Mercurial > hg > truffle
view src/share/vm/oops/markOop.hpp @ 9300:d73ad771a602
return immutable collections from (some) CompilationResult getters
author | Doug Simon <doug.simon@oracle.com> |
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date | Thu, 25 Apr 2013 17:45:44 +0200 |
parents | 22b8d3d181d9 |
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/* * Copyright (c) 1997, 2012, Oracle and/or its affiliates. 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. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #ifndef SHARE_VM_OOPS_MARKOOP_HPP #define SHARE_VM_OOPS_MARKOOP_HPP #include "oops/oop.hpp" // The markOop describes the header of an object. // // Note that the mark is not a real oop but just a word. // It is placed in the oop hierarchy for historical reasons. // // Bit-format of an object header (most significant first, big endian layout below): // // 32 bits: // -------- // hash:25 ------------>| age:4 biased_lock:1 lock:2 (normal object) // JavaThread*:23 epoch:2 age:4 biased_lock:1 lock:2 (biased object) // size:32 ------------------------------------------>| (CMS free block) // PromotedObject*:29 ---------->| promo_bits:3 ----->| (CMS promoted object) // // 64 bits: // -------- // unused:25 hash:31 -->| unused:1 age:4 biased_lock:1 lock:2 (normal object) // JavaThread*:54 epoch:2 unused:1 age:4 biased_lock:1 lock:2 (biased object) // PromotedObject*:61 --------------------->| promo_bits:3 ----->| (CMS promoted object) // size:64 ----------------------------------------------------->| (CMS free block) // // unused:25 hash:31 -->| cms_free:1 age:4 biased_lock:1 lock:2 (COOPs && normal object) // JavaThread*:54 epoch:2 cms_free:1 age:4 biased_lock:1 lock:2 (COOPs && biased object) // narrowOop:32 unused:24 cms_free:1 unused:4 promo_bits:3 ----->| (COOPs && CMS promoted object) // unused:21 size:35 -->| cms_free:1 unused:7 ------------------>| (COOPs && CMS free block) // // - hash contains the identity hash value: largest value is // 31 bits, see os::random(). Also, 64-bit vm's require // a hash value no bigger than 32 bits because they will not // properly generate a mask larger than that: see library_call.cpp // and c1_CodePatterns_sparc.cpp. // // - the biased lock pattern is used to bias a lock toward a given // thread. When this pattern is set in the low three bits, the lock // is either biased toward a given thread or "anonymously" biased, // indicating that it is possible for it to be biased. When the // lock is biased toward a given thread, locking and unlocking can // be performed by that thread without using atomic operations. // When a lock's bias is revoked, it reverts back to the normal // locking scheme described below. // // Note that we are overloading the meaning of the "unlocked" state // of the header. Because we steal a bit from the age we can // guarantee that the bias pattern will never be seen for a truly // unlocked object. // // Note also that the biased state contains the age bits normally // contained in the object header. Large increases in scavenge // times were seen when these bits were absent and an arbitrary age // assigned to all biased objects, because they tended to consume a // significant fraction of the eden semispaces and were not // promoted promptly, causing an increase in the amount of copying // performed. The runtime system aligns all JavaThread* pointers to // a very large value (currently 128 bytes (32bVM) or 256 bytes (64bVM)) // to make room for the age bits & the epoch bits (used in support of // biased locking), and for the CMS "freeness" bit in the 64bVM (+COOPs). // // [JavaThread* | epoch | age | 1 | 01] lock is biased toward given thread // [0 | epoch | age | 1 | 01] lock is anonymously biased // // - the two lock bits are used to describe three states: locked/unlocked and monitor. // // [ptr | 00] locked ptr points to real header on stack // [header | 0 | 01] unlocked regular object header // [ptr | 10] monitor inflated lock (header is wapped out) // [ptr | 11] marked used by markSweep to mark an object // not valid at any other time // // We assume that stack/thread pointers have the lowest two bits cleared. class BasicLock; class ObjectMonitor; class JavaThread; class markOopDesc: public oopDesc { private: // Conversion uintptr_t value() const { return (uintptr_t) this; } public: // Constants enum { age_bits = 4, lock_bits = 2, biased_lock_bits = 1, max_hash_bits = BitsPerWord - age_bits - lock_bits - biased_lock_bits, hash_bits = max_hash_bits > 31 ? 31 : max_hash_bits, cms_bits = LP64_ONLY(1) NOT_LP64(0), epoch_bits = 2 }; // The biased locking code currently requires that the age bits be // contiguous to the lock bits. enum { lock_shift = 0, biased_lock_shift = lock_bits, age_shift = lock_bits + biased_lock_bits, cms_shift = age_shift + age_bits, hash_shift = cms_shift + cms_bits, epoch_shift = hash_shift }; enum { lock_mask = right_n_bits(lock_bits), lock_mask_in_place = lock_mask << lock_shift, biased_lock_mask = right_n_bits(lock_bits + biased_lock_bits), biased_lock_mask_in_place= biased_lock_mask << lock_shift, biased_lock_bit_in_place = 1 << biased_lock_shift, age_mask = right_n_bits(age_bits), age_mask_in_place = age_mask << age_shift, epoch_mask = right_n_bits(epoch_bits), epoch_mask_in_place = epoch_mask << epoch_shift, cms_mask = right_n_bits(cms_bits), cms_mask_in_place = cms_mask << cms_shift #ifndef _WIN64 ,hash_mask = right_n_bits(hash_bits), hash_mask_in_place = (address_word)hash_mask << hash_shift #endif }; // Alignment of JavaThread pointers encoded in object header required by biased locking enum { biased_lock_alignment = 2 << (epoch_shift + epoch_bits) }; #ifdef _WIN64 // These values are too big for Win64 const static uintptr_t hash_mask = right_n_bits(hash_bits); const static uintptr_t hash_mask_in_place = (address_word)hash_mask << hash_shift; #endif enum { locked_value = 0, unlocked_value = 1, monitor_value = 2, marked_value = 3, biased_lock_pattern = 5 }; enum { no_hash = 0 }; // no hash value assigned enum { no_hash_in_place = (address_word)no_hash << hash_shift, no_lock_in_place = unlocked_value }; enum { max_age = age_mask }; enum { max_bias_epoch = epoch_mask }; // Biased Locking accessors. // These must be checked by all code which calls into the // ObjectSynchronizer and other code. The biasing is not understood // by the lower-level CAS-based locking code, although the runtime // fixes up biased locks to be compatible with it when a bias is // revoked. bool has_bias_pattern() const { return (mask_bits(value(), biased_lock_mask_in_place) == biased_lock_pattern); } JavaThread* biased_locker() const { assert(has_bias_pattern(), "should not call this otherwise"); return (JavaThread*) ((intptr_t) (mask_bits(value(), ~(biased_lock_mask_in_place | age_mask_in_place | epoch_mask_in_place)))); } // Indicates that the mark has the bias bit set but that it has not // yet been biased toward a particular thread bool is_biased_anonymously() const { return (has_bias_pattern() && (biased_locker() == NULL)); } // Indicates epoch in which this bias was acquired. If the epoch // changes due to too many bias revocations occurring, the biases // from the previous epochs are all considered invalid. int bias_epoch() const { assert(has_bias_pattern(), "should not call this otherwise"); return (mask_bits(value(), epoch_mask_in_place) >> epoch_shift); } markOop set_bias_epoch(int epoch) { assert(has_bias_pattern(), "should not call this otherwise"); assert((epoch & (~epoch_mask)) == 0, "epoch overflow"); return markOop(mask_bits(value(), ~epoch_mask_in_place) | (epoch << epoch_shift)); } markOop incr_bias_epoch() { return set_bias_epoch((1 + bias_epoch()) & epoch_mask); } // Prototype mark for initialization static markOop biased_locking_prototype() { return markOop( biased_lock_pattern ); } // lock accessors (note that these assume lock_shift == 0) bool is_locked() const { return (mask_bits(value(), lock_mask_in_place) != unlocked_value); } bool is_unlocked() const { return (mask_bits(value(), biased_lock_mask_in_place) == unlocked_value); } bool is_marked() const { return (mask_bits(value(), lock_mask_in_place) == marked_value); } bool is_neutral() const { return (mask_bits(value(), biased_lock_mask_in_place) == unlocked_value); } // Special temporary state of the markOop while being inflated. // Code that looks at mark outside a lock need to take this into account. bool is_being_inflated() const { return (value() == 0); } // Distinguished markword value - used when inflating over // an existing stacklock. 0 indicates the markword is "BUSY". // Lockword mutators that use a LD...CAS idiom should always // check for and avoid overwriting a 0 value installed by some // other thread. (They should spin or block instead. The 0 value // is transient and *should* be short-lived). static markOop INFLATING() { return (markOop) 0; } // inflate-in-progress // Should this header be preserved during GC? inline bool must_be_preserved(oop obj_containing_mark) const; inline bool must_be_preserved_with_bias(oop obj_containing_mark) const; // Should this header (including its age bits) be preserved in the // case of a promotion failure during scavenge? // Note that we special case this situation. We want to avoid // calling BiasedLocking::preserve_marks()/restore_marks() (which // decrease the number of mark words that need to be preserved // during GC) during each scavenge. During scavenges in which there // is no promotion failure, we actually don't need to call the above // routines at all, since we don't mutate and re-initialize the // marks of promoted objects using init_mark(). However, during // scavenges which result in promotion failure, we do re-initialize // the mark words of objects, meaning that we should have called // these mark word preservation routines. Currently there's no good // place in which to call them in any of the scavengers (although // guarded by appropriate locks we could make one), but the // observation is that promotion failures are quite rare and // reducing the number of mark words preserved during them isn't a // high priority. inline bool must_be_preserved_for_promotion_failure(oop obj_containing_mark) const; inline bool must_be_preserved_with_bias_for_promotion_failure(oop obj_containing_mark) const; // Should this header be preserved during a scavenge where CMS is // the old generation? // (This is basically the same body as must_be_preserved_for_promotion_failure(), // but takes the Klass* as argument instead) inline bool must_be_preserved_for_cms_scavenge(Klass* klass_of_obj_containing_mark) const; inline bool must_be_preserved_with_bias_for_cms_scavenge(Klass* klass_of_obj_containing_mark) const; // WARNING: The following routines are used EXCLUSIVELY by // synchronization functions. They are not really gc safe. // They must get updated if markOop layout get changed. markOop set_unlocked() const { return markOop(value() | unlocked_value); } bool has_locker() const { return ((value() & lock_mask_in_place) == locked_value); } BasicLock* locker() const { assert(has_locker(), "check"); return (BasicLock*) value(); } bool has_monitor() const { return ((value() & monitor_value) != 0); } ObjectMonitor* monitor() const { assert(has_monitor(), "check"); // Use xor instead of &~ to provide one extra tag-bit check. return (ObjectMonitor*) (value() ^ monitor_value); } bool has_displaced_mark_helper() const { return ((value() & unlocked_value) == 0); } markOop displaced_mark_helper() const { assert(has_displaced_mark_helper(), "check"); intptr_t ptr = (value() & ~monitor_value); return *(markOop*)ptr; } void set_displaced_mark_helper(markOop m) const { assert(has_displaced_mark_helper(), "check"); intptr_t ptr = (value() & ~monitor_value); *(markOop*)ptr = m; } markOop copy_set_hash(intptr_t hash) const { intptr_t tmp = value() & (~hash_mask_in_place); tmp |= ((hash & hash_mask) << hash_shift); return (markOop)tmp; } // it is only used to be stored into BasicLock as the // indicator that the lock is using heavyweight monitor static markOop unused_mark() { return (markOop) marked_value; } // the following two functions create the markOop to be // stored into object header, it encodes monitor info static markOop encode(BasicLock* lock) { return (markOop) lock; } static markOop encode(ObjectMonitor* monitor) { intptr_t tmp = (intptr_t) monitor; return (markOop) (tmp | monitor_value); } static markOop encode(JavaThread* thread, uint age, int bias_epoch) { intptr_t tmp = (intptr_t) thread; assert(UseBiasedLocking && ((tmp & (epoch_mask_in_place | age_mask_in_place | biased_lock_mask_in_place)) == 0), "misaligned JavaThread pointer"); assert(age <= max_age, "age too large"); assert(bias_epoch <= max_bias_epoch, "bias epoch too large"); return (markOop) (tmp | (bias_epoch << epoch_shift) | (age << age_shift) | biased_lock_pattern); } // used to encode pointers during GC markOop clear_lock_bits() { return markOop(value() & ~lock_mask_in_place); } // age operations markOop set_marked() { return markOop((value() & ~lock_mask_in_place) | marked_value); } markOop set_unmarked() { return markOop((value() & ~lock_mask_in_place) | unlocked_value); } uint age() const { return mask_bits(value() >> age_shift, age_mask); } markOop set_age(uint v) const { assert((v & ~age_mask) == 0, "shouldn't overflow age field"); return markOop((value() & ~age_mask_in_place) | (((uintptr_t)v & age_mask) << age_shift)); } markOop incr_age() const { return age() == max_age ? markOop(this) : set_age(age() + 1); } // hash operations intptr_t hash() const { return mask_bits(value() >> hash_shift, hash_mask); } bool has_no_hash() const { return hash() == no_hash; } // Prototype mark for initialization static markOop prototype() { return markOop( no_hash_in_place | no_lock_in_place ); } // Helper function for restoration of unmarked mark oops during GC static inline markOop prototype_for_object(oop obj); // Debugging void print_on(outputStream* st) const; // Prepare address of oop for placement into mark inline static markOop encode_pointer_as_mark(void* p) { return markOop(p)->set_marked(); } // Recover address of oop from encoded form used in mark inline void* decode_pointer() { if (UseBiasedLocking && has_bias_pattern()) return NULL; return clear_lock_bits(); } // These markOops indicate cms free chunk blocks and not objects. // In 64 bit, the markOop is set to distinguish them from oops. // These are defined in 32 bit mode for vmStructs. const static uintptr_t cms_free_chunk_pattern = 0x1; // Constants for the size field. enum { size_shift = cms_shift + cms_bits, size_bits = 35 // need for compressed oops 32G }; // These values are too big for Win64 const static uintptr_t size_mask = LP64_ONLY(right_n_bits(size_bits)) NOT_LP64(0); const static uintptr_t size_mask_in_place = (address_word)size_mask << size_shift; #ifdef _LP64 static markOop cms_free_prototype() { return markOop(((intptr_t)prototype() & ~cms_mask_in_place) | ((cms_free_chunk_pattern & cms_mask) << cms_shift)); } uintptr_t cms_encoding() const { return mask_bits(value() >> cms_shift, cms_mask); } bool is_cms_free_chunk() const { return is_neutral() && (cms_encoding() & cms_free_chunk_pattern) == cms_free_chunk_pattern; } size_t get_size() const { return (size_t)(value() >> size_shift); } static markOop set_size_and_free(size_t size) { assert((size & ~size_mask) == 0, "shouldn't overflow size field"); return markOop(((intptr_t)cms_free_prototype() & ~size_mask_in_place) | (((intptr_t)size & size_mask) << size_shift)); } #endif // _LP64 }; #endif // SHARE_VM_OOPS_MARKOOP_HPP