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// bits, including 'self-fwd' are 0. "is_self_forwarded()" will be correctly
// set to false. Otherwise encode_pointer_as_mark() may have 'self-fwd' set.
//
// - age - used by some GCs to track the age of objects.
//
- // - valhalla - reserved for valhalla
+ // - valhalla - only supported on 64-bit VMs
+ //
+ // * inline types: A value class instance
+ // * flat arrays: An array with flattened value class elements
+ // * null-free arrays: An array instance without null elements
+ // * valhalla reserved: Reserved for future use
+ //
+ // Inline types cannot be locked and do not have an identity hash.
//
// - hash - contains the identity hash value: largest value is 31 bits, see
// os::random(). Also, 64-bit VMs require a hash value no bigger than 32
// bits because they will not properly generate a mask larger than that:
// see library_call.cpp
// Number of bits
static const int lock_bits = 2;
static const int self_fwd_bits = 1;
static const int age_bits = 4;
- static const int valhalla_reserved_bits = LP64_ONLY(4) NOT_LP64(0);
- static const int max_hash_bits = BitsPerWord - age_bits - lock_bits - self_fwd_bits - valhalla_reserved_bits;
+ static const int inline_type_bits = LP64_ONLY(1) NOT_LP64(0);
+ static const int null_free_array_bits = LP64_ONLY(1) NOT_LP64(0);
+ static const int flat_array_bits = LP64_ONLY(1) NOT_LP64(0);
+ static const int valhalla_reserved_bits = LP64_ONLY(1) NOT_LP64(0);
+ static const int max_hash_bits = BitsPerWord - age_bits - lock_bits - inline_type_bits - valhalla_reserved_bits - flat_array_bits - null_free_array_bits - self_fwd_bits;
static const int hash_bits = max_hash_bits > 31 ? 31 : max_hash_bits;
// Shifts
static const int lock_shift = 0;
static const int self_fwd_shift = lock_shift + lock_bits;
static const int age_shift = self_fwd_shift + self_fwd_bits;
- static const int valhalla_reserved_shift = age_shift + age_bits;
+ static const int inline_type_shift = age_shift + age_bits;
+ static const int null_free_array_shift = inline_type_shift + inline_type_bits;
+ static const int flat_array_shift = null_free_array_shift + null_free_array_bits;
+ static const int valhalla_reserved_shift = flat_array_shift + flat_array_bits;
static const int hash_shift = valhalla_reserved_shift + valhalla_reserved_bits;
// Masks (in-place)
static const uintptr_t lock_mask_in_place = right_n_bits(lock_bits) << lock_shift;
static const uintptr_t self_fwd_bit_in_place = right_n_bits(self_fwd_bits) << self_fwd_shift;
static const uintptr_t age_mask_in_place = right_n_bits(age_bits) << age_shift;
+ static const uintptr_t inline_type_bit_in_place = right_n_bits(inline_type_bits) << inline_type_shift;
+ static const uintptr_t null_free_array_bit_in_place = right_n_bits(null_free_array_bits) << null_free_array_shift;
+ static const uintptr_t flat_array_bit_in_place = right_n_bits(flat_array_bits) << flat_array_shift;
+ static const uintptr_t valhalla_reserved_bit_in_place = right_n_bits(valhalla_reserved_bits) << valhalla_reserved_shift;
static const uintptr_t hash_mask_in_place = right_n_bits(hash_bits) << hash_shift;
// Verify that _bit_in_place refers to constants with only one bit.
static_assert(is_power_of_2(self_fwd_bit_in_place));
+ #ifdef _LP64
+ static_assert(is_power_of_2(inline_type_bit_in_place));
+ static_assert(is_power_of_2(null_free_array_bit_in_place));
+ static_assert(is_power_of_2(flat_array_bit_in_place));
+ static_assert(is_power_of_2(valhalla_reserved_bit_in_place));
+ #endif
// Masks (unshifted)
static const uintptr_t lock_mask = lock_mask_in_place >> lock_shift;
static const uintptr_t age_mask = age_mask_in_place >> age_shift;
static const uintptr_t hash_mask = hash_mask_in_place >> hash_shift;
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;
+ static const uintptr_t inline_type_pattern = inline_type_bit_in_place | unlocked_value;
+ static const uintptr_t inline_type_pattern_mask = inline_type_bit_in_place | lock_mask_in_place;
+
static const uintptr_t no_hash = 0 ; // no hash value assigned
static const uintptr_t no_hash_in_place = (uintptr_t)no_hash << hash_shift;
static const uintptr_t no_lock_in_place = unlocked_value;
static const uint max_age = age_mask;
// Creates a markWord with all bits set to zero.
static markWord zero() { return markWord(uintptr_t(0)); }
+ bool is_inline_type() const {
+ #ifdef _LP64 // 64 bit encodings only
+ return (mask_bits(value(), inline_type_pattern_mask) == inline_type_pattern);
+ #else
+ return false;
+ #endif
+ }
+
// 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 {
bool is_marked() const {
return (mask_bits(value(), lock_mask_in_place) == marked_value);
}
bool is_neutral() const { // Not locked, or marked - a "clean" neutral state
+ LP64_ONLY(assert(!is_unlocked() || mask_bits(value(), inline_type_bit_in_place) == 0,
+ "Inline types should not be used for locking. _value: " PTR_FORMAT, _value));
return (mask_bits(value(), lock_mask_in_place) == unlocked_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_bit_in_place) >= static_cast<intptr_t>(marked_value);
}
// Should this header be preserved during GC?
bool must_be_preserved() const {
+ // The reserved bits are only guaranteed to be unset if the mark word is "unlocked"
+ LP64_ONLY(assert(!is_unlocked() || mask_bits(value(), valhalla_reserved_bit_in_place) == 0,
+ "Reserved bits should not be used. _value: " PTR_FORMAT, _value));
return !is_unlocked() || !has_no_hash();
}
// WARNING: The following routines are used EXCLUSIVELY by
// synchronization functions. They are not really gc safe.
bool has_no_hash() const {
return hash() == no_hash;
}
+ bool is_flat_array() const {
+ assert(!has_monitor_pointer(), "Bits are not valid if replaced by a monitor pointer: " PTR_FORMAT, value());
+ assert(!is_marked(), "Bits might not be valid if marked by the GC: " PTR_FORMAT, value());
+ #ifdef _LP64 // 64 bit encodings only
+ return (mask_bits(value(), flat_array_bit_in_place) != 0);
+ #else
+ return false;
+ #endif
+ }
+
+ bool is_null_free_array() const {
+ assert(!has_monitor_pointer(), "Bits are not valid if replaced by a monitor pointer: " PTR_FORMAT, value());
+ assert(!is_marked(), "Bits might not be valid if marked by the GC: " PTR_FORMAT, value());
+ #ifdef _LP64 // 64 bit encodings only
+ return (mask_bits(value(), null_free_array_bit_in_place) != 0);
+ #else
+ return false;
+ #endif
+ }
+
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);
}
inline Klass* klass_or_null() const;
inline Klass* klass_without_asserts() const;
inline narrowKlass narrow_klass() const;
inline markWord set_narrow_klass(narrowKlass narrow_klass) const;
- // Prototype mark for initialization
+ // Prototype marks for initialization
+
static markWord prototype() {
return markWord(unlocked_value);
}
+ static markWord inline_type_prototype() {
+ NOT_LP64(assert(false, "Should not be called in 32 bit mode"));
+ return markWord(unlocked_value | inline_type_bit_in_place);
+ }
+
+ static markWord flat_array_prototype(bool null_free) {
+ NOT_LP64(assert(false, "Should not be called in 32 bit mode"));
+ if (null_free) {
+ return markWord(unlocked_value | flat_array_bit_in_place | null_free_array_bit_in_place);
+ } else {
+ return markWord(unlocked_value | flat_array_bit_in_place);
+ }
+ }
+
+ static markWord null_free_array_prototype() {
+ NOT_LP64(assert(false, "Should not be called in 32 bit mode"));
+ return markWord(unlocked_value | null_free_array_bit_in_place);
+ }
+
// Debugging
void print_on(outputStream* st, bool print_monitor_info = true) const;
// Prepare address of oop for placement into mark
inline static markWord encode_pointer_as_mark(void* p) { return from_pointer(p).set_marked(); }
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