6990754: Use native memory and reference counting to implement SymbolTable

Move symbols from permgen into C heap and reference count them

Reviewed-by: never, acorn, jmasa, stefank

hotspot/src/share/vm/memory/iterator.hpp

@@ -290,6 +290,22 @@ public:
   virtual void do_tag(int tag) = 0;
 };
 
+class SymbolClosure : public StackObj {
+ public:
+  virtual void do_symbol(Symbol**) = 0;
+
+  // Clear LSB in symbol address; it can be set by CPSlot.
+  static Symbol* load_symbol(Symbol** p) {
+    return (Symbol*)(intptr_t(*p) & ~1);
+  }
+
+  // Store symbol, adjusting new pointer if the original pointer was adjusted
+  // (symbol references in constant pool slots have their LSB set to 1).
+  static void store_symbol(Symbol** p, Symbol* sym) {
+    *p = (Symbol*)(intptr_t(sym) | (intptr_t(*p) & 1));
+  }
+};
+
 #ifdef ASSERT
 // This class is used to flag phases of a collection that
 // can unload classes and which should override the