Mercurial > hg > truffle
comparison src/share/vm/oops/arrayOop.hpp @ 113:ba764ed4b6f2
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 |
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date | Sun, 13 Apr 2008 17:43:42 -0400 |
parents | d5fc211aea19 |
children | 437d03ea40b1 |
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110:a49a647afe9a | 113:ba764ed4b6f2 |
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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 }; |