optimization if its address has TOP base.
+    return NodeSentinel; // caller will return NULL
   }
-  assert(base == NULL || t_adr->isa_rawptr() ||
-        !phase->type(base)->higher_equal(TypePtr::NULL_PTR), "NULL+offs not RAW address?");
-#endif
 
   // Avoid independent memory operations
   Node* old_mem = mem;

--- a/hotspot/src/share/vm/opto/node.cpp	Fri May 02 09:30:17 2014 +0000
+++ b/hotspot/src/share/vm/opto/node.cpp	Fri May 02 16:44:54 2014 -0700
@@ -27,6 +27,7 @@
 #include "memory/allocation.inline.hpp"
 #include "opto/cfgnode.hpp"
 #include "opto/connode.hpp"
+#include "opto/loopnode.hpp"
 #include "opto/machnode.hpp"
 #include "opto/matcher.hpp"
 #include "opto/node.hpp"
@@ -1263,6 +1264,7 @@
 
   Node *top = igvn->C->top();
   nstack.push(dead);
+  bool has_irreducible_loop = igvn->C->has_irreducible_loop();
 
   while (nstack.size() > 0) {
     dead = nstack.pop();
@@ -1277,13 +1279,31 @@
           assert (!use->is_Con(), "Control for Con node should be Root node.");
           use->set_req(0, top);       // Cut dead edge to prevent processing
           nstack.push(use);           // the dead node again.
+        } else if (!has_irreducible_loop && // Backedge could be alive in irreducible loop
+                   use->is_Loop() && !use->is_Root() &&       // Don't kill Root (RootNode extends LoopNode)
+                   use->in(LoopNode::EntryControl) == dead) { // Dead loop if its entry is dead
+          use->set_req(LoopNode::EntryControl, top);          // Cut dead edge to prevent processing
+          use->set_req(0, top);       // Cut self edge
+          nstack.push(use);
         } else {                      // Else found a not-dead user
+          // Dead if all inputs are top or null
+          bool dead_use = !use->is_Root(); // Keep empty graph alive
           for (uint j = 1; j < use->req(); j++) {
-            if (use->in(j) == dead) { // Turn all dead inputs into TOP
+            Node* in = use->in(j);
+            if (in == dead) {         // Turn all dead inputs into TOP
               use->set_req(j, top);
+            } else if (in != NULL && !in->is_top()) {
+              dead_use = false;
             }
           }
-          igvn->_worklist.push(use);
+          if (dead_use) {
+            if (use->is_Region()) {
+              use->set_req(0, top);   // Cut self edge
+            }
+            nstack.push(use);
+          } else {
+            igvn->_worklist.push(use);
+          }
         }
         // Refresh the iterator, since any number of kills might have happened.
         k = dead->last_outs(kmin);