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 // [header | 00] locked locked regular object header (fast-locking in use)
58 // [header | 01] unlocked regular object header
59 // [ptr | 10] monitor inflated lock (header is swapped out, UseObjectMonitorTable == false)
60 // [header | 10] monitor inflated lock (UseObjectMonitorTable == true)
61 // [ptr | 11] marked used to mark an object
62
63 class BasicLock;
64 class ObjectMonitor;
65 class JavaThread;
66 class outputStream;
67
68 class markWord {
69 private:
70 uintptr_t _value;
71
72 public:
73 explicit markWord(uintptr_t value) : _value(value) {}
74
79 ~markWord() = default;
80 markWord(const markWord&) = default;
81 markWord& operator=(const markWord&) = default;
82
83 static markWord from_pointer(void* ptr) {
84 return markWord((uintptr_t)ptr);
85 }
86 void* to_pointer() const {
87 return (void*)_value;
88 }
89
90 bool operator==(const markWord& other) const {
91 return _value == other._value;
92 }
93 bool operator!=(const markWord& other) const {
94 return !operator==(other);
95 }
96
97 // Conversion
98 uintptr_t value() const { return _value; }
99
100 // Constants
101 static const int age_bits = 4;
102 static const int lock_bits = 2;
103 static const int self_fwd_bits = 1;
104 static const int max_hash_bits = BitsPerWord - age_bits - lock_bits - self_fwd_bits;
105 static const int hash_bits = max_hash_bits > 31 ? 31 : max_hash_bits;
106 static const int unused_gap_bits = LP64_ONLY(4) NOT_LP64(0); // Reserved for Valhalla.
107
108 static const int lock_shift = 0;
109 static const int self_fwd_shift = lock_shift + lock_bits;
110 static const int age_shift = self_fwd_shift + self_fwd_bits;
111 static const int hash_shift = age_shift + age_bits + unused_gap_bits;
112
113 static const uintptr_t lock_mask = right_n_bits(lock_bits);
114 static const uintptr_t lock_mask_in_place = lock_mask << lock_shift;
115 static const uintptr_t self_fwd_mask = right_n_bits(self_fwd_bits);
116 static const uintptr_t self_fwd_mask_in_place = self_fwd_mask << self_fwd_shift;
117 static const uintptr_t age_mask = right_n_bits(age_bits);
118 static const uintptr_t age_mask_in_place = age_mask << age_shift;
119 static const uintptr_t hash_mask = right_n_bits(hash_bits);
120 static const uintptr_t hash_mask_in_place = hash_mask << hash_shift;
121
122 #ifdef _LP64
123 // Used only with compact headers:
124 // We store the (narrow) Klass* in the bits 43 to 64.
125
126 // These are for bit-precise extraction of the narrow Klass* from the 64-bit Markword
127 static constexpr int klass_offset_in_bytes = 4;
128 static constexpr int klass_shift = hash_shift + hash_bits;
129 static constexpr int klass_shift_at_offset = klass_shift - klass_offset_in_bytes * BitsPerByte;
130 static constexpr int klass_bits = 22;
131 static constexpr uintptr_t klass_mask = right_n_bits(klass_bits);
132 static constexpr uintptr_t klass_mask_in_place = klass_mask << klass_shift;
133 #endif
134
135
136 static const uintptr_t locked_value = 0;
137 static const uintptr_t unlocked_value = 1;
138 static const uintptr_t monitor_value = 2;
139 static const uintptr_t marked_value = 3;
140
141 static const uintptr_t no_hash = 0 ; // no hash value assigned
142 static const uintptr_t no_hash_in_place = (uintptr_t)no_hash << hash_shift;
143 static const uintptr_t no_lock_in_place = unlocked_value;
144
145 static const uint max_age = age_mask;
146
147 // Creates a markWord with all bits set to zero.
148 static markWord zero() { return markWord(uintptr_t(0)); }
149
150 // lock accessors (note that these assume lock_shift == 0)
151 bool is_locked() const {
152 return (mask_bits(value(), lock_mask_in_place) != unlocked_value);
153 }
154 bool is_unlocked() const {
155 return (mask_bits(value(), lock_mask_in_place) == unlocked_value);
156 }
157 bool is_marked() const {
158 return (mask_bits(value(), lock_mask_in_place) == marked_value);
159 }
160 bool is_forwarded() const {
161 // Returns true for normal forwarded (0b011) and self-forwarded (0b1xx).
162 return mask_bits(value(), lock_mask_in_place | self_fwd_mask_in_place) >= static_cast<intptr_t>(marked_value);
163 }
164 bool is_neutral() const { // Not locked, or marked - a "clean" neutral state
165 return (mask_bits(value(), lock_mask_in_place) == unlocked_value);
166 }
167
168 // Should this header be preserved during GC?
169 bool must_be_preserved() const {
170 return (!is_unlocked() || !has_no_hash());
171 }
172
173 // WARNING: The following routines are used EXCLUSIVELY by
174 // synchronization functions. They are not really gc safe.
175 // They must get updated if markWord layout get changed.
176 markWord set_unlocked() const {
177 return markWord(value() | unlocked_value);
178 }
179
180 bool is_fast_locked() const {
181 return (value() & lock_mask_in_place) == locked_value;
182 }
183 markWord set_fast_locked() const {
184 // Clear the lock_mask_in_place bits to set locked_value:
185 return markWord(value() & ~lock_mask_in_place);
186 }
187
188 bool has_monitor() const {
189 return ((value() & lock_mask_in_place) == monitor_value);
190 }
195 assert(has_monitor(), "check");
196 assert(!UseObjectMonitorTable, "Locking with OM table does not use markWord for monitors");
197 // Use xor instead of &~ to provide one extra tag-bit check.
198 return (ObjectMonitor*) (value() ^ monitor_value);
199 }
200
201 static markWord encode(ObjectMonitor* monitor) {
202 assert(!UseObjectMonitorTable, "Locking with OM table does not use markWord for monitors");
203 uintptr_t tmp = (uintptr_t) monitor;
204 return markWord(tmp | monitor_value);
205 }
206
207 bool has_displaced_mark_helper() const {
208 intptr_t lockbits = value() & lock_mask_in_place;
209 return !UseObjectMonitorTable && lockbits == monitor_value;
210 }
211 markWord displaced_mark_helper() const;
212 void set_displaced_mark_helper(markWord m) const;
213
214 // used to encode pointers during GC
215 markWord clear_lock_bits() const { return markWord(value() & ~lock_mask_in_place); }
216
217 // age operations
218 markWord set_marked() { return markWord((value() & ~lock_mask_in_place) | marked_value); }
219 markWord set_unmarked() { return markWord((value() & ~lock_mask_in_place) | unlocked_value); }
220
221 uint age() const { return (uint) mask_bits(value() >> age_shift, age_mask); }
222 markWord set_age(uint v) const {
223 assert((v & ~age_mask) == 0, "shouldn't overflow age field");
224 return markWord((value() & ~age_mask_in_place) | ((v & age_mask) << age_shift));
225 }
226 markWord incr_age() const { return age() == max_age ? markWord(_value) : set_age(age() + 1); }
227
228 // hash operations
229 intptr_t hash() const {
230 return mask_bits(value() >> hash_shift, hash_mask);
231 }
232
233 bool has_no_hash() const {
234 return hash() == no_hash;
235 }
236
237 markWord copy_set_hash(intptr_t hash) const {
238 uintptr_t tmp = value() & (~hash_mask_in_place);
239 tmp |= ((hash & hash_mask) << hash_shift);
240 return markWord(tmp);
241 }
242
243 inline Klass* klass() const;
244 inline Klass* klass_or_null() const;
245 inline Klass* klass_without_asserts() const;
246 inline narrowKlass narrow_klass() const;
247 inline markWord set_narrow_klass(narrowKlass narrow_klass) const;
248
249 // Prototype mark for initialization
250 static markWord prototype() {
251 return markWord( no_hash_in_place | no_lock_in_place );
252 }
253
254 // Debugging
255 void print_on(outputStream* st, bool print_monitor_info = true) const;
256
257 // Prepare address of oop for placement into mark
258 inline static markWord encode_pointer_as_mark(void* p) { return from_pointer(p).set_marked(); }
259
260 // Recover address of oop from encoded form used in mark
261 inline void* decode_pointer() const { return (void*)clear_lock_bits().value(); }
262
263 inline bool is_self_forwarded() const {
264 return mask_bits(value(), self_fwd_mask_in_place) != 0;
265 }
266
267 inline markWord set_self_forwarded() const {
268 return markWord(value() | self_fwd_mask_in_place);
269 }
270
271 inline markWord unset_self_forwarded() const {
272 return markWord(value() & ~self_fwd_mask_in_place);
273 }
274
275 inline oop forwardee() const {
276 return cast_to_oop(decode_pointer());
277 }
278 };
279
280 // Support atomic operations.
281 template<>
282 struct PrimitiveConversions::Translate<markWord> : public std::true_type {
283 typedef markWord Value;
284 typedef uintptr_t Decayed;
|
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 // unused:32 klass:19 hashctrl:2 -->| unused_gap:4 age:4 self-fwd:1 lock:2 (normal object)
49 //
50 // Note: klass occupies bits 13-31 (19 bits), hashctrl occupies bits 11-12 (2 bits)
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 // - With +UseCompactObjectHeaders:
58 // hashctrl bits indicate if object has been hashed:
59 // 00 - never hashed
60 // 01 - hashed, but not expanded by GC: will recompute hash
61 // 10 - not hashed, but expanded; special state used only by CDS to deal with scratch classes
62 // 11 - hashed and expanded by GC, and hashcode has been installed in hidden field
63 //
64 // When identityHashCode() is called, the transitions work as follows:
65 // 00 - set the hashctrl bits to 01, and compute the identity hash
66 // 01 - recompute idendity hash. When GC encounters 01 when moving an object, it will allocate an extra word, if
67 // necessary, for the object copy, and install 11.
68 // 11 - read hashcode from field
69 //
70 // - the two lock bits are used to describe three states: locked/unlocked and monitor.
71 //
72 // [header | 00] locked locked regular object header (fast-locking in use)
73 // [header | 01] unlocked regular object header
74 // [ptr | 10] monitor inflated lock (header is swapped out, UseObjectMonitorTable == false)
75 // [header | 10] monitor inflated lock (UseObjectMonitorTable == true)
76 // [ptr | 11] marked used to mark an object
77
78 class BasicLock;
79 class ObjectMonitor;
80 class JavaThread;
81 class outputStream;
82
83 class markWord {
84 private:
85 uintptr_t _value;
86
87 public:
88 explicit markWord(uintptr_t value) : _value(value) {}
89
94 ~markWord() = default;
95 markWord(const markWord&) = default;
96 markWord& operator=(const markWord&) = default;
97
98 static markWord from_pointer(void* ptr) {
99 return markWord((uintptr_t)ptr);
100 }
101 void* to_pointer() const {
102 return (void*)_value;
103 }
104
105 bool operator==(const markWord& other) const {
106 return _value == other._value;
107 }
108 bool operator!=(const markWord& other) const {
109 return !operator==(other);
110 }
111
112 // Conversion
113 uintptr_t value() const { return _value; }
114 uint32_t value32() const { return (uint32_t)_value; }
115
116 // Constants
117 static const int age_bits = 4;
118 static const int lock_bits = 2;
119 static const int self_fwd_bits = 1;
120 static const int max_hash_bits = BitsPerWord - age_bits - lock_bits - self_fwd_bits;
121 static const int hash_bits = max_hash_bits > 31 ? 31 : max_hash_bits;
122 static const int unused_gap_bits = LP64_ONLY(4) NOT_LP64(0); // Reserved for Valhalla.
123 static const int hashctrl_bits = 2;
124
125 static const int lock_shift = 0;
126 static const int self_fwd_shift = lock_shift + lock_bits;
127 static const int age_shift = self_fwd_shift + self_fwd_bits;
128 static const int hash_shift = age_shift + age_bits + unused_gap_bits;
129 static const int hashctrl_shift = age_shift + age_bits + unused_gap_bits;
130
131 static const uintptr_t lock_mask = right_n_bits(lock_bits);
132 static const uintptr_t lock_mask_in_place = lock_mask << lock_shift;
133 static const uintptr_t self_fwd_mask = right_n_bits(self_fwd_bits);
134 static const uintptr_t self_fwd_mask_in_place = self_fwd_mask << self_fwd_shift;
135 static const uintptr_t age_mask = right_n_bits(age_bits);
136 static const uintptr_t age_mask_in_place = age_mask << age_shift;
137 static const uintptr_t hash_mask = right_n_bits(hash_bits);
138 static const uintptr_t hash_mask_in_place = hash_mask << hash_shift;
139 static const uintptr_t hashctrl_mask = right_n_bits(hashctrl_bits);
140 static const uintptr_t hashctrl_mask_in_place = hashctrl_mask << hashctrl_shift;
141 static const uintptr_t hashctrl_hashed_mask_in_place = ((uintptr_t)1) << hashctrl_shift;
142 static const uintptr_t hashctrl_expanded_mask_in_place = ((uintptr_t)2) << hashctrl_shift;
143
144 #ifdef _LP64
145 // Used only with compact headers:
146 // With UseCompactObjectHeaders: We store the (narrow) Klass* in bits 13-31 (19 bits total).
147 // Without UseCompactObjectHeaders: Klass* is stored separately in object header, not in markword.
148
149 // These are for bit-precise extraction of the narrow Klass* from the markword (UseCompactObjectHeaders only)
150 //
151 // Bit position summary for UseCompactObjectHeaders:
152 // Bits 0- 1: lock (2 bits)
153 // Bit 2 : self-fwd (1 bit)
154 // Bits 3- 6: age (4 bits)
155 // Bits 7-10: unused_gap (4 bits)
156 // Bits 11-12: hashctrl (2 bits) - hash control state
157 // Bits 13-31: klass (19 bits) - narrow klass pointer
158 // Bits 32-63: unused (32 bits)
159 //
160 // Without UseCompactObjectHeaders, klass is stored separately in object header
161 static constexpr int klass_shift = hashctrl_shift + hashctrl_bits;
162 static constexpr int klass_bits = 19;
163 static constexpr uintptr_t klass_mask = right_n_bits(klass_bits);
164 static constexpr uintptr_t klass_mask_in_place = klass_mask << klass_shift;
165 #endif
166
167
168 static const uintptr_t locked_value = 0;
169 static const uintptr_t unlocked_value = 1;
170 static const uintptr_t monitor_value = 2;
171 static const uintptr_t marked_value = 3;
172 static const uintptr_t forward_expanded_value = 0b111;
173
174 static const uintptr_t no_hash = 0 ; // no hash value assigned
175 static const uintptr_t no_hash_in_place = (uintptr_t)no_hash << hash_shift;
176 static const uintptr_t no_lock_in_place = unlocked_value;
177
178 static const uint max_age = age_mask;
179
180 // Creates a markWord with all bits set to zero.
181 static markWord zero() { return markWord(uintptr_t(0)); }
182
183 // lock accessors (note that these assume lock_shift == 0)
184 bool is_locked() const {
185 return (mask_bits(value(), lock_mask_in_place) != unlocked_value);
186 }
187 bool is_unlocked() const {
188 return (mask_bits(value(), lock_mask_in_place) == unlocked_value);
189 }
190 bool is_marked() const {
191 return (value() & (self_fwd_mask_in_place | lock_mask_in_place)) > monitor_value;
192 }
193 bool is_forwarded() const {
194 // Returns true for normal forwarded (0b011) and self-forwarded (0b1xx).
195 return mask_bits(value(), lock_mask_in_place | self_fwd_mask_in_place) >= static_cast<intptr_t>(marked_value);
196 }
197 bool is_neutral() const { // Not locked, or marked - a "clean" neutral state
198 return (mask_bits(value(), lock_mask_in_place) == unlocked_value);
199 }
200
201 markWord set_forward_expanded() {
202 assert((value() & (lock_mask_in_place | self_fwd_mask_in_place)) == marked_value, "must be normal-forwarded here");
203 return markWord(value() | forward_expanded_value);
204 }
205 bool is_forward_expanded() {
206 return (value() & (lock_mask_in_place | self_fwd_mask_in_place)) == forward_expanded_value;
207 }
208
209 // Should this header be preserved during GC?
210 bool must_be_preserved() const {
211 return UseCompactObjectHeaders ? !is_unlocked() : (!is_unlocked() || !has_no_hash());
212 }
213
214 // WARNING: The following routines are used EXCLUSIVELY by
215 // synchronization functions. They are not really gc safe.
216 // They must get updated if markWord layout get changed.
217 markWord set_unlocked() const {
218 return markWord(value() | unlocked_value);
219 }
220
221 bool is_fast_locked() const {
222 return (value() & lock_mask_in_place) == locked_value;
223 }
224 markWord set_fast_locked() const {
225 // Clear the lock_mask_in_place bits to set locked_value:
226 return markWord(value() & ~lock_mask_in_place);
227 }
228
229 bool has_monitor() const {
230 return ((value() & lock_mask_in_place) == monitor_value);
231 }
236 assert(has_monitor(), "check");
237 assert(!UseObjectMonitorTable, "Locking with OM table does not use markWord for monitors");
238 // Use xor instead of &~ to provide one extra tag-bit check.
239 return (ObjectMonitor*) (value() ^ monitor_value);
240 }
241
242 static markWord encode(ObjectMonitor* monitor) {
243 assert(!UseObjectMonitorTable, "Locking with OM table does not use markWord for monitors");
244 uintptr_t tmp = (uintptr_t) monitor;
245 return markWord(tmp | monitor_value);
246 }
247
248 bool has_displaced_mark_helper() const {
249 intptr_t lockbits = value() & lock_mask_in_place;
250 return !UseObjectMonitorTable && lockbits == monitor_value;
251 }
252 markWord displaced_mark_helper() const;
253 void set_displaced_mark_helper(markWord m) const;
254
255 // used to encode pointers during GC
256 markWord clear_lock_bits() const { return markWord(value() & ~(lock_mask_in_place | self_fwd_mask_in_place)); }
257
258 // age operations
259 markWord set_marked() { return markWord((value() & ~lock_mask_in_place) | marked_value); }
260 markWord set_unmarked() { return markWord((value() & ~lock_mask_in_place) | unlocked_value); }
261
262 uint age() const { return (uint) mask_bits(value() >> age_shift, age_mask); }
263 markWord set_age(uint v) const {
264 assert((v & ~age_mask) == 0, "shouldn't overflow age field");
265 return markWord((value() & ~age_mask_in_place) | ((v & age_mask) << age_shift));
266 }
267 markWord incr_age() const { return age() == max_age ? markWord(_value) : set_age(age() + 1); }
268
269 // hash operations
270 intptr_t hash() const {
271 assert(!UseCompactObjectHeaders, "only without compact i-hash");
272 return mask_bits(value() >> hash_shift, hash_mask);
273 }
274
275 bool has_no_hash() const {
276 if (UseCompactObjectHeaders) {
277 return !is_hashed();
278 } else {
279 return hash() == no_hash;
280 }
281 }
282
283 inline bool is_hashed_not_expanded() const {
284 assert(UseCompactObjectHeaders, "only with compact i-hash");
285 return (value() & hashctrl_mask_in_place) == hashctrl_hashed_mask_in_place;
286 }
287 inline markWord set_hashed_not_expanded() const {
288 assert(UseCompactObjectHeaders, "only with compact i-hash");
289 return markWord((value() & ~hashctrl_mask_in_place) | hashctrl_hashed_mask_in_place);
290 }
291
292 inline bool is_hashed_expanded() const {
293 assert(UseCompactObjectHeaders, "only with compact i-hash");
294 return (value() & hashctrl_mask_in_place) == (hashctrl_hashed_mask_in_place | hashctrl_expanded_mask_in_place);
295 }
296 inline markWord set_hashed_expanded() const {
297 assert(UseCompactObjectHeaders, "only with compact i-hash");
298 return markWord((value() & ~hashctrl_mask_in_place) | (hashctrl_hashed_mask_in_place | hashctrl_expanded_mask_in_place));
299 }
300
301 // This is a special hashctrl state (11) that is only used
302 // during CDS archive dumping. There we allocate 'scratch mirrors' for
303 // each real mirror klass. We allocate those scratch mirrors
304 // in a pre-extended form, but without being hashed. When the
305 // real mirror gets hashed, then we turn the scratch mirror into
306 // hashed_moved state, otherwise we leave it in that special state
307 // which indicates that the archived copy will be allocated in the
308 // unhashed form.
309 inline bool is_not_hashed_expanded() const {
310 assert(UseCompactObjectHeaders, "only with compact i-hash");
311 return (value() & hashctrl_mask_in_place) == hashctrl_expanded_mask_in_place;
312 }
313 inline markWord set_not_hashed_expanded() const {
314 assert(UseCompactObjectHeaders, "only with compact i-hash");
315 return markWord((value() & ~hashctrl_mask_in_place) | hashctrl_expanded_mask_in_place);
316 }
317 inline markWord set_not_hashed_not_expanded() const {
318 assert(UseCompactObjectHeaders, "only with compact i-hash");
319 return markWord(value() & ~(hashctrl_mask_in_place | hashctrl_expanded_mask_in_place));
320 }
321 // Return true when object is either hashed_moved or not_hashed_moved.
322 inline bool is_expanded() const {
323 assert(UseCompactObjectHeaders, "only with compact i-hash");
324 return (value() & hashctrl_expanded_mask_in_place) != 0;
325 }
326 inline bool is_hashed() const {
327 assert(UseCompactObjectHeaders, "only with compact i-hash");
328 return (value() & hashctrl_hashed_mask_in_place) != 0;
329 }
330
331 inline markWord copy_hashctrl_from(markWord m) const {
332 if (UseCompactObjectHeaders) {
333 return markWord((value() & ~hashctrl_mask_in_place) | (m.value() & hashctrl_mask_in_place));
334 } else {
335 return markWord(value());
336 }
337 }
338
339 markWord copy_set_hash(intptr_t hash) const {
340 uintptr_t tmp = value() & (~hash_mask_in_place);
341 tmp |= ((hash & hash_mask) << hash_shift);
342 return markWord(tmp);
343 }
344
345 inline Klass* klass() const;
346 inline Klass* klass_or_null() const;
347 inline Klass* klass_without_asserts() const;
348 inline narrowKlass narrow_klass() const;
349 inline markWord set_narrow_klass(narrowKlass narrow_klass) const;
350
351 #ifdef _LP64
352 inline int array_length() { return checked_cast<int>(value() >> 32); }
353 #endif
354
355 // Prototype mark for initialization
356 static markWord prototype() {
357 if (UseCompactObjectHeaders) {
358 return markWord(no_lock_in_place);
359 } else {
360 return markWord(no_hash_in_place | no_lock_in_place);
361 }
362 }
363
364 // Debugging
365 void print_on(outputStream* st, bool print_monitor_info = true) const;
366
367 // Prepare address of oop for placement into mark
368 inline static markWord encode_pointer_as_mark(void* p) { return from_pointer(p).set_marked(); }
369
370 // Recover address of oop from encoded form used in mark
371 inline void* decode_pointer() const { return (void*)clear_lock_bits().value(); }
372
373 inline bool is_self_forwarded() const {
374 // Match 100, 101, 110 but not 111.
375 return mask_bits(value() + 1, (lock_mask_in_place | self_fwd_mask_in_place)) > 4;
376 }
377
378 inline markWord set_self_forwarded() const {
379 return markWord(value() | self_fwd_mask_in_place);
380 }
381
382 inline markWord unset_self_forwarded() const {
383 return markWord(value() & ~self_fwd_mask_in_place);
384 }
385
386 inline oop forwardee() const {
387 return cast_to_oop(decode_pointer());
388 }
389 };
390
391 // Support atomic operations.
392 template<>
393 struct PrimitiveConversions::Translate<markWord> : public std::true_type {
394 typedef markWord Value;
395 typedef uintptr_t Decayed;
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