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comparison src/share/vm/oops/arrayOop.hpp @ 113:ba764ed4b6f2

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6420645: Create a vm that uses compressed oops for up to 32gb heapsizes Summary: Compressed oops in instances, arrays, and headers. Code contributors are coleenp, phh, never, swamyv Reviewed-by: jmasa, kamg, acorn, tbell, kvn, rasbold
author coleenp
date Sun, 13 Apr 2008 17:43:42 -0400
parents d5fc211aea19
children 437d03ea40b1
comparison
equal deleted inserted replaced
110:a49a647afe9a 113:ba764ed4b6f2
20 * CA 95054 USA or visit www.sun.com if you need additional information or 20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions. 21 * have any questions.
22 * 22 *
23 */ 23 */
24 24
25 // arrayOopDesc is the abstract baseclass for all arrays. 25 // arrayOopDesc is the abstract baseclass for all arrays. It doesn't
26 // declare pure virtual to enforce this because that would allocate a vtbl
27 // in each instance, which we don't want.
28
29 // The layout of array Oops is:
30 //
31 // markOop
32 // klassOop // 32 bits if compressed but declared 64 in LP64.
33 // length // shares klass memory or allocated after declared fields.
34
26 35
27 class arrayOopDesc : public oopDesc { 36 class arrayOopDesc : public oopDesc {
28 friend class VMStructs; 37 friend class VMStructs;
29 private: 38
30 int _length; // number of elements in the array 39 // Interpreter/Compiler offsets
40
41 // Header size computation.
42 // The header is considered the oop part of this type plus the length.
43 // Returns the aligned header_size_in_bytes. This is not equivalent to
44 // sizeof(arrayOopDesc) which should not appear in the code, except here.
45 static int header_size_in_bytes() {
46 size_t hs = UseCompressedOops ?
47 sizeof(arrayOopDesc) :
48 align_size_up(sizeof(arrayOopDesc) + sizeof(int), HeapWordSize);
49 #ifdef ASSERT
50 // make sure it isn't called before UseCompressedOops is initialized.
51 static size_t arrayoopdesc_hs = 0;
52 if (arrayoopdesc_hs == 0) arrayoopdesc_hs = hs;
53 assert(arrayoopdesc_hs == hs, "header size can't change");
54 #endif // ASSERT
55 return (int)hs;
56 }
31 57
32 public: 58 public:
33 // Interpreter/Compiler offsets 59 // The _length field is not declared in C++. It is allocated after the
34 static int length_offset_in_bytes() { return offset_of(arrayOopDesc, _length); } 60 // declared nonstatic fields in arrayOopDesc if not compressed, otherwise
35 static int base_offset_in_bytes(BasicType type) { return header_size(type) * HeapWordSize; } 61 // it occupies the second half of the _klass field in oopDesc.
62 static int length_offset_in_bytes() {
63 return UseCompressedOops ? klass_gap_offset_in_bytes() :
64 sizeof(arrayOopDesc);
65 }
66
67 // Returns the offset of the first element.
68 static int base_offset_in_bytes(BasicType type) {
69 return header_size(type) * HeapWordSize;
70 }
36 71
37 // Returns the address of the first element. 72 // Returns the address of the first element.
38 void* base(BasicType type) const { return (void*) (((intptr_t) this) + base_offset_in_bytes(type)); } 73 void* base(BasicType type) const {
74 return (void*) (((intptr_t) this) + base_offset_in_bytes(type));
75 }
39 76
40 // Tells whether index is within bounds. 77 // Tells whether index is within bounds.
41 bool is_within_bounds(int index) const { return 0 <= index && index < length(); } 78 bool is_within_bounds(int index) const { return 0 <= index && index < length(); }
42 79
43 // Accessores for instance variable 80 // Accessors for instance variable which is not a C++ declared nonstatic
44 int length() const { return _length; } 81 // field.
45 void set_length(int length) { _length = length; } 82 int length() const {
83 return *(int*)(((intptr_t)this) + length_offset_in_bytes());
84 }
85 void set_length(int length) {
86 *(int*)(((intptr_t)this) + length_offset_in_bytes()) = length;
87 }
46 88
47 // Header size computation. 89 // Should only be called with constants as argument
48 // Should only be called with constants as argument (will not constant fold otherwise) 90 // (will not constant fold otherwise)
91 // Returns the header size in words aligned to the requirements of the
92 // array object type.
49 static int header_size(BasicType type) { 93 static int header_size(BasicType type) {
50 return Universe::element_type_should_be_aligned(type) 94 size_t typesize_in_bytes = header_size_in_bytes();
51 ? align_object_size(sizeof(arrayOopDesc)/HeapWordSize) 95 return (int)(Universe::element_type_should_be_aligned(type)
52 : sizeof(arrayOopDesc)/HeapWordSize; 96 ? align_object_size(typesize_in_bytes/HeapWordSize)
97 : typesize_in_bytes/HeapWordSize);
53 } 98 }
54 99
55 // This method returns the maximum length that can passed into 100 // This method returns the maximum length that can passed into
56 // typeArrayOop::object_size(scale, length, header_size) without causing an 101 // typeArrayOop::object_size(scale, length, header_size) without causing an
57 // overflow. We substract an extra 2*wordSize to guard against double word 102 // overflow. We substract an extra 2*wordSize to guard against double word
60 assert(type >= 0 && type < T_CONFLICT, "wrong type"); 105 assert(type >= 0 && type < T_CONFLICT, "wrong type");
61 assert(type2aelembytes(type) != 0, "wrong type"); 106 assert(type2aelembytes(type) != 0, "wrong type");
62 // We use max_jint, since object_size is internally represented by an 'int' 107 // We use max_jint, since object_size is internally represented by an 'int'
63 // This gives us an upper bound of max_jint words for the size of the oop. 108 // This gives us an upper bound of max_jint words for the size of the oop.
64 int32_t max_words = (max_jint - header_size(type) - 2); 109 int32_t max_words = (max_jint - header_size(type) - 2);
65 int elembytes = (type == T_OBJECT) ? T_OBJECT_aelem_bytes : type2aelembytes(type); 110 int elembytes = type2aelembytes(type);
66 jlong len = ((jlong)max_words * HeapWordSize) / elembytes; 111 jlong len = ((jlong)max_words * HeapWordSize) / elembytes;
67 return (len > max_jint) ? max_jint : (int32_t)len; 112 return (len > max_jint) ? max_jint : (int32_t)len;
68 } 113 }
69 114
70 }; 115 };