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#ifndef SHARE_OOPS_MARKWORD_HPP
#define SHARE_OOPS_MARKWORD_HPP
#include "metaprogramming/primitiveConversions.hpp"
+ #include "oops/compressedKlass.hpp"
#include "oops/oopsHierarchy.hpp"
#include "runtime/globals.hpp"
#include <type_traits>
//
// Bit-format of an object header (most significant first, big endian layout below):
//
// 32 bits:
// --------
- // hash:25 ------------>| age:4 unused_gap:1 lock:2 (normal object)
+ // hash:25 ------------>| age:4 self-fwd:1 lock:2 (normal object)
//
// 64 bits:
// --------
- // unused:25 hash:31 -->| unused_gap:1 age:4 unused_gap:1 lock:2 (normal object)
+ // unused:25 hash:31 -->| unused_gap:1 age:4 self-fwd:1 lock:2 (normal object)
+ //
+ // 64 bits (with compact headers):
+ // -------------------------------
+ // nklass:32 hash:25 -->| unused_gap:1 age:4 self-fwded:1 lock:2 (normal object)
//
// - 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
uintptr_t value() const { return _value; }
// Constants
static const int age_bits = 4;
static const int lock_bits = 2;
- static const int first_unused_gap_bits = 1;
- static const int max_hash_bits = BitsPerWord - age_bits - lock_bits - first_unused_gap_bits;
+ static const int self_fwd_bits = 1;
+ static const int max_hash_bits = BitsPerWord - age_bits - lock_bits - self_fwd_bits;
static const int hash_bits = max_hash_bits > 31 ? 31 : max_hash_bits;
- static const int second_unused_gap_bits = LP64_ONLY(1) NOT_LP64(0);
+ static const int hash_bits_compact = hash_bits;
+ // Used only without compact headers.
+ static const int unused_gap_bits = LP64_ONLY(1) NOT_LP64(0);
static const int lock_shift = 0;
- static const int age_shift = lock_bits + first_unused_gap_bits;
- static const int hash_shift = age_shift + age_bits + second_unused_gap_bits;
+ static const int self_fwd_shift = lock_shift + lock_bits;
+ static const int age_shift = self_fwd_shift + self_fwd_bits;
+ static const int hash_shift = age_shift + age_bits + unused_gap_bits;
+ static const int hash_shift_compact = 11;
static const uintptr_t lock_mask = right_n_bits(lock_bits);
static const uintptr_t lock_mask_in_place = lock_mask << lock_shift;
+ static const uintptr_t self_fwd_mask = right_n_bits(self_fwd_bits);
+ static const uintptr_t self_fwd_mask_in_place = self_fwd_mask << self_fwd_shift;
static const uintptr_t age_mask = right_n_bits(age_bits);
static const uintptr_t age_mask_in_place = age_mask << age_shift;
static const uintptr_t hash_mask = right_n_bits(hash_bits);
static const uintptr_t hash_mask_in_place = hash_mask << hash_shift;
+ static const uintptr_t hash_mask_compact = right_n_bits(hash_bits_compact);
+ static const uintptr_t hash_mask_compact_in_place = hash_mask_compact << hash_shift_compact;
+
+ #ifdef _LP64
+ // Used only with compact headers:
+ // We store nKlass in the upper 22 bits of the markword. When extracting, we need to read the upper
+ // 32 bits and rightshift by the lower 10 foreign bits.
+
+ // These are for loading the nKlass with a 32-bit load and subsequent masking of the lower
+ // shadow bits
+ static constexpr int klass_load_shift = 32;
+ static constexpr int klass_load_bits = 32;
+ static constexpr int klass_shadow_bits = 10;
+ static constexpr uintptr_t klass_shadow_mask = right_n_bits(klass_shadow_bits);
+ static constexpr uintptr_t klass_shadow_mask_inplace = klass_shadow_mask << klass_load_shift;
+
+ // These are for bit-precise extraction of the nKlass from the 64-bit Markword
+ static constexpr int klass_shift = 42;
+ static constexpr int klass_bits = 22;
+ static constexpr uintptr_t klass_mask = right_n_bits(klass_bits);
+ static constexpr uintptr_t klass_mask_in_place = klass_mask << klass_shift;
+ #endif
+
static const uintptr_t locked_value = 0;
static const uintptr_t unlocked_value = 1;
static const uintptr_t monitor_value = 2;
static const uintptr_t marked_value = 3;
return (mask_bits(value(), lock_mask_in_place) == unlocked_value);
}
bool is_marked() const {
return (mask_bits(value(), lock_mask_in_place) == marked_value);
}
- bool is_forwarded() const {
- return (mask_bits(value(), lock_mask_in_place) == marked_value);
+ bool is_forwarded() const {
+ // Returns true for normal forwarded (0b011) and self-forwarded (0b1xx).
+ return mask_bits(value(), lock_mask_in_place | self_fwd_mask_in_place) >= static_cast<intptr_t>(marked_value);
}
+
bool is_neutral() const { // Not locked, or marked - a "clean" neutral state
return (mask_bits(value(), lock_mask_in_place) == unlocked_value);
}
// Special temporary state of the markWord while being inflated.
bool has_monitor() const {
return ((value() & lock_mask_in_place) == monitor_value);
}
ObjectMonitor* monitor() const {
assert(has_monitor(), "check");
+ assert(!UseObjectMonitorTable, "Lightweight locking with OM table does not use markWord for monitors");
// Use xor instead of &~ to provide one extra tag-bit check.
return (ObjectMonitor*) (value() ^ monitor_value);
}
bool has_displaced_mark_helper() const {
intptr_t lockbits = value() & lock_mask_in_place;
- return LockingMode == LM_LIGHTWEIGHT ? lockbits == monitor_value // monitor?
- : (lockbits & unlocked_value) == 0; // monitor | stack-locked?
+ if (LockingMode == LM_LIGHTWEIGHT) {
+ return !UseObjectMonitorTable && lockbits == monitor_value;
+ }
+ // monitor (0b10) | stack-locked (0b00)?
+ return (lockbits & unlocked_value) == 0;
}
markWord displaced_mark_helper() const;
void set_displaced_mark_helper(markWord m) const;
markWord copy_set_hash(intptr_t hash) const {
- uintptr_t tmp = value() & (~hash_mask_in_place);
- tmp |= ((hash & hash_mask) << hash_shift);
- return markWord(tmp);
+ if (UseCompactObjectHeaders) {
+ uintptr_t tmp = value() & (~hash_mask_compact_in_place);
+ tmp |= ((hash & hash_mask_compact) << hash_shift_compact);
+ return markWord(tmp);
+ } else {
+ uintptr_t tmp = value() & (~hash_mask_in_place);
+ tmp |= ((hash & hash_mask) << hash_shift);
+ return markWord(tmp);
+ }
}
// it is only used to be stored into BasicLock as the
// indicator that the lock is using heavyweight monitor
static markWord unused_mark() {
return markWord(marked_value);
// stored into object header, it encodes monitor info
static markWord encode(BasicLock* lock) {
return from_pointer(lock);
}
static markWord encode(ObjectMonitor* monitor) {
+ assert(!UseObjectMonitorTable, "Lightweight locking with OM table does not use markWord for monitors");
uintptr_t tmp = (uintptr_t) monitor;
return markWord(tmp | monitor_value);
}
+ markWord set_has_monitor() const {
+ return markWord((value() & ~lock_mask_in_place) | monitor_value);
+ }
+
// used to encode pointers during GC
markWord clear_lock_bits() const { return markWord(value() & ~lock_mask_in_place); }
// age operations
markWord set_marked() { return markWord((value() & ~lock_mask_in_place) | marked_value); }
}
markWord incr_age() const { return age() == max_age ? markWord(_value) : set_age(age() + 1); }
// hash operations
intptr_t hash() const {
- return mask_bits(value() >> hash_shift, hash_mask);
+ if (UseCompactObjectHeaders) {
+ return mask_bits(value() >> hash_shift_compact, hash_mask_compact);
+ } else {
+ return mask_bits(value() >> hash_shift, hash_mask);
+ }
}
bool has_no_hash() const {
return hash() == no_hash;
}
+ inline Klass* klass() const;
+ inline Klass* klass_or_null() const;
+ inline Klass* klass_without_asserts() const;
+ inline narrowKlass narrow_klass() const;
+ inline markWord set_narrow_klass(narrowKlass nklass) const;
+ inline markWord set_klass(Klass* klass) const;
+
// Prototype mark for initialization
static markWord prototype() {
return markWord( no_hash_in_place | no_lock_in_place );
}
inline static markWord encode_pointer_as_mark(void* p) { return from_pointer(p).set_marked(); }
// Recover address of oop from encoded form used in mark
inline void* decode_pointer() const { return (void*)clear_lock_bits().value(); }
+ inline bool self_forwarded() const {
+ NOT_LP64(assert(LockingMode != LM_LEGACY, "incorrect with LM_LEGACY on 32 bit");)
+ return mask_bits(value(), self_fwd_mask_in_place) != 0;
+ }
+
+ inline markWord set_self_forwarded() const {
+ NOT_LP64(assert(LockingMode != LM_LEGACY, "incorrect with LM_LEGACY on 32 bit");)
+ return markWord(value() | self_fwd_mask_in_place);
+ }
+
+ inline markWord unset_self_forwarded() const {
+ NOT_LP64(assert(LockingMode != LM_LEGACY, "incorrect with LM_LEGACY on 32 bit");)
+ return markWord(value() & ~self_fwd_mask_in_place);
+ }
+
inline oop forwardee() const {
return cast_to_oop(decode_pointer());
}
};
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