diff -r d050cc84f57d src/share/vm/opto/loopopts.cpp
--- a/src/share/vm/opto/loopopts.cpp	Tue Dec 01 16:21:13 2015 +0100
+++ b/src/share/vm/opto/loopopts.cpp	Tue Dec 01 17:55:00 2015 +0100
@@ -945,6 +945,13 @@
 }
 
 static bool merge_point_safe(Node* region) {
+  // 4799512: Stop split_if_with_blocks from splitting a block with a ConvI2LNode
+  // having a PhiNode input. This sidesteps the dangerous case where the split
+  // ConvI2LNode may become TOP if the input Value() does not
+  // overlap the ConvI2L range, leaving a node which may not dominate its
+  // uses.
+  // A better fix for this problem can be found in the BugTraq entry, but
+  // expediency for Mantis demands this hack.
   // 6855164: If the merge point has a FastLockNode with a PhiNode input, we stop
   // split_if_with_blocks from splitting a block because we could not move around
   // the FastLockNode.
@@ -955,6 +962,10 @@
         Node* m = n->fast_out(j);
         if (m->is_FastLock())
           return false;
+#ifdef _LP64
+        if (m->Opcode() == Op_ConvI2L)
+          return false;
+ #endif
       }
     }
   }