inline void oopDesc::incr_age() {
assert(!is_forwarded(), "Attempt to increment age of forwarded mark");
if (has_displaced_mark()) {
set_displaced_mark(displaced_mark()->incr_age());
} else {
set_mark(mark()->incr_age());
}
}
// The following method needs to be MT safe.
inline int oopDesc::age() const {
assert(!is_forwarded(), "Attempt to read age from forwarded mark");
if (has_displaced_mark()) {
return displaced_mark()->age();
} else {
return mark()->age();
}
}
inline oop oopDesc::forward_to_atomic(oop p) {
assert(ParNewGeneration::is_legal_forward_ptr(p),
"illegal forwarding pointer value.");
markOop oldMark = mark();
markOop forwardPtrMark = markOopDesc::encode_pointer_as_mark(p);
markOop curMark;
assert(forwardPtrMark->decode_pointer() == p, "encoding must be reversable");
assert(sizeof(markOop) == sizeof(intptr_t), "CAS below requires this.");
while (!oldMark->is_marked()) {
curMark = (markOop)Atomic::cmpxchg_ptr(forwardPtrMark, &_mark, oldMark);
assert(is_forwarded(), "object should have been forwarded");
if (curMark == oldMark) {
return NULL;
}
// If the CAS was unsuccessful then curMark->is_marked()
// should return true as another thread has CAS'd in another
// forwarding pointer.
oldMark = curMark;
}
return forwardee();
}
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
// at the size. For instances, this is positive and equal to the
// size. For arrays, this is negative and provides log2 of the
// array element size. For other oops, it is zero and thus requires
// a virtual call.
//
// We go to all this trouble because the size computation is at the
// heart of phase 2 of mark-compaction, and called for every object,
// alive or dead. So the speed here is equal in importance to the
// speed of allocation.
if (lh <= Klass::_lh_neutral_value) {
// The most common case is instances; fall through if so.
if (lh < Klass::_lh_neutral_value) {
// Second most common case is arrays. We have to fetch the
// length of the array, shift (multiply) it appropriately,
// up to wordSize, add the header, and align to object size.
size_t size_in_bytes;
#ifdef _M_IA64
// The Windows Itanium Aug 2002 SDK hoists this load above
// the check for s < 0. An oop at the end of the heap will
// cause an access violation if this load is performed on a non
// array oop. Making the reference volatile prohibits this.
// (%%% please explain by what magic the length is actually fetched!)
volatile int *array_length;
array_length = (volatile int *)( (intptr_t)this +
arrayOopDesc::length_offset_in_bytes() );
assert(array_length > 0, "Integer arithmetic problem somewhere");
// Put into size_t to avoid overflow.
size_in_bytes = (size_t) array_length;
size_in_bytes = size_in_bytes << Klass::layout_helper_log2_element_size(lh);
#else
size_t array_length = (size_t) ((arrayOop)this)->length();
size_in_bytes = array_length << Klass::layout_helper_log2_element_size(lh);
#endif
size_in_bytes += Klass::layout_helper_header_size(lh);
// This code could be simplified, but by keeping array_header_in_bytes
// in units of bytes and doing it this way we can round up just once,
// 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, 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, we will need to suitably modify the assertion.
assert((s == klass->oop_size(this)) ||
(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);
}
}
assert(s % MinObjAlignment == 0, "alignment check");
assert(s > 0, "Bad size calculated");
return s;
}
