1 /*
2 * Copyright (c) 1998, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
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_VM_CODE_OOPRECORDER_HPP
26 #define SHARE_VM_CODE_OOPRECORDER_HPP
27
28 #include "runtime/handles.hpp"
29 #include "utilities/growableArray.hpp"
30
31 // Recording and retrieval of oop relocations in compiled code.
32
33 class CodeBlob;
34
35 class OopRecorder : public ResourceObj {
36 public:
37 // A two-way mapping from positive indexes to oop handles.
38 // The zero index is reserved for a constant (sharable) null.
39 // Indexes may not be negative.
40
41 // Use the given arena to manage storage, if not NULL.
42 // By default, uses the current ResourceArea.
43 OopRecorder(Arena* arena = NULL);
44
45 // Generate a new index on which CodeBlob::oop_addr_at will work.
46 // allocate_index and find_index never return the same index,
47 // and allocate_index never returns the same index twice.
48 // In fact, two successive calls to allocate_index return successive ints.
49 int allocate_index(jobject h) {
50 return add_handle(h, false);
51 }
52
53 // For a given jobject, this will return the same index repeatedly.
54 // The index can later be given to oop_at to retrieve the oop.
55 // However, the oop must not be changed via CodeBlob::oop_addr_at.
56 int find_index(jobject h) {
57 int index = maybe_find_index(h);
58 if (index < 0) { // previously unallocated
59 index = add_handle(h, true);
60 }
61 return index;
62 }
63
64 // variant of find_index which does not allocate if not found (yields -1)
65 int maybe_find_index(jobject h);
66
67 // returns the size of the generated oop table, for sizing the CodeBlob.
68 // must be called after all oops are allocated!
69 int oop_size();
70
71 // Retrieve the oop handle at a given index.
72 jobject handle_at(int index);
73
74 int element_count() {
75 // there is always a NULL virtually present as first object
76 return _handles->length() + first_index;
77 }
78
79 // copy the generated oop table to nmethod
80 void copy_to(nmethod* nm); // => nm->copy_oops(_handles)
81
82 bool is_unused() { return _handles == NULL && !_complete; }
83 #ifdef ASSERT
84 bool is_complete() { return _complete; }
85 #endif
86
87 private:
88 // leaky hash table of handle => index, to help detect duplicate insertion
89 class IndexCache: public ResourceObj {
90 // This class is only used by the OopRecorder class.
91 friend class OopRecorder;
92 enum {
93 _log_cache_size = 9,
94 _cache_size = (1<<_log_cache_size),
95 // Index entries are ints. The LSBit is a collision indicator.
96 _collision_bit_shift = 0,
97 _collision_bit = 1,
98 _index_shift = _collision_bit_shift+1
99 };
100 int _cache[_cache_size];
101 static juint cache_index(jobject handle) {
102 juint ci = (int) (intptr_t) handle;
103 ci ^= ci >> (BitsPerByte*2);
104 ci += ci >> (BitsPerByte*1);
105 return ci & (_cache_size-1);
106 }
107 int* cache_location(jobject handle) {
108 return &_cache[ cache_index(handle) ];
109 }
110 static bool cache_location_collision(int* cloc) {
111 return ((*cloc) & _collision_bit) != 0;
112 }
113 static int cache_location_index(int* cloc) {
114 return (*cloc) >> _index_shift;
115 }
116 static void set_cache_location_index(int* cloc, int index) {
117 int cval0 = (*cloc);
118 int cval1 = (index << _index_shift);
119 if (cval0 != 0 && cval1 != cval0) cval1 += _collision_bit;
120 (*cloc) = cval1;
121 }
122 IndexCache();
123 };
124
125 // Helper function; returns false for NULL or Universe::non_oop_word().
126 inline bool is_real_jobject(jobject h);
127
128 void maybe_initialize();
129 int add_handle(jobject h, bool make_findable);
130
131 enum { null_index = 0, first_index = 1, index_cache_threshold = 20 };
132
133 GrowableArray<jobject>* _handles; // ordered list (first is always NULL)
134 GrowableArray<int>* _no_finds; // all unfindable indexes; usually empty
135 IndexCache* _indexes; // map: jobject -> its probable index
136 Arena* _arena;
137 bool _complete;
138
139 #ifdef ASSERT
140 static int _find_index_calls, _hit_indexes, _missed_indexes;
141 #endif
142 };
143
144 #endif // SHARE_VM_CODE_OOPRECORDER_HPP