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src/hotspot/share/gc/shenandoah/shenandoahForwarding.inline.hpp

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13  * accompanied this code).
14  *
15  * You should have received a copy of the GNU General Public License version
16  * 2 along with this work; if not, write to the Free Software Foundation,
17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18  *
19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20  * or visit www.oracle.com if you need additional information or have any
21  * questions.
22  *
23  */
24 
25 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP
26 #define SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP
27 
28 #include "gc/shenandoah/shenandoahForwarding.hpp"
29 
30 #include "gc/shenandoah/shenandoahAsserts.hpp"
31 #include "oops/markWord.hpp"
32 #include "runtime/javaThread.hpp"

33 
34 inline oop ShenandoahForwarding::get_forwardee_raw(oop obj) {
35   shenandoah_assert_in_heap(nullptr, obj);
36   return get_forwardee_raw_unchecked(obj);
37 }
38 
39 inline oop ShenandoahForwarding::get_forwardee_raw_unchecked(oop obj) {
40   // JVMTI and JFR code use mark words for marking objects for their needs.
41   // On this path, we can encounter the "marked" object, but with null
42   // fwdptr. That object is still not forwarded, and we need to return
43   // the object itself.
44   markWord mark = obj->mark();
45   if (mark.is_marked()) {
46     HeapWord* fwdptr = (HeapWord*) mark.clear_lock_bits().to_pointer();
47     if (fwdptr != nullptr) {
48       return cast_to_oop(fwdptr);
49     }
50   }
51   return obj;
52 }

69 inline oop ShenandoahForwarding::get_forwardee(oop obj) {
70   shenandoah_assert_correct(nullptr, obj);
71   return get_forwardee_raw_unchecked(obj);
72 }
73 
74 inline bool ShenandoahForwarding::is_forwarded(oop obj) {
75   return obj->mark().is_marked();
76 }
77 
78 inline oop ShenandoahForwarding::try_update_forwardee(oop obj, oop update) {
79   markWord old_mark = obj->mark();
80   if (old_mark.is_marked()) {
81     return cast_to_oop(old_mark.clear_lock_bits().to_pointer());
82   }
83 
84   markWord new_mark = markWord::encode_pointer_as_mark(update);
85   markWord prev_mark = obj->cas_set_mark(new_mark, old_mark, memory_order_conservative);
86   if (prev_mark == old_mark) {
87     return update;
88   } else {

89     return cast_to_oop(prev_mark.clear_lock_bits().to_pointer());
90   }
91 }
92 
93 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP

13  * accompanied this code).
14  *
15  * You should have received a copy of the GNU General Public License version
16  * 2 along with this work; if not, write to the Free Software Foundation,
17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18  *
19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20  * or visit www.oracle.com if you need additional information or have any
21  * questions.
22  *
23  */
24 
25 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP
26 #define SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP
27 
28 #include "gc/shenandoah/shenandoahForwarding.hpp"
29 
30 #include "gc/shenandoah/shenandoahAsserts.hpp"
31 #include "oops/markWord.hpp"
32 #include "runtime/javaThread.hpp"
33 #include "runtime/synchronizer.hpp"
34 
35 inline oop ShenandoahForwarding::get_forwardee_raw(oop obj) {
36   shenandoah_assert_in_heap(nullptr, obj);
37   return get_forwardee_raw_unchecked(obj);
38 }
39 
40 inline oop ShenandoahForwarding::get_forwardee_raw_unchecked(oop obj) {
41   // JVMTI and JFR code use mark words for marking objects for their needs.
42   // On this path, we can encounter the "marked" object, but with null
43   // fwdptr. That object is still not forwarded, and we need to return
44   // the object itself.
45   markWord mark = obj->mark();
46   if (mark.is_marked()) {
47     HeapWord* fwdptr = (HeapWord*) mark.clear_lock_bits().to_pointer();
48     if (fwdptr != nullptr) {
49       return cast_to_oop(fwdptr);
50     }
51   }
52   return obj;
53 }

70 inline oop ShenandoahForwarding::get_forwardee(oop obj) {
71   shenandoah_assert_correct(nullptr, obj);
72   return get_forwardee_raw_unchecked(obj);
73 }
74 
75 inline bool ShenandoahForwarding::is_forwarded(oop obj) {
76   return obj->mark().is_marked();
77 }
78 
79 inline oop ShenandoahForwarding::try_update_forwardee(oop obj, oop update) {
80   markWord old_mark = obj->mark();
81   if (old_mark.is_marked()) {
82     return cast_to_oop(old_mark.clear_lock_bits().to_pointer());
83   }
84 
85   markWord new_mark = markWord::encode_pointer_as_mark(update);
86   markWord prev_mark = obj->cas_set_mark(new_mark, old_mark, memory_order_conservative);
87   if (prev_mark == old_mark) {
88     return update;
89   } else {
90     assert(prev_mark.is_marked(), "must be forwarded");
91     return cast_to_oop(prev_mark.clear_lock_bits().to_pointer());
92   }
93 }
94 
95 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP
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