8006040: NPG: on_stack processing wastes space in ConstantPool

Added on_stack bit to flags.  Also MetadataMarkOnStack is used for more than JVMTI so had to be moved.

Reviewed-by: dholmes, stefank
diff --git a/hotspot/src/share/vm/oops/constantPool.hpp b/hotspot/src/share/vm/oops/constantPool.hpp
index 6554602..ea4b13f 100644
--- a/hotspot/src/share/vm/oops/constantPool.hpp
+++ b/hotspot/src/share/vm/oops/constantPool.hpp
@@ -95,10 +95,15 @@
   jobject              _resolved_references;
   Array<u2>*           _reference_map;
 
-  int                  _flags;         // a few header bits to describe contents for GC
-  int                  _length; // number of elements in the array
+  enum {
+    _has_invokedynamic = 1,           // Flags
+    _has_pseudo_string = 2,
+    _has_preresolution = 4,
+    _on_stack          = 8
+  };
 
-  bool                 _on_stack;     // Redefined method still executing refers to this constant pool.
+  int                  _flags;  // old fashioned bit twiddling
+  int                  _length; // number of elements in the array
 
   union {
     // set for CDS to restore resolved references
@@ -115,17 +120,8 @@
 
   void set_operands(Array<u2>* operands)       { _operands = operands; }
 
-  enum FlagBit {
-    FB_has_invokedynamic = 1,
-    FB_has_pseudo_string = 2,
-    FB_has_preresolution = 3
-  };
-
-  int flags() const                         { return _flags; }
-  void set_flags(int f)                     { _flags = f; }
-  bool flag_at(FlagBit fb) const            { return (_flags & (1 << (int)fb)) != 0; }
-  void set_flag_at(FlagBit fb);
-  // no clear_flag_at function; they only increase
+  int flags() const                            { return _flags; }
+  void set_flags(int f)                        { _flags = f; }
 
  private:
   intptr_t* base() const { return (intptr_t*) (((char*) this) + sizeof(ConstantPool)); }
@@ -178,18 +174,20 @@
   Array<u1>* tags() const                   { return _tags; }
   Array<u2>* operands() const               { return _operands; }
 
-  bool has_pseudo_string() const            { return flag_at(FB_has_pseudo_string); }
-  bool has_invokedynamic() const            { return flag_at(FB_has_invokedynamic); }
-  bool has_preresolution() const            { return flag_at(FB_has_preresolution); }
-  void set_pseudo_string()                  {    set_flag_at(FB_has_pseudo_string); }
-  void set_invokedynamic()                  {    set_flag_at(FB_has_invokedynamic); }
-  void set_preresolution()                  {    set_flag_at(FB_has_preresolution); }
+  bool has_invokedynamic() const            { return (_flags & _has_invokedynamic) != 0; }
+  void set_has_invokedynamic()              { _flags |= _has_invokedynamic; }
+
+  bool has_pseudo_string() const            { return (_flags & _has_pseudo_string) != 0; }
+  void set_has_pseudo_string()              { _flags |= _has_pseudo_string; }
+
+  bool has_preresolution() const            { return (_flags & _has_preresolution) != 0; }
+  void set_has_preresolution()              { _flags |= _has_preresolution; }
 
   // Redefine classes support.  If a method refering to this constant pool
   // is on the executing stack, or as a handle in vm code, this constant pool
   // can't be removed from the set of previous versions saved in the instance
   // class.
-  bool on_stack() const                     { return _on_stack; }
+  bool on_stack() const                      { return (_flags &_on_stack) != 0; }
   void set_on_stack(const bool value);
 
   // Klass holding pool
@@ -457,7 +455,7 @@
 
   void pseudo_string_at_put(int which, int obj_index, oop x) {
     assert(EnableInvokeDynamic, "");
-    set_pseudo_string();        // mark header
+    set_has_pseudo_string();        // mark header
     assert(tag_at(which).is_string(), "Corrupted constant pool");
     string_at_put(which, obj_index, x);    // this works just fine
   }