7102776: Pack instanceKlass boolean fields into single u1 field

Summary: Reduce class runtime memory usage by packing 4 instanceKlass boolean fields into single u1 field. Save 4-byte for each loaded class.
Reviewed-by: dholmes, bobv, phh, twisti, never, coleenp
Contributed-by: NJiangli Zhou <jiangli.zhou@oracle.com>

agent/src/share/classes/sun/jvm/hotspot/oops/InstanceKlass.java

@@ -63,6 +63,8 @@ public class InstanceKlass extends Klass {
   private static int CLASS_STATE_FULLY_INITIALIZED;
   private static int CLASS_STATE_INITIALIZATION_ERROR;
 
+  private static int IS_MARKED_DEPENDENT_MASK;
+
   private static synchronized void initialize(TypeDataBase db) throws WrongTypeException {
     Type type            = db.lookupType("instanceKlass");
     arrayKlasses         = new OopField(type.getOopField("_array_klasses"), Oop.getHeaderSize());
@@ -90,7 +92,7 @@ public class InstanceKlass extends Klass {
     staticFieldSize      = new CIntField(type.getCIntegerField("_static_field_size"), Oop.getHeaderSize());
     staticOopFieldCount   = new CIntField(type.getCIntegerField("_static_oop_field_count"), Oop.getHeaderSize());
     nonstaticOopMapSize  = new CIntField(type.getCIntegerField("_nonstatic_oop_map_size"), Oop.getHeaderSize());
-    isMarkedDependent    = new CIntField(type.getCIntegerField("_is_marked_dependent"), Oop.getHeaderSize());
+    miscFlags            = new CIntField(type.getCIntegerField("_misc_flags"), Oop.getHeaderSize());
     initState            = new CIntField(type.getCIntegerField("_init_state"), Oop.getHeaderSize());
     vtableLen            = new CIntField(type.getCIntegerField("_vtable_len"), Oop.getHeaderSize());
     itableLen            = new CIntField(type.getCIntegerField("_itable_len"), Oop.getHeaderSize());
@@ -118,6 +120,8 @@ public class InstanceKlass extends Klass {
     CLASS_STATE_FULLY_INITIALIZED = db.lookupIntConstant("instanceKlass::fully_initialized").intValue();
     CLASS_STATE_INITIALIZATION_ERROR = db.lookupIntConstant("instanceKlass::initialization_error").intValue();
 
+    IS_MARKED_DEPENDENT_MASK = db.lookupIntConstant("instanceKlass::IS_MARKED_DEPENDENT").intValue();
+
   }
 
   InstanceKlass(OopHandle handle, ObjectHeap heap) {
@@ -151,7 +155,7 @@ public class InstanceKlass extends Klass {
   private static CIntField staticFieldSize;
   private static CIntField staticOopFieldCount;
   private static CIntField nonstaticOopMapSize;
-  private static CIntField isMarkedDependent;
+  private static CIntField miscFlags;
   private static CIntField initState;
   private static CIntField vtableLen;
   private static CIntField itableLen;
@@ -333,7 +337,7 @@ public class InstanceKlass extends Klass {
   public long      getNonstaticFieldSize()  { return                nonstaticFieldSize.getValue(this); }
   public long      getStaticOopFieldCount() { return                staticOopFieldCount.getValue(this); }
   public long      getNonstaticOopMapSize() { return                nonstaticOopMapSize.getValue(this); }
-  public boolean   getIsMarkedDependent()   { return                isMarkedDependent.getValue(this) != 0; }
+  public boolean   getIsMarkedDependent()   { return                (miscFlags.getValue(this) & IS_MARKED_DEPENDENT_MASK) != 0; }
   public long      getVtableLen()           { return                vtableLen.getValue(this); }
   public long      getItableLen()           { return                itableLen.getValue(this); }
   public Symbol    getGenericSignature()    { return getSymbol(genericSignature); }
@@ -524,7 +528,7 @@ public class InstanceKlass extends Klass {
       visitor.doCInt(staticFieldSize, true);
       visitor.doCInt(staticOopFieldCount, true);
       visitor.doCInt(nonstaticOopMapSize, true);
-      visitor.doCInt(isMarkedDependent, true);
+      visitor.doCInt(miscFlags, true);
       visitor.doCInt(initState, true);
       visitor.doCInt(vtableLen, true);
       visitor.doCInt(itableLen, true);

src/share/vm/code/dependencies.cpp

@@ -1624,7 +1624,7 @@ void KlassDepChange::initialize() {
   for (ContextStream str(*this); str.next(); ) {
     klassOop d = str.klass();
     assert(!instanceKlass::cast(d)->is_marked_dependent(), "checking");
-    instanceKlass::cast(d)->set_is_marked_dependent(true);
+    instanceKlass::cast(d)->set_is_marked_dependent();
   }
 }
 
@@ -1633,7 +1633,7 @@ KlassDepChange::~KlassDepChange() {
   // Unmark transitive interfaces
   for (ContextStream str(*this); str.next(); ) {
     klassOop d = str.klass();
-    instanceKlass::cast(d)->set_is_marked_dependent(false);
+    instanceKlass::cast(d)->clear_is_marked_dependent();
   }
 }
 

src/share/vm/oops/instanceKlass.hpp

@@ -230,10 +230,7 @@ class instanceKlass: public Klass {
   int             _static_oop_field_count;// number of static oop fields in this klass
   int             _nonstatic_oop_map_size;// size in words of nonstatic oop map blocks
   int             _java_fields_count;    // The number of declared Java fields
-  bool            _is_marked_dependent;  // used for marking during flushing and deoptimization
-  bool            _rewritten;            // methods rewritten.
-  bool            _has_nonstatic_fields; // for sizing with UseCompressedOops
-  bool            _should_verify_class;  // allow caching of preverification
+
   u2              _minor_version;        // minor version number of class file
   u2              _major_version;        // major version number of class file
   ClassState      _init_state;           // state of class
@@ -260,6 +257,19 @@ class instanceKlass: public Klass {
   JvmtiCachedClassFieldMap* _jvmti_cached_class_field_map;  // JVMTI: used during heap iteration
   volatile u2     _idnum_allocated_count;         // JNI/JVMTI: increments with the addition of methods, old ids don't change
 
+  // Compact the following four boolean flags into 1-bit each.  These four flags
+  // were defined as separate boolean fields and each was 1-byte before. Since
+  // there are 2 bytes unused after the _idnum_allocated_count field, place the
+  // _misc_flags field after _idnum_allocated_count to utilize the unused bits
+  // and save total 4-bytes.
+  enum {
+    IS_MARKED_DEPENDENT  = 0x1, // used for marking during flushing and deoptimization
+    REWRITTEN            = 0x2, // methods rewritten.
+    HAS_NONSTATIC_FIELDS = 0x4, // for sizing with UseCompressedOops
+    SHOULD_VERIFY_CLASS  = 0x8  // allow caching of preverification
+  };
+  u1              _misc_flags;
+
   // embedded Java vtable follows here
   // embedded Java itables follows here
   // embedded static fields follows here
@@ -269,8 +279,14 @@ class instanceKlass: public Klass {
   friend class SystemDictionary;
 
  public:
-  bool has_nonstatic_fields() const        { return _has_nonstatic_fields; }
-  void set_has_nonstatic_fields(bool b)    { _has_nonstatic_fields = b; }
+  bool has_nonstatic_fields() const        { return (_misc_flags & HAS_NONSTATIC_FIELDS) != 0; }
+  void set_has_nonstatic_fields(bool b) {
+    if (b) {
+      _misc_flags |= HAS_NONSTATIC_FIELDS;
+    } else {
+      _misc_flags &= ~HAS_NONSTATIC_FIELDS;
+    }
+  }
 
   // field sizes
   int nonstatic_field_size() const         { return _nonstatic_field_size; }
@@ -378,15 +394,23 @@ class instanceKlass: public Klass {
   bool is_in_error_state() const           { return _init_state == initialization_error; }
   bool is_reentrant_initialization(Thread *thread)  { return thread == _init_thread; }
   int  get_init_state()                    { return _init_state; } // Useful for debugging
-  bool is_rewritten() const                { return _rewritten; }
+  bool is_rewritten() const                { return (_misc_flags & REWRITTEN) != 0; }
 
   // defineClass specified verification
-  bool should_verify_class() const         { return _should_verify_class; }
-  void set_should_verify_class(bool value) { _should_verify_class = value; }
+  bool should_verify_class() const         { return (_misc_flags & SHOULD_VERIFY_CLASS) != 0; }
+  void set_should_verify_class(bool value) {
+    if (value) {
+      _misc_flags |= SHOULD_VERIFY_CLASS;
+    } else {
+      _misc_flags &= ~SHOULD_VERIFY_CLASS;
+    }
+  }
+
 
   // marking
-  bool is_marked_dependent() const         { return _is_marked_dependent; }
-  void set_is_marked_dependent(bool value) { _is_marked_dependent = value; }
+  bool is_marked_dependent() const         { return (_misc_flags & IS_MARKED_DEPENDENT) != 0; }
+  void set_is_marked_dependent()           { _misc_flags |= IS_MARKED_DEPENDENT; }
+  void clear_is_marked_dependent()         { _misc_flags &= ~IS_MARKED_DEPENDENT; }
 
   // initialization (virtuals from Klass)
   bool should_be_initialized() const;  // means that initialize should be called
@@ -756,7 +780,7 @@ private:
 #else
   void set_init_state(ClassState state) { _init_state = state; }
 #endif
-  void set_rewritten()                  { _rewritten = true; }
+  void set_rewritten()                  { _misc_flags |= REWRITTEN; }
   void set_init_thread(Thread *thread)  { _init_thread = thread; }
 
   u2 idnum_allocated_count() const      { return _idnum_allocated_count; }

src/share/vm/oops/instanceKlassKlass.cpp

@@ -399,7 +399,7 @@ instanceKlassKlass::allocate_instance_klass(Symbol* name, int vtable_len, int it
     ik->set_inner_classes(NULL);
     ik->set_static_oop_field_count(0);
     ik->set_nonstatic_field_size(0);
-    ik->set_is_marked_dependent(false);
+    ik->clear_is_marked_dependent();
     ik->set_init_state(instanceKlass::allocated);
     ik->set_init_thread(NULL);
     ik->set_reference_type(rt);

src/share/vm/runtime/vmStructs.cpp

@@ -307,7 +307,7 @@ static inline uint64_t cast_uint64_t(size_t x)
   nonstatic_field(instanceKlass,               _static_field_size,                            int)                                   \
   nonstatic_field(instanceKlass,               _static_oop_field_count,                       int)                                   \
   nonstatic_field(instanceKlass,               _nonstatic_oop_map_size,                       int)                                   \
-  nonstatic_field(instanceKlass,               _is_marked_dependent,                          bool)                                  \
+  nonstatic_field(instanceKlass,               _misc_flags,                                   u1)                                    \
   nonstatic_field(instanceKlass,               _minor_version,                                u2)                                    \
   nonstatic_field(instanceKlass,               _major_version,                                u2)                                    \
   nonstatic_field(instanceKlass,               _init_state,                                   instanceKlass::ClassState)             \
@@ -1362,6 +1362,7 @@ static inline uint64_t cast_uint64_t(size_t x)
   /* The compiler thinks this is a different type than */                 \
   /* unsigned short on Win32 */                                           \
   declare_unsigned_integer_type(u2)                                       \
+  declare_unsigned_integer_type(u1)                                       \
   declare_unsigned_integer_type(unsigned)                                 \
                                                                           \
   /*****************************/                                         \
@@ -2385,6 +2386,7 @@ static inline uint64_t cast_uint64_t(size_t x)
   declare_constant(instanceKlass::being_initialized)                      \
   declare_constant(instanceKlass::fully_initialized)                      \
   declare_constant(instanceKlass::initialization_error)                   \
+  declare_constant(instanceKlass::IS_MARKED_DEPENDENT)                    \
                                                                           \
   /*********************************/                                     \
   /* Symbol* - symbol max length */                                     \