8006280: Need to reorder metadata structures to reduce size (64-bit)

Summary: Reordered Klass, InstanceKlass and Method to save 8 bytes each
Reviewed-by: coleenp, jiangli
Contributed-by: ioi.lam@oracle.com

hotspot/src/share/vm/oops/instanceKlass.hpp

@@ -256,6 +256,16 @@ class InstanceKlass: public Klass {
   // JVMTI fields can be moved to their own structure - see 6315920
   unsigned char * _cached_class_file_bytes;       // JVMTI: cached class file, before retransformable agent modified it in CFLH
   jint            _cached_class_file_len;         // JVMTI: length of above
+
+  volatile u2     _idnum_allocated_count;         // JNI/JVMTI: increments with the addition of methods, old ids don't change
+
+  // Class states are defined as ClassState (see above).
+  // Place the _init_state here to utilize the unused 2-byte after
+  // _idnum_allocated_count.
+  u1              _init_state;                    // state of class
+  u1              _reference_type;                // reference type
+
+
   JvmtiCachedClassFieldMap* _jvmti_cached_class_field_map;  // JVMTI: used during heap iteration
 
   // Method array.
@@ -281,15 +291,6 @@ class InstanceKlass: public Klass {
   //     ...
   Array<u2>*      _fields;
 
-  volatile u2     _idnum_allocated_count;         // JNI/JVMTI: increments with the addition of methods, old ids don't change
-
-  // Class states are defined as ClassState (see above).
-  // Place the _init_state here to utilize the unused 2-byte after
-  // _idnum_allocated_count.
-  u1              _init_state;                    // state of class
-
-  u1              _reference_type;                // reference type
-
   // embedded Java vtable follows here
   // embedded Java itables follows here
   // embedded static fields follows here

hotspot/src/share/vm/oops/klass.hpp

@@ -75,11 +75,11 @@
 //    [class_loader_data]
 //    [modifier_flags]
 //    [access_flags  ]
-//    [verify_count  ] - not in product
-//    [alloc_count   ]
 //    [last_biased_lock_bulk_revocation_time] (64 bits)
 //    [prototype_header]
 //    [biased_lock_revocation_count]
+//    [verify_count  ] - not in product
+//    [alloc_count   ]
 //    [_modified_oops]
 //    [_accumulated_modified_oops]
 //    [trace_id]
@@ -164,18 +164,18 @@ class Klass : public Metadata {
   jint        _modifier_flags;  // Processed access flags, for use by Class.getModifiers.
   AccessFlags _access_flags;    // Access flags. The class/interface distinction is stored here.
 
-#ifndef PRODUCT
-  int           _verify_count;  // to avoid redundant verifies
-#endif
-
-  juint    _alloc_count;        // allocation profiling support
-
   // Biased locking implementation and statistics
   // (the 64-bit chunk goes first, to avoid some fragmentation)
   jlong    _last_biased_lock_bulk_revocation_time;
   markOop  _prototype_header;   // Used when biased locking is both enabled and disabled for this type
   jint     _biased_lock_revocation_count;
 
+#ifndef PRODUCT
+  int           _verify_count;  // to avoid redundant verifies
+#endif
+
+  juint    _alloc_count;        // allocation profiling support
+
   TRACE_DEFINE_KLASS_TRACE_ID;
 
   // Remembered sets support for the oops in the klasses.

hotspot/src/share/vm/oops/method.hpp

@@ -127,8 +127,8 @@ class Method : public Metadata {
   InvocationCounter _backedge_counter;           // Incremented before each backedge taken - used to trigger frequencey-based optimizations
 
 #ifdef TIERED
-  jlong             _prev_time;                   // Previous time the rate was acquired
   float             _rate;                        // Events (invocation and backedge counter increments) per millisecond
+  jlong             _prev_time;                   // Previous time the rate was acquired
 #endif
 
 #ifndef PRODUCT