hotspot/src/share/vm/oops/oop.inline.hpp
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rev 611 : Merge
@@ -1,10 +1,10 @@
#ifdef USE_PRAGMA_IDENT_HDR
#pragma ident "@(#)oop.inline.hpp 1.142 07/09/25 16:47:44 JVM"
#endif
/*
- * Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved.
+ * Copyright 1997-2008 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
@@ -26,30 +26,81 @@
*/
// Implementation of all inlined member functions defined in oop.hpp
// We need a separate file to avoid circular references
-
inline void oopDesc::release_set_mark(markOop m) {
OrderAccess::release_store_ptr(&_mark, m);
}
inline markOop oopDesc::cas_set_mark(markOop new_mark, markOop old_mark) {
return (markOop) Atomic::cmpxchg_ptr(new_mark, &_mark, old_mark);
}
+inline klassOop oopDesc::klass() const {
+ if (UseCompressedOops) {
+ return (klassOop)decode_heap_oop_not_null(_metadata._compressed_klass);
+ } else {
+ return _metadata._klass;
+ }
+}
+
+inline klassOop oopDesc::klass_or_null() const volatile {
+ // can be NULL in CMS
+ if (UseCompressedOops) {
+ return (klassOop)decode_heap_oop(_metadata._compressed_klass);
+ } else {
+ return _metadata._klass;
+ }
+}
+
+inline int oopDesc::klass_gap_offset_in_bytes() {
+ assert(UseCompressedOops, "only applicable to compressed headers");
+ return oopDesc::klass_offset_in_bytes() + sizeof(narrowOop);
+}
+
+inline oop* oopDesc::klass_addr() {
+ // Only used internally and with CMS and will not work with
+ // UseCompressedOops
+ assert(!UseCompressedOops, "only supported with uncompressed oops");
+ return (oop*) &_metadata._klass;
+}
+
+inline narrowOop* oopDesc::compressed_klass_addr() {
+ assert(UseCompressedOops, "only called by compressed oops");
+ return (narrowOop*) &_metadata._compressed_klass;
+}
+
inline void oopDesc::set_klass(klassOop k) {
// since klasses are promoted no store check is needed
assert(Universe::is_bootstrapping() || k != NULL, "must be a real klassOop");
assert(Universe::is_bootstrapping() || k->is_klass(), "not a klassOop");
- oop_store_without_check((oop*) &_klass, (oop) k);
+ if (UseCompressedOops) {
+ oop_store_without_check(compressed_klass_addr(), (oop)k);
+ } else {
+ oop_store_without_check(klass_addr(), (oop) k);
+ }
+}
+
+inline int oopDesc::klass_gap() const {
+ return *(int*)(((intptr_t)this) + klass_gap_offset_in_bytes());
+}
+
+inline void oopDesc::set_klass_gap(int v) {
+ if (UseCompressedOops) {
+ *(int*)(((intptr_t)this) + klass_gap_offset_in_bytes()) = v;
+ }
}
inline void oopDesc::set_klass_to_list_ptr(oop k) {
// This is only to be used during GC, for from-space objects, so no
// barrier is needed.
- _klass = (klassOop)k;
+ if (UseCompressedOops) {
+ _metadata._compressed_klass = encode_heap_oop(k); // may be null (parnew overflow handling)
+ } else {
+ _metadata._klass = (klassOop)k;
+ }
}
inline void oopDesc::init_mark() { set_mark(markOopDesc::prototype_for_object(this)); }
inline Klass* oopDesc::blueprint() const { return klass()->klass_part(); }
@@ -71,22 +122,171 @@
inline bool oopDesc::is_constantPoolCache() const { return blueprint()->oop_is_constantPoolCache(); }
inline bool oopDesc::is_compiledICHolder() const { return blueprint()->oop_is_compiledICHolder(); }
inline void* oopDesc::field_base(int offset) const { return (void*)&((char*)this)[offset]; }
-inline oop* oopDesc::obj_field_addr(int offset) const { return (oop*) field_base(offset); }
+template <class T> inline T* oopDesc::obj_field_addr(int offset) const { return (T*)field_base(offset); }
inline jbyte* oopDesc::byte_field_addr(int offset) const { return (jbyte*) field_base(offset); }
inline jchar* oopDesc::char_field_addr(int offset) const { return (jchar*) field_base(offset); }
inline jboolean* oopDesc::bool_field_addr(int offset) const { return (jboolean*)field_base(offset); }
inline jint* oopDesc::int_field_addr(int offset) const { return (jint*) field_base(offset); }
inline jshort* oopDesc::short_field_addr(int offset) const { return (jshort*) field_base(offset); }
inline jlong* oopDesc::long_field_addr(int offset) const { return (jlong*) field_base(offset); }
inline jfloat* oopDesc::float_field_addr(int offset) const { return (jfloat*) field_base(offset); }
inline jdouble* oopDesc::double_field_addr(int offset) const { return (jdouble*) field_base(offset); }
+inline address* oopDesc::address_field_addr(int offset) const { return (address*) field_base(offset); }
+
+
+// Functions for getting and setting oops within instance objects.
+// If the oops are compressed, the type passed to these overloaded functions
+// is narrowOop. All functions are overloaded so they can be called by
+// template functions without conditionals (the compiler instantiates via
+// the right type and inlines the appopriate code).
+
+inline bool oopDesc::is_null(oop obj) { return obj == NULL; }
+inline bool oopDesc::is_null(narrowOop obj) { return obj == 0; }
+
+// Algorithm for encoding and decoding oops from 64 bit pointers to 32 bit
+// offset from the heap base. Saving the check for null can save instructions
+// in inner GC loops so these are separated.
+
+inline narrowOop oopDesc::encode_heap_oop_not_null(oop v) {
+ assert(!is_null(v), "oop value can never be zero");
+ address heap_base = Universe::heap_base();
+ uint64_t pd = (uint64_t)(pointer_delta((void*)v, (void*)heap_base, 1));
+ assert(OopEncodingHeapMax > pd, "change encoding max if new encoding");
+ uint64_t result = pd >> LogMinObjAlignmentInBytes;
+ assert((result & CONST64(0xffffffff00000000)) == 0, "narrow oop overflow");
+ return (narrowOop)result;
+}
+
+inline narrowOop oopDesc::encode_heap_oop(oop v) {
+ return (is_null(v)) ? (narrowOop)0 : encode_heap_oop_not_null(v);
+}
+
+inline oop oopDesc::decode_heap_oop_not_null(narrowOop v) {
+ assert(!is_null(v), "narrow oop value can never be zero");
+ address heap_base = Universe::heap_base();
+ return (oop)(void*)((uintptr_t)heap_base + ((uintptr_t)v << LogMinObjAlignmentInBytes));
+}
+
+inline oop oopDesc::decode_heap_oop(narrowOop v) {
+ return is_null(v) ? (oop)NULL : decode_heap_oop_not_null(v);
+}
+
+inline oop oopDesc::decode_heap_oop_not_null(oop v) { return v; }
+inline oop oopDesc::decode_heap_oop(oop v) { return v; }
+
+// Load an oop out of the Java heap as is without decoding.
+// Called by GC to check for null before decoding.
+inline oop oopDesc::load_heap_oop(oop* p) { return *p; }
+inline narrowOop oopDesc::load_heap_oop(narrowOop* p) { return *p; }
+
+// Load and decode an oop out of the Java heap into a wide oop.
+inline oop oopDesc::load_decode_heap_oop_not_null(oop* p) { return *p; }
+inline oop oopDesc::load_decode_heap_oop_not_null(narrowOop* p) {
+ return decode_heap_oop_not_null(*p);
+}
+
+// Load and decode an oop out of the heap accepting null
+inline oop oopDesc::load_decode_heap_oop(oop* p) { return *p; }
+inline oop oopDesc::load_decode_heap_oop(narrowOop* p) {
+ return decode_heap_oop(*p);
+}
+
+// Store already encoded heap oop into the heap.
+inline void oopDesc::store_heap_oop(oop* p, oop v) { *p = v; }
+inline void oopDesc::store_heap_oop(narrowOop* p, narrowOop v) { *p = v; }
+
+// Encode and store a heap oop.
+inline void oopDesc::encode_store_heap_oop_not_null(narrowOop* p, oop v) {
+ *p = encode_heap_oop_not_null(v);
+}
+inline void oopDesc::encode_store_heap_oop_not_null(oop* p, oop v) { *p = v; }
+
+// Encode and store a heap oop allowing for null.
+inline void oopDesc::encode_store_heap_oop(narrowOop* p, oop v) {
+ *p = encode_heap_oop(v);
+}
+inline void oopDesc::encode_store_heap_oop(oop* p, oop v) { *p = v; }
+
+// Store heap oop as is for volatile fields.
+inline void oopDesc::release_store_heap_oop(volatile oop* p, oop v) {
+ OrderAccess::release_store_ptr(p, v);
+}
+inline void oopDesc::release_store_heap_oop(volatile narrowOop* p,
+ narrowOop v) {
+ OrderAccess::release_store(p, v);
+}
+
+inline void oopDesc::release_encode_store_heap_oop_not_null(
+ volatile narrowOop* p, oop v) {
+ // heap oop is not pointer sized.
+ OrderAccess::release_store(p, encode_heap_oop_not_null(v));
+}
+
+inline void oopDesc::release_encode_store_heap_oop_not_null(
+ volatile oop* p, oop v) {
+ OrderAccess::release_store_ptr(p, v);
+}
+
+inline void oopDesc::release_encode_store_heap_oop(volatile oop* p,
+ oop v) {
+ OrderAccess::release_store_ptr(p, v);
+}
+inline void oopDesc::release_encode_store_heap_oop(
+ volatile narrowOop* p, oop v) {
+ OrderAccess::release_store(p, encode_heap_oop(v));
+}
+
+
+// These functions are only used to exchange oop fields in instances,
+// not headers.
+inline oop oopDesc::atomic_exchange_oop(oop exchange_value, volatile HeapWord *dest) {
+ if (UseCompressedOops) {
+ // encode exchange value from oop to T
+ narrowOop val = encode_heap_oop(exchange_value);
+ narrowOop old = (narrowOop)Atomic::xchg(val, (narrowOop*)dest);
+ // decode old from T to oop
+ return decode_heap_oop(old);
+ } else {
+ return (oop)Atomic::xchg_ptr(exchange_value, (oop*)dest);
+ }
+}
-inline oop oopDesc::obj_field(int offset) const { return *obj_field_addr(offset); }
-inline void oopDesc::obj_field_put(int offset, oop value) { oop_store(obj_field_addr(offset), value); }
+inline oop oopDesc::atomic_compare_exchange_oop(oop exchange_value,
+ volatile HeapWord *dest,
+ oop compare_value) {
+ if (UseCompressedOops) {
+ // encode exchange and compare value from oop to T
+ narrowOop val = encode_heap_oop(exchange_value);
+ narrowOop cmp = encode_heap_oop(compare_value);
+
+ narrowOop old = (narrowOop) Atomic::cmpxchg(val, (narrowOop*)dest, cmp);
+ // decode old from T to oop
+ return decode_heap_oop(old);
+ } else {
+ return (oop)Atomic::cmpxchg_ptr(exchange_value, (oop*)dest, compare_value);
+ }
+}
+
+// In order to put or get a field out of an instance, must first check
+// if the field has been compressed and uncompress it.
+inline oop oopDesc::obj_field(int offset) const {
+ return UseCompressedOops ?
+ load_decode_heap_oop(obj_field_addr<narrowOop>(offset)) :
+ load_decode_heap_oop(obj_field_addr<oop>(offset));
+}
+inline void oopDesc::obj_field_put(int offset, oop value) {
+ UseCompressedOops ? oop_store(obj_field_addr<narrowOop>(offset), value) :
+ oop_store(obj_field_addr<oop>(offset), value);
+}
+inline void oopDesc::obj_field_raw_put(int offset, oop value) {
+ UseCompressedOops ?
+ encode_store_heap_oop(obj_field_addr<narrowOop>(offset), value) :
+ encode_store_heap_oop(obj_field_addr<oop>(offset), value);
+}
inline jbyte oopDesc::byte_field(int offset) const { return (jbyte) *byte_field_addr(offset); }
inline void oopDesc::byte_field_put(int offset, jbyte contents) { *byte_field_addr(offset) = (jint) contents; }
inline jboolean oopDesc::bool_field(int offset) const { return (jboolean) *bool_field_addr(offset); }
@@ -108,12 +308,25 @@
inline void oopDesc::float_field_put(int offset, jfloat contents) { *float_field_addr(offset) = contents; }
inline jdouble oopDesc::double_field(int offset) const { return *double_field_addr(offset); }
inline void oopDesc::double_field_put(int offset, jdouble contents) { *double_field_addr(offset) = contents; }
-inline oop oopDesc::obj_field_acquire(int offset) const { return (oop)OrderAccess::load_ptr_acquire(obj_field_addr(offset)); }
-inline void oopDesc::release_obj_field_put(int offset, oop value) { oop_store((volatile oop*)obj_field_addr(offset), value); }
+inline address oopDesc::address_field(int offset) const { return *address_field_addr(offset); }
+inline void oopDesc::address_field_put(int offset, address contents) { *address_field_addr(offset) = contents; }
+
+inline oop oopDesc::obj_field_acquire(int offset) const {
+ return UseCompressedOops ?
+ decode_heap_oop((narrowOop)
+ OrderAccess::load_acquire(obj_field_addr<narrowOop>(offset)))
+ : decode_heap_oop((oop)
+ OrderAccess::load_ptr_acquire(obj_field_addr<oop>(offset)));
+}
+inline void oopDesc::release_obj_field_put(int offset, oop value) {
+ UseCompressedOops ?
+ oop_store((volatile narrowOop*)obj_field_addr<narrowOop>(offset), value) :
+ oop_store((volatile oop*) obj_field_addr<oop>(offset), value);
+}
inline jbyte oopDesc::byte_field_acquire(int offset) const { return OrderAccess::load_acquire(byte_field_addr(offset)); }
inline void oopDesc::release_byte_field_put(int offset, jbyte contents) { OrderAccess::release_store(byte_field_addr(offset), contents); }
inline jboolean oopDesc::bool_field_acquire(int offset) const { return OrderAccess::load_acquire(bool_field_addr(offset)); }
@@ -135,11 +348,10 @@
inline void oopDesc::release_float_field_put(int offset, jfloat contents) { OrderAccess::release_store(float_field_addr(offset), contents); }
inline jdouble oopDesc::double_field_acquire(int offset) const { return OrderAccess::load_acquire(double_field_addr(offset)); }
inline void oopDesc::release_double_field_put(int offset, jdouble contents) { OrderAccess::release_store(double_field_addr(offset), contents); }
-
inline int oopDesc::size_given_klass(Klass* klass) {
int lh = klass->layout_helper();
int s = lh >> LogHeapWordSize; // deliver size scaled by wordSize
// lh is now a value computed at class initialization that may hint
@@ -184,30 +396,29 @@
// skipping the intermediate round to HeapWordSize. Cast the result
// of round_to to size_t to guarantee unsigned division == right shift.
s = (int)((size_t)round_to(size_in_bytes, MinObjAlignmentInBytes) /
HeapWordSize);
- // UseParNewGC can change the length field of an "old copy" of an object
- // array in the young gen so it indicates the stealable portion of
- // an already copied array. This will cause the first disjunct below
- // to fail if the sizes are computed across such a concurrent change.
+ // UseParNewGC, UseParallelGC and UseG1GC can change the length field
+ // of an "old copy" of an object array in the young gen so it indicates
+ // the grey portion of an already copied array. This will cause the first
+ // disjunct below to fail if the two comparands are computed across such
+ // a concurrent change.
// UseParNewGC also runs with promotion labs (which look like int
// filler arrays) which are subject to changing their declared size
// when finally retiring a PLAB; this also can cause the first disjunct
// to fail for another worker thread that is concurrently walking the block
// offset table. Both these invariant failures are benign for their
// current uses; we relax the assertion checking to cover these two cases below:
// is_objArray() && is_forwarded() // covers first scenario above
// || is_typeArray() // covers second scenario above
// If and when UseParallelGC uses the same obj array oop stealing/chunking
- // technique, or when G1 is integrated (and currently uses this array chunking
- // technique) we will need to suitably modify the assertion.
+ // technique, we will need to suitably modify the assertion.
assert((s == klass->oop_size(this)) ||
- (((UseParNewGC || UseParallelGC) &&
- Universe::heap()->is_gc_active()) &&
- (is_typeArray() ||
- (is_objArray() && is_forwarded()))),
+ (Universe::heap()->is_gc_active() &&
+ ((is_typeArray() && UseParNewGC) ||
+ (is_objArray() && is_forwarded() && (UseParNewGC || UseParallelGC || UseG1GC)))),
"wrong array object size");
} else {
// Must be zero, so bite the bullet and take the virtual call.
s = klass->oop_size(this);
}
@@ -225,56 +436,68 @@
inline bool oopDesc::is_parsable() {
return blueprint()->oop_is_parsable(this);
}
-
-inline void update_barrier_set(oop *p, oop v) {
+inline void update_barrier_set(void* p, oop v) {
assert(oopDesc::bs() != NULL, "Uninitialized bs in oop!");
oopDesc::bs()->write_ref_field(p, v);
}
+inline void update_barrier_set_pre(void* p, oop v) {
+ oopDesc::bs()->write_ref_field_pre(p, v);
+}
-inline void oop_store(oop* p, oop v) {
+template <class T> inline void oop_store(T* p, oop v) {
if (always_do_update_barrier) {
- oop_store((volatile oop*)p, v);
+ oop_store((volatile T*)p, v);
} else {
- *p = v;
+ update_barrier_set_pre(p, v);
+ oopDesc::encode_store_heap_oop(p, v);
update_barrier_set(p, v);
}
}
-inline void oop_store(volatile oop* p, oop v) {
+template <class T> inline void oop_store(volatile T* p, oop v) {
+ update_barrier_set_pre((void*)p, v);
// Used by release_obj_field_put, so use release_store_ptr.
- OrderAccess::release_store_ptr(p, v);
- update_barrier_set((oop *)p, v);
+ oopDesc::release_encode_store_heap_oop(p, v);
+ update_barrier_set((void*)p, v);
}
-inline void oop_store_without_check(oop* p, oop v) {
+template <class T> inline void oop_store_without_check(T* p, oop v) {
// XXX YSR FIX ME!!!
if (always_do_update_barrier) {
oop_store(p, v);
} else {
assert(!Universe::heap()->barrier_set()->write_ref_needs_barrier(p, v),
"oop store without store check failed");
- *p = v;
+ oopDesc::encode_store_heap_oop(p, v);
}
}
// When it absolutely has to get there.
-inline void oop_store_without_check(volatile oop* p, oop v) {
+template <class T> inline void oop_store_without_check(volatile T* p, oop v) {
// XXX YSR FIX ME!!!
if (always_do_update_barrier) {
oop_store(p, v);
} else {
- assert(!Universe::heap()->barrier_set()->
- write_ref_needs_barrier((oop *)p, v),
+ assert(!Universe::heap()->barrier_set()->write_ref_needs_barrier((T*)p, v),
"oop store without store check failed");
- OrderAccess::release_store_ptr(p, v);
+ oopDesc::release_encode_store_heap_oop(p, v);
}
}
+// Should replace *addr = oop assignments where addr type depends on UseCompressedOops
+// (without having to remember the function name this calls).
+inline void oop_store_raw(HeapWord* addr, oop value) {
+ if (UseCompressedOops) {
+ oopDesc::encode_store_heap_oop((narrowOop*)addr, value);
+ } else {
+ oopDesc::encode_store_heap_oop((oop*)addr, value);
+ }
+}
// Used only for markSweep, scavenging
inline bool oopDesc::is_gc_marked() const {
return mark()->is_marked();
}
@@ -303,11 +526,11 @@
if (!Universe::heap()->is_in_reserved(obj)) return false;
// obj is aligned and accessible in heap
// try to find metaclass cycle safely without seg faulting on bad input
// we should reach klassKlassObj by following klass link at most 3 times
for (int i = 0; i < 3; i++) {
- obj = obj->klass();
+ obj = obj->klass_or_null();
// klass should be aligned and in permspace
if (!check_obj_alignment(obj)) return false;
if (!Universe::heap()->is_in_permanent(obj)) return false;
}
if (obj != Universe::klassKlassObj()) {
@@ -341,19 +564,21 @@
// used only for asserts
inline bool oopDesc::is_unlocked_oop() const {
if (!Universe::heap()->is_in_reserved(this)) return false;
return mark()->is_unlocked();
}
-
-
#endif // PRODUCT
inline void oopDesc::follow_header() {
- MarkSweep::mark_and_push((oop*)&_klass);
+ if (UseCompressedOops) {
+ MarkSweep::mark_and_push(compressed_klass_addr());
+ } else {
+ MarkSweep::mark_and_push(klass_addr());
+ }
}
-inline void oopDesc::follow_contents() {
+inline void oopDesc::follow_contents(void) {
assert (is_gc_marked(), "should be marked");
blueprint()->oop_follow_contents(this);
}
@@ -363,11 +588,10 @@
// The extra heap check is needed since the obj might be locked, in which case the
// mark would point to a stack location and have the sentinel bit cleared
return mark()->is_marked();
}
-
// Used by scavengers
inline void oopDesc::forward_to(oop p) {
assert(Universe::heap()->is_in_reserved(p),
"forwarding to something not in heap");
markOop m = markOopDesc::encode_pointer_as_mark(p);
@@ -385,12 +609,13 @@
}
// Note that the forwardee is not the same thing as the displaced_mark.
// The forwardee is used when copying during scavenge and mark-sweep.
// It does need to clear the low two locking- and GC-related bits.
-inline oop oopDesc::forwardee() const { return (oop) mark()->decode_pointer(); }
-
+inline oop oopDesc::forwardee() const {
+ return (oop) mark()->decode_pointer();
+}
inline bool oopDesc::has_displaced_mark() const {
return mark()->has_displaced_mark_helper();
}
@@ -433,30 +658,41 @@
} else {
return slow_identity_hash();
}
}
-
inline void oopDesc::oop_iterate_header(OopClosure* blk) {
- blk->do_oop((oop*)&_klass);
+ if (UseCompressedOops) {
+ blk->do_oop(compressed_klass_addr());
+ } else {
+ blk->do_oop(klass_addr());
+ }
}
-
inline void oopDesc::oop_iterate_header(OopClosure* blk, MemRegion mr) {
- if (mr.contains(&_klass)) blk->do_oop((oop*)&_klass);
+ if (UseCompressedOops) {
+ if (mr.contains(compressed_klass_addr())) {
+ blk->do_oop(compressed_klass_addr());
+ }
+ } else {
+ if (mr.contains(klass_addr())) blk->do_oop(klass_addr());
+ }
}
-
inline int oopDesc::adjust_pointers() {
debug_only(int check_size = size());
int s = blueprint()->oop_adjust_pointers(this);
assert(s == check_size, "should be the same");
return s;
}
inline void oopDesc::adjust_header() {
- MarkSweep::adjust_pointer((oop*)&_klass);
+ if (UseCompressedOops) {
+ MarkSweep::adjust_pointer(compressed_klass_addr());
+ } else {
+ MarkSweep::adjust_pointer(klass_addr());
+ }
}
#define OOP_ITERATE_DEFN(OopClosureType, nv_suffix) \
\
inline int oopDesc::oop_iterate(OopClosureType* blk) { \
@@ -468,12 +704,23 @@
SpecializationStats::record_call(); \
return blueprint()->oop_oop_iterate##nv_suffix##_m(this, blk, mr); \
}
ALL_OOP_OOP_ITERATE_CLOSURES_1(OOP_ITERATE_DEFN)
-ALL_OOP_OOP_ITERATE_CLOSURES_3(OOP_ITERATE_DEFN)
+ALL_OOP_OOP_ITERATE_CLOSURES_2(OOP_ITERATE_DEFN)
+
+#ifndef SERIALGC
+#define OOP_ITERATE_BACKWARDS_DEFN(OopClosureType, nv_suffix) \
+ \
+inline int oopDesc::oop_iterate_backwards(OopClosureType* blk) { \
+ SpecializationStats::record_call(); \
+ return blueprint()->oop_oop_iterate_backwards##nv_suffix(this, blk); \
+}
+ALL_OOP_OOP_ITERATE_CLOSURES_1(OOP_ITERATE_BACKWARDS_DEFN)
+ALL_OOP_OOP_ITERATE_CLOSURES_2(OOP_ITERATE_BACKWARDS_DEFN)
+#endif // !SERIALGC
inline bool oopDesc::is_shared() const {
return CompactingPermGenGen::is_shared(this);
}