11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
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_OOPS_MARKWORD_HPP
26 #define SHARE_OOPS_MARKWORD_HPP
27
28 #include "cppstdlib/type_traits.hpp"
29 #include "metaprogramming/primitiveConversions.hpp"
30 #include "oops/compressedKlass.hpp"
31 #include "oops/oopsHierarchy.hpp"
32 #include "runtime/globals.hpp"
33
34 // The markWord describes the header of an object.
35 //
36 // Bit-format of an object header (most significant first, big endian layout below):
37 //
38 // 32 bits:
39 // --------
40 // hash:25 ------------>| age:4 self-fwd:1 lock:2 (normal object)
41 //
42 // 64 bits:
43 // --------
44 // unused:22 hash:31 -->| unused_gap:4 age:4 self-fwd:1 lock:2 (normal object)
45 //
46 // 64 bits (with compact headers):
47 // -------------------------------
48 // klass:22 hash:31 -->| unused_gap:4 age:4 self-fwd:1 lock:2 (normal object)
49 //
50 // - hash contains the identity hash value: largest value is
51 // 31 bits, see os::random(). Also, 64-bit vm's require
52 // a hash value no bigger than 32 bits because they will not
53 // properly generate a mask larger than that: see library_call.cpp
54 //
55 // - the two lock bits are used to describe three states: locked/unlocked and monitor.
56 //
57 // [ptr | 00] locked ptr points to real header on stack (stack-locking in use)
58 // [header | 00] locked locked regular object header (fast-locking in use)
59 // [header | 01] unlocked regular object header
60 // [ptr | 10] monitor inflated lock (header is swapped out, UseObjectMonitorTable == false)
61 // [header | 10] monitor inflated lock (UseObjectMonitorTable == true)
62 // [ptr | 11] marked used to mark an object
63 // [0 ............ 0| 00] inflating inflation in progress (stack-locking in use)
64 //
65 // We assume that stack/thread pointers have the lowest two bits cleared.
66 //
67 // - INFLATING() is a distinguished markword value of all zeros that is
68 // used when inflating an existing stack-lock into an ObjectMonitor.
69 // See below for is_being_inflated() and INFLATING().
70
71 class BasicLock;
72 class ObjectMonitor;
73 class JavaThread;
74 class outputStream;
75
76 class markWord {
77 private:
78 uintptr_t _value;
79
80 public:
81 explicit markWord(uintptr_t value) : _value(value) {}
82
83 markWord() = default; // Doesn't initialize _value.
84
85 // It is critical for performance that this class be trivially
86 // destructable, copyable, and assignable.
87 ~markWord() = default;
88 markWord(const markWord&) = default;
89 markWord& operator=(const markWord&) = default;
90
91 static markWord from_pointer(void* ptr) {
92 return markWord((uintptr_t)ptr);
93 }
94 void* to_pointer() const {
95 return (void*)_value;
96 }
97
98 bool operator==(const markWord& other) const {
99 return _value == other._value;
100 }
101 bool operator!=(const markWord& other) const {
102 return !operator==(other);
103 }
104
105 // Conversion
106 uintptr_t value() const { return _value; }
107
108 // Constants
109 static const int age_bits = 4;
110 static const int lock_bits = 2;
111 static const int self_fwd_bits = 1;
112 static const int max_hash_bits = BitsPerWord - age_bits - lock_bits - self_fwd_bits;
113 static const int hash_bits = max_hash_bits > 31 ? 31 : max_hash_bits;
114 static const int unused_gap_bits = LP64_ONLY(4) NOT_LP64(0); // Reserved for Valhalla.
115
116 static const int lock_shift = 0;
117 static const int self_fwd_shift = lock_shift + lock_bits;
118 static const int age_shift = self_fwd_shift + self_fwd_bits;
119 static const int hash_shift = age_shift + age_bits + unused_gap_bits;
120
121 static const uintptr_t lock_mask = right_n_bits(lock_bits);
122 static const uintptr_t lock_mask_in_place = lock_mask << lock_shift;
123 static const uintptr_t self_fwd_mask = right_n_bits(self_fwd_bits);
124 static const uintptr_t self_fwd_mask_in_place = self_fwd_mask << self_fwd_shift;
125 static const uintptr_t age_mask = right_n_bits(age_bits);
126 static const uintptr_t age_mask_in_place = age_mask << age_shift;
127 static const uintptr_t hash_mask = right_n_bits(hash_bits);
128 static const uintptr_t hash_mask_in_place = hash_mask << hash_shift;
129
130 #ifdef _LP64
131 // Used only with compact headers:
132 // We store the (narrow) Klass* in the bits 43 to 64.
133
134 // These are for bit-precise extraction of the narrow Klass* from the 64-bit Markword
135 static constexpr int klass_offset_in_bytes = 4;
136 static constexpr int klass_shift = hash_shift + hash_bits;
137 static constexpr int klass_shift_at_offset = klass_shift - klass_offset_in_bytes * BitsPerByte;
138 static constexpr int klass_bits = 22;
139 static constexpr uintptr_t klass_mask = right_n_bits(klass_bits);
140 static constexpr uintptr_t klass_mask_in_place = klass_mask << klass_shift;
141 #endif
142
143
144 static const uintptr_t locked_value = 0;
145 static const uintptr_t unlocked_value = 1;
146 static const uintptr_t monitor_value = 2;
147 static const uintptr_t marked_value = 3;
148
149 static const uintptr_t no_hash = 0 ; // no hash value assigned
150 static const uintptr_t no_hash_in_place = (uintptr_t)no_hash << hash_shift;
151 static const uintptr_t no_lock_in_place = unlocked_value;
152
153 static const uint max_age = age_mask;
154
155 // Creates a markWord with all bits set to zero.
156 static markWord zero() { return markWord(uintptr_t(0)); }
157
158 // lock accessors (note that these assume lock_shift == 0)
159 bool is_locked() const {
160 return (mask_bits(value(), lock_mask_in_place) != unlocked_value);
161 }
162 bool is_unlocked() const {
163 return (mask_bits(value(), lock_mask_in_place) == unlocked_value);
164 }
165 bool is_marked() const {
166 return (mask_bits(value(), lock_mask_in_place) == marked_value);
167 }
168 bool is_forwarded() const {
169 // Returns true for normal forwarded (0b011) and self-forwarded (0b1xx).
170 return mask_bits(value(), lock_mask_in_place | self_fwd_mask_in_place) >= static_cast<intptr_t>(marked_value);
171 }
172 bool is_neutral() const { // Not locked, or marked - a "clean" neutral state
173 return (mask_bits(value(), lock_mask_in_place) == unlocked_value);
174 }
175
176 // Special temporary state of the markWord while being inflated.
177 // Code that looks at mark outside a lock need to take this into account.
178 bool is_being_inflated() const { return (value() == 0); }
179
180 // Distinguished markword value - used when inflating over
181 // an existing stack-lock. 0 indicates the markword is "BUSY".
182 // Lockword mutators that use a LD...CAS idiom should always
183 // check for and avoid overwriting a 0 value installed by some
184 // other thread. (They should spin or block instead. The 0 value
185 // is transient and *should* be short-lived).
186 // Fast-locking does not use INFLATING.
187 static markWord INFLATING() { return zero(); } // inflate-in-progress
188
189 // Should this header be preserved during GC?
190 bool must_be_preserved() const {
191 return (!is_unlocked() || !has_no_hash());
192 }
193
194 // WARNING: The following routines are used EXCLUSIVELY by
195 // synchronization functions. They are not really gc safe.
196 // They must get updated if markWord layout get changed.
197 markWord set_unlocked() const {
198 return markWord(value() | unlocked_value);
199 }
200
201 bool is_fast_locked() const {
202 return (value() & lock_mask_in_place) == locked_value;
203 }
204 markWord set_fast_locked() const {
205 // Clear the lock_mask_in_place bits to set locked_value:
206 return markWord(value() & ~lock_mask_in_place);
207 }
208
209 bool has_monitor() const {
210 return ((value() & lock_mask_in_place) == monitor_value);
211 }
252 // age operations
253 markWord set_marked() { return markWord((value() & ~lock_mask_in_place) | marked_value); }
254 markWord set_unmarked() { return markWord((value() & ~lock_mask_in_place) | unlocked_value); }
255
256 uint age() const { return (uint) mask_bits(value() >> age_shift, age_mask); }
257 markWord set_age(uint v) const {
258 assert((v & ~age_mask) == 0, "shouldn't overflow age field");
259 return markWord((value() & ~age_mask_in_place) | ((v & age_mask) << age_shift));
260 }
261 markWord incr_age() const { return age() == max_age ? markWord(_value) : set_age(age() + 1); }
262
263 // hash operations
264 intptr_t hash() const {
265 return mask_bits(value() >> hash_shift, hash_mask);
266 }
267
268 bool has_no_hash() const {
269 return hash() == no_hash;
270 }
271
272 inline Klass* klass() const;
273 inline Klass* klass_or_null() const;
274 inline Klass* klass_without_asserts() const;
275 inline narrowKlass narrow_klass() const;
276 inline markWord set_narrow_klass(narrowKlass narrow_klass) const;
277
278 // Prototype mark for initialization
279 static markWord prototype() {
280 return markWord( no_hash_in_place | no_lock_in_place );
281 }
282
283 // Debugging
284 void print_on(outputStream* st, bool print_monitor_info = true) const;
285
286 // Prepare address of oop for placement into mark
287 inline static markWord encode_pointer_as_mark(void* p) { return from_pointer(p).set_marked(); }
288
289 // Recover address of oop from encoded form used in mark
290 inline void* decode_pointer() const { return (void*)clear_lock_bits().value(); }
291
292 inline bool is_self_forwarded() const {
293 return mask_bits(value(), self_fwd_mask_in_place) != 0;
294 }
295
296 inline markWord set_self_forwarded() const {
297 return markWord(value() | self_fwd_mask_in_place);
298 }
299
300 inline markWord unset_self_forwarded() const {
301 return markWord(value() & ~self_fwd_mask_in_place);
302 }
303
304 inline oop forwardee() const {
305 return cast_to_oop(decode_pointer());
306 }
307 };
308
309 // Support atomic operations.
310 template<>
|
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
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_OOPS_MARKWORD_HPP
26 #define SHARE_OOPS_MARKWORD_HPP
27
28 #include "cppstdlib/type_traits.hpp"
29 #include "metaprogramming/primitiveConversions.hpp"
30 #include "oops/compressedKlass.hpp"
31 #include "oops/layoutKind.hpp"
32 #include "oops/oopsHierarchy.hpp"
33 #include "runtime/globals.hpp"
34 #include "utilities/vmEnums.hpp"
35
36 // The markWord describes the header of an object.
37 //
38 // Bit-format of an object header (most significant first, big endian layout below):
39 //
40 // 32 bits:
41 // --------
42 // hash:25 ------------>| age:4 self-fwd:1 lock:2 (normal object)
43 //
44 // 64 bits:
45 // --------
46 // unused:22 hash:31 -->| valhalla:4 age:4 self-fwd:1 lock:2 (normal object)
47 //
48 // 64 bits (with compact headers):
49 // -------------------------------
50 // klass:22 hash:31 -->| valhalla:4 age:4 self-fwd:1 lock:2 (normal object)
51 //
52 // - hash contains the identity hash value: largest value is
53 // 31 bits, see os::random(). Also, 64-bit vm's require
54 // a hash value no bigger than 32 bits because they will not
55 // properly generate a mask larger than that: see library_call.cpp
56 //
57 // - the two lock bits are used to describe three states: locked/unlocked and monitor.
58 //
59 // [ptr | 00] locked ptr points to real header on stack (stack-locking in use)
60 // [header | 00] locked locked regular object header (fast-locking in use)
61 // [header | 01] unlocked regular object header
62 // [ptr | 10] monitor inflated lock (header is swapped out, UseObjectMonitorTable == false)
63 // [header | 10] monitor inflated lock (UseObjectMonitorTable == true)
64 // [ptr | 11] marked used to mark an object
65 // [0 ............ 0| 00] inflating inflation in progress (stack-locking in use)
66 //
67 // We assume that stack/thread pointers have the lowest two bits cleared.
68 //
69 //
70 // - INFLATING() is a distinguished markword value of all zeros that is
71 // used when inflating an existing stack-lock into an ObjectMonitor.
72 // See below for is_being_inflated() and INFLATING().
73 //
74 // VALHALLA EXTENSIONS:
75 //
76 // N.B.: 32 bit mode is not supported, this section assumes 64 bit systems.
77 //
78 // Project Valhalla uses markWord bits to denote the following oops (listed least to most significant):
79 // * inline types: have alternative bytecode behavior, e.g. can not be locked
80 // * flat arrays: load/decode of klass layout helper is expensive for aaload
81 // * "null free" arrays: load/decode of klass layout helper again for aaload
82 // * inline type: "larval state": mutable state, but only during object init, observable
83 // by only by a single thread (generally do not mutate markWord)
84 //
85 // Inline types cannot be locked, monitored or inflating.
86 //
87 // Note the position of 'self-fwd' is not by accident. When forwarding an
88 // object to a new heap position, HeapWord alignment guarantees the lower
89 // bits, including 'self-fwd' are 0. "is_self_forwarded()" will be correctly
90 // set to false. Otherwise encode_pointer_as_mark() may have 'self-fwd' set.
91
92 class BasicLock;
93 class ObjectMonitor;
94 class JavaThread;
95 class outputStream;
96
97 class markWord {
98 private:
99 uintptr_t _value;
100
101 public:
102 explicit markWord(uintptr_t value) : _value(value) {}
103
104 markWord() = default; // Doesn't initialize _value.
105
106 // It is critical for performance that this class be trivially
107 // destructable, copyable, and assignable.
108 ~markWord() = default;
109 markWord(const markWord&) = default;
110 markWord& operator=(const markWord&) = default;
111
112 static markWord from_pointer(void* ptr) {
113 return markWord((uintptr_t)ptr);
114 }
115 void* to_pointer() const {
116 return (void*)_value;
117 }
118
119 bool operator==(const markWord& other) const {
120 return _value == other._value;
121 }
122 bool operator!=(const markWord& other) const {
123 return !operator==(other);
124 }
125
126 // Conversion
127 uintptr_t value() const { return _value; }
128
129 // Constants, in least significant bit order
130 static const int lock_bits = 2;
131 static const int self_fwd_bits = 1;
132 // instance state
133 static const int age_bits = 4;
134 // EnableValhalla: static prototype header bits (fast path instead of klass layout_helper)
135 static const int inline_type_bits = 1;
136 static const int null_free_array_bits = LP64_ONLY(1) NOT_LP64(0);
137 static const int flat_array_bits = LP64_ONLY(1) NOT_LP64(0);
138 static const int larval_bits = 1;
139 static const int max_hash_bits = BitsPerWord - age_bits - lock_bits - inline_type_bits - larval_bits - flat_array_bits - null_free_array_bits - self_fwd_bits;
140 static const int hash_bits = max_hash_bits > 31 ? 31 : max_hash_bits;
141
142 static const int lock_shift = 0;
143 static const int self_fwd_shift = lock_shift + lock_bits;
144 static const int age_shift = self_fwd_shift + self_fwd_bits;
145 static const int inline_type_shift = age_shift + age_bits;
146 static const int null_free_array_shift = inline_type_shift + inline_type_bits;
147 static const int flat_array_shift = null_free_array_shift + null_free_array_bits;
148 static const int larval_shift = flat_array_shift + flat_array_bits;
149 static const int hash_shift = larval_shift + larval_bits;
150
151 static const uintptr_t lock_mask = right_n_bits(lock_bits);
152 static const uintptr_t lock_mask_in_place = lock_mask << lock_shift;
153 static const uintptr_t self_fwd_mask = right_n_bits(self_fwd_bits);
154 static const uintptr_t self_fwd_mask_in_place = self_fwd_mask << self_fwd_shift;
155 static const uintptr_t inline_type_bit_in_place = right_n_bits(inline_type_bits) << inline_type_shift;
156 static const uintptr_t inline_type_mask_in_place = inline_type_bit_in_place + lock_mask;
157 static const uintptr_t null_free_array_mask = right_n_bits(null_free_array_bits);
158 static const uintptr_t null_free_array_mask_in_place = (null_free_array_mask << null_free_array_shift) | lock_mask_in_place;
159 static const uintptr_t null_free_array_bit_in_place = (right_n_bits(null_free_array_bits) << null_free_array_shift);
160 static const uintptr_t flat_array_mask = right_n_bits(flat_array_bits);
161 static const uintptr_t flat_array_mask_in_place = (flat_array_mask << flat_array_shift) | null_free_array_mask_in_place | lock_mask_in_place;
162 static const uintptr_t flat_array_bit_in_place = right_n_bits(flat_array_bits) << flat_array_shift;
163 static const uintptr_t age_mask = right_n_bits(age_bits);
164 static const uintptr_t age_mask_in_place = age_mask << age_shift;
165
166 static const uintptr_t larval_mask = right_n_bits(larval_bits);
167 static const uintptr_t larval_mask_in_place = (larval_mask << larval_shift) | inline_type_mask_in_place;
168 static const uintptr_t larval_bit_in_place = right_n_bits(larval_bits) << larval_shift;
169
170 static const uintptr_t hash_mask = right_n_bits(hash_bits);
171 static const uintptr_t hash_mask_in_place = hash_mask << hash_shift;
172
173 #ifdef _LP64
174 // Used only with compact headers:
175 // We store the (narrow) Klass* in the bits 43 to 64.
176
177 // These are for bit-precise extraction of the narrow Klass* from the 64-bit Markword
178 static constexpr int klass_offset_in_bytes = 4;
179 static constexpr int klass_shift = hash_shift + hash_bits;
180 static constexpr int klass_shift_at_offset = klass_shift - klass_offset_in_bytes * BitsPerByte;
181 static constexpr int klass_bits = 22;
182 static constexpr uintptr_t klass_mask = right_n_bits(klass_bits);
183 static constexpr uintptr_t klass_mask_in_place = klass_mask << klass_shift;
184 #endif
185
186
187 static const uintptr_t locked_value = 0;
188 static const uintptr_t unlocked_value = 1;
189 static const uintptr_t monitor_value = 2;
190 static const uintptr_t marked_value = 3;
191
192 static const uintptr_t inline_type_pattern = inline_type_bit_in_place | unlocked_value;
193 static const uintptr_t null_free_array_pattern = null_free_array_bit_in_place | unlocked_value;
194 static const uintptr_t null_free_flat_array_pattern = flat_array_bit_in_place | null_free_array_pattern;
195 static const uintptr_t nullable_flat_array_pattern = flat_array_bit_in_place | unlocked_value;
196
197 static const uintptr_t larval_pattern = larval_bit_in_place | inline_type_pattern;
198
199 static const uintptr_t no_hash = 0 ; // no hash value assigned
200 static const uintptr_t no_hash_in_place = (uintptr_t)no_hash << hash_shift;
201 static const uintptr_t no_lock_in_place = unlocked_value;
202
203 static const uint max_age = age_mask;
204
205 // Creates a markWord with all bits set to zero.
206 static markWord zero() { return markWord(uintptr_t(0)); }
207
208 bool is_inline_type() const {
209 return (mask_bits(value(), inline_type_mask_in_place) == inline_type_pattern);
210 }
211
212 // lock accessors (note that these assume lock_shift == 0)
213 bool is_locked() const {
214 return (mask_bits(value(), lock_mask_in_place) != unlocked_value);
215 }
216 bool is_unlocked() const {
217 return (mask_bits(value(), lock_mask_in_place) == unlocked_value);
218 }
219 bool is_marked() const {
220 return (mask_bits(value(), lock_mask_in_place) == marked_value);
221 }
222
223 // is unlocked and not an inline type (which cannot be involved in locking, displacement or inflation)
224 // i.e. test both lock bits and the inline type bit together
225 bool is_neutral() const { // Not locked, or marked - a "clean" neutral state
226 return (mask_bits(value(), inline_type_mask_in_place) == unlocked_value);
227 }
228
229 bool is_forwarded() const {
230 // Returns true for normal forwarded (0b011) and self-forwarded (0b1xx).
231 return mask_bits(value(), lock_mask_in_place | self_fwd_mask_in_place) >= static_cast<intptr_t>(marked_value);
232 }
233
234 // Special temporary state of the markWord while being inflated.
235 // Code that looks at mark outside a lock need to take this into account.
236 bool is_being_inflated() const { return (value() == 0); }
237
238 // Distinguished markword value - used when inflating over
239 // an existing stack-lock. 0 indicates the markword is "BUSY".
240 // Lockword mutators that use a LD...CAS idiom should always
241 // check for and avoid overwriting a 0 value installed by some
242 // other thread. (They should spin or block instead. The 0 value
243 // is transient and *should* be short-lived).
244 // Fast-locking does not use INFLATING.
245 static markWord INFLATING() { return zero(); } // inflate-in-progress
246
247 // Should this header be preserved during GC?
248 bool must_be_preserved() const {
249 return (!is_unlocked() || !has_no_hash() ||
250 (EnableValhalla && (is_larval_state() || is_inline_type() || is_flat_array() || is_null_free_array())));
251 }
252
253 // WARNING: The following routines are used EXCLUSIVELY by
254 // synchronization functions. They are not really gc safe.
255 // They must get updated if markWord layout get changed.
256 markWord set_unlocked() const {
257 return markWord(value() | unlocked_value);
258 }
259
260 bool is_fast_locked() const {
261 return (value() & lock_mask_in_place) == locked_value;
262 }
263 markWord set_fast_locked() const {
264 // Clear the lock_mask_in_place bits to set locked_value:
265 return markWord(value() & ~lock_mask_in_place);
266 }
267
268 bool has_monitor() const {
269 return ((value() & lock_mask_in_place) == monitor_value);
270 }
311 // age operations
312 markWord set_marked() { return markWord((value() & ~lock_mask_in_place) | marked_value); }
313 markWord set_unmarked() { return markWord((value() & ~lock_mask_in_place) | unlocked_value); }
314
315 uint age() const { return (uint) mask_bits(value() >> age_shift, age_mask); }
316 markWord set_age(uint v) const {
317 assert((v & ~age_mask) == 0, "shouldn't overflow age field");
318 return markWord((value() & ~age_mask_in_place) | ((v & age_mask) << age_shift));
319 }
320 markWord incr_age() const { return age() == max_age ? markWord(_value) : set_age(age() + 1); }
321
322 // hash operations
323 intptr_t hash() const {
324 return mask_bits(value() >> hash_shift, hash_mask);
325 }
326
327 bool has_no_hash() const {
328 return hash() == no_hash;
329 }
330
331 // private buffered value operations
332 markWord enter_larval_state() const {
333 return markWord(value() | larval_bit_in_place);
334 }
335 markWord exit_larval_state() const {
336 return markWord(value() & ~larval_bit_in_place);
337 }
338 bool is_larval_state() const {
339 return (mask_bits(value(), larval_mask_in_place) == larval_pattern);
340 }
341
342 bool is_flat_array() const {
343 #ifdef _LP64 // 64 bit encodings only
344 return (mask_bits(value(), flat_array_mask_in_place) == null_free_flat_array_pattern)
345 || (mask_bits(value(), flat_array_mask_in_place) == nullable_flat_array_pattern);
346 #else
347 return false;
348 #endif
349 }
350
351 bool is_null_free_array() const {
352 #ifdef _LP64 // 64 bit encodings only
353 return (mask_bits(value(), null_free_array_mask_in_place) == null_free_array_pattern);
354 #else
355 return false;
356 #endif
357 }
358
359 inline Klass* klass() const;
360 inline Klass* klass_or_null() const;
361 inline Klass* klass_without_asserts() const;
362 inline narrowKlass narrow_klass() const;
363 inline markWord set_narrow_klass(narrowKlass narrow_klass) const;
364
365 // Prototype mark for initialization
366 static markWord prototype() {
367 return markWord( no_hash_in_place | no_lock_in_place );
368 }
369
370 static markWord inline_type_prototype() {
371 return markWord(inline_type_pattern);
372 }
373
374 #ifdef _LP64 // 64 bit encodings only
375 static markWord flat_array_prototype(LayoutKind lk);
376
377 static markWord null_free_array_prototype() {
378 return markWord(null_free_array_pattern);
379 }
380 #endif
381
382 // Debugging
383 void print_on(outputStream* st, bool print_monitor_info = true) const;
384
385 // Prepare address of oop for placement into mark
386 inline static markWord encode_pointer_as_mark(void* p) { return from_pointer(p).set_marked(); }
387
388 inline void* decode_pointer() const {
389 return (void*) (clear_lock_bits().value());
390 }
391
392 inline bool is_self_forwarded() const {
393 return mask_bits(value(), self_fwd_mask_in_place) != 0;
394 }
395
396 inline markWord set_self_forwarded() const {
397 return markWord(value() | self_fwd_mask_in_place);
398 }
399
400 inline markWord unset_self_forwarded() const {
401 return markWord(value() & ~self_fwd_mask_in_place);
402 }
403
404 inline oop forwardee() const {
405 return cast_to_oop(decode_pointer());
406 }
407 };
408
409 // Support atomic operations.
410 template<>
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