9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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_ARRAYOOP_HPP
26 #define SHARE_OOPS_ARRAYOOP_HPP
27
28 #include "oops/oop.hpp"
29 #include "utilities/align.hpp"
30 #include "utilities/globalDefinitions.hpp"
31
32 // arrayOopDesc is the abstract baseclass for all arrays. It doesn't
33 // declare pure virtual to enforce this because that would allocate a vtbl
34 // in each instance, which we don't want.
35
36 // The layout of array Oops is:
37 //
38 // markWord
39 // Klass* // 32 bits if compressed but declared 64 in LP64.
40 // length // shares klass memory or allocated after declared fields.
41
42
43 class arrayOopDesc : public oopDesc {
44 friend class VMStructs;
45 friend class arrayOopDescTest;
46
47 // Interpreter/Compiler offsets
48
49 private:
50 // Returns the address of the length "field". See length_offset_in_bytes().
51 static int* length_addr_impl(void* obj_ptr) {
52 char* ptr = static_cast<char*>(obj_ptr);
53 return reinterpret_cast<int*>(ptr + length_offset_in_bytes());
54 }
55
56 // Given a type, return true if elements of that type must be aligned to 64-bit.
57 static bool element_type_should_be_aligned(BasicType type) {
58 #ifdef _LP64
59 if (type == T_OBJECT || type == T_ARRAY) {
60 return !UseCompressedOops;
61 }
62 #endif
63 return type == T_DOUBLE || type == T_LONG;
64 }
65
66 public:
67 // Header size computation.
68 // The header is considered the oop part of this type plus the length.
69 // This is not equivalent to sizeof(arrayOopDesc) which should not appear in the code.
70 static int header_size_in_bytes() {
71 int hs = length_offset_in_bytes() + (int)sizeof(int);
72 #ifdef ASSERT
73 // make sure it isn't called before UseCompressedOops is initialized.
74 static int arrayoopdesc_hs = 0;
75 if (arrayoopdesc_hs == 0) arrayoopdesc_hs = hs;
76 assert(arrayoopdesc_hs == hs, "header size can't change");
77 #endif // ASSERT
78 return (int)hs;
79 }
80
81 // The _length field is not declared in C++. It is allocated after the
82 // mark-word when using compact headers (+UseCompactObjectHeaders), otherwise
83 // after the compressed Klass*.
84 static int length_offset_in_bytes() {
85 return oopDesc::base_offset_in_bytes();
86 }
87
88 // Returns the offset of the first element.
89 static int base_offset_in_bytes(BasicType type) {
90 int hs = header_size_in_bytes();
91 return element_type_should_be_aligned(type) ? align_up(hs, BytesPerLong) : hs;
92 }
93
94 // Returns the address of the first element. The elements in the array will not
95 // relocate from this address until a subsequent thread transition.
96 void* base(BasicType type) const {
114
115 // Accessors for array length. There's not a member variable for
116 // it; see length_offset_in_bytes().
117 int length() const { return *length_addr_impl(const_cast<arrayOopDesc*>(this)); }
118 void set_length(int length) { *length_addr_impl(this) = length; }
119
120 int* length_addr() {
121 return length_addr_impl(this);
122 }
123
124 static void set_length(HeapWord* mem, int length) {
125 *length_addr_impl(mem) = length;
126 }
127
128 // Return the maximum length of an array of BasicType. The length can be passed
129 // to typeArrayOop::object_size(scale, length, header_size) without causing an
130 // overflow. We also need to make sure that this will not overflow a size_t on
131 // 32 bit platforms when we convert it to a byte size.
132 static int32_t max_array_length(BasicType type) {
133 assert(type < T_CONFLICT, "wrong type");
134 assert(type2aelembytes(type) != 0, "wrong type");
135
136 int hdr_size_in_bytes = base_offset_in_bytes(type);
137 // This is rounded-up and may overlap with the first array elements.
138 int hdr_size_in_words = align_up(hdr_size_in_bytes, HeapWordSize) / HeapWordSize;
139
140 const size_t max_element_words_per_size_t =
141 align_down((SIZE_MAX/HeapWordSize - (size_t)hdr_size_in_words), MinObjAlignment);
142 const size_t max_elements_per_size_t =
143 HeapWordSize * max_element_words_per_size_t / (size_t)type2aelembytes(type);
144 if ((size_t)max_jint < max_elements_per_size_t) {
145 // It should be ok to return max_jint here, but parts of the code
146 // (CollectedHeap, Klass::oop_oop_iterate(), and more) uses an int for
147 // passing around the size (in words) of an object. So, we need to avoid
148 // overflowing an int when we add the header. See CRs 4718400 and 7110613.
149 return align_down(max_jint - hdr_size_in_words, MinObjAlignment);
150 }
151 return (int32_t)max_elements_per_size_t;
152 }
153
154 };
155
156 #endif // SHARE_OOPS_ARRAYOOP_HPP
|
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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_ARRAYOOP_HPP
26 #define SHARE_OOPS_ARRAYOOP_HPP
27
28 #include "oops/oop.hpp"
29 #include "runtime/globals.hpp"
30 #include "utilities/align.hpp"
31 #include "utilities/globalDefinitions.hpp"
32
33 // arrayOopDesc is the abstract baseclass for all arrays. It doesn't
34 // declare pure virtual to enforce this because that would allocate a vtbl
35 // in each instance, which we don't want.
36
37 // The layout of array Oops is:
38 //
39 // markWord
40 // Klass* // 32 bits if compressed but declared 64 in LP64.
41 // length // shares klass memory or allocated after declared fields.
42
43
44 class arrayOopDesc : public oopDesc {
45 friend class VMStructs;
46 friend class arrayOopDescTest;
47
48 // Interpreter/Compiler offsets
49
50 private:
51 // Returns the address of the length "field". See length_offset_in_bytes().
52 static int* length_addr_impl(void* obj_ptr) {
53 char* ptr = static_cast<char*>(obj_ptr);
54 return reinterpret_cast<int*>(ptr + length_offset_in_bytes());
55 }
56
57 // Given a type, return true if elements of that type must be aligned to 64-bit.
58 static bool element_type_should_be_aligned(BasicType type) {
59 if (type == T_FLAT_ELEMENT) {
60 return true; //CMH: tighten the alignment when removing T_FLAT_ELEMENT
61 }
62 #ifdef _LP64
63 if (type == T_OBJECT || type == T_ARRAY) {
64 return !UseCompressedOops;
65 }
66 #endif
67 return type == T_DOUBLE || type == T_LONG;
68 }
69
70 public:
71 // Header size computation.
72 // The header is considered the oop part of this type plus the length.
73 // This is not equivalent to sizeof(arrayOopDesc) which should not appear in the code.
74 static int header_size_in_bytes() {
75 int hs = length_offset_in_bytes() + (int)sizeof(int);
76 #ifdef ASSERT
77 // make sure it isn't called before UseCompressedOops is initialized.
78 static int arrayoopdesc_hs = 0;
79 if (arrayoopdesc_hs == 0) arrayoopdesc_hs = hs;
80 // assert(arrayoopdesc_hs == hs, "header size can't change");
81 #endif // ASSERT
82 return (int)hs;
83 }
84
85 // The _length field is not declared in C++. It is allocated after the
86 // mark-word when using compact headers (+UseCompactObjectHeaders), otherwise
87 // after the compressed Klass*.
88 static int length_offset_in_bytes() {
89 return oopDesc::base_offset_in_bytes();
90 }
91
92 // Returns the offset of the first element.
93 static int base_offset_in_bytes(BasicType type) {
94 int hs = header_size_in_bytes();
95 return element_type_should_be_aligned(type) ? align_up(hs, BytesPerLong) : hs;
96 }
97
98 // Returns the address of the first element. The elements in the array will not
99 // relocate from this address until a subsequent thread transition.
100 void* base(BasicType type) const {
118
119 // Accessors for array length. There's not a member variable for
120 // it; see length_offset_in_bytes().
121 int length() const { return *length_addr_impl(const_cast<arrayOopDesc*>(this)); }
122 void set_length(int length) { *length_addr_impl(this) = length; }
123
124 int* length_addr() {
125 return length_addr_impl(this);
126 }
127
128 static void set_length(HeapWord* mem, int length) {
129 *length_addr_impl(mem) = length;
130 }
131
132 // Return the maximum length of an array of BasicType. The length can be passed
133 // to typeArrayOop::object_size(scale, length, header_size) without causing an
134 // overflow. We also need to make sure that this will not overflow a size_t on
135 // 32 bit platforms when we convert it to a byte size.
136 static int32_t max_array_length(BasicType type) {
137 assert(type < T_CONFLICT, "wrong type");
138 assert(type != T_FLAT_ELEMENT, "wrong type");
139 assert(type2aelembytes(type) != 0, "wrong type");
140
141 int hdr_size_in_bytes = base_offset_in_bytes(type);
142 // This is rounded-up and may overlap with the first array elements.
143 int hdr_size_in_words = align_up(hdr_size_in_bytes, HeapWordSize) / HeapWordSize;
144
145 const size_t max_element_words_per_size_t =
146 align_down((SIZE_MAX/HeapWordSize - (size_t)hdr_size_in_words), MinObjAlignment);
147 const size_t max_elements_per_size_t =
148 HeapWordSize * max_element_words_per_size_t / (size_t)type2aelembytes(type);
149 if ((size_t)max_jint < max_elements_per_size_t) {
150 // It should be ok to return max_jint here, but parts of the code
151 // (CollectedHeap, Klass::oop_oop_iterate(), and more) uses an int for
152 // passing around the size (in words) of an object. So, we need to avoid
153 // overflowing an int when we add the header. See CRs 4718400 and 7110613.
154 return align_down(max_jint - hdr_size_in_words, MinObjAlignment);
155 }
156 return (int32_t)max_elements_per_size_t;
157 }
158
159 inline bool is_null_free_array() const;
160 };
161
162 #endif // SHARE_OOPS_ARRAYOOP_HPP
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